阅读说明：本技术 降低接收光路背景杂散光干扰的系统及其降扰方法 (System for reducing stray light interference of background of receiving light path and interference reduction method thereof ) 是由 冯新文 张俊双 徐国辉 吕通发 牟鑫 吕超 何永春 鲍明正 袁晓磊 于世奇 傅裕 于 2021-07-20 设计创作，主要内容包括：本发明涉及降低接收光路背景杂散光干扰的系统及其降扰方法,其中系统包括包括激光发射准直头、窄带滤光片、第一45°反射镜、第二45°反射镜、非球面透镜、光栏、光电探测器和反射镜；激光发射准直头生成发射激光束,发射激光束依次经反射镜、第二45°反射镜、第一45°反射镜、窄带滤光片后照射在目标物上,发射激光束在目标物上发生反射后生成回波激光束；所述回波激光束依次经过窄带滤光片、第一45°反射镜、第二45°反射镜、非球面透镜、光栏后到达光电探测器。本发明通过增加接收光程,减小接收视场角,确保能接收到大部分回波激光束的同时减小太阳辐射的背景杂散光送入到光电探测器,从而提高信噪比,并实现仪器小型化及轻量化设计。(The invention relates to a system for reducing the stray light interference of a receiving light path background and an interference reducing method thereof, wherein the system comprises a laser emission collimation head, a narrow-band filter, a first 45-degree reflector, a second 45-degree reflector, an aspheric lens, a diaphragm, a photoelectric detector and a reflector; the laser emission collimation head generates an emission laser beam, the emission laser beam sequentially passes through the reflector, the second 45-degree reflector, the first 45-degree reflector and the narrow-band filter and then irradiates on a target object, and the emission laser beam is reflected on the target object to generate an echo laser beam; the echo laser beam reaches the photoelectric detector after sequentially passing through the narrow-band filter, the first 45-degree reflector, the second 45-degree reflector, the aspheric lens and the diaphragm. The invention reduces the receiving field angle by increasing the receiving optical path, ensures that most echo laser beams can be received, and simultaneously reduces the background stray light of solar radiation to be sent to the photoelectric detector, thereby improving the signal-to-noise ratio and realizing the miniaturization and lightweight design of instruments.)

1. The system for reducing the stray light interference of the background of a receiving light path is characterized by comprising a laser emitting collimation head (001), a narrow-band filter (004), a first 45-degree reflector (006), a second 45-degree reflector (007), an aspheric lens (008), a diaphragm (009), a photoelectric detector (010) and a reflector (011), wherein the laser emitting collimation head is arranged in a laser range finder;

the narrow band filter (004) and the first 45-degree reflecting mirror (006) are arranged coaxially; the second 45-degree reflector (007), the reflector (011), the aspheric lens (008), the light barrier (009) and the photoelectric detector (010) are arranged in a coaxial mode; the second 45-degree reflector (007) and the first 45-degree reflector (006) are perpendicular to each other, the second 45-degree reflector is located right below the first 45-degree reflector, and the reflector (011) and the second 45-degree reflector (007) are parallel to each other;

the laser emission collimation head is used for generating an emission laser beam (002), the emission laser beam (002) sequentially passes through a reflector (011), a second 45-degree reflector (007), a first 45-degree reflector (006) and a narrow-band filter (004) and then irradiates on a target object (003), and the emission laser beam (002) is reflected on the target object (003) to generate an echo laser beam (005);

the echo laser beam (005) reaches the photoelectric detector (010) after passing through the narrow-band filter (004), the first 45-degree reflector (006), the second 45-degree reflector (007), the aspheric lens (008) and the diaphragm (009) in sequence, so that an optical signal is converted into an electric signal after the optical signal is received by the light sensitive surface of the photoelectric detector (010).

2. The system of claim 1, wherein the system is configured to reduce stray light interference from the background of the received light path: the photoelectric detector further comprises a data processing module electrically connected with the output end of the photoelectric detector (010), the data processing module receives the electric signal and then processes the electric signal, and data obtained after processing are displayed on an image display unit electrically connected with the data processing module.

3. The system of claim 1, wherein the system is configured to reduce stray light interference from the background of the received light path: when the divergence angle of the emitted laser beam (002) is set to alpha, alpha is not less than 0.2mrad and not more than 0.3 mrad.

4. The system of claim 3, wherein the system comprises: the divergence angle of the emitted laser beam (002) was 0.28 mrad.

5. The system of claim 3, wherein the system comprises: the receiving field angle of the photosensitive surface of the photoelectric detector is beta, and the beta is more than or equal to 0.5mrad and less than or equal to 1.2 mrad.

6. The system of claim 5, wherein the system comprises: the receiving field angle is 1 mrad.

7. The system of claim 1, wherein the system is configured to reduce stray light interference from the background of the received light path: the laser emission collimation head (001) is an optical fiber collimation head, emits emission laser beams with the wavelength of 1550 +/-10 nm, and the narrow-band filter (004) is used for filtering out background stray light outside the wavelength range of 1550 +/-10 nm.

8. The system of claim 1, wherein the system is configured to reduce stray light interference from the background of the received light path: the aspheric lens converts the echo laser beam into a point light source and converges the point light source on a photosensitive surface of the photoelectric detector, and the focal length of the aspheric lens is 30mm to 100 mm.

9. The method for reducing the stray light interference of the receiving light path background according to any one of claims 1 to 8, comprising the following steps:

step S1, generating a transmitting laser beam (002) by a laser transmitting collimation head (001), irradiating the transmitting laser beam (002) on a target object (003) after the transmitting laser beam (002) is transmitted by a reflector (011) and then sequentially passes through a second 45-degree reflector (007), a first 45-degree reflector (6) and a narrow-band filter (004), and generating an echo laser beam (005) after the transmitting laser beam is reflected by the target object;

step S2, the echo laser beam (005) firstly passes through a narrow band filter (004) to carry out filtering processing so as to filter out the background stray light outside the wavelength range of the echo laser beam (005), thereby only allowing the light in the wavelength range of the echo laser beam (005) to pass through;

step S3, the echo laser beam (005) coming out of the narrow band filter (004) is reflected by the first 45-degree reflecting mirror (006) and the second 45-degree reflecting mirror (007) in sequence to realize 180-degree deflection of a receiving light path;

step S4, the refracted echo laser beam (005) sequentially passes through an aspheric lens (008) and a diaphragm (009) and then reaches a photoelectric detector (010);

wherein, the echo laser beam (005) is focused when passing through the aspheric lens (008) to convert the echo laser beam into a point light source so as to be converged on a photosensitive surface of the photoelectric detector; the light barrier (009) can further reduce stray light from entering a photosensitive surface of the photodetector (010);

step S5, after the light sensitive surface of the photoelectric detector (010) receives the echo laser beam, converting the optical signal into an electrical signal; the photoelectric detector transmits the electric signal to the data processing module for data processing, and finally the data processing module generates distance information and transmits the distance information to the image display unit for display.

10. The method as claimed in claim 9, wherein the step of reducing stray light interference comprises: in step S4, since the mirror (011) blocks the echo laser beam when passing through the mirror (011) in the optical path of the echo laser beam returning to the photodetector, the diameter of the projection surface of the echo laser beam on the optical path where the mirror (011) is located is 5 to 10 times the diameter of the mirror in the optical path, and the blocking effect of the mirror (011) on the echo laser beam (005) can be ignored within the accuracy requirement range of the laser range finder.

Technical Field

The invention belongs to the technical field of remote laser detection, and particularly relates to a system and a method for reducing background stray light interference of a receiving light path.

Background

In the field of laser ranging at present, a laser ranging instrument is generally adopted to emit laser beams to irradiate a target object, and then echo lasers reflected by the target object are received, so that the distance between the ranging instrument and the target object can be calculated. The emitted laser beam has a divergence angle, called as an emission field angle, most of echo energy of the emitted pulse can be received when the receiving field angle is larger than or equal to the emission field angle in principle, and in order to increase the detection distance, the receiving field angle needs to be increased. However, a small receiving field angle means a large receiving focal length, which increases the size of the laser distance measuring device, and is not favorable for the miniaturization and weight reduction of the device.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a system and a method for reducing the interference of the stray light of the background of a receiving optical path, so that the receiving field angle is compressed under the condition of ensuring the integrity of a receiving signal, the interference of the stray light of the background is reduced, the signal-to-noise ratio and the measurement precision are improved, and the miniaturization and lightweight design of a distance measuring instrument is realized.

The system for reducing the stray light interference of the background of a receiving light path comprises a laser emitting collimation head, a narrow-band filter, a first 45-degree reflector, a second 45-degree reflector, an aspheric lens, a diaphragm, a photoelectric detector and a reflector, wherein the laser emitting collimation head is arranged in a laser range finder;

the narrow-band filter and the first 45-degree reflector are arranged in a coaxial mode; the second 45-degree reflector, the aspheric lens, the diaphragm and the photoelectric detector are arranged in a coaxial manner; the second 45-degree reflector and the first 45-degree reflector are perpendicular to each other, the second 45-degree reflector is positioned right below the first 45-degree reflector, and the reflector and the second 45-degree reflector are arranged in parallel to each other;

the laser emission collimation head is used for generating emission laser beams, the emission laser beams sequentially pass through the reflector, the second 45-degree reflector, the first 45-degree reflector and the narrow-band filter and then irradiate on a target object, and the emission laser beams are reflected on the target object to generate echo laser beams;

the echo laser beam sequentially passes through the narrow-band filter, the first 45-degree reflector, the second 45-degree reflector, the aspheric lens and the diaphragm and then reaches the photoelectric detector, and the light sensitive surface of the photoelectric detector receives the echo laser beam and then converts the optical signal into an electrical signal.

Furthermore, the system further comprises a data processing module electrically connected with the output end of the photoelectric detector, wherein the data processing module receives the electric signal and then processes the electric signal, and displays the processed data on an image display unit electrically connected with the data processing module.

Furthermore, the divergence angle of the emitted laser beam is set as alpha, and the alpha is more than or equal to 0.2mrad and less than or equal to 0.3 mrad. Preferably, the divergence angle of the emitted laser beam is 0.28 mrad.

Furthermore, the receiving field angle of the photosensitive surface of the photoelectric detector is beta, and the beta is more than or equal to 0.5mrad and less than or equal to 1.2 mrad.

Further, the reception field angle is 1 mrad.

Furthermore, the laser emission collimation head is an optical fiber collimation head, emits an emission laser beam with the wavelength of 1550 +/-10 nm, and the narrow-band filter is used for filtering out background stray light outside the wavelength range of 1550 +/-10 nm.

Furthermore, the aspheric lens converts the echo laser beam into a point light source and converges the point light source on a photosensitive surface of the photoelectric detector, and the focal length of the aspheric lens is 30mm to 100 mm.

The invention also provides a disturbance reduction method of the system for reducing the stray light disturbance of the background of the receiving light path, which comprises the following steps:

step S1, the laser emission collimation head generates an emission laser beam, the emission laser beam is irradiated on a target object after sequentially passing through the second 45-degree reflector, the first 45-degree reflector and the narrow-band filter after being emitted by the reflector, and the emission laser beam generates an echo laser beam after being reflected by the target object;

step S2, the echo laser beam is firstly filtered through a narrow band filter to filter out the background stray light outside the wavelength range of the echo laser beam, so that only the light in the wavelength range of the echo laser beam is allowed to pass through;

step S3, the echo laser beam coming out of the narrow band filter is reflected by the first 45-degree reflector and the second 45-degree reflector in sequence to realize 180-degree turning of a receiving light path;

step S4, the converted echo laser beam sequentially passes through an aspheric lens and a diaphragm and then reaches a photoelectric detector;

the echo laser beam is focused when passing through the aspheric lens, so that the echo laser beam is converted into a point light source to be conveniently converged on a photosensitive surface of the photoelectric detector; the light barrier can further reduce the stray light from entering the photosensitive surface of the photoelectric detector;

step S5, after the light sensitive surface of the photoelectric detector receives the echo laser beam, converting the optical signal into an electrical signal; the photoelectric detector transmits the electric signal to the data processing module for data processing, and finally the data processing module generates distance information and transmits the distance information to the image display unit for display.

Further, in step S4, since the reflector blocks the echo laser beam when passing through the reflector in the optical path of the echo laser beam returning to the photodetector, the diameter of the projection surface of the echo laser beam on the optical path where the reflector is located is 5 to 10 times the diameter of the reflector in the optical path, so that the blocking effect of the reflector on the echo laser beam can be ignored within the accuracy requirement range of the laser range finder.

By means of the technical scheme, the grating is added between the aspheric lens and the photoelectric detector to be combined with a mode of increasing the optical path, so that the receiving field angle is reduced, and the introduced interference of background stray light is reduced; considering the complexity of the surface shape of the target object and the increase of the reflection angle of the energy concentration area, the size of the photosensitive surface of the photoelectric detector is matched with the focal length design of the aspheric lens, so that the receiving field angle is about two to three times or more than three times of the transmitting field angle (the divergence angle of the transmitting laser beam), the energy of most echo laser beams is ensured to be received, and meanwhile, the background stray light of solar radiation is reduced and sent to the photoelectric detector, so that the signal-to-noise ratio is further improved, and the measurement accuracy of the instrument is improved.

The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical means of the present invention more clearly understood, the present invention may be implemented in accordance with the content of the description, and in order to make the above and other objects, features, and advantages of the present invention more clearly understandable, the following preferred embodiments are described in detail with reference to the accompanying drawings.

Drawings

Fig. 1 is a schematic block diagram of a system for reducing the stray light interference in the background of the receiving light path according to the present invention.

FIG. 2 is a schematic diagram of the optical path length of the emitted laser beam in the system for reducing the background stray light interference of the receiving optical path according to the present invention.

FIG. 3 is a schematic diagram of the optical path length of the echo laser beam in the system for reducing the background stray light interference of the receiving optical path according to the present invention.

Fig. 4 is a schematic diagram of a receiving field angle in a system for reducing the background stray light interference of a receiving optical path according to the present invention.

FIG. 5 is a schematic diagram showing the relationship between the divergence angle of the emitted laser beam and the receiving field angle in a system for reducing the background stray light interference of the receiving optical path according to the present invention.

Detailed Description

The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and preferred embodiments.

Referring to fig. 1 to 5, a system for reducing the stray light interference of the background of the receiving light path is installed in a laser range finder, and includes a laser emitting collimating head 001, a narrowband filter 004, a first 45 ° reflector 006, a second 45 ° reflector 007, an aspheric lens 008, a diaphragm 009, a photodetector 010, and a reflector 011; the laser emission collimation head is used as a light source, and the emission laser beam is produced and irradiated to a target object 003, so that the target object 003 reflects an echo laser beam 005 back to the system, and the distance measurement function is realized. Specifically, the narrow band filter 004 and the first 45 ° reflecting mirror 006 are arranged coaxially, and are located on the same horizontal plane; the second 45-degree reflector 007, the reflector 011, the aspheric lens 008, the diaphragm 009 and the photodetector 010 are arranged coaxially in sequence on a receiving optical path; second 45 speculum 007 and first 45 speculum 006 mutually perpendicular set up, and second 45 speculum is located first 45 speculum under, and speculum 011 and second 45 speculum 007 mutual parallel arrangement. The size of the mirror 011 is much smaller than the projection plane of the echo laser beam 005 on the receiving optical path, so that the blocking effect of the mirror on the echo laser beam in the optical path can be ignored within the accuracy requirement range of the laser range finder. In this embodiment, the projection surface of the echo laser beam 005 on the receiving optical path is a mirror area.

With reference to fig. 2, the laser emission collimating head is configured to generate an emission laser beam 002, the emission laser beam 002 is emitted upwards vertically, the emission laser beam 002 passes through the reflector 011, the second 45 ° reflector 007, the first 45 ° reflector 006 and the narrow band filter 004 in sequence and then irradiates on the target 003, and the emission laser beam 002 is reflected on the target 003 to generate an echo laser beam 005.

Referring to fig. 3 again, the reflected echo laser beam 005 overlaps with the emitted light path of the emitted emission laser beam, and the reflected echo laser beam has an opposite direction, and passes through the narrowband filter 004, the first 45 ° reflector 006, the second 45 ° reflector 007, the aspheric lens 008, and the optical grating 009 in sequence and then reaches the photodetector 010, so that the optical signal is converted into an electrical signal after the optical surface of the photodetector 010 receives the echo laser beam.

Preferably, the laser emission collimating head 001 is an optical fiber collimating head, which emits an emission laser beam with a wavelength of 1550 ± 10nm, and the divergence angle of the emission laser beam is small, in this embodiment, the range of the divergence angle α is 0.2mrad or less and is 0.3mrad or less, so that the size of a light spot irradiated on a target object is reduced, and a receiving field angle can easily and completely cover a long-distance light spot.

In the front end receiving optical path of the aspheric lens, echo laser beams between the narrow band filter and the first 45-degree reflector are parallel to echo laser beams between the second 45-degree reflector and the aspheric lens in opposite directions, so that a folding receiving optical path is formed, and after the echo laser beams enter the narrow band filter, the optical path is twice of the original optical path through the first 45-degree reflector and the second 45-degree reflector which are perpendicular to each other, but the length of the laser ranging instrument is unchanged, so that the design of miniaturization and light weight is realized. Meanwhile, the receiving optical path is lengthened, so that the receiving field angle is reduced, and the receiving amount of the background stray light can be reduced when the receiving field angle is reduced, so that the signal-to-noise ratio is improved. Referring to fig. 4, in the present embodiment, when the receiving angle of view is β, β is greater than or equal to 0.5mrad and less than or equal to 1.2mrad, and the receiving angle of view is preferably 1 mrad. Furthermore, as can be seen from fig. 4, the size of the receiving field angle is related to the distance between the photodetector and the aspheric lens (i.e., the focal length of the aspheric lens), and the size of the photosensitive surface of the photodetector; the smaller the focus, the larger the receiving field angle, which is in inverse proportion.

Preferably, the aspheric lens has a focusing capability to convert the echo laser beam into a point light source to be focused on the photosensitive surface of the photodetector, and in order to further reduce the length of the optical machine (i.e. the laser range finder), the focal length of the aspheric lens should be designed to be shorter, and in this embodiment, the focal length ranges from 30mm to 100 mm. The focal length is designed to match the size of the photosensitive surface of the photodetector, so that the receiving field angle in this embodiment is about 1mrad, which corresponds to a divergence angle of more than three times 0.28 mrad.

Preferably, a narrow-band filter 004 is arranged at the front end of the aspheric lens 008 to filter the echo laser beam and filter out background stray light outside a required wavelength range, so that only light in the wavelength range of the emitted laser beam is allowed to pass through; for example, if the emitted laser beam has a wavelength of 1550 ± 10nm, the window on the narrowband filter 004 only allows light in the wavelength range to pass through, and isolates all stray interfering light outside the wavelength range. It should be noted that, when the emitted laser beam passes through the narrow band filter 004, the light path is transmitted inside the optical machine, and is not exposed outside, so that background stray light does not need to be considered, that is, the narrow band filter does not need to play a role in filtering.

The rear end of the aspheric lens 008 is provided with a diaphragm which can further isolate stray light larger than a designed receiving field angle from entering the photosensitive surface. In the above, the size of the photosensitive surface is designed in combination with the focal length of the aspheric lens, so that the final receiving angle of view is 1mrad, but it should be noted that the receiving angle of view can ensure sufficient reception of echo energy as long as it is larger than the divergence angle, so the relationship between the receiving angle of view and the divergence angle should be in a reasonable range, which is designed according to practical needs, and the invention does not limit the divergence angle, the receiving angle of view and the proportional relationship between the two angles.

With the above system for reducing the stray light interference of the background of the receiving light path, the method for reducing the stray light interference of the background of the receiving light path specifically comprises the following steps:

step S1, generating a transmitting laser beam 002 by a laser transmitting collimation head 001, irradiating the transmitting laser beam 002 on a target 003 after sequentially passing through a second 45-degree reflector 007, a first 45-degree reflector 6 and a narrow-band filter 004 after being transmitted by a reflector 011, and generating an echo laser beam 005 after the transmitting laser beam is reflected by the target;

step S2, the echo laser beam 005 firstly passes through the narrow band filter 004 to perform filtering processing to filter out the stray light of the background outside the wavelength range of the echo laser beam 005, so as to allow only the light in the wavelength range of the echo laser beam 005 to pass through;

step S3, the echo laser beam 005 coming out of the narrowband filter 004 then sequentially reflects through the first 45 ° reflector 006 and the second 45 ° reflector 007 to realize 180 ° deflection of the receiving light path;

step S4, the refracted echo laser beam 005 passes through the aspheric lens 008 and the diaphragm 009 in sequence and then reaches the photodetector 010;

wherein, the echo laser beam 005 is focused when passing through the aspheric lens 008, so that the echo laser beam is converted into a point light source to be converged on the photosensitive surface of the photodetector; the light barrier 009 can further reduce stray light from entering the photosensitive surface of the photodetector 010;

step S5, after the optical sensing surface of the photodetector 010 receives the echo laser beam, converting the optical signal into an electrical signal; the photoelectric detector transmits the electric signal to the data processing module for data processing, and finally the data processing module generates distance information and transmits the distance information to the image display unit for display.

It should be noted that, in step S4, since the mirror will have a very small blocking effect on the echo laser beam when passing through the mirror in the optical path of the echo laser beam returning to the photodetector, in this embodiment, the diameter of the projection surface of the echo laser beam on the optical path where the mirror is located is 5 to 10 times, preferably 5 to 6 times, the diameter of the mirror in the optical path, and in short, the size of the mirror 011 is very small compared with the diameter of the echo laser beam, so that the blocking effect of the mirror on the echo laser beam can be ignored within the accuracy requirement range of the laser range finder, and the measurement result is hardly affected.

The interference reduction method of the system for reducing the interference of the background stray light of the receiving light path, which is provided by the invention, adopts the first 45-degree reflecting mirror and the second 45-degree reflecting mirror which are vertical to each other to realize the folding of the receiving light path, increases the receiving light path and reduces the receiving field angle, and further reduces the introduction of the background stray light by combining a mode of adding a diaphragm between the aspheric lens and the photoelectric detector. Considering the complexity of the surface shape of the target object and the increase of the reflection angle in the energy concentration area, the invention ensures that the receiving field angle beta is about two to three times or more than three times of the divergence angle alpha, ensures that most echo energy is received, and simultaneously reduces the sending of the background stray light of solar radiation into the photoelectric detector, thereby reducing the signal-to-noise ratio and influencing the measurement accuracy.

With reference to fig. 5, by the above technical solution, the receiving field half-angle S100 (i.e. half of the receiving field angle β) is larger than the diverging half-angle S200 (i.e. half of the diverging angle α), and it can be seen that the receiving field angle can completely cover the spot of the emitted laser beam with the diverging angle on the target object; otherwise, when the receiving field half angle is smaller than the divergence half angle, the coverage area of the receiving field of the remote target is smaller than the area of a light spot irradiated on the target object by the transmitting laser beam, so that the echo energy can not be fully utilized, and the receiving sensitivity is low.

The above description is only a preferred embodiment of the present invention, and any person skilled in the art can make any simple modification, equivalent change and modification to the above embodiments according to the technical essence of the present invention without departing from the scope of the present invention, and still fall within the scope of the present invention.