A collimating lens for vehicle-mounted fisheye camera MTF test

Abstract

The present application relates to a kind of vehicle-mounted fish-eye camera MTF test collimating lens, belong to the field of photoelectric testing instrument design.The technical problem of existing vehicle-mounted fish-eye lens transmission function test equipment needing foreign import, high cost of matching equipment is solved.The collimating lens of the present application includes aperture diaphragm, first lens, second lens, third lens, fourth lens, imaging plane arranged in turn along the direction of light propagation;The light emitted by the object arranged at aperture diaphragm reaches imaging plane after first lens, second lens, third lens and fourth lens in turn;First lens is convex-concave positive lens, second lens is concave-convex negative lens, third lens is concave-convex negative lens, and fourth lens is concave-convex positive lens.The vehicle-mounted fish-eye camera MTF test collimating lens of the present application can provide infinite target when used for vehicle-mounted fish-eye lens MTF test, and the collimating lens has large tolerance limit, is easy to process and adjust, has low processing cost and high test efficiency.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic testing instrument design, specifically relating to a collimating lens for MTF testing of a vehicle-mounted fisheye camera. Background Technology

[0002] With its core advantages of ultra-wide field of view (FOV typically ≥180°), short focal length, and panoramic imaging, the automotive fisheye lens has become a key component in automotive camera systems for achieving blind-spot-free perception. Its applications are highly focused on scenarios such as vehicle surrounding environment monitoring, panoramic fusion, and full-coverage in-vehicle monitoring. A single fisheye lens can cover a large area on one side of the vehicle, and four fisheye lenses combined with algorithms can stitch together a 360° panoramic image of the vehicle's surroundings, accurately capturing pedestrians, curbs, low obstacles, etc., around the vehicle, completely eliminating close-range blind spots when reversing or meeting oncoming traffic in narrow roads.

[0003] However, existing vehicle-mounted fisheye lens transmission testing equipment does require importation from abroad, and the cost of supporting equipment is high. Summary of the Invention

[0004] This invention aims to solve the technical problems in the prior art by providing a collimating lens for testing the MTF (Mean Transmission Test) of a vehicle-mounted fisheye camera. When used for MTF testing of a vehicle-mounted fisheye camera, the collimating lens of this invention can provide a target at infinity. This collimating lens has loose adjustment tolerances, low manufacturing costs, and high testing efficiency.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0006] A collimating lens for MTF testing of a vehicle-mounted fisheye camera includes an aperture stop, a first lens, a second lens, a third lens, a fourth lens, and an imaging plane arranged sequentially along the optical path propagation direction.

[0007] The first lens is a convex-concave positive lens, the second lens is a concave-convex negative lens, the third lens is a concave-convex negative lens, and the fourth lens is a concave-convex positive lens.

[0008] The light emitted by the object set at the aperture stop passes sequentially through the first lens incident surface and the first lens exit surface of the first lens, the second lens incident surface and the second lens exit surface of the second lens, the third lens incident surface and the third lens exit surface of the third lens, and the fourth lens incident surface and the fourth lens exit surface of the fourth lens before reaching the imaging plane.

[0009] The radius of curvature of the incident surface of the first lens is 307.566±0.2mm, and the radius of curvature of the exit surface of the first lens is -49.376±0.05mm; the radius of curvature of the incident surface of the second lens is -38.796±0.05mm, and the radius of curvature of the exit surface of the second lens is -74.378±0.05mm; the radius of curvature of the incident surface of the third lens is -45.295±0.05mm, and the radius of curvature of the exit surface of the third lens is -76.291±0.05mm; the radius of curvature of the incident surface of the fourth lens is -215.936±0.2mm, and the radius of curvature of the exit surface of the fourth lens is -51.015±0.05mm.

[0010] In the above technical solution, the aperture stop is located at 88mm±0.1mm at the front end of the first lens; the center interval between the first lens and the second lens is 7±0.01mm; the center interval between the second lens and the third lens is 2.6±0.01mm; the center interval between the third lens and the fourth lens is 6.4±0.01mm; and the center interval between the fourth lens and the imaging plane is 100±0.1mm.

[0011] In the above technical solution, the center thickness of the first lens is 10.0±0.01mm; the center thickness of the second lens is 2.0±0.01mm; the center thickness of the third lens is 2.0±0.01mm; and the center thickness of the fourth lens is 10.0±0.01mm.

[0012] In the above technical solution, the refractive index of the material of the first lens is 1.5666511680~1.5746320401, the refractive index of the material of the second lens is 1.6491819206~1.6657249034, the refractive index of the material of the third lens is 1.6421003810~1.6612399780, and the refractive index of the material of the fourth lens is 1.5901712007~1.5988452190.

[0013] In the above technical solution, the material of the first lens is H-ZPK7, the material of the second lens is H-TF5, the material of the third lens is H-ZF1, and the material of the fourth lens is H-ZPK5.

[0014] In the above technical solution, the wavelength range of the collimating lens for MTF testing of the vehicle-mounted fisheye camera is 0.486µm to 0.656µm.

[0015] In the above technical solution, the field of view of the collimating lens for MTF testing of the vehicle-mounted fisheye camera is ±12.6°.

[0016] In the above technical solution, the entrance pupil diameter of the collimating lens for MTF testing of the vehicle-mounted fisheye camera is 4mm.

[0017] The beneficial effects of this invention are:

[0018] The collimating lens for MTF testing of the vehicle-mounted fisheye camera of the present invention, based on aberration theory, uses the matching of positive and negative optical power of multiple lenses, appropriate lens materials, radius of curvature and spacing to correct field curvature, astigmatism, distortion and magnification chromatic aberration. The imaging quality of this collimating lens is close to the diffraction limit and can meet the usage requirements of optical transfer function measuring instruments.

[0019] The collimating lens for MTF testing of a vehicle-mounted fisheye camera of the present invention can provide a target at infinity when used for MTF testing of a vehicle-mounted fisheye lens. The collimating lens has a large tolerance, is easy to manufacture and adjust, has low manufacturing cost, and high testing efficiency. Attached Figure Description

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0021] Figure 1 This is a schematic diagram of the optical structure of the collimating lens for MTF testing of the vehicle-mounted fisheye camera of the present invention.

[0022] Figure 2 This is a blur pattern of the collimating lens used for MTF testing of the vehicle-mounted fisheye camera of the present invention.

[0023] Figure 3 The field curvature and distortion diagrams are for the collimating lens of the MTF test of the vehicle-mounted fisheye camera of the present invention.

[0024] Figure 4 This is an optical transfer function curve of the collimating lens for MTF testing of the vehicle-mounted fisheye camera of the present invention. In the figure, OTF on the vertical axis refers to the optical transfer function.

[0025] The reference numerals in the figure are:

[0026] 1-First lens, 2-Second lens, 3-Third lens, 4-Fourth lens, 5-Aperture stop, 6-Imaging plane;

[0027] S1 - First lens incident surface, S2 - First lens exit surface, S3 - Second lens incident surface, S4 - Second lens exit surface, S5 - Third lens incident surface, S6 - Third lens exit surface, S7 - Fourth lens incident surface, S8 - Fourth lens exit surface. Detailed Implementation

[0028] This invention provides a collimating lens for testing the MTF of a vehicle-mounted fisheye camera, comprising an aperture stop 5, a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, and an imaging plane 6 arranged sequentially along the optical path propagation direction; the first lens 1 is a convex-concave positive lens, the second lens 2 is a concave-convex negative lens, the third lens 3 is a concave-convex negative lens, and the fourth lens 4 is a concave-convex positive lens; the light emitted from an object positioned at the aperture stop 5 passes sequentially through the first lens incident surface S1 and the first lens exit surface S2 of the first lens 1, the second lens incident surface S3 and the second lens exit surface S4 of the second lens 2, the third lens incident surface S5 and the third lens exit surface S6 of the third lens 3, and the fourth lens incident surface S7 and the fourth lens exit surface S8 of the fourth lens 4 before reaching the imaging plane 6.

[0029] The collimating lens for testing the MTF of the vehicle-mounted fisheye camera of the present invention is used in which a knife-edge target is placed on the imaging plane 6 and illuminated by a visible light source. The target is projected onto the front end of the collimating lens through the collimating lens of the present invention. The vehicle-mounted fisheye camera under test is placed 88mm away from the front end of the first lens 1 of the collimating lens and receives the target image from the imaging plane 6 of the collimating lens. The MTF of the vehicle-mounted fisheye camera under test is calculated by analyzing the target image.

[0030] The vehicle-mounted fisheye camera MTF testing collimating lens of the present invention is a visible light achromatic optical imaging lens with a wavelength range of 0.486µm to 0.656µm and a field of view of ±12.6°. It adopts an object-side infinity design. The aperture stop 5 is placed 88mm in front of the first surface (i.e., the first lens incident surface S1 of the first lens 1). The aperture stop 5 determines the entrance pupil diameter of the collimating lens system. The size of the image formed by the aperture stop 5 in the object space is the entrance pupil diameter, which is 4mm.

[0031] The aperture stop 5 is located 88mm from the front end of the first lens 1. The vehicle-mounted fisheye camera under test is placed here. The entrance pupil diameter of the vehicle-mounted fisheye camera under test is generally 2mm-3mm. The collimating lens of this invention is designed with an entrance pupil diameter of 4mm, which can fill the entrance pupil diameter of the vehicle-mounted fisheye camera under test.

[0032] This invention uses four materials with different dispersion coefficients: the first material has a refractive index of 1.5666511680~1.5746320401, the second material has a refractive index of 1.6491819206~1.6657249034, the third material has a refractive index of 1.6421003810~1.6612399780, and the fourth material has a refractive index of 1.5901712007~1.5988452190.

[0033] The first material mentioned above is H-ZPK7, the second material is H-TF5, the third material is H-ZF1, and the fourth material is H-ZPK5.

[0034] The first lens 1 uses the first material, the second lens 2 uses the second material, the third lens 3 uses the third material, and the fourth lens 4 uses the fourth material.

[0035] Along the direction of light propagation, the two sides of the first lens 1 are the first lens incident surface S1 and the first lens exit surface S2; the two sides of the second lens 2 are the second lens incident surface S3 and the second lens exit surface S4; the two sides of the third lens 3 are the third lens incident surface S5 and the third lens exit surface S6; and the two sides of the fourth lens 4 are the fourth lens incident surface S7 and the fourth lens exit surface S8.

[0036] The vehicle-mounted fisheye camera MTF testing collimating lens of the present invention belongs to a large field of view and small relative aperture optical system. It mainly considers field curvature, astigmatism, distortion and magnification chromatic aberration related to the field of view. Spherical aberration and positional chromatic aberration are relatively small. The present invention uses 4 lenses with positive and negative optical power matching, and appropriate lens materials, radii of curvature and spacing to correct positional field curvature, astigmatism, distortion and magnification chromatic aberration.

[0037] To further ensure image quality, the radius of curvature of the first lens incident surface S1 is 307.566±0.2mm, and the radius of curvature of the first lens exit surface S2 is -49.376±0.05mm; the radius of curvature of the second lens incident surface S3 is -38.796±0.05mm, and the radius of curvature of the second lens exit surface S4 is -74.378±0.05mm; the radius of curvature of the third lens incident surface S5 is -45.295±0.05mm, and the radius of curvature of the third lens exit surface S6 is -76.291±0.05mm; the radius of curvature of the fourth lens incident surface S7 is -215.936±0.2mm, and the radius of curvature of the fourth lens exit surface S8 is -51.015±0.05mm.

[0038] like Figure 1 As shown, light propagates from left to right. If the center of curvature of the radius of curvature is to the right of the vertex of the surface, the radius of curvature is positive; if the center of curvature of the radius of curvature is to the left of the vertex of the surface, the radius of curvature is negative.

[0039] To better ensure image quality, the collimating lens for MTF testing of the vehicle-mounted fisheye camera of this invention has an object distance of 88±0.1mm; the center distance between the first lens 1 and the second lens 2 is 7±0.01mm; the center distance between the second lens 2 and the third lens 3 is 2.6±0.01mm; the center distance between the third lens 3 and the fourth lens 4 is 6.4±0.01mm; and the center distance between the fourth lens 4 and the imaging plane 6 is 100±0.1mm.

[0040] The center thickness of the first lens 1 is 10.0±0.01mm; the center thickness of the second lens 2 is 2.0±0.01mm; the center thickness of the third lens 3 is 2.0±0.01mm; and the center thickness of the fourth lens 4 is 10.0±0.01mm.

[0041] Any techniques not mentioned in this invention are based on existing technologies.

[0042] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0043] Example

[0044] like Figure 1 As shown, the collimating lens for MTF testing of the vehicle-mounted fisheye camera of the present invention, from left to right, consists of an aperture stop 5, a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, and an imaging plane 6. The aperture stop 5 is positioned 88mm to the left of the first lens 1. During testing, the vehicle-mounted fisheye camera under test is placed at the aperture stop 5, and the blade target is placed 100mm to the right of the last side of the collimating lens of the present invention, i.e., on the imaging plane 6.

[0045] Along the direction of light propagation from left to right, the two surfaces of the first lens 1 are, in sequence, the first lens incident surface S1 and the first lens exit surface S2; the two surfaces of the second lens 2 are, in sequence, the second lens incident surface S3 and the second lens exit surface S4; the two surfaces of the third lens 3 are, in sequence, the third lens incident surface S5 and the third lens exit surface S6; and the two surfaces of the fourth lens 4 are, in sequence, the fourth lens incident surface S7 and the fourth lens exit surface S8. The radius of curvature of the first lens incident surface S1 is 307.566 mm, and the first lens exit surface... The radius of curvature of S2 is -49.376 mm; the radius of curvature of the second lens incident surface S3 is -38.796 mm, and the radius of curvature of the second lens exit surface S4 is -74.378 mm; the radius of curvature of the third lens incident surface S5 is -45.295 mm, and the radius of curvature of the third lens exit surface S6 is -76.291 mm; the radius of curvature of the fourth lens incident surface S7 is -215.936 mm, and the radius of curvature of the fourth lens exit surface S8 is -51.015 mm.

[0046] The object distance of the collimating lens is 88.0 mm; the center distance between the first lens 1 and the second lens 2 is 7.0 mm; the center distance between the second lens 2 and the third lens 3 is 2.6 mm; the center distance between the third lens 3 and the fourth lens 4 is 6.4 mm; and the center distance between the fourth lens 4 and the imaging plane 6 is 100.0 mm.

[0047] The center thickness of the first lens 1 is 10.0 mm; the center thickness of the second lens 2 is 2.0 mm; the center thickness of the third lens 3 is 2.0 mm; and the center thickness of the fourth lens 4 is 10.0 mm.

[0048] The first lens 1 is made of material H-ZPK7, the second lens 2 is made of material H-TF5, the third lens 3 is made of material H-ZF1, and the fourth lens 4 is made of material H-ZPK5.

[0049] Table 1 shows the optical element parameters of the collimating lens of the present invention.

[0050]

[0051] The optical parameters of the collimating lens for MTF testing of the vehicle-mounted fisheye camera of the present invention are as follows:

[0052] Focal length: 112mm, wavelength: 0.486µm~0.656µm, entrance pupil diameter: 4mm, object distance: 88mm, image distance: 100mm.

[0053] The collimating lens for MTF testing of the vehicle-mounted fisheye camera of the present invention is a visible light band lens that emits visible light from a knife-edge target. When applied to an optical transfer function measuring instrument, it is used to test the imaging quality of the vehicle-mounted fisheye camera.

[0054] Figure 2 This is a blur pattern of the collimating lens for MTF testing of the vehicle-mounted fisheye camera of the present invention, from... Figure 2 The blur pattern shows that the blur pattern in each field of view of the collimating lens system of the present invention is well corrected, and the blur pattern radius is within the Airy disk. The RMS value of the on-axis blur pattern radius is 0.501µm, and the RMS value of the blur pattern radius at the maximum off-axis field of view is 10.734µm.

[0055] Figure 3 The field curvature and distortion diagrams are obtained from the collimating lens of the MTF test for the vehicle-mounted fisheye camera of this invention. Figure 3 As can be seen from the field curvature and distortion diagrams, the maximum field curvature of the collimating lens system of the present invention is 0.93mm, and the maximum distortion is 2.97%.

[0056] Figure 4 This is an optical transfer function curve of the collimating lens for MTF testing of the vehicle-mounted fisheye camera of the present invention. Figure 4 As can be seen from the optical transfer function curves, the optical transfer function of the collimating lens system of the present invention is close to the diffraction limit in each field of view.

[0057] In summary, the imaging quality of the collimating lens for testing the MTF of the vehicle-mounted fisheye camera of the present invention can meet the requirements of the optical transfer function measuring instrument and can be used to test the imaging quality of the vehicle-mounted fisheye camera.

[0058] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A collimating lens for MTF testing of a vehicle-mounted fisheye camera, characterized in that, It includes an aperture stop (5), a first lens (1), a second lens (2), a third lens (3), a fourth lens (4), and an imaging plane (6) arranged sequentially along the optical path propagation direction; The first lens (1) is a convex-concave positive lens, the second lens (2) is a concave-convex negative lens, the third lens (3) is a concave-convex negative lens, and the fourth lens (4) is a concave-convex positive lens. The light emitted by the object set at the aperture stop (5) passes sequentially through the first lens incident surface (S1) and the first lens exit surface (S2) of the first lens (1), the second lens incident surface (S3) and the second lens exit surface (S4) of the second lens (2), the third lens incident surface (S5) and the third lens exit surface (S6) of the third lens (3), and the fourth lens incident surface (S7) and the fourth lens exit surface (S8) of the fourth lens (4) before reaching the imaging plane (6). The radius of curvature of the first lens incident surface (S1) is 307.566±0.2mm, and the radius of curvature of the first lens exit surface (S2) is -49.376±0.05mm; the radius of curvature of the second lens incident surface (S3) is -38.796±0.05mm, and the radius of curvature of the second lens exit surface (S4) is -74.378±0.05mm; the radius of curvature of the third lens incident surface (S5) is -45.295±0.05mm, and the radius of curvature of the third lens exit surface (S6) is -76.291±0.05mm; the radius of curvature of the fourth lens incident surface (S7) is -215.936±0.2mm, and the radius of curvature of the fourth lens exit surface (S8) is -51.015±0.05mm.

2. The collimating lens for MTF testing of a vehicle-mounted fisheye camera according to claim 1, characterized in that, The aperture stop (5) is located 88 mm ± 0.1 mm from the front end of the first lens (1); the center interval between the first lens (1) and the second lens (2) is 7 ± 0.01 mm; the center interval between the second lens (2) and the third lens (3) is 2.6 ± 0.01 mm; the center interval between the third lens (3) and the fourth lens (4) is 6.4 ± 0.01 mm; and the center interval between the fourth lens (4) and the imaging plane (6) is 100 ± 0.1 mm.

3. The collimating lens for MTF testing of a vehicle-mounted fisheye camera according to claim 1, characterized in that, The center thickness of the first lens (1) is 10.0±0.01mm; the center thickness of the second lens (2) is 2.0±0.01mm; the center thickness of the third lens (3) is 2.0±0.01mm; and the center thickness of the fourth lens (4) is 10.0±0.01mm.

4. The collimating lens for MTF testing of a vehicle-mounted fisheye camera according to claim 1, characterized in that, The refractive index of the material of the first lens (1) is 1.5666511680~1.5746320401, the refractive index of the material of the second lens (2) is 1.6491819206~1.6657249034, the refractive index of the material of the third lens (3) is 1.6421003810~1.6612399780, and the refractive index of the material of the fourth lens (4) is 1.5901712007~1.5988452190.

5. The collimating lens for MTF testing of a vehicle-mounted fisheye camera according to claim 4, characterized in that, The material of the first lens (1) is H-ZPK7, the material of the second lens (2) is H-TF5, the material of the third lens (3) is H-ZF1, and the material of the fourth lens (4) is H-ZPK5.

6. The collimating lens for MTF testing of a vehicle-mounted fisheye camera according to claim 1, characterized in that, The collimating lens has a wavelength range of 0.486µm to 0.656µm.

7. The collimating lens for MTF testing of a vehicle-mounted fisheye camera according to claim 1, characterized in that, The collimating lens has a field of view of ±12.6°.

8. The collimating lens for MTF testing of a vehicle-mounted fisheye camera according to claim 1, characterized in that, The entrance pupil diameter of this collimating lens is 4mm.

Images