Large-aperture three-piece projection lens
Through the combination of large-aperture three-piece projection lens structure and lens material, the problem of image quality and light efficiency improvement of projection lenses is solved, and high-definition imaging and system lightweight are achieved.
Patent Information
- Application Number
- CN202422478965.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-14
- Publication Date
- 2025-07-25
- Estimated Expiration
- 2034-10-14
AI Technical Summary
It is difficult for existing projection lenses to achieve large aperture, long rear focal, and high-definition imaging at the same time, and the imaging quality is limited and the system's light efficiency improvement is limited.
A large aperture three-piece projection lens structure is adopted, including a first lens, a second lens, a third lens and a spatial light modulator. The lens material is a combination of thermoplastic and glass. The aperture is set for vignetting control, and the lens parameters are optimized to improve imaging quality.
It realizes the balance of large aperture, large field of view, high image quality and long rear focal of the projection lens, clear imaging, shortened system length, and lightweight overall size, meeting the spatial structure requirements of the DLP optical system.
Smart Images
Figure CN223155304U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of automotive projection lenses, in particular to a large-aperture three-piece projection lens. Background Technique
[0002] In recent years, with the in-depth application of new technologies such as intelligent driving and intelligent sensing in the automotive field, as the "glasses" for night driving - vehicle lights, they also play a crucial role in safe driving. The emergence of ADB (Adaptive Driving Beam) headlights enables vehicle lights to not only take into account illumination but also play a good safety role, thus making pixelated vehicle lights the intelligent development direction of vehicle lights.
[0003] Currently, pixelated and intelligent projection vehicle lights mainly rely on high-pixel LEDs and digital light processing (DLP) projection technologies. Compared with traditional vehicle lights, DLP technology has been widely used in the civilian projection field and is relatively mature. It mainly consists of a lighting optical path, a spatial light modulator (DMD), and a projection optical path, etc. Due to the limitations of the system structure, the projection lens needs to have a long back focal length. In order to improve the system light efficiency, the projection lens needs to have a large aperture. These requirements pose greater challenges to the design of the projection lens. In the prior art, some projection lenses adopt a 5-piece glass structure, and in order to control the chromatic aberration and thermal stability of the system, some glass materials with special temperature characteristics need to be used; some use 4-piece all-glass or glass-plastic hybrid structure projection lenses, but the imaging quality is low. If coating is required, glass materials with low melting points need to be used; the aperture and back focal length of the entire projection system cannot be made large simultaneously, which limits the improvement of the system light efficiency. Summary of the Invention
[0004] The technical problem to be solved by the utility model is: to provide a large-aperture three-piece projection lens in order to solve the problems existing in the prior art in the above-mentioned background technique.
[0005] The technical solution adopted by the utility model to solve its technical problem is: a large-aperture three-piece projection lens,
[0006] along the optical axis direction, successively includes a first lens, a second lens, a third lens, and a spatial light modulator from the image side to the object side. The first lens is a meniscus lens with positive optical power and long focal length, the second lens is a concave lens with negative optical power, and the third lens is a convex lens with positive optical power;
[0007] It also includes two diaphragms, which are respectively a first diaphragm arranged on the object side surface of the first lens and a second diaphragm arranged on the image side surface of the second lens.
[0008] The first aperture is disposed on the object side surface of the first lens, which is beneficial to the overall appearance of the lens; the second aperture is disposed on the image side surface of the second lens, and can perform vignetting control on the off-axis field aberration.
[0009] Furthermore, the material of the first lens is heat-resistant plastic. Compared with the glass lens, it has lower manufacturing cost and more flexible design space, which is beneficial to well solve the problems of unclear imaging, distorted field of view, narrow field of view, etc. in the case of large-aperture lenses. In this way, good imaging quality can be achieved without setting too many lenses.
[0010] Furthermore, the refractive index n1 of the first lens is 1.4 to 1.7, the focal length f1 of the first lens satisfies 1000 < |f1|, and the Abbe number vd1 of the first lens satisfies: 25 ≤ vd1 ≤ 60.
[0011] Furthermore, the refractive index n1 of the first lens is 1.49, the focal length f1 of the first lens satisfies 1200 < |f1|, and the Abbe number vd1 of the first lens is 57.
[0012] Furthermore, the second lens and the third lens form a cemented lens. Such a setting can reduce the assembly tolerance and make the actual performance of the system closer to the design value.
[0013] Furthermore, the combined focal length f23 of the second lens and the third lens and the effective focal length EFL of the projection lens satisfy: 0.7 < |f23 / EFL| < 2.
[0014] Furthermore, the materials of the second lens and the third lens are glass.
[0015] Furthermore, the object side surface of the second lens is concave or flat, the refractive index n2 of the second lens is 1.7 to 2.0, and the Abbe number vd2 of the second lens satisfies: vd2 ≤ 30. Setting a larger refractive index of the second lens can refract light as much as possible, thereby increasing the field of view of the projection lens, reducing the barrel distortion of the edge field of view, and improving the contrast of the edge field of view of the system.
[0016] Furthermore, the refractive index n3 of the third lens is 1.6 to 1.8, and the Abbe number vd3 of the third lens satisfies: vd2 > 40. Setting a larger Abbe number of the third lens can better correct the chromatic aberration of the optical system.
[0017] The beneficial effects of the present utility model:
[0018] The present utility model has a three-lens structure, adopts a combination of heat-resistant plastic and glass lenses, realizes good thermal stability, has no special requirements for temperature characteristics, and can achieve high-quality imaging effects;
[0019] Through the combination of this architecture and materials, requirements such as large aperture, large field of view, high image quality, and long back focal length of the projection lens can be achieved simultaneously, and the imaging effect is clear; the system F-number (aperture size) is between 1.2 and 1.5, and the imaging quality can reach the entire field of view > ±7.8°, modulation transfer function MTF > 0.3 @ 16.5 lp / mm. The back focal length can achieve the ratio of the back focal length BFL to the effective focal length EFL of the projection lens: BFL / EFL > 0.7. The projection lens can achieve a better clear imaging effect, and the overall image quality is distortion-free; the system length can be effectively shortened, achieving the ratio of the total optical length TTL of the lens to the effective focal length EFL of the projection lens: TTL / EFL < 2.2, which can further reduce the overall size of the projection device and achieve lightweight. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The present utility model will be further described below in conjunction with the drawings and embodiments.
[0021] Figure 1 It is a schematic structural diagram of Embodiment 1 of the present utility model.
[0022] Figure 2 It is a field curvature curve diagram of Embodiment 1 of the present utility model.
[0023] Figure 3 It is a distortion curve diagram of Embodiment 1 of the present utility model.
[0024] Figure 4 It is a vertical chromatic aberration diagram of Embodiment 1 of the present utility model.
[0025] Figure 5 It is a modulation transfer function curve diagram of Embodiment 1 of the present utility model at 20 °C.
[0026] Figure 6 It is a modulation transfer function curve diagram of Embodiment 1 of the present utility model at 85 °C.
[0027] Figure 7 It is a modulation transfer function curve diagram of Embodiment 1 of the present utility model at 125 °C.
[0028] Figure 8 It is a schematic structural diagram of Embodiment 2 of the present utility model.
[0029] Figure 9 It is a modulation transfer function curve diagram of Embodiment 2 of the present utility model.
[0030] Figure 10 It is a vertical chromatic aberration diagram of Embodiment 2 of the present utility model.
[0031] Figure 11 It is a schematic structural diagram of Embodiment 3 of the present utility model.
[0032] Figure 12It is the modulation transfer function curve graph of the third embodiment of the present utility model.
[0033] Figure 13 It is the vertical chromatic aberration graph of the third embodiment of the present utility model.
[0034] In the figure: 1. First lens; 2. Second lens; 3. Third lens; 4. Spatial light modulator. Specific embodiments
[0035] Now, the present utility model will be further described in detail with reference to the accompanying drawings. These drawings are all simplified schematic diagrams, only schematically showing the basic structure of the present utility model, so they only show the components related to the present utility model.
[0036] Embodiment 1
[0037] As Figure 1 shown, a large-aperture three-piece projection lens, along the optical axis direction, sequentially includes a first lens 1, a second lens 2, a third lens 3, and a spatial light modulator 4 from the image side to the object side. The first lens 1 is a meniscus lens with positive optical power and long focal length. The second lens 2 is a concave lens with negative optical power. The third lens 3 is a convex lens with positive optical power. It also includes two diaphragms (not shown in the figure), which are a first diaphragm disposed on the object side surface of the first lens 1 and a second diaphragm disposed on the image side surface of the second lens 2 respectively. Among them, the first diaphragm is beneficial to the overall appearance of the lens, and the second diaphragm can perform vignetting control on off-axis field aberrations.
[0038] Among them, the shape of the first lens 1 can be meniscus-shaped, with extremely small contribution to the focal length of the system, having a more flexible design space, which is beneficial to well solve the problems of unclear imaging, distorted field of view, narrow field of view, etc. in the case of small and thin lenses. In this way, without setting too many lenses, the optical system can have good imaging quality. The refractive index n1 of the first lens 1 is 1.4 - 1.7, the focal length f1 of the first lens 1 satisfies 1000 < |f1|, and the Abbe number vd1 of the first lens 1 satisfies: 25 ≤ vd1 ≤ 60. The first lens 1 is made of heat-resistant plastic, which has lower manufacturing cost and more flexible design space compared with glass lenses, and is beneficial to well solve the problems of unclear imaging, distorted field of view, narrow field of view, etc. in the case of large-aperture lenses. In this way, without setting too many lenses, the optical system can have good imaging quality.
[0039] The object side of the second lens 2 can be concave or flat, and its material is glass. The refractive index n2 of the second lens 2 is 1.7 to 2.0, and the Abbe number vd2 of the second lens 2 satisfies: vd2 ≤ 30. A larger refractive index can refract light as much as possible, thereby increasing the field of view of the projection lens, reducing the barrel distortion of the marginal field of view, and improving the contrast of the marginal field of view of the system. The material of the third lens 3 is also glass, the refractive index n3 is 1.6 to 1.8, and the Abbe number vd3 of the third lens satisfies: vd2 > 40. The larger Abbe number vd3 of the third lens 3 can better correct the chromatic aberration of the optical system. The combined focal length f23 of the second lens 2 and the third lens 3 and the effective focal length EFL of the projection lens satisfy: 0.7 < |f23 / EFL| < 2.
[0040] Table 1 shows the optical parameters of the projection lens in the first embodiment. In Table 1, EFL is the effective focal length of the projection lens; BFL is the back focal length of the projection lens; F / # is the aperture value; FOV is the field of view angle of the projection lens.
[0041] Table 1
[0042]
[0043] Table 2 shows the optical parameters of the first lens 1, the second lens 2, and the third lens 3 in the projection lens of the first embodiment. In Table 2, S1 is the image side of the first lens 1, S2 is the object side of the first lens 1; S3 is the image side of the second lens 2, S4 is the object side of the second lens 2; S5 is the image side of the third lens 3, S6 is the object side of the third lens 3; R is the radius of curvature; Th is the central thickness of the lens; Nd is the refractive index of the lens; vd is the Abbe number of the lens.
[0044] Table 2
[0045]
[0046] Figure 2 is the field curvature curve graph of the projection lens obtained by using the projection lens structure and the data in Table 1 and Table 2; wherein, the abscissa is the magnitude of the field curvature, in mm; the ordinate is the normalized image height; T represents the meridional direction, and S represents the sagittal direction. Figure 1 is the distortion curve graph of the projection lens obtained by using the projection lens structure and the data in Table 1 and Table 2; wherein, the abscissa is the magnitude of the distortion, in %; the ordinate is the normalized image height, and the distortion in the full field of view can be made below 1%.
[0047] Figure 3 is using Figure 1 of the projection lens structure and the data in Table 1 and Table 2, the obtained projection lens distortion curve graph; wherein, the abscissa is the magnitude of the distortion, in %; the ordinate is the normalized image height, and the distortion in the full field of view can be made below 1%.
[0048] Figure 4 is using Figure 1The vertical chromatic aberration diagram of the projection lens obtained from the projection lens structure and the data in Table 1 and Table 2; wherein, the abscissa represents the field height, with the unit of μm; the ordinate represents the vertical position difference of light rays with different wavelengths on the image plane, Figure 4 It can be seen from [here] that the red-green and blue-green chromatic aberrations are both within 20 μm.
[0049] Figure 5 is obtained by using Figure 1 the projection lens structure and the data in Table 1 and Table 2, the modulation transfer function curve diagram of the projection lens at 20 °C is obtained. The abscissa is the spatial frequency, with the unit of line pairs per millimeter (LP / mm), and the ordinate is the modulation transfer function. At the spatial frequency of 16.5 LP / mm, the MTF corresponding to the central field of view (0.0000 mm) is above 0.65, and the MTF corresponding to the maximum field of view (6.0000 mm) is above 0.3, far meeting the requirements of the human eye's limit angular resolution. Figure 6 is obtained by using Figure 1 the projection lens structure and the data in Table 1 and Table 2, the modulation transfer function curve diagram of the projection lens at 85 °C is obtained. Figure 7 is obtained by using Figure 1 the projection lens structure and the data in Table 1 and Table 2, the modulation transfer function curve diagram of the projection lens at 125 °C is obtained. The MTF corresponding to the central field of view (0.0000 mm) is above 0.9, and the MTF corresponding to the maximum field of view (6.0000 mm) is above 0.15, meeting the requirements of the human eye's limit angular resolution. In the temperature range from 20 °C to 125 °C, the MTF value of the full field of view reaches above 0.15.
[0050] Example 2
[0051] As Figure 8 shown, compared with Example 1, the second lens 2 and the third lens 3 adopt a cemented structure, which can reduce the assembly tolerance and make the actual performance of the system closer to the design value. The system parameters of Example 2 are shown in Table 3. By using Figure 8 the projection lens structure and the data in Table 3, the modulation transfer function curve diagram of the projection lens is obtained. As Figure 9 shown, the field of view reaches ±8.1°, and BFL / EFL reaches 1.0; the full-field distortion can be achieved at 0.8%; the full-field MTF value reaches above 0.3. By using Figure 8 the projection lens structure and the data in Table 3, the vertical chromatic aberration diagram of the projection lens is obtained. As Figure 10 shown, the red-green and blue-green chromatic aberrations are both within 12 μm.
[0052] Table 3
[0053]
[0054] Embodiment 3
[0055] As shown Figure 11 in the figure, compared with Embodiment 1, the second lens 2 and the third lens 3 adopt a cemented structure, which can reduce the assembly tolerance. The refractive index n1 of the first lens 1 is 1.49, the focal length f1 of the first lens satisfies 1200 < |f1|, and the Abbe number vd1 of the first lens is 57. The system parameters of Embodiment 3 are shown in Table 4. Using Figure 11 the projection lens structure and the data in Table 4, the modulation transfer function curve graph of the projection lens obtained is as shown Figure 12 in the figure. The field of view reaches ±8.1°, BFL / EFL reaches 1.04, the full-field distortion can be made below 0.85%, and the full-field MTF value reaches above 0.3. Using Figure 11 the projection lens structure and the data in Table 4, the vertical chromatic aberration graph of the projection lens obtained is as shown Figure 13 in the figure. The red-green and blue-green chromatic aberrations are both within 14um.
[0056] Table 4
[0057]
[0058] Enlightened by the above ideal embodiments based on the present utility model, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of this utility model. The technical scope of this utility model is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.
Claims
1. A large-aperture three-piece projection lens, characterized in that: Along the optical axis direction, it sequentially includes a first lens (1), a second lens (2), a third lens (3) and a spatial light modulator (4) from the image side to the object side. The first lens (1) is a meniscus lens with positive optical power and long focal length. The second lens (2) is a concave lens with negative optical power. The third lens (3) is a convex lens with positive optical power; It further includes two diaphragms, namely a first diaphragm provided on the object side surface of the first lens (1) and a second diaphragm provided on the image side surface of the second lens (2).
2. The large-aperture three-piece projection lens according to claim 1, wherein: The material of the first lens (1) is heat-resistant plastic.
3. The large-aperture three-piece projection lens according to claim 2, characterized in that: The refractive index n1 of the first lens (1) is 1.4 - 1.
7. The focal length f1 of the first lens (1) satisfies 1000 < |f1|. The Abbe number vd1 of the first lens (1) satisfies: 25 ≤ vd1 ≤ 60.
4. The large-aperture three-piece projection lens according to claim 3, wherein: The refractive index n1 of the first lens (1) is 1.
49. The focal length f1 of the first lens (1) satisfies 1200 < |f1|. The Abbe number vd1 of the first lens (1) = 57.
5. The large-aperture three-piece projection lens according to claim 1, wherein: The second lens (2) and the third lens (3) form a cemented lens.
6. The large-aperture three-piece projection lens according to claim 5, wherein: The combined focal length f23 of the second lens (2) and the third lens (3) and the effective focal length EFL of the projection lens satisfy: 0.7 < |f23 / EFL| < 2.
7. The large-aperture three-piece projection lens according to claim 6, characterized in that: The materials of the second lens (2) and the third lens (3) are glass.
8. The large-aperture three-piece projection lens according to claim 1 or 6, characterized in that: The object side surface of the second lens (2) is concave or flat. The refractive index n2 of the second lens (2) is 1.7 - 2.
0. The Abbe number vd2 of the second lens (2) satisfies: vd2 ≤ 30.
9. The large-aperture three-piece projection lens according to claim 1 or 6, characterized in that: The refractive index n3 of the third lens (3) is 1.6 - 1.
8. The Abbe number vd3 of the third lens (3) satisfies: vd2 > 40.