Off-axis projection lens
By optimizing the lens combination and materials, an off-axis projection lens was designed, which solved the problems of poor imaging effect and high cost of LCD projection lenses, and achieved high-quality imaging and low-cost projection effect.
Patent Information
- Application Number
- CN202520081566.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-14
- Publication Date
- 2025-12-30
- Estimated Expiration
- 2035-01-14
AI Technical Summary
Existing LCD projection lenses have poor imaging quality and high cost, and cannot meet the requirements for high off-axis ratio.
The structure employs a sequential arrangement of a first group of lenses, an aperture stop, a second group of lenses, and a film, including lens combinations with positive and negative optical powers. It uses glass and plastic lenses, optimizes the lens focal length ratio and distance, controls light convergence and the amount of light entering the lens, and corrects aberrations.
It achieves a balance between image quality and brightness, reduces costs, and supports 50% off-axis projection, while also offering the advantages of high resolution and ease of manufacturing.
Smart Images
Figure CN223742843U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of projection lens technology, and in particular to an off-axis projection lens. Background Technology
[0002] The projection lens is the core component of a projection device. Light passes through a reflective or transmissive light modulation device and then is projected onto the projection screen to form an image.
[0003] Existing projectors can be mainly classified by technology into LCD projectors, DLP projectors, and LCOS projectors. LCD projectors have rapidly captured a large share of the low-to-mid-end consumer market due to their mature technology and ultra-low cost.
[0004] LCD projectors are high-tech products resulting from advancements in liquid crystal technology, lighting technology, and integrated circuits. LCD projectors utilize the photoelectric effect of liquid crystals—that is, the arrangement of liquid crystal molecules changes under the influence of an electric field, affecting the transmittance or reflectance of the liquid crystal cells, thereby influencing their optical properties and producing images with different grayscale levels and colors.
[0005] Due to practical application scenarios, projection lenses are required to have a higher off-axis ratio. When the off-axis ratio reaches 100%, the projection optical engine can be placed directly on any platform for projection without having to consider the problem of insufficient space under the projector.
[0006] To achieve low costs, many existing LCD projection lenses use generic lens designs. While this reduces lens costs, it often results in poor image quality. Other LCD projection lenses, in order to achieve higher image quality and brightness, often use a larger number of lenses and more expensive materials. Utility Model Content
[0007] In order to overcome the shortcomings of the prior art, the purpose of this utility model is to provide an off-axis projection lens. This utility model solves the problems of poor imaging and high cost of many existing LCD projection lenses.
[0008] To achieve the above objectives, this utility model provides the following solution:
[0009] An off-axis projection lens, comprising:
[0010] The first group of lenses, the aperture stop, the second group of lenses, the film, and the image plane are arranged in sequence.
[0011] The image plane is used to emit light, the film is used to converge the light, the aperture is used to control the amount of light entering after convergence, and the first group of lenses and the second group of lenses are both used to correct aberrations;
[0012] The first group of lenses is provided with a first lens, and the first lens is a lens with positive optical power;
[0013] The second group of lenses includes: a second lens, a third lens, and a fourth lens;
[0014] The second lens is a lens with negative optical power, while the third and fourth lenses are both lenses with positive optical power.
[0015] The first lens is placed in front of the aperture stop, and the second, third, and fourth lenses are all placed behind the aperture stop.
[0016] Preferably, the film is made of plastic, while the other lenses are made of glass.
[0017] Preferably, the first lens, the second lens, the third lens, and the fourth lens are all spherical lenses.
[0018] Preferably, the ratio of the focal length of the first group of lenses to the focal length of the projection lens is 0.829; the ratio of the focal length of the second group of lenses to the focal length of the projection lens is -14.51; the ratio of the focal length of the second lens to the focal length of the second group of lenses is 0.034; the ratio of the focal length of the third lens to the focal length of the second group of lenses is -0.140; and the ratio of the focal length of the fourth lens to the focal length of the second group of lenses is -0.071.
[0019] Preferably, the focal length of the film is 135mm.
[0020] Preferably, the MTF value of each field of view of the zoom projection lens is greater than 0.45.
[0021] Preferably, the distance from the third lens to the film is 94mm.
[0022] Preferably, the zoom projection lens has a projection ratio of 1.2.
[0023] The present invention discloses the following technical effects:
[0024] This utility model provides an off-axis projection lens, comprising:
[0025] The first group of lenses, the aperture stop, the second group of lenses, the film, and the image plane are arranged in sequence.
[0026] The image plane is used to emit light, the film is used to converge the light, and the aperture is used to control the amount of light entering after convergence. Both the first group of lenses and the second group of lenses are used to correct aberrations. The first group of lenses includes a first lens, which is a lens with positive optical power. The second group of lenses includes a second lens, a third lens, and a fourth lens. The second lens is a lens with negative optical power, while the third and fourth lenses are both lenses with positive optical power. The first lens is placed in front of the aperture, and the second, third, and fourth lenses are all placed behind the aperture. This invention reasonably balances imaging brightness, cost, image quality, and resolution, and has a series of advantages such as ease of manufacturing, reasonable tolerances, low cost, support for 50% off-axis imaging, and high image quality. It has high practical application value. Attached Figure Description
[0027] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0028] Figure 1 A schematic diagram of an off-axis projection lens structure provided for an embodiment of this utility model;
[0029] Figure 2 A schematic diagram of the spatial frequency MTF provided for an embodiment of this utility model;
[0030] Figure 3 A vertical axis color difference diagram provided for an embodiment of this utility model;
[0031] Figure 4 The field curvature evaluation diagram provided for the embodiments of this utility model;
[0032] Figure 5 The distortion evaluation diagram provided for the embodiments of this utility model;
[0033] Figure 6 Comparative evaluation diagrams provided for embodiments of this utility model.
[0034] Explanation of reference numerals in the attached figures:
[0035] 1-First group of lenses, 3-Second group of lenses, 2-Aperture, 4-Film, 5-Image plane, G01-First lens, G02-Second lens, G03-Third lens, G04-Fourth lens. Detailed Implementation
[0036] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.
[0037] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0038] like Figure 1 As shown, this utility model provides an off-axis projection lens, comprising:
[0039] The first group of lenses 1, the aperture 2, the second group of lenses 3, the film 4, and the image plane 5 are arranged in sequence.
[0040] The image plane 5 is used to emit light, the film 4 is used to converge the light, the aperture 2 is used to control the amount of light entering after convergence, and the first group of lenses 1 and the second group of lenses 3 are both used to correct aberrations.
[0041] The first group of lenses 1 is provided with a first lens G01, and the first lens is a lens with positive optical power;
[0042] The second group of lenses 3 includes: a second lens G02, a third lens G03, and a fourth lens G04;
[0043] The second lens G02 is a lens with negative optical power, while the third lens G03 and the fourth lens G04 are both lenses with positive optical power.
[0044] The first lens G01 is placed in front of the aperture stop 2, and the second lens G02, the third lens G03 and the fourth lens G04 are all placed behind the aperture stop 2.
[0045] Furthermore, the film 4 is made of plastic, while the other lenses are made of glass.
[0046] Furthermore, the first lens G01, the second lens G02, the third lens G03, and the fourth lens G04 are all spherical lenses.
[0047] The ratio of the focal length f1 of the first group lens 1 of the projection lens to the focal length f of the projection lens is approximately 0.829; the ratio of the focal length f2 of the second group lens 3 of the projection lens to the focal length f of the projection lens is approximately -14.51; the ratio of the focal length fG02 of the G02 lens to the focal length f2 of the second group lens 3 of the projection lens is approximately 0.034; the ratio of the focal length fG03 of the G03 lens to the focal length f2 of the second group lens 3 of the projection lens is approximately -0.140; the ratio of the focal length fG04 of the G04 lens to the focal length f2 of the second group lens 3 of the projection lens is approximately -0.071; and the ratio of the focal length f5 of the film 4 to the focal length f of the projection lens is approximately 1.226.
[0048] Table 1 shows the specific parameters of the projection lens.
[0049] Table 1. Specific parameters of the projection lens
[0050]
[0051]
[0052] Furthermore, the focal length of film 4 is 135mm.
[0053] Furthermore, such as Figure 2 As shown, the MTF value of each field of view of the zoom projection lens is greater than 0.45.
[0054] Specifically, MTF (Modulation Transfer Function) is currently the most accurate and scientific evaluation standard for lenses. The vertical axis represents contrast ratio; the closer it is to 1, the better the lens image quality. The horizontal axis represents resolution, measured in line pairs per millimeter. In this embodiment, the image source pixel size is 46.1 μm, corresponding to a half-Nyquist frequency of 5.4 line pairs per millimeter. In this embodiment, the MTF value at the half-Nyquist frequency for each field of view is above 0.45.
[0055] Furthermore, such as Figure 3 As shown, the vertical axis chromatic aberration diagram of the lens is plotted, with the vertical axis representing the image height field of view value and the horizontal axis representing the numerical value in micrometers. The diagram plots the chromatic aberration values for each field of view between blue, red, and green light (dominant wavelengths) based on the dominant wavelength. Projection lenses generally require the chromatic aberration value to be within the size of one image source pixel. In this embodiment, the axial chromatic aberration is controlled within 26 μm, which is less than one pixel size (pixel size 46.1 μm).
[0056] like Figure 4-5As shown, the vertical axis represents the field of view of the lens. The horizontal axis of the field curvature plot represents the magnitude of the field curvature value, and the horizontal axis of the distortion plot represents the distortion value. Distortion is a very important indicator for projection lenses, and it generally needs to be controlled within 3%, while TV distortion is required to be controlled within 1%. The system distortion of this embodiment is within 0.4%, and the TV distortion value is also within 0.3%, indicating excellent distortion properties of the system.
[0057] like Figure 6 As shown, relative illuminance refers to the ratio of illuminance at different coordinate points on the image plane to the illuminance at the center point. The vertical axis represents the normalized illuminance value, and the horizontal axis represents the field of view angle of the lens. Under the same conditions, a smooth transition of the relative illuminance curves for each field of view indicates uniform illuminance within the projection frame, and the closer the relative illuminance value for each field of view is to 1, the higher the final projection brightness.
[0058] Furthermore, the lens has a projection ratio of 1.2. The lens has an effective focal length of 110.1mm and an f / n=2.8. The lens uses a 4.0-inch LCD screen with a resolution of 1920*1080. The lens uses film 4, which can effectively converge the principal ray angle of the lens.
[0059] The distance between the G03 lens and film 4 reaches 94mm, providing sufficient space to incorporate a plane mirror to reflect the light path, thereby reducing the projector size. The publicly disclosed LCD projection lens has a sufficient image height design and an offset of over 50%.
[0060] More specifically, in the implementation, the optical lens satisfies the following condition:
[0061] 0.5 <EPND / IH<1 (1)
[0062] Wherein, EPND represents the aperture of the optical lens, and IH represents the actual half-image height of the optical lens.
[0063] When condition (1) is met, a reasonable balance between the light transmission of the lens and the size of the imaging surface 5 can be achieved.
[0064] In the implementation method, the optical lens satisfies the following condition:
[0065] 4 <T L* f / IH 2 <6 (2)
[0066] Among them, T L The optical total length of the optical lens is represented by f, the effective focal length of the optical lens is represented by f, and the actual half-image height of the optical lens is represented by IH.
[0067] When condition (2) is satisfied, the relationship between the total length of the lens and its resolving power can be reasonably balanced. LWhen the / f / IH value exceeds the upper limit, the overall length of the lens is too large, or in other words, if the overall length is shortened, the image height will be insufficient; T L When the value of / f / IH exceeds the lower limit, the lens aberration correction becomes difficult due to the excessive optical focal length of each lens, and the resolving power decreases significantly.
[0068] In the implementation method, the optical lens satisfies the following condition:
[0069] 100mm <IH / tanθ<120mm (3)
[0070] Wherein, IH represents the actual half-image height of the optical lens, and θ represents the half-field angle of the optical lens.
[0071] When condition (3) is met, the distortion of the optical lens can be reasonably limited, reducing the difficulty of distortion correction. When the value of IH / tanθ exceeds the lower limit, the distortion of the lens will increase in the negative direction; when the value of IH / tanθ exceeds the upper limit, the distortion of the lens will increase in the positive direction.
[0072] In the implementation method, the optical lens satisfies the following condition:
[0073] CRA < 5° (4)
[0074] Wherein, CRA represents the principal ray incident angle of the optical lens on the imaging plane 5.
[0075] When condition (4) is met, it can be well matched with the LCD screen and achieve a good projection effect.
[0076] In the implementation method, the optical lens satisfies the following condition:
[0077] 0.9 <fG04 / fG01<1.5 (5)
[0078] Where fG04 represents the focal length of the G04 lens, and fG01 represents the focal length of the G01 lens.
[0079] The system has a small number of lenses. In order to obtain a better imaging effect, the optical power is combined in a positive-negative-positive manner. The focal lengths of the two positive optical power lenses are close, which can enhance the symmetry of the system and help optimize image quality.
[0080] When condition (5) is satisfied before and after, better image quality can be obtained while satisfying the system focal length.
[0081] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.
[0082] This document uses specific examples to illustrate the principles and implementation methods of this utility model. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this utility model. Furthermore, those skilled in the art will recognize that, based on the ideas of this utility model, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this utility model.
Claims
1. An off-axis projection lens characterized in that, The application relates to a projection lens. The projection lens comprises a first group of lenses, a diaphragm, a second group of lenses, a film and an image plane arranged in sequence. The image plane is used for emitting light, the film is used for converging the light, the diaphragm is used for controlling the light quantity of the converged light, and the first group of lenses and the second group of lenses are used for correcting aberration. The first group of lenses is provided with a first lens which is a lens with positive focal length. The second group of lenses comprises a second lens, a third lens and a fourth lens. The second lens is a lens with negative focal length, and the third lens and the fourth lens are lenses with positive focal length. The first lens is arranged in front of the diaphragm, and the second lens, the third lens and the fourth lens are arranged behind the diaphragm.
2. An off-axis projection lens according to claim 1, characterized in that The film is made of plastic material, and the other lenses are made of glass material.
3. The off-axis projection lens of claim 1, wherein, The first lens, the second lens, the third lens and the fourth lens are spherical lenses.
4. The off-axis projection lens of claim 1, wherein, The ratio of the focal length of the first group of lenses to the focal length of the projection lens is 0.829, the ratio of the focal length of the second group of lenses to the focal length of the projection lens is -14.51, the ratio of the focal length of the second lens to the focal length of the second group of lenses is 0.034, the ratio of the focal length of the third lens to the focal length of the second group of lenses is -0.140, and the ratio of the focal length of the fourth lens to the focal length of the second group of lenses is -0.
071.
5. The off-axis projection lens of claim 1, wherein, The focal length of the film is 135 mm.
6. The off-axis projection lens of claim 1, wherein, The MTF value of each field of view of the off-axis projection lens is greater than 0.
45.
7. The off-axis projection lens of claim 1, wherein, The distance from the third lens to the film is 94 mm.
8. The off-axis projection lens of claim 1, wherein, The projection ratio of the off-axis projection lens is 1.2.