Projection optical system

Abstract

The application discloses a projection optical system and relates to the technical field of optical projection. By moving the movable lens group in the focusing group, a clear picture can be obtained at different projection distances. By moving the movable lens group in the zoom group, a picture of different sizes can be obtained without changing the projection distance. Through the cooperation of the lens groups, a large picture can be projected in a short distance, and the imaging quality is high, and 4K resolution can be supported while realizing continuous zooming.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical projection technology, in particular to a projection optical system capable of projecting a large screen in a short distance and achieving continuous zooming while obtaining high imaging quality. BACKGROUND

[0002] Laser display projection technology is a new type of display projection technology on the market. The laser projector using this technology can realize automatic focusing function. The laser projector capable of automatic focusing function is also called automatic focusing projector. The focusing refers to adjusting the image distance of the projector by adjusting the position of the focus of the projector.

[0003] The focusing projector includes a driving assembly and a projection lens, and the projection lens includes a focusing lens group for focusing. When the projection lens projects to the screen and the distance between the projection lens and the screen changes, the driving assembly can control each focusing lens in the focusing lens group to move along the optical axis of the focusing lens group according to the corresponding relationship between the distance and the image distance.

[0004] With the development of projection technology, the application scenarios of projectors are becoming more and more diversified. When a large screen needs to be projected in a short distance, users will choose a short-focus lens. However, the traditional short-focus lens is mainly fixed focus, and different screen sizes can only be achieved by changing the projection distance, which is difficult to meet the increasing complex needs of users. In addition, the traditional zoom projection lens is mainly medium or long focus, and a long projection distance is needed to project a large screen, which causes trouble for users with limited space. SUMMARY

[0005] The present application provides a projection optical system.

[0006] The present application provides the following scheme:

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

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

[0009] The focusing group includes at least a second lens group and a third lens group which can move along the optical axis direction, and the second lens group and the third lens group are moved to obtain a clear picture at different projection distances;

[0010] The variable magnification group at least includes a fourth lens group, a fifth lens group and a sixth lens group which are movable along the optical axis, and the fourth lens group, the fifth lens group and the sixth lens group are moved to obtain different sizes of the screen without changing the projection distance.

[0011] The rear fixed group includes a seventh lens group with positive focal length.

[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 whole optical system satisfy the following relationship:

[0013] 0.3 < D / L < 0.4.

[0014] Preferably, the focal length f1 of the front fixed 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 focus 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 negative focal length lens, and the third lens is a double concave negative focal length aspherical lens.

[0019] The third lens group includes a fourth lens with double convex positive focal length and a fifth lens with meniscus negative focal length, 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 whole 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] The optical distortion distortion of the whole optical system during the movement of the fourth lens group, the fifth lens group and the sixth lens group satisfies the following relationship:

[0025] -2%<distortion<2%.

[0026] Preferably, the fourth lens group comprises a sixth lens and a seventh lens, the sixth lens is a double-concave negative power lens, and the seventh lens is a double-convex positive power lens.

[0027] The fifth lens group comprises an eighth lens, a ninth lens and a tenth lens, the eighth lens is a double-convex positive power lens, the ninth lens is a double-concave negative power lens, and the tenth lens is a meniscus positive power lens.

[0028] The sixth lens group comprises 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 double-concave negative power aspheric lens, the twelfth lens is a meniscus positive power aspheric lens, the thirteenth lens is a plane-concave negative power lens, the fourteenth lens is a double-convex positive power lens, the fifteenth lens is a meniscus negative power lens, the sixteenth lens is a double-convex positive power lens, the seventeenth lens is a double-concave negative power lens, the eighteenth lens is a meniscus positive power lens, and the nineteenth lens is a double-convex positive power aspheric lens.

[0029] Preferably, a diaphragm is arranged on the plane of the thirteenth lens.

[0030] Preferably, the seventh lens group comprises a twentieth lens, and the twentieth lens is a double-convex 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 variable magnification group satisfy the following relationship:

[0032] 0.05<f3 / fw<0.15

[0033] The back focal length 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 of the present application, the following technical effects are provided:

[0036] By the present application, a projection optical system can be realized. In an implementation, by moving the movable lens group in the focus adjusting group, a clear picture can be obtained at different projection distances. By moving the movable lens group in the zoom group, a picture of different size can be obtained without changing the projection distance. By the cooperation of the lens groups, a large picture can be projected at a short distance, and the imaging quality is high, and 4K resolution can be supported while realizing continuous zooming.

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

[0038] 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 will be briefly introduced below. Obviously, the drawings in the following description only represent some of the embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort.

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

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

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

[0042] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments only represent some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art belong to the scope of protection of the present application.

[0043] EMBODIMENT

[0044] Reference Figure 1 is a projection optical system provided by an embodiment of the present application, as shown in the figure, the system includes, in order along its optical axis direction from the object side to the image side, a front fixed group, a focus adjusting group, a zoom group and a rear fixed group; Figure 1

[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 focal 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 focusing group includes at least a second lens group G2 and a third lens group G3 which can move along the optical axis direction, and the second lens group G2 and the third lens group G3 are moved to obtain a clear picture at different projection distances.

[0047] The zooming group includes at least a fourth lens group G4, a fifth lens group G5 and a sixth lens group G6 which 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 to obtain pictures of different sizes without changing the projection distance.

[0048] The rear fixed group includes a seventh lens group G7 which has positive focal power.

[0049] The projection optical system provided by the embodiment of the present application includes at least one aspheric lens in the front fixed group, at least two movable lens groups in the focusing group, and at least three movable lens groups in the zooming group.

[0050] In a specific implementation, the Abbe number of the meniscus aspheric 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 includes at least one meniscus aspheric lens which has negative focal power and an Abbe number between 40 and 60. The meniscus aspheric lens has a good light collecting effect on light rays of large angles, which is beneficial to eliminate distortion aberration and reduce the aperture of the front end of the optical system.

[0053] Further, the front fixed group has negative focal power and the position relative to the object side is unchanged. The focal length f1 of the front fixed group and the minimum focal length fw obtained by moving the second lens group G2 and the third lens group G3 of the zooming 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 by the embodiments 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 aspheric lens with negative focal power. In a specific implementation, the second lens group G2 can include a second lens L2 and a third lens L3. The second lens L2 is a meniscus negative focal power lens, and the third lens L3 is a biconcave negative focal power aspheric lens.

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

[0059] The zoom group provided by the embodiments of the present application contains at least three movable lens groups. By moving the at least three lens groups, a picture 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] The optical distortion distortion of the entire optical system during the movement of the fourth lens group G4, the fifth lens group G5 and the sixth lens group G6 satisfies the following relationship:

[0065] -2% < distortion < 2%.

[0066] In a specific implementation, the fourth lens group G4 can include a sixth lens L6 and a seventh lens L7. The sixth lens L6 is a biconcave negative focal power lens, and the seventh lens L7 is a biconvex positive focal power lens.

[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 double-convex positive refractive power and the ninth lens L9 with double-concave negative refractive power form a cemented lens, and the tenth lens L10 is a meniscus positive refractive 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 double-concave negative refractive power aspheric lens, the twelfth lens L12 is a meniscus positive refractive power aspheric lens, the thirteenth lens L13 with flat-concave negative refractive power, the fourteenth lens L14 with double-convex positive refractive power and the fifteenth lens L15 with meniscus negative refractive power form three cemented lenses, the sixteenth lens L16 with double-convex positive refractive power, the seventeenth lens L17 with double-concave negative refractive power and the eighteenth lens L18 with meniscus positive refractive power form three cemented lenses, and the nineteenth lens L19 is a double-convex positive refractive power aspheric lens.

[0069] Further, a diaphragm is arranged on the plane of the thirteenth lens L13. The zoom group includes at least three movable lens groups, and the diaphragm is arranged in one of the lens groups (the sixth lens group G6). The sixth lens group G6 includes at least two aspheric lenses, one of which is arranged between the diaphragm and the front fixed group and functions to eliminate spherical aberration, and the other of which is arranged between the diaphragm and the rear fixed group and functions to eliminate field curvature aberration.

[0070] In another implementation, the zoom group includes at least three movable lens groups, and the diaphragm is arranged in one of the lens groups. The lens group includes at least two cemented lenses, and the cemented lenses include high-refractive-index low-dispersion glass and function to eliminate chromatic aberration.

[0071] The rear fixed group is fixed relative to the object side and has positive refractive power. In a specific implementation, the seventh lens group G7 includes a twentieth lens L20, and the twentieth lens L20 is a double-convex positive refractive power lens.

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

[0073] 0.05 < f3 / fw < 0.15

[0074] The back focal length 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 effect of the projection optical system provided by the embodiment of the present application is verified below by taking an implementation manner as an example.

[0077] The front fixed group, the focusing group, the zooming group and the rear fixed group are sequentially arranged from the object side to the image side. The front fixed group contains the first lens group G1. The focusing group contains the second lens group G2 and the third lens group G3, and the two lens groups are movable. The zooming 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 the 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 the second lens L2 and the third lens L3, wherein the second lens L2 is a meniscus type negative power lens, and the third lens L3 is a double-concave type negative power aspherical lens.

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

[0081] The fourth lens group G4 includes the sixth lens L6 and the seventh lens L7, wherein the sixth lens L6 is a double-concave type negative power lens, and the seventh lens L7 is a double-convex type positive power lens.

[0082] The fifth lens group G5 includes the eighth lens L8 to the tenth lens L10, wherein the eighth lens L8 with double-convex type positive power and the ninth lens L9 with double-concave type negative power form a cemented lens, and the tenth lens L10 is a meniscus type positive power lens.

[0083] The sixth lens group G6 includes the eleventh lens L11 to the nineteenth lens L19, wherein the eleventh lens L11 is a double-concave type negative power aspherical lens, the twelfth lens L12 is a meniscus type positive power aspherical lens, the thirteenth lens L13 with flat-concave type negative power, the fourteenth lens L14 with double-convex type positive power and the fifteenth lens L15 with meniscus type negative power form a three-cemented lens, the sixteenth lens L16 with double-convex type positive power, the seventeenth lens L17 with double-concave type negative power and the eighteenth lens L18 with meniscus type positive power form a three-cemented lens, and the nineteenth lens L19 is a double-convex type positive power aspherical lens. The diaphragm is arranged on the plane side of the third lens.

[0084] The seventh lens group G7 includes the twentieth lens L20 which is a double-convex type positive power lens.

[0085] As shown in FIG. 1, by moving the three lens groups of the zoom group, a continuous zoom system of 1.1 times can be obtained, the minimum focal length is 5.2 mm (at this time the corresponding maximum field angle is 122°), and the maximum focal length is 5.8 mm (at this time the corresponding maximum field angle is 116°). The optical data is shown in Table 1. Figure 2 、 Figure 3 As shown in FIG. 1, by moving the three lens groups of the zoom group, a continuous zoom system of 1.1 times can be obtained, the minimum focal length is 5.2 mm (at this time the corresponding maximum field angle is 122°), and the maximum focal length is 5.8 mm (at this time the corresponding maximum field angle is 116°). The optical data is 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 gap, nd represents the refractive index of the glass, and vd represents the Abbe number of the glass. The data of air gaps D0 to D3 is shown in Table 2.

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

[0091]

[0092]

[0093] Table 2 shows the change of air gap between the zoom groups at different focal lengths, and a zoom of 1.1 times is achieved.

[0094] The aspheric surfaces described in Table 1 are all even aspheric surfaces, and the expression is as follows:

[0095]

[0096] Wherein, z is the sag of the aspheric surface along the optical axis at a height of r, c represents the vertex curvature of the surface, k is the conic coefficient of the aspheric surface, and a2, a3, a4, a5, a6, a7, and a8 are high-order non-curvature coefficients. The conic coefficient statistics are shown in Table 3.

[0097] Table 3

[0098] Surface No. 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 in the present application can obtain a clear picture at different projection distances by moving the movable lens group in the focusing group. By moving the movable lens group in the zoom group, different sizes of pictures can be obtained without changing the projection distance. Through the cooperation of each lens group, a large picture can be projected in a short distance, and the imaging quality is high while realizing continuous zoom ratio, and can support 4K resolution.

[0100] It is to be noted that, as used in this specification and the appended claims, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a component" can include a combination of two or more components, and the term "an element" can include comparable reference to a plurality of elements. Also, as used in this specification and the appended claims, the term "or" as used in the context of "A / B or C" means any literary or instrumental combination of the elements A / B and C. The terms "comprise," "comprising," "include," "including," and the like, as used herein, specifically include and do not exclude any steps of the processes, methods, articles, or apparatuses described herein, unless otherwise indicated.

[0101] The preferred embodiments of the present application have been described above with the intent to enable those skilled in the art to make and use it. Various modifications to these embodiments will occur to those skilled in the art and are intended to be encompassed by the description. Therefore, it is to be understood that within the scope of the appended claims, the application can be practiced otherwise than as specifically described. For that reason, the above description is intended for illustration only and not for limitation.

Claims

1. A projection optical system characterized by comprising, in order from an object side to an image side, The projection optical system comprises a front fixed group, a focusing group, a zooming group and a rear fixed group in sequence from the object side to the image side along the optical axis direction; the number of lens pieces with optical power in the projection optical system is 20; The front fixed group comprises a first lens group, the first lens group comprises at least one meniscus aspheric lens piece, the meniscus aspheric lens piece has negative optical power, and the meniscus aspheric lens piece is used for eliminating distortion aberration and reducing the aperture of the front end of the optical system; The focusing group comprises at least a second lens group and a third lens group which can move along the optical axis direction, the second lens group and the third lens group are moved so as to obtain a clear picture at different projection distances; the second lens group comprises a second lens and a third lens, the second lens is a meniscus negative optical power lens piece, and the third lens is a double-concave negative optical power aspheric lens piece; The third lens group comprises a fourth lens with double-convex positive optical power and a fifth lens with meniscus negative optical power, and the fourth lens and the fifth lens form a cemented lens piece; The zooming group comprises at least a fourth lens group, a fifth lens group and a sixth lens group which can move along the optical axis direction, the fourth lens group, the fifth lens group and the sixth lens group are moved so as to obtain pictures of different sizes without changing the projection distance; the fourth lens group comprises a sixth lens and a seventh lens, the sixth lens is a double-concave negative optical power lens piece, and the seventh lens is a double-convex positive optical power lens piece; The fifth lens group comprises an eighth lens, a ninth lens and a tenth lens; the eighth lens with double-convex positive optical power and the ninth lens with double-concave negative optical power form a cemented lens piece, and the tenth lens is a meniscus positive optical power lens piece; The sixth lens group comprises 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 double-concave negative optical power aspheric lens piece, the twelfth lens is a meniscus positive optical power aspheric lens piece, the thirteenth lens with flat-concave negative optical power, the fourteenth lens with double-convex positive optical power and the fifteenth lens with meniscus negative optical power form a three-cemented lens piece, the sixteenth lens with double-convex positive optical power, the seventeenth lens with double-concave negative optical power and the eighteenth lens with meniscus positive optical power form a three-cemented lens piece, and the nineteenth lens is a double-convex positive optical power aspheric lens piece; The rear fixed group comprises a seventh lens group, the seventh lens group has positive optical power; the seventh lens group comprises a twentieth lens; the twentieth lens is a double-convex positive optical power lens piece.

2. The projection optical system according to claim 1, characterized by The Abbe number of the meniscus aspheric lens piece is between 40 and 60, the maximum aperture D of the front fixed group and the total length L of the whole optical system satisfy the following relationship: 0.3 < D / L < 0.

4.

3. The projection optical system according to claim 1, characterized by The focal length f1 of the front fixed group and the minimum focal length fw obtained by moving the second lens group and the third lens group of the zooming group satisfy the following relationship: -0.15 < f1 / fw < -0.

05.

4. The projection optical system according to claim 1, characterized by The focal length f1 of the front fixed group and the focal length f2 of the focus group satisfy the following relationship: 0.4 < f1 / f2 < 0.

6.

5. The projection optical system according to claim 1, characterized by 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 whole optical projection system satisfy the following relationship: 0.015 < fw / L < 0.025 The maximum field angle FOV obtained by moving the fourth lens group, the fifth lens group and the sixth lens group satisfy the following relationship: 110° < FOV < 130° The optical distortion distortion of the whole optical system during moving the fourth lens group, the fifth lens group and the sixth lens group satisfies the following relationship: -2% < distortion < 2%.

6. The projection optical system according to claim 1, characterized by The plane of the thirteenth lens is provided with a diaphragm.

7. The projection optical system according to claim 1, characterized by 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: 0.05 < f3 / fw < 0.15 The back focal length BFL of the optical system and the total length L of the whole optical projection system satisfy the following relationship: 0.1 < BFL / L < 0.2.

Images