1535nm beam expanding lens for miniaturized laser range finder

Abstract

The invention discloses a 1535nm beam expanding lens for a miniaturized laser range finder, which comprises an incident element A1 and an emergent element A2, and the focal points of the incident element A1 and the emergent element A2 coincide; the incident element A1 is a glass ball with the diameter of 0.5-1.5 mm, the emergent element A2 is a plano-convex lens, and the convex surface of the plano-convex lens faces the emergent direction of light. According to the Kepler type beam expanding lens, the small glass ball with the diameter being equal to that of the Kepler type beam expanding lens is adopted as an incident element of the Kepler type beam expanding lens, the plano-convex lens with the convex face facing the light emitting direction is adopted as an emitting element, and therefore when the focal length of the beam expanding lens at the emitting element is small, the beam expanding lens can still have the large amplification factor on laser of 1535 nm; the miniaturized requirement of the range finder is met, high magnification and small size are achieved, meanwhile, the cost is low, and the range finder is easy to install and adjust.

Description

Technical Field

[0001] The invention relates to a 1535nm beam expanding lens for a miniaturized laser rangefinder, belonging to the technical field of optical lenses. Background Art

[0002] In recent years, laser rangefinders are developing in the direction of miniaturization, and the size of the beam expander lens of the laser rangefinder directly affects the size of the whole rangefinder. The prior art uses a telephoto structure as the output element of the beam expander lens to reduce the total length of the lens. The telephoto structure composed of a positive-negative optical power lens group can move the main surface of the lens out of the lens element, and can make the distance from the frontmost surface of the lens element to the focal plane less than its focal length, thereby reducing the size of the lens. However, when using the telephoto structure, the output element of the beam expander lens requires at least two lenses, which is costly and relatively troublesome to assemble and adjust. Summary of the invention

[0003] The present invention provides a 1535nm beam expanding lens for a miniaturized laser rangefinder, which requires few lenses, has low cost and is easy to install and adjust; is adapted to a 1535nm laser, has good correction of spherical aberration, and has a magnification of more than 20 times; has the characteristics of high magnification, small size, low cost, easy installation and adjustment, etc.

[0004] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0005] A 1535nm beam expander lens for a miniaturized laser rangefinder comprises an incident element A1 and an exit element A2, wherein the focal points of the incident element A1 and the exit element A2 coincide with each other; the incident element A1 is a glass ball with a diameter of 0.5-1.5 mm, and the exit element A2 is a plano-convex lens with its convex surface facing the exit direction of light.

[0006] In order to further ensure the quality of beam expansion, the above-mentioned 1535nm beam expander lens for miniaturized laser rangefinder is characterized by satisfying the following relationship: 1.18<M / T<1.17, wherein M is the magnification of the beam expander lens, and T is the total length of the beam expander lens.

[0007] The convex surface of the emission element A2 is an aspherical surface.

[0008] Along the incident direction of light, the two sides of the plano-convex lens are the incident surface and the exit surface respectively. In order to better adapt to the 1535nm laser, the curvature radius of the incident surface is infinite, and the curvature radius of the exit surface is 7.62mm±5%.

[0009] In order to take into account both the requirements of beam expansion and small volume, the center thickness of the plano-convex lens is 2.5 mm±5%. The center interval between the incident element A1 and the exit element A2 is 13.793 mm±5%.

[0010] In order to take into account both the beam expansion quality and processability requirements, the materials used for the incident element A1 and the output element A2 are both H-K9L.

[0011] The output element of the 1535nm beam expansion lens for a miniaturized laser rangefinder uses only one lens, thereby achieving high-magnification beam expansion of the 1535nm laser, meeting the miniaturization requirements of the rangefinder, and having low cost and simple assembly and adjustment.

[0012] It is further preferred that the diameter of the glass ball is 1 mm. This not only meets the requirement of miniaturization, but is also inexpensive and readily available, and can also match the diameter of the laser's exit pupil spot. The diameter of the laser's exit pupil spot of the rangefinder is generally about 0.3 mm. Considering the shielding of mechanical parts and the margin during debugging, 1 mm is the most suitable rounded diameter.

[0013] The technologies not mentioned in the present invention are all referred to the prior art.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] Compared with the prior art, the present invention adopts a glass ball with a diameter of 1 mm as the incident element of the Kepler type beam expander, and a plano-convex aspheric lens with the convex surface facing the light emitting direction as the output element. The glass ball with a diameter of 1 mm has a relatively small focal length. When used as the incident element of the beam expander, the focal length of the output element can take a relatively small value under the same beam expansion ratio requirement, thereby shortening the total length of the lens, so that the output element can meet the miniaturization requirements of the rangefinder using only one lens. In addition, the 1 mm glass ball can be well adapted to the exit pupil spot diameter of the 1535 nm laser, and it is a shelf product with mature technology and can be purchased directly, which greatly reduces the development cost investment of the lens mold and fixture during lens processing. The use of a small focal length element will cause the lens to produce a large high-order spherical aberration. The introduction of an aspheric surface into the output element can correct the high-order spherical aberration of the lens, and can achieve high-quality beam expansion for the 1535 nm laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is an optical system diagram of a 1535nm beam expander lens for a miniaturized laser rangefinder according to the present invention;

[0017] Figure 2 A schematic diagram of the divergence angle deviation of a laser beam with a wavelength of 1535nm after the 1535nm beam expander lens for a miniaturized laser rangefinder provided in an embodiment of the present invention expands the beam;

[0018] Figure 3 A schematic diagram of vertical axis aberration after a 1535nm beam expander lens for a miniaturized laser rangefinder provided in an embodiment of the present invention expands a laser beam having a wavelength of 1535nm; DETAILED DESCRIPTION

[0019] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0020] Example 1

[0021] like Figure 1 As shown, a 1535nm beam expander lens for a miniaturized laser rangefinder includes an incident element A1 and an exit element A2, the focal points of the incident element A1 and the exit element A2 coincide with each other, the incident element A1 is a glass ball with a diameter of 1 mm, and the exit element A2 is a plano-convex lens with its convex surface facing the exit direction of the light.

[0022] The convex surface of the emission element A2 is an aspherical surface.

[0023] The aspheric surface formula is as follows. Table 1 gives the aspheric surface coefficients of this embodiment:

[0024]

[0025] The meanings of the quantities in the equation are as follows:

[0026] z is the lens sagittal height of the aspheric surface along the optical axis;

[0027] c = 1 / R;

[0028] R is the vertex radius of curvature of the lens;

[0029] r is the semi-aperture of the lens perpendicular to the optical axis;

[0030] k is the cone coefficient;

[0031] α1, α2, α3, α4, α5, and α6 are all aspherical coefficients, among which α1, α5, and α6 are all 0.

[0032] Table 1 Aspheric coefficients of the embodiments

[0033] R k <![CDATA[α2]]> <![CDATA[α3]]> <![CDATA[α4]]> -7.62 0 1.6509420E-04 2.0240551E-06 3.4843549E-08

[0034] The material of the incident element A1 and the output element A2 is H-K9L.

[0035] The beam expander lens of the laser rangefinder satisfies the following relationship:

[0036] M / T=1.174, where M is the magnification of the beam expander lens and T is the total length of the beam expander lens.

[0037] Table 1 Optical parameters of each lens in the lens

[0038]

[0039] In the embodiment of the present invention, the laser beam expander formed by the above-mentioned lens group has a magnification of 20.307 times, a total optical path length of 17.293 mm, and a total weight of 0.25 g.

[0040] In the embodiment of the present invention, the spot diameter is 0.3 mm, and the wavelength of the incident laser is 1535 nm. The schematic diagram of the laser output divergence angle deviation after the incident laser is expanded is shown in FIG. Figure 2 As shown in the figure, the RMS deviation is less than 0.002mrad, and the laser beam after beam expansion has good collimation. The vertical axis aberration diagram is shown in Figure 3 As shown in the figure, it can be seen that the high-order spherical aberration of the lens is well corrected, and the maximum axial aberration within the full aperture is only 0.000262mm.

[0041] The above-mentioned beam expander lens adopts a glass ball with a diameter of 1mm as the incident element of the Kepler type beam expander, and a plano-convex lens with the convex surface facing the emitting direction of the light as the emitting element, so that the beam expander lens can still have a large magnification for the 1535nm laser when the focal length of the emitting element takes a small value; it meets the miniaturization requirements of the rangefinder, while achieving high magnification and small size, it also takes into account low cost and simple installation and adjustment.

Claims

1. A 1535nm beam expander lens for a miniaturized laser rangefinder, characterized in that: It includes an incident element A1 and an exit element A2, the focal points of the incident element A1 and the exit element A2 coincide with each other; the incident element A1 is a glass ball with a diameter of 0.5-1.5 mm, and the exit element A2 is a plano-convex lens with its convex surface facing the exit direction of the light.

2. The 1535nm beam expander lens for a miniaturized laser rangefinder according to claim 1, characterized in that: The following relationship is satisfied: 1.18<M / T<1.17, where M is the magnification of the beam expander lens, and T is the total length of the beam expander lens.

3. The 1535nm beam expander lens for a miniaturized laser rangefinder according to claim 1 or 2, characterized in that: The convex surface of the emission element A2 is an aspherical surface.

4. The 1535nm beam expander lens for a miniaturized laser rangefinder according to claim 1 or 2, characterized in that: Along the incident direction of light, the two sides of the plano-convex lens are the incident surface and the exit surface respectively. The curvature radius of the incident surface is infinite, and the curvature radius of the exit surface is 7.62 mm±5%.

5. The 1535nm beam expander lens for a miniaturized laser rangefinder according to claim 1 or 2, characterized in that: The center thickness of the plano-convex lens is 2.5 mm ± 5%.

6. The 1535nm beam expander lens for a miniaturized laser rangefinder according to claim 1 or 2, characterized in that: The center distance between the incident element A1 and the exit element A2 is 13.793 mm±5%.

7. The 1535nm beam expander lens for a miniaturized laser rangefinder according to claim 1 or 2, characterized in that: The materials used for the incident element A1 and the output element A2 are both H-K9L.

8. The 1535nm beam expander lens for a miniaturized laser rangefinder according to claim 1 or 2, characterized in that: The diameter of the glass ball is 1 mm.

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