Optical lens for projection

Abstract

The present invention provides an optical lens for projection, which comprises: a concave reflector arranged in sequence from the object side to the image side, a first lens group with negative optical power, a second lens group with positive optical power moving forward and backward along the optical axis of the optical lens for projection, a third lens group with positive optical power and a galvanometer, and an aperture is arranged between the lenses of the third lens group; the first lens group comprises a first lens, a second lens and a third lens arranged in sequence, the first lens faces the concave reflector; the incident surface of the third lens is a concave surface facing the second lens group, and the exit surface is a convex surface facing the second lens. The present invention has the advantages of no distortion at a large angle, large aperture, image telecentricity, 4K imaging, etc.

Description

Technical Field

[0001] The invention relates to an optical lens, in particular to an optical lens for ultra-short-throw projection. Background Art

[0002] At present, projectors have been widely used, such as in the education industry. The optical lens for projection is the core module of the projector, but it usually has shortcomings such as large spherical aberration, poor peripheral image quality, large length, greater distortion with larger angles, large astigmatism and axial chromatic aberration, such as:

[0003] CN2018104678873 discloses a projection optical system with an ultra-large projection range, which specifically includes: a first lens group that is stationary relative to the DMD chip is arranged between the DMD chip and the reflector, and the optical focal length of the first lens group is negative; a second lens group that can move between the DMD chip and the first lens group is arranged between the DMD chip and the first lens group, and the optical focal length of the second lens group is positive; a third lens group that can move between the DMD chip and the second lens group is arranged between the DMD chip and the second lens group, and the optical focal length of the third lens group is negative; a fourth lens group that is stationary relative to the DMD chip is arranged between the DMD chip and the third lens group, and the optical focal length of the fourth lens group is positive.

[0004] CN2017203198140 discloses an ultra-short-focus projection optical device, which specifically includes: a first lens group that can move forward and backward relative to a DMD chip, and the optical focal length of the first lens group is positive; a second lens group that can move forward and backward relative to the DMD chip, and the optical focal length of the second lens group is positive; a third lens group that can move forward and backward relative to the DMD chip, and the optical focal length of the third lens group is negative; and a fourth lens group that is stationary relative to the DMD chip, and the optical focal length of the fourth lens group is positive. Summary of the invention

[0005] In order to solve the deficiencies in the above-mentioned prior art solutions, the present invention provides an optical lens for projection with good reliability, large aperture, large angle, no distortion, image-space telecentricity, and 4K imaging.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] An optical lens for projection, comprising:

[0008] A concave reflecting mirror, a first lens group with negative optical power, a second lens group with positive optical power and movable in the positive and reverse directions along the optical axis of the projection optical lens, a third lens group with positive optical power and a galvanometer are sequentially arranged from the object side to the image side; the third lens group includes at least two lenses, and a stop is arranged between the lenses of the third lens group;

[0009] The first lens group includes a first lens, a second lens and a third lens arranged in sequence, the first lens is adjacent to the concave reflector, and the focal length satisfies:

[0010] f 11 is the focal length of the first lens, f 12 is the focal length of the second lens, f 13 is the focal length of the third lens, f 1 is the focal length of the first lens group;

[0011] The incident surface of the third lens is a concave surface facing the second lens group and concave into the third lens, and the exit surface is a convex surface facing the second lens and arched toward the second lens, and satisfies:

[0012] R 32 is the radius of curvature of the incident surface, R 31 is the radius of curvature of the exit surface.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] 1. Good reliability;

[0015] Fewer second lens groups, i.e., fewer moving lenses, reduce structural complexity and cost, and improve operational reliability;

[0016] 2. No distortion at large angles;

[0017] The first lens group is used to correct the overall distortion of the system. It adopts a three-lens structure with a negative-negative-positive focal power. The first two negative lenses allow the light to diverge sufficiently to ensure the designed field of view, while the last positive lens converges and corrects the distortion.

[0018] The third lens is a meniscus lens, and the curvature radii of the front and rear surfaces of the lens satisfy a certain ratio relationship, so that the final deflection of the light at the first lens group can correct the distortion value introduced by the excessive field angle;

[0019] 3. Large aperture;

[0020] The second lens group is a cemented lens structure design. Compared with the movement of a single lens, the cemented lens can not only adjust the aberration caused by the change of the image size during the movement, but also adjust the spherical aberration and coma introduced by the large aperture.

[0021] 4. High peripheral brightness ratio;

[0022] The first lens of the third lens group behind the aperture is an aspherical lens, and the focal length of the lens and the distance (from the lens to the aperture) meet special conditions, ensuring image quality while having a high peripheral brightness ratio, thereby improving the overall efficiency of the lens;

[0023] 5. 4K imaging is achieved;

[0024] The third lens group includes at least one aspherical lens, especially the lens facing (i.e., closest to) the aperture, whose refractive index and Abbe number are specially designed to ensure that the coma meets the requirements of 4K imaging;

[0025] 6. Like Fang Yuanxin;

[0026] The third lens group uses a combination of triplet and doublet lenses to make the divergence angles of the upper and lower rays closer, thus ensuring that the telecentricity of the lens is less than 0.1 degrees. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The disclosure of the present invention will become easier to understand with reference to the accompanying drawings. It is easy for those skilled in the art to understand that these drawings are only used to illustrate the technical solution of the present invention and are not intended to limit the scope of protection of the present invention. In the drawings:

[0028] Figure 1 is a simplified structural diagram of an optical lens for projection according to Embodiment 1-2 of the present invention;

[0029] Figure 2 1 is a simplified structural diagram of an optical lens for projection according to Embodiment 3 of the present invention. DETAILED DESCRIPTION

[0030] Figure 1-2 The following description describes optional embodiments of the present invention to teach those skilled in the art how to implement and reproduce the present invention. In order to teach the technical solution of the present invention, some conventional aspects have been simplified or omitted. Those skilled in the art should understand that variations or substitutions derived from these embodiments will be within the scope of the present invention. Those skilled in the art should understand that the following features can be combined in various ways to form multiple variations of the present invention. Thus, the present invention is not limited to the following optional embodiments, but is only limited by the claims and their equivalents. In the following embodiments, when the unit of focal length is not marked, the unit of focal length is millimeter.

[0031] Embodiment 1:

[0032] Figure 1 The structure diagram of the projection optical lens of the first embodiment of the present invention is schematically shown. Figure 1 As shown, the projection optical lens includes:

[0033] A concave reflector 1, a first lens group with negative focal length, a second lens group with positive focal length that moves in the positive and reverse directions along the optical axis of the projection optical lens, a third lens group with positive focal length, and a galvanometer are sequentially arranged from the object side to the image side. The third lens group can be fixedly arranged, preferably, the third lens group can also be arranged movably, and can be used to adjust the distance between the sensor, that is, to adaptively adjust the distance between the sensor and the image plane, and the adjustment range is very small. The third lens group includes at least two lenses, and the aperture A1 is arranged between the lenses of the third lens group.

[0034] The first lens group includes a first lens, a second lens and a third lens arranged in sequence, the first lens is adjacent to the concave reflector, and the focal length satisfies:

[0035] f 11 is the focal length of the first lens, f 12 is the focal length of the second lens, f 13 is the focal length of the third lens, f 1 is the focal length of the first lens group;

[0036] The incident surface of the third lens is a concave surface facing the second lens group and concave into the third lens, and the exit surface is a convex surface facing the second lens and arched toward the second lens, and satisfies:

[0037] R 32 is the radius of curvature of the incident surface, R 31 is the radius of curvature of the exit surface.

[0038] Furthermore, the relative aperture FNo of the projection optical lens satisfies: FNo∈[1.8,2.4].

[0039] In order to obtain a large aperture, further, the second lens group includes a fourth lens and a fifth lens cemented together, and the focal length satisfies:

[0040] f 21 is the focal length of the fourth lens, f 22 is the focal length of the fifth lens, f 2 is the focal length of the second lens group.

[0041] In order to obtain image telecentricity, further, the third lens group includes:

[0042] The triplet lens group includes three lenses with positive, negative and positive optical powers arranged in sequence; the focal length f of the triplet lens group is 3-0-3 satisfy: f 3is the focal length of the third lens group. Further, 20 mm ≤ |f 3-0-3 |≤30mm.

[0043] The two-cemented lens group includes two lenses with negative and positive focal powers arranged in sequence, and the focal length of the two-cemented lens group is f 3-0-2 and the focal length f of the triplet 3-0-3 satisfy:

[0044] The light passes through the two-cemented lens group, the three-cemented lens group and the aperture in sequence. In the current arrangement state, the lens arrangement is better, there are no two consecutive lenses with negative focal power, and the chromatic aberration is good.

[0045] In order to obtain a high peripheral brightness ratio, further, the third lens group includes:

[0046] The sixth lens is an aspherical lens, disposed between the second lens group and the aperture, and satisfies:

[0047] f 3-0-1 is the focal length of the sixth lens, and d is the distance from the sixth lens to the aperture stop.

[0048] In order to meet the requirements of 4K imaging, further, the sixth lens element meets the following requirements:

[0049] 1.95≤N d6 ≤2.05, 25≤V d6 ≤30, N d6 is the refractive index of the sixth lens, V d6 is the Abbe number of the sixth lens.

[0050] According to the above-mentioned optical lens for projection, preferably, the focal length f of the first lens group is 1 , the focal length f of the second lens group 2 , the focal length f of the third lens group 3 , the focal length f of the projection optical lens satisfies:

[0051] For example, f 1 ∈[-25mm,-15mm],f 2 ∈[30mm,45mm],f 3 ∈[20mm,30mm], f∈[1.6mm,2.4mm].

[0052] The surface of the lens of the third lens group adjacent to the galvanometer mirror facing the galvanometer mirror is a concave surface that is recessed into the lens, and the surface away from the galvanometer mirror is a convex surface that is arched outward from the lens, so that the lens adjacent to the galvanometer mirror bends in the direction away from the galvanometer mirror, which is conducive to telecentric design.

[0053] Embodiment 2:

[0054] This is an application example of the projection optical lens according to Embodiment 1 of the present invention.

[0055] like Figure 1 As shown, in this application example;

[0056] The reflecting surface of the concave reflecting mirror 1 is an aspherical surface;

[0057] The first lens group includes:

[0058] The focal length of the first lens group is f, which is composed of a negative aspherical lens G1, a negative spherical lens G2, and a positive spherical lens G3. 1 ∈[-25mm,-15mm]; the focal length of lenses G1-G3 satisfies:

[0059] f 11 is the focal length of lens G1, f 12 is the focal length of lens G2, f 13 is the focal length of lens G3;

[0060] The incident surface of lens G3 is a concave surface facing the second lens group, and the exit surface is a convex surface facing lens G2, and they satisfy: R 32 is the radius of curvature of the incident surface, R 31 is the radius of curvature of the exit surface.

[0061] The second lens group includes: a lens G4 with negative focal power and a lens G5 with positive focal power, which are cemented together, and the focal lengths satisfy: f 21 is the focal length of lens G4, f 22 is the focal length of lens G5, f 2 is the focal length of the second lens group;

[0062] The third lens group includes:

[0063] The lenses G6-G13 with optical focal powers of negative, positive, positive, negative, positive, negative, positive, positive and positive are arranged in sequence from the object side to the image side along the optical axis, among which: the lens G6 between the lens G5 and the aperture is an aspheric lens; the lens G7 is an aspheric lens, the lenses G8-G10 are a triplet lens group, and the lenses G11-G12 are a doublet lens group; the lens G13 facing the galvanometer is bent in the direction away from the galvanometer, which is conducive to the telecentric design.

[0064] Table 1: Lens structural parameters.

[0065]

[0066]

[0067] Table 2: Parameters of various aspherical lenses

[0068]

[0069] Table 3: Thickness variable table

[0070] 80 inches 100 inches 120 inches D1 -376 -470 -564 D2 10.89 10.59 10.37 D3 1.73 2 2.2

[0071] Embodiment 3:

[0072] This is an application example of the projection optical lens according to Embodiment 1 of the present invention.

[0073] like Figure 2 As shown, in this application example;

[0074] The reflecting surface of the concave reflecting mirror 1 is an aspherical surface;

[0075] The first lens group includes:

[0076] The focal length of the first lens group is f, which is composed of a negative aspherical lens G1, a negative spherical lens G2, and a positive spherical lens G3. 1 ∈[-25mm,-15mm]; the focal length of lenses G1-G3 satisfies: f 11 is the focal length of lens G1, f 12 is the focal length of lens G2, f 13 is the focal length of lens G3;

[0077] The incident surface of lens G3 is a concave surface facing the second lens group, and the exit surface is a convex surface facing lens G2, and they satisfy: R 32 is the radius of curvature of the incident surface, R 31 is the radius of curvature of the exit surface.

[0078] The second lens group includes: a lens G4 with negative focal power and a lens G5 with positive focal power, which are cemented together, and the focal lengths satisfy: f 21 is the focal length of lens G4, f 22 is the focal length of lens G5, f 2 is the focal length of the second lens group;

[0079] The third lens group includes:

[0080] The lenses G6-G12 with optical focal powers of negative, positive, positive, negative, positive, positive and positive are arranged in sequence from the object side to the image side along the optical axis, among which: the lens G6 between the lens G5 and the aperture A1 is an aspheric lens; the lens G7 is an aspheric lens, and the lenses G8-G10 are a group of three cemented lenses; the lens G12 facing the galvanometer is bent in the direction away from the galvanometer, which is conducive to the telecentric design.

[0081] Table 4: Lens structural parameters.

[0082]

[0083]

[0084] Table 5: Parameters of various aspherical lenses

[0085]

[0086] Table 6: Thickness variable table

[0087] 80 inches 100 inches 120 inches D1 -372 -465 -558 D2 10.31 10.61 10.39 D3 1.73 2 2.2

[0088] The optical parameters of the projection optical lens according to the above-mentioned embodiment 2-3 are:

[0089] Lens parameters Example 1 Example 2 focal length 2mm 2mm Field of view 155° 155° F number (aperture) 2.3 2.3 Throw Ratio 0.2 0.2 full length Within 190mm Within 190mm Optical distortion Less than 0.2% Less than 0.2% Telecentricity Less than 0.1 degree Less than 1 degree

[0090] As can be seen from the above, in the third lens group, the continuous use of a triplet and a doublet lens (Example 2) is significantly better than the combination of a triplet and a single lens (Example 3) in terms of telecentricity.

Claims

1. An optical lens for projection, characterized in that: The projection optical lens comprises: A concave reflecting mirror, a first lens group with negative optical power, a second lens group with positive optical power and movable in the positive and reverse directions along the optical axis of the projection optical lens, a third lens group with positive optical power and a galvanometer are sequentially arranged from the object side to the image side; the third lens group includes at least two lenses, and a stop is arranged between the lenses of the third lens group; The first lens group includes a first lens, a second lens and a third lens arranged in sequence, the first lens is adjacent to the concave reflector, and the focal length satisfies: f 11 is the focal length of the first lens, f 12 is the focal length of the second lens, f 13 is the focal length of the third lens, and f1 is the focal length of the first lens group; The incident surface of the third lens is a concave surface facing the second lens group and concave into the third lens, and the exit surface is a convex surface facing the second lens and arched toward the second lens, and satisfies: R 32 is the radius of curvature of the incident surface, R 31 is the radius of curvature of the exit surface; The third lens is a meniscus lens, which is used for the final deflection of light in the first lens group to correct the distortion value introduced by the large field of view. The second lens group includes a fourth lens and a fifth lens cemented together, and the focal length satisfies: f 21 is the focal length of the fourth lens, f 22 is the focal length of the fifth lens; f2 is the focal length of the second lens group.

2. The projection optical lens according to claim 1, characterized in that: The third lens group comprises: The triplet lens group includes three lenses with positive, negative and positive optical powers arranged in sequence; the focal length f of the triplet lens group is 3-0-3 satisfy: f3 is the focal length of the third lens group; The two-cemented lens group includes two lenses with negative and positive focal powers arranged in sequence, and the focal length of the two-cemented lens group is f 3-0-2 and the focal length f of the triplet 3-0-3 satisfy:

3. The projection optical lens according to claim 2, characterized in that: The light passes through the doublet lens group, the triplet lens group and the aperture in sequence.

4. The projection optical lens according to claim 1, characterized in that: The third lens group comprises: The sixth lens is an aspherical lens, disposed between the second lens group and the aperture, and satisfies: f 3-0-1 is the focal length of the sixth lens, and d is the distance from the sixth lens to the aperture stop.

5. The projection optical lens according to claim 4, characterized in that: The sixth lens satisfies: 1.95≤N d6 ≤2.05, 25≤V d6 ≤30, N d6 is the refractive index of the sixth lens, V d6 is the Abbe number of the sixth lens.

6. The projection optical lens according to claim 1, characterized in that: The focal length f1 of the first lens group, the focal length f2 of the second lens group, the focal length f3 of the third lens group, and the focal length f of the projection optical lens satisfy:

7. The projection optical lens according to claim 6, characterized in that: f1∈[-25mm,-15mm], f2∈[30mm,45mm], f3∈[20mm,30mm], f∈[1.6mm,2.4mm].

8. The projection optical lens according to claim 1, characterized in that: The surface of the lens of the third lens group adjacent to the galvanometer mirror and facing the galvanometer mirror is a concave surface that is recessed into the lens, and the surface that is away from the galvanometer mirror is a convex surface that is arched outward from the lens.

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