Middle and long distance range finder

Abstract

The invention discloses a medium and long distance range finder. A laser emission module emits a first laser beam to a to-be-measured object; the to-be-measured object performs diffuse reflection on the first laser beam to form a second laser beam; the laser receiving module receives the second laser beam to detect the to-be-detected object; the control module measures the distance of the to-be-measured object based on the emitting time of the first laser beam and the receiving time of the second laser beam received by the laser receiving module; wherein the first optical axis of the laser transmitting module is parallel to the second optical axis of the laser receiving module, and the light spot divergence angle of the laser transmitting module is smaller than 0.25 mrad. Therefore, the light spot divergence angle of the laser emission module is set to be within the range, the divergence angle is small, it can be guaranteed that light spots are as small as possible and energy in unit area is more concentrated when the laser irradiates a long-distance object, and therefore distance measurement of the long-distance object is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of laser ranging, and in particular to a medium and long-range rangefinder. Background Art

[0002] Currently, the market for medium and long-range rangefinders is still relatively blank. Especially in the range of 10 - 20 km, where both the ranging ability and accuracy need to be ensured. In the military, civilian, or aerospace applications, medium and long-range rangefinders can provide a wider ranging scope, which is a more promising application.

[0003] However, most of the current rangefinders on the market use a system composed of an objective lens and an eyepiece for imaging and aiming, and the magnification of the eyepiece imaging is only 7 times. When imaging at a long distance, due to the extremely large ranging dynamic range with the working distance ranging from 2000 m to 20000 m, it is difficult for the system composed of the objective lens and the eyepiece to achieve clear imaging of the object to be measured at different working distances, and the ranging accuracy is average. Summary of the Invention

[0004] The present invention provides a medium and long-range rangefinder to solve the problem of inaccurate ranging in the related art at long distances.

[0005] To achieve the above object, an embodiment of the present invention provides a medium and long-range rangefinder, including: a laser emission module, a laser reception module, and a control module;

[0006] The laser emission module is used to emit a first laser beam to the object to be measured; the object to be measured diffusely reflects the first laser beam to form a second laser beam;

[0007] The laser reception module is used to receive the second laser beam to detect the object to be measured;

[0008] The control module, which is respectively connected to the laser emission module and the laser reception module, is used to measure the distance to the object to be measured based on the emission time of the first laser beam and the reception time when the second laser beam is received by the laser reception module;

[0009] Wherein, the first optical axis of the laser emission module is parallel to the second optical axis of the laser reception module, and the spot divergence angle of the laser emission module is less than or equal to 0.25 mrad.

[0010] Optionally, the laser emission module includes: a solid-state laser and a collimating and beam expanding lens group; the solid-state laser is used to emit an initial laser beam; the collimating and beam expanding lens group is used to collimate and expand the initial laser beam to form a first laser beam;

[0011] Along the direction of the initial laser beam transmission, a collimating and beam expanding lens group is successively provided with a first lens group and a second lens group. The first lens group includes a first lens with a negative optical power and a second lens with a positive optical power. The second lens group includes a third lens with a negative optical power and a fourth lens with a positive optical power;

[0012] The magnification of the first lens group is greater than 4, and the magnification of the second lens group is greater than 4.

[0013] Optionally, the range of the focal length f1 of the first lens is: -7mm ≤ f1 ≤ -12mm; the range of the focal length f2 of the second lens is: 62mm ≤ f2 ≤ 76mm; the range of the focal length f3 of the third lens is: -11mm ≤ f3 ≤ -17mm; the range of the focal length f4 of the fourth lens is: 120mm ≤ f4 ≤ 170mm.

[0014] Optionally, the range of the front surface curvature radius of the first lens is from -8mm to -10mm, the range of the rear surface curvature radius is from -10mm to -13mm, the range of the central thickness is from 2mm to 2.3mm, and the range of the diameter is from 3mm to 9mm;

[0015] The range of the front surface curvature radius of the second lens is from 31mm to 34mm, the range of the rear surface curvature radius is from 95mm to 105mm, the range of the central thickness is from 3.8mm to 4.3mm, and the range of the diameter is from 7mm to 13mm;

[0016] The range of the front surface curvature radius of the third lens is from 31mm to 34mm, the range of the rear surface curvature radius is from -6mm to -7.8mm, the range of the central thickness is from 3.8mm to 4.3mm, and the range of the diameter is from 11mm to 19mm;

[0017] The range of the front surface curvature radius of the fourth lens is from 240m to 340mm, the range of the rear surface curvature radius is from 48mm to 58mm, the range of the central thickness is from 5mm to 5.8mm, and the range of the diameter is from 31mm to 39mm;

[0018] The air interval distance L0 from the light-emitting surface of the solid-state laser to the front surface of the first lens satisfies: 4mm ≤ L0 ≤ 10mm;

[0019] The air interval distance L1 from the rear surface of the first lens to the front surface of the second lens satisfies: 42mm ≤ L1 ≤ 45mm;

[0020] The air interval distance L2 from the rear surface of the second lens to the front surface of the third lens satisfies: 0.1mm ≤ L2 ≤ 0.3mm;

[0021] The air interval distance L3 from the rear surface of the third lens to the front surface of the fourth lens satisfies: 70mm ≤ L3 ≤ 75mm;

[0022] Among them, the front surface is the surface adjacent to the side of the solid laser, and the rear surface is the surface far from the side of the solid laser.

[0023] Optionally, on at least one surface of at least one of the first lens to the fourth lens, an antireflection film for increasing the transmittance of the initial laser beam is provided. Among them, an antireflection film for increasing the transmittance of the laser beam can be provided on the front and rear surfaces of all lenses. The antireflection film can improve the beam transmission efficiency, reduce the generation of stray light, and the antireflection film needs to reach a high laser damage threshold.

[0024] Optionally, the instantaneous peak power of the solid laser is 150,000 watts, and the wavelength of the initial laser beam is 1535 nm.

[0025] Optionally, the laser receiving module includes: a receiving focusing lens group and a photodetector; the receiving focusing lens group is used to receive and focus the second laser beam, and the photodetector is used to detect the focused second laser beam;

[0026] Along the transmission direction of the second laser beam, the receiving focusing lens group includes a fifth lens with a positive optical power, a sixth lens with a positive optical power, and a seventh lens with a negative optical power;

[0027] The receiving aperture range of the receiving focusing lens group is 90 mm - 105 mm, the RMS radius of the focused spot in the central field of view is less than 50 μm, the total system length is less than 145 mm, and the focal length range is 116 mm to 136 mm.

[0028] Optionally, the radius of curvature of the front surface of the fifth lens ranges from 136 mm to 139 mm, the radius of curvature of the rear surface is infinite, the central thickness ranges from 11.6 mm to 12 mm; the diameter range is 90 mm to 105 mm;

[0029] The radius of curvature of the front surface of the sixth lens ranges from 68 mm to 71 mm, the radius of curvature of the rear surface ranges from -95 mm to -97 mm, the central thickness ranges from 8.3 mm to 8.6 mm; the diameter range is 67 mm to 82 mm;

[0030] The seventh lens is a negative lens, the radius of curvature of the front surface is infinite, the radius of curvature of the rear surface ranges from -188 mm to -189 mm, the central thickness ranges from 7.8 mm to 8.1 mm; the diameter range is 67 mm to 82 mm;

[0031] The air separation distance L4 from the rear surface of the fifth lens to the front surface of the sixth lens satisfies: 18 mm ≤ L4 ≤ 25 mm;

[0032] The air separation distance L5 from the rear surface of the sixth lens to the front surface of the seventh lens satisfies: 6 mm ≤ L5 ≤ 7 mm;

[0033] Among them, the front surface is the surface on the side away from the photoelectric sensor, and the rear surface is the surface on the side adjacent to the photoelectric sensor.

[0034] Optionally, on at least one surface of at least one of the fifth lens to the seventh lens, an antireflection film for increasing the transmittance of the second laser beam is provided. The antireflection film can be provided on the front and rear surfaces of each lens to increase the transmittance of the second laser beam and reduce the generation of stray light.

[0035] Optionally, the medium and long-range rangefinder further includes: a dichroic mirror and an imaging module;

[0036] The dichroic mirror is located on the path of the first laser beam transmission, and is used to transmit the first laser beam to the object to be measured, and is also used to reflect the visible light beam carrying the information of the object to be measured to the imaging module;

[0037] The imaging module is used to coaxialize the third optical axis and the first optical axis of the imaging module according to the visible light beam and the electronic target, and is also used to image the object to be measured according to the visible light beam.

[0038] Optionally, the imaging module includes an imaging lens group and a photosensitive element. The imaging lens group is used to focus the visible light beam, and the photosensitive element is used to sense the focused visible light beam;

[0039] Along the direction of the visible light beam transmission, the imaging lens group includes an eighth lens and a ninth lens. The eighth lens is a positive cemented lens, and the ninth lens is a negative meniscus lens;

[0040] The aperture range of the imaging lens group is 36 mm to 40 mm, the focal length range is 180 mm to 250 mm, and the total length is less than 260 mm.

[0041] Optionally, the radius of curvature range of the first surface of the positive cemented lens is 87 mm to 88 mm, the radius of curvature of the second surface is 68 mm to 70 mm, the radius of curvature range of the third surface is 84 mm to 87 mm, the center thickness range from the first surface to the second surface is 2.9 mm to 3.3 mm, the center thickness range from the second surface to the third surface is 6.8 mm to 7.4 mm, and the diameter range is 36 mm to 50 mm;

[0042] The radius of curvature range of the front surface of the negative meniscus lens is -79 mm to -81 mm, the radius of curvature range of the rear surface is 6.8 mm to 7.2 mm, the center thickness range is 166 mm to 170 mm, and the diameter range is 36 mm to 50 mm;

[0043] The air interval distance L6 from the third surface of the positive cemented lens to the front surface of the negative meniscus lens satisfies: 4.9 mm ≤ L6 ≤ 6 mm;

[0044] The air spacing distance L7 from the rear surface of the negative meniscus lens to the focal point satisfies: 180 mm ≤ L7 ≤ 185 mm;

[0045] Wherein, the front surface is the surface on the side away from the photosensitive element, and the rear surface is the surface adjacent to the photosensitive element.

[0046] Optionally, on at least one surface of at least one lens among the eighth lens to the ninth lens, an antireflection film for enhancing the transmission of the visible light beam is provided, and an antireflection film for enhancing the transmission of the visible light beam can be provided on the front and rear surfaces of each lens.

[0047] Optionally, the medium and long distance rangefinder further includes: a reflection element, located between the imaging lens group and the photosensitive element, for changing the transmission direction of the visible light beam, wherein the optical axis of the photosensitive element is parallel to the first optical axis.

[0048] Optionally, the photosensitive element is a CMOS photosensitive element.

[0049] According to the medium and long distance rangefinder proposed by the embodiment of the present invention, a first laser beam is emitted by the laser emission module to the object to be measured; the object to be measured diffusely reflects the first laser beam to form a second laser beam; the laser reception module receives the second laser beam to detect the object to be measured; the control module measures the distance to the object to be measured based on the emission time of the first laser beam and the reception time when the second laser beam is received by the laser reception module; wherein, the first optical axis of the laser emission module is parallel to the second optical axis of the laser reception module, and the spot divergence angle of the laser emission module is less than or equal to 0.25 mrad. Thus, by setting the spot divergence angle of the laser emission module within the above range, the divergence angle is small, and when the laser hits a long-distance target, the spot can be made as small as possible, and the energy per unit area is more concentrated, thereby realizing the ranging of long-distance objects.

[0050] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. Description of the Drawings

[0051] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0052] Figure 1 It is a block schematic diagram of the medium and long distance rangefinder proposed by the embodiment of the present invention;

[0053] Figure 2 It is a schematic structural diagram of the middle laser emission module in the middle and long-distance rangefinder proposed by the embodiment of the present invention;

[0054] Figure 3 It is the spot diagram of the collimating and beam expanding lens group in the middle and long-distance rangefinder proposed by the embodiment of the present invention;

[0055] Figure 4 It is the full-field spot diagram of the collimating and beam expanding lens group in the middle and long-distance rangefinder proposed by the embodiment of the present invention;

[0056] Figure 5 It is the PSF irradiance schematic diagram of the collimating and beam expanding lens group in the middle and long-distance rangefinder proposed by the embodiment of the present invention;

[0057] Figure 6 It is the wavefront diagram of the collimating and beam expanding lens group in the middle and long-distance rangefinder proposed by the embodiment of the present invention;

[0058] Figure 7 It is the MTF diagram of the collimating and beam expanding lens group in the middle and long-distance rangefinder proposed by the embodiment of the present invention;

[0059] Figure 8 It is a schematic structural diagram of the laser receiving module in the middle and long-distance rangefinder proposed by the embodiment of the present invention;

[0060] Figure 9 It is the full-field spot diagram of the receiving focusing lens group in the middle and long-distance rangefinder proposed by the embodiment of the present invention;

[0061] Figure 10 It is the MTF diagram of the receiving focusing lens group in the middle and long-distance rangefinder proposed by the embodiment of the present invention;

[0062] Figure 11 It is the PSF irradiance schematic diagram of the receiving focusing lens group in the middle and long-distance rangefinder proposed by the embodiment of the present invention;

[0063] Figure 12 It is a schematic diagram of the imaging module in the middle and long-distance rangefinder proposed by the embodiment of the present invention;

[0064] Figure 13 It is a schematic diagram of the optical path structure of the visible light imaging system in the middle and long-distance rangefinder proposed by the embodiment of the present invention;

[0065] Figure 14 It is the MTF schematic diagram of the imaging lens group in the middle and long-distance rangefinder proposed by the embodiment of the present invention;

[0066] Figure 15It is the spot diagram of the imaging lens group in the medium and long distance rangefinder proposed by the embodiments of the present invention;

[0067] Figure 16 It is the field curvature and distortion diagram of the imaging lens group in the medium and long distance rangefinder proposed by the embodiments of the present invention;

[0068] Figure 17 It is the optical path diagram of the imaging lens group in the medium and long distance rangefinder proposed by the embodiments of the present invention. Specific embodiments

[0069] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0070] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those clearly listed steps or units, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0071] Figure 1 It is the block diagram of the medium and long distance rangefinder proposed by the embodiments of the present invention. As Figure 1 shown, the medium and long distance rangefinder includes: a laser emission module 101, a laser reception module 102, and a control module 103;

[0072] The laser emission module 101 is used to emit a first laser beam 01 to the object to be measured; the object to be measured diffusely reflects the first laser beam 01 to form a second laser beam 02;

[0073] The laser reception module 102 is used to receive the second laser beam 02 to detect the object to be measured;

[0074] The control module 103 is respectively connected to the laser emission module 101 and the laser reception module 102, and is used for ranging the object to be measured based on the emission time of the first laser beam 01 and the reception time when the second laser beam 02 is received by the laser reception module 102;

[0075] Wherein, the first optical axis of the laser emission module 101 is parallel to the second optical axis of the laser reception module 102, and the spot divergence angle of the laser emission module 101 is less than 0.25 mrad.

[0076] It should be noted that when the divergence angle of the spot emitted by the laser emission module 101 is less than 0.25 mrad, it can be ensured that when hitting a long-distance target, the spot is as small as possible and the energy per unit area is more concentrated. In this way, most of the energy in the first laser beam 01 can be transmitted to the object to be measured, rather than forming a large-area divergence in the transmission path, resulting in energy loss. Furthermore, the first laser beam 01 can transmit a farther distance compared to a laser beam with a larger divergence angle, so as to range a farther object to be measured.

[0077] In actual operation, when the distance to be measured is farther, the divergence angle of the spot of the laser emission module 101 can be controlled to be smaller for realization. Exemplarily, when the divergence angle of the spot of the laser emission module 101 is controlled to be any value between 0.2 mrad and 0.25 mrad, ranging within the range of 2 km to 20 km can be achieved. If testing a 20 km target under low visibility conditions (such as visibility less than 18 km), a lower divergence angle (such as less than 0.2 mrad) is more beneficial to the testing accuracy and detection rate.

[0078] Optionally, Figure 2 is a schematic structural diagram of the medium laser emission module of the medium and long-distance rangefinder proposed in the embodiment of the present invention. As Figure 2 shown, the laser emission module 101 includes: a solid-state laser 104 and a collimating and beam-expanding lens group 105; the solid-state laser 104 is used for emitting an initial laser beam; the collimating and beam-expanding lens group 105 is used for collimating and beam-expanding the initial laser beam to form the first laser beam 01;

[0079] Along the transmission direction of the initial laser beam, the collimating and beam-expanding lens group 105 is sequentially provided with a first lens group 1051 and a second lens group 1052. The first lens group 1051 includes a first lens 1 with a negative optical power and a second lens 2 with a positive optical power. The second lens group 1052 includes a third lens 3 with a negative optical power and a fourth lens 4 with a positive optical power;

[0080] The magnification of the first lens group 1051 is greater than 4, and the magnification of the second lens group 1052 is greater than 4.

[0081] It can be understood that the solid-state laser 104 can select a laser with high energy to match the lower divergence angle formed after the collimating and beam-expanding lens group 105, so that the target detected by the laser emission module 101 is farther. Exemplarily, the instantaneous peak power of the solid-state laser can be 150,000 watts, and the wavelength of the initial laser beam can be 1535 nm. Using a 1535 nm solid-state laser is safer for the human eye at the same power, effectively avoiding accidental laser irradiation and injuring people at close range.

[0082] The size of the laser exit spot of such a laser is 0.55 mm, the divergence angle is 8 mrad, and the spot size at 5 mm is 0.59 mm. Therefore, it is necessary to expand and collimate the initial laser beam so that the divergence angle of the first laser beam 01 reaches below 0.25 mrad, such as reaching 0.2 mrad to achieve long-distance detection.

[0083] Among them, according to the target divergence angle of 0.2 mrad and the output divergence angle of 8 mrad, it can be known that the magnification of the divergence angle by the collimating and beam-expanding lens group 105 is 40 times. Furthermore, it can be first magnified by the first lens group 1051 and then magnified again by the second lens group 1052 to achieve a magnification of 40 times. Exemplarily, the magnification of the first lens group 1051 can be 8, and the magnification of the second lens group 1052 can be 5. Or the magnification of the first lens group 1051 can be 5, and the magnification of the second lens group 1052 can be 8. Thus, the output divergence angle of the solid-state laser 104 of 8 mrad is expanded and collimated to the target divergence angle of 0.2 mrad.

[0084] Therefore, after the initial laser beam is magnified by the first lens 1, it is collimated by the second lens 2 to reduce the divergence angle, then magnified by the third lens 3, and finally collimated by the fourth lens 4, so that the divergence angle reaches 0.2 mrad.

[0085] Among them, the magnification settings of the first lens 1 to the fourth lens 4 can be obtained by setting the corresponding focal lengths.

[0086] Optionally, the range of the focal length f1 of the first lens is: -7 mm ≤ f1 ≤ -12 mm; the range of the focal length f2 of the second lens is: 62 mm ≤ f2 ≤ 76 mm; the range of the focal length f3 of the third lens is: -11 mm ≤ f3 ≤ -17 mm; the range of the focal length f4 of the fourth lens is: 120 mm ≤ f4 ≤ 170 mm.

[0087] In one embodiment, the first lens 1 may be at a distance of 5 mm from the solid-state laser 104. Furthermore, the spot size at the incident surface of the first lens 1 is 0.59 mm. After being magnified 40 times, the spot size at the exit surface of the fourth lens 4 should be 23.6 mm. Thus, the specific positions of the respective lenses between the first lens 1 and the fourth lens 4 can be obtained based on the above parameters.

[0088] Optionally, the front surface curvature radius of the first lens 1 ranges from -8 mm to -10 mm, the rear surface curvature radius ranges from -10 mm to -13 mm, the central thickness ranges from 2 mm to 2.3 mm, the diameter ranges from 3 mm to 9 mm, and the diameter is preferably 6 mm;

[0089] The front surface curvature radius of the second lens 2 ranges from 31 mm to 34 mm, the rear surface curvature radius ranges from 95 mm to 105 mm, the central thickness ranges from 3.8 mm to 4.3 mm, the diameter ranges from 7 mm to 13 mm, and the diameter is preferably 10 mm;

[0090] The front surface curvature radius of the third lens 3 ranges from 31 mm to 34 mm, the rear surface curvature radius ranges from -6 mm to -7.8 mm, the central thickness ranges from 3.8 mm to 4.3 mm, the diameter ranges from 11 mm to 19 mm, and the diameter is preferably 15 mm;

[0091] The front surface curvature radius of the fourth lens 4 ranges from 240 mm to 340 mm, the rear surface curvature radius ranges from 48 mm to 58 mm, the central thickness ranges from 5 mm to 5.8 mm, the diameter ranges from 31 mm to 39 mm, and the diameter is preferably 35 mm;

[0092] The air gap distance L0 from the exit surface of the solid-state laser 104 to the front surface of the first lens satisfies: 4 mm ≤ L0 ≤ 10 mm;

[0093] The air gap distance L1 from the rear surface of the first lens 1 to the front surface of the second lens 2 satisfies: 42 mm ≤ L1 ≤ 45 mm;

[0094] The air gap distance L2 from the rear surface of the second lens 2 to the front surface of the third lens 3 satisfies: 0.1 mm ≤ L2 ≤ 0.3 mm;

[0095] The air gap distance L3 from the rear surface of the third lens 3 to the front surface of the fourth lens 4 satisfies: 70 mm ≤ L3 ≤ 75 mm;

[0096] Herein, the front surface is the surface on the side adjacent to the solid-state laser 104, and the rear surface is the surface on the side away from the solid-state laser 104.

[0097] Through the above parameter settings, the divergence angle requirement can be met. Moreover, through the settings of the first lens group 1051 and the second lens group 1052, a better wavefront aberration can be obtained, with the wavefront less than 0.05λ and the RMS less than 0.007λ. The total length of the collimating and beam expanding lens group 105 is less than 200 mm, such as 190 mm, which is the optimal solution considering the cost performance of lens processing and the compactness of the system. The smaller optical total length can also avoid the need to use mirrors for light path turning, and minimize the number of optical lenses passing through the system in high-power scenarios, which is extremely important for improving the performance stability and lifespan of the system. The self-luminous efficiency and thermal radiation of high-power solid-state lasers are also smaller than those of fiber lasers, effectively controlling the heat of the whole machine and improving the reliability of the whole machine. For high-power scenarios, the lens material in the laser emission module 101 adopts high-density fused silica glass material, and each lens is a spherical mirror made of glass (such as JGS1 fused silica glass), improving the surface finish of the lens after cold processing. The outer ring of the lens can be fixed with a material with good heat conductivity, and the lens barrel is provided with heat dissipation measures, which can reduce the expansion and contraction rate and the deviation of the lens optical power.

[0098] Optionally, on at least one surface of at least one of the first lens 1 to the fourth lens 4, an antireflection film for increasing the transmission of the initial laser beam is provided.

[0099] Among them, an antireflection film with a wavelength of 1535 nm ± 20 nm can be provided on both surfaces of the first lens 1, and the damage threshold is greater than 20 J / cm 2 , an antireflection film with a wavelength of 1535 nm ± 20 nm can be provided on both surfaces of the second lens 2, and the damage threshold is greater than 20 J / cm 2 , an antireflection film with a wavelength of 1535 nm ± 20 nm can be provided on both surfaces of the third lens 3, and the damage threshold is greater than 20 J / cm 2 , an antireflection film with a wavelength of 1535 nm ± 20 nm can be provided on both surfaces of the fourth lens 4, and the damage threshold is greater than 10 J / cm 2 , so as to ensure that each lens has high transmittance and high damage threshold. The lens material is all JGS1.

[0100] Figure 3 is the spot diagram of the collimating and beam expanding lens group in the medium and long distance rangefinder proposed by the embodiment of the present invention. Figure 3 Spot diagram reference in: chief ray, scale bar: 0.4, the surface is the image plane.

[0101] Figure 4 is the full-field spot diagram of the collimating and beam expanding lens group in the medium and long distance rangefinder proposed by the embodiment of the present invention. Among them, the RMS radius is 0.102 mrad, the GEO radius is 0.179 mrad, the circle diameter is 0.4 mrad, and the chief ray is referenced. From Figure 3 and Figure 4 , it can be seen that the aberration of this collimating and beam expanding lens group is small.

[0102] Figure 5 It is a schematic diagram of the PSF irradiance of the collimating and beam expanding lens group in the medium and long distance rangefinder proposed in the embodiment of the present invention. That is, Figure 5 It reflects the diffraction PSF irradiation situation, and the irradiation intensity within the corresponding divergence angle can reach more than 80%.

[0103] Figure 6 It is the wavefront diagram of the collimating and beam expanding lens group in the medium and long distance rangefinder proposed in the embodiment of the present invention. From Figure 6 it can be seen that the collimating and beam expanding lens group has a very small wavefront aberration.

[0104] Figure 7 It is the MTF diagram of the collimating and beam expanding lens group in the medium and long distance rangefinder proposed in the embodiment of the present invention. From Figure 7 it can be seen that the aberration of the collimating and beam expanding lens group is small.

[0105] Optionally, Figure 8 It is a schematic structural diagram of the laser receiving module in the medium and long distance rangefinder proposed in the embodiment of the present invention. As Figure 8 shown, the laser receiving module 102 includes: a receiving focusing lens group 106 and a photodetector 107; the receiving focusing lens group 106 is used to receive and focus the second laser beam 02, and the photodetector 107 is used to detect the focused second laser beam 02;

[0106] Along the transmission direction of the second laser beam 02, the receiving focusing lens group 106 includes a fifth lens 5 with positive optical power, a sixth lens 6 with positive optical power, and a seventh lens 7 with negative optical power;

[0107] The receiving aperture range of the receiving focusing lens group 106 is 90 mm - 105 mm, the RMS radius of the focused spot in the central field of view is less than 50 μm, the total system length is less than 145 mm, and the focal length range is 116 mm to 136 mm.

[0108] In one embodiment, the receiving aperture of the receiving focusing lens group 106 can be 100 mm, the radius of the central field of view is 1 μm, and under the divergence angle of 0.25 mrad, the receiving spot aperture is about 72 μm, and the photosensitive surface diameter of the photodetector 107 can be 100 μm. At this design value, the laser receiving module 102 can improve the received optical power as much as possible. By setting the focal length at 125 mm, the total length of the lens group can be less than 145 mm. The whole lens group is relatively compact.

[0109] Optionally, the radius of curvature of the front surface of the fifth lens 5 ranges from 136 mm to 139 mm, the radius of curvature of the rear surface is infinite, the central thickness ranges from 11.6 mm to 12 mm; the diameter ranges from 90 mm to 105 mm, preferably 100 mm;

[0110] The radius of curvature of the front surface of the sixth lens 6 ranges from 68 mm to 71 mm, the radius of curvature of the rear surface ranges from -95 mm to -97 mm, the central thickness ranges from 8.3 mm to 8.6 mm; the diameter ranges from 67 mm to 82 mm, preferably 75 mm;

[0111] The seventh lens 7 is a negative lens, the radius of curvature of the front surface is infinite, the radius of curvature of the rear surface ranges from -188 mm to -189 mm, the central thickness ranges from 7.8 mm to 8.1 mm; the diameter ranges from 67 mm to 82 mm, preferably 75 mm;

[0112] The air spacing distance L4 from the rear surface of the fifth lens 5 to the front surface of the sixth lens 6 satisfies: 18 mm ≤ L4 ≤ 25 mm;

[0113] The air spacing distance L5 from the rear surface of the sixth lens 6 to the front surface of the seventh lens 7 satisfies: 6 mm ≤ L5 ≤ 7 mm;

[0114] Wherein, the front surface is the side surface away from the photoelectric sensor 107, and the rear surface is the side surface adjacent to the photoelectric sensor 107.

[0115] Optionally, on at least one surface of at least one of the fifth lens 5 to the seventh lens 7, an antireflection film for increasing the transmission of the second laser beam 02 is provided.

[0116] Among them, the fifth lens 5 to the seventh lens 7 are all glass spherical mirrors. Among them, the lens material of the fifth lens 5 is H-ZLAF89L, the lens material of the sixth lens 6 is H-ZF12, and the lens material of the seventh lens 7 is H-QK3L. Antireflection films with 1535 nm ± 2 nm can be provided on both sides of the three lenses to increase the transmittance of the second laser beam 02.

[0117] Figure 9 It is the point spread function diagram of the full field of view of the receiving focusing lens group in the medium and long distance rangefinder proposed in the embodiment of the present invention. From Figure 9 It can be seen that the RMS radius of the light spot after passing through the receiving focusing lens group is 13.95 μm, the GEO radius is 17.712 μm, the circle diameter is 40 μm, reference: centroid. The aberration of this receiving focusing lens group is small.

[0118] Figure 10 It is the MTF diagram of the receiving focusing lens group in the medium and long distance rangefinder proposed in the embodiment of the present invention. From Figure 10 It can be seen that the aberration of this receiving focusing lens group is small.

[0119] Figure 11It is a schematic diagram of the PSF irradiance of the receiving focusing lens group in the medium and long distance rangefinder proposed by the embodiments of the present invention.

[0120] From Figures 9 to 11 It can be seen that for the three-piece separated receiving focusing lens group, the relatively large fifth lens 5 is a plano-convex lens, which reduces the processing difficulty. Even when the aperture is large, it can still quickly converge the light spot, effectively compress the focal length of the receiving lens, and make the structure more compact. At the same time, the relatively small RMS and spot diameter allow a smaller photosensitive surface of the receiving plate to be selected, which is beneficial to reducing high reflection at close range and interference from stray light signals.

[0121] Optionally, Figure 12 It is a schematic diagram of the imaging module in the medium and long distance rangefinder proposed by the embodiments of the present invention. As Figure 12 shown, the medium and long distance rangefinder further includes: a dichroic mirror 108 and an imaging module 109;

[0122] The dichroic mirror 108 is located on the path of the transmission of the first laser beam 01, and is used to transmit the first laser beam 01 to the object to be measured, and is also used to reflect the visible light beam 03 carrying the information of the object to be measured to the imaging module 109;

[0123] The imaging module 109 is used to adjust the third optical axis of the imaging module 109 to be coaxial with the first optical axis according to the visible light beam 03 and the electronic target, and is also used to image the object to be measured according to the visible light beam 03.

[0124] As Figure 12 shown, after the medium and long distance rangefinder is powered on, that is, the photosensitive element 110 is powered on, the solid-state laser 104 is powered on, and the photodetector 107 is powered on. The solid-state laser 104 drives and triggers to generate a 5 Hz pulse signal, and the solid-state laser 104 is turned on to generate a light spot with an exit light spot of 0.55 mm and a full angle of 8 mrad; after the light spot passes through the collimating and beam-expanding lens group 105, the light spot diameter is expanded to 23.6 mm, and the divergence angle is 0.2 mrad; the collimated light is transmitted through the dichroic mirror 108 placed at 45° and reaches the first window plate 113, and then exits the rangefinder and hits the object to be measured. At the same time, the photosensitive element 110 in the imaging module 109 clearly images the object to be measured. The visible light beam passes through the first window plate 113, is reflected by the dichroic mirror 108 to the photosensitive element 110 in the imaging module 109, and is focused and imaged on the CMOS visible light camera. The imaging module 109 and the laser emission module 101 are made to be coaxial through structural tolerances and optical debugging. The electronic target is further calibrated through an algorithm. The center of the target is coaxial with the imaging module 109 and the laser emission module 101, and the position of the object to be measured can be locked more accurately through the collected characteristic region image.

[0125] The light spot generates diffuse reflection after hitting the object to be measured, and is captured by the receiving focusing lens group 106 through the second window piece 112 and converged onto the photodetector 107, generating an electrical signal and sending it to the control module 103. The time interval between the emitted light and the received light is calculated, and the distance of the object to be measured relative to the rangefinder can be obtained using the time-of-flight method. The data is transmitted to the device through the interface. Thus, the rangefinder completes a process of aiming and ranging.

[0126] Among them, the imaging module 109 and the laser emission module 101 share the first window piece 113. Among them, the second window piece 112 and the first window piece 113 are separately arranged, and are two pieces of quartz glass materials with two coating parameters. Separately manufacturing and installing is beneficial to reducing the size of a single window piece, and reducing the coating difficulty and cost. It can also be specially made for the spectrum of the receiving system to filter out interference of specific wavelengths. The window piece can be flat glass.

[0127] Through the setting of the imaging module, it can not only achieve large-field imaging of the object to be measured at close range, but also aim and image small objects to be measured at a long distance. In addition, this electronic imaging can also dynamically scale the imaging area through algorithms, adjust the image contrast and brightness, and even improve the resolution through interpolation. These are all advantages that are difficult to match by traditional eyepiece imaging.

[0128] Optionally, the imaging module 109 includes an imaging lens group (8, 9) and a photosensitive element 110. The imaging lens group (8, 9) is used to focus the visible light beam 03, and the photosensitive element 110 is used to sense the focused visible light beam 03;

[0129] Along the transmission direction of the visible light beam 03, the imaging lens group includes an eighth lens 8 and a ninth lens 9. The eighth lens 8 is a positive cemented lens, and the ninth lens 9 is a negative meniscus lens;

[0130] The aperture range of the imaging lens group (8, 9) is 36 mm to 40 mm, the focal length range is 180 mm to 250 mm, and the total length is less than 260 mm. In one embodiment, the aperture can be 40 mm, the focal length can be 200 mm, and the total length can be 210 mm (as Figure 13 shown).

[0131] Among them, through the setting of the cemented lens, chromatic aberration can be effectively reduced. This imaging lens group is a long-focus lens group, which can image objects at close range and also image objects at a long distance.

[0132] Optionally, the radius of curvature of the first surface of the positive cemented lens ranges from 87 mm to 88 mm, the radius of curvature of the second surface is from 68 mm to 70 mm, the radius of curvature of the third surface ranges from 84 mm to 87 mm, the center thickness from the first surface to the second surface ranges from 2.9 mm to 3.3 mm, the center thickness from the second surface to the third surface ranges from 6.8 mm to 7.4 mm, the diameter ranges from 36 mm to 50 mm, and the diameter is preferably 40 mm;

[0133] The radius of curvature of the front surface of the negative meniscus lens ranges from -79 mm to -81 mm, the radius of curvature of the rear surface ranges from 6.8 mm to 7.2 mm, the center thickness ranges from 166 mm to 170 mm, the diameter ranges from 36 mm to 50 mm, and the diameter is preferably 40 mm;

[0134] The air gap distance L6 from the third surface of the positive cemented lens to the front surface of the negative meniscus lens satisfies: 4.9 mm ≤ L6 ≤ 6 mm;

[0135] The air gap distance L7 from the rear surface of the negative meniscus lens to the focal point satisfies: 180 mm ≤ L7 ≤ 185 mm;

[0136] Wherein, the front surface is the surface on the side away from the photosensitive element, and the rear surface is the surface on the side adjacent to the photosensitive element.

[0137] Optionally, on at least one surface of at least one of the eighth lens 8 to the ninth lens 9, an antireflection film for enhancing the transmission of visible light beams is provided.

[0138] In one embodiment, an antireflection film with a wavelength range of 400 nm - 700 nm can be provided on the sides of both lenses to increase the transmittance of visible light beams. Both lenses are spherical lenses. The lens material between the first surface and the second surface of the eighth lens 8 is H-K3, the lens material between the second surface and the third surface is H-FK95, and the lens material of the ninth lens 9 is H-LAF10LA.

[0139] Figure 14 It is the MTF schematic diagram of the imaging lens group in the medium and long distance rangefinder proposed in the embodiment of the present invention.

[0140] Figure 15 It is the spot diagram of the imaging lens group in the medium and long distance rangefinder proposed in the embodiment of the present invention.

[0141] Figure 16 It is the field curvature and distortion diagram of the imaging lens group in the medium and long distance rangefinder proposed in the embodiment of the present invention.

[0142] Figure 17It is the optical path diagram of the imaging lens group in the medium and long distance rangefinder proposed in the embodiments of the present invention. Among them, the scaling ratio is ±2λ.

[0143] From Figures 14 to 17 It can be seen that the system field of view angle is optimized according to 0.25°, the RMS radius is close to 1μm, and the MTF is close to the diffraction limit; the RMS of the 0° central field of view < 1μm, and the lens design resolution can reach 200 lp / mm (MTF > 0.2, meridional); at a field of view angle of 1°, the RMS < 10μm, and the lens design resolution can reach 90 lp / mm (MTF > 0.2, sagittal). The system still has a certain resolution and is used for edge feature objects in the close-range field of view.

[0144] Optionally, continue to refer to Figure 12 This medium and long distance rangefinder further includes: a reflection element 111, located between the imaging lens group (8, 9) and the photosensitive element 110, for changing the transmission direction of the visible light beam 03. Among them, the optical axis of the photosensitive element 110 is parallel to the first optical axis. Among them, the reflection element 111 can be a reflecting mirror, and the reflecting mirror 111 is used to change the visible light optical path to reduce the overall volume of the medium and long distance rangefinder.

[0145] Optionally, the photosensitive element 110 can be a CMOS photosensitive element. In some embodiments, it can also be a CCD photosensitive element.

[0146] Thus, the small field of view long focal length objective lens (i.e., the imaging lens group) takes into account the imaging of both far and near objects to be measured. The lens cooperates with a high-pixel CMOS camera to make the imaging picture clearer. When the software magnifies the picture for the second time, it is convenient to extract the target features in the target area and reduce the misjudgment rate of the emission optical axis.

[0147] Therefore, the medium and long distance rangefinder proposed in the embodiments of the present invention solves the problem of ranging from 2 km to 20 km through the imaging module combined with the laser emission module and the laser reception module. Among them, in this rangefinder, the high power setting of the solid-state laser and the combination of the collimating and beam expanding lens group better realize the long-distance detection.

[0148] In summary, according to the medium- and long-distance rangefinder proposed in the embodiments of the present invention, a first laser beam is emitted by a laser emission module to an object to be measured; the object to be measured diffusely reflects the first laser beam to form a second laser beam; the laser reception module receives the second laser beam to detect the object to be measured; the control module measures the distance to the object to be measured based on the emission time of the first laser beam and the reception time when the second laser beam is received by the laser reception module; wherein, the first optical axis of the laser emission module is parallel to the second optical axis of the laser reception module, and the spot divergence angle of the laser emission module is less than 0.25 mrad. Thus, by setting the spot divergence angle of the laser emission module within the above range, the divergence angle is small, which can ensure that when the laser hits a distant target, the spot is as small as possible and the energy per unit area is more concentrated, thereby realizing the ranging of distant objects.

[0149] The above specific embodiments do not constitute a limitation on the protection scope of the present 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 principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A medium and long distance rangefinder, characterized in that, It includes: a laser emission module, a laser reception module, and a control module; The laser emission module is used to emit a first laser beam to an object to be measured; the object to be measured diffusely reflects the first laser beam to form a second laser beam; The laser reception module is used to receive the second laser beam to detect the object to be measured; The control module, which is respectively connected to the laser emission module and the laser reception module, is used to measure the distance to the object to be measured based on the emission time of the first laser beam and the reception time when the second laser beam is received by the laser reception module; Wherein, the first optical axis of the laser emission module is parallel to the second optical axis of the laser reception module, and the spot divergence angle of the laser emission module is less than or equal to 0.25 mrad.

2. The medium and long distance rangefinder according to claim 1, characterized in that, The laser emission module includes: a solid-state laser and a collimating and beam-expanding lens group; the solid-state laser is used to emit an initial laser beam; the collimating and beam-expanding lens group is used to collimate and expand the initial laser beam to form the first laser beam; Along the transmission direction of the initial laser beam, the collimating and beam-expanding lens group is sequentially provided with a first lens group and a second lens group. The first lens group includes a first lens with a negative focal power and a second lens with a positive focal power. The second lens group includes a third lens with a negative focal power and a fourth lens with a positive focal power; The magnification of the first lens group is greater than 4, and the magnification of the second lens group is greater than 4.

3. The medium and long distance rangefinder according to claim 2, characterized in that, The range of the focal length f1 of the first lens is: -7 mm ≤ f1 ≤ -12 mm; the range of the focal length f2 of the second lens is: 62 mm ≤ f2 ≤ 76 mm; the range of the focal length f3 of the third lens is: -11 mm ≤ f3 ≤ -17 mm; the range of the focal length f4 of the fourth lens is: 120 mm ≤ f4 ≤ 170 mm.

4. The medium and long distance rangefinder according to claim 2, characterized in that, The range of the front surface curvature radius of the first lens is from -8 mm to -10 mm, the range of the rear surface curvature radius is from -10 mm to -13 mm, the range of the central thickness is from 2 mm to 2.3 mm, and the range of the diameter is from 3 mm to 9 mm; The range of the front surface curvature radius of the second lens is from 31 mm to 34 mm, the range of the rear surface curvature radius is from 95 mm to 105 mm, the range of the central thickness is from 3.8 mm to 4.3 mm, and the range of the diameter is from 7 mm to 13 mm; The range of the front surface curvature radius of the third lens is from 31 mm to 34 mm, the range of the rear surface curvature radius is from -6 mm to -7.8 mm, the range of the central thickness is from 3.8 mm to 4.3 mm, and the range of the diameter is from 11 mm to 19 mm; The range of the front surface curvature radius of the fourth lens is from 240 mm to 340 mm, the range of the rear surface curvature radius is from 48 mm to 58 mm, the range of the central thickness is from 5 mm to 5.8 mm, and the range of the diameter is from 31 mm to 39 mm; The air separation distance L0 from the light-emitting surface of the solid-state laser to the front surface of the first lens satisfies: 4 mm ≤ L0 ≤ 10 mm; The air separation distance L1 from the rear surface of the first lens to the front surface of the second lens satisfies: 42 mm ≤ L1 ≤ 45 mm; The air interval distance L2 from the rear surface of the second lens to the front surface of the third lens satisfies: 0.1 mm ≤ L2 ≤ 0.3 mm; The air interval distance L3 from the rear surface of the third lens to the front surface of the fourth lens satisfies: 70 mm ≤ L3 ≤ 75 mm; Wherein, the front surface is the surface adjacent to the side of the solid laser, and the rear surface is the surface away from the side of the solid laser.

5. The medium and long distance rangefinder according to claim 2, characterized in that, On at least one surface of at least one of the first lens to the fourth lens, an antireflection film for increasing the transmittance of the initial laser beam is provided.

6. The medium and long distance rangefinder according to claim 2, characterized in that, The instantaneous peak power of the solid laser is 150,000 watts, and the wavelength of the initial laser beam is 1535 nm.

7. The medium and long distance rangefinder according to claim 1, characterized in that, The laser receiving module includes: a receiving focusing lens group and a photodetector; the receiving focusing lens group is used to receive and focus the second laser beam, and the photodetector is used to detect the focused second laser beam; Along the transmission direction of the second laser beam, the receiving focusing lens group includes a fifth lens with a positive optical power, a sixth lens with a positive optical power, and a seventh lens with a negative optical power; The receiving aperture range of the receiving focusing lens group is from 90 mm to 105 mm, the RMS radius of the focused spot in the central field of view is less than 50 μm, the total system length is less than 145 mm, and the focal length range is from 116 mm to 136 mm.

8. The medium and long distance rangefinder according to claim 7, characterized in that, The radius of curvature range of the front surface of the fifth lens is from 136 mm to 139 mm, the radius of curvature of the rear surface is infinite, the central thickness range is from 11.6 mm to 12 mm; the diameter range is from 90 mm to 105 mm; The radius of curvature range of the front surface of the sixth lens is from 68 mm to 71 mm, the radius of curvature range of the rear surface is from -95 mm to -97 mm, the central thickness range is from 8.3 mm to 8.6 mm; the diameter range is from 67 mm to 82 mm; The seventh lens is a negative lens, the radius of curvature of the front surface is infinite, the radius of curvature range of the rear surface is from -188 mm to -189 mm, the central thickness range is from 7.8 mm to 8.1 mm; the diameter range is from 67 mm to 82 mm; The air interval distance L4 from the rear surface of the fifth lens to the front surface of the sixth lens satisfies: 18 mm ≤ L4 ≤ 25 mm; The air interval distance L5 from the rear surface of the sixth lens to the front surface of the seventh lens satisfies: 6 mm ≤ L5 ≤ 7 mm; Wherein, the front surface is the surface away from the side of the photoelectric sensor, and the rear surface is the surface adjacent to the side of the photoelectric sensor.

9. The medium and long distance rangefinder according to claim 7, characterized in that, On at least one surface of at least one of the fifth lens to the seventh lens, an antireflection film for increasing the transmittance of the second laser beam is provided.

10. The medium and long distance rangefinder according to claim 1, characterized in that, It further includes: a dichroic mirror and an imaging module; The dichroic mirror is located on the path of the first laser beam transmission, and is used to transmit the first laser beam to the object to be measured, and is also used to reflect the visible light beam carrying the information of the object to be measured to the imaging module; The imaging module is used to coaxialize a third optical axis of the imaging module with the first optical axis according to the visible light beam and the electronic target, and is further used to image the object to be measured according to the visible light beam.

11. The medium and long distance rangefinder according to claim 10, characterized in that, The imaging module includes an imaging lens group and a photosensitive element. The imaging lens group is used to focus the visible light beam, and the photosensitive element is used to sense the focused visible light beam. In the direction of transmission of the visible light beam, the imaging lens group includes an eighth lens and a ninth lens. The eighth lens is a positive cemented lens, and the ninth lens is a negative meniscus lens. The aperture range of the imaging lens group is from 36 mm to 40 mm, the focal length range is from 180 mm to 250 mm, and the total length is less than 260 mm.

12. The medium and long distance rangefinder according to claim 11, characterized in that, The radius of curvature of the first surface of the positive cemented lens ranges from 87 mm to 88 mm, the radius of curvature of the second surface is from 68 mm to 70 mm, the radius of curvature of the third surface ranges from 84 mm to 87 mm. The central thickness range from the first surface to the second surface is from 2.9 mm to 3.3 mm, the central thickness range from the second surface to the third surface is from 6.8 mm to 7.4 mm, and the diameter range is from 36 mm to 50 mm. The radius of curvature of the front surface of the negative meniscus lens ranges from -79 mm to -81 mm, the radius of curvature of the rear surface ranges from 6.8 mm to 7.2 mm, the central thickness range is from 166 mm to 170 mm, and the diameter range is from 36 mm to 50 mm. The air separation distance L6 from the third surface of the positive cemented lens to the front surface of the negative meniscus lens satisfies: 4.9 mm ≤ L6 ≤ 6 mm. The air separation distance L7 from the rear surface of the negative meniscus lens to the focus satisfies: 180 mm ≤ L7 ≤ 185 mm. Wherein, the front surface is the surface on the side far from the photosensitive element, and the rear surface is the surface adjacent to the photosensitive element.

13. The medium and long distance rangefinder according to claim 11, characterized in that, On at least one surface of at least one of the eighth lens to the ninth lens, an antireflection film for increasing the transmittance of the visible light beam is provided.

14. The medium and long distance rangefinder according to claim 11, characterized in that, It further includes: A reflection element, located between the imaging lens group and the photosensitive element, for changing the transmission direction of the visible light beam. Wherein, the optical axis of the photosensitive element is parallel to the first optical axis.

15. The medium and long distance rangefinder according to claim 11, characterized in that, The photosensitive element is a CMOS photosensitive element.

Images