阅读说明：本技术 表征飞行时间传感器和/或表征覆盖其的盖的方法和装置 (Method and device for characterizing a time-of-flight sensor and/or for characterizing a cover covering it ) 是由 M·戴拉彻 M·弗拉斯彻 H·波兰克 A·J·舍恩利布 于 2021-06-04 设计创作，主要内容包括：本公开的各实施例涉及表征飞行时间传感器和/或表征覆盖其的盖的方法和装置。提供了一种用于表征飞行时间传感器和/或表征覆盖飞行时间传感器的盖的方法(100)。方法包括：用飞行时间传感器来执行至少一个编码调制测量以便获得关于从盖反射回飞行时间传感器的光的测量数据。飞行时间传感器的测量范围被配置为针对至少一个编码调制测量立刻终止在盖之后。此外,方法包括：基于测量数据来确定特征数据,其中特征数据指示与飞行时间传感器和/或盖相关的量。(Embodiments of the present disclosure relate to methods and apparatus for characterizing time-of-flight sensors and/or characterizing covers covering the same. A method (100) for characterizing a time-of-flight sensor and/or characterizing a cover covering a time-of-flight sensor is provided. The method comprises the following steps: at least one coded modulation measurement is performed with the time-of-flight sensor to obtain measurement data regarding light reflected back from the cover to the time-of-flight sensor. The measurement range of the time-of-flight sensor is configured to terminate immediately after the cover for at least one coded modulation measurement. Further, the method comprises: characteristic data is determined based on the measurement data, wherein the characteristic data is indicative of a quantity related to the time-of-flight sensor and/or the cover.)

1. A method (100) for characterizing a time-of-flight sensor and/or characterizing a cover covering the time-of-flight sensor, the method comprising: performing (102) at least one coded modulation measurement with the time-of-flight sensor in order to obtain measurement data on light reflected back from the cover to the time-of-flight sensor, wherein a measurement range of the time-of-flight sensor is configured to terminate immediately after the cover for the at least one coded modulation measurement; and

determining (104) characteristic data based on the measurement data, wherein the characteristic data is indicative of a quantity related to the time of flight sensor and/or the cover.

2. The method of claim 1, wherein an illumination element of the time-of-flight sensor for emitting the light and a light capture element of the time-of-flight sensor for measuring the light reflected from the cover are arranged in a common cavity covered by the cover.

3. A method according to claim 1 or claim 2, wherein at least two coded modulation measurements are performed in order to obtain the measurement data.

4. The method according to any one of claims 1 to 3, wherein the characteristic data is indicative of a distance error correction value for correcting a distance value, the distance value being determined based on a depth measurement performed by the time-of-flight sensor, and wherein determining (104) the characteristic data comprises:

determining a measured distance of the cover to the time-of-flight sensor based on the measurement data; and

determining the distance error correction value based on a comparison of the measured distance of the cover to the time-of-flight sensor and a known distance of the cover to the time-of-flight sensor.

5. The method of claim 4, further comprising:

correcting, using the distance error correction value, a distance value indicative of a distance of the time-of-flight sensor to an object in a scene sensed by the time-of-flight sensor, wherein the distance value is determined based on a depth measurement performed by the time-of-flight sensor.

6. The method according to any one of claims 1 to 3, wherein the characteristic data is indicative of a measured output power of a lighting element of the time-of-flight sensor for emitting the light.

7. The method of claim 6, further comprising:

generating an illumination signal for controlling the illumination element of the time-of-flight sensor based on the characteristic data; and/or

Based on the characteristic data, a reference signal for driving electronic circuitry of a light capturing element of the time-of-flight sensor is generated in order to measure the light reflected from the cover.

8. A method according to any of claims 1 to 3, wherein the characteristic data is indicative of the condition of the lid.

9. The method of claim 8, wherein the condition of the cover indicates at least one of: no foreign matter is present on the cover; the presence of foreign matter on the cover; the presence of dirt on the cover; a fingerprint mark is present on the cover; a fluid is present on the cap.

10. The method of any of claims 1 to 9, further comprising:

storing the characteristic data in a memory with temperature data indicative of a temperature at the time-of-flight sensor during the at least one coded modulation measurement used to obtain the measurement data.

11. The method of claim 10, wherein several other pieces of feature data are stored in the memory in addition to the feature data, wherein each of the several other pieces of feature data is stored with a respective piece of temperature data indicative of a temperature at the time-of-flight sensor that is different from the temperature during the at least one coded modulation measurement used to obtain the measurement data, and wherein the method further comprises:

measuring a current temperature at the time-of-flight sensor;

selecting one of the characteristic data and the other pieces of characteristic data based on a comparison of the current temperature and the temperatures indicated by the pieces of temperature data stored in the memory together with the characteristic data and the other pieces of characteristic data; and

operating the time-of-flight sensor using selected ones of the feature data and the several other pieces of feature data.

12. The method of any preceding claim, wherein the time-of-flight sensor comprises a light capturing element for measuring the light reflected from the cover, the method further comprising:

performing one or more depth measurements on a scene with the time-of-flight sensor;

determining, based on the one or more depth measurements of the scene, whether any photosensitive elements of the light capturing element to be used for the at least one coded modulation measurement are receiving light reflected back to the time-of-flight sensor from any object in the scene; and

performing the at least one coded modulation measurement for obtaining the measurement data if no photosensitive element to be used for the at least one coded modulation measurement is receiving light reflected back to the time-of-flight sensor from any object in the scene.

13. The method of any of claims 1 to 11, wherein the at least one coded modulation measurement used to obtain the measurement data is performed in a sequence of depth measurements used to obtain a depth image.

14. An apparatus (300) for characterizing a time-of-flight sensor (310) and/or characterizing a cover (330) covering the time-of-flight sensor (310), the apparatus comprising:

a time-of-flight sensor (310) configured to perform at least one coded modulation measurement in order to obtain measurement data on light reflected back from the cover (330) to the time-of-flight sensor (310), wherein a measurement range of the time-of-flight sensor (310) is configured to terminate immediately after the cover (330) for the at least one coded modulation measurement; and

a processing circuit (320) configured to determine characteristic data based on the measurement data, wherein the characteristic data is indicative of a quantity related to the time-of-flight sensor (310) and/or the cover (330).

15. The apparatus according to claim 14, wherein the illumination element (311) of the time of flight sensor (310) for emitting light and the light capturing element (312) of the time of flight sensor (310) for measuring the light reflected from the cover (330) are arranged in a common cavity (340) covered by the cover (330).

Technical Field

The present disclosure relates to time-of-flight (ToF) sensing. In particular, examples relate to a method and apparatus for characterizing a ToF sensor and/or characterizing a cover covering a ToF sensor.

Background

The ToF module is typically covered by a cover glass to protect the ToF module from the environment. The cover glass may affect the measurement of the ToF module. In addition, various other characteristics (such as temperature) may alter the measurement of the ToF module.

Thus, characterization of the ToF sensor and/or the cover covering the ToF sensor may be required.

Disclosure of Invention

This need may be met by the subject matter of the appended claims.

One example relates to a method for characterizing a ToF sensor and/or characterizing a cover covering a ToF sensor. The method comprises the following steps: at least one coded modulation measurement is performed with the ToF sensor to obtain measurement data regarding light reflected back from the cover to the ToF sensor. The measurement range of the ToF sensor is configured immediately after termination of the cover for the at least one coded modulation measurement. In addition, the method comprises: characteristic data is determined based on the measurement data. The characteristic data indicates a quantity associated with the ToF sensor and/or the lid.

Another example relates to an apparatus for characterizing a ToF sensor and/or characterizing a cover covering a ToF sensor. The device includes: a ToF sensor configured to perform at least one coded modulation measurement in order to obtain measurement data on light reflected back from the cover to the ToF sensor. The measurement range of the ToF sensor is configured to terminate immediately after the cover for at least one coded modulation measurement. The device also includes: processing circuitry configured to determine characteristic data based on the measurement data. The characteristic data indicates a quantity associated with the ToF sensor and/or the lid.

Drawings

Some examples of apparatus and/or methods will now be described, by way of example only, with reference to the accompanying drawings, in which

Fig. 1 illustrates a flow chart of an example of a method for characterizing a ToF sensor and/or characterizing a cover covering a ToF sensor;

fig. 2 illustrates an exemplary arrangement of a ToF sensor and a cover; and

fig. 3 illustrates an example of an apparatus for characterizing a ToF sensor and/or characterizing a cover covering a ToF sensor.

Detailed Description

Various examples will now be described more fully with reference to the accompanying drawings, in which some examples are illustrated. In the drawings, the thickness of lines, layers and/or regions may be exaggerated for clarity.

Accordingly, while other examples are capable of various modifications and alternative forms, specific examples thereof are shown in the drawings and will be described below in detail. However, the detailed description does not limit other examples to the particular forms described. The disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure. Throughout the description of the figures, the same or similar reference numerals refer to the same or similar elements which may be implemented the same or in modified forms while providing the same or similar functionality when compared to each other.

It will be understood that when an element is referred to as being "connected" or "coupled" to another element, the elements may be directly connected or coupled or connected or coupled via one or more intervening elements. If an "or" is used to combine two elements a and B, it should be understood that all possible combinations are disclosed, i.e. only a, only B and a and B, without being explicitly or implicitly defined otherwise. An alternative wording for the same combination is "at least one of a and B" or "a and/or B". The same applies, mutatis mutandis, to combinations of more than two elements.

The terminology used herein to describe particular examples is not intended to be limiting of other examples. Other examples may also use multiple elements to implement the same functionality, whenever singular forms such as "a," "an," and "the" are used and only a single element is used, neither explicitly nor implicitly defined as being mandatory. Also, while the functionality is subsequently described as being implemented using a plurality of elements, other examples may implement the same functionality using a single element or processing entity. It will be further understood that the terms "comprises," "comprising," "includes" and/or "including," when used, specify the presence of stated features, integers, steps, operations, procedures, actions, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, procedures, actions, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientific terms) are used herein in the ordinary sense of the art to which examples thereof belong.

Fig. 1 illustrates a flow chart of an example of a method 100 for characterizing a ToF sensor and/or characterizing a cover covering a ToF sensor. Method 100 will be described further below with reference to fig. 2, which fig. 2 illustrates an exemplary arrangement of ToF sensor 210 and cover 220 covering ToF sensor 210.

The method 100 comprises: at least one Coded Modulation (CM) measurement is performed 102 with ToF sensor 210 in order to obtain measurement data of light reflected back from cover 220 to ToF sensor 210. In general, any number of CM measurements may be performed. For example, exactly one (i.e., a single) CM measurement may be performed in order to obtain measurement data. In other examples, at least two, three, four, or more CM measurements may be performed in order to obtain measurement data. In other words, the measurement of the lid 220 comprises one or several frames.

As can be seen from fig. 2, in each CM measurement, light 201 is emitted by the illumination element 211 of the ToF sensor 210. The illumination element 211 generates light 201 based on an illumination signal that exhibits a series of alternating high and low pulses of varying duration (length). Thus, the light 201 is a series of light pulses with varying pulse lengths and varying pulse intervals. For example, the illumination element 211 may include one or more Light Emitting Diodes (LEDs) or one or more laser diodes (e.g., one or more Vertical Cavity Surface Emitting Lasers (VCSELs)) that are excited based on the illumination signal.

Light 201 is reflected from lid 220 back to ToF sensor 210. Specifically, light 201 is reflected (at least partially) from cover 220 to light capturing element 212 of ToF sensor 210. The light 201 may be reflected at the surface of the cover 220 and/or inside the cover 220 (within the cover 220). The reflected light is denoted by reference numeral 202 in fig. 2. The reflected light 202 reaches the ToF sensor 210 without exiting the module. The light capture element 212 measures the reflected light 202. The light capturing element 212 may include various components such as, for example, optical components (e.g., one or more lenses) and electronic circuitry. For example, the electronic circuit arrangement may comprise an image sensor comprising a plurality of light sensitive elements or pixels (e.g. each image sensor comprising a Photonic Mixer Device (PMD)), and driver electronics for the image sensor. All or only selected ones of the multiple light sensitive elements/pixels may be used for measuring the reflected light 202. The reference signal is used to drive the electronic circuitry (e.g., photosensitive elements or pixels) of the light capturing element 212 in order to measure the reflected light 202. Similar to what was described above for the illumination signal used to drive the illumination element 211, the reference signal exhibits a series of alternating high and low pulses of varying duration (length). It is noted that the illumination signal and the reference signal used for CM measurements may be the same, time shifted (phase shifted) with respect to each other and/or different from each other. Additionally, if more than one CM measurement is performed, different illumination signals and/or reference signals may be used for the individual CM measurements.

Typically, the illumination element 211 and the light capturing element 212 are arranged in a common cavity covered (at least partially) by a cover 220 to protect the ToF sensor 210 from dust, moisture, dirt, etc. The cover 220 may be made of, for example, glass, plastic, or any other suitable material. For example, the cover 220 may be a glass cover of a mobile phone or an automotive ToF system. In some examples, the cover 220 may be a display, such as an OLED (organic light emitting diode) display or a micro LED display, or a portion thereof. It is to be noted that the cover 220 may be any element capable of protecting the ToF sensor 210 from the surrounding environment and being at least partially transparent to the modulated light 201 emitted by the illumination element 211.

The measurement range of the ToF sensor is configured to terminate immediately (immediately) behind the cover for at least one coded modulation measurement according to the method 100. This is exemplarily depicted in fig. 2, fig. 2 illustrating a measurement range 213 of the ToF sensor 210. This measurement range 213 is a distance (depth) range in which the ToF sensor 210 can sense the distance of the object from the ToF sensor 210 based on the light reflected back from the object to the ToF sensor 210. In the example of fig. 2, measurement range 213 begins at a distance d from ToF sensor 210₀And terminates at a distance d from ToF sensor 210₁. Limiting the distance d of the measuring range 213₁Immediately (e.g., instantaneously) following distance d, which represents the distance of cover 220 from ToF sensor 210_c. For example, the measurement range 213 of the ToF sensor 210 may end less than 50cm, 30cm, 10cm, 5cm, 1cm, or 5mm behind the cover 220 (i.e., the distance d)₁And a distance d_cMay differ by less than, for example, 50cm, 30cm, 10cm, 5cm, 1cm, or 5 mm).

The measurement range of ToF sensor 210 for at least one CM measurement may be adjusted by adjusting the pulse duration (length) of the high and low pulses in the illumination signal and/or the reference signal. In addition, the measurement range of ToF sensor 210 can be adjusted by adjusting the time shift (phase shift) between the illumination signal and the reference signal. By modulating light 201 using CM, the response of ToF sensor 210 can be limited to a distance similar to the optical path between ToF sensor 210 and cover 220. The modulation code based on the illumination signal and the reference signal may be selected, for example, to have a high slope to mitigate the response of ToF sensor 210 to reflections off objects behind cover 220. Therefore, only the light reflected by the cover 220 may be measured.

ToF sensor 210 generates and outputs measurement data based on light reaching light capturing element 212. Due to the limitation of the measurement range 213 of the ToF sensor 210, the ToF sensor is (substantially) only sensitive to the reflected light 202 reaching the light capturing element 212 from the cover 220. Thus, for at least one CM measurement, measurement data is obtained (for) light reflected back from the cover 220 to the ToF sensor 210.

The method 100 additionally includes: the characteristic data is determined 104 based on measurement data of light reflected back from the cover 220 to the ToF sensor 210. The characteristic data indicates a quantity associated with ToF sensor 210 and/or lid 220.

The lid 220 is a known object having a known reflectivity at a known fixed distance from the ToF sensor 210. Thus, the optical path of light 201 to cover 220 and back to ToF sensor 210 has a fixed distance. Given knowledge about cover 220, reflected light 202 reaching light capturing element 212 from cover 220 allows characterization of ToF sensor 210 and cover 220. Thus, method 100 may allow characterization of ToF sensor 210 and sensor 220 by means of characteristic data derived from the following measurement data: the measurement data is of light reflected back from lid 220 to ToF sensor 210.

The characteristic data may be of various types and may indicate various quantities related to the ToF sensor and/or the lid. Hereinafter, some exemplary types of feature data will be described in detail. However, it is to be noted that the present disclosure is not limited to the examples described below.

According to some examples, the characteristic data indicates a range error correction value for correcting a range value, the range value being determined based on a depth measurement performed by ToF sensor 210. ToF sensors, such as ToF sensor 210, typically suffer from distance (depth) measurement errors (offsets) that may depend on various factors, such as temperature or aging. For example, the generation of the illumination signal and the driver electronics operation are temperature dependent. Thus, the temperature may affect the indirect light path on the cover 220. The distance measurement error is to be compensated for to obtain a correct distance (depth) measurement. As described below, the known path distance between the cover 220 and the ToF sensor 210 and the obtained measurement data enable correction of this error.

To obtain the range error correction value, determining 104 the characteristic data comprises: the measured distance of the cover 220 to the ToF sensor 210 is determined based on the measurement data. In other words, the distance of the lid 220 to the ToF sensor 210 is measured via at least one CM measurement. Additionally, determining 104 the characteristic data includes: the distance error correction value is determined based on a comparison of the measured distance of the cover 220 to the ToF sensor 210 and the known distance of the cover 220 to the ToF sensor 210. By comparing the measured distance of cap 220 to ToF sensor 210 with the known distance of cap 220 to ToF sensor 210, the difference between the measured distance of cap 220 to ToF sensor 210 and the actual distance of cap 220 to ToF sensor 210 can be determined and a distance error correction value can be derived therefrom.

Assuming that determining a distance value based on one or more depth measurements performed by ToF sensor 210 indicates a distance of ToF sensor 210 from an object in a scene (not shown in fig. 2) sensed by ToF sensor 210, method 100 may further include: the distance value is corrected using the determined distance error correction value. For example, the range error correction value may be a range error correction offset added to or subtracted from the range value, or the range error correction value may be a factor multiplied by the range value. Accordingly, the distance value that is subject to the distance measurement error of ToF sensor 210 can be corrected to provide an error-corrected distance value.

For example, if the light capturing element 212 comprises a plurality of light sensitive elements or pixels, a respective distance error correction value may be determined for each or at least a part of the plurality of light sensitive elements or pixels. In other words, the distance error correction value may be calculated on a pixel-by-pixel basis.

In other examples, the characteristic data is indicative of the measured output power of the lighting element 211. The output power of the lighting element 211 may depend on various factors, such as temperature or aging. The reflectivity of the cover 220 is assumed to be substantially constant. Thus, the reflected light 202 reaching the light capturing element 212 is proportional to the output power of the illumination element 211. By digitizing the reflected light 202 reaching the light capturing element 212, the current output power of the illumination element 211 can be measured. For example, if the output power of the lighting element 211 drifts due to temperature changes, the drift of the output power may be measured and used as an input to a control system (controller) of the lighting element 211 to adjust the emitted optical power. Thus, a constant optical power output of the lighting element 211 may be achieved. For example, a constant optical power output of the lighting element 211 for different temperatures may be achieved. For example, an illumination signal for controlling the illumination element 211 may be generated based on the characteristic data according to the method 100. By varying the illumination signal based on the characteristic data, the output power of the illumination element 211 can be controlled. Similarly, duty cycle adaptation, pulse skipping or exposure time adaptation may be performed based on the characteristic data to achieve a (substantially) constant average output power of the lighting elements 211. For example, a control algorithm for controlling the light emission of the lighting elements 211 may receive as input the characteristic data. Alternatively or additionally, a reference signal for driving the electronic circuitry of the light capturing element 212 may be generated based on the characteristic data according to the method 100. By varying the reference signal based on the characteristic data, the operation of the light capturing element 212 may be adapted to the measured output power of the illumination element 211.

Where lighting element 211 comprises more than one light source (e.g., an LED or VCSEL), method 100 may be applied separately to each of the light sources to separately measure the output power of the light sources of lighting element 211. Thus, each of the light sources of the lighting element 211 may be individually controlled based on the respective measured output power.

In still other examples, the characteristic data indicates a condition of the lid. Different conditions of the cover 220 affect the reflectivity of the cover 220 and, therefore, may affect (change) the light emission and/or reception characteristics of the ToF sensor 210. The reflectivity of the cover 220 is known for at least one particular condition of the cover 200. Thus, the reflected light 202 may be used to classify the condition of the cover. The condition of the cap 220 may, for example, indicate at least one of: no foreign matter is present on the cover 220; foreign matter (e.g., dust, liquid droplets) is present on the cover 220; dirt is present on the cover 220; one or more fingerprints are present on the cover 220; there is fluid on the cap 220. For example, dirt on the cover 220 may alter the reflectivity of the cover such that the reflected light 202 exhibits certain characteristics. Thus, the measurement data obtained for at least one CM measurement may exhibit a certain characteristic in the presence of dirt on the cover 220. The condition of the cover 220 may be determined by comparing measurement data obtained for at least one CM measurement when dirt is present on the cover 220 with reference data for one or more predefined conditions of the cover 220.

In some examples, the method 100 may further include: the characteristic data is output to other circuit means, for example an application processor.

Method 100 may be used during operation of ToF sensor 210. For example, at least one CM measurement for obtaining measurement data may be performed in a depth measurement sequence for obtaining a depth image. Thus, the determined feature data may be used in obtaining the depth image. For example, if the determined feature data indicates a distance error correction value as described above, the distance value determined based on the depth measurement sequence may be corrected using the distance error correction value in obtaining the depth image. Similarly, if the characteristic data indicates a measured output power of the lighting element 211, the output power of the lighting element 211 during the depth measurement sequence may be controlled based on the measured output power to achieve an (substantially) constant average output power of the lighting element 211 during the depth measurement sequence. The at least one CM measurement for obtaining measurement data may be performed at any location in a depth measurement sequence for obtaining a depth image.

In other examples, the at least one CM measurement for obtaining measurement data may be performed occasionally, i.e. independently of being performed in the depth measurement sequence for obtaining the depth image. For example, if there are no reflective objects in the scene sensed by ToF sensor 210 that may affect the measurement, at least one CM measurement for obtaining measurement data may be performed. Thus, the method 100 may further comprise: performing one or more depth measurements on the scene with ToF sensor 210; and determining, based on one or more depth measurements of the scene (e.g., based on data obtained from the one or more depth measurements), whether any photosensitive elements (pixels) in the light capture element 212 (intended) to be used for the at least one CM measurement are receiving light reflected back to the ToF sensor 210 from any object in the scene. At least one CM measurement for obtaining measurement data is performed (only if) no light sensitive elements (pixels) to be used for the at least one CM measurement are receiving light reflected back to the ToF sensor 210 from any object in the scene.

According to the method 100, the characteristic data may be stored in the (data) memory together with temperature data indicative of the temperature at the ToF sensor 210 during at least one CM measurement for obtaining measurement data. The temperature at ToF sensor 210 may, for example, indicate the temperature at illumination element 211, light capture element 212, or a sub-element thereof. For example, one or more temperature sensors may be disposed at ToF sensor 210 to measure temperature and provide temperature data. The characteristic data may be stored in memory along with the temperature data, for example, during operation of ToF sensor 210 or at factory calibration. The memory may be a memory of ToF sensor 210 or an external memory accessible to ToF sensor 210.

In addition to the characteristic data, several other pieces of characteristic data may be stored in the memory. Each of the other several pieces of characteristic data is stored with a corresponding piece of temperature data indicating a temperature at the ToF sensor 210 that is different from the temperature during at least one CM measurement used to obtain the measurement data. For example, multiple CM measurements may be taken at different temperatures to obtain corresponding pieces of characteristic data for the different temperatures. Thus, the characteristic data may be used as calibration data, i.e. temperature-dependent calibration data, for different temperatures. To obtain characterization data for a target (desired) temperature, the method 100 may include: control the ToF sensor 210 to heat to the target temperature (e.g., by controlling the ToF sensor 210 to continuously perform ToF measurements until the target temperature is reached) and perform at least one CM measurement for obtaining measurement data once the target temperature has been reached (after the target temperature has been reached).

The stored temperature-related calibration data may be used by ToF sensor 210 to adjust its operation (e.g., periodically, repeatedly) based on the current temperature. For example, the method 100 may include: the current temperature at ToF sensor 210 is measured (e.g., using the temperature sensor described above). Additionally, the method 100 may include: one of the characteristic data and the other pieces of characteristic data is selected based on a comparison of the current temperature and the temperatures indicated by the respective temperature information (i.e., the pieces of temperature data) stored in the memory together with the characteristic data and the other pieces of characteristic data. The method 100 may additionally include: ToF sensor 210 is operated using selected ones of the characteristic data and other pieces of characteristic data. For example, if several pieces of characterization data indicate respective distance error correction values for different temperatures, an appropriate distance error correction value for the current temperature may be selected based on a simple temperature measurement at ToF sensor 210. Similarly, if several pieces of characteristic data indicate the respective measured output power of the lighting element 211 for different temperatures, suitable calibration data for controlling the lighting element 211 for the current temperature may be selected based on a simple temperature measurement at the ToF sensor 210. In other words, only the temperature may be measured during operation to select the corresponding calibration data for error correction.

In addition, the corresponding piece of characteristic data stored in the memory together with the corresponding piece of temperature data may be updated with the following characteristic data: the characterization data is newly determined according to the method 100 for the same temperature as indicated by the stored piece of temperature data.

As described above for various examples, the light reflected by the cover 220 may be used for system temperature compensation.

Also illustrated in fig. 3 is an example of an apparatus 300 for characterizing a ToF sensor and/or characterizing a cover covering a ToF sensor according to the proposed technique. Device 300 includes ToF sensor 310. The ToF sensor 310 comprises an illumination element 311 and a light capturing element 312 for performing ToF measurements according to the techniques described above. The lighting element 311 and the light capturing element 312 are arranged in a common cavity 340 (at least partially) covered by a cover 330. In particular, ToF sensor 310 is configured to perform at least one CM measurement in order to obtain measurement data of light reflected back from cover 330 to ToF sensor 310. The measurement range of ToF sensor 310 is configured to terminate immediately (shortly) after cover 330 for at least one CM measurement.

In addition, the apparatus 300 includes a processing circuit 320. For example, the processing circuit 320 may be a single special-purpose processor, a single shared processor, or multiple individual processors, some or all of which may be shared, digital information processor (DSP) hardware, an Application Specific Integrated Circuit (ASIC), or a Field Programmable Gate Array (FPGA). Processing circuit 320 may optionally be coupled to Read Only Memory (ROM), Random Access Memory (RAM), and/or non-volatile memory, for example, for storing software. The processing circuit 320 is configured to perform processing in accordance with the techniques described above. In particular, the processing circuit 320 is configured to determine the characteristic data based on the measurement data. The characteristic data indicates a quantity associated with ToF sensor 310 and/or cover 330.

The apparatus 300 may also include additional hardware-conventional and/or custom.

Examples as described herein may be summarized as follows:

some examples are provided that relate to a method for characterizing a ToF sensor and/or characterizing a cover covering a ToF sensor. The method comprises the following steps: at least one coded modulation measurement is performed with the ToF sensor to obtain measurement data regarding light reflected back from the cover to the ToF sensor. The measurement range of the ToF sensor is configured to terminate immediately after the cover for at least one coded modulation measurement. In addition, the method comprises: characteristic data is determined based on the measurement data. The characteristic data indicates a quantity associated with the ToF sensor and/or the lid.

According to some examples, the illumination element of the ToF sensor for emitting light and the light capturing element of the ToF sensor for measuring light reflected from the cover are arranged in a common cavity covered by the cover.

In some examples, at least two coded modulation measurements are performed in order to obtain measurement data.

According to some examples, the feature data indicates a distance error correction value for correcting a distance value determined based on a depth measurement performed by the ToF sensor, and determining the feature data includes: determining a measured distance of the lid to the ToF sensor based on the measurement data; and determining a distance error correction value based on a comparison of the measured distance of the lid to the ToF sensor and the known distance of the lid to the ToF sensor.

In some examples, the method further comprises: using the distance error correction value, a distance value indicative of a distance of the ToF sensor to an object in the scene sensed by the ToF sensor is corrected, wherein the distance value is determined based on a depth measurement performed by the ToF sensor.

According to some examples, the characteristic data is indicative of a measured output power of an illumination element of the ToF sensor for emitting light.

In some examples, the method further comprises: generating an illumination signal for controlling an illumination element of the ToF sensor based on the characteristic data; and/or generating a reference signal for driving electronic circuitry of a light capturing element of the ToF sensor based on the characteristic data, in order to measure light reflected from the cover.

According to some examples, the characteristic data is indicative of a condition of the lid.

In some examples, the condition of the lid indicates at least one of: no foreign matter exists on the cover; foreign matter is present on the cover; dirt is present on the cover; the cover has fingerprint traces; the fluid is present on the lid.

According to some examples, the method further comprises: the characteristic data is stored in the memory together with temperature data indicative of the temperature at the ToF sensor during at least one coded modulation measurement used to obtain the measurement data.

In some examples, in addition to the characteristic data, several other pieces of characteristic data are stored in the memory, wherein each of the several other pieces of characteristic data is stored with a respective piece of temperature data indicative of a temperature at the ToF sensor, the respective piece of temperature data being indicative of a temperature different from a temperature during at least one coded modulation measurement used to obtain the measurement data, and wherein the method further comprises: measuring a current temperature at the ToF sensor; selecting one of the characteristic data and the other pieces of characteristic data based on a comparison of a current temperature and temperatures indicated by the pieces of temperature data stored in the memory together with the characteristic data and the other pieces of characteristic data; and operating the ToF sensor using the feature data and selected ones of the other pieces of feature data.

According to some examples, the ToF sensor comprises a light capturing element for measuring light reflected from the cover, and the method further comprises: performing one or more depth measurements on the scene with a ToF sensor; determining, based on the one or more depth measurements of the scene, whether any photosensitive elements of the light capturing element to be used for the at least one coded modulation measurement are receiving light reflected back to the ToF sensor from any object in the scene; and performing at least one CM measurement for obtaining measurement data if no photosensitive element to be used for the at least one CM measurement is receiving light reflected back to the ToF sensor from any object in the scene.

In some examples, the at least one coded modulation measurement used to obtain the measurement data is performed in a depth measurement sequence used to obtain the depth image.

Other examples relate to an apparatus for characterizing a ToF sensor and/or characterizing a cover covering a ToF sensor. The device includes: a ToF sensor configured to perform at least one coded modulation measurement in order to obtain measurement data on light reflected back from the cover to the ToF sensor. The measurement range of the ToF sensor is configured to terminate immediately after the cover for at least one coded modulation measurement. The device also includes: processing circuitry configured to determine characteristic data based on the measurement data. The characteristic data indicates a quantity associated with the ToF sensor and/or the lid.

According to some examples, the illumination element of the ToF sensor for emitting light and the light capturing element of the ToF sensor for measuring light reflected from the cover are arranged in a common cavity covered by the cover.

Examples of the present disclosure may provide ToF reference measurements based on the reflection of the cover (glass).

Aspects and features mentioned and described in connection with one or more of the previously detailed examples and figures may also be combined with one or more of the other examples in place of or in addition to the same features of the other examples.

The specification and drawings merely illustrate the principles of the disclosure. Moreover, all examples recited herein are principally intended expressly to be only for illustrative purposes to aid the reader in understanding the principles of the disclosure and the concepts contributed by the inventor to furthering the art. All statements herein reciting principles, aspects, and examples of the disclosure, as well as specific examples thereof, are intended to encompass equivalents thereof.

For example, the block diagrams may illustrate high-level circuit diagrams embodying the principles of the present disclosure. Similarly, flowcharts, task diagrams, state transition diagrams, pseudocode, and the like may represent various processes, operations, or steps which may be substantially represented in computer-readable media, and thus executed by a computer or processor, whether or not such computer or processor is explicitly shown. The methods disclosed in this specification or the claims may be implemented by a device having means for performing each of the respective acts of the methods.

It will be appreciated that the disclosure of various actions, processes, operations, steps, or functions disclosed in this specification or the claims may not be construed as limited to a particular sequence, unless expressly or implicitly stated otherwise, e.g., for technical reasons. Accordingly, the disclosure of multiple acts or functions does not limit these to a particular order unless these acts or functions are not interchangeable for technical reasons. Further, in some examples, a single action, function, procedure, operation, or step may individually comprise, or may be divided into, a plurality of sub-actions, sub-functions, sub-procedures, sub-operations, or sub-steps. Such sub-acts may be included within and part of the disclosure of the single act unless explicitly excluded.

Furthermore, the following claims are hereby incorporated into the detailed description, with each claim standing on its own as a separate example. Although each claim may itself be taken as a separate example, note that: although a dependent claim may refer in the claims to a particular combination with one or more other claims, other examples may also include a combination of a dependent claim with the subject matter of each other dependent claim or independent claim. Such combinations are expressly set forth herein unless the context suggests that a particular combination is not intended. Furthermore, even if a claim does not directly depend on an independent claim, it is intended to include features of that claim directed to any other independent claim.