Short-focus projection lens with off-axis
By combining glass spherical mirrors and plastic aspherical mirrors, the problem of LCD projection lenses being unable to achieve short focal lengths and off-axis projection without increasing the number of lenses is solved. This achieves reduced focal length and improved off-axis projection, providing a high-performance projection effect at a cost-effective price.
Patent Information
- Application Number
- CN202423074278.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-13
- Publication Date
- 2025-10-31
- Estimated Expiration
- 2034-12-13
AI Technical Summary
Existing LCD projection lenses cannot achieve short focal lengths and off-axis projection without increasing the number of lenses, resulting in high costs. There is an urgent market demand for multifunctional and cost-effective projection lenses.
By combining glass spherical mirrors and plastic aspherical mirrors, and through the reasonable matching and optimization of lenses with different focal lengths, a short-throw projection lens with off-axis is designed. The number of lenses used is not increased by much, the focal length is greatly reduced, the projection ratio reaches 0.6, and the off-axis is improved to 70%.
With only a slight increase in the number of lenses used, the overall focal length of the lens is greatly reduced, the throw ratio reaches 0.6, and the off-axis is improved to 70%, providing a high-performance short-throw projection effect at a cost-effective price.
Smart Images
Figure CN223501245U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of projection lens technology, specifically relating to a short-throw projection lens with an off-axis. Background Technology
[0002] With the increasing popularity of projection technology, the market demand for high-end projection lenses is rising. Currently, projectors on the market are mainly divided into two types: DLP projectors and LCD projectors. DLP projectors are small in size and have good color, and generally use short-throw lenses with offset, but the overall cost is high and the market share is low. LCD projectors have dominated the market in recent years and have good performance, but the size is larger than that of DLP projectors. They generally use long-throw lenses without offset (throw ratio 1.2~1.4, offset is 0), and the number of lenses used in the lens is small, resulting in lower overall lens design and manufacturing costs.
[0003] Currently, due to the large size of LCDs, if a short-throw lens is required, the number of lenses needed will increase significantly, making it difficult to control costs. Adding an off-axis lens would further complicate matters. The market demand for multi-functional, cost-effective projection lenses is growing stronger. At present, without increasing the number of lenses, the focal length of LCD lenses cannot be shortened further, and aberrations cannot be corrected. To achieve a short-throw lens, the number of lenses used must be increased, but the cost will increase rapidly. Adding an off-axis lens would further increase the size and number of lenses, resulting in high costs. Therefore, there is an urgent need to develop a short-throw optical projection lens with an off-axis feature that offers a cost advantage. Utility Model Content
[0004] The purpose of this invention is to provide a short-throw projection lens with an off-axis, which can significantly reduce the overall focal length of the lens without increasing the number of lenses used in the lens, thereby solving the problems mentioned in the background art.
[0005] To achieve the above objectives, this utility model provides the following technical solution: a short-throw projection lens with an off-axis, comprising a projection lens body, the projection lens body including a housing, and inside the housing arranged a first lens, a second lens, a third lens, a fourth lens, and a fifth lens in sequence from the object side to the image side along the axial direction of the housing. The first lens is a spherical lens with negative optical power and a convex object side, the second lens is a spherical lens with positive optical power and a convex object side, the third lens is a spherical lens with positive optical power and a convex object side, the fourth lens is an aspherical lens with negative optical power and a concave object side, and the fifth lens is an aspherical lens with positive optical power and a convex object side.
[0006] Furthermore, the first lens, the second lens, and the third lens are all made of glass, while the fourth lens and the fifth lens are both made of plastic.
[0007] Furthermore, the image-side surface of the first lens is concave, the image-side surface of the second lens is convex, concave, or flat, the image-side surface of the third lens is convex, concave, or flat, the image-side surface of the fourth lens is concave, and the image-side surface of the fifth lens is convex, concave, or flat.
[0008] Furthermore, the first lens and the projection lens body satisfy the following relationship: 1 < |f1 / f| < 2, where f1 is the focal length of the first lens and f is the focal length of the projection lens body.
[0009] Furthermore, the first lens, the second lens, and the projection lens body satisfy the following relationship: 0.8 < |f12 / f| < 1.6, where f12 is the combined focal length of the first lens and the second lens, and f is the focal length of the projection lens body.
[0010] Furthermore, the third lens and the projection lens body satisfy the following relationship: 1.2 < |f3 / f| < 2.2, where f3 is the focal length of the third lens and f is the focal length of the projection lens body.
[0011] Furthermore, the fourth lens and the projection lens body satisfy the following relationship: 0.2 < |f4 / f| < 0.8, where f4 is the focal length of the fourth lens and f is the focal length of the projection lens body.
[0012] Furthermore, the fifth lens and the projection lens body satisfy the following relationship: 0.5 < |f5 / f| < 1.2, where f5 is the focal length of the fifth lens and f is the focal length of the projection lens body.
[0013] Furthermore, the Abbe numbers of the first lens, the second lens, the third lens, and the fifth lens are between 50 and 58, and the Abbe number of the fourth lens is between 30 and 35.
[0014] Furthermore, an aperture is provided inside the housing, and the aperture is positioned between the second lens and the third lens.
[0015] Compared with the prior art, the beneficial effects of this utility model are: by coordinating lenses with different focal lengths, this projection lens can achieve a significant reduction in the overall focal length of the lens without increasing the number of lenses used in the lens by a small amount, and the projection ratio of the lens can reach 0.6, while also having a certain degree of off-axis. Attached Figure Description
[0016] Figure 1 This is a front sectional view of the present invention.
[0017] The attached diagram lists the components represented by each number as follows:
[0018] 1. Projection lens body; 2. Housing; 3. First lens; 4. Second lens; 5. Third lens; 6. Fourth lens; 7. Fifth lens; 8. Aperture. Detailed Implementation
[0019] To make the objectives and advantages of this utility model clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the following text is merely used to describe one or more specific embodiments of this utility model and does not strictly limit the scope of protection specifically claimed by this utility model.
[0020] like Figure 1 As shown, a short-throw projection lens with an off-axis includes a projection lens body 1. The projection lens body 1 includes a housing 2. Inside the housing 2, a first lens 3, a second lens 4, a third lens 5, a fourth lens 6, and a fifth lens 7 are arranged sequentially from the object side to the image side along the axis of the housing 2. The first lens 3 is a spherical lens with negative optical power and a convex object side. The second lens 4 is a spherical lens with positive optical power and a convex object side. The third lens 5 is a spherical lens with positive optical power and a convex object side. The fourth lens 6 is an aspherical lens with negative optical power and a concave object side. The fifth lens 7 is an aspherical lens with positive optical power and a convex object side. The first lens 3, the second lens 4, and the third lens 5 are all made of glass. The fourth lens 6 and the fifth lens 7 are both made of plastic. The Abbe number of the first lens 3, the second lens 4, the third lens 5, and the fifth lens 7 is between 50 and 58. The Abbe number of the fourth lens 6 is between 30 and 35.
[0021] Based on the above structure, the projection lens body 1 adopts a combination of glass spherical mirror and plastic aspherical mirror. By reasonably matching and optimizing lenses with different focal lengths, the focal length can be reduced, the projection ratio can be achieved to 0.6:1, and it has 70% off-axis. Compared with the focal length of fixed-focus lenses in the prior art, it reduces the focal length by 30% and increases the off-axis from 0 to 70%, achieving an excellent experience effect of projecting a large image with off-axis at a short distance, while ensuring that the resolution meets the imaging requirements.
[0022] like Figure 1 As shown, the image-side surface of the first lens 3 is concave, the image-side surface of the second lens 4 is convex, concave, or flat, the image-side surface of the third lens 5 is convex, concave, or flat, the image-side surface of the fourth lens 6 is concave, and the image-side surface of the fifth lens 7 is convex, concave, or flat.
[0023] Based on the above structure, while ensuring the focal length requirements of the first lens 3, the second lens 4, the third lens 5, the fourth lens 6, and the fifth lens 7, the image-side surfaces of the second lens 4, the third lens 5, and the fifth lens 7 can be selected with different shapes to facilitate processing.
[0024] like Figure 1 As shown, the first lens 3 and the projection lens body 1 satisfy the following relationship: 1 < |f1 / f| < 2; the first lens 3, the second lens 4 and the projection lens body 1 satisfy the following relationship: 0.8 < |f12 / f| < 1.6; the third lens 5 and the projection lens body 1 satisfy the following relationship: 1.2 < |f3 / f| < 2.2; the fourth lens 6 and the projection lens body 1 satisfy the following relationship: 0.2 < |f4 / f| < 0.8; and the fifth lens 7 and the projection lens body 1 satisfy the following relationship: 0.5 < |f5 / f| < 1.2, where f1 is the focal length of the first lens 3, f12 is the combined focal length of the first lens 3 and the second lens 4, f3 is the focal length of the third lens 5, f4 is the focal length of the fourth lens 6, f5 is the focal length of the fifth lens 7, and f is the focal length of the projection lens body 1.
[0025] According to the above structure, the first lens 3 is used to collect light and is suitable for lenses with a large field of view. At the same time, since the shape of the lens has an important influence on distortion and imaging effect, in order to improve the imaging effect, the design of the first lens 3 satisfies 5 < |ET1 / CT1| < 10, where CT1 is the center thickness of the first lens 3 and ET1 is the edge thickness of the first lens 3 along the axial direction. The first lens 3 and the second lens 4 work together to converge the collected light to the third lens 5. The fourth lens 6 and the projection lens body 1 satisfy 0.2 < |f4 / f| < 0.8, which can effectively correct aberrations such as coma, astigmatism, and field curvature. In order to ensure that the fourth lens 6 has good manufacturability, it is required that 2 < |ET4 / CT4| < 3.2, where CT4 is the center thickness of the fourth lens 6 and ET4 is the edge thickness of the fourth lens 6 along the axial direction. The fifth lens 7 and the projection lens body 1 satisfy 0.5 < |f5 / f| < 1.2 to correct residual aberrations.
[0026] like Figure 1 As shown, in order to adjust the intensity of the passing light beam, an aperture 8 is provided inside the housing 2, and the aperture 8 is positioned between the second lens 4 and the third lens 5.
[0027] The working principle of this utility model is as follows: The projection lens body 1 adopts a combination of glass spherical mirror and plastic aspherical mirror. By reasonably matching and optimizing lenses with different focal lengths, the focal length can be reduced, achieving a projection ratio of 0.6:1, and with 70% off-axis, which reduces the focal length by 30% compared to the fixed-focus lenses in the prior art, and increases the off-axis from 0 to 70%. This achieves an excellent experience of projecting a large image with off-axis at a short distance, while ensuring that the resolution meets the imaging requirements. The first lens 3 is used to collect light and is suitable for lenses with a large field of view. At the same time, due to the shape of the lens, distortion and imaging effect are affected. This has a significant impact. To improve imaging performance, the design of the first lens 3 satisfies 5 < |ET1 / CT1| < 10. The first lens 3 and the second lens 4 work together to converge the collected light rays onto the third lens 5. The fourth lens 6 and the projection lens body 1 satisfy 0.2 < |f4 / f| < 0.8, which can effectively correct aberrations such as coma, astigmatism, and field curvature. To ensure good manufacturability of the fourth lens 6, 2 < |ET4 / CT4| < 3.2 is required. The fifth lens 7 and the projection lens body 1 satisfy 0.5 < |f5 / f| < 1.2 to correct residual aberrations.
[0028] The above description is merely a preferred embodiment of this utility model. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of this utility model, and these improvements and modifications should also be considered within the scope of protection of this utility model. Structures, devices, and operating methods not specifically described or explained in this utility model, unless otherwise specified or limited, shall be implemented using conventional methods in the field.
Claims
1. A short-throw projection lens with an off-axis, comprising a projection lens body (1), characterized in that: The projection lens body (1) includes a housing (2). Inside the housing (2) are arranged a first lens (3), a second lens (4), a third lens (5), a fourth lens (6) and a fifth lens (7) arranged sequentially from the object side to the image side along the axial direction of the housing (2). The first lens (3) is a spherical lens with negative optical power and a convex object side. The second lens (4) is a spherical lens with positive optical power and a convex object side. The third lens (5) is a spherical lens with positive optical power and a convex object side. The fourth lens (6) is an aspherical lens with negative optical power and a concave object side. The fifth lens (7) is an aspherical lens with positive optical power and a convex object side.
2. A short-throw projection lens with off-axis according to claim 1, characterized in that: The first lens (3), the second lens (4) and the third lens (5) are all made of glass, while the fourth lens (6) and the fifth lens (7) are all made of plastic.
3. A short-throw projection lens with off-axis according to claim 1, characterized in that: The image-side surface of the first lens (3) is concave, the image-side surface of the second lens (4) is convex, concave or flat, the image-side surface of the third lens (5) is convex, concave or flat, the image-side surface of the fourth lens (6) is concave, and the image-side surface of the fifth lens (7) is convex, concave or flat.
4. A short-throw projection lens with off-axis according to claim 1, characterized in that: The first lens (3) and the projection lens body (1) satisfy the following relationship: 1<|f1 / f|<2, where f1 is the focal length of the first lens (3) and f is the focal length of the projection lens body (1).
5. A short-throw projection lens with off-axis according to claim 1, characterized in that: The first lens (3), the second lens (4) and the projection lens body (1) satisfy the following relationship: 0.8 < |f12 / f| < 1.6, where f12 is the combined focal length of the first lens (3) and the second lens (4), and f is the focal length of the projection lens body (1).
6. A short-throw projection lens with off-axis according to claim 1, characterized in that: The third lens (5) and the projection lens body (1) satisfy the following relationship: 1.2 < |f3 / f| < 2.2, where f3 is the focal length of the third lens (5) and f is the focal length of the projection lens body (1).
7. A short-throw projection lens with off-axis according to claim 1, characterized in that: The fourth lens (6) and the projection lens body (1) satisfy the following relationship: 0.2 < |f4 / f| < 0.8, where f4 is the focal length of the fourth lens (6) and f is the focal length of the projection lens body (1).
8. A short-throw projection lens with off-axis according to claim 1, characterized in that: The fifth lens (7) and the projection lens body (1) satisfy the following relationship: 0.5 < |f5 / f| < 1.2, where f5 is the focal length of the fifth lens (7) and f is the focal length of the projection lens body (1).
9. A short-throw projection lens with off-axis according to claim 1, characterized in that: The Abbe numbers of the first lens (3), the second lens (4), the third lens (5) and the fifth lens (7) are between 50 and 58, and the Abbe number of the fourth lens (6) is between 30 and 35.
10. A short-throw projection lens with an off-axis according to claim 1, characterized in that: An aperture (8) is provided inside the outer casing (2), and the aperture (8) is positioned between the second lens (4) and the third lens (5).