Imaging equipment, laser radar and receiving system thereof

Abstract

The invention is suitable for the technical field of laser radars, and provides an imaging device, a laser radar and a receiving system thereof, and the receiving system of the laser radar comprises a receiving element, a polarization beam splitting element and a detector assembly. The receiving element is used for receiving reflected light of a target to be measured and transmitting the received reflected light to the incident plane of the polarization beam splitting element; the polarization beam splitting element is used for separating a p polarization component and an s polarization component in the reflected light transmitted by the receiving element and transmitting the p polarization component and the s polarization component to the detector assembly; the detector assembly comprises a first detector and a second detector, the first detector is used for detecting the p polarization component, and the second detector is used for detecting the s polarization component; according to the scheme, p and s polarization components in the reflected light collected by the receiving element are separated through the arranged polarization beam splitting element and the detector assembly, the p and s polarization components are detected by the two detectors respectively, and substance identification of the to-be-detected target is achieved through the polarization difference.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser radar, and in particular relates to an imaging device, a laser radar and a receiving system thereof. Background Art

[0002] LiDAR is a remote sensing technology that uses lasers to perform three-dimensional detection. It consists of a transmitting system and a receiving system. The transmitting system is used to emit pulsed lasers to illuminate the target to be measured, and the receiving system is used to receive the reflected light from the target to be measured. By recording the time difference between the transmitted pulse and the received pulse, the longitudinal distance of the object is calculated.

[0003] However, conventional lidar can only detect the target position but cannot obtain the target's material information.

[0004] Therefore, it is urgent to design a receiving system that can perform material identification. Summary of the invention

[0005] The purpose of the embodiments of the present invention is to provide an imaging device, a laser radar and a receiving system thereof, aiming to solve the problem that the current laser radar cannot obtain the material information of the target.

[0006] The embodiment of the present invention is implemented as follows: a receiving system of a laser radar, the receiving system of the laser radar comprising a receiving element, a polarization beam splitting element and a detector assembly; the receiving element is used to receive reflected light of a target to be measured, and transmit the received reflected light to an incident surface of the polarization beam splitting element; the polarization beam splitting element is used to separate a p-polarization component from an s-polarization component in the reflected light transmitted by the receiving element, and transmit the separated components to the detector assembly; the detector assembly comprises a first detector and a second detector, the first detector is used to detect the p-polarization component, and the second detector is used to detect the s-polarization component;

[0007] Among them, the polarization direction of p-polarized light is in the plane formed by the incident, reflected, refracted light and the normal line, and the polarization direction of s-polarized light is perpendicular to the plane formed by the incident, reflected, refracted light and the normal line.

[0008] The present invention also provides a laser radar, which includes a transmitting system and the receiving system, wherein the transmitting system at least includes a laser and a deflection structure.

[0009] The laser is used to emit light of a set wavelength to illuminate the target to be measured, wherein the light of the set wavelength includes light polarized in the p direction and light polarized in the s direction;

[0010] The deflection structure is arranged on the optical path of the outgoing light of the laser, and is used to deflect the outgoing light of the laser so that the outgoing light of the laser can scan in a two-dimensional space.

[0011] The present invention also provides an imaging device, which includes an illumination light source, a light collecting system and the receiving system.

[0012] The illumination light source is used to emit a laser beam in a p-polarization direction or a laser beam in an s-polarization direction to the target to be measured.

[0013] The light collecting system is arranged on the optical path of the outgoing light of the polarization beam splitting element;

[0014] For the laser radar receiving system given in the above embodiment, the p and s polarization components in the reflected light collected by the receiving element are separated by the polarization beam splitter element and the detector assembly, and are detected respectively by two detectors, and the polarization difference is used to realize the material identification of the target to be measured. The overall structure of the receiving system is simple and easy to promote and apply. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of the structure of a laser radar receiving system provided by an embodiment of the present invention;

[0016] Figure 2 A schematic diagram of the structure of a laser radar provided by an embodiment of the present invention;

[0017] Figure 3 A schematic structural diagram of an imaging device provided by an embodiment of the present invention;

[0018] Figure 4 Schematic diagram of the propagation principle of light in different media;

[0019] Figure 5 The reflectivity R of the p-polarized component of the glass reflected light provided in the embodiment of the present invention is p The reflectivity R of the s-polarization component si Trend graph with incident angle.

[0020] In the accompanying drawings: 100-receiving system; 101-receiving element; 102-polarization beam splitting element; 103-first detector; 104-second detector; 105-light collecting system; 106-digital micromirror array; 200-transmitting system; 201-laser; 202-deflection structure; 203-transmitting light element; 300-illumination light source. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0022] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0023] Figure 1 A schematic diagram of the structure of a laser radar receiving system provided in an embodiment of the present invention, wherein the laser radar receiving system 100 includes a receiving element 101, a polarization beam splitting element 102 and a detector assembly;

[0024] The receiving element 101 is used to receive the reflected light of the target to be measured, and transmit the received reflected light to the incident surface of the polarization beam splitting element 102;

[0025] The polarization beam splitting element 102 is used to separate the p-polarization component and the s-polarization component in the reflected light transmitted by the receiving element 101, and transmit them to the detector assembly;

[0026] The detector assembly includes a first detector 103 and a second detector 104 . The first detector 103 is used to detect the p-polarization component, and the second detector 104 is used to detect the s-polarization component.

[0027] In an example of this embodiment, the reflected light of the target to be measured can be the reflected light after an external light source, a laser or an illumination light source illuminates the target to be measured, and the receiving element 101 can be a single lens, a lens group, a Fresnel lens, etc.; the first detector 103 and the second detector 104 can be photodiodes, photomultiplier tubes or avalanche photodiodes.

[0028] The laser radar receiving system provided in this embodiment separates the p and s polarization components in the reflected light collected by the receiving element by means of the polarization beam splitting element and the detector assembly, and detects them respectively by two detectors, and realizes material identification of the target to be measured by utilizing the polarization difference. The overall structure of the receiving system is simple and is easy to promote and apply.

[0029] The polarization beam splitter element utilizes the principle that the refractive index of light in different media is different. Figure 4 As shown, the reflection phenomenon of light can be analyzed according to the electromagnetic theory of light and the boundary conditions of the electromagnetic field. The electric vector of the incident light is decomposed into the p-polarization component E parallel to the incident plane. p and the s-polarization component E perpendicular to the incident plane s , then the reflectivity R of the p-polarized component in the reflected light p The reflectivity R of the s-polarization component s They are:

[0030]

[0031] Where n1 sin i1 = n2 sin i2, n1 and n2 are the refractive indices of air and the object respectively, i1 is the incident angle of light to the object. If the light is incident from air to glass, then n1 = 1, n2 = 1.5, and the reflectivity of the p-polarized component is R p The reflectivity R of the s-polarization component s The curve of the change with the incident angle is as follows Figure 5 As shown. It can be seen that for a mirror-reflecting object such as glass, the reflectivity of the p-polarization component is always higher than that of the s-polarization component.

[0032] Therefore, in some embodiments, for mirror-reflecting objects such as glass and smooth metal, when the incident light is linearly polarized light, the target reflected light is approximately linearly polarized:

[0033] When the incident light is linearly polarized light in the p-polarization direction, the reflected light contains more p-polarization components and less s-polarization components;

[0034] When the incident light is linearly polarized light in the s-polarization direction, the reflected light contains more s-polarization components and less p-polarization components;

[0035] When the incident light is completely unpolarized light, the target reflected light is unpolarized light, and the s-polarization component is always higher than the p-polarization component.

[0036] For ordinary rough objects, when light is incident on the surface of the object, the surface will reflect the light in all directions. Therefore, regardless of whether the incident light is linearly polarized light, the target reflected light is always unpolarized light, and the p-polarization component is almost equivalent to the s-polarization component.

[0037] In summary, by measuring the polarization characteristics of the target light while measuring the intensity of the target light, the polarization characteristics of the light, namely the p-polarization component and the s-polarization component, can identify the target component.

[0038] like Figure 1 As shown, in another embodiment scenario, the polarization beam splitting element is a polarization beam splitting prism or a Glan Taylor prism. Preferably, the polarization beam splitting element is a polarization beam splitting prism.

[0039] like Figure 1 As shown, in another embodiment, the sensitivity of the first detector 103 is different from the sensitivity of the second detector 104 .

[0040] In this embodiment, the p and s polarization components are detected respectively by two detectors with different sensitivities, which reduces the requirements on the dynamic range of the detectors and further reduces the construction cost of the equipment.

[0041] In addition, in some embodiment scenarios, for example, when the target object (i.e., the target to be measured) is a mirror-reflecting object such as glass or smooth metal, the first detector 103 and the second detector 104 included in the detector assembly may also use detectors with the same sensitivity. Detectors with the same sensitivity can simplify the complexity of setting up the receiving system, reduce the difficulty of distinction, and facilitate maintenance.

[0042] In another embodiment, the detector assembly further comprises a controller, the controller is connected to a memory, the memory stores a pre-calibrated database,

[0043] The controller is used to determine the material of the target to be measured according to the difference between the p-polarization component and the s-polarization component,

[0044] Or the material of the target to be measured is determined based on the comparison between the difference and the data in the pre-calibrated database.

[0045] In this embodiment, the pre-calibrated database is formed after pre-calibration based on material properties of known objects, that is, objects of known materials are used in advance to pre-calibrate the intensity difference detected by the first detector 103 and the second detector 104 .

[0046] like Figure 2 As shown, in another embodiment, a laser radar is provided, the laser radar comprising a transmitting system 200 and any of the above-described receiving systems 100, the transmitting system 200 comprising at least a laser 201 and a deflection structure 202,

[0047] The laser 201 is used to emit light of a set wavelength to illuminate the target to be measured, wherein the light of the set wavelength includes light polarized in the p direction and light polarized in the s direction;

[0048] The deflection structure 202 is disposed on the optical path of the outgoing light of the laser, and is used to deflect the outgoing light of the laser so that the outgoing light of the laser can scan in a two-dimensional space.

[0049] In an example of this embodiment, the set wavelength light at least includes separable p-direction polarized light and s-direction polarized light. The laser radar can be applied to material identification or other remote sensing detection fields, and has the following modes when performing material identification:

[0050] The laser 201 emits polarized light in the p direction to illuminate the target to be measured, that is, the target object. If the intensity detected by the first detector 103 is higher than the intensity detected by the second detector 104, the target object is glass or metal; if the intensity detected by the first detector 103 is equivalent to the intensity detected by the second detector 104, the target object is an ordinary diffuse reflection object;

[0051] The laser 201 emits polarized light in the s direction to illuminate the target object. If the intensity detected by the first detector 103 is lower than the intensity detected by the second detector 104, the target object is glass or metal; if the intensity detected by the first detector 103 is equal to the intensity detected by the second detector 104, the target object is an ordinary diffuse reflection object.

[0052] The laser 201 emits completely non-polarized light to illuminate the target object. If the intensity detected by the first detector 103 is lower than the intensity detected by the second detector 104, the target object is glass or metal; if the intensity detected by the first detector 103 is equivalent to the intensity detected by the second detector 104, the target object is an ordinary diffuse reflection object.

[0053] In addition, in one implementation scenario, a material pre-calibration can be performed and used as a reference to determine the material properties of the target to be tested. That is, by using an object of known material in advance, the intensity difference detected by the first detector 103 and the second detector 104 is pre-calibrated, so that in the test, the material of the target to be tested can be determined according to the intensity difference detected by the first detector 103 and the second detector 104.

[0054] In summary, through the above-mentioned multiple modes of detection, the material of the target to be tested can be determined, and the overall structure of the system is relatively simple and has high applicability.

[0055] like Figure 2 As shown, in another embodiment, the transmitting system further includes an emitting light element 203, and the emitting light element 203 is disposed on the optical path of the outgoing light of the deflection structure 202, and is used to emit the outgoing light of the deflection structure 202 toward the target to be measured.

[0056] In this embodiment, the deflection structure 202 is one of a rotating multi-faceted reflection prism, a MEMS (micro-electro-mechanical system, MEMS) galvanometer, and a digital micro-mirror array (digital micro-mirror device, DMD); the emitting light element adopts a single lens or a lens group composed of multiple lenses.

[0057] The specific structures of the deflection structure 202 and the light emitting element in this embodiment are not limited thereto. In practical applications, those skilled in the art can flexibly select and adjust them as needed to facilitate the implementation of this solution, which will not be described in detail here.

[0058] like Figure 3As shown, based on the laser radar receiving system, in another embodiment, an imaging device is provided, which is applied to single-pixel imaging; the imaging device includes an illumination light source 300, a light collecting system 105 and any of the above-mentioned receiving systems 100,

[0059] The illumination light source 300 is used to emit a laser beam in a p-polarization direction or a laser beam in an s-polarization direction to the target to be measured.

[0060] The light collecting system 105 is arranged on the optical path of the outgoing light of the polarization beam splitting element 102 .

[0061] In this embodiment, the polarization beam splitting element 102 may be a digital micromirror array (DMD) 106, wherein the illumination light source 300 is not limited to a laser, and may be sunlight or a conventional illumination lamp. In the figure, the solid line represents the emitted light, and the dotted line represents the received light, such as an LED lamp or other illumination lamp; the light collecting system includes one or more light collectors, and the outgoing light of the polarization beam splitting element 102 is collected by one or more of the light collectors. The digital micromirror array (DMD) 106 is configured as follows: the target light of different sub-fields (sub-field 1, sub-field 2, sub-field 3) generated by the illumination light irradiating the object is imaged on the DMD through the receiving element 101, and the micromirrors at different positions on the DMD reflect the target light corresponding to the different sub-fields into the light collecting system for collection;

[0062] In addition, the polarization direction of the p-polarized light in this embodiment is within the plane formed by the incident, reflected, refracted light and the normal line, and the polarization direction of the s-polarized light is perpendicular to the plane formed by the incident, reflected, refracted light and the normal line.

[0063] Specifically, when the imaging device is used for substance identification, it has the following modes:

[0064] The illumination light source is set as follows: the illumination light is a p-polarized laser, which illuminates the target object. If the intensity detected by the first detector 103 is lower than the intensity detected by the second detector 104, the target object is glass or metal; if the intensity detected by the first detector 103 is equal to the intensity detected by the second detector 104, the target object is an ordinary diffuse reflection object;

[0065] The illumination light is s-polarized laser. If the intensity detected by the first detector 103 is lower than the intensity detected by the second detector 104, the target object is glass or metal; if the intensity detected by the first detector 103 is equivalent to the intensity detected by the second detector 104, the target object is an ordinary diffuse reflection object.

[0066] The illumination light is completely non-polarized laser or sunlight. If the intensity detected by the first detector 103 is lower than that of the second detector 104, the target object is glass or metal; if the intensity detected by the first detector 103 is equivalent to that of the second detector 104, the target object is a common diffuse reflection object. Similarly, objects of known materials can be used in advance to pre-calibrate the intensity difference detected by the first detector 103 and the second detector 104. Therefore, in actual testing, the material of the target to be tested can be determined based on the intensity difference detected by the first detector 103 and the second detector 104.

[0067] In addition, in some embodiment scenarios, the first detector 103 and the second detector 104 are used to detect the p and s polarization components of the target light respectively. In this case, when the target object is a mirror-reflecting object such as glass or smooth metal, the intensity difference between the p and s polarization components in the target light is relatively large. At this time, two detectors with different sensitivities can be used to detect them separately, thereby reducing the requirements for the dynamic range of the detectors.

[0068] In summary, the above-mentioned embodiment provides a laser radar receiving system, and based on the laser radar and imaging equipment provided by the receiving system, polarization differences are used to identify materials. The receiving system includes a receiving element, a polarization beam splitting element and a first and a second detector included in the detector assembly; wherein the polarization beam splitting element is used to separate the p and s polarization components of the target object reflected light collected by the receiving element, and the two detectors are used to detect them respectively, and the polarization difference is used to realize the material identification of the target object. The structure is relatively simple, and it can be applied to laser detection and single-pixel imaging, and has a wide range of applications.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A laser radar receiving system, characterized in that: The receiving system of the laser radar includes a receiving element, a polarization beam splitting element and a detector assembly; The receiving element is used to receive the reflected light of the target to be measured, and transmit the received reflected light to the incident surface of the polarization beam splitting element; The polarization beam splitting element is used to separate the p-polarization component and the s-polarization component in the reflected light transmitted by the receiving element, and transmit them to the detector assembly; The detector assembly includes a first detector and a second detector, wherein the first detector is used to detect the p-polarization component, and the second detector is used to detect the s-polarization component.

2. The laser radar receiving system according to claim 1, characterized in that: The polarization beam splitting element is a polarization beam splitting prism or a Glan Taylor prism.

3. The laser radar receiving system according to claim 1, characterized in that: The sensitivity of the first detector is different from the sensitivity of the second detector.

4. The laser radar receiving system according to claim 1, characterized in that: The detector assembly further includes a controller, the controller is connected to a memory, and the memory stores a pre-calibrated database. The controller is used to determine the material of the target to be measured according to the difference between the p-polarization component and the s-polarization component, Or the material of the target to be measured is determined based on the comparison between the difference and the data in the pre-calibrated database.

5. A laser radar, characterized in that: The laser radar comprises a transmitting system and a receiving system as claimed in any one of claims 1 to 4, wherein the transmitting system at least comprises a laser and a deflection structure. The laser is used to emit light of a set wavelength to illuminate the target to be measured, wherein the light of the set wavelength includes light polarized in the p direction and light polarized in the s direction; The deflection structure is arranged on the optical path of the outgoing light of the laser, and is used to deflect the outgoing light of the laser so that the outgoing light of the laser can scan in a two-dimensional space.

6. The laser radar according to claim 5, characterized in that: The transmitting system further comprises a transmitting light element, which is arranged on the optical path of the output light of the deflection structure and is used to transmit the output light of the deflection structure to the target to be measured.

7. The laser radar according to claim 5 or 6, characterized in that: The deflection structure is one of a rotating multi-faceted reflection prism, a MEMS galvanometer, and a digital micromirror array; the emitting light element adopts a single lens or a lens group composed of multiple lenses.

8. An imaging device, characterized in that: The imaging device comprises an illumination light source, a light collecting system and a receiving system as claimed in any one of claims 1 to 4, The illumination light source is used to emit a laser beam in a p-polarization direction or a laser beam in an s-polarization direction to the target to be measured; The light collecting system is arranged on the optical path of the outgoing light of the polarization beam splitting element.

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