Three-piece liquid crystal display (LCD) projection lens
By using a three-piece LCD projection lens design, employing a combination of positive and negative optical power and glass spherical lenses, the problems of poor imaging effect and high cost of existing LCD projection lenses are solved, achieving high-quality and low-cost projection effects.
Patent Information
- Application Number
- CN202520081645.6
- 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, with a large number of lenses and expensive materials.
It adopts a three-element structure, including a first group of lenses, an aperture, a second group of lenses, and a film arranged in sequence. It uses glass spherical lenses, has a small number of lenses, and uses a combination of positive and negative optical power to correct aberrations. The film converges the light, and the aperture controls the amount of light entering.
It achieves high-quality imaging, requires fewer lenses, has low cost, is suitable for micro-projection devices, has low distortion, and meets daily viewing needs.
Smart Images
Figure CN223742844U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of projection lens technology, and in particular to a three-piece LCD 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] 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
[0006] In order to overcome the shortcomings of the prior art, the purpose of this utility model is to provide a three-piece LCD projection lens. This utility model solves the problems of poor imaging and high cost of many existing LCD projection lenses.
[0007] To achieve the above objectives, this utility model provides the following solution:
[0008] A three-element LCD projection lens, comprising:
[0009] The first group of lenses, the aperture stop, the second group of lenses, the film, and the image plane are arranged in sequence.
[0010] 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;
[0011] The first group of lenses is provided with a first lens, and the first lens is a lens with positive optical power;
[0012] The second group of lenses includes: a second lens and a third lens;
[0013] The second lens is a lens with negative optical power, and the third lens is a lens with positive optical power;
[0014] The first lens is placed in front of the aperture stop, and the second and third lenses are both placed behind the aperture stop.
[0015] Preferably, the film is made of plastic, while the other lenses are made of glass.
[0016] Preferably, the first lens, the second lens, and the third lens are all spherical lenses.
[0017] Preferably, the ratio of the focal length of the first group of lenses to the focal length of the projection lens is 7.566, the ratio of the focal length of the second group of lenses to the focal length of the projection lens is -4.059, the ratio of the focal length of the second lens to the focal length of the second group of lenses is 0.111, and the ratio of the focal length of the third lens to the focal length of the second group of lenses is -0.158.
[0018] Preferably, the MTF value of each field of view of the zoom projection lens is greater than 0.4.
[0019] Preferably, the focal length of the zoom projection lens is 59.4mm.
[0020] Preferably, the zoom projection lens has a projection ratio of 0.98.
[0021] The present invention discloses the following technical effects:
[0022] This invention provides a three-element LCD projection lens, comprising: a first group of lenses, an aperture stop, a second group of lenses, a film, and an image plane arranged sequentially; the image plane is used to emit light, the film is used to converge the light, and the aperture stop 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 and a third lens; the second lens is a lens with negative optical power, and the third lens is a lens with positive optical power; the first lens is placed in front of the aperture stop, and the second and third lenses are both placed behind the aperture stop. The LCD projection lens disclosed in this utility model has a throw ratio of 0.98, which is suitable for most daily viewing needs. The lens uses only three glass spherical lenses, and all materials used are low-cost optical lens materials, greatly reducing lens cost and assembly difficulty. The LCD projection lens has a small overall length, meeting the needs of micro-projection devices. In summary, this utility model's LCD projection lens, with only three lenses, has a series of advantages such as high image quality, few lenses, low distortion, reasonable tolerance, and low cost. Attached Figure Description
[0023] 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.
[0024] Figure 1 A schematic diagram of a three-piece LCD projection lens structure provided for an embodiment of this utility model;
[0025] Figure 2 A schematic diagram of the spatial frequency MTF provided for an embodiment of this utility model;
[0026] Figure 3 A chromatic aberration diagram provided for an embodiment of this utility model;
[0027] Figure 4 The field curvature evaluation diagram provided for the embodiments of this utility model;
[0028] Figure 5 The distortion evaluation diagram provided for the embodiments of this utility model.
[0029] Explanation of reference numerals in the attached figures:
[0030] 1-First group of lenses, 2-Second group of lenses, 3-Aperture stop, 4-Film, 5-Image plane, G1-First lens, G2-Second lens, G3-Third lens. Detailed Implementation
[0031] 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.
[0032] 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.
[0033] like Figure 1 As shown, this utility model provides a three-piece LCD projection lens, comprising:
[0034] The first group of lenses 1, the aperture 3, the second group of lenses 2, the film 4, and the image plane 5 are arranged in sequence.
[0035] The image plane 5 is used to emit light, the film 4 is used to converge the light, the aperture 3 is used to control the amount of light entering after convergence, and the first group of lenses 1 and the second group of lenses 2 are both used to correct aberrations.
[0036] The first group of lenses 1 is provided with a first lens G1, and the first lens is a lens with positive optical power;
[0037] The second group of lenses 2 includes: a second lens G2 and a third lens G3;
[0038] The second lens G2 is a lens with negative optical power, and the third lens G3 is a lens with positive optical power;
[0039] The first lens G1 is placed in front of the aperture stop 3, and the second lens G2 and the third lens G3 are both placed behind the aperture stop 3.
[0040] Furthermore, the film 4 is made of plastic, while the other lenses are made of glass.
[0041] Furthermore, the first lens G1, the second lens G2, and the third lens G3 are all spherical lenses.
[0042] Furthermore, the ratio of the focal length f1 of the first group lens 1 of the objective lens system to the focal length f of the objective lens system is approximately 7.566; the ratio of the focal length f2 of the second group lens 2 of the objective lens system to the focal length f of the objective lens system is approximately -4.059; the ratio of the focal length fG2 of the G2 lens to the focal length f2 of the second group lens 2 of the objective lens system is approximately 0.111; the ratio of the focal length fG3 of the G3 lens to the focal length f2 of the second group lens 2 of the objective lens system is approximately -0.158; and the ratio of the focal length f4 of the film 4 to the focal length f of the objective lens system is approximately 1.177.
[0043] Table 1 shows the specific parameters of the projection lens.
[0044] Table 1 shows the specific parameters of the projection lens.
[0045]
[0046]
[0047] The focal length of film 4 is 70mm at f / 4.
[0048] Furthermore, such as Figure 2 As shown, the MTF value of each field of view of the zoom projection lens is greater than 0.4.
[0049] 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 plane size is 46.5 μm (5 pixels), 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 0.4.
[0050] Furthermore, such as Figure 3 As shown, Figure 3 This is a chromatic aberration diagram of the lens, 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 5 pixels of an image plane. In this embodiment, the chromatic aberration is controlled to be within 20µm, less than 0.5 pixels (pixel size 46.5µm).
[0051] Furthermore, such as 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 0.3%, and the TV distortion value is also within 0.3%, indicating that the system has excellent distortion properties.
[0052] The lens has a projection ratio of 0.98; the effective focal length of the lens is 59.4mm, and the F / NO. is 2.7; the lens uses a 2.69-inch LCD screen with a resolution of 1280*720; the lens uses film 4, which can effectively converge the main light angle of the lens.
[0053] Furthermore, in the implementation, the optical lens satisfies the following condition:
[0054] 0.6 <EPND / IH<0.7 (1)
[0055] Wherein, EPND represents the aperture of the optical lens, and IH represents the actual half-image height of the optical lens.
[0056] When condition (1) is met, a reasonable balance between the light transmission of the lens and the size of the image plane 5 can be achieved.
[0057] In the implementation method, the optical lens satisfies the following condition:
[0058] 3 <T L* f / IH 2 <4 (2)
[0059] 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.
[0060] When condition (2) is satisfied, the relationship between the total length of the lens and its resolving power can be reasonably balanced. L When 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.
[0061] In the implementation method, the optical lens satisfies the following condition:
[0062] 55mm <IH / tanθ<65mm (3)
[0063] Wherein, IH represents the actual half-image height of the optical lens, and θ represents the half-field angle of the optical lens.
[0064] 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.
[0065] In the implementation method, the optical lens satisfies the following condition:
[0066] CRA < 3° (4)
[0067] Wherein, CRA represents the principal ray incident angle of the optical lens at image plane 5.
[0068] When condition (4) is met, it can be well matched with the LCD screen and achieve a good projection effect.
[0069] In the implementation method, the optical lens satisfies the following condition:
[0070] 0.75 <fG3 / fG1<0.85 (5)
[0071] Where fG3 represents the focal length of the G3 lens and fG1 represents the focal length of the G1 lens.
[0072] 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.
[0073] When condition (5) is satisfied before and after, better image quality can be obtained while satisfying the system focal length.
[0074] 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.
[0075] 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. A three-piece LCD projection lens characterized by, The application relates to a three-piece LCD projection lens. The first group lens, the diaphragm, the second group lens, the film and the image plane are 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 lens and the second group lens are used for correcting aberration. The first group lens is provided with a first lens which is a lens with positive focal length. The second group lens comprises a second lens and a third lens. The second lens is a lens with negative focal length, and the third lens is a lens with positive focal length. The first lens is arranged in front of the diaphragm, and the second lens and the third lens are arranged behind the diaphragm.
2. The three-piece LCD projection lens according to claim 1, wherein, The film is made of plastic material, and the other lenses are made of glass material.
3. The three-piece LCD projection lens of claim 1, wherein, The first lens, the second lens and the third lens are spherical lenses.
4. The three-piece LCD projection lens of claim 1, wherein, The ratio of the focal length of the first group lens to the focal length of the projection lens is 7.566, the ratio of the focal length of the second group lens to the focal length of the projection lens is -4.059, the ratio of the focal length of the second lens to the focal length of the second group lens is 0.111, and the ratio of the focal length of the third lens to the focal length of the second group lens is -0.
158.
5. The three-piece LCD projection lens of claim 1, wherein, The MTF value of each field of view of the three-piece LCD projection lens is greater than 0.
4.
6. The three-piece LCD projection lens of claim 1, wherein, The focal length of the three-piece LCD projection lens is 59.4mm.
7. The three-piece LCD projection lens of claim 1, wherein, The projection ratio of the three-piece LCD projection lens is 0.98.