Adjusting Device and Adjusting Method for Coaxiality of Transmitting and Receiving Systems of Paraxial Lidar System

Abstract

An adjustment device and method for coaxiality of a transmitting and receiving system of a side-axis lidar system. The device includes a fixed base, an absorption-type optical attenuator, a folding structure, and a black diffuse reflection cloth. The present invention can shorten repeated adjustment steps to one adjustment, greatly improving work efficiency and the efficiency and consistency of mass production.

Description

Technical Field

[0001] The present invention relates to lidar, in particular to an adjustment device and an adjustment method for coaxial emission and reception systems of a paraxial lidar system. Background Art

[0002] According to different layouts of the emission and reception optical paths of lidar, there is a case where the emission and reception optical paths are arranged coaxially, which is called a coaxial optical system. The advantage of this optical path is that the energy of the lidar reception system is inversely proportional to the distance. The disadvantage is that the reception optical system is easily interfered by stray light from near diffuse reflection, and the emission optical path will occupy a part of the reception aperture. Correspondingly, the emission and reception optical paths are arranged on two parallel lines, and their optical axes are not coincident but parallel, which is called a paraxial optical system. This well solves the problems of interference from near stray light and the occupation of the reception optical path by the emission optical path. However, there will also be a situation where the energy of the received optical signal is very small due to the non-coincidence of the two optical axes at close range. When the lidar is dealing with some low-reflectivity targets at close range, the signal energy will be very small, and even the situation where it cannot be measured may occur. By adjusting the optical positions of emission and reception, the signal energy at close range can be adjusted to an appropriate size. However, adjusting the signal energy at close range will also affect the size of the signal energy at far range. Therefore, it is necessary to repeatedly debug many times until a position is found where the energies of the received signals at close range and far range reach a satisfactory value. This is not only cumbersome but also prone to errors, and is not suitable for mass production. Summary of the Invention

[0003] The present invention aims to solve the problem that the coaxial adjustment steps of the laser emission and reception systems of the existing paraxial lidar system are cumbersome and it is difficult to achieve a satisfactory degree of the energy of the laser received signal at both close range and relatively far range. The present invention proposes an adjustment device and an adjustment method for coaxial emission and reception systems of a paraxial lidar system, which can shorten the repeated adjustment steps to one adjustment, greatly improve the work efficiency, and improve the efficiency and consistency of mass production.

[0004] The technical solution of the present invention is as follows:

[0005] An adjustment device for coaxial emission and reception systems of a paraxial lidar system, characterized in that it includes a fixed base, an absorption-type optical attenuator, a folding structure, and a black diffuse reflection cloth. The folding structure is arranged in front of the fixed base, and this folding structure is a structure that can rotate 90 degrees perpendicular to the bottom surface of the fixed base. The absorption-type optical attenuator is fixed on this folding structure. The black diffuse reflection cloth is set as a test target far away from the fixed base, and the distance L between the black diffuse reflection cloth and the fixed base is more than 3.2 meters.

[0006] A method for adjusting the coaxiality of the transmitting system and the receiving system of a paraxial lidar system by using the adjusting device with the transmitting and receiving systems of the paraxial lidar system coaxial, the method comprising the following steps:

[0007] 1) Place and fix the paraxial lidar system to be adjusted on the fixed base, direct the detection beam of the paraxial lidar system to be adjusted towards the black diffuse reflection cloth, rotate the folding structure to move the absorption type optical attenuator out of the detection beam of the paraxial lidar system to be adjusted, and start the paraxial lidar system to be adjusted;

[0008] 2) Adjust the position of the detector of the receiving optical system of the paraxial lidar system to be adjusted to find the maximum value of the received signal energy. At this time, the fields of view of the receiving optical system and the transmitting optical system can be approximately regarded as included;

[0009] 3) If the electrical signal received by the receiving optical system of the paraxial lidar system to be adjusted is in a saturated state at this time and is not convenient to adjust, then move the optical attenuator into the detection beam through the folding structure to ensure that the cross-section of the detection beam is covered;

[0010] 4) Continue to adjust the position of the detector of the receiving optical system of the paraxial lidar system to be adjusted. When the received signal energy of the receiving optical system of the paraxial lidar system to be adjusted is the maximum value, the coaxial adjustment of the transmitting system and the receiving system of the lidar system is completed.

[0011] The working principle experiment of the present invention is as follows:

[0012] 1. First, combine the receiving optical system and the transmitting optical system into an ideal paraxial system, that is, the receiving optical path is parallel to the transmitting optical path. Since the detector of the receiving system itself cannot emit light, we use a simulated detector to simulate the light source of the detector, so that we can make the light spot on the collimator coincide with the light spot emitted by the transmitting light source on the receiving screen. At this time, the transceiver state can be considered as an ideal paraxial system.

[0013] 2. Install the ideal paraxial system on the device, then place the device on the device fixing seat, and prepare a black diffuse reflection cloth. Its function is to make the reflectivity close when incident on the target at different angles.

[0014] 3. In an ideal off-axis system, since the optical paths of the receiving optical system and the transmitting optical system do not coincide at a short distance, from the near field to the far field, the two fields of view will change from being separated to tangent, then to intersecting, and finally to being contained within each other. At a short distance, due to the separation of the fields of view of the receiving optical system and the transmitting optical system, it is difficult for the detector of the receiving system to receive the main energy reflected from the luminous optical path. When the fields of view are tangent, the detector of the receiving system can only receive partial energy reflected from the luminous optical path. Only when the receiving field of view contains the luminous field of view can the detector of the receiving system completely receive the main energy from the transmitting optical path. Therefore, the coincidence degree of the receiving and transmitting optical systems at both short and long distances can be balanced by bringing the receiving optical system and the transmitting optical system into coincidence earlier. The specific operation is to select a position much closer than the far distance as the position of infinity, place a black diffusive reflection cloth, and at this position, find the maximum value of the received signal energy by adjusting the position of the detector of the receiving system. At this time, the fields of view of the receiving optical system and the transmitting optical system can be approximately regarded as being contained within each other. Then, at a far position, there will be a slight deviation between the two fields of view, but it can be ensured that the vast majority of the part is contained within each other.

[0015] The beneficial effects of the present invention are as follows:

[0016] The present invention can simplify the coaxial adjustment steps of the laser emission and reception systems of an off-axis lidar system, enabling the received signal energy of the off-axis lidar system to reach a satisfactory level at both short and relatively long distances, and improving the efficiency and consistency of mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic structural diagram of the coaxial adjustment device for the emission and reception systems of the off-axis lidar system of the present invention, with the absorptive optical attenuator in the open state;

[0018] Figure 2 is the state where the absorptive optical attenuator is closed;

[0019] Figure 3 is a schematic diagram of the fields of view of the emission and reception systems of the off-axis lidar system of the present invention from near to far, that is, a schematic diagram of the two fields of view changing from being separated to tangent, then to intersecting, and finally to being contained within each other DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The present invention will be described in detail below with reference to the drawings and embodiments, but the protection scope of the present invention should not be limited thereby.

[0021] First, please refer to Figure 1 、 Figure 2 , Figure 1 is a schematic structural diagram of the coaxial adjustment device for the emission and reception systems of the off-axis lidar system of the present invention, with the absorptive optical attenuator in the open state; Figure 2This is the state where the absorption-type optical attenuation sheet is closed. As can be seen from the figure, the coaxial adjustment device for the transmitting and receiving systems of the side-axis lidar system of the present invention includes: a fixed base 4, an absorption-type optical attenuation sheet 3, a folding structure 2, and a black diffusive cloth 5. The folding structure 2 is arranged in front of the fixed base 4. The folding structure 2 is a structure that can rotate 90 degrees perpendicular to the bottom surface of the fixed base 4. The absorption-type optical attenuation sheet 3 is fixed on the folding structure 2. The black diffusive cloth 5 is set as a test target far away from the fixed base 4. The distance L between the black diffusive cloth 5 and the fixed base 4 is more than 3.2 meters.

[0022] The method for adjusting the coaxiality of the transmitting and receiving systems of the side-axis lidar system by using the above-mentioned coaxial adjustment device for the transmitting and receiving systems of the side-axis lidar system includes the following steps:

[0023] 1) Place and fix the side-axis lidar system 1 to be adjusted on the fixed base 4. The detection beam of the side-axis lidar system 1 to be adjusted points to the black diffusive cloth 5. Rotate the folding structure 2 to move the absorption-type optical attenuation sheet 3 out of the detection beam of the side-axis lidar system 1 to be adjusted (as Figure 1 shown), and start the side-axis lidar system 1 to be adjusted.

[0024] 2) Adjust the position of the detector of the receiving optical system of the side-axis lidar system 1 to be adjusted to find the maximum value of the received signal energy. At this time, the fields of view of the receiving optical system and the transmitting optical system can be approximately regarded as included.

[0025] 3) If the electrical signal received by the receiving optical system of the side-axis lidar system 1 to be adjusted is in a saturated state at this time and is not convenient to adjust, then move the optical attenuation sheet 3 into the detection beam through the folding structure 2 (as Figure 2 shown) to ensure that the cross-section of the detection beam is covered.

[0026] 4) Continue to adjust the position of the detector of the receiving optical system of the side-axis lidar system 1 to be adjusted. When the received signal energy of the receiving optical system of the side-axis lidar system 1 to be adjusted is the maximum value, the coaxial adjustment of the transmitting and receiving systems of the lidar system is completed.

[0027] An embodiment of the method for adjusting the coaxiality of the transmitting and receiving systems of the side-axis lidar system includes the following steps:

[0028] 1) Place and fix the side-axis lidar system 1 to be adjusted on the fixed base 4;

[0029] 2) Place the black diffuse reflection cloth 5 at a position much closer than 13 meters. The distance value of this position is generally 0.2 - 0.4 times the distance of the far position, which is set at 3.5 meters here. At this position, by adjusting the detector position of the receiving optical system of the to-be-adjusted off-axis lidar system 1, find the maximum received signal energy. At this time, the fields of view of the receiving optical system and the transmitting optical system can be approximately regarded as included (as Figure 3 shown);

[0030] 3) If the displayed electrical signal received by the receiving optical system of the to-be-adjusted off-axis lidar system 1 is in a saturated state at this time and is not convenient to adjust, then move the optical attenuation sheet into the optical path through the folding structure to ensure covering the cross-section of the optical path (as Figure 2 shown);

[0031] 4) Continue to adjust the detector position of the receiving optical system of the to-be-adjusted off-axis lidar system 1. When the received signal energy of the receiving optical system of the lidar system is the maximum, then the transmitting system and the receiving system of the to-be-adjusted off-axis lidar system 1 are coaxial.

[0032] Experiments show that the present invention can shorten the repeated adjustment steps to one adjustment, greatly improving the work efficiency and the efficiency and consistency of mass production.

Claims

1. An adjustment device for coaxiality of the transmitting and receiving systems of a paraxial lidar system, characterized in that, it includes: a fixed base (4), an absorption-type optical attenuator (3), a folding structure (2) and a black diffuse reflection cloth (5). The folding structure (2) is arranged in front of the fixed base (4). The folding structure (2) is a structure that rotates 90 degrees perpendicular to the bottom surface of the fixed base (4). The absorption-type optical attenuator (3) is fixed on the folding structure (2). The black diffuse reflection cloth (5) is set as a test target far away from the fixed base (4). The distance between the black diffuse reflection cloth (5) and the fixed base (4) is more than 3.2 meters. The implemented adjustment method includes the following steps: 1) Place and fix the paraxial lidar system (1) to be adjusted on the fixed base (4). The detection beam of the paraxial lidar system (1) to be adjusted points to the black diffuse reflection cloth (5). Move the absorption-type optical attenuator (3) out of the detection beam of the paraxial lidar system (1) to be adjusted by rotating the folding structure (2), and start the paraxial lidar system to be adjusted; 2) Adjust the position of the detector of the receiving optical system of the paraxial lidar system (1) to be adjusted to find the maximum value of the received signal energy. At this time, the fields of view of the receiving optical system and the transmitting optical system can be approximately regarded as included; 3) If the electrical signal received by the receiving optical system of the paraxial lidar system (1) to be adjusted is in a saturated state at this time and is not convenient to adjust, then move the optical attenuator (3) into the detection beam through the folding structure (2) to ensure covering the cross-section of the detection beam; 4) Continue to adjust the position of the detector of the receiving optical system of the paraxial lidar system (1) to be adjusted. When the received signal energy of the receiving optical system of the paraxial lidar system (1) to be adjusted is the maximum value, the coaxial adjustment of the transmitting system and the receiving system of the lidar system is completed.

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