Optical system and laser range finder

Abstract

The utility model relates to the technical field of distance measurement, and discloses an optical system and a laser range finder, and the optical system is composed of a first lens, a second lens and a third lens. The second lens is arranged on the first lens; the third lens is arranged on the first lens or the second lens; wherein the first lens is configured to converge light in a preset far-field range, the second lens is configured to converge light in a first preset near-field range, and the third lens is configured to converge light in a second preset near-field range. The optical system not only can effectively solve the problem of a short-distance measurement blind area of the laser range finder, but also has the advantages of simple structure, convenience in installation and adjustment, low cost, easiness in batch production and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of distance measurement technology, and in particular to an optical system and a laser range finder. BACKGROUND

[0002] The laser range finder is a measuring tool for distance measurement by using the laser ranging principle, and is a safe, fast and convenient portable ranging device. The laser range finder with transmitting and receiving off-axis is widely used due to its simple structure, convenient installation, low cost and easy mass production. However, due to the off-axis of the transmitting and receiving light paths, when measuring a short distance, the convergence point of the light after passing through the receiving lens will gradually deviate from the center of the Avalanche Photon Diode (APD), the smaller the distance, the greater the deviation of the light convergence point from the center of the APD, and the weaker the received signal, until the APD effective surface is completely deviated, and thus an effective signal cannot be obtained, resulting in a measurement blind area.

[0003] Therefore, how to effectively eliminate the measurement blind area of the laser range finder with transmitting and receiving off-axis becomes a technical problem to be solved. CONTENT OF THE INVENTION

[0004] Therefore, the present application provides an optical system and a laser range finder to effectively solve the problem of the measurement blind area of the laser range finder with transmitting and receiving off-axis.

[0005] In a first aspect, the present application provides an optical system, which is composed of a first lens, a second lens and a third lens; the second lens is arranged on the first lens; the third lens is arranged on the first lens or the second lens; wherein the first lens is configured to converge light in a preset far field range, the second lens is configured to converge light in a first preset near field range, and the third lens is configured to converge light in a second preset near field range.

[0006] In an embodiment, the second lens is arranged on the exit surface of the first lens, and the third lens is arranged on the exit surface of the first lens or the exit surface of the second lens.

[0007] In an embodiment, the first lens is a plano-convex aspheric lens, the exit surface of the first lens is a plane, and / or the exit surface of the second lens and the third lens is one of a cylindrical surface, a spherical surface or an aspheric surface.

[0008] In an embodiment, the width of the second lens close to the center of the first lens is greater than the width of the second lens away from the center of the first lens, and / or the thickness of the second lens close to the center of the first lens is less than the thickness of the second lens away from the center of the first lens.

[0009] In an embodiment, the length of the second lens in the longitudinal axis direction of the first lens is not greater than half of the aperture of the first lens in the longitudinal axis direction; and the width of the second lens in the transverse axis direction of the first lens is not greater than 3 / 5 of the width of the first lens in the transverse axis direction.

[0010] In an embodiment, the width of the second lens gradually decreases from the center to the edge of the first lens along the longitudinal axis direction of the first lens; and / or, the thickness of the second lens gradually increases from the center to the edge of the first lens along the longitudinal axis direction of the first lens.

[0011] In an embodiment, the length of the third lens in the longitudinal axis direction of the first lens is not greater than the length of the second lens in the longitudinal axis direction; and the width of the third lens in the transverse axis direction of the first lens is not greater than the width of the second lens in the transverse axis direction.

[0012] In an embodiment, the edge of the third lens away from the center of the first lens is aligned with the edge of the second lens away from the center of the first lens.

[0013] In an embodiment, the thickness of the third lens close to the center of the first lens is less than the thickness of the third lens away from the center of the first lens.

[0014] In an embodiment, the projection of the third lens on the exit surface of the first lens is rectangular.

[0015] In an embodiment, the first lens, the second lens and the third lens are integrally formed.

[0016] In an embodiment, the first lens, the second lens and the third lens are symmetrical about the longitudinal axis of the first lens.

[0017] In an embodiment, the aperture of the first lens is less than 25mm, and the focal length is not greater than 35mm; the curvature radius R1 of the second lens and the curvature radius R2 of the third lens respectively satisfy the following expressions: 180mm < R1 < 300mm, 50mm < R2 < 110mm.

[0018] In an embodiment, the portion of the second lens close to the center of the first lens is arc-shaped.

[0019] In an embodiment, the height h1 of the highest point of the second lens from the exit surface of the first lens in the portion close to the edge of the first lens and the height h2 of the highest point of the second lens from the exit surface of the first lens in the portion close to the center of the first lens satisfy the following relationship: h1 < 0.5 mm, h2 < 0.3 mm, and h1 > h2.

[0020] In an embodiment, the height h3 of the highest point of the third lens from the exit surface of the first lens in the portion close to the edge of the first lens and the height h4 of the highest point of the third lens from the exit surface of the first lens in the portion close to the center of the first lens satisfy the following relationship: h3 < 1 mm, h4 < 0.5 mm, and h3 > h4 > h1 > h2.

[0021] In an embodiment, the third lens is arranged on the exit surface of the first lens, the exit surfaces of the second lens and the third lens are spherical surfaces, and the radii of curvature r1 of the second lens and the radii of curvature r2 of the third lens satisfy the following expressions, respectively: 100 mm < r1 < 250 mm, and 30 mm < r2 < 80 mm.

[0022] In a second aspect, the present application further provides a laser range finder, which comprises a laser source, a sensor, and any one of the optical systems provided by the present application, the laser source is used to emit laser to a target to be measured, and the optical system is used to converge the light reflected by the target to be measured to the sensor.

[0023] In an embodiment, the second lens and the third lens are arranged in a first region of the exit surface of the first lens, and the first region is located on one side of the transverse axis of the first lens and close to the laser source.

[0024] The optical system provided by the present application comprises a first lens, a second lens, and a third lens. By arranging the second lens on the first lens and arranging the third lens on the first lens or on the second lens, the laser range finder using the optical system has good measurement effect in long-distance measurement, and the second lens and the third lens can converge light in near-distance measurement, thereby playing an optical compensation role, so that the laser range finder can also have good measurement effect in near-distance measurement, and effectively solves the measurement blind area problem of the transceiver off-axis laser range finder. BRIEF DESCRIPTION OF DRAWINGS

[0025] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the optical path of a laser rangefinder during distance measurement in one embodiment of this application;

[0027] Figure 2 This is a schematic diagram of the structure of an optical system in one embodiment of this application;

[0028] Figure 3 This is another schematic diagram of the optical system in one embodiment of this application;

[0029] Figure 4 for Figure 3 A schematic diagram of the front structure of the optical system shown;

[0030] Figure 5 for Figure 3 Side view of the optical system shown;

[0031] Figure 6 for Figure 3 A schematic diagram of the front structure of the optical system shown;

[0032] Figure 7 for Figure 6 A cross-sectional view of the optical system shown along the CC direction;

[0033] Figure 8 A graph showing the relationship between the received signal strength and the measured distance of the laser rangefinder provided in this application.

[0034] Explanation of reference numerals in the attached figures:

[0035] 100. Laser rangefinder; 10. Laser source; 20. Collimating lens; 30. Target to be measured; 40. Optical system; 41. First lens; 42. Second lens; 43. Third lens; 50. Sensor; 81. Longitudinal axis of the first lens; 82. Transverse axis of the first lens. Detailed Implementation

[0036] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0037] It should be understood that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship between the components in a certain specific posture.

[0038] It should also be understood that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or may be connected to an intermediary element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element through an intermediary element.

[0039] The terminology used in this application specification is for the purpose of describing particular embodiments only and is not intended to limit the application. Descriptions using terms such as "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature.

[0040] like Figure 1 and Figure 2 As shown, Figure 1 This is a schematic diagram of the optical path of a laser rangefinder during distance measurement in one embodiment of this application. Figure 2 This is a schematic diagram of the optical system in one embodiment of this application. The laser rangefinder 100 can be a laser rangefinder with off-axis transmission and reception. The laser rangefinder 100 includes a laser source 10, a collimating lens 20, an optical system 40, and a sensor 50.

[0041] When it is necessary to measure the distance between the laser source 10 and the target 30, the laser source 10 emits a laser beam toward the target 30. After passing through the collimating lens 20, the laser beam is directed toward the target 30. The laser beam undergoes diffuse reflection at the target 30, and the reflected light is focused onto the sensor 50 through the optical system 40, thereby completing the measurement.

[0042] The optical system 40 can be the receiving lens of the laser rangefinder 100, and the optical system 40 is composed of a first lens 41, a second lens 42, and a third lens 43. The second lens 42 and the third lens 43 are both disposed on the first lens 41.

[0043] In one embodiment, the first lens 41 is a plano-convex aspherical lens. The incident surface of the first lens 41 is convex and aspherical, and the exit surface of the first lens 41 is planar. The second lens 42 and the third lens 43 are both disposed on the exit surface of the first lens 41. Since the second lens 42 and the third lens 43 are located on the exit surface of the first lens 41 near the sensor 50, during close-range ranging, not only can the amount of light entering the ranging blind zone be increased, but the overall energy distribution received by the sensor 50 can also be made smoother, achieving a uniform transition of energy intensity. In addition, the fact that the second lens 42 and the third lens 43 are disposed on the exit surface of the first lens 41 is also beneficial to production, reducing the manufacturing cost of the optical system 40.

[0044] like Figure 2 As shown, the exit surfaces of both the second lens 42 and the third lens 43 are spherical. The spherical radii r1 of the second lens 42 and r2 of the third lens 43 satisfy the following expressions:

[0045] 100mm<r1<250mm, 30mm<r2<80mm.

[0046] When the laser rangefinder 100 performs distance measurement, the first lens 41 is configured to converge light within a preset far-field range, the second lens 42 is configured to converge light within a first preset near-field range, and the third lens 43 is configured to converge light within a second preset near-field range. Thus, when the target 30 is within the preset far-field range, the first lens 41 primarily converges the light; when the target 30 is within the first preset near-field range, the second lens 42 and the overlapping lens area of ​​the first lens 41 converge the light, compensating for the first lens 41's focusing effect; when the target 30 is within the second preset near-field range, the third lens 43 and the overlapping lens area of ​​the first lens 41 converge the light, compensating for the first lens 41's focusing effect. Therefore, the application... Figure 2 The laser rangefinder 100 of the optical system 40 shown can measure not only at long distances but also at close distances, overcoming the blind zone problem of traditional laser sensors at close distances.

[0047] Specifically, in Figure 2In the illustrated embodiment, the first lens 41 is used to converge light rays from 1m to infinity, the second lens 42 is used to converge light rays from 0.5m to 1m, and the third lens 43 is used to converge light rays from 0m to 0.5m. It should be noted that the values ​​of 0.5m and 1m mentioned above can be understood as approximately 0.5m and approximately 1m, respectively. That is, the starting point of the light convergence range of the second lens 42 is approximately 0.5m, which could be 0.4m or 0.55m, etc., and the ending point of the light convergence range is approximately 1m, which could be 0.95m or 1.01m, etc.

[0048] In one embodiment, the second lens 42 and the third lens 43 can be bonded to the first lens 41. Of course, the second lens 42 and the third lens 43 can also be combined with the first lens 41 in other ways. For example, the second lens 42 and the third lens 43 can be integrally formed with the first lens 41. There is no limitation on the combination of the first lens 41, the second lens 42 and the third lens 43.

[0049] In one embodiment, to better and more conveniently control the light deflection in the measurement blind zone, the second lens 42 and the third lens 43 are disposed on a first region of the exit surface of the first lens 41, the first region being located on one side of the transverse axis 82 of the first lens 41 and close to the laser source 10. Figure 2 As shown, Figure 2 The shaded area with the diagonal line is the first region, labeled A. That is to say, when... Figure 2 The optical system 40 shown is applied to Figure 1 In the laser rangefinder 100 shown, the first region A is positioned downwards so that the first region A is closer to the laser source 10.

[0050] In one embodiment, the sensor 50 may include an avalanche photodiode (APD). The off-axis distance D from the center of the laser source 10 to the center of the sensor 50 satisfies the following condition: 10mm ≤ D ≤ 15mm.

[0051] In this embodiment, when the target 30 is far from the laser rangefinder 100, the first lens 41 in the optical system 40 plays a major role in focusing the light, thereby converging the reflected and scattered light onto the sensor 50. When the target 30 is close to the laser rangefinder, the convergence point of the light gathered by the first lens 41 is off-center from the center of the sensor 50, resulting in weaker light received by the sensor 50. At this time, the second lens 42 and the third lens 43 in the optical system 40 play a major role in focusing the light, compensating for the focusing effect of the first lens 41, thereby converging more reflected and scattered light onto the sensor 50, thus completing the measurement. This laser rangefinder 100 not only has the advantages of simple structure, convenient assembly and adjustment, low cost, and ease of mass production, but also enables close-range ranging, solving the problem of measurement blind spots that occur in traditional laser rangefinders at close range.

[0052] like Figure 1 and Figure 3 As shown, Figure 1 This is a schematic diagram of the optical path of a laser rangefinder during distance measurement in one embodiment of this application. Figure 3 This is another schematic diagram of the optical system in one embodiment of this application. The laser rangefinder 100 can be a laser rangefinder with off-axis transmission and reception. The laser rangefinder 100 includes a laser source 10, a collimating lens 20, an optical system 40, and a sensor 50.

[0053] When it is necessary to measure the distance between the laser source 10 and the target 30, the laser source 10 emits a laser beam toward the target 30. After passing through the collimating lens 20, the laser beam is directed toward the target 30. The laser beam undergoes diffuse reflection at the target 30, and the reflected light is focused onto the sensor 50 through the optical system 40, thereby completing the measurement.

[0054] The optical system 40 can be a receiving lens of the laser rangefinder 100, and it consists of a first lens 41, a second lens 42, and a third lens 43. The second lens 42 is disposed on the first lens 41, and the third lens 43 is disposed on the second lens 42. The first lens 41 is configured to converge light rays within a preset far-field range, the second lens 42 is configured to converge light rays within a first preset near-field range, and the third lens 43 is configured to converge light rays within a second preset near-field range.

[0055] It should be noted that the specific values ​​of the first preset near field range and the second preset near field range can be adjusted according to the specific parameters of the first lens 41, the second lens 42 and the third lens 43, and no specific restrictions are imposed here.

[0056] Specifically, in one embodiment, the second lens 42 is disposed on the exit surface of the first lens 41, and the third lens 43 is disposed on the exit surface of the second lens 42. Since the second lens 42 and the third lens 43 are located on the side of the first lens 41 closest to the sensor 50, during close-range ranging, not only can the amount of light entering the ranging blind zone be increased, but the overall trend of the energy distribution received by the sensor 50 can also be made gentle, achieving a uniform transition of energy intensity.

[0057] Furthermore, in one embodiment, to better and more conveniently control the light deflection in the measurement blind zone, such as... Figure 3 As shown, the second lens 42 and the third lens 43 are disposed in the first region A of the exit surface of the first lens 41. The first region A is located on one side of the transverse axis 82 of the first lens 41 and close to the laser source 10. That is, when Figure 3 The optical system 40 shown is applied to Figure 1 In the laser rangefinder 100 shown, the first region A is positioned downwards so that the first region A is closer to the laser source 10.

[0058] In one embodiment, the first lens 41 is a plano-convex aspherical lens. The incident surface of the first lens 41 is convex and aspherical, and the exit surface of the first lens 41 is planar. The exit surfaces of the second lens 42 and the third lens 43 are cylindrical, spherical, or aspherical. Since the second lens 42 is disposed on the exit surface of the first lens 41, i.e., on a plane, it facilitates manufacturing and reduces the production cost of the optical system 40.

[0059] like Figure 4 As shown, Figure 4 for Figure 3 The diagram shows a front view of the optical system. The width c of the second lens 42 near the center of the first lens 41 is greater than the width d of the second lens 42 away from the center of the first lens 41. That is, when the portion of the second lens 42 near the center of the first lens 41 is called the bottom, and the portion away from the center of the first lens 41 is called the top, the width c of the bottom of the second lens 42 will be greater than the width d of its top, thus forming a shape that is narrower at the top and wider at the bottom.

[0060] It is understood that in some embodiments, the second lens 42 may be generally shaped as narrower at the top and wider at the bottom, and the edges of the second lens 42 may not be regular in shape. In other embodiments, the edges of the second lens 42 may also be regular in shape, such as... Figure 4As shown, the width of the second lens 42 gradually decreases from the center to the edge of the first lens 41 along the longitudinal axis 81. That is, the second lens 42 gradually narrows in width from its bottom to its top, thus forming a shape that is narrow at the top and wide at the bottom. The edges of the second lens 42 are thus arranged to have a more regular shape.

[0061] In one embodiment, because the width of the second lens 42 near the center of the first lens 41 is wider, i.e., the bottom of the second lens 42 is wider, the light energy compensated in this area is greater. To ensure the measurement accuracy of the laser rangefinder 100, the portion of the second lens 42 near the center of the first lens 41 is arc-shaped. For example, as... Figure 4 As shown, in Figure 4 In the optical system 40 shown, the bottom of the second lens 42 has two arcs B on both sides. These arcs B can be arcs with a preset radius obtained through chamfering technology, and the preset radius can be less than 3mm. By chamfering the bottom of the second lens 42, the compensation light in the corresponding measurement blind zone can be better adjusted, ensuring the measurement accuracy of the laser rangefinder 100.

[0062] In one embodiment, such as Figure 4 As shown, the length h of the second lens 42 along the longitudinal axis 81 of the first lens 41 is not greater than half the aperture H of the first lens 41 along the longitudinal axis 81. That is, as... Figure 4 As shown, when the bottom of the second lens 42 extends from the center of the first lens 41 towards the edge of the first lens 41, the maximum extension length cannot exceed half the aperture H of the first lens 41. That is, the top of the second lens 42 cannot exceed the edge of the first lens 41, so that the second lens 42 can be completely positioned on the exit surface of the first lens 41 in the longitudinal axis 81 direction. In addition, the width of the second lens 42 in the transverse axis 82 direction of the first lens 41 is not greater than 3 / 5 of the width of the first lens 41 in the transverse axis 82 direction, so that the second lens 42 can be completely positioned on the first lens 41 in the transverse axis 82 direction without excessively interfering with the light converging of the first lens 41.

[0063] In one embodiment, such as Figure 3 As shown, the thickness of the second lens 42 near the center of the first lens 41 is less than the thickness of the second lens 42 away from the center of the first lens 41. Specifically, as... Figure 5 As shown, Figure 5 for Figure 3 A side view of the optical system shown. Figure 5It can be seen that the thickness of the second lens 42 near the center of the first lens 41 is less than the thickness of the second lens 42 near the edge of the first lens 41, that is, the thickness of the bottom of the second lens 42 is less than the thickness of the top of the second lens 42.

[0064] Furthermore, in one embodiment, the thickness of the second lens 42 gradually increases from the center to the edge of the first lens 41 along the longitudinal axis 81. That is, the thickness of the second lens 42 gradually increases from its bottom to its top, as detailed in [reference needed]. Figure 5 As shown, from Figure 5 It can be seen that the thickness of the second lens 42 gradually increases from the center of the first lens 41 to the edge of the first lens 41.

[0065] In one embodiment, such as Figure 5 As shown, the height h1 of the highest point of the second lens 42 near the edge of the first lens 41 from the exit surface of the first lens 41, and the height h2 of the highest point of the second lens 42 near the center of the first lens 41 from the exit surface of the first lens 41, satisfy the following relationship: h1 < 0.5 mm, h2 < 0.3 mm, and h1 > h2. That is, the height h2 of the highest point at the bottom of the second lens 42 from the exit surface of the first lens 41 is less than 0.3 mm, and the height h1 of the highest point at the top of the second lens 42 from the exit surface of the first lens 41 is less than 0.5 mm.

[0066] like Figure 3 and Figure 4 As shown, the third lens 43 extends from the top to the bottom of the second lens 42, such that the edge of the third lens 43 away from the center of the first lens 41 is aligned with the edge of the second lens 42 away from the center of the first lens 41. In other words, the tops of the third lens 43 and the second lens 42 are aligned with each other. The extendable length 'a' of the third lens 43 along the longitudinal axis 81 of the first lens 41 is no greater than the length 'h' of the second lens 42 along the longitudinal axis 81. The width 'b' of the third lens 43 along the transverse axis 82 of the first lens 41 is no greater than the width of the second lens 42 along the transverse axis 82. In other words, through the design of the length and width of the third lens 43, it can be completely positioned on the exit surface of the second lens 42. The placement of the third lens 43 not only converges the light within the second preset near-field range, thus compensating for the light in the measurement blind zone, but also makes the trend of the measurement signal of the laser rangefinder 100 more stable.

[0067] It should be noted that the specific shape of the third lens 43 is not specifically limited in this application, and it can be any shape. Figure 3 The shape inFigure 3 The projection of the third lens 43 onto the exit surface of the first lens 41 is rectangular, as shown. Figure 4 As shown, at this time, the width b of the third lens 43 is not greater than the width d of the top of the second lens 42.

[0068] like Figure 3 and Figure 5 As shown, the thickness of the third lens 43 near the center of the first lens 41 is less than the thickness of the third lens 43 away from the center of the first lens 41. It should be noted that the thicknesses of the second lens 42 and the third lens 43 in this application are based on the exit surface of the first lens 41. For example, the thickness of the third lens 43 near the center of the first lens 41 refers to the distance between the portion of the third lens 43 near the center of the first lens 41 and the exit surface of the first lens 41; the thickness of the third lens 43 away from the center of the first lens 41 refers to the distance between the portion of the third lens 43 away from the center of the first lens 41 and the exit surface of the first lens 41.

[0069] Furthermore, in one embodiment, as Figure 5 As shown, the height h3 of the highest point of the third lens 43 near the edge of the first lens 41 from the exit surface of the first lens 41 and the height h4 of the highest point of the third lens 43 near the center of the first lens 41 from the exit surface of the first lens 41 satisfy the following relationship: h3 < 1 mm, h4 < 0.5 mm, and h3 > h4 > h1 > h2.

[0070] In one embodiment, the aperture H of the first lens 41 is less than 25mm, and its focal length is no greater than 35mm. The radius of curvature R1 of the second lens 42 and the radius of curvature R2 of the third lens 43 satisfy the following expressions: 180mm < R1 < 300mm, 50mm < R2 < 110mm.

[0071] In one embodiment, the first lens 41, the second lens 42, and the third lens 43 may be integrally formed. For example... Figure 6 and Figure 7 As shown, Figure 6 for Figure 3 The diagram shows the front view of the optical system. Figure 7 for Figure 6 The optical system shown is a cross-sectional view along the CC direction. From Figure 7 It can be seen that after the first lens 41, the second lens 42 and the third lens 43 are integrally formed, the positional relationship between the three lenses, and the change in the thickness of the second lens 42 and the third lens 43 in the direction of the longitudinal axis 81 of the first lens 41.

[0072] In one embodiment, the first lens 41, the second lens 42, and the third lens 43 are symmetrical about the longitudinal axis 81 of the first lens 41.

[0073] In the optical system 40 provided in this application embodiment, when the target 30 is within a preset far-field range of the laser rangefinder 100, the first lens 41 plays a major role in focusing the light, thereby converging the reflected scattered light onto the sensor 50; when the target 30 is within a first preset near-field range of the laser rangefinder 100, the second lens 42 plays a major role in focusing the light, thereby deflecting and converging the reflected scattered light onto the sensor 50, thus achieving light compensation within the first preset near-field range and solving the problem of the measurement blind zone of the laser rangefinder 100 within the first preset near-field range; when the target 30 is within a second preset near-field range of the laser rangefinder 100, the third lens 43 plays a major role in focusing the light, thereby deflecting and converging the reflected scattered light onto the sensor 50, thus achieving light compensation within the second preset near-field range and solving the problem of the measurement blind zone of the laser rangefinder 100 within the second preset near-field range.

[0074] In particular, when the photosensitive area of ​​sensor 50 is very small, the optical system 40 of this application can better focus light onto sensor 50, achieving no measurement blind spots within the overall measurement range and ensuring a stable overall signal trend. Specifically, as... Figure 8 As shown, Figure 8 This diagram illustrates the relationship between the received signal strength and the measured distance of the laser rangefinder provided in this application. The laser rangefinder 100 employs... Figure 3 The optical system 40 shown; in Figure 8 The diagram shows three signal segments, from left to right, corresponding to the signal strengths compensated by the third lens 43, the second lens 42, and the first lens 41 at corresponding distances. Figure 8 It is easy to see that the optical system 40 can make the signal trend relatively smooth throughout the entire measurement range.

[0075] In addition, the laser rangefinder 100 using the optical system 40 of this application not only has the advantages of simple structure, convenient assembly and adjustment, low cost and easy mass production, but also can realize close-range distance measurement, solving the problem of measurement blind zone in traditional laser rangefinders when measuring at close range.

[0076] Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples.

[0077] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An optical system, characterized in that, The optical system consists of a first lens, a second lens, and a third lens; The second lens is disposed on the first lens; The third lens is disposed on the first lens, or disposed on the second lens; The first lens is configured to converge light rays within a preset far-field range, the second lens is configured to converge light rays within a first preset near-field range, and the third lens is configured to converge light rays within a second preset near-field range.

2. The optical system according to claim 1, characterized in that, The second lens is disposed on the exit surface of the first lens, and the third lens is disposed on the exit surface of the first lens or on the exit surface of the second lens.

3. The optical system according to claim 1, characterized in that, The first lens is a plano-convex aspherical lens, and the exit surface of the first lens is a plane, and / or the exit surfaces of the second and third lenses are cylindrical, spherical or aspherical.

4. The optical system according to claim 1, characterized in that, The width of the second lens near the center of the first lens is greater than the width of the second lens away from the center of the first lens, and / or the thickness of the second lens near the center of the first lens is less than the thickness of the second lens away from the center of the first lens.

5. The optical system according to claim 1, characterized in that, The length of the second lens along the longitudinal axis of the first lens is not greater than half the aperture of the first lens along the longitudinal axis; the width of the second lens along the transverse axis of the first lens is not greater than 3 / 5 of the width of the first lens along the transverse axis.

6. The optical system according to claim 4, characterized in that, The width of the second lens gradually decreases from the center to the edge of the first lens along the longitudinal axis of the first lens; and / or the thickness of the second lens gradually increases from the center to the edge of the first lens along the longitudinal axis of the first lens.

7. The optical system according to claim 1, characterized in that, The length of the third lens in the longitudinal axis direction of the first lens is not greater than the length of the second lens in the longitudinal axis direction; the width of the third lens in the transverse axis direction of the first lens is not greater than the width of the second lens in the transverse axis direction.

8. The optical system according to claim 7, characterized in that, The edge of the third lens away from the center of the first lens is aligned with the edge of the second lens away from the center of the first lens.

9. The optical system according to claim 1, characterized in that, The thickness of the third lens closer to the center of the first lens is less than the thickness of the third lens farther from the center of the first lens.

10. The optical system according to claim 2, characterized in that, The projection of the third lens onto the exit surface of the first lens is rectangular.

11. The optical system according to claim 1, characterized in that, The first lens, the second lens, and the third lens are integrally formed.

12. The optical system according to claim 1, characterized in that, The first lens, the second lens, and the third lens are symmetrical about the longitudinal axis of the first lens.

13. The optical system according to claim 1, characterized in that, The first lens has an aperture of less than 25mm and a focal length of no more than 35mm; the radius of curvature R1 of the second lens and the radius of curvature R2 of the third lens satisfy the following expressions respectively: 180mm<R1<300mm, 50mm<R2<110mm.

14. The optical system according to claim 1, characterized in that, The portion of the second lens near the center of the first lens is arc-shaped.

15. The optical system according to claim 1, characterized in that, The height h1 of the highest point of the second lens near the edge of the first lens from the exit surface of the first lens and the height h2 of the highest point of the second lens near the center of the first lens from the exit surface of the first lens satisfy the following relationship: h1 < 0.5 mm, h2 < 0.3 mm, and h1 > h2.

16. The optical system according to claim 15, characterized in that, The height h3 of the highest point of the third lens near the edge of the first lens from the exit surface of the first lens and the height h4 of the highest point of the third lens near the center of the first lens from the exit surface of the first lens satisfy the following relationship: h3 < 1 mm, h4 < 0.5 mm, and h3 > h4 > h1 > h2.

17. The optical system according to claim 1, characterized in that, The third lens is disposed on the exit surface of the first lens. The exit surfaces of the second and third lenses are spherical. The radius of curvature r1 of the second lens and the radius of curvature r2 of the third lens satisfy the following expressions: 100mm < r1 < 250mm, 30mm < r2 < 80mm.

18. A laser rangefinder, characterized in that, include: The laser source, the sensor, and the optical system as described in any one of claims 1-17, wherein the laser source is used to emit a laser beam toward a target under test, and the optical system is used to focus the light reflected from the target under test onto the sensor.

19. The laser rangefinder according to claim 18, characterized in that, The second lens and the third lens are disposed in a first region of the exit surface of the first lens, the first region being located on one side of the transverse axis of the first lens and close to the laser source.

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