A laser illuminator with large magnification ratio for long-distance lighting

Abstract

The invention discloses a large variable magnification laser illuminator for long-distance lighting, comprising a fourth lens, a third lens, a second lens and a first lens group which are sequentially arranged along the optical axis from the end face of an optical fiber outward, the end face of the optical fiber is generated by an optical fiber connected to a laser, the fourth lens and the third lens are convex lenses with positive focal length, the second lens is a concave lens with negative focal length, the first lens group is a cemented lens with positive focal length composed of a first lens and a second lens, the distance between the fourth lens and the first lens group relative to the end face of the optical fiber is fixed, and a distance adjustment device is provided for adjusting the distance between the third lens and the second lens relative to the end face of the optical fiber, thereby adjusting the illumination angle of the laser illuminator. The invention can solve the problem that the minimum spot size of the prior art is not small enough and the field of view variation range is not large enough.

Description

Technical Field

[0001] The invention relates to a large-magnification laser illuminator for long-distance lighting, belonging to the technical field of laser lighting. Background Art

[0002] Infrared laser lighting technology that uses lasers for auxiliary lighting has been widely used in the field of night vision, and the laser illuminator is the core component that determines the effect of laser lighting. In the prior art, the laser illuminator designed using the imaging principle has the characteristics of good spot uniformity and clear edges, which is conducive to improving the night vision lighting distance.

[0003] The angle of the laser illuminator can be determined according to the field of view of the main long-distance laser night vision devices. In order to ensure the longest night vision distance, the laser spot should be small enough. At the same time, in order to take into account the field of view, the minimum spot of the illuminator should be inscribed on the screen, and the maximum spot should be able to cover the entire field of view of the large field of view as much as possible. This puts high demands on the minimum field of view angle and the range of field of view change of the laser illuminator. The zoom illuminators designed using the imaging principle currently published, such as patents 201510264944.4, 201110185055.0, etc., have a zoom ratio of less than 60 times, and when used with optical fibers with a core diameter of 400um, the minimum field of view angle is greater than 0.3°, the light cannot be concentrated, the spot brightness is low, and it is difficult to meet the requirements of long-distance night vision. Therefore, it is necessary to design a zoom illuminator with a larger zoom ratio, which can meet the needs of longer-distance night vision lighting on the basis of covering a sufficiently large field of view. Summary of the invention

[0004] In view of the defects of the prior art, the present invention provides a large zoom ratio laser illuminator for long-distance lighting, which solves the problems in the prior art that the minimum light spot is not small enough and the field of view variation range is not large enough.

[0005] In order to solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a large zoom ratio laser illuminator for long-distance lighting, comprising a fourth lens, a third lens, a second lens and a first lens group arranged in sequence along the optical axis from the end face of the optical fiber outward, the end face of the optical fiber is generated by the optical fiber connected to the laser, the fourth lens and the third lens are convex lenses with positive optical focal length, the second lens is a concave lens with negative optical focal length, the first lens group is a cemented lens with positive optical focal length composed of a first lens and a second lens, the distance between the fourth lens and the first lens group relative to the end face of the optical fiber is fixed, and a distance adjustment device is provided, the distance adjustment device is used to adjust the distance between the third lens and the second lens relative to the end face of the optical fiber, thereby adjusting the illumination angle of the laser illuminator, that is, achieving zoom.

[0006] Furthermore, the distance adjustment device includes an inner lens barrel, an outer lens barrel, a lens frame, a linear groove, a cam, a cam groove, a motor, a transmission gear and a gear ring. The inner lens barrel is located inside the outer lens barrel, the first lens group, the second lens, and the third lens are respectively arranged in the inner lens barrel through their respective lens frames, the cams are respectively located at both ends of the lens frames of the second lens and the third lens, the linear groove is opened on the inner lens barrel, the cam groove is opened on the outer lens barrel, the cam passes through the linear groove and then extends into the cam groove, the gear ring is fixed on the outer lens barrel, the transmission gear is connected to the output shaft of the motor, and the gear ring is meshed with the transmission gear.

[0007] Furthermore, when the illumination angle of the laser illuminator changes from small to large, the third lens moves from a direction away from the fiber end face to a direction close to the fiber end face, and the second lens moves from a direction close to the fiber end face to a direction away from the fiber end face.

[0008] Furthermore, when the illumination angle of the laser illuminator changes from large to small, the third lens moves from close to the fiber end face to away from the fiber end face, and the second lens moves from away from the fiber end face to close to the fiber end face.

[0009] Furthermore, at the shortest focal length of the laser illuminator, the distance between the third lens and the fourth lens is the smallest, and the distance between the second lens and the third lens is the largest; at the longest focal length, the distance between the second lens and the third lens is the smallest, and the distance between the third lens and the fourth lens is the largest.

[0010] Furthermore, during the laser illuminator magnification change process, the second lens and the third lens simultaneously pass through points where their respective imaging magnifications are -1.

[0011] Furthermore, the zoom ratio of the laser illuminator is f2 / f1≥133, f1≤0.75mm, f2≥100mm, totr<155mm, f1 is the effective focal length of the short focal end of the laser illuminator, f2 is the effective focal length of the long focal end of the zoom laser illuminator, and totr is the total length of the optical system.

[0012] Furthermore, the laser illuminator satisfies the following relationship: (D78max-D78min) / f1≤30, (D34max-D34min) / f2≤1, where D78 max and D78 min are the maximum and minimum values ​​of the interval between the third lens and the fourth lens during the laser illuminator zoom process, D34 max and D34 min They are respectively the maximum and minimum values ​​of the interval between the first lens group and the second lens during the magnification change of the laser illuminator.

[0013] Furthermore, the total length of the laser illuminator optical system is 154.5 mm, the interval between adjacent lenses is not less than 3 mm, and the distance between the fourth lens and the optical fiber end face is greater than 3 mm.

[0014] Furthermore, the laser uses a 400um optical fiber with a maximum illumination angle of 30° and a minimum illumination angle of 0.23°.

[0015] Beneficial effects of the present invention:

[0016] 1. Only two groups of lenses are moved to achieve a super-large zoom ratio of more than 130 times, and the diameter and weight of the moving lens group are very small, which makes it convenient to use a small-power motor and will not reduce the service life of the motor due to excessive load.

[0017] 2. The longest focal length exceeds 100mm. When used with the 400um core diameter optical fiber commonly used in laser lighting, the minimum field of view angle is less than 0.23°, which is much smaller than the 0.3° of conventional laser illuminators. The laser energy is more concentrated, and longer-distance lighting can be achieved.

[0018] 3. The system has a compact structure and a small number of lenses, ensuring the high transmittance and easy assembly of the laser illuminator.

[0019] 4. The total length of the system is fixed, and the first lens group far away from the fiber end face and the fourth lens close to the fiber end face are fixed, so that the inside of the laser illuminator is in a closed state, which is beneficial to improve the stability of the illuminator structure and facilitate mechanical design. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the structure of the laser illuminator described in Example 1;

[0021] Figure 2 This is a schematic diagram of the optical system of the laser illuminator described in Example 1;

[0022] Figure 3 A relationship diagram between the distances between the second lens and the third lens of the laser illuminator described in Example 1 and the front surface of the fourth lens and the focal length of the system;

[0023] In the figure: 1. first lens group, 2. second lens, 3. third lens, 4. fourth lens, 5. optical fiber end face, 6. laser, 7. inner lens barrel, 8. outer lens barrel, 9. lens holder, 10. linear groove, 11. cam, 12. motor, 13. transmission gear, 14. outer gear ring, 15. cam groove, 1-1. first lens, 1-2. second lens, A: the distance between the second lens and the optical fiber end face, B: the distance between the third lens and the optical fiber end face. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0025] Example 1

[0026] This embodiment 1 discloses a large variable magnification laser illuminator for long-distance lighting, such as Figure 1 As shown, the optical system includes a laser 6, an optical fiber end face 5, a fourth lens 4, a third lens 3, a second lens 2, and a first lens group 1. The optical fiber end face 5 is generated by an optical fiber connected to the laser 6, and the fourth lens 4, the third lens 3, the second lens 2 and the first lens group 1 are sequentially arranged at the front end of the optical fiber end face 5 along the optical axis.

[0027] The fourth lens 4 and the third lens 3 are convex lenses with positive focal length, the second lens 2 is a concave lens with negative focal length, the first lens group 1 is a cemented lens composed of a first lens 1-1 and a second lens 1-2, and the second lens 1-2 is located on the side close to the optical fiber end face 4.

[0028] The fourth lens 4 reduces the divergence angle of the laser emitted by the optical fiber, the third lens 3 further converges the light beam converged by the fourth lens 4, the second lens 2 diverges the light beam converged by the third lens 3, and the first lens group 1 converges the light beam diverged by the second lens 2 again.

[0029] The fourth lens 4 and the first lens group 1 are fixed relative to the optical fiber end face 5, and the second lens 2 and the third lens 3 can move along the optical axis to change the field angle of the illuminator to meet the lighting needs at different distances.

[0030] By adjusting the distance between the second lens 2 and the optical fiber end face 5, the divergence angle of the light beam after passing through the first lens group 1 can be adjusted. By adjusting the distance between the third lens 3 and the second lens 2, compensation of the image plane position can be achieved. Therefore, the illumination angle of the laser illuminator can be adjusted over a wide range while the image plane position remains unchanged, thereby achieving a good lighting effect throughout the entire adjustment process.

[0031] In this embodiment, the distance between the second lens 2 and the third lens 3 and the optical fiber end face is adjusted by a distance adjustment device. Figure 1 As shown, the distance adjustment device comprises an inner lens barrel 7, an outer lens barrel 8, a lens frame 9, and a motor 12; the inner lens barrel 7 is located inside the outer lens barrel 8, and the first lens group 1, the second lens 2, and the third lens 3 are respectively arranged in the inner lens barrel through their respective lens frames 9. A linear groove 10 is provided at the relative position of the inner lens barrel 6, and cams 11 are fixed on both sides of the lens frame 9 corresponding to the second lens 2 and the third lens 3 ( Figure 1Only the cam 11 on the upper side is drawn in the figure. A cam groove that matches the cam is provided on the inner surface of the outer barrel 8; the cam 11 passes through the linear groove 10 and then extends into the cam groove. A transmission gear 13 is fixed on the output shaft of the motor 12 shown, and an outer gear ring 14 is fixed on the outer surface of the outer barrel 8. The motor 12 can drive the outer barrel 8 to rotate through the meshing transmission of the outer gear ring 14 and the transmission gear 13. In the process of the motor 12 driving the outer barrel 8 to rotate, the second lens 2 and the third lens 3 can be driven to move along the set cam curve under the driving effect of the cam groove on the cam 11 and the limiting effect of the linear groove 10 on the cam 11, so as to realize the change of the illumination spot angle of the laser illuminator.

[0032] like Figure 2 As shown, the working principle diagram of the high-definition large-angle zoom laser illuminator of the present invention is given. The second lens 2 is a concave lens, which is the only lens in the whole system that provides negative optical power. By moving in the direction of the optical axis, the imaging magnification of the system changes. The third lens 3 is a convex lens, which cooperates with the second lens 2 to make corresponding movements, changing the magnification of the system while ensuring that the image plane position does not change during the zoom process. The second lens 2 and the third lens 3 jointly determine the zoom ratio of the laser illuminator. During the zoom process, the second lens 2 and the third lens 3 simultaneously pass through the points with their respective imaging magnifications of -1, ensuring that the movement directions of the two lens groups will not change during the entire zoom process, shortening the distance of the lens group movement, making the curve smoother, and more conducive to the design of the mechanical structure. The first lens group 1 is formed by gluing the first lens 1-1 and the second lens 1-2, which has a convergence effect on the passing laser, reducing spherical aberration and chromatic aberration caused by laser wavelength drift. The fourth lens 4 is a convex lens with positive optical power, and controls the size of the system's starting focal length together with the first lens group 1.

[0033] As shown in Table 1, a specific structure of a laser illuminator is given, in which the first lens 1-1, the second lens 1-2, and the

[0034] Specific parameters of the second lens 2, the third lens 3 and the fourth lens 4, where the side of the lens away from the fiber end face is the front surface, and the side close to the fiber end face is the back surface:

[0035]

[0036] Table 1

[0037] The distance between the fourth lens 4 of the laser illuminator and the optical fiber end face 5 is 3.7 mm.

[0038] like Figure 3 As shown, a diagram showing the relationship between the distances between the second lens 2 and the third lens 3 and the front surface of the fourth lens 4 in the laser illuminator and the focal length of the system is given. Figure 3In the figure, the ordinate is the distance between the lens and the front surface of the fourth lens 4, and the abscissa is the focal length of the laser illuminator at this time; curve A is the motion curve of the second lens, and curve B is the motion curve of the third lens. Figure 3 It can be seen that in the process of the focal length of the illuminator changing from small to large, the distance between the second lens 2 and the front surface of the fourth lens 4 gradually decreases, and the distance between the third lens 3 and the front surface of the fourth lens 4 gradually increases. At the shortest focal length of the illuminator, the interval between the third lens 3 and the fourth lens 4 is the smallest, which is 4mm. At this time, the interval between the second lens 2 and the third lens 3 is the largest, which is 120mm, and the interval between the first lens group 1 and the second lens 2 is the smallest, which is 5mm; at the longest focal length, the interval between the second lens 2 and the third lens 3 is the smallest, which is 3mm, the interval between the third lens 3 and the fourth lens 4 is the largest, which is 26mm, and the interval between the first lens group 1 and the second lens 2 is the largest, which is 100mm.

[0039] The total length of the laser illuminator optical system is 154.5 mm. To prevent the lenses from affecting each other when changing the magnification, the interval between adjacent lenses is not less than 3 mm, which keeps the structure compact while retaining sufficient space for mechanical design and assembly.

[0040] The laser illuminator has a focal length of f2=100mm at the long focal end, a focal length of f1=0.75mm at the short focal end, a zoom ratio of f2 / f1≥133, and is used with a 400um optical fiber. The maximum illumination angle can reach 30° and the minimum illumination angle can reach 0.23°.

[0041] The above description is only the basic principle and preferred embodiments of the present invention. Improvements and substitutions made by those skilled in the art based on the present invention belong to the protection scope of the present invention.

Claims

1. A laser illuminator with a large zoom ratio for long-distance lighting, comprising a fourth lens, a third lens, a second lens and a first lens group arranged in sequence along the optical axis from the end face of the optical fiber outward, the end face of the optical fiber being generated by an optical fiber connected to a laser, characterized in that: The fourth lens and the third lens are convex lenses with positive focal length, the second lens is a concave lens with negative focal length, the first lens group is a cemented lens with positive focal length composed of the first lens and the second lens, the distance between the fourth lens and the first lens group relative to the optical fiber end face is fixed, and a distance adjustment device is provided, the distance adjustment device is used to adjust the distance between the third lens and the second lens relative to the optical fiber end face, thereby adjusting the illumination angle of the laser illuminator, that is, achieving magnification; the magnification ratio of the laser illuminator is f2 / f1≥133, f1≤0.75mm, f2≥100mm, totr<155m m, f1 is the effective focal length of the short focal end of the laser illuminator, f2 is the effective focal length of the long focal end of the zoom laser illuminator, and totr is the total length of the optical system; the following relationship is satisfied: (D78max-D78min) / f1≤30, (D34max-D34min) / f2≤1, wherein D78max and D78min are respectively the maximum and minimum values ​​of the interval between the third lens and the fourth lens during the laser illuminator zoom process, and D34max and D34min are respectively the maximum and minimum values ​​of the interval between the first lens group and the second lens during the laser illuminator zoom process.

2. The large-magnification laser illuminator for long-distance lighting according to claim 1, characterized in that: The distance adjustment device comprises an inner lens barrel, an outer lens barrel, a lens frame, a linear groove, a cam, a cam groove, a motor, a transmission gear and a gear ring. The inner lens barrel is located inside the outer lens barrel. The first lens group, the second lens and the third lens are respectively arranged in the inner lens barrel through their respective lens frames. The cams are respectively located at both ends of the lens frames of the second lens and the third lens. The linear groove is opened on the inner lens barrel, the cam groove is opened on the outer lens barrel, the cam passes through the linear groove and then extends into the cam groove. The gear ring is fixed on the outer lens barrel, the transmission gear is connected to the output shaft of the motor, and the gear ring is meshed with the transmission gear.

3. The large variable magnification laser illuminator for long-distance lighting according to claim 1, characterized in that: When the illumination angle of the laser illuminator changes from small to large, the third lens moves from a direction away from the fiber end face to a direction close to the fiber end face, and the second lens moves from a direction close to the fiber end face to a direction away from the fiber end face.

4. The large variable magnification laser illuminator for long-distance lighting according to claim 1, characterized in that: When the illumination angle of the laser illuminator changes from large to small, the third lens moves from close to the fiber end face to away from the fiber end face, and the second lens moves from away from the fiber end face to close to the fiber end face.

5. The large variable magnification laser illuminator for long-distance lighting according to claim 3 or 4, characterized in that: At the shortest focal length of the laser illuminator, the distance between the third lens and the fourth lens is the smallest, and the distance between the second lens and the third lens is the largest. At the longest focal length, the distance between the second lens and the third lens is the smallest, and the distance between the third lens and the fourth lens is the largest.

6. The large variable magnification laser illuminator for long-distance lighting according to claim 1, characterized in that: During the laser illuminator magnification change process, the second lens and the third lens simultaneously pass through the points where their respective imaging magnifications are -1.

7. The large variable magnification laser illuminator for long-distance lighting according to claim 1, characterized in that: The total length of the laser illuminator optical system is 154 mm, the interval between adjacent lenses is not less than 3 mm, and the distance between the fourth lens and the optical fiber end face is greater than 3 mm.

8. The large variable magnification laser illuminator for long-distance lighting according to claim 1, characterized in that: The laser uses 400um optical fiber, with a maximum illumination angle of 30° and a minimum illumination angle of 0.23°.

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