Ultra-short-focus LCD projection lens
By employing a four-lens structure and specially designed lens parameters, the problems of high cost and difficulty in miniaturization of existing LCD projection lenses have been solved, resulting in a projection lens with ultra-short throw, high resolution, large aperture, and stable imaging at high and low temperatures.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-07
- Publication Date
- 2026-03-24
AI Technical Summary
While ensuring resolution and brightness requirements, existing LCD projection lenses are difficult to control in terms of size and cost, resulting in high costs and difficulty in meeting miniaturization requirements.
It adopts a four-lens structure, including a first positive lens, a second negative lens, and a third positive lens, all of which are plastic aspherical lenses. The Fresnel lens is a plastic aspherical or spherical lens. The aperture Fno. ≤ 2.6, the lens focal length and distance meet specific conditions, the lens is designed as an ultra-short focal length lens, and the projection ratio is controlled at 0.9 < |TR| < 1.
It achieves ultra-short throw, high resolution, large aperture, compact structure, low cost, and can correct aberrations, making it suitable for LCD projection devices and meeting the requirements for high and low temperature imaging stability.
Smart Images
Figure CN224035694U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to projection lens technical field, especially in super short focus LCD projection lens. BACKGROUND
[0002] In recent years, with the popularization of home theater, the demand of consumers for high-quality, portable projection equipment increases, and the LCD projection technology breaks through in high resolution, high brightness, miniaturization and other aspects. The demand for low-cost LCD projectors is increasing, and the demand for resolution, miniaturization and large aperture projection lenses is greater. In order to ensure resolution and brightness, the lenses on the market usually use multiple glass lenses, and the size and cost of the lenses are difficult to effectively control. It is necessary to develop a product with low cost and performance requirements. SUMMARY
[0003] The utility model provides a kind of super short focus LCD projection lens, satisfies lens projection quality, guarantees high and low temperature image, and effectively controls lens cost.
[0004] The technical scheme of the utility model is realized as follows: a kind of super short focus LCD projection lens, including first positive lens, second negative lens, diaphragm, third positive lens and Fresnel lens arranged in order from object side to image side, first positive lens, second negative lens, third positive lens are plastic aspheric lens. Positive lens has positive refractive power, and negative lens has negative refractive power.
[0005] Further, the object side surface and the image side surface of the first positive lens are convex and concave in turn, the object side surface and the image side surface of the second negative lens are concave and convex in turn, and the object side surface and the image side surface of the third positive lens are both convex.
[0006] Further, the aperture Fno. of the projection lens is less than or equal to 2.6.
[0007] Further, the image side surface of the Fresnel lens is provided with an LCD screen, the distance between the Fresnel lens and the LCD screen is L, and 8mm < L < 12mm.
[0008] Further, the distance between the rear vertex of the image side of the third positive lens and the Fresnel lens is L1, and L1 < 42mm.
[0009] Further, 0.9 < |f1 / f| < 1.1 and 0.8 < |f2 / f3| < 1, wherein f1 is the focal length of the first positive lens, f2 is the focal length of the second negative lens, f3 is the focal length of the third positive lens, and f is the focal length of the lens optical system.
[0010] Further, the Fresnel lens is a spherical lens or an aspherical lens.
[0011] Further, the Fresnel lens is a plastic aspheric lens.
[0012] Further, 0.9 < |TR| < 1, TR is a lens projection ratio.
[0013] The present application has the advantages that:
[0014] The super-short-focus LCD projection lens adopts a four-lens structure, the first positive lens, the second negative lens and the third positive lens are plastic aspheric lenses, and the fourth lens is a Fresnel lens, so that the obtained LCD projection lens has the advantages of super-short focus, high resolution, large aperture, compact structure, high and low temperature imaging stability, can effectively correct aberration in an optical system, and has lower cost than the prior art LCD projection lens and can be applied to an LCD projection device. BRIEF DESCRIPTION OF DRAWINGS
[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.
[0016] Figure 1 It is a structure schematic diagram of the LCD projection lens.
[0017] Figure 2 It is a spherical aberration schematic diagram of the LCD projection at normal temperature.
[0018] Figure 3 It is an astigmatism schematic diagram of the LCD projection.
[0019] Figure 4 It is a distortion schematic diagram of the LCD projection.
[0020] Figure 5 It is a Rayfan schematic diagram of the LCD projection at normal temperature.
[0021] The first positive lens 1, the second negative lens 2, the diaphragm 3, the third positive lens 4, the Fresnel lens 5, and the LCD screen 6. DETAILED DESCRIPTION
[0022] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.
[0023] As Figure 1 shown in the figure, an ultra-short focus LCD projection lens comprises a first positive lens 1, a second negative lens 2, a diaphragm 3, a third positive lens 4 and a Fresnel lens 5 arranged in sequence from the object side to the image side, the first positive lens 1, the second negative lens 2 and the third positive lens 4 are all plastic aspheric lenses.
[0024] The object side surface and the image side surface of the first positive lens 1 are convex and concave in sequence, the object side surface and the image side surface of the second negative lens 2 are concave and convex in sequence, and the object side surface and the image side surface of the third positive lens 4 are both convex.
[0025] The aperture Fno. of the projection lens is ≤2.6, which meets the lens brightness requirement.
[0026] The image side surface of the Fresnel lens 5 is provided with an LCD screen 6, and the distance between the Fresnel lens 5 and the LCD screen 6 is L, 8mm < L < 12mm. This distance needs to be determined by the optical machine, and too large or too small will be unfavorable to the resolution.
[0027] The back focal distance meets the following conditions, L1 < 42mm, L1 is the distance between the back vertex of the image side of the third positive lens 4 and the Fresnel lens 5. This distance determines the position of the back focal distance of the optical machine, and too small back focal distance will cause the problem of optical path interference by the mechanism.
[0028] 0.9 < |f1 / f| < 1.1, 0.8 < |f2 / f3| < 1, wherein f1 is the focal length of the first positive lens 1, f2 is the focal length of the second negative lens 2, f3 is the focal length of the third positive lens 4, and f is the focal length of the lens optical system.
[0029] The focal length of the lens is determined by the structure of the front and back two surfaces of the lens, and the focal length of the lens reflects the overall situation of the combination of the front and back two surfaces of the lens, which is a structural parameter of the lens. The lens meeting the above limitation conditions can effectively correct the change amount of high and low temperature resolution. In the embodiment, |f1 / f| = 0.99, |f2 / f3| = 0.85.
[0030] The Fresnel lens 5 is an aspheric lens, and the aspheric surface of the Fresnel lens 5 can improve the overall resolution of the lens.
[0031] 0.9 < |TR| < 1, TR is the projection ratio of the lens. The smaller the projection ratio, the larger the projected picture at the same distance, and the higher the design difficulty. In the embodiment, |TR| = 0.98.
[0032] Table 1: Basic lens data of the embodiment
[0033] Surface number Radius of curvature R Surface separation D Refractive index Nd Abbe number Vd First positive lens 1 object side surface 20.29 8.00 1.490 57.4 First positive lens 1 image side surface 60.69 7.40 Second negative lens 2 object side surface -14.02 2.44 1.580 29.9 Second negative lens 2 image side surface -37.19 -0.08 Infinity Infinity 1.70 Third positive lens 4 object side surface 28.84 6.40 1.490 57.4 Third positive lens 4 image side surface -107.79 39.30 Fresnel lens 5 object side surface Infinity 1.60 1.490 57.4 Fresnel lens 5 image side surface Infinity 10.00 LCD screen 6 image surface Infinity
[0034] The object side surface is the surface of the lens close to the object side, and the image side surface is the surface of the lens close to the image side. The curvature radius R represents the curvature radius value of the corresponding surface, in mm, and the surface interval D represents the lens thickness of the corresponding surface or the interval value between lenses, in mm. The table also gives the refractive index Nd and Abbe number Vd of the lens relative to d light (wavelength of 587.6 nm).
[0035] In the embodiment, the first positive lens 1, the second negative lens 2 and the third positive lens 4 are all aspherical lenses. The aspherical lens coefficients are taken as the center of the lens surface as the origin, the optical axis as the x-axis, and the aspherical surface of the lens surface expression satisfying the following formula:
[0036]
[0037] Wherein, X is the depth of the aspherical lens, in mm, Y is the distance from the optical axis to the lens surface, in mm, C is the curvature radius of the aspherical lens, C = 1 / R, k is the conic constant, and b, c, d, e, f, g and h are the coefficients of the aspherical lens.
[0038] Table 2: coefficient specific parameters
[0039]
[0040] Table 3: optical system parameters
[0041] f FNO. TR TTL LCD size 59 2.6 0.98 77.4 2.69 inches
[0042] In the above table, the unit of the paraxial focal length f is mm, the FNO. is the lens aperture value, and the unit of the total optical length TTL is mm.
[0043] The LCD projection lens of the embodiment is tested at room temperature, Figures 2-5 The ball aberration diagram, the astigmatism diagram, the distortion diagram and the Rayfan diagram at room temperature are shown in FIGS. 5-8, respectively. Figures 2-5 It can be seen that the various aberrations of the LCD projection lens of the embodiment are well corrected, and the LCD projection lens can be applied to the LCD projection equipment.
[0044] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims
1. An ultra-compact LCD projection lens characterized in that: The projection lens comprises, arranged in sequence from the object side to the image side, a first positive lens, a second negative lens, a diaphragm, a third positive lens and a Fresnel lens, wherein the first positive lens, the second negative lens and the third positive lens are plastic aspheric lenses; The object side surface and the image side surface of the first positive lens are a convex surface and a concave surface in sequence, the object side surface and the image side surface of the second negative lens are a concave surface and a convex surface in sequence, and the object side surface and the image side surface of the third positive lens are both convex surfaces; The Fresnel lens is a spherical lens; The distance between the rear vertex of the image side of the third positive lens and the Fresnel lens is L1, and L1<42mm; 0.9<|TR|<1, wherein TR is the projection ratio of the lens.
2. The ultra-compact LCD projection lens according to claim 1, characterized in that: The aperture Fno. of the projection lens is ≤2.
6.
3. The ultra-short throw LCD projection lens of claim 1, wherein: The image side surface of the Fresnel lens is provided with an LCD screen, and the distance between the Fresnel lens and the LCD screen is L, wherein 8mm 4. The ultra-short throw LCD projection lens of claim 1, wherein: 0.9<|f1 / f|<1.1 and 0.8<|f2 / f3|<1, wherein f1 is the focal length of the first positive lens, f2 is the focal length of the second negative lens, f3 is the focal length of the third positive lens, and f is the focal length of the optical system of the lens.