Projection optical system

Abstract

The invention discloses a projection optical system, relates to the technical field of optical projection, and can obtain clear pictures under different projection distances by moving a movable lens group in a focusing group. By moving the movable lens group in the zoom group, pictures with different sizes can be obtained under the condition that the projection distance is not changed. Through the mutual cooperation of the lens groups, a large picture can be projected in a short distance, the continuous magnification zooming is realized, the imaging quality is high, and the 4K resolution can be supported.

Description

Technical Field

[0001] The present invention relates to the technical field of optical projection, and in particular to a projection optical system which can project a large image in a short distance and achieve high imaging quality while realizing continuous magnification zoom. Background Art

[0002] Laser display projection technology is a new type of display projection technology on the market. Laser projectors that currently use this technology can achieve the function of automatic focusing, and laser projectors that can achieve the automatic focusing function are also called automatic focusing projectors. Among them, focusing refers to adjusting the position of the projector's focal point to adjust the projector's image distance.

[0003] The focus projector includes a driving component and a projection lens, wherein the projection lens includes a focusing lens group for focusing. When the projection lens projects onto a screen and the distance between the projection lens and the screen changes, the driving component can control each focusing lens in the focusing lens group to move along the optical axis of the focusing lens group according to a pre-configured correspondence between the distance and the image distance.

[0004] With the development of projection technology, the application scenarios of projectors are becoming more and more diverse. When users need to project a large image at a short distance, they will choose a short-focus lens. Traditional short-focus lenses are mainly fixed-focus, and different image sizes can only be achieved by changing the projection distance, which is difficult to meet the increasing complex needs of users. In addition, traditional zoom projection lenses are mainly medium-to-long-focus, and a long projection distance is required to project a large image, which causes trouble for users with limited space. Summary of the invention

[0005] The invention provides a projection optical system.

[0006] The present invention provides the following scheme:

[0007] A projection optical system, comprising a front fixed group, a focus group, a zoom group and a rear fixed group in sequence from the object side to the image side along the optical axis direction;

[0008] The front fixed group includes a first lens group, the first lens group includes at least one meniscus aspheric lens, the meniscus aspheric lens has negative optical power, and the meniscus aspheric lens is used to eliminate distortion aberration and reduce the aperture of the front end of the optical system;

[0009] The focus adjustment group at least includes a second lens group and a third lens group that can be moved along the optical axis, and the second lens group and the third lens group are moved so as to obtain a clear picture at different projection distances;

[0010] The zoom group at least includes a fourth lens group, a fifth lens group and a sixth lens group that can be moved along the optical axis direction, and the fourth lens group, the fifth lens group and the sixth lens group are moved so as to obtain images of different sizes without changing the projection distance;

[0011] The rear fixed group includes a seventh lens group having positive optical power.

[0012] Preferably, the Abbe number of the meniscus aspherical lens is between 40 and 60, and the maximum aperture D of the front fixed group and the total length L of the entire optical system satisfy the following relationship:

[0013] 0.3 <D / L<0.4。

[0014] Preferably, the focal length f1 of the front fixed lens group and the minimum focal length fw obtained by moving the second lens group and the third lens group of the variable magnification group satisfy the following relationship:

[0015] -0.15 <f1 / fw<-0.05。

[0016] Preferably, the focal length f1 of the front fixed group and the focal length f2 of the focusing group satisfy the following relationship:

[0017] 0.4 <f1 / f2<0.6。

[0018] Preferably: the second lens group includes a second lens and a third lens, the second lens is a meniscus type negative power lens, and the third lens is a biconcave negative power aspherical lens;

[0019] The third lens group includes a fourth lens with a biconvex positive focal power and a fifth lens with a meniscus negative focal power, and the fourth lens and the fifth lens form a cemented lens.

[0020] Preferably, the minimum focal length fw obtained by moving the fourth lens group, the fifth lens group and the sixth lens group and the total length L of the entire optical projection system satisfy the following relationship:

[0021] 0.015 <fw / L<0.025

[0022] The maximum field of view FOV obtained by moving the fourth lens group, the fifth lens group, and the sixth lens group satisfies the following relationship:

[0023] 110° <FOV<130°

[0024] During the movement of the fourth lens group, the fifth lens group, and the sixth lens group, the optical distortion of the entire optical system maintains the following relationship:

[0025] -2% <distortion<2%。

[0026] Preferably: the fourth lens group includes a sixth lens and a seventh lens, the sixth lens is a biconcave lens with negative focal length, and the seventh lens is a biconvex lens with positive focal length;

[0027] The fifth lens group includes an eighth lens, a ninth lens and a tenth lens; the eighth lens with biconvex positive focal power and the ninth lens with biconcave negative focal power form a cemented lens, and the tenth lens is a meniscus positive focal power lens;

[0028] The sixth lens group includes an eleventh lens, a twelfth lens, a thirteenth lens, a fourteenth lens, a fifteenth lens, a sixteenth lens, a seventeenth lens, an eighteenth lens and a nineteenth lens; the eleventh lens is a biconcave negative power aspheric lens, the twelfth lens is a meniscus positive power aspheric lens, the thirteenth lens with plano-concave negative power, the fourteenth lens with biconvex positive power and the fifteenth lens with meniscus negative power form a triplet lens, the sixteenth lens with biconvex positive power, the seventeenth lens with biconcave negative power and the eighteenth lens with meniscus positive power form a triplet lens, and the nineteenth lens is a biconvex positive power aspheric lens.

[0029] Preferably: a stop is arranged on the plane of the thirteenth lens.

[0030] Preferably, the seventh lens group includes a twentieth lens; the twentieth lens is a biconvex positive power lens.

[0031] Preferably, the focal length f3 of the rear fixed group and the minimum focal length fw obtained by moving at least three lens groups of the zoom group satisfy the following relationship:

[0032] 0.05 <f3 / fw<0.15

[0033] The back focus BFL of the optical system and the total length L of the entire optical projection system satisfy the following relationship:

[0034] 0.1 <BFL / L<0.2。

[0035] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0036] Through the present invention, a projection optical system can be realized. In one implementation mode, by moving the movable lens group in the focus group, a clear picture can be obtained at different projection distances. By moving the movable lens group in the zoom group, pictures of different sizes can be obtained without changing the projection distance. Through the mutual cooperation of the lens groups, a large picture can be projected in a short distance, and while realizing continuous magnification zoom, the image quality is high and 4K resolution can be supported.

[0037] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0039] Figure 1 is a schematic structural diagram of a projection optical system provided by an embodiment of the present invention;

[0040] Figure 2 1 is a schematic diagram of MTF when the focal length is 5.2 mm and the maximum field angle is 122° provided by an embodiment of the present invention;

[0041] Figure 3 It is a schematic diagram of MTF when the focal length is 5.8 mm and the maximum field angle is 116° provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0043] Example

[0044] See also Figure 1 , is a projection optical system provided by an embodiment of the present invention, such as Figure 1 As shown, the system includes a front fixed group, a focus group, a zoom group and a rear fixed group in sequence from the object side to the image side along the optical axis direction;

[0045] The front fixed group includes a first lens group G1, the first lens group G1 includes at least one meniscus aspheric lens, the meniscus aspheric lens has negative optical power, and the meniscus aspheric lens is used to eliminate distortion aberration and reduce the aperture of the front end of the optical system;

[0046] The focus adjustment group at least includes a second lens group G2 and a third lens group G3 that can be moved along the optical axis, and the second lens group G2 and the third lens group G3 are moved so as to obtain a clear picture at different projection distances;

[0047] The zoom group at least includes a fourth lens group G4, a fifth lens group G5 and a sixth lens group G6 that can move along the optical axis direction, and the fourth lens group G4, the fifth lens group G5 and the sixth lens group G6 are moved so as to obtain images of different sizes without changing the projection distance;

[0048] The rear fixed group includes a seventh lens group G7, and the seventh lens group G7 has positive refractive power.

[0049] The projection optical system provided in the embodiment of the present application comprises at least one aspherical surface in the front fixed group. The focusing group comprises at least two movable lens groups, and by moving the at least two lens groups, a clear picture can be obtained at different projection distances. The zoom group comprises at least three movable lens groups, and by moving the at least three lens groups, pictures of different sizes can be obtained without changing the projection distance.

[0050] In a specific implementation, the embodiment of the present application can provide that the Abbe number of the meniscus aspherical lens is between 40 and 60, and the maximum aperture D of the front fixed group and the total length L of the entire optical system satisfy the following relationship:

[0051] 0.3 <D / L<0.4。

[0052] The front fixed group contains at least one meniscus aspherical lens with negative power and an Abbe number between 40 and 60. The meniscus aspherical surface has a better light collecting effect for light incident at a large angle, which is beneficial to eliminate distortion aberration and reduce the aperture of the front end of the optical system.

[0053] Furthermore, the front fixed lens group remains unchanged relative to the object side and has negative optical power. The focal length f1 of the front fixed lens group and the minimum focal length fw obtained by moving the second lens group G2 and the third lens group G3 of the variable magnification group satisfy the following relationship:

[0054] -0.15 <f1 / fw<-0.05。

[0055] The focal length f1 of the front fixed group and the focal length f2 of the focusing group satisfy the following relationship:

[0056] 0.4 <f1 / f2<0.6。

[0057] The focusing group provided in the embodiment of the present application contains at least two movable lens groups. By moving the at least two lens groups, a clear picture can be obtained at different projection distances. The focusing group contains at least one aspherical lens with negative optical power. In specific implementation, the embodiment of the present application can provide that the second lens group G2 includes a second lens L2 and a third lens L3, the second lens L2 is a meniscus type negative optical power lens, and the third lens L3 is a biconcave negative optical power aspherical lens;

[0058] The third lens group G3 includes a fourth lens L4 with a biconvex positive power and a fifth lens L5 with a meniscus negative power. The fourth lens L4 and the fifth lens L5 form a cemented lens.

[0059] The zoom group provided in the embodiment of the present application contains at least three movable lens groups. By moving the at least three lens groups, pictures of different sizes can be obtained without changing the projection distance.

[0060] The minimum focal length fw obtained by moving the fourth lens group G4, the fifth lens group G5 and the sixth lens group G6 and the total length L of the entire optical projection system satisfy the following relationship:

[0061] 0.015 <fw / L<0.025

[0062] The maximum field of view FOV obtained by moving the fourth lens group G4, the fifth lens group G5 and the sixth lens group G6 satisfies the following relationship:

[0063] 110° <FOV<130°

[0064] During the movement of the fourth lens group G4, the fifth lens group G5 and the sixth lens group G6, the optical distortion of the entire optical system keeps satisfying the following relationship:

[0065] -2% <distortion<2%。

[0066] In a specific implementation, the embodiment of the present application may provide that the fourth lens group G4 includes a sixth lens L6 and a seventh lens L7, the sixth lens L6 is a biconcave lens with negative power, and the seventh lens L7 is a biconvex lens with positive power;

[0067] The fifth lens group G5 includes an eighth lens L8, a ninth lens L9 and a tenth lens L10; the eighth lens L8 with biconvex positive power and the ninth lens L9 with biconcave negative power form a cemented lens, and the tenth lens L10 is a meniscus positive power lens;

[0068] The sixth lens group G6 includes an eleventh lens L11, a twelfth lens L12, a thirteenth lens L13, a fourteenth lens L14, a fifteenth lens L15, a sixteenth lens L16, a seventeenth lens L17, an eighteenth lens L18 and a nineteenth lens L19; the eleventh lens L11 is a biconcave negative power aspheric lens, the twelfth lens L12 is a meniscus positive power aspheric lens, the thirteenth lens L13 with plano-concave negative power, the fourteenth lens L14 with biconvex positive power and the fifteenth lens L15 with meniscus negative power form a triplet lens, the sixteenth lens L16 with biconvex positive power, the seventeenth lens L17 with biconcave negative power and the eighteenth lens L18 with meniscus positive power form a triplet lens, and the nineteenth lens L19 is a biconvex positive power aspheric lens.

[0069] Furthermore, a stop is provided on the plane of the thirteenth lens L13. The zoom group contains at least three movable lens groups, the stop is located in one of the lens groups (the sixth lens group G6), the sixth lens group G6 contains at least two aspherical lenses, one of which is located between the stop and the front fixed group, and its function is to eliminate spherical aberration, and the other is located between the stop and the rear fixed group, and its function is to eliminate field curvature aberration.

[0070] In another implementation, the zoom group contains at least three movable lens groups, the aperture is located in one of the lens groups, the lens group contains at least two cemented lenses, and the cemented lenses contain high-refractive-index and low-dispersion glass, which functions to eliminate chromatic aberration.

[0071] The rear fixed group remains unchanged relative to the object side and has positive power. In specific implementation, the embodiment of the present application may provide that the seventh lens group G7 includes a twentieth lens L20; the twentieth lens L20 is a biconvex positive power lens.

[0072] The focal length f3 of the rear fixed group and the minimum focal length fw obtained by moving at least three lens groups of the variable magnification group satisfy the following relationship:

[0073] 0.05 <f3 / fw<0.15

[0074] The back focus BFL of the optical system and the total length L of the entire optical projection system satisfy the following relationship:

[0075] 0.1 <BFL / L<0.2。

[0076] The following takes an implementation method as an example to verify the effect of the projection optical system provided in the embodiment of the present application.

[0077] From the object side to the image side, there are the front fixed group, the focus group, the zoom group and the rear fixed group. The front fixed group contains the first lens group G1. The focus group contains the second lens group G2 and the third lens group G3, and the two lens groups are movable. The zoom group contains the fourth lens group G4 to the sixth lens group G6, and the three lens groups are movable. The rear fixed group contains the seventh lens group G7.

[0078] The first lens group G1 includes a first lens L1 which is a meniscus type negative power aspherical lens with an Abbe number between 40 and 60.

[0079] The second lens group G2 includes a second lens L2 and a third lens L3, wherein the second lens L2 is a meniscus type negative power lens, and the third lens L3 is a biconcave negative power aspherical lens.

[0080] The third lens group G3 includes a fourth lens L4 and a fifth lens L5, wherein the biconvex fourth lens L4 with positive refractive power and the meniscus fifth lens L5 with negative refractive power form a cemented lens.

[0081] The fourth lens group G4 includes a sixth lens L6 and a seventh lens L7, wherein the sixth lens L6 is a biconcave lens with negative power, and the seventh lens L7 is a biconvex lens with positive power.

[0082] The fifth lens group G5 includes an eighth lens L8 to a tenth lens L10, wherein the biconvex eighth lens L8 with positive refractive power and the biconcave ninth lens L9 with negative refractive power form a cemented lens, and the tenth lens (L10) is a meniscus lens with positive refractive power.

[0083] The sixth lens group G6 includes the eleventh lens L11 to the nineteenth lens L19, wherein the eleventh lens L11 is a biconcave negative power aspheric lens, the twelfth lens L12 is a meniscus positive power aspheric lens, the thirteenth lens L13 of plano-concave negative power, the fourteenth lens L14 of biconvex positive power and the fifteenth lens L15 of meniscus negative power form a triplet lens, the sixteenth lens L16 of biconvex positive power, the seventeenth lens L17 of biconcave negative power and the eighteenth lens L18 of meniscus positive power form a triplet lens, and the nineteenth lens L19 is a biconvex positive power aspheric lens. The aperture is arranged on one side of the plane of the third lens.

[0084] The seventh lens group G7 includes a twentieth lens L20, wherein the twentieth lens L20 is a biconvex positive power lens.

[0085] Proven, such as Figure 2 , Figure 3 As shown, by moving the three lens groups of the zoom group, a 1.1x continuous zoom system can be obtained, with a minimum focal length of 5.2mm (the corresponding maximum field of view angle is 122°) and a maximum focal length of 5.8mm (the corresponding maximum field of view angle is 116°). The optical data are shown in Table 1.

[0086] Table 1 Optical data table

[0087]

[0088]

[0089] Wherein, R represents the radius of curvature of the lens, d represents the lens thickness or air space, nd represents the refractive index of the glass, and vd represents the Abbe number of the glass. The data of the air spaces D0 to D3 are shown in Table 2.

[0090] Table 2 Data table of air intervals D0 to D3

[0091]

[0092]

[0093] Table 2 shows the change in air spacing between zoom groups at different focal lengths, achieving a 1.1x zoom.

[0094] The aspheric surfaces described in Table 1 are all even-order aspheric surfaces, and their expressions are as follows:

[0095]

[0096] Among them, z is the aspheric surface vertex height when the aspheric surface is at a height of r along the optical axis, c represents the vertex curvature of the surface, k is the conic coefficient of the aspheric surface, and α2, α3, α4, α5, α6, α7, and α8 are high-order aspheric surface coefficients. The statistics of the conic coefficients are shown in Table 3.

[0097] Table 3

[0098] Surface number k 4th-order term 6th order term 8th order term 10th order term 12th order term 14th order term 16th order term 1 0 1.67E-05 -1.75E-08 1.46E-11 -8.79E-15 3.69E-18 -9.57E-22 1.18E-25 2 -1.17 -1.50E-07 4.08E-08 -9.17E-11 4.14E-14 5.04E-17 -5.63E-20 1.56E-23 5 0 -5.34E-05 1.97E-07 -2.74E-10 1.44E-13 0.00E+00 0.00E+00 0.00E+00 6 0 -4.07E-05 2.01E-07 -2.58E-10 2.72E-13 0.00E+00 0.00E+00 0.00E+00 19 0 -5.34E-05 1.97E-07 -2.74E-10 1.44E-13 0.00E+00 0.00E+00 0.00E+00 20 0 -4.07E-05 2.01E-07 -2.58E-10 2.72E-13 0.00E+00 0.00E+00 0.00E+00 21 0 -3.29E-05 7.73E-08 -4.01E-10 1.92E-12 -5.74E-15 5.66E-18 0.00E+00 22 0 6.84E-06 2.06E-09 1.51E-10 -1.16E-12 5.07E-15 -8.40E-18 0.00E+00 31 0 -5.34E-05 1.97E-07 -2.74E-10 1.44E-13 0.00E+00 0.00E+00 0.00E+00 32 0 -4.07E-05 2.01E-07 -2.58E-10 2.72E-13 0.00E+00 0.00E+00 0.00E+00

[0099] In summary, the projection optical system provided by the present application can obtain a clear picture at different projection distances by moving the movable lens group in the focus group. By moving the movable lens group in the zoom group, pictures of different sizes can be obtained without changing the projection distance. Through the mutual cooperation of the lens groups, a large picture can be projected in a short distance, and while achieving continuous magnification zoom, the image quality is high and can support 4K resolution.

[0100] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0101] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A projection optical system, characterized in that: Along the optical axis direction from the object side to the image side, it includes a front fixed group, a focus group, a zoom group and a rear fixed group; The front fixed group includes a first lens group, the first lens group includes at least one meniscus aspheric lens, the meniscus aspheric lens has negative optical power, and the meniscus aspheric lens is used to eliminate distortion aberration and reduce the aperture of the front end of the optical system; The focus adjustment group at least includes a second lens group and a third lens group that can be moved along the optical axis, and the second lens group and the third lens group are moved so as to obtain a clear picture at different projection distances; The zoom group at least includes a fourth lens group, a fifth lens group and a sixth lens group that can be moved along the optical axis direction, and the fourth lens group, the fifth lens group and the sixth lens group are moved so as to obtain images of different sizes without changing the projection distance; The rear fixed group includes a seventh lens group having positive optical power.

2. The projection optical system according to claim 1, characterized in that: The Abbe number of the meniscus aspherical lens is between 40 and 60, and the maximum aperture D of the front fixed group and the total length L of the entire optical system satisfy the following relationship: 0.3 <D / L<0.4。 3. The projection optical system according to claim 1, characterized in that: The focal length f1 of the front fixed lens group and the minimum focal length fw obtained by moving the second lens group and the third lens group of the variable magnification group satisfy the following relationship: -0.15 <f1 / fw<-0.05。 4. The projection optical system according to claim 1, characterized in that: The focal length f1 of the front fixed group and the focal length f2 of the focusing group satisfy the following relationship: 0.4 <f1 / f2<0.6。 5. The projection optical system according to claim 1, characterized in that: The second lens group includes a second lens and a third lens, the second lens is a meniscus type negative power lens, and the third lens is a biconcave negative power aspherical lens; The third lens group includes a fourth lens with a biconvex positive focal power and a fifth lens with a meniscus negative focal power, and the fourth lens and the fifth lens form a cemented lens.

6. The projection optical system according to claim 1, characterized in that: The minimum focal length fw obtained by moving the fourth lens group, the fifth lens group, and the sixth lens group and the total length L of the entire optical projection system satisfy the following relationship: 0.015 <fw / L<0.025 The maximum field of view FOV obtained by moving the fourth lens group, the fifth lens group, and the sixth lens group satisfies the following relationship: 110° <FOV<130° During the movement of the fourth lens group, the fifth lens group, and the sixth lens group, the optical distortion of the entire optical system maintains the following relationship: -2% <distortion<2%。 7. The projection optical system according to claim 1, characterized in that: The fourth lens group includes a sixth lens and a seventh lens, the sixth lens is a biconcave lens with negative power, and the seventh lens is a biconvex lens with positive power; The fifth lens group includes an eighth lens, a ninth lens and a tenth lens; the eighth lens with biconvex positive focal power and the ninth lens with biconcave negative focal power form a cemented lens, and the tenth lens is a meniscus positive focal power lens; The sixth lens group includes an eleventh lens, a twelfth lens, a thirteenth lens, a fourteenth lens, a fifteenth lens, a sixteenth lens, a seventeenth lens, an eighteenth lens and a nineteenth lens; the eleventh lens is a biconcave negative power aspheric lens, the twelfth lens is a meniscus positive power aspheric lens, the thirteenth lens with plano-concave negative power, the fourteenth lens with biconvex positive power and the fifteenth lens with meniscus negative power form a triplet lens, the sixteenth lens with biconvex positive power, the seventeenth lens with biconcave negative power and the eighteenth lens with meniscus positive power form a triplet lens, and the nineteenth lens is a biconvex positive power aspheric lens.

8. The projection optical system according to claim 7, characterized in that: A stop is arranged on the plane of the thirteenth lens.

9. The projection optical system according to claim 1, characterized in that: The seventh lens group includes a twentieth lens; the twentieth lens is a biconvex positive power lens.

10. The projection optical system according to claim 1, characterized in that: The focal length f3 of the rear fixed group and the minimum focal length fw obtained by moving at least three lens groups of the variable magnification group satisfy the following relationship: 0.05 <f3 / fw<0.15 The back focus BFL of the optical system and the total length L of the entire optical projection system satisfy the following relationship: 0.1 <BFL / L<0.2。

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