Laser ranging echo receiving device and laser ranging method

Abstract

This invention discloses a laser ranging echo receiving device and a laser ranging method. The device includes a focusing lens, a main detector, and a secondary detector. The focusing lens refracts and converges the laser echo reflected from the target, which includes targets with general reflectivity and targets with extremely high reflectivity. The main detector, located at the rear focal point of the focusing lens, outputs a ranging response value based on the received laser echo to measure the distance to targets with general reflectivity. The secondary detector, located on the same focal plane as the main detector, outputs a ranging response value based on the received laser echo when the main detector is in a receiving saturation state, to measure the distance to targets with extremely high reflectivity. This embodiment solves the problem in existing laser ranging technologies that cannot accurately measure the distance to targets with extremely high reflectivity such as retroreflectors. Furthermore, it uses fewer optical components, is smaller and lighter, and is easier to debug.

Description

Technical Field

[0001] This invention relates to the field of laser ranging technology, and in particular to a laser ranging echo receiving device and a laser ranging method. Background Technology

[0002] For lidar that uses the time-of-flight method for ranging, a laser source emits laser pulses that illuminate the surface of the target within the detector's response range. The reflected laser pulses from the target are received by the detector, and the distance to the target is calculated by the time interval between the emitted and received pulses.

[0003] When using lidar for road surveying, two different types of reflective objects are generally detected: the first type is conventional diffuse reflectors, such as walls, trees, soil, roads, and most man-made or natural features; the second type is retroreflectors, such as road traffic signs. Retroreflectors can cause reflected light to return from near the direction of the incident light over a wide angle range, thus exhibiting a high reflectivity. Different diffuse reflective targets have varying reflectivity, and different levels of roads use different retroreflective materials with varying retroreflectivity coefficients. Generally, traffic signs on ordinary roads use high-intensity materials, while traffic signs on highways use ultra-high-intensity materials. The retroreflectivity coefficient of traffic signs can be considered to be between approximately 250 and 500. The retroreflectivity coefficient of other targets around the road is generally lower, similar to that of fabrics and walls, approximately between 0.2 and 2. In other words, the reflectivity of retroreflectors around the road is approximately several hundred to several thousand times that of diffuse reflectors.

[0004] When a lidar pulse scans a retroreflector, if the reflectivity of the target is too high and the echo energy is too strong, it can cause saturation in the detector's sampling circuit. Related experiments have shown that pulse response saturation is due to the lifetime of photogenerated carriers. Slow carrier release causes small-signal carriers incident during the carrier's lifetime (i.e., for a period after saturation occurs) to be submerged in the saturation response, and the duration of detector saturation increases with the incident light energy.

[0005] Because laser ranging based on the time-of-flight principle calculates target distance by comparing the time difference between the initial pulse peak and the echo pulse peak, detector saturation makes it impossible to determine the arrival time of the echo pulse peak, thus preventing the calculation of the target distance. Furthermore, excessively strong echo energy can cause circuit oscillations. After the saturation peak, a series of oscillating peaks appear. These oscillating peaks do not exceed the saturation value and behave similarly to normal echoes, thus failing to filter and generating a series of false alarm noise.

[0006] In practical applications, a basic laser ranging and receiving system typically consists of a focusing lens and a detector. Figure 1a This is a schematic diagram illustrating the principle of laser ranging in existing technology. Figure 1b This is a schematic diagram of the first data acquisition method in existing laser ranging technology. Figure 1c This is a schematic diagram of the second type of data acquisition in existing laser ranging technology. Figure 1d This is a schematic diagram of the third type of data acquisition in existing laser ranging technology. For example... Figure 1a As shown, under normal circumstances, the focusing lens in a laser ranging echo receiver focuses the parallel light reflected from the target onto the photosensitive element of the detector. The detector then outputs a response value, and the back-end circuitry and algorithm compare the peak times of transmission and reception to calculate the distance to the target. In a non-saturated receiving state, the laser ranging receiver system acquires a ranging waveform as shown... Figure 1b As shown; when a laser ranging receiver system receives a ranging echo returned from a target with extremely high reflectivity, it may enter a receiving saturation state, and the acquired ranging waveform will be as follows. Figure 1c As shown; after the saturation peak, a series of oscillating peaks may appear, with waveforms as follows. Figure 1d As shown.

[0007] Therefore, when a basic laser ranging device illuminates a highly reflective object during the ranging process, it is prone to detector saturation, resulting in ranging abnormalities. Figure 1e This is a schematic diagram illustrating the principle of another laser ranging technology in the prior art, such as... Figure 1e As shown, a second focusing lens 2 is added after the focusing lens 1 that receives the laser echo beam to collimate the beam. The collimated beam then passes through a beam splitter, with a main detector and a secondary detector positioned at the reflecting and transmitting ends of the beam splitter, respectively. Based on the ratio of reflectivity between highly reflective targets and ordinary targets, the reflection-to-transmission ratio of the beam splitter is adjusted so that the beam energy entering the secondary detector is only a fraction of the energy entering the main detector. When the laser rangefinder scans a target with extremely high reflectivity, the main detector will saturate due to receiving excessively strong reflected signals, while the energy received by the secondary detector will be within its normal response range. However, this laser ranging receiver has a complex structure, requires many optical components, is costly, and is large in size and weight. After the echo beam is focused, it needs to be split into two optical paths. The detectors on the two optical paths need to be focused and adjusted separately. The adjustment process is complicated and the efficiency is low. Furthermore, since a portion of the energy originally incident on the main detector needs to be diverted to the secondary detector, some of the weaker echoes from distant targets that the main detector could originally respond to are no longer detected because some of the energy has been separated, resulting in a loss of ranging capability. Summary of the Invention

[0008] This invention provides a laser ranging echo receiving device and a laser ranging method to achieve accurate ranging of targets with ultra-high reflectivity using simple optical path elements.

[0009] According to one aspect of the present invention, a laser ranging echo receiving device is provided, the device comprising a focusing lens, a main detector and a secondary detector;

[0010] The focusing lens is used to refract and converge the laser echo reflected by the target under test, wherein the target under test includes general reflectivity targets and ultra-high reflectivity targets;

[0011] The main detector is positioned at the rear focal point of the focusing lens and is used to output the main detector ranging response value based on the received laser echo, so as to realize the distance measurement of the general reflectivity target.

[0012] The secondary detector, which is located on the same focal plane as the primary detector, is used to output the ranging response value of the secondary detector based on the received laser echo when the primary detector is in a receiving saturation state, so as to realize the distance measurement of the ultra-high reflectivity target.

[0013] Optionally, the secondary detector is positioned at the Airy disk bright ring corresponding to the focusing lens, and the number of Airy disk bright rings is determined based on the reflectivity of the ultra-high reflectivity target and the magnification of the secondary detector.

[0014] Optionally, the focusing lens includes a first light-transmitting region and a second light-transmitting region;

[0015] The light-transmitting area of ​​the first light-transmitting region is larger than that of the second light-transmitting region, and the diameter of the second light-transmitting region is determined based on the diameter of the focusing lens and the reflectivity of the ultra-high reflectivity target.

[0016] The optical axis of the first light-transmitting region is collinear with the optical axis of the focusing lens, and the optical axis of the second light-transmitting region is parallel to the optical axis of the first light-transmitting region.

[0017] The back focal length of the first light-transmitting region is the same as that of the second light-transmitting region.

[0018] Optionally, the main detector is located at the rear focal position of the first light-transmitting area;

[0019] The secondary detector is located at the rear focal position of the second light-transmitting region.

[0020] Optionally, the device further includes: a cylindrical wedge prism;

[0021] The cylindrical wedge prism is coaxially arranged with the focusing lens and is located on the light-inlet side of the focusing lens;

[0022] The light-transmitting area of ​​the cylindrical wedge prism is smaller than that of the focusing lens, and the diameter of the cylindrical wedge prism is determined based on the diameter of the focusing lens and the reflectivity of the ultra-high reflectivity target.

[0023] Optionally, the main detector is located at the rear focal point of the first outer ring beam of the focusing lens, and the first outer ring beam is a beam that enters the focusing lens without being refracted by the cylindrical wedge prism;

[0024] The sub-detector is located at the rear focal point of the first inner ring beam of the focusing lens, which is a beam that has been refracted by the cylindrical wedge prism before entering the focusing lens.

[0025] Optionally, the device further includes: an annular hollow wedge prism;

[0026] The annular hollow wedge prism is coaxially arranged with the focusing lens and is located on the light-inlet surface side of the focusing lens;

[0027] The light-transmitting area of ​​the annular hollow wedge prism is smaller than that of the focusing lens. The outer diameter of the annular hollow wedge prism is equal to that of the focusing lens. The ring width of the annular hollow wedge prism is determined based on the diameter of the focusing lens and the reflectivity of the ultra-high reflectivity target.

[0028] Optionally, the main detector is located at the rear focal point of the second inner ring beam of the focusing lens, and the second inner ring beam is a beam that enters the focusing lens without being refracted by the annular hollow wedge prism;

[0029] The sub-detector is located at the rear focal point of the second outer ring beam of the focusing lens, which is a beam that enters the focusing lens after being refracted by the annular hollow wedge prism.

[0030] Optionally, the main detector includes a main photosensitive surface, the secondary detector includes a secondary photosensitive surface, and the main photosensitive surface and the secondary photosensitive surface are encapsulated in a detector housing.

[0031] According to another aspect of the present invention, a laser ranging method is provided, employing the laser ranging echo receiving device described in the first aspect, the method comprising:

[0032] When the main detector is in a state of receiving saturation, the range response value of the secondary detector is output based on the received laser echo to achieve distance measurement of targets with extremely high reflectivity; otherwise,

[0033] The main detector outputs a ranging response value based on the received laser echo to achieve distance measurement of targets with general reflectivity.

[0034] The technical solution of this invention, through the design of a laser ranging echo receiving device including a focusing lens, a main detector, and a secondary detector, wherein the focusing lens is used to refract and converge the laser echo reflected by the target to be measured, including targets with general reflectivity and targets with ultra-high reflectivity; the main detector is set at the rear focal point of the focusing lens, and is used to output the ranging response value of the main detector according to the received laser echo, so as to realize the distance measurement of targets with general reflectivity; the secondary detector is set on the same focal plane as the main detector, and is used to output the ranging response value of the secondary detector according to the received laser echo when the main detector is in the receiving saturation state, so as to realize the distance measurement of targets with ultra-high reflectivity. This solves the problem that existing laser ranging technology cannot accurately measure the distance of targets with ultra-high reflectivity. It not only uses fewer optical path components, but also has low cost, small size and weight. Furthermore, since the echo beam focused by the same focusing lens enters the two detectors, and the two detectors are on the same focal plane, only one focusing operation is needed to complete the focusing requirements of the two detectors simultaneously, and the debugging steps are simple.

[0035] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1a This is a schematic diagram illustrating the principle of laser ranging in existing technology;

[0038] Figure 1b This is a schematic diagram of the first data acquisition method in existing laser ranging technology;

[0039] Figure 1c This is a schematic diagram of the second type of data acquisition in existing laser ranging technology;

[0040] Figure 1d This is a schematic diagram of the third type of data acquisition in existing laser ranging technology;

[0041] Figure 1e This is a schematic diagram illustrating the principle of another laser ranging technology in the prior art;

[0042] Figure 2 This is a schematic diagram of the structure of a laser ranging echo receiving device provided in an embodiment of the present invention;

[0043] Figure 3 This is a statistical chart of detector position debugging data of a laser ranging echo receiving device provided in an embodiment of the present invention;

[0044] Figure 4 This is a schematic diagram illustrating the detector position setting principle of a laser ranging echo receiving device provided in an embodiment of the present invention;

[0045] Figure 5a This is a schematic diagram of the first structure of the focusing lens in a laser ranging echo receiving device provided in an embodiment of the present invention;

[0046] Figure 5b This is a schematic diagram of the second structure of the focusing lens in a laser ranging echo receiving device provided in an embodiment of the present invention;

[0047] Figure 5c This is a schematic diagram of the first echo receiving principle of a laser ranging echo receiving device provided in an embodiment of the present invention;

[0048] Figure 5d This is a schematic diagram of the first echo reception effect of a laser ranging echo receiving device provided in an embodiment of the present invention;

[0049] Figure 6a This is a schematic diagram of the second echo receiving principle of a laser ranging echo receiving device including a cylindrical wedge prism provided in an embodiment of the present invention;

[0050] Figure 6b This is a schematic diagram of the second echo reception effect of a laser ranging echo receiving device including a cylindrical wedge prism provided in an embodiment of the present invention;

[0051] Figure 7a This is a schematic diagram of the structure of the annular hollow wedge prism in a laser ranging echo receiving device provided in an embodiment of the present invention;

[0052] Figure 7b This is a schematic diagram of the third echo reception effect of a laser ranging echo receiving device including a ring-shaped hollow wedge prism provided in an embodiment of the present invention;

[0053] Figure 8a This is a schematic diagram of the detector structure in a laser ranging echo receiving device provided in an embodiment of the present invention;

[0054] Figure 8b This is a schematic diagram of the detector effect in a laser ranging echo receiving device provided in an embodiment of the present invention;

[0055] Figure 8c This is a schematic diagram of the fourth echo reception effect of a laser ranging echo receiving device provided in an embodiment of the present invention;

[0056] Figure 8d This is a schematic diagram of the fifth echo reception effect of a laser ranging echo receiving device provided in an embodiment of the present invention;

[0057] Figure 9 This is a schematic flowchart of a laser ranging method provided in an embodiment of the present invention. Detailed Implementation

[0058] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0059] It should be noted that the terms "first," "second," "target," etc., used in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0060] Example 1

[0061] Figure 2 This is a schematic diagram of a laser ranging echo receiving device provided in Embodiment 1 of the present invention. This laser ranging echo receiving device can be configured in a laser rangefinder. Figure 2 As shown, the device may include a focusing mirror 10, a main detector 20, and a secondary detector 30.

[0062] The focusing lens 10 can be used to refract and converge the laser echo reflected by the target under test, which includes targets with general reflectivity and targets with ultra-high reflectivity.

[0063] The main detector 20 can be set at the rear focal point of the focusing lens 10 to output the range response value of the main detector based on the received laser echo, so as to realize the distance measurement of targets with general reflectivity.

[0064] The secondary detector 30 can be set on the same focal plane as the main detector 20. When the main detector 20 is in a receiving saturation state, it outputs the ranging response value of the secondary detector based on the received laser echo, so as to realize the distance measurement of the ultra-high reflectivity target.

[0065] Generally, a target with low reflectivity can be understood as a target to be measured, which can include common diffuse reflectors such as walls, trees, soil, and roads, with retroreflectivity mostly between 0.2 and 2. A target with very high reflectivity can be understood as a target to be measured with high reflectivity, typically a retroreflector, such as road traffic signs made of high-strength or ultra-high-strength materials, with retroreflectivity mostly between 250 and 500.

[0066] In practical applications, when using a laser rangefinder for distance measurement, a laser pulse is emitted from the laser source in the rangefinder and irradiates the surface of the target. The laser rangefinder's laser range echo receiver receives the laser echo reflected from the target and outputs a distance response value, thereby calculating the distance to the target. In this embodiment, the focusing lens 10 in the laser range echo receiver can refract and converge the laser echo reflected from the target, as shown in Figure 1. The focusing lens 10 can be a convex mirror.

[0067] Specifically, for the optical path system of a laser rangefinder, the position of the target relative to the size of the optical path system can be considered as the far field, and the laser echo beam can also be approximated as parallel light. Therefore, the energy distribution of the cross-section of the light spot after being focused by the focusing lens generally exhibits a Gaussian distribution. The focusing lens in the echo receiving system of laser rangefinders such as lidar is generally circular, a naturally existing circular aperture. In practice, when the parallel beam passes through the circular aperture, Fraunhofer circular aperture diffraction occurs, forming an Airy disk. Approximately 84% of the light energy is concentrated in the central bright spot of the Airy disk, while the remaining approximately 16% of the light energy is distributed on the bright rings of the Airy disk at various levels.

[0068] In this embodiment, the main detector 20 can be positioned at the rear focal point of the focusing lens 10, which corresponds to the central bright spot of the Airy disk. For ranging in most scenarios, placing the main detector 20 at the energy center position maximizes the utilization of laser energy to achieve the longest possible ranging effect. The main detector 20 can output a ranging response value based on the received laser echo to achieve distance measurement for targets with general reflectivity.

[0069] However, when ranging targets with extremely high reflectivity, the main detector 20 may experience signal saturation due to the high reflectivity of the target, thus affecting the ranging. In this embodiment, the secondary detector 30 is positioned on the same focal plane as the main detector 20. When a target with extremely high reflectivity is detected, and the main detector 20 is in a state of receiving saturation, the low energy at the edge of the Airy disk can be utilized to prevent the secondary detector 30 from saturating when receiving the echo from the target. The secondary detector then outputs a ranging response value based on the received laser echo, thereby achieving distance measurement of the target with extremely high reflectivity. The detector in this embodiment can be a common device such as an APD (Avalanche Photo Diode), a SPAD (Single Photon Avalanche Diode), or a SiPM (Silicon Photomultiplier).

[0070] The laser ranging echo receiver provided in this embodiment has a more streamlined structure compared to existing technologies, reducing the overall weight and assembly difficulty. Furthermore, since the laser echo beams received by the main and secondary detectors are focused by the same focusing lens, and both detectors are on the same focal plane, installation and debugging difficulties are significantly reduced, improving efficiency. During manufacturing, it is only necessary to pre-install the two detectors on a single plane and pre-define the distance between them according to the ranging and circuit processing requirements. Then, as a single component, the main detector within this component is focused and adjusted to the focusing lens; separate focusing and adjustment of each detector is not required. Because the secondary detector utilizes a portion of the energy not received or utilized by the main detector, rather than separating energy from the energy originally received by the main detector, the laser rangefinder using this embodiment does not lose its ranging capability.

[0071] The focusing and adjustment process of the laser ranging echo receiver provided in this embodiment can be as follows:

[0072] 1) Determine the measurement distance range L1 to L2 for the ultra-high reflectivity target to be measured;

[0073] 2) Place the ultra-high reflectivity target at a certain position within the measurement range and measure its distance;

[0074] 3) Set the main detector to the back focal point of the focusing lens, and adjust the secondary detector to be near the main detector and on the same focal plane as the main detector. At this time, the detector should be in a state of signal reception saturation at the back focal point. Gradually move the secondary detector from the center region of the Airy disk to the edge of the Airy disk. At this time, the secondary detector will slowly return from the saturation state to the normal response range.

[0075] 4) Determine the appropriate position D of the secondary detector based on the echo signal strength required by the processing circuit;

[0076] 5) Move the position of the ultra-high reflectivity target within the measurement range L1 to L2 and observe whether the sub-detectors can respond normally.

[0077] 6) If the sub-detector saturates when the ultra-high reflectivity target moves to certain positions, continue moving the sub-detector away from the center of the Airy disk; if the sub-detector becomes unresponsive when the ultra-high reflectivity target moves to certain positions, move the sub-detector closer to the center of the Airy disk.

[0078] 7) If the secondary detector cannot be placed in a suitable location due to spatial constraints, it can be placed nearby, and the effect can be achieved by adjusting the magnification: if the secondary detector saturates when the ultra-high reflectivity target moves to a certain position, the magnification should be reduced; if the secondary detector does not respond when the ultra-high reflectivity target moves to a certain position, the magnification should be increased, thereby determining the magnification n. Generally, adjusting the magnification can be achieved by adding an attenuator or aperture in front of the detector to achieve the same effect. These are conventional techniques in this field and will not be elaborated upon here.

[0079] In practical applications, the main detector and the secondary detector acquire signals simultaneously. Since the secondary detector's receiving capability is primarily tuned for high-reflectivity targets, under normal circumstances, its reception of echoes from diffuse reflective targets will be very weak and filtered out. In this case, the ranging information from the main detector is used. However, when the main detector experiences high-reflectivity saturation, the secondary detector, being within its response range, will have its main detector signal filtered out due to reception saturation, and the ranging information from the secondary detector will be used. Therefore, the ranging system optimized by the above focusing and tuning scheme can avoid high-reflectivity saturation within the L1-L2 range and complete the measurement.

[0080] For example, the light source wavelength of the laser ranging optical path system is 1550nm, the diameter of the receiving focusing lens is 50mm, and the back focal length is 40mm. The detector is placed on the focal plane of the focusing lens and moved from the positive focal point to the edge region. The energy intensity fluctuation of the light spot outside the central bright spot of the Airy disk can be observed from the response value of the detector. Figure 3This is a statistical chart of detector position debugging data for a laser ranging echo receiving device provided in Embodiment 1 of the present invention, as shown in the figure. Figure 3 As shown, three channels were used to observe this phenomenon. The magnification difference between the three channels is approximately 12x. Channel 1 has the base magnification, channel 2 has 12x magnification, and channel 3 has 144x magnification. Figure 3 As can be seen in this embodiment, for a laser ranging system with a 1550nm laser light source, a 50mm diameter receiving aperture, and a 40mm back focal length, a secondary detector can be placed 1mm away from the center of the focal point. This detector has a magnification of 12 times, and at this time, it has a good detection effect on highly reflective objects in the range of 4m to 10m.

[0081] The technical solution of this embodiment only adds one auxiliary detector in terms of structure. It has fewer optical path components, lower cost, smaller size and lighter weight. Since the laser echo beam focused by the same focusing lens enters the two detectors, only one focusing operation is needed to make the two detectors focus at the same time. After the laser echo beam is focused, no other optical path processing is performed. Instead, the energy distribution characteristics of the beam itself are used to distribute the echo energy received by the two detectors, so that the response ranges of the two detectors can be staggered. This not only does not lose the ranging capability, but also avoids the detector saturation and abnormal ranging information caused by irradiating ultra-high reflectivity targets.

[0082] In one embodiment, the sub-detector 20 is positioned at the Airy disk bright ring corresponding to the focusing lens 10, and the number of Airy disk bright rings is determined based on the reflectivity of the ultra-high reflectivity target and the magnification of the sub-detector.

[0083] Figure 4 This is a schematic diagram illustrating the detector position setting principle of a laser ranging echo receiving device according to an embodiment of the present invention. Figure 4 As shown in the figure, the curves in the figure can represent the energy values ​​at various locations within the Airy disk region. The main detector 20 can be set at the position of the bright spot in the center of the Airy disk, and the secondary detector 30 can be set at the first bright ring of the Airy disk, that is, at the first energy peak outside the bright spot in the center of the Airy disk.

[0084] In one embodiment, the focusing lens 10 may include a first light-transmitting region 11 and a second light-transmitting region 12; the light-transmitting area of ​​the first light-transmitting region 11 is larger than the light-transmitting area of ​​the second light-transmitting region 12, and the diameter of the second light-transmitting region 12 is determined according to the diameter of the focusing lens and the reflectivity of the ultra-high reflectivity target; the optical axis of the first light-transmitting region 11 is collinear with the optical axis of the focusing lens 10, and the optical axis of the second light-transmitting region 12 is parallel to the optical axis of the first light-transmitting region 11; the back focal length of the first light-transmitting region 11 is the same as the back focal length of the second light-transmitting region 12.

[0085] Correspondingly, the main detector 20 can be located at the rear focal position of the first light-transmitting region 11; the secondary detector 30 can be located at the rear focal position of the second light-transmitting region 12.

[0086] Figure 5a This is a schematic diagram of the first structure of the focusing lens in a laser ranging echo receiving device provided in an embodiment of the present invention. Figure 5b This is a front view of the focusing lens's light-transmitting surface in a laser ranging echo receiving device provided in an embodiment of the present invention. Figure 5c This is a schematic diagram of the first echo receiving principle of a laser ranging echo receiving device provided in an embodiment of the present invention. Figure 5d This is a schematic diagram of the first echo reception effect of a laser ranging echo receiving device provided in an embodiment of the present invention. As shown in the figure, the focusing lens 10 in this embodiment can be a freeform lens, which can separate the laser echo beam into two focal points, which are then incident on two detectors respectively. The focusing lens 10 can be divided into two light-transmitting regions from the axial direction: a first light-transmitting region 11 and a second light-transmitting region 12. The second light-transmitting region 12 can also be a focusing lens, with its optical axis parallel to the optical axis of the first light-transmitting region 11 and its back focal length consistent with that of the first light-transmitting region 11. This allows for two focal points to be obtained on a single focal plane. A detector is arranged at each of the two focal points. In this embodiment, the main detector 20 is arranged at focal point position 1, i.e., the back focal point position of the first light-transmitting region 11; and the secondary detector 30 is arranged at focal point position 2, i.e., the back focal point position of the second light-transmitting region 12. The ratio of the energy received by the two detectors is the ratio of the light-transmitting areas of the two regions. For example, using the retroreflection coefficient of an ultra-high reflectivity target (approximately 400 times that of a typical reflectivity target) as a benchmark, and with a focusing lens outer diameter of 50 mm, the diameter d of the second light-transmitting region 12 can be designed as follows: If d≈2.5mm, then the ratio of the received energy of the main detector 20 and the secondary detector 30 for the same target reflected light wave is about 400. When a high reflectivity target is detected, the main detector 20 is saturated, while the secondary detector 30 is exactly in the corresponding signal receiving range, which means that the distance detection of ultra-high reflectivity targets can be realized.

[0087] Since the positions of the two focal points of the freeform surface focusing lens are known and controllable, the distance between the two focal points can be denoted as d1. During manufacturing, it is only necessary to pre-install the two detectors on a plane, with the distance d2 between the two detectors set to the aforementioned distance d1. Then, as a single component, the main detector in this component is focused and adjusted to the focal point of the first light-transmitting area of ​​the focusing lens. It is not necessary to focus and adjust the two detectors separately, which reduces the difficulty of installation and adjustment and improves efficiency.

[0088] In this embodiment, the laser ranging echo receiver simultaneously acquires signals from both the main detector and the secondary detector during continuous ranging. Since the secondary detector's receiving capability is primarily tuned for ultra-high reflectivity targets, its reception of echo information from targets with generally low reflectivity is weak under normal circumstances and is filtered out. In this case, the ranging information from the main detector is used. However, when the main detector experiences high reflectivity saturation, the secondary detector, being within its response range, receives the signal from the main detector, which is then filtered out due to saturation, and the ranging information from the secondary detector is used. In this embodiment, the position of the secondary detector does not require response value adjustment based on the ranging range, simplifying the adjustment process and increasing efficiency. Furthermore, the position of the secondary detector is determined by the surface design of the second light-transmitting area of ​​the freeform focusing lens, allowing for more flexible spacing between it and the main detector. This flexibility is not limited by the energy distribution or area of ​​the beam itself, resulting in a wider range of applications.

[0089] In one embodiment, the laser ranging echo receiving device provided in this embodiment may include a focusing lens 10, a main detector 20, a secondary detector 30, and a cylindrical wedge prism 40.

[0090] The cylindrical wedge prism 40 can be coaxially arranged with the focusing lens 10 and located on the light-inlet side of the focusing lens 10; the light-transmitting area of ​​the cylindrical wedge prism 40 is smaller than the light-transmitting area of ​​the focusing lens 10, and the diameter of the cylindrical wedge prism 40 can be determined according to the diameter of the focusing lens 10 and the reflectivity of the ultra-high reflectivity target.

[0091] Correspondingly, the main detector 20 can be located at the rear focal point of the first outer ring beam of the focusing lens 10, which is a beam that enters the focusing lens 10 without being refracted by the cylindrical wedge prism 40; the secondary detector 30 is located at the rear focal point of the first inner ring beam of the focusing lens, which is a beam that enters the focusing lens 10 after being refracted by the cylindrical wedge prism 40.

[0092] Figure 6a This is a schematic diagram illustrating the second echo receiving principle of a laser ranging echo receiving device including a cylindrical wedge prism, provided in an embodiment of the present invention. Figure 6b This is a schematic diagram illustrating the second echo reception effect of a laser ranging echo receiving device including a cylindrical wedge prism provided in an embodiment of the present invention. Figure 6a and Figure 6bAs shown, the technical solution of this embodiment adds a cylindrical wedge prism 40 in front of the focusing lens 10. The function of the cylindrical wedge prism 40 is to deflect the laser echo beam in the central part by a certain amount, so that it enters the sub-detector 30, while the echo beam passing through the part smaller than the diameter of the focusing lens 10 but larger than the diameter of the cylindrical wedge prism 40 enters the main detector 20. During use, the diameter of the cylindrical wedge prism 40 can be adjusted according to actual needs to distribute the energy ratio of the echoes entering the main detector 20 and the sub-detector 30. For example, based on the retroreflection coefficient of an ultra-high reflectivity target being approximately 400 times that of a normal reflectivity target, and with the outer diameter of the focusing lens 10 being 50 mm, the diameter d of the cylindrical wedge prism 40 can be designed as follows: If d≈2.5mm, then the ratio of the received energy of the main detector 20 and the secondary detector 30 for the same target reflected light wave is about 400. When a high reflectivity target is detected, the main detector 20 is saturated, while the secondary detector 30 is exactly within the corresponding signal receiving range, which means that the distance detection of ultra-high reflectivity targets can be achieved.

[0093] Since the angle at which the cylindrical wedge prism 40 deflects the beam is known and controllable, the distance d1 between the back focal point of the first inner ring beam and the back focal point of the first outer ring beam can be calculated based on the selected angle of the cylindrical wedge prism 40. During manufacturing, it is only necessary to pre-install the two detectors onto a focal plane, with the distance d2 between the two detectors set to the aforementioned distance d1. Then, as a single assembly, the main detector 20 and the focusing lens 10 in this assembly can be focused and adjusted; separate focusing and adjustment of the two detectors is not required. Furthermore, in general applications, the cylindrical wedge prism 40 and the focusing lens 10 can be coaxially arranged and installed, posing minimal difficulties for machining and assembly.

[0094] In this embodiment, the laser ranging echo receiver simultaneously acquires signals from both the main detector and the secondary detector during continuous ranging. Since the secondary detector's receiving capability is primarily tuned for ultra-high reflectivity targets, its reception of echo information from targets with generally low reflectivity is weak under normal circumstances and is filtered out. In this case, the ranging information from the main detector is used. However, when the main detector experiences high reflectivity saturation, the secondary detector, being within its response range, receives the signal from the main detector, which is then filtered out due to saturation, and the ranging information from the secondary detector is used. This embodiment of the laser ranging echo receiver offers better overall manufacturability, lower processing difficulty, and lower overall cost. Furthermore, the position of the secondary detector is determined by the deflection angle of the cylindrical wedge prism, allowing for more flexible spacing between it and the main detector. This arrangement is not limited by the energy distribution or region of the beam itself, resulting in a simple and efficient debugging process and a wider range of applications.

[0095] In one embodiment, the laser ranging echo receiving device provided in this embodiment may include a focusing lens 10, a main detector 20, a secondary detector 30, and an annular hollow wedge prism 50.

[0096] The annular hollow wedge prism 50 can be coaxially arranged with the focusing lens 10 and located on the light-incoming surface side of the focusing lens 10; the light-transmitting area of ​​the annular hollow wedge prism 50 is smaller than that of the focusing lens 10, the outer diameter of the annular hollow wedge prism 50 is equal to that of the focusing lens 10, and the ring width of the annular hollow wedge prism 50 can be determined according to the diameter of the focusing lens 10 and the reflectivity of the ultra-high reflectivity target.

[0097] Correspondingly, the main detector 20 is located at the rear focal point of the second inner ring beam of the focusing lens 10, which is a beam that enters the focusing lens 10 without being refracted by the annular hollow wedge prism 50; the auxiliary detector 30 is located at the rear focal point of the second outer ring beam of the focusing lens 10, which is a beam that enters the focusing lens 10 after being refracted by the annular hollow wedge prism 50.

[0098] Figure 7a This is a schematic diagram of the structure of a ring-shaped hollow wedge prism in a laser ranging echo receiving device provided in an embodiment of the present invention, as shown below. Figure 7a As shown in the figure, (1) is a three-dimensional view of the annular hollow wedge prism 50, (2) is a side view of the annular hollow wedge prism 50, and (3) is a front view of the light-gathering surface of the annular hollow wedge prism 50. Figure 7b This is a schematic diagram of the third echo reception effect of a laser ranging echo receiving device including a ring-shaped hollow wedge prism provided in an embodiment of the present invention, as shown in the figure. Figure 7b As shown, the outer diameter of the annular hollow wedge prism 50 can be equal to the outer diameter of the focusing lens 10, which allows the annular hollow wedge prism 50 and the focusing lens 10 to share the same inner wall of the hole for assembly, resulting in a simpler structure and higher coaxiality.

[0099] In one embodiment, the laser ranging echo receiver provided in this embodiment includes a main detector including a main photosensitive surface and a secondary detector including a secondary photosensitive surface. The main photosensitive surface and the secondary photosensitive surface can be encapsulated in a detector housing.

[0100] In practical applications, the two detectors in all the above embodiments can be encapsulated in a single detector housing. Figure 8a This is a schematic diagram of the detector structure in a laser ranging echo receiving device provided in an embodiment of the present invention. Figure 8b This is a schematic diagram of the detector in a laser ranging echo receiving device according to an embodiment of the present invention. As shown in the figure, the detector mainly includes a photosensitive surface, which can be common photosensitive materials such as SPAD, APD, and SiPM. The detector housing can include a base, a cover, and a window. Figure 8aThis is a schematic diagram of the structure of the two detectors before and after encapsulation. Figure 8b This is a schematic diagram showing the effect of the two detectors before and after encapsulation. Figure 8c This is a schematic diagram of the fourth echo reception effect of a laser ranging echo receiving device provided in an embodiment of the present invention; Figure 8d This is a schematic diagram of the fifth echo reception effect of a laser ranging echo receiving device provided in an embodiment of the present invention. As shown in the figure, encapsulating the two detectors in a single detector housing makes the laser ranging echo receiving device more compact, lighter, and easier to install and debug.

[0101] Example 2

[0102] This embodiment is applicable to laser ranging. The method can be performed by a laser rangefinder, which can be any of the laser ranging echo receiving devices described in Embodiment 1 of this invention. Figure 9 This is a schematic flowchart of a laser ranging method provided in an embodiment of the present invention, as shown below. Figure 9 As shown, the method may include:

[0103] S110. When the main detector is in a receiving saturation state, the range response value of the secondary detector is output according to the received laser echo to realize the distance measurement of the ultra-high reflectivity target.

[0104] S120. When the main detector is in a non-saturated receiving state, the main detector outputs the ranging response value based on the received laser echo to realize the distance measurement of targets with general reflectivity.

[0105] In this embodiment, the laser ranging echo receiving device in the laser ranging method is any one of the laser ranging echo receiving devices in Embodiment 1 of the present invention.

[0106] This invention utilizes the energy distribution characteristics of the light beam itself to distribute the echo energy received by the two detectors, allowing the response ranges of the two detectors to be staggered. This not only does not result in a loss of ranging capability, but also avoids detector saturation and abnormal ranging information caused by irradiating targets with extremely high reflectivity.

[0107] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0108] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A laser ranging echo receiving device, characterized in that, Includes a focusing mirror, a main detector, and a secondary detector; The focusing lens is used to refract and converge the laser echo reflected by the target under test, wherein the target under test includes general reflectivity targets and ultra-high reflectivity targets; The main detector is positioned at the rear focal point of the focusing lens and is used to output the main detector ranging response value based on the received laser echo, so as to realize the distance measurement of the general reflectivity target. The secondary detector, which is located on the same focal plane as the primary detector, is used to output the ranging response value of the secondary detector based on the received laser echo when the primary detector is in a receiving saturation state, so as to realize the distance measurement of the ultra-high reflectivity target.

2. The apparatus according to claim 1, characterized in that, The secondary detector is positioned at the bright ring of the Airy disk corresponding to the focusing lens, and the number of levels of the bright ring is determined based on the reflectivity of the ultra-high reflectivity target and the magnification of the secondary detector.

3. The apparatus according to claim 1, characterized in that, The focusing lens includes a first light-transmitting region and a second light-transmitting region; The light-transmitting area of ​​the first light-transmitting region is larger than that of the second light-transmitting region, and the diameter of the second light-transmitting region is determined based on the diameter of the focusing lens and the reflectivity of the ultra-high reflectivity target. The optical axis of the first light-transmitting region is collinear with the optical axis of the focusing lens, and the optical axis of the second light-transmitting region is parallel to the optical axis of the first light-transmitting region. The back focal length of the first light-transmitting region is the same as that of the second light-transmitting region.

4. The apparatus according to claim 3, characterized in that, The main detector is located at the rear focal position of the first light-transmitting area; The secondary detector is located at the rear focal position of the second light-transmitting region.

5. The apparatus according to claim 1, characterized in that, The device further includes: a cylindrical wedge prism; The cylindrical wedge prism is coaxially arranged with the focusing lens and is located on the light-inlet side of the focusing lens; The light-transmitting area of ​​the cylindrical wedge prism is smaller than that of the focusing lens, and the diameter of the cylindrical wedge prism is determined based on the diameter of the focusing lens and the reflectivity of the ultra-high reflectivity target.

6. The apparatus according to claim 5, characterized in that, The main detector is located at the rear focal point of the first outer ring beam of the focusing lens, which is a beam that enters the focusing lens without being refracted by the cylindrical wedge prism; The sub-detector is located at the rear focal point of the first inner ring beam of the focusing lens, which is a beam that has been refracted by the cylindrical wedge prism before entering the focusing lens.

7. The apparatus according to claim 1, characterized in that, The device further includes: an annular hollow wedge-shaped prism; The annular hollow wedge prism is coaxially arranged with the focusing lens and is located on the light-inlet surface side of the focusing lens; The light-transmitting area of ​​the annular hollow wedge prism is smaller than that of the focusing lens. The outer diameter of the annular hollow wedge prism is equal to that of the focusing lens. The ring width of the annular hollow wedge prism is determined based on the diameter of the focusing lens and the reflectivity of the ultra-high reflectivity target.

8. The apparatus according to claim 7, characterized in that, The main detector is located at the rear focal point of the second inner ring beam of the focusing lens, which is a beam that enters the focusing lens without being refracted by the annular hollow wedge prism; The sub-detector is located at the rear focal point of the second outer ring beam of the focusing lens, which is a beam that enters the focusing lens after being refracted by the annular hollow wedge prism.

9. The apparatus according to any one of claims 1-8, characterized in that, The main detector includes a main photosensitive surface, and the secondary detector includes a secondary photosensitive surface. The main photosensitive surface and the secondary photosensitive surface are encapsulated in a detector housing.

10. A laser ranging method, characterized in that, The method using the laser ranging echo receiving device according to any one of claims 1-9 comprises: When the main detector is in a state of receiving saturation, the range response value of the secondary detector is output based on the received laser echo to achieve distance measurement of targets with extremely high reflectivity; otherwise, The main detector outputs a ranging response value based on the received laser echo to achieve distance measurement of targets with general reflectivity.

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