Large-magnification infrared beam expanding focusing lens

Abstract

The utility model belongs to the technical field of optics, and particularly relates to a large-magnification infrared beam expanding and focusing lens, which comprises a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged along the propagation direction of a light path, the total length of the large-magnification infrared beam expanding and focusing lens is 110mm, and the distance between the first lens and the second lens is 0mlt; l1lt; 2 mm; the distance between the second lens and the third lens is 23 mlt; l2lt; 25 mm; the distance between the third lens and the fourth lens is 52 mmlt; l3lt; 54mm, 54mm; the full field of view of the large-magnification infrared beam expanding and focusing lens is + / -0.1 degrees, the entrance pupil diameter is 60mm, and the exit pupil diameter is 7.5 mm. The total optical length of the lens is short, the number of the lenses is small, the lens has the 1550 nm wavelength signal transmitting and receiving functions at the same time, and the size and weight of an optical system are reduced; all the lenses adopt standard spherical lenses, so that the development and processing cost is reduced, and the processing, detection and adjustment difficulty of the lenses is reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of optics, and particularly relates to a high-magnification infrared beam expander focusing lens. Background Art

[0002] In the field of laser communication, an instrument needs to simultaneously satisfy the functions of signal reception and transmission with a common aperture. After the laser is received by a beam expander focusing lens (also known as an optical antenna), the light is subjected to a beam reduction effect to obtain a laser beam with a smaller diameter in front of the focusing lens. At the same time, when the laser is emitted through the beam expander focusing lens, the light is subjected to a beam expansion effect, and due to the existence of its divergence angle, the emitted light can form a larger light spot in the distance, enabling the instrument to receive the signal light well when receiving.

[0003] However, considering that a large-aperture receiving lens is required as much as possible for receiving signals and the diameter of the beam-reduced signal needs to be as small as possible, there is a need for a high magnification for the beam expander focusing lens. With the development of lasers, fiber lasers with a wavelength of 1550 nm are widely used. Since the wavelength of 1550 nm is in the communication band and has low loss in air propagation, a beam expander focusing lens with a wavelength of 1550 nm is required. At the same time, considering the miniaturization problem, the overall optical length of the beam expander focusing lens should be as small as possible. Summary of the Invention

[0004] The purpose of the utility model is to overcome the above deficiencies and provide a high-magnification infrared beam expander focusing lens, which can enable the lens to have the functions of signal transmission and reception at a wavelength of 1550 nm at the same time, and reduce the volume and weight of the optical system.

[0005] According to the technical solution provided by the utility model, a high-magnification infrared beam expander focusing lens includes a first lens, a second lens, a third lens, and a fourth lens sequentially arranged along the optical path propagation direction;

[0006] The first lens is a plano-convex lens with positive optical power, the radius of curvature of its front surface is 50 mm < R1 < 60 mm, and the radius of curvature of its rear surface is R2 is infinity; the central thickness of the first lens is 11 mm < d1 < 14 mm;

[0007] The second lens is a convex-concave lens with positive optical power, the radius of curvature of its front surface is 55 mm < R3 < 58 mm, and the radius of curvature of its rear surface is 95 mm < R4 < 100 mm; the central thickness of the second lens is 7 mm < d2 < 10 mm;

[0008] The third lens is a biconcave lens with a negative optical power. The radius of curvature of its front surface is -78 mm < R5 < -75 mm, and the radius of curvature of its rear surface is 50 mm < R6 < 53 mm; the central thickness of the third lens is 5 mm < d3 < 8 mm;

[0009] The fourth lens is a biconcave lens with a positive optical power. The radius of curvature of its front surface is -28 mm < R7 < -25 mm, and the radius of curvature of its rear surface is 20 mm < R8 < 23 mm (infinity); the central thickness of the fourth lens is 3 mm < d4 < 5 mm;

[0010] The total length of the large magnification infrared beam expander and focusing lens is 110 mm. The distance between the first lens and the second lens is 0 mm < L1 < 2 mm; the distance between the second lens and the third lens is 23 mm < L2 < 25 mm; the distance between the third lens and the fourth lens is 52 mm < L3 < 54 mm.

[0011] As a further improvement of the present utility model, the full field of view of the large magnification infrared beam expander and focusing lens is ±0.1°, the entrance pupil diameter is 60 mm, and the exit pupil diameter is 7.5 mm.

[0012] As a further improvement of the present utility model, the distance between the first lens and the second lens is 1 mm; the distance between the second lens and the third lens is 24.162 mm; the distance between the third lens and the fourth lens is 53.838 mm.

[0013] As a further improvement of the present utility model, both the first lens and the second lens are positive lenses, the third lens and the fourth lens are negative lenses, and the beam expander and focusing lens adopts a front-mounted entrance pupil arrangement, and the entrance pupil is at the first lens.

[0014] As a further improvement of the present utility model, the radius of curvature of the front surface of the first lens is 52.909 mm, and the radius of curvature of the rear surface is infinity; the central thickness of the first lens is 13 mm;

[0015] The radius of curvature of the front surface of the second lens is 56.054 mm, and the radius of curvature of the rear surface is 96.703 mm; the central thickness of the second lens is 8 mm;

[0016] The radius of curvature of the front surface of the third lens is -76.454 mm, and the radius of curvature of the rear surface is 52.667 mm; the central thickness of the third lens is 6 mm;

[0017] The fourth lens is a plano-convex lens. The radius of curvature of the front surface is -26.728 mm, and the radius of curvature of the rear surface is 20.548 mm; the central thickness of the fourth lens is 4 mm.

[0018] As a further improvement of the present utility model, the first lens 1 is made of H-K9L glass; the second lens is made of H-F4 glass; the third lens 3 is made of H-F4 glass; the fourth lens 4 is made of H-K9L glass.

[0019] As a further improvement of the present utility model, the first lens, the second lens, the third lens and the fourth lens are all standard spherical lenses.

[0020] The beneficial effects of the present utility model are as follows:

[0021] Compared with the prior art, the large magnification infrared beam expander focusing lens of the present utility model has the following advantages:

[0022] 1. The overall optical length of the lens in this application is shorter, the number of lenses is less, and the lens realizes an achromatic design at the same time, reducing the volume and weight of the optical system;

[0023] 2. All the lenses adopt standard spherical lenses, reducing the research and development and processing costs, and reducing the difficulty of lens processing, detection and alignment;

[0024] 3. The imaging quality of the optical system is good, reducing the tracking error, and meeting the requirements of high-probability capture and high-precision tracking. Description of the Drawings

[0025] Figure 1 It is a schematic structural diagram of the large magnification infrared beam expander focusing lens of the present utility model.

[0026] Figure 2 It is a standard spot diagram of the large magnification infrared beam expander focusing lens of the present utility model.

[0027] Figure 3 It is a wavefront aberration diagram of the large magnification infrared beam expander focusing lens of the present utility model.

[0028] Description of the reference numerals: 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens 4. Detailed Embodiments

[0029] The present utility model will be further described below in conjunction with the embodiments in the drawings:

[0030] As shown in the figure, a large magnification infrared beam expander focusing lens includes a first lens 1, a second lens 2, a third lens 3 and a fourth lens 4 arranged in sequence along the optical path propagation direction;

[0031] The first lens 1 is a plano-convex lens with positive optical power, the curvature radius of its front surface is 50mm < R1 < 60mm, and the curvature radius of its rear surface R2 is infinite; the central thickness of the first lens 1 is 11mm < d1 < 14mm;

[0032] The second lens 2 is a convex-concave lens with a positive optical power. The radius of curvature of its front surface is 55 mm < R3 < 58 mm, and the radius of curvature of its rear surface is 95 mm < R4 < 100 mm; the central thickness of the second lens 2 is 7 mm < d2 < 10 mm;

[0033] The third lens 3 is a biconcave lens with a negative optical power. The radius of curvature of its front surface is -78 mm < R5 < -75 mm, and the radius of curvature of its rear surface is 50 mm < R6 < 53 mm; the central thickness of the third lens 3 is 5 mm < d3 < 8 mm;

[0034] The fourth lens 4 is a biconcave lens with a positive optical power. The radius of curvature of its front surface is -28 mm < R7 < -25 mm, and the radius of curvature of its rear surface 20 mm < R8 < 23 mm is infinite; the central thickness of the fourth lens 4 is 3 mm < d4 < 5 mm;

[0035] The total length of the large magnification infrared beam expander and focusing lens is 110 mm. The distance between the first lens 1 and the second lens 2 is 0 mm < L1 < 2 mm; the distance between the second lens 2 and the third lens 3 is 23 mm < L2 < 25 mm; the distance between the third lens 3 and the fourth lens 4 is 52 mm < L3 < 54 mm.

[0036] The full field of view of the large magnification infrared beam expander and focusing lens is ±0.1°, the entrance pupil diameter is 60 mm, the exit pupil diameter is 7.5 mm, and the lens of this application realizes 8-fold beam expansion and contraction, meeting the requirements of the large magnification infrared beam expander and focusing lens.

[0037] Embodiment

[0038] As Figure 1 shown, a large magnification infrared beam expander and focusing lens includes a first lens 1, a second lens 2, a third lens 3, and a fourth lens 4 arranged in sequence along the optical path propagation direction.

[0039] The operating wavelength of the beam expander and focusing lens is selected as the 1550 nm band. This band is a safe band for the human eye and is far from the visible light band, reducing the serious interference of visible light, sunlight, and ground stray light on the beacon light receiving optical path, and facilitating the aiming, acquisition, and tracking processes of the communication system;

[0040] In the case of a beam expander and focusing lens of the same type with a beam expansion (contraction) magnification of 8 times, the total length of the lens is mostly about 190 mm. The total length of the beam expander and focusing lens of this application is 110 mm, which is lower than the average total length. It mainly realizes the optical total length as small as possible by the central thickness of the four lenses and the distance between every two of them;

[0041] The distance between the first lens 1 and the second lens 2 is 1 mm; the distance between the second lens 2 and the third lens 3 is 24.162 mm; the distance between the third lens 3 and the fourth lens 4 is 53.838 mm.

[0042] Both the first lens 1 and the second lens 2 are positive lenses, the third lens 3 and the fourth lens 4 are negative lenses, and the beam expander and focusing lens adopts a front - placed entrance pupil layout, and the entrance pupil is at the first lens 1.

[0043] The radius of curvature of the front surface of the first lens 1 is 52.909 mm, and the radius of curvature of the rear surface is infinity; the central thickness of the first lens 1 is 13 mm;

[0044] The radius of curvature of the front surface of the second lens 2 is 56.054 mm, and the radius of curvature of the rear surface is 96.703 mm; the central thickness of the second lens 2 is 8 mm;

[0045] The radius of curvature of the front surface of the third lens 3 is - 76.454 mm, and the radius of curvature of the rear surface is 52.667 mm; the central thickness of the third lens 3 is 6 mm;

[0046] The fourth lens 4 is a plano - convex lens, the radius of curvature of the front surface is - 26.728 mm, and the radius of curvature of the rear surface is 20.548 mm; the central thickness of the fourth lens 4 is 4 mm.

[0047] The first lens 1 uses H - K9L glass; the second lens 2 uses H - F4 glass; the third lens 3 uses H - F4 glass; the fourth lens 4 uses H - K9L glass. With such a design, the application of different glass materials can effectively reduce the chromatic aberration of the optical system and improve the optical imaging quality.

[0048] The first lens 1, the second lens 2, the third lens 3 and the fourth lens 4 are all standard spherical lenses, which reduces the research and development and processing costs and reduces the difficulties in lens processing, detection and alignment.

[0049] As Figure 2 It is the standard spot diagram of the high - magnification infrared beam expander and focusing lens. It can be seen from the figure that within the full field of view, the beam divergence angle is better than 0.1 mrad, less than the Airy disk radius, and the imaging effect is good.

[0050] As Figure 3 It is the wavefront aberration diagram of the high - magnification infrared beam expander and focusing lens. It can be seen from the figure that the wavefront aberration of the central field of view of the beam expander and focusing lens is 0.0143 wavelengths, and the peak - to - valley ratio is 0.0576 wavelengths. The wavefront aberration is less than 0.1. Therefore, the high - magnification infrared beam expander and focusing lens has good imaging quality and beam expansion effect.

[0051] The optical structure of the high-magnification infrared beam expander and focusing lens of this application is relatively simple. It adopts a four-lens optical system, which reduces the volume and weight of the optical system and is convenient for installation, adjustment and testing. All the lenses of the optical system use standard spherical lenses, which reduces the research and development and processing costs. The beam expander and focusing lens has a relatively large aperture, achieving 8-fold beam expansion and contraction. The divergence angle of the output beam is very small, and the imaging quality is good, meeting the imaging requirements.

[0052] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A large magnification infrared beam expander and focusing lens, characterized in that It includes a first lens (1), a second lens (2), a third lens (3) and a fourth lens (4) arranged in sequence along the optical path propagation direction; The first lens (1) is a plano-convex lens with a positive optical power. The radius of curvature of its front surface is 50mm < R1 < 60mm, and the radius of curvature of its rear surface is R2 = infinity; the central thickness of the first lens (1) is 11mm < d1 < 14mm; The second lens (2) is a convex-concave lens with a positive optical power. The radius of curvature of its front surface is 55mm < R3 < 58mm, and the radius of curvature of its rear surface is 95mm < R4 < 100mm; the central thickness of the second lens (2) is 7mm < d2 < 10mm; The third lens (3) is a double-concave lens with a negative optical power. The radius of curvature of its front surface is -78mm < R5 < -75mm, and the radius of curvature of its rear surface is 50mm < R6 < 53mm; the central thickness of the third lens 3 is 5mm < d3 < 8mm; The fourth lens (4) is a double-concave lens with a positive optical power. The radius of curvature of its front surface is -28mm < R7 < -25mm, and the radius of curvature of its rear surface 20mm < R8 < 23mm = infinity; the central thickness of the fourth lens 4 is 3mm < d4 < 5mm; The total length of the large magnification infrared beam expander and focusing lens is 110mm. The distance between the first lens (1) and the second lens (2) is 0mm < L1 < 2mm; the distance between the second lens (2) and the third lens (3) is 23mm < L2 < 25mm; the distance between the third lens (3) and the fourth lens (4) is 52mm < L3 < 54mm.

2. The large magnification infrared beam expander focusing lens according to claim 1, wherein The full field of view of the large magnification infrared beam expander and focusing lens is ±0.1°, the entrance pupil diameter is 60mm, and the exit pupil diameter is 7.5mm.

3. The large magnification infrared beam expanding and focusing lens according to claim 1, wherein, The distance between the first lens (1) and the second lens (2) is 1mm; the distance between the second lens (2) and the third lens (3) is 24.162mm; the distance between the third lens (3) and the fourth lens (4) is 53.838mm.

4. The large magnification infrared beam expander focusing lens according to claim 1, wherein, Both the first lens (1) and the second lens (2) are positive lenses, the third lens (3) and the fourth lens (4) are negative lenses, and the beam expander and focusing lens adopts a front-mounted entrance pupil arrangement, and the entrance pupil is at the first lens (1).

5. The large magnification infrared beam expander focusing lens according to claim 1, characterized in that, The radius of curvature of the front surface of the first lens (1) is 52.909mm, and the radius of curvature of the rear surface is infinity; the central thickness of the first lens (1) is 13mm; The radius of curvature of the front surface of the second lens (2) is 56.054mm, and the radius of curvature of the rear surface is 96.703mm; the central thickness of the second lens (2) is 8mm; The radius of curvature of the front surface of the third lens (3) is -76.454mm, and the radius of curvature of the rear surface is 52.667mm; the central thickness of the third lens (3) is 6mm; The fourth lens (4) is a plano-convex lens, with the radius of curvature of the front surface being -26.728 mm and the radius of curvature of the rear surface being 20.548 mm; the central thickness of the fourth lens (4) is 4 mm.

6. The large magnification infrared beam expander focusing lens according to claim 1, wherein, The first lens (1) is made of H-K9L glass; the second lens (2) is made of H-F4 glass; the third lens (3) is made of H-F4 glass; the fourth lens (4) is made of H-K9L glass.

7. The large magnification infrared beam expander focusing lens according to claim 1, wherein, The first lens (1), the second lens (2), the third lens (3) and the fourth lens (4) are all standard spherical lenses.

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