A large field of view object side telecentric projection imaging method and lens for vehicle lamp

Abstract

The application discloses a large-view-field object-side telecentric projection imaging method and a lens for a vehicle lamp. Incident light rays are converged through two large-aperture meniscus lens; the converged light rays are reduced in size and aberration through a double cemented lens group composed of a first negative double-concave lens and a first positive double-convex lens; the light rays are further converged through a second negative meniscus lens, so that the light rays all enter a diaphragm; chromatic aberration is corrected through three cemented lenses, and aberration is further reduced, and a spherical aberration can be corrected since the aperture diaphragm is located on the object side of the three cemented lenses; the light path is further converged through two double-convex lens groups, and distortion is reduced, the light rays enter a TIR total reflection prism, pass through a protective glass, and are clearly imaged on a DMD image plane. The imaging method provided by the application can realize object-side telecentric projection imaging under a large view field through the cooperation of conditional expressions and positive and negative focal lengths between the lenses, and the imaging is high in definition.

Description

TECHNICAL FIELD

[0001] The present application relates to a large field of view object far field of view projection lens for vehicle lamp and its imaging method, belonging to the field of optical projection technology. BACKGROUND

[0002] In recent years, laser white light source is the development trend of illumination light source, and intelligent pixel headlamp is the development direction of vehicle lighting system. Using laser white light source as light source, combining DLP projection technology, sensor and intelligent algorithm, the full digital control of headlamp is realized, and the light beam can be adjusted at the level of million pixels. According to the detection system carried in the vehicle, the road environment, pedestrians and vehicles are intelligently identified, and the light beam is adjusted in time after rapid analysis, so as to realize the projection of road information, pedestrian identification information, speed limit, road sign and other traffic sign projection functions.

[0003] As an important device of intelligent pixel headlamp, the projection lens is the key to realize the road projection function, but it is limited by many conditions: the laser white light source as the light source leads to high temperature in the vehicle lamp, the material of the projection lens is limited, and the material that can withstand high and low temperature changes and will not deform the lens must be used; the road surface is wide, and the field of view angle range is large; due to the small space in the vehicle lamp, the projection lens needs to be compact in structure, large in light quantity, high and uniform in relative luminance; at the same time, the vehicle lamp also has the projection imaging function, and the projected picture quality has certain requirements; the cost of the vehicle lamp projection lens is limited due to its large application quantity. SUMMARY

[0004] In view of the deficiencies in the prior art, the present application provides a large field of view object far field of view projection lens for vehicle lamp, which is compact in structure, low in cost, high and uniform in relative luminance, and clear in picture quality.

[0005] To achieve the above-mentioned application purpose, the technical scheme adopted by the present application is a large field of view object far field of view projection imaging method for vehicle lamp, comprising the following steps:

[0006] 1. Converging light

[0007] Two large aperture meniscus lenses are used to converge the incident light, and according to the direction of light incidence, the first positive meniscus lens (1) and the first negative meniscus lens (2) are sequentially arranged along the optical axis; the first positive meniscus lens has a light aperture of 70-71mm and a thickness of 14-15mm; the first negative meniscus lens has a light aperture of 61.5-62.5mm and a thickness of 4.5-5.5mm;

[0008] 2. Reduce aberration

[0009] The converged light rays are reduced in aberration by a double cemented lens group; the double cemented lens is composed of a first negative double-concave lens (3) and a first positive double-convex lens (4), the first negative double-concave lens has a light aperture of 30.5-31.5 mm and a thickness of 4-5 mm; the first positive double-convex lens has a light aperture of 28.5-29.5 mm and a thickness of 9.5-10.5 mm;

[0010] 3. Further converging light rays

[0011] The second negative meniscus lens (5) is used to further converge light rays so that all the light rays enter the diaphragm; the second negative meniscus lens has a light aperture of 21-22 mm and a thickness of 9.5-10.5 mm;

[0012] 4. Correcting chromatic aberration and spherical aberration and reducing aberration

[0013] The three cemented lens groups are used to correct chromatic aberration, further reduce aberration, correct spherical aberration and correct spherical aberration of the aperture diaphragm; the three cemented lens groups in the order of light incidence direction comprise a first positive double-concave lens (7) having a light aperture of 7.5-8.5 mm and a thickness of 2.5-3.5 mm, a third negative meniscus lens (8) having a light aperture of 11-12 mm and a thickness of 7-8 mm, and a second positive double-convex lens (9) having a light aperture of 15.5-16.5 mm and a thickness of 6.5-7.5 mm; the aperture diaphragm (6) is arranged on the object side of the first positive double-concave lens (7);

[0014] 5. Converging light path, reducing distortion and clear imaging

[0015] The two double-convex lens groups are used to converge light path and reduce distortion; the double-convex lens groups comprise a third positive double-convex lens (10) having a light aperture of 22-23 mm and a thickness of 4.5-5.5 mm and a fourth positive double-convex lens (11) having a light aperture of 23-24 mm and a thickness of 4.5-5.5 mm; the converged light rays enter the TIR total reflection prism (12), pass through the protective glass (13) and are clearly imaged on the DMD image plane (14).

[0016] The technical scheme of the present application also provides a large field of view object far field of view projection lens for vehicle lamp, which is a double Gauss coaxial structure, and the optical elements include, in sequence along the light incident direction, a first positive meniscus lens, a first negative meniscus lens, a first negative double concave lens, a first positive double convex lens, a second negative meniscus lens, an aperture diaphragm, a first positive double concave lens, a third negative meniscus lens, a second positive double convex lens, a third positive double convex lens, a fourth positive double convex lens, a TIR prism, a protective glass and a digital micro-mirror device (DMD); wherein the first negative double concave lens and the first positive double convex lens are glued to form a double glued lens group; the first positive double concave lens, the third negative meniscus lens and the second positive double convex lens are glued to form a three-glued lens group; and the aperture diaphragm is arranged on the object side of the first positive double concave lens.

[0017] The light transmission aperture of the first positive meniscus lens is 70-71mm, and the thickness is 14-15mm; the light transmission aperture of the first negative meniscus lens is 61.5-62.5mm, and the thickness is 4.5-5.5mm; the light transmission aperture of the first negative double concave lens is 30.5-31.5mm, and the thickness is 4-5mm; the light transmission aperture of the first positive double convex lens is 28.5-29.5mm, and the thickness is 9.5-10.5mm; the light transmission aperture of the second negative meniscus lens is 21-22mm, and the thickness is 9.5-10.5mm; the light transmission aperture of the first positive double concave lens is 7.5-8.5mm, and the thickness is 2.5-3.5mm; the light transmission aperture of the third negative meniscus lens is 11-12mm, and the thickness is 7-8mm; the light transmission aperture of the second positive double convex lens is 15.5-16.5mm, and the thickness is 6.5-7.5mm; the light transmission aperture of the third positive double convex lens is 22-23mm, and the thickness is 4.5-5.5mm; and the light transmission aperture of the fourth positive double convex lens is 23-24mm, and the thickness is 4.5-5.5mm.

[0018] The lens material of the large field of view object far field of view projection lens for vehicle lamp is glass.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] The large field of view object far field of view projection imaging method for vehicle lamp provided by the present application adopts all spherical glass lenses for the projection lens, which can ensure clear imaging in high and low temperature environments; through the cooperation of the conditional expressions and the positive and negative focal lengths between the lenses, the large field of view object far field of view projection lens meets the requirements of high and uniform relative luminance, and can image under large field of view conditions with high imaging quality and clarity. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is the working flowchart of the large field of view object far field of view projection imaging method for vehicle lamp provided by the present application.

[0022] Figure 2 is a structural schematic diagram of an optical system of a large field of view object far projection lens provided by an embodiment of the present application;

[0023] Figure 3 is a transfer function MTF curve diagram of the optical system provided by the embodiment of the present application;

[0024] Figure 4 is a spot diagram of each field of view visible light band of the optical system provided by the embodiment of the present application;

[0025] Figure 5 is a field curvature and distortion curve diagram of the optical system provided by the embodiment of the present application;

[0026] Figure 6 is a relative luminance diagram of the optical system provided by the embodiment of the present application.

[0027] In the figure, 1. first piece of positive meniscus lens; 2. first piece of negative meniscus lens; 3. first piece of negative double concave lens; 4. first piece of positive double convex lens; 5. second piece of negative meniscus lens; 6. aperture stop; 7. first piece of positive double concave lens; 8. third piece of negative meniscus lens; 9. second piece of positive double convex lens; 10. third piece of positive double convex lens; 11. fourth piece of positive double convex lens; 12. TIR prism; 13. protective glass; 14. digital micromirror device DMD. Embodiment

[0028] The technical solution of the present application will be further described below in combination with the drawings and embodiments. Embodiment

[0029] Referring to the drawings Figure 1 and the drawings Figure 2 are respectively a work flow diagram of a large field of view object far projection imaging method for vehicle lamp and a structural schematic diagram of a projection lens optical system provided by the embodiment.

[0030] In combination with Figure 1 and Figure 2 It can be seen that the imaging method comprises the following steps:

[0031] (1) converging light rays: the incident light rays are converged by two pieces of large aperture meniscus spherical lenses, and the light rays are sequentially included along an optical axis according to the direction of light ray incidence, including a first piece of positive meniscus lens 1 and a first piece of negative meniscus lens 2;

[0032] (2) reducing structure and aberration: the converged light rays pass through a double cemented lens group composed of a first piece of negative double concave lens 3 and a first piece of positive double convex lens 4 to reduce structure and aberration;

[0033] (3) Further converging light: the second negative meniscus lens 5 is used to further converge light, so that all the light enters the aperture stop 6;

[0034] (4) Correcting chromatic aberration and spherical aberration, reducing aberration: the three cemented lenses are used to correct chromatic aberration and further reduce aberration. The three cemented lens groups in the light incident direction include the first positive double-concave lens 7, the third negative meniscus lens 8, and the second positive double-convex lens 9. The aperture stop 6 is located on the object side of the first positive double-concave lens 7, which can correct the spherical aberration.

[0035] (5) Converging light path, reducing distortion, and clear imaging: two double-convex lenses are used, including the third positive double-convex lens 10 and the fourth positive double-convex lens 11, to converge the light path and reduce distortion. Finally, the light enters the TIR total reflection prism 12, passes through the protective glass 13, and forms a clear image on the DMD image plane 14.

[0036] By Figure 2 It can be seen that the lens structure adopted in the embodiment is a double-Gauss coaxial structure. In the light incident direction, the optical elements include the first positive meniscus lens 1, the first negative meniscus lens 2, the first negative double-concave lens 3, the first positive double-convex lens 4, the second negative meniscus lens 5, the aperture stop 6, the first positive double-concave lens 7, the third negative meniscus lens 8, the second positive double-convex lens 9, the third positive double-convex lens 10, the fourth positive double-convex lens 11, the TIR prism 12, the protective glass 13, and the digital micromirror device DMD 14. The aperture stop 6 is located on the object side of the first positive double-concave lens 7.

[0037] The first positive meniscus lens has a light aperture of 70-71mm and a thickness of 14-15mm. The first negative meniscus lens has a light aperture of 61.5-62.5mm and a thickness of 4.5-5.5mm. The first negative double-concave lens has a light aperture of 30.5-31.5mm and a thickness of 4-5mm. The first positive double-convex lens has a light aperture of 28.5-29.5mm and a thickness of 9.5-10.5mm. The second negative meniscus lens has a light aperture of 21-22mm and a thickness of 9.5-10.5mm. The first positive double-concave lens has a light aperture of 7.5-8.5mm and a thickness of 2.5-3.5mm. The third negative meniscus lens has a light aperture of 11-12mm and a thickness of 7-8mm. The second positive double-convex lens has a light aperture of 15.5-16.5mm and a thickness of 6.5-7.5mm. The third positive double-convex lens has a light aperture of 22-23mm and a thickness of 4.5-5.5mm. The fourth positive double-convex lens has a light aperture of 23-24mm and a thickness of 4.5-5.5mm.

[0038] In the embodiment, the parameters of each optical element (surface) are shown in Table 1.

[0039] Table 1:

[0040]

[0041] In this embodiment, a glass window is placed above the micromirror array (DMD) to protect it. The glass window is made of Corning Eagle XG, which has a refractive index of 1.512. The distance between the lower surface of the glass window and the micromirror array is 0.51 mm. Since this material was not found in the Zemax optical design software's glass library, K7 glass, which has a similar refractive index and Abbe number, was used instead. In other embodiments, H-K9L glass was also used.

[0042] See appendix Figure 3 This is the MTF (Mean Transfer Function) curve of a large field-of-view telecentric projection imaging system for vehicles provided in this embodiment. The MTF curve represents the relationship between modulation density and the number of line logs per millimeter in the image, used to evaluate the ability to reproduce details of objects. In the curve, from top to bottom, the first black dashed line is the theoretically aberration-free curve; the closer it is to the solid black line, the better the image quality. The resolution of the entire pixel-high-light optical system consists of the resolution of the DMD chip and the resolution of the projection lens. The resolution of the projection lens must match the resolution of the DMD chip. The pixel size of the DMD chip is 7.6μm. According to the resolution calculation formula, the resolution can be calculated as follows:

[0043]

[0044] Based on general projection lens design standards, the modulation transfer function (MTF) of this lens is specified to be greater than 0.4 at the cutoff frequency of 66 lp / mm. As can be seen from the figure, most curves are above 0.6, indicating very good resolution and meeting the design specifications.

[0045] See appendix Figure 4 This is a dot plot of the visible light bands in each field of view of a large field-of-view telecentric projection imaging system for vehicles provided in this embodiment. The light spots formed when each ray intersects the image plane are calculated with reference to the principal ray, and are divided into root mean square (RMS) radius and geometrical (GEO) radius. The RMS radius is calculated by first taking the root mean square of the distance between each ray and the principal ray, and then calculating the square root; the GEO radius is the distance from the principal ray to the ray furthest away. The RMS radius calculation depends on each ray, so using the RMS radius as a reference, the more concentrated the light spots, the better the imaging. Figure 3As shown, the first field angle RMS radius is 3.608 μm, the second field angle RMS radius is 3.316 μm, the third field angle RMS radius is 3.003 μm, the fourth field angle is 3.581 μm, the fifth field angle is 7.223 μm, and the RMS radius of the whole field is less than the single pixel size 7.6 μm in the DMD chip, that is, all the light falls into the DMD chip pixel micromirror, and the DMD chip pixel micromirror can control all the light in the field of view.

[0046] Referring to the accompanying drawings Figure 5 It is a field curvature and distortion curve diagram of a large field of view object side telecentric projection imaging system for vehicles provided by the embodiment. The field curvature refers to the image field curvature, and is mainly used to indicate the degree of non-coincidence of the intersection of the whole light beam with the ideal image point in the optical assembly. The distortion refers to the difference in magnification of different parts of an object when the object is imaged through the optical assembly. The distortion will cause the similarity of the image to deteriorate, but does not affect the definition of the image. In general optical systems, as long as the image distortion caused by the distortion is not perceived by the human eye, it is allowed, and the allowed distortion value is about 2%. From Figure 4 It can be seen that the field curvature is within ±0.1, and the distortion is less than 1.5%, which meets the requirements of human visual perception.

[0047] Referring to the accompanying drawings Figure 6 It is a relative luminance diagram of a large field of view object side telecentric projection imaging system for vehicles provided by the embodiment. Since the F number 1.8 illumination large aperture design is adopted, it is ensured that the light source is uniformly projected to the road surface, such as Figure 5 It can be seen that the luminance distribution decreases by 5% from the central field of view to the edge field of view, and the luminance distribution is relatively uniform.

[0048] The results prove that the large field of view object side telecentric projection imaging method and lens provided by the embodiment only use ten spherical glass lenses as optical elements, the F number is 1.8, the focal length is 11.08 mm, the total length of the system is 120.52 mm, the optical transfer function is greater than 0.4 in the visible light waveband and the ±32° large field of view, the spot diagram is less than 7.6 μm, the distortion is less than 2%, the relative luminance is high and uniform, and the projection imaging quality is high.

Claims

1. A method for large field-of-view object-side telecentric projection imaging of vehicle lights, characterized in that... Includes the following steps: (1) Converging light Two large-aperture crescent-shaped surface lenses are used to converge the incident light rays. According to the incident direction of the light rays, along the optical axis, there are a first positive crescent-shaped lens (1) and a first negative crescent-shaped lens (2). The first positive crescent-shaped lens has a light-transmitting aperture of 70-71 mm and a thickness of 14-15 mm. The first negative crescent-shaped lens has a light-transmitting aperture of 61.5-62.5 mm and a thickness of 4.5-5.5 mm. (2) Reduce aberrations The converged light rays are reduced by a cemented doublet lens group; the cemented doublet lens is composed of a first negative biconcave lens (3) and a first positive biconvex lens (4). The aperture of the first negative biconcave lens is 30.5-31.5 mm and the thickness is 4-5 mm; the aperture of the first positive biconvex lens is 28.5-29.5 mm and the thickness is 9.5-10.5 mm. (3) Further convergence of light A second negative meniscus lens (5) is used to further converge the light so that all the light enters the aperture; the aperture of the second negative meniscus lens is 21-22 mm and the thickness is 9.5-10.5 mm. (4) Correct chromatic aberration and spherical aberration to reduce aberrations: A three-cemented lens group is used to correct chromatic aberration, further reduce aberrations, correct spherical aberration, and an aperture stop is used to correct spherical aberration. The three-cemented lens group, according to the direction of light incidence, includes a first positive biconcave lens (7) with an aperture of 7.5-8.5 mm and a thickness of 2.5-3.5 mm, a third negative meniscus lens (8) with an aperture of 11-12 mm and a thickness of 7-8 mm, and a second positive biconvex lens (9) with an aperture of 15.5-16.5 mm and a thickness of 6.5-7.5 mm. An aperture stop (6) is set on the object side of the first positive biconcave lens (7). (5) Converging optical paths, reducing distortion, and achieving clear imaging Two biconvex lens groups are used to converge the light path and reduce distortion. The biconvex lens group includes a third positive biconvex lens (10) with a light-transmitting aperture of 22-23 mm and a thickness of 4.5-5.5 mm, and a fourth positive biconvex lens (11) with a light-transmitting aperture of 23-24 mm and a thickness of 4.5-5.5 mm. The converged light enters the TIR total reflection prism (12), passes through the protective glass (13), and forms a clear image on the DMD image plane (14).

2. A large field-of-view telecentric projection lens for vehicle headlights, characterized in that: It has a dual Gaussian coaxial structure. Along the incident direction of light, the projection lens consists of a first positive meniscus lens (1), a first negative meniscus lens (2), a first negative biconcave lens (3), a first positive biconvex lens (4), a second negative meniscus lens (5), an aperture stop (6), a first positive biconcave lens (7), a third negative meniscus lens (8), a second positive biconvex lens (9), a third positive biconvex lens (10), a fourth positive biconvex lens (11), a TIR prism (12), a protective glass (13), and a digital micromirror device (DMD) (14). Among them, the first negative biconcave lens (3) and the first positive biconvex lens (4) are cemented together to form a cemented doublet lens group; the first positive biconcave lens (7), the third negative meniscus lens (8), and the second positive biconvex lens (9) are cemented together to form a triplet lens group; the aperture stop (6) is set on the object side of the first positive biconcave lens (7). The first positive meniscus lens has an aperture of 70–71 mm and a thickness of 14–15 mm; the first negative meniscus lens has an aperture of 61.5–62.5 mm and a thickness of 4.5–5.5 mm; the first negative biconcave lens has an aperture of 30.5–31.5 mm and a thickness of 4–5 mm; the first positive biconvex lens has an aperture of 28.5–29.5 mm and a thickness of 9.5–10.5 mm; the second negative meniscus lens has an aperture of 21–22 mm and a thickness of 9.5–10.5 mm. The first positive biconcave lens has an aperture of 7.5–8.5 mm and a thickness of 2.5–3.5 mm; the third negative meniscus lens has an aperture of 11–12 mm and a thickness of 7–8 mm; the second positive biconvex lens has an aperture of 15.5–16.5 mm and a thickness of 6.5–7.5 mm; the third positive biconvex lens has an aperture of 22–23 mm and a thickness of 4.5–5.5 mm; and the fourth positive biconvex lens has an aperture of 23–24 mm and a thickness of 4.5–5.5 mm.

3. A large field-of-view telecentric projection lens for vehicle lights according to claim 2, characterized in that: The lens is made of glass.

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