Treating barrier and transmission element contamination from a hybrid particulate matter sensor
阅读说明：本技术 处理自混合颗粒物传感器的障碍物和传输元件污染物 (Treating barrier and transmission element contamination from a hybrid particulate matter sensor ) 是由 M·姆特鲁 闫淼磊 于 2020-04-03 设计创作，主要内容包括：本公开涉及处理自混合颗粒物传感器的障碍物和传输元件污染物。提供了一种便携式电子设备,其可以以颗粒物浓度模式操作,其中该便携式电子设备使用自混合干涉测量传感器从光学谐振腔发射相干光的光束,接收进入所述光学谐振腔的所述光束的反射或反向散射,产生由相干光的所述光束的反射或反向散射产生的自混合信号,以及使用所述自混合信号确定粒子速度和/或颗粒物浓度。该便携式电子设备还可以绝对距离模式操作,其中该便携式电子设备确定使用自混合信号确定的绝对距离是在与相干光的所述光束相关联的颗粒感测体积之外还是之内。如果不是,则该便携式电子设备可确定存在污染物和/或障碍物,这可能导致不准确的粒子速度和/或颗粒物浓度确定。(The present disclosure relates to treating obstructions and transmission element contaminants of self-mixing particulate matter sensors. A portable electronic device is provided that can operate in a particulate matter concentration mode, wherein the portable electronic device emits a beam of coherent light from an optical resonant cavity using a self-mixing interferometric sensor, receives a reflection or backscatter of the beam of coherent light into the optical resonant cavity, generates a self-mixing signal generated by the reflection or backscatter of the beam of coherent light, and determines particle velocity and/or particulate matter concentration using the self-mixing signal. The portable electronic device may also operate in an absolute distance mode, wherein the portable electronic device determines whether an absolute distance determined using the self-mixing signal is outside or within a particle sensing volume associated with the beam of coherent light. If not, the portable electronic device may determine that a contaminant and/or obstruction is present, which may result in an inaccurate particle velocity and/or particulate matter concentration determination.)
1. A portable electronic device that senses particulate matter, comprising:
at least one optically transparent material;
at least one optical element;
a self-mixing interferometric sensor configured to emit a beam of coherent light from an optical resonant cavity through the at least one optically transparent material via the at least one optical element to illuminate an object, to receive a reflection or backscatter of the beam of light entering the optical resonant cavity, and to generate a self-mixing signal resulting from self-mixing of the coherent light within the optical resonant cavity; and
a processor configured to:
determining a particle velocity using the self-mixing signal;
determining a particulate matter concentration using the particle velocity and particle count;
determining an absolute distance to the object using the self-mixing signal; and
determining whether the particulate matter concentration is accurate by determining whether the absolute distance corresponds to outside of a sensing volume associated with the beam of coherent light.
2. The portable electronic device of claim 1, wherein the processor determines the particle velocity using:
a first self-mixing signal measured from a first beam of coherent light; and
a second self-mixing signal measured from a second beam of coherent light.
3. The portable electronic device of claim 2, wherein the processor determines the particle velocity using a known angle between the first beam of coherent light and the second beam of coherent light.
4. The portable electronic device of claim 2, wherein:
the self-mixing interferometry sensor comprises a first vertical cavity surface emitting laser and a second vertical cavity surface emitting laser;
said first vertical cavity surface emitting laser emits said first beam of coherent light; and
the second VCSEL emits the second beam of coherent light.
5. The portable electronic device of claim 2, wherein:
the self-mixing interferometric sensor is a single vertical cavity surface emitting laser; and
the at least one optical element splits the beam of coherent light into the first beam of coherent light and the second beam of coherent light.
6. The portable electronic device of claim 1, wherein the at least one optical element focuses the beam of coherent light at a location corresponding to the sensing volume.
7. The portable electronic device of claim 1, wherein the processor discards the particulate matter concentration when it is determined that the particulate matter concentration is inaccurate.
8. A portable electronic device that senses particulate matter, comprising:
a self-mixing interferometric sensor configured to emit a beam of coherent light from an optical resonator, receive a reflection or backscatter of the beam of light entering the optical resonator, and generate a self-mixing signal resulting from self-mixing of the coherent light within the optical resonator; and
a processor configured to:
determining an absolute distance to an object causing the reflection or the backscatter of the beam of coherent light using the self-mixing signal; and
determining a particle velocity using the self-mixing signal when the absolute distance is within a predetermined sensing volume.
9. The portable electronic device of claim 8, wherein the processor waits for a period of time before determining the particle velocity when the absolute distance is outside the predetermined sensing volume.
10. The portable electronic device of claim 8, wherein the processor determines that the particle velocity cannot be determined when the absolute distance is outside the predetermined sensing volume.
11. The portable electronic device of claim 8, wherein the processor:
making a series of absolute distance determinations when the absolute distance is outside the predetermined sensing volume; and
waiting until one of the series of absolute distance determinations is within the predetermined sensing volume, or is not determinable until the particle velocity is determined.
12. The portable electronic device of claim 8, wherein the processor determines the absolute distance based on a modulation of the beam of coherent light.
13. The portable electronic device of claim 8, the processor determines the particle velocity using the self-mixing signal and signals that the particle velocity is inaccurate when the absolute distance is outside the predetermined sensing volume.
14. The portable electronic device defined in claim 8 wherein the self-mixing interferometric sensor comprises at least one vertical cavity surface emitting laser optically coupled to a photodetector.
15. A portable electronic device that senses particulate matter, comprising:
a self-mixing interferometric sensor configured to emit a beam of coherent light from an optical resonator, receive a reflection or backscatter of the beam of light entering the optical resonator, and generate a self-mixing signal resulting from self-mixing of the coherent light within the optical resonator; and
a processor configured to:
operating in a particulate matter concentration determination mode by determining a particle velocity using the self-mixing signal; and
operating in absolute distance mode by:
determining an absolute distance using the self-mixing signal;
determining that a contaminant is present on an optically transparent material when the absolute distance is less than a sensing volume associated with the beam of coherent light; and
determining that an obstruction is present in the beam of coherent light when the absolute distance is greater than the sensing volume.
16. The portable electronic device of claim 15, wherein:
the absolute distance is a first absolute distance; and
the processor determines a second absolute distance after determining the contaminant or the obstruction.
17. The portable electronic device of claim 15, wherein the processor outputs a notification to clean the optically transparent material after determining the presence of the contaminant.
18. The portable electronic device of claim 17, wherein:
the absolute distance is a first absolute distance;
the processor determining a second absolute distance; and
when the second absolute distance is within the sensing volume, the processor switches to the particulate matter concentration determination mode.
19. The portable electronic device of claim 15, wherein the processor outputs a notification to remove the obstacle when the obstacle is determined.
20. The portable electronic device of claim 19, wherein the processor switches to the particulate matter concentration determination mode after removing the obstruction.
Technical Field
Embodiments described in the present disclosure relate generally to sensor technology. More particularly, embodiments of the present invention relate to detecting and handling obstructions and transmission element contaminants from a hybrid particulate matter sensor.
Background
There are many different kinds of electronic devices. Examples of electronic devices include desktop computing devices, laptop computing devices, mobile computing devices, smart phones, tablet computing devices, wearable devices, electronic kitchen appliances, digital media players, and the like. Such electronic devices may include buttons, switches, touch input surfaces, and/or other components.
Electronic devices are increasingly being equipped with one or more environmental and/or other sensors. Examples of such sensors include one or more pressure sensors, temperature sensors, humidity sensors, gas sensors, and particulate matter sensors.
Particulate matter sensing and measurement may be used for environmental and/or other applications, such as air quality monitoring and management. The particulate matter may comprise a mixture of solid particles and/or liquid droplets suspended in air. According to the world health organization data, particulate matter is the world's leading outdoor air pollutant. Particulates can have a variety of adverse health effects, for example, causing respiratory and/or cardiovascular irritation and/or disease, even cancer. Particularly smaller particles, such as PM10 (less than about 10 microns in diameter) and/or PM2.5 (less than about 2.5 microns in diameter), can penetrate deep into the respiratory system and may even be more harmful to humans than larger particles.
Disclosure of Invention
The present disclosure relates to wavelength modulation techniques that detect the presence of contaminants and/or obstacles that may lead to inaccurate particle velocity and/or particulate matter concentration estimates. The portable electronic device may operate in a particulate matter concentration mode, wherein the portable electronic device emits a beam of coherent light from the optical resonator using a self-mixing interferometric sensor, receives a reflection or backscatter of the beam of coherent light into the optical resonator, generates a self-mixing signal generated by the reflection or backscatter of the beam of coherent light, and determines a particle velocity and/or a particulate matter concentration using the self-mixing signal. The portable electronic device may also operate in an absolute distance mode, in which the portable electronic device determines whether an absolute distance determined using the self-mixing signal is outside or within a particle sensing volume associated with the beam of coherent light. If the determined absolute distance is outside the particle sensing volume, the portable electronic device may determine that a contaminant and/or obstruction is present, discard and/or re-determine the associated particle velocity and/or particulate matter concentration determination, indicate removal of the contaminant and/or obstruction, wait to determine the particle velocity and/or particulate matter concentration until the contaminant and/or obstruction disappears, and so forth. Therefore, inaccurate particle velocity and/or particulate matter concentration data cannot be reported and/or used.
In various embodiments, a portable electronic device for sensing particulate matter comprises: at least one optically transparent material; at least one optical element; a self-mixing interferometric sensor configured to emit a beam of coherent light from the optical resonator through the at least one optically transparent material via the at least one optical element to illuminate the object, to receive a reflection or backscatter of the beam of light entering the optical resonator, and to generate a self-mixing signal resulting from self-mixing of the coherent light within the optical resonator; and a processor. The processor is configured to determine a particle velocity using the self-mixing signal, determine a particulate matter concentration using the particle velocity and the particle count, determine an absolute distance to the object using the self-mixing signal, and determine whether the particulate matter concentration is accurate by determining whether the absolute distance corresponds to inside or outside of a sensing volume associated with a beam of coherent light of a relevant particulate matter size range (e.g., PM 2.5).
In some examples, the processor determines the particle velocity using a first self-mixing signal measured from a first beam of coherent light and a second self-mixing signal measured from a second beam of coherent light. In various implementations of such examples, the processor determines the particle velocity using a known angle between the first beam of coherent light and the second beam of coherent light. In many such examples, the self-mixing interferometric sensor includes a first vertical-cavity surface-emitting laser that emits a first beam of coherent light and a second vertical-cavity surface-emitting laser that emits a second beam of coherent light. In some implementations of such examples, the self-mixing interferometric sensor is a single vertical-cavity surface-emitting laser and the at least one optical element splits the beam of coherent light into a first beam of coherent light and a second beam of coherent light.
In various examples, the at least one optical element focuses the beam of coherent light at a location corresponding to the sensing volume. In various examples, the processor discards the particulate matter concentration when it is determined that the particulate matter concentration is inaccurate.
In some embodiments, a portable electronic device that senses particulate matter includes a self-mixing interferometric sensor configured to emit a beam of coherent light from an optical resonator, receive a reflection or backscatter of the beam of light entering the optical resonator, and generate a self-mixing signal resulting from self-mixing of the coherent light within the optical resonator; and a processor. The processor is configured to determine an absolute distance to an object causing reflection or backscatter of the beam of coherent light using the self-mixing signal, and determine a particle velocity using the self-mixing signal when the absolute distance is within a predetermined sensing volume.
In some examples, the portable electronic device may perform absolute distance measurements every second (or other periodic or aperiodic intervals) using a self-mixing interferometric sensor. If the portable electronic device detects that the absolute distance (determined with a sufficiently high signal-to-noise ratio) is outside the predetermined sensing volume, the portable electronic device may discard the data collected during the last second (or other interval).
In various examples, the processor waits for a period of time when the absolute distance is outside the predetermined sensing volume and then determines the particle velocity. In various examples, the processor determines that the particle velocity cannot be determined when the absolute distance is outside of the predetermined sensing volume. In some examples, the processor makes a series of absolute distance determinations when the absolute distance is outside of the predetermined sensing volume, and waits until one of the series of absolute distance determinations is within the predetermined sensing volume, or is not determinable until the particle velocity is determined. In various examples, the processor determines the absolute distance based on a modulation of the beam of coherent light. In some examples, the processor uses the self-mixing signal to determine particle velocity and signals that the particle velocity is inaccurate when the absolute distance is outside of a predetermined sensing volume. In various examples, the self-mixing interferometric sensor is at least one vertical cavity surface emitting laser optically coupled to a photodetector.
In various embodiments, a portable electronic device that senses particulate matter includes a self-mixing interferometric sensor configured to emit a beam of coherent light from an optical resonator, receive a reflection or backscatter of the beam of light entering the optical resonator, and generate a self-mixing signal resulting from self-mixing of the coherent light within the optical resonator; and a processor. The processor is configured to operate in a particulate matter concentration determination mode by determining a particle velocity using the self-mixing signal, and to operate in an absolute distance mode by determining an absolute distance using the self-mixing signal; determining that a contaminant is present on the optically transparent material when the absolute distance is less than a sensing volume associated with a beam of coherent light of a relevant particulate matter size range (e.g., PM 2.5); and determining that an obstruction is present in the beam of coherent light when the absolute distance is greater than the associated sensing volume.
In some examples, the absolute distance is a first absolute distance and the processor determines the second absolute distance after determining the contaminant or obstruction. In various examples, the processor outputs a notification to clean the optically transparent material after determining that the contaminant is present. In some implementations of such examples, the absolute distance is a first absolute distance, the processor determines a second absolute distance, and the processor switches to the particulate matter concentration determination mode when the second absolute distance is within the sensing volume (if particles are present at the time of measurement) or the measurement of the second absolute distance is no longer indicative of the presence of contaminants or obstructions (if particles are not present at the time of measurement).
For example, the processor may measure absolute distance every second (or other periodic or aperiodic interval). The contamination or obstruction may be slow (in milliseconds to seconds). Thus, the processor is likely to measure the absolute distance of the contaminant or obstruction (if present). When the measurement of the absolute distance indicates that the absolute distance is not within the sensing volume, the processor may discard the data recorded in that second (or other interval).
In various examples, the processor outputs a notification to remove the obstacle when the obstacle is determined. In various examples, the processor switches to the particulate matter concentration determination mode after removing the obstruction.
Drawings
The present disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements.
FIG. 1 depicts an exemplary electronic device that can detect and/or treat one or more obstructions and/or transmission element contaminants of one or more self-mixing particulate sensors.
FIG. 2A depicts a partial cross-section of the example electronic device of FIG. 1, showing an example particulate matter sensor taken along line A-A of FIG. 1.
FIG. 2B depicts the example particulate matter sensor of FIG. 2A with example transmission element contaminants.
FIG. 2C depicts the example particulate matter sensor of FIG. 2A with an example obstruction.
FIG. 3 depicts exemplary functional relationships between exemplary components that may be used to implement the exemplary electronic device of FIG. 1.
FIG. 4 depicts a flow chart of an exemplary method for determining a particulate matter concentration. The exemplary method may be performed by an electronic device, such as the electronic devices shown in fig. 1-3.
FIG. 5A depicts a flow chart showing a first exemplary method for detecting and/or treating one or more obstructions and/or transport element contaminants of one or more self-mixing particulate matter sensors. The exemplary method may be performed by an electronic device, such as the electronic devices shown in fig. 1-3.
FIG. 5B depicts a flow chart showing a second exemplary method for detecting and/or treating one or more obstructions and/or transport element contaminants of the one or more self-mixing particulate matter sensors. The exemplary method may be performed by an electronic device, such as the electronic devices shown in fig. 1-3.
FIG. 5C depicts a flow chart showing a third exemplary method for detecting and/or treating one or more obstructions and/or transport element contaminants of the one or more self-mixing particulate matter sensors. The exemplary method may be performed by an electronic device, such as the electronic devices shown in fig. 1-3.
FIG. 5D depicts a flow chart showing a fourth exemplary method for detecting and/or treating one or more obstructions and/or transport element contaminants of the one or more self-mixing particulate matter sensors. The exemplary method may be performed by an electronic device, such as the electronic devices shown in fig. 1-3.
FIG. 5E depicts a flow chart showing a fifth exemplary method for detecting and/or treating one or more obstructions and/or transport element contaminants of the one or more self-mixing particulate matter sensors. The exemplary method may be performed by an electronic device, such as the electronic devices shown in fig. 1-3.
FIG. 5F depicts a flow chart showing a sixth exemplary method for detecting and/or treating one or more obstructions and/or transport element contaminants of the one or more self-mixing particulate matter sensors. The exemplary method may be performed by an electronic device, such as the electronic devices shown in fig. 1-3.
FIG. 5G depicts a flow chart showing a seventh exemplary method for detecting and/or treating one or more obstructions and/or transport element contaminants of the one or more self-mixing particulate matter sensors. The exemplary method may be performed by an electronic device, such as the electronic devices shown in fig. 1-3.
FIG. 6A depicts a vertical cavity surface emitting laser that may be used for one or more particulate matter sensors in the electronic device of FIGS. 1-3.
FIG. 6B depicts self-mixing interference in the VCSEL of FIG. 6A.
FIG. 7A depicts a parallel self-mixing sensing system for measuring particulate matter concentration and/or particle velocity of particulate matter.
FIG. 7B depicts a first self-mixing signal that may be measured by the parallel self-mixing sensing system of FIG. 7A.
FIG. 7C depicts a second self-mixing signal that may be measured by the parallel self-mixing sensing system of FIG. 7A.
Fig. 8A depicts self-mixing or coherent light feedback in a vertical cavity surface emitting laser that emits coherent light toward a moving object and receives reflected or backscattered light from the moving object.
FIG. 8B depicts a graph of a spectral analysis of interferometric parameters of a VCSEL measured for a moving object.
Fig. 8C depicts a time-dependent plot of signals of laser current, laser wavelength, and interferometric parameters that may be used as part of a spectral analysis.
FIG. 8D depicts a flow diagram showing a spectral analysis method for determining absolute distance.
FIG. 8E depicts a block diagram of a system implementing a spectral analysis method for determining absolute distances.
Detailed Description
Reference will now be made in detail to the exemplary embodiments illustrated in the accompanying drawings. It should be understood that the following description is not intended to limit the embodiments to one preferred embodiment. On the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the embodiments as defined by the appended claims.
The following description includes sample systems, methods, and computer program products that embody various elements of the present disclosure. However, it should be understood that the described disclosure may be embodied in many forms other than those set forth herein.
In self-mixing interferometry, one or more beams of coherent light emitted by one or more stimulated emission sources (such as one or more lasers or other coherent light sources) may be reflected or backscattered from an object and re-coupled into the resonant cavity of the light source emitting the coherent light. This re-coupling may modify one or more interferometric parameters, such as the laser's resonator electric field, measurable phase-sensitive changes in carrier distribution, and/or other changes in gain distribution and lasing threshold, etc., to produce a voltage at the lasing junction (if the laser is driven by a current source), a bias current on the laser (if the laser is driven by a voltage source), and/or a measurable change in the optical power emitted by the laser.
Self-mixing interferometers can be used to measure particulate matter concentration by detecting particles in a gas that scatter coherent light. Using the self-mixing signal measured by detecting a modification of the interferometric parameter caused by the re-coupling of the reflected or backscattered light, the particle may be detected and the velocity of the particle may be determined using the corresponding doppler frequency. The air flow may be determined based on the particle velocity, and the particulate matter concentration may be determined or estimated based on the particle count and the air flow.
Given that the particulate matter may be microscopic, PM10 (less than about 10 microns in diameter) and/or PM2.5 (less than about 2.5 microns in diameter), the amount of light reflected or backscattered from the particulate matter into the cavity may be very small. To detect such reflected or backscattered light, an optical element (such as refractive, diffractive, holographic or sub-wavelength beam shaping optics) may be used to focus the emitted coherent light to a diffraction-limited or near diffraction-limited location that serves as a "sensing volume".
Determining or estimating the particulate matter concentration in this manner may involve an accurate estimate of the particle velocity. Generally, when no air flow control element (such as one or more fans, pumps, etc.) is used, the particles are free to move in three dimensions. Thus, multiple coherent light sources and/or coherent light beams may be used to estimate particle velocity. In such implementations, it may be desirable to know the angles between the various beams accurately to facilitate accurate particle velocity estimation.
Beam shaping optics can often perform satisfactorily and produce a tightly focused beam with a precisely controlled angle. This may facilitate accurate particle velocity estimation and thus estimation of particulate matter concentration. However, the light beam may be transmitted through a transmission element (such as one or more optically transparent materials, e.g., cover glass, plastic layers, etc.) and/or one or more optical elements, e.g., lenses, etc. Contaminants on such optically transparent materials (such as water, sweat, skin oil and/or other oils, fingerprints, dirt, dust, smudges, etc.) can disrupt the tight focus of the light beam due to refraction and scattering. This can result in a significant decrease in the sensitivity of particulate matter detection. In addition, such contamination can change the direction of the light beam, causing inaccuracies in particle velocity estimation. Such contamination can lead to inaccuracies of up to 400% or more.
Furthermore, macroscopic obstacles in the beam path (such as hands, face, walls, table top, etc.) may also lead to inaccurate particle velocity and/or particulate matter concentration estimates. These obstacles may generate self-mixing interferometry signals that may not be distinguished from self-mixing interferometry signals generated by particulate matter. Accordingly, inaccurate particle velocities and/or particulate matter concentrations may be estimated.
The following disclosure relates to wavelength modulation techniques that detect the presence of contaminants and/or obstacles that may lead to inaccurate particle velocity and/or particulate matter concentration estimates. The portable electronic device may operate in a particulate matter concentration mode, wherein the portable electronic device emits a beam of coherent light from the optical resonator using a self-mixing interferometric sensor, receives a reflection or backscatter of the beam of coherent light into the optical resonator, generates a self-mixing signal (or interference signal) resulting from the reflection or backscatter of the beam of coherent light, and determines a particle velocity and/or a particulate matter concentration using the self-mixing signal. The portable electronic device may also operate in an absolute distance mode, in which the portable electronic device determines whether an absolute distance determined using the self-mixing signal is outside or within a particle sensing volume associated with the beam of coherent light. If the determined absolute distance is outside the particle sensing volume, the portable electronic device may determine that a contaminant and/or obstruction is present, discard and/or re-determine the associated particle velocity and/or particulate matter concentration determination, indicate removal of the contaminant and/or obstruction, wait to determine the particle velocity and/or particulate matter concentration until the contaminant and/or obstruction disappears, and so forth. Therefore, inaccurate particle velocity and/or particulate matter concentration data cannot be reported and/or used.
These and other embodiments are discussed below with reference to fig. 1-8E. However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes only and should not be construed as limiting.
FIG. 1 depicts an exemplary
The
FIG. 2A depicts a partial cross-section of the example
Although fig. 2A shows and describes a single VCSEL211 and a single beam of
Regardless, various contaminants on the
The sensing volume can typically be very small, such as about 0.005 cubic millimeters. The presence of a contaminant or obstruction may be determined if the absolute distance to the object resulting from the mixed signal is determined to be outside the sensing volume.
FIG. 2B depicts the example
Regardless, in some cases, the presence of contaminant 230 on
However, the example
For example, if the sensing volume associated with
FIG. 2C depicts the example
In any event, the presence of a non-stationary (i.e., moving) macroscopic obstruction, such as
However, in absolute distance mode, the example
FIG. 3 depicts exemplary functional relationships between exemplary components that may be used to implement the exemplary
FIG. 4 depicts a flow diagram of an
At 410, the electronic device may emit one or more beams of coherent light. For example, the electronic device may use a VCSEL to emit a laser beam through the cover glass. At 420, the electronic device may measure one or more self-mixing signals resulting from reflection or backscatter of one or more beams of coherent light. For example, the electronic device may use a photodetector (such as a photodiode and/or other type of photodetector) to measure changes in the self-mixing parameter in response to the reflection.
At 430, the electronic device can count particles detected using the self-mixing signal. At 440, the electronic device may determine the particle velocity in one or more directions using the self-mixing signal. At 450, the electronics can reconstruct the air flow using the particle velocity. At 460, the electronics can estimate the particulate matter concentration using the particle count and the air flow.
When converting to particulate matter concentration, the electronics can assume a certain particle distribution and a certain mass density. Without these assumptions, it is not possible to achieve a conversion from particle count/volume to particle mass/volume.
The
Although the
For example, the
As another example,
FIG. 5A depicts a flow chart showing a first exemplary method 500A for detecting and/or treating one or more obstructions and/or transport element contaminants of one or more self-mixing particulate matter sensors. This exemplary method 500A may be performed by an electronic device, such as the
At 510A, an electronic device is operable. For example, the electronics can cause one or more coherent light sources to emit one or more beams of coherent light. At 520A, the electronics can determine whether reflection or backscatter from the one or more coherent light sources is detected. For example, the electronic device may use one or more photodetectors (such as one or more photodiodes and/or other types of photodetectors) to detect reflections or backscattering generated by one or more particles and/or other objects in the sensing volume of the one or more light beams and/or otherwise in the path of the one or more light beams. If not, the flow may return to 510A, where the electronic device may continue to operate. Otherwise, the flow may proceed to 530A.
At 530A, the electronic device can determine whether to operate in the particulate matter concentration mode or the absolute distance mode. If the electronics determine to operate in the particulate matter concentration mode, the process may proceed to 540A, where the electronics may determine the particulate matter concentration using reflection or backscatter. The process flow may then return to 530A, where the electronics re-determine whether to operate in the particulate matter concentration mode or the absolute distance mode (such as switching to the absolute distance mode to verify whether the determined particulate matter concentration is accurate).
At 550A, after the electronics determine to operate in absolute distance mode, the electronics can use the reflection or backscatter to determine an absolute distance to the object causing the reflection or backscatter. The use of reflection or backscatter to determine absolute distance will be discussed in more detail below.
The process may then proceed to 560A, where the electronics may determine whether the absolute distance corresponds to one or more sensing volumes associated with one or more coherent light beams. If so, or if the particle has passed through the sensing volume, if the target is not found in the beam path for a predetermined amount of time, the process may proceed to 540A, where the electronics may use reflection or backscatter to determine the particulate matter concentration. Otherwise, the electronic device may determine that an error has occurred (e.g., a combination of a contaminant on the transmission element through which the one or more beams of coherent light are transmitted and an obstacle in one or more paths of the one or more beams of coherent light, etc.), and the process may proceed to 570A, where the electronic device may process the error (e.g., discard data regarding the reflection or backscatter, output a notification regarding the one or more contaminants and/or obstacles, instruct the user to clean the transmission element, instruct the user to remove the obstacle, wait for the obstacle to be removed, etc.).
Although the example method 500A is shown and described as including particular operations performed in a particular order, it should be understood that this is an example. In various implementations, various orders of the same, similar, and/or different operations may be performed without departing from the scope of the disclosure.
For example, the method 500A is shown and described as determining whether to operate in the particulate matter concentration mode or the absolute distance mode after determining the particulate matter concentration. However, in some implementations, the electronic device may instead return to 520A after 540A to first determine whether reflections or backscattering are still detected. Various configurations are possible and contemplated without departing from the scope of the present disclosure.
Further, method 500A is an event-driven method. Alternatively, the electronic device may attempt to measure absolute distances at certain intervals and determine if there is anything that does not correspond to the sensing volume. For example, the electronic device may measure absolute distance every second (or other periodic or aperiodic interval). The contamination or obstruction may be slow (in milliseconds to seconds). Thus, the electronic device is likely to measure the absolute distance of a contaminant or obstruction (if present). When the measurement of the absolute distance indicates that the absolute distance is not within the sensing volume, the electronics can discard the data recorded in that second (or other interval).
FIG. 5B depicts a flow chart showing a second
At 510B, the electronic device may determine a particle velocity using the self-mixing signal. At 520B, the electronic device may determine the accuracy of the self-mixed signal. The self-mixing signal may be accurate when caused by particles moving through the associated sensing volume, and may be inaccurate when caused by contaminants or obstacles other than particles moving through the associated sensing volume. For example, the electronics can determine the accuracy of the self-mixing signal based on a relationship between an absolute distance to an object that causes reflection or backscatter in a beam of coherent light used to generate the self-mixing signal and a sensing volume associated with the beam of coherent light. The flow may then proceed to 530B, where the electronic device may determine whether the self-mixing signal is accurate. For example, if the absolute distance is within the sensing volume, the electronics can determine that the self-mixing signal is accurate. If the absolute distance is outside the sensing volume, the electronics can determine that the self-mixing signal is inaccurate.
If the self-mixing signal is accurate, the process may proceed to 540B, where the electronics may use the particle velocity (such as to determine air flow and/or particulate matter concentration) and the electronics determines another particle velocity before the process returns to 510B. Otherwise, the flow proceeds to 550B, where the electronics can discard the determined particle velocity before returning to 510B and determining another particle velocity.
Although the
For example, the
FIG. 5C depicts a flow chart showing a third exemplary method 500C for detecting and/or treating one or more obstructions and/or transport element contaminants of the one or more self-mixing particulate matter sensors. This exemplary method 500C may be performed by an electronic device, such as the
At 510C, the electronic device may determine a particle velocity using the self-mixing signal. At 520C, the electronic device may determine whether a period of time has elapsed since the electronic device previously determined the accuracy of the mixed signal. For example, the electronic device may determine accuracy only once per second, once per minute, once per hour, once per day, and so forth. If the time period has elapsed, the process may proceed to 530C, where the electronic device may use the particle velocity before the process returns to 510C, and the electronic device determines another particle velocity. Otherwise, the flow may then proceed to 540C, where the electronic device may determine whether the self-mixing signal is accurate. For example, if the absolute distance of an object causing reflection or backscatter in the beam of coherent light used to generate the self-mixing signal is within a particulate matter sensing volume associated with the beam of coherent light, the electronics can determine that the self-mixing signal is accurate.
If the self-mixing signal is accurate, the flow may proceed to 530C, where the electronics may use the particle velocity before the flow returns to 510C, and the electronics determines another particle velocity. Otherwise, the flow proceeds to 550C, where the electronics can discard the determined particle velocity before returning to 510C and determining another particle velocity.
Although the example method 500C is shown and described as including particular operations performed in a particular order, it should be understood that this is an example. In various implementations, various orders of the same, similar, and/or different operations may be performed without departing from the scope of the disclosure.
For example, the method 500C is shown and described as checking for accuracy after a certain period of time has elapsed. However, in other implementations, such accuracy may be determined without monitoring the time period (such as continuously, randomly, etc.). Various configurations are possible and contemplated without departing from the scope of the present disclosure.
FIG. 5D depicts a flow chart showing a fourth exemplary method 500D for detecting and/or treating one or more obstructions and/or transport element contaminants of the one or more self-mixing particulate sensors. This exemplary method 500D may be performed by an electronic device, such as the
At 510D, the electronics can determine the particulate matter concentration using the self-mixing signal. At 520D, the electronic device can determine whether a change between the particulate matter concentration and a previous particulate matter concentration determination is greater than a threshold. For example, the threshold may be a variation of greater than 0.5 micrograms/cubic meter. If the change is less than or equal to the threshold, the flow may proceed to 530D, where the electronic device may use the particle velocity before the flow returns to 510D, and the electronic device determines another particle velocity. Otherwise, the process may then proceed to 540D, where the electronics may determine whether the determined particulate matter concentration is accurate. For example, the electronics can determine that the particulate matter concentration is accurate if the absolute distance of the object causing reflection or backscatter in the beam of coherent light used to determine the particulate matter concentration is within the particle sensing volume associated with the beam of coherent light.
If the particulate matter concentration is accurate, the process may proceed to 530D, where the electronics may use the particulate matter concentration before the process returns to 510D, and the electronics determines another particulate matter concentration. Otherwise, the process proceeds to 550D, where the electronics can discard the determined particulate matter concentration before returning to 510D and determining another particulate matter concentration.
Although the example method 500D is shown and described as including particular operations performed in a particular order, it should be understood that this is an example. In various implementations, various orders of the same, similar, and/or different operations may be performed without departing from the scope of the disclosure.
For example, the method 500D is shown and described as determining another particulate matter concentration after discarding the particulate matter concentration determination due to inaccuracies. However, in some implementations, the electronic device may determine that an accurate particulate matter concentration cannot be determined (e.g., due to contaminants that have not been cleaned and/or obstacles that have not been removed), while the electronic device may instead provide an indication that an accurate particulate matter concentration cannot be determined. Various configurations are possible and contemplated without departing from the scope of the present disclosure.
FIG. 5E depicts a flow chart showing a fifth
At 510E, the electronics can detect a reflection or backscatter of the beam of light from coherent light produced by an object (such as a particle) in the path of the beam of light. The process may then proceed to 520E, where the electronics may determine whether the self-mixing signal generated by reflection or backscatter is accurate. The self-mixing signal may be accurate if the absolute distance to the object determined using the self-mixing signal is within the particle sensing volume associated with the light beam. If so, the flow may proceed to 530E, where the electronics use the self-mixing signal to determine particle velocity before the flow returns to 510E, and the electronics may detect additional reflections or backscattering. Otherwise, flow may proceed directly to 510E.
The particles can move very fast. Their absolute distance may not always be measured. Sometimes, particles may be missed and objects may not be detected when attempting to measure absolute distances. In this case, the fact that the absolute distance measurement does not indicate a target outside the sensing volume may be sufficient to mark the measurement as accurate. Various configurations are possible and contemplated without departing from the scope of the present disclosure.
Although the
For example,
FIG. 5F depicts a flow chart showing a sixth exemplary method 500F for detecting and/or treating one or more obstructions and/or transport element contaminants of the one or more self-mixing particulate matter sensors. The
At 510F, the electronics can determine a particle velocity. The electronics can use the reflection or backscatter of the beam of coherent light from the particles in the path of the beam to determine particle velocity in one or more directions. The flow may then proceed to 520F where the electronics may determine whether the particle velocity is accurate. The particle velocity may be accurate if the absolute distance to the particle determined using reflection or backscatter is within the particle sensing volume associated with the light beam. If so, the flow may proceed to 530F, where the electronic device uses the determined particle velocity before the flow returns to 510F, and the electronic device may determine another particle velocity. Otherwise, flow may proceed to 540F where the electronics may wait (e.g., for a period of time, such as 10 milliseconds, 2 seconds, etc.), then return to 510F and attempt to determine the particle velocity again.
Although the example method 500F is shown and described as including particular operations performed in a particular order, it should be understood that this is an example. In various implementations, various orders of the same, similar, and/or different operations may be performed without departing from the scope of the disclosure.
For example, the method 500F is shown and described as determining a particle velocity at 510F. However, in some implementations, the electronic device may instead determine whether a particle is detected. If not, the process may wait until a particle is detected and determine the velocity of the particle in one or more directions before proceeding to 520F. Various configurations are possible and contemplated without departing from the scope of the present disclosure.
FIG. 5G depicts a flow chart showing a seventh
At 510G, the electronics can determine a particle velocity. The electronics can use the reflection or backscatter of the beam of coherent light from the particles in the path of the beam to determine particle velocity in one or more directions. The process may then proceed to 520G, where the electronics may determine an absolute distance to the particle and/or another object causing reflection or backscatter. The flow may then proceed to 530G, where the electronics may determine whether the absolute distance is less than, equal to, or greater than the sensing volume associated with the light beam.
If the absolute distance is less than the sensing volume, the electronic device may determine that an object other than a particle is blocking the light beam, and the flow may proceed to 550G, where the electronic device may output an object removal notification. The flow may then return to 510G where the electronics determine another particle velocity.
If the absolute distance is greater than the sensing volume, the electronic device can determine that a contaminant is present on the cover glass or other transmission element, and the process can proceed to 560G, where the electronic device can output a cover glass cleaning notification. The flow may then return to 510G where the electronics determine another particle velocity.
If the absolute distance is equal to the sensing volume, the electronics can determine that the particle velocity is accurate. The process may then proceed to 540G, where the electronics may use the particle velocity to determine the particulate matter concentration.
In some cases, the electronic device may not be able to measure any absolute distance. However, if the electronics are unable to measure absolute distance, the electronics can determine that the determined particle velocity is accurate. Various configurations are possible and contemplated without departing from the scope of the present disclosure.
Although the
For example,
The use of the self-mixing signal to determine or estimate particle velocity, air flow, and/or particulate matter concentration will now be described in more detail. FIG. 6A depicts an exemplary block diagram of a VCSEL211 that may be used for one or more particle sensors in the electronic device of FIGS. 1-3. In a typical type of laser, an input energy source causes the gain material within the cavity to emit light. Mirrors at both ends of the cavity feed the light back to the gain material to cause amplification of the light and to make the light coherent, and have (mostly) a single wavelength. An aperture in one of the mirrors allows transmission of coherent light.
In the VCSEL211, there may be two
Fig. 6B depicts self-mixing interference (alternatively referred to as "optical feedback" or "back injection") in the VCSEL211 of fig. 6A. In fig. 6B,
The emitted
Fig. 7A-7C are diagrams illustrating a parallel self-mixing sensing system 700A for measuring particle velocity components and corresponding self-mixing signals. The parallel self-mixing sensing system 700A includes a self-mixing module 701. The self-mixing module 701 includes a first light source and detector unit 702, a first optical element (e.g., lens) 706, a second light source and detector unit 704, and a second optical element (e.g., lens) 708. The first light source and detector unit 702 may be a monolithically integrated unit comprising the first light source and the first photodetector. In some implementations, the first light source is a laser source such as a first VCSEL, and the first photodetector is an intra-or extra-cavity photodiode monolithically integrated with the first VCSEL. Similarly, the second light source and detector unit 704 may be a monolithically integrated unit comprising a second light source such as a second VCSEL and a second photodetector (e.g., photodiode) that is similarly integrated with the second VCSEL.
The first VCSEL generates a first light beam 710 and the second VCSEL generates a second light beam 712. The center point, which is defined as the point with the highest irradiance on the transverse plane where the laser beam has the smallest footprint, i.e., the focal point of the first beam 710, is a distance Delta _ x from the center point of the second beam 712. When two VCSELs are used, the value of the distance Delta _ x may be in the range of about 15 μm to 100 μm. However, in a Laguerre-Gaussian beam implementation using a single VCSEL, Delta _ x may range from about 0.25 μm to 2.5 μm. The focal region 720 includes the focal points of the first light beam 710 and the second light beam 712. The particle 705 moving in the focal region 720 may be characterized by the parallel self-mixing sensing system 700A. For example, when the particle 705 passes through one of the first beam 710 or the second beam 712, the absolute value of the corresponding velocity in the Z direction (| Vz |) may be measured from the doppler shift using self-mixing interferometry techniques. For example, when particle 705 passes near the focal point of first beam 710, it may scatter a portion of first beam 710, which may reach and be re-coupled with the resonant cavity of the first VCSEL. Under such coherent interaction, the first photodetector may detect the first self-mixing signal and measure a first timing associated with the first signal.
As the particle 705 moves in the focal region 720, it may pass near the focal point of the second beam 712 and may scatter a portion of the second beam 712, which may reach and be recoupled to the resonant cavity of the second VCSEL. Under such coherent interaction, the second photodetector may detect the second self-mixing signal and measure a second timing associated with the second signal. The time difference Delta _ T between the first timing (T0) and the second timing (T1) may be used (e.g., by a processor) to determine the horizontal velocity component (Vx) of the particle 705 (Vx Delta _ X/Delta _ T) by simply dividing the distance the particle 705 travels in the X direction (Delta _ X) by the time difference Delta _ T. The processor may be, for example, a processor of a host device such as a smartphone or a smart watch.
In one or more implementations, the first and second photodetectors may be separate from the first and second VCSELs and positioned at a side of the VCSELs, e.g., implemented as side photodetectors on a chip. In these implementations, cover glass on a separate beam splitting element with a splitting ratio may be used to reflect the first beam 710 and the second beam 712 to a side photodetector, the primary purpose of which is to monitor the optical power level of the reflected light. The power level of the light reflected from the cover glass and/or the separate beam splitting element is a measure of the light output power level of the first VCSEL and the second VCSEL. The self-mixing interference caused by the particles 705 disturbs the output power of the VCSEL and thus produces a measurable signal on the corresponding photodetector.
In some implementations, the first beam and the second beam can be implemented based on a single laser source (e.g., a first VCSEL). In some such implementations, a single beam of a single laser source may be converted to a higher order laguerre-gaussian beam with two independent lobes 725. As described above, each of the lobes 725 may serve as one of the first beam 710 and the second beam 712, and may similarly be used to characterize the particle 705. In this implementation, the self-mixing signal may be read from a single photodetector.
In one or more implementations, the light source and detector units 702 and/or 704 may be monolithic VCSEL photodetector units and include a top distributed bragg reflector, a multiple quantum well active region, and a bottom distributed bragg reflector. The bottom distributed bragg reflector may include an intra-cavity photodetector layer.
A graph 700B shown in fig. 7B represents a first exemplary signal recorded by the first photodetector of the first light source and detector unit 702. The recorded first exemplary signal includes a background (e.g., noise) 730 and a first self-mixed signal 740. The first timing T0 is the start time of the first self-mixed signal 740. Alternatively, T0 may be defined as the peak point of the envelope of the first self-mixed signal 740.
A
Although fig. 7A to 7C show the use of first and second light sources and detector units 702, 704 to detect velocity in the X-plane, it should be understood that this is an example. In various implementations, one or more additional pairs of light source and detector units (and/or a single light source and detector using split beams and/or other multiple light beams) may be positioned perpendicular to the first and second light sources and detector units 702, 704 in the Y-plane and/or Z-plane to detect velocity in the Y-plane and/or Z-plane, respectively. Various configurations for measuring and determining and/or estimating particle velocity are possible and contemplated without departing from the scope of the present disclosure.
Determining or estimating absolute distances using self-mixing signals will now be described in more detail. As previously discussed, fig. 6B shows a diagram of a laser component capable of self-mixing interference that can produce interferometric parameter variations. As previously discussed, there may be two
In the example shown, there is a velocity (magnitude) with respect to the laser
Using the specific example of power, and reviewing from the above, in the absence of strong back reflection (e.g., no specular reflector), the change in power is related to the length of the
Because the movement of the target causes the optical feedback cavity length to vary through multiple wavelengths of the emitted coherent light, the sinusoidal power signal (or an equivalent sinusoidal signal of another interferometric parameter) can be spectrally analyzed, such as through a Fast Fourier Transform (FFT). The bottom graph 830 of fig. 8A shows an amplitude (or "magnitude") curve from such spectral analysis. The spectrum may be calculated from samples taken during a sampling interval comprised between time 0 and time 826a during which the target is moved in a single direction relative to the laser.
In some implementations, the spectral analysis may use a sample size of 128 or 256 samples. Spectral analysis may also apply a filter (such as a triangular filter, raised cosine filter, etc.) to a sample of the signal of the interferometric parameter being measured (such as a power supply or a change therein, or junction voltage or current, or laser bias current, etc.).
FIG. 8A showsA graph 830 of the magnitude or amplitude spectrum in which there are three significant components is shown. There is a DC component 832 which reflects the fact that the signal of the interferometric parameter generally has a steady-state value around which the signal oscillates sinusoidally. Then, there is a main or main frequency f of the sinusoidal signal with the interferometric parameterBAn associated first harmonic or fundamental beat frequency 834. It can be seen that in some configurations fB＝c×(Delta_λ/λ2) Wherein DeltaλIs the Doppler shift of the wavelength due to the movement of the object and is caused by
TABLE 1
Fig. 8B shows a first combined magnitude and phase plot 840 obtained from spectral analysis of the junction voltage signal in one embodiment. The top of the combined magnitude and phase graph 840 shows the magnitude of the FFT, while the bottom of the graph 840 shows the phase. In graph 840, the target moves in a first direction relative to the laser. The movement of the target produces a primarily, but non-ideal sinusoidal form such that there is more than one harmonic, as shown by the amplitude curve at the top of the combined magnitude and phase plot 840. Fig. 8B also shows a second combined magnitude and phase plot 850 obtained under the same conditions, except that the target is moving in the opposite direction (at the same speed).
The phase shift at the second harmonic frequency can be used to determine the direction of motion. The particular example shown in the phase curve of graph 840 is from a spectral analysis performed on a voltage signal induced by the target moving in a first direction relative to the laser. This direction is calculated by: 2 x phase fundamental harmonic phase second harmonic.
When the value is greater than zero, the target moves toward the laser, and when the value is less than zero, the target moves away from the laser. Next, the particular example shown in the phase curve of graph 850 is from an exemplary spectral analysis performed on the voltage signal induced by the target moving in a direction opposite the first direction relative to the laser. In this case, the number of calculations will be less than zero.
Fig. 8C shows a time-dependent graph 860 relating laser current 862 (also referred to as modulation current) with a resulting laser wavelength 864 and a resulting
Fig. 8D and 8E illustrate a flow diagram of a
At an
Applying a modulation current 862 to the VCSEL induces a
At
At
At
Fig. 8E illustrates a block diagram of a
As described above, movement of the target may cause a change in an interferometric parameter, such as a parameter of the
The
The voltage output may then be sampled and quantized by an analog-to-digital conversion (ADC) block 895 c. It may be helpful to apply equalization immediately before applying the digital FFT to the output of the ADC block 895 c. The initial digital signal value from the digital generator used to generate the modulation current 862 is used as an input to the digital
The output of the digital
Equalization and subtraction can be used to clear any remaining artifacts that may be present in the
Once the best correlation is obtained by feedback, the FFT shown in
The
In various implementations, a portable electronic device that senses particulate matter may include: at least one optically transparent material; at least one optical element; a self-mixing interferometric sensor configured to emit a beam of coherent light from the optical resonator through the at least one optically transparent material via the at least one optical element to illuminate the object, to receive a reflection or backscatter of the beam of light entering the optical resonator, and to generate a self-mixing signal resulting from self-mixing of the coherent light within the optical resonator; and a processor. The processor may be configured to determine a particle velocity using the self-mixing signal, determine a particulate matter concentration using the particle velocity and the particle count, determine an absolute distance to the object using the self-mixing signal, and determine whether the particulate matter concentration is accurate by determining whether the absolute distance corresponds to inside or outside of a particulate matter sensing volume associated with the beam of coherent light.
In some examples, the processor may determine the particle velocity using a first self-mixing signal measured from a first beam of coherent light and a second self-mixing signal measured from a second beam of coherent light. In various such examples, the processor may determine the particle velocity using a known angle between the first beam of coherent light and the second beam of coherent light. In many such examples, the self-mixing interferometric sensor can include a first vertical-cavity surface-emitting laser that can emit a first beam of coherent light and a second vertical-cavity surface-emitting laser that can emit a second beam of coherent light. In some such examples, the self-mixing interferometric sensor may be a single vertical-cavity surface-emitting laser, and the at least one optical element may separate the beam of coherent light into a first beam of coherent light and a second beam of coherent light.
In various examples, the at least one optical element may focus the beam of coherent light at a location corresponding to the sensing volume. In various examples, the processor may discard the particulate matter concentration when it is determined that the particulate matter concentration is inaccurate.
In some implementations, a portable electronic device that senses particulate matter can include a self-mixing interferometric sensor configured to emit a beam of coherent light from an optical resonator, receive a reflection or backscatter of the beam of light entering the optical resonator, and generate a self-mixing signal resulting from self-mixing of the coherent light within the optical resonator; and a processor. The processor may be configured to determine an absolute distance to an object causing reflection or backscatter of the beam of coherent light using the self-mixing signal, and determine a particle velocity using the self-mixing signal when the absolute distance is within a predetermined sensing volume.
In various examples, the processor may wait for a period of time when the absolute distance is outside the predetermined sensing volume and then determine the particle velocity. In various examples, the processor may determine that the particle velocity cannot be determined when the absolute distance is outside of a predetermined sensing volume. In some examples, the processor may make a series of absolute distance determinations when the absolute distance is outside of the predetermined sensing volume, and wait until one of the series of absolute distance determinations is within the predetermined sensing volume, or is not determinable until the particle velocity is determined. In various examples, the processor may determine the absolute distance based on a modulation of the beam of coherent light. In some examples, the processor may use the self-mixing signal to determine the particle velocity and signal that the particle velocity is inaccurate when the absolute distance is outside of a predetermined sensing volume. In various examples, the self-mixing interferometric sensor can be at least one vertical cavity surface emitting laser optically coupled to a photodetector.
In various implementations, a portable electronic device that senses particulate matter may include a self-mixing interferometric sensor configured to emit a beam of coherent light from an optical resonator, receive a reflection or backscatter of the beam of light entering the optical resonator, and generate a self-mixing signal resulting from self-mixing of the coherent light within the optical resonator; and a processor. The processor may be configured to operate in a particulate matter concentration determination mode by determining a particle velocity using the self-mixing signal, and operate in an absolute distance mode by determining an absolute distance using the self-mixing signal; determining that a contaminant is present on the optically transparent material when the absolute distance is less than a sensing volume associated with the beam of coherent light; and determining that an obstruction is present in the beam of coherent light when the absolute distance is greater than the sensing volume.
In some examples, the absolute distance may be a first absolute distance, and the processor may determine the second absolute distance after determining the contaminant or obstruction. In various examples, the processor may output a notification to clean the optically transparent material after determining that the contaminant is present. In some such examples, the absolute distance may be a first absolute distance, the processor may determine a second absolute distance, and the processor may switch to the particulate matter concentration determination mode when the second absolute distance is within the sensing volume.
In various examples, the processor may output a notification to remove the obstacle when the obstacle is determined. In various examples, the processor may switch to the particulate matter concentration determination mode after removing the obstruction.
As described above and shown in the figures, the present disclosure relates to wavelength modulation techniques that detect the presence of contaminants and/or obstacles that may lead to inaccurate particle velocity and/or particulate matter concentration estimates. The portable electronic device may operate in a particulate matter concentration mode, wherein the portable electronic device emits at least one beam of coherent light using at least one light source, measures a self-mixing signal generated by reflection or backscatter of the beam of coherent light using at least one detector, and determines particle velocity and/or particulate matter concentration using the self-mixing signal. The portable electronic device may also operate in an absolute distance mode, in which the portable electronic device determines whether an absolute distance determined using the self-mixing signal is outside or within a particle sensing volume associated with the beam of coherent light. If the determined absolute distance is outside the particle sensing volume, the portable electronic device may determine that a contaminant and/or obstruction is present, discard and/or re-determine the associated particle velocity and/or particulate matter concentration determination, indicate removal of the contaminant and/or obstruction, wait to determine the particle velocity and/or particulate matter concentration until the contaminant and/or obstruction disappears, and so forth. Therefore, inaccurate particle velocity and/or particulate matter concentration data cannot be reported and/or used.
In the present disclosure, the disclosed methods may be embodied as a set of instructions or software readable by a device. Additionally, it should be understood that the specific order or hierarchy of steps in the methods disclosed are examples of sample methods. In other embodiments, the specific order or hierarchy of steps in the methods may be rearranged while remaining within the disclosed subject matter. The accompanying method claims present elements of the various steps in a sample order, and are not necessarily meant to be limited to the specific order or hierarchy presented.
The present disclosure described may be provided as a computer program product or software which may include a non-transitory machine-readable medium having stored thereon instructions which may be used to program a computer system (or other electronic devices) to perform a process according to the present disclosure. A non-transitory machine-readable medium includes any mechanism for storing information in a form (e.g., software, processing application) readable by a machine (e.g., a computer). The non-transitory machine readable medium may take the form of, but is not limited to: magnetic storage media (e.g., floppy disks, video cassettes, etc.); optical storage media (e.g., CD-ROM); a magneto-optical storage medium; read Only Memory (ROM); random Access Memory (RAM); erasable programmable memory (e.g., EPROM and EEPROM); a flash memory; and so on.
The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the embodiments. It will be apparent, however, to one skilled in the art that the embodiments may be practiced without the specific details. Thus, the foregoing descriptions of specific embodiments described herein are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to those skilled in the art that many modifications and variations are possible in light of the above teaching.
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