CN114690369A

CN114690369A - Projection lens

Info

Publication number: CN114690369A
Application number: CN202011566643.4A
Authority: CN
Inventors: 陈怡学; 葛睿; 尹蕾
Original assignee: Chengdu Jimi Technology Co Ltd
Current assignee: Chengdu Jimi Technology Co Ltd
Priority date: 2020-12-25
Filing date: 2020-12-25
Publication date: 2022-07-01
Anticipated expiration: 2040-12-25
Also published as: CN114690369B

Abstract

The invention discloses a projection lens, which comprises a fourth lens group, a third lens group, a diaphragm, a second lens group and a first lens group which are sequentially arranged along the projection light-emitting direction, wherein the diopter of the first lens group is negative to disperse light beams, the diopter of the second lens group is positive to adjust the aperture of the light beams, the diopter of the third lens group is negative and corrects spherical aberration, chromatic aberration and sinusoidal aberration, and the diopter of the fourth lens group is positive. The projection lens disclosed by the invention adopts the combination of the lens groups with negative, positive and negative diopters, can effectively disperse light beams to ensure the projection size, adjusts the aperture of the light beams to converge light, corrects spherical aberration, chromatic aberration and sine aberration, reduces distortion, improves the imaging quality, reduces the usage amount of the lenses, improves the structural compactness, reduces the occupied volume, is easy to assemble and has low cost.

Description

Projection lens

Technical Field

The invention relates to the technical field of projection devices, in particular to a projection lens.

Background

In recent years, projection display technology has been rapidly developed, and a projection apparatus can project a large-size image screen with a small apparatus volume. The projection lens is the key to influence the quality of projection pictures, the existing projection device tends to be miniaturized and developed, and the occupied volume of the projection lens is required to be smaller, so that the f-number of the projection lens is increased, and the light flux of a projection optical system is reduced. The existing shadow lens has the defects of more lenses, larger imaging distortion, not compact enough structure, complex assembly, high production difficulty and high cost.

Disclosure of Invention

The invention aims to solve the technical problems and the technical task of improving the prior art, and provides a projection lens, which solves the problems of large number of projection lens lenses, compact structure and large imaging distortion of a projection device in the prior art.

In order to solve the technical problems, the technical scheme of the invention is as follows:

a projection lens comprises a fourth lens group, a third lens group, a diaphragm, a second lens group and a first lens group which are sequentially arranged along the projection light-emitting direction, wherein the diopter of the first lens group is negative to disperse light beams, the diopter of the second lens group is positive to adjust the aperture of the light beams, the diopter of the third lens group is negative to correct spherical aberration, chromatic aberration and sinusoidal aberration, and the diopter of the fourth lens group is positive. The projection lens of the invention adopts a plurality of lens groups to combine, the first lens group effectively disperses light beams to ensure that a large-size image picture is projected, the second lens group adjusts the aperture of the light beams and effectively converges the light beams, can compensate with the distortion and spherical aberration generated by the first lens group, ensures the imaging quality, reduces the aperture of the diaphragm opening, can effectively reduce the whole occupied volume of the projection lens, improves the structure compactness, and the third lens group positioned on the light inlet side of the diaphragm is used for further correcting spherical aberration, chromatic aberration and sinusoidal aberration, so that the imaging quality is improved, the diopter of the fourth lens group is positive, the aperture of a light beam can be effectively restricted, the projection lens can be ensured to have a longer rear working distance, enough space is provided for placing optical elements such as a galvanometer, a prism digital micromirror device and the like, the assembly and the production are convenient, the structure compactness is improved, and the projection quality is ensured.

Further, first lens group is including the lens two of the negative diopter and the lens one of the negative diopter that set gradually along throwing the light-emitting direction, lens one be resin aspheric lens, be favorable to improving the angle of vision of system, rectify off-axis aberration, aspheric lens can reduce spherical lens's use quantity, great reduction projection lens system's complexity, reduce cost improves compact structure nature, and the light side of advancing of lens one is the even aspheric surface with the light-emitting side, through rationally optimizing aspheric surface coefficient, rectifies off-axis aberration effectively.

Furthermore, the second lens is a biconcave lens, the curvature radius of the light inlet side of the second lens is the same as that of the light outlet side of the second lens, so that the manufacturing is convenient, the cost is reduced, the second lens and the first lens are matched to effectively disperse light beams on the premise of not using a plurality of common spherical lenses, the subsequent lens group can conveniently eliminate aberration and collimate the light beams, the number of the lenses is reduced, the structure compactness is improved, and the cost of the projection lens is reduced.

Further, the second lens group include the lens of positive diopter four and the lens of positive diopter three that set gradually along throwing the light-emitting direction, lens four and lens three be biconvex lens, through the camber and the interval of reasonable optimization the two, can restraint a light beam bore more accurately, furthest makes light pass through the diaphragm completely, reduces light energy loss, improves projection quality.

Furthermore, the third lens group comprises a lens six with positive diopter and a lens five with negative diopter which are sequentially arranged along the projection light-emitting direction, the lens six and the lens five are combined to form a double cemented lens, the structure is compact, the total length of the projection lens is reduced, and the whole occupied space of the projection lens is reduced.

Furthermore, the refractive index of the fifth lens is higher than that of the sixth lens, the refractive index of the fifth lens is larger than or equal to 1.75, the refractive index of the sixth lens is smaller than or equal to 1.55, spherical aberration, chromatic aberration and sine aberration can be corrected simultaneously, and the projection quality is improved.

Furthermore, the fifth lens is a biconcave lens, the sixth lens is a biconvex lens, and the curvature radius of the six light inlet sides of the lenses is the same as that of the light outlet sides of the lenses, so that the lenses are convenient to manufacture, the cost is reduced, and the production and assembly processes are simplified.

Further, fourth lens group including along projecting the lens eight and the lens seven of positive diopter of the positive diopter that the light-emitting direction set gradually, can restrain beam aperture effectively, guarantee longer back working distance, be convenient for place optical element such as galvanometer, prism digital micromirror device to the guarantee can conveniently be assembled, lens eight and lens seven be biconvex lens, the curvature radius of lens seven advance the light side the same rather than the curvature radius of light-emitting side, be convenient for make reduce cost.

The digital micromirror device, the prism and the vibrating mirror are sequentially arranged on the light inlet side of the fourth lens group along the projection light outlet direction, the digital micromirror device is placed in a biased mode relative to the optical axis, the upward bias of an emergent image during projection work is guaranteed, the emergent light beam is higher than the position of the projection lens, and the projection image cannot be shielded by the projection lens.

Further, the effective focal length of the projection lens is 6mm or more and EFL or less than 7mm, the ratio of the lens back focal length of the projection lens to the effective focal length is BFL/EFL or more and 2.8 or less, the f-number of the projection lens is Fno or less than 1.7, the total length of the projection lens is TTL or less and 60mm, the field angle FOV of the projection lens is 63 degrees or more, and the light transmission aperture of each lens in the fourth lens group, the third lens group, the second lens group and the first lens group is less than 18 mm. The aperture diameter is bigger, that is to say, the aperture of passing light is bigger, and the number of light rays that can receive is more, improves luminance when guaranteeing small volume, improvement compact structure nature to effectively improve projection quality.

Compared with the prior art, the invention has the advantages that:

the projection lens disclosed by the invention adopts the combination of the lens groups with negative, positive and negative diopters, can effectively disperse light beams to ensure the projection size, adjusts the aperture of the light beams to converge light, corrects spherical aberration, chromatic aberration and sine aberration, reduces distortion, improves the imaging quality, reduces the usage amount of the lenses, improves the structural compactness, reduces the occupied volume, is easy to assemble and has low cost.

Drawings

Fig. 1 is a schematic diagram of an overall structure of a projection lens.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The projection lens disclosed by the embodiment of the invention can effectively inhibit the distortion, improve the chromatic aberration of a projection system, has a compact structure, small occupied space, low cost and large aperture, and can ensure a high-performance MTF value.

As shown in fig. 1, a projection lens mainly includes a fourth lens group G4, a third lens group G3, a diaphragm 10, a second lens group G2 and a first lens group G1, which are sequentially arranged along a projection light-emitting direction, wherein diopter of the first lens group G1 is negative to adjust a divergent light beam, diopter of the second lens group G2 is positive to adjust a light beam aperture, diopter of the third lens group G3 is negative to correct spherical aberration, chromatic aberration and sinusoidal difference, diopter of the fourth lens group G4 is positive, and diopter of the projection light-emitting direction is positive, negative, positive and negative, thereby forming a large-aperture high-performance fixed-focus projection lens, and effectively improving aberration-eliminating capability of the fixed-focus projection lens, and having low distortion, large-aperture, low cost and compact structure. The occupied space is small.

Specifically, the first lens group G1 includes a second lens L2 with a negative diopter and a first lens L1 with a negative diopter that are sequentially arranged along the projection light-emitting direction, the second lens group G2 includes a fourth lens L4 with a positive diopter and a third lens L3 with a positive diopter that are sequentially arranged along the projection light-emitting direction, the third lens group G3 includes a sixth lens L6 with a positive diopter and a fifth lens L5 with a negative diopter that are sequentially arranged along the projection light-emitting direction, and the fourth lens group G4 includes an eighth lens L8 with a positive diopter and a seventh lens L7 with a positive diopter that are sequentially arranged along the projection light-emitting direction;

the first lens L1 is a resin aspheric lens, both the light-in side and the light-out side of the first lens L1 are even aspheric surfaces, and the polynomial formula of the first lens L1 is as follows:

the second lens L2 is a biconcave lens, the curvature radius of the light inlet side of the second lens L2 is the same as that of the light outlet side of the second lens, the cost is greatly reduced, the production and assembly processes are simplified, the first lens L1 and the second lens L2 are matched, light beams can be effectively diverged on the premise that a plurality of common spherical lenses are not used, and the aberration elimination and collimation of the light beams can be conveniently carried out by the rest lens groups. Specifically, the curvature radius of the surface of the light inlet side of the first lens L1 is-50 mm to 20mm, the curvature radius of the surface of the light outlet side of the first lens L1 is 10mm to 60mm, the curvature radius of the light inlet side surface of the second lens L2 is-50 mm to 0mm, and the curvature radius of the light outlet side surface of the second lens L2 is 0mm to 50 mm;

the four lens L4 and the three lens L3 are both biconvex lenses, the aperture of the light beam can be accurately restricted by reasonably optimizing the curvatures and the intervals of the four lens L4 and the three lens L3, the light can completely pass through the diaphragm to the greatest extent, the light energy loss is reduced, and the projection quality is improved. Specifically, the curvature radius of the light-in side surface of the third lens L3 is 0 mm-50 mm, the curvature radius of the light-out side surface of the third lens L3 is-70 mm-20 mm, the curvature radius of the light-in side surface of the fourth lens L4 is 0 mm-50 mm, and the curvature radius of the light-out side surface of the fourth lens L4 is-100 mm-50 mm;

the six L6 and five L5 lenses form a double cemented lens, the focal length is negative f56, the refractive index of the five L5 lens is higher than that of the six L6 lens, specifically, the refractive index range of the five L5 lens is 1.75-1.95, the refractive index range of the six L6 lens is 1.35-1.55, the refractive index difference of the two lenses is large, achromatic design can be carried out, small chromatic aberration of the whole optical system is guaranteed, and spherical aberration and sine aberration can be corrected simultaneously; the five-L5 lens is a biconcave lens, the six-L6 lens is a biconvex lens, the curvature radius of the light inlet side of the six-L6 lens is the same as that of the light outlet side of the six-L6 lens, the curvature radius of the light inlet side surface of the five-L5 lens is-50 mm-0 mm, the curvature radius of the light outlet side surface of the five-L5 lens is 0 mm-50 mm, the curvature radius of the light inlet side surface of the six-L6 lens is 0 mm-50 mm, and the curvature radii of the six-L6 lens and the light outlet side surface are-50 mm-0 mm.

The eight L8 and seven L7 lenses are both biconvex lenses, and the curvature radius of the light inlet side of the seven L7 lenses is the same as that of the light outlet side thereof. Specifically, the curvature radius of the light-in side surface of the seven L7 lens is 0 mm-50 mm, the curvature radius of the light-out side surface of the seven L7 lens is-50 mm-0 mm, the curvature radius of the light-in side surface of the eight L8 lens is 0 mm-50 mm, and the curvature radius of the light-out side surface of the eight L8 lens is-200 mm-100 mm, so that the aperture of a light beam is effectively restricted, a long rear working distance is ensured, optical elements such as a galvanometer, a prism digital micromirror device and the like are conveniently placed, and the convenient assembly is guaranteed.

In addition, in order to improve the projection quality, the aspheric surface of the first lens L1 is used to correct distortion, astigmatism, coma aberration and spherical aberration, the light-exit side surface of the second lens L2 generates positive distortion, and the light-entrance side surface of the second lens L2 generates negative spherical aberration; the light-emitting side surface of the third lens L3 can generate positive spherical aberration to correct negative spherical aberration of the light-in side of the second lens L2, the light-in side surface of the fourth lens L4 can generate negative distortion to compensate positive distortion of the light-out side of the second lens L2, the fourth lens L4 is arranged close to the diaphragm 10, light can be effectively converged, the aperture of the diaphragm opening is reduced, the whole volume of the projection lens can be effectively reduced, a small amount of positive distortion exists on the light-out side surface of the seventh lens L7, the negative distortion of the light-in side surface of the fourth lens L4 can be balanced and compensated, distortion is reduced on the whole, and projection quality is improved.

The projection lens further comprises a digital micro-mirror device 40, a prism 30 and a vibrating mirror 20 which are sequentially arranged on the light inlet side of the fourth lens group G4 along the projection light outlet direction, the digital micro-mirror device is placed in a biased mode relative to the optical axis, the upward bias of an outgoing image in the projection working process is guaranteed, the outgoing light beam is higher than the position of the projection lens, the projection image cannot be shielded by the projection lens, and the vibrating mirror enables the projection lens to simultaneously obtain the inherent resolution of the DMD size when the vibrating mirror is static and the high resolution of the vibrating mirror during working shaking.

Overall, the effective focal length of the projection lens is 6mm or more and EFL or less than 7mm, the ratio of the lens back focal length of the projection lens to the effective focal length is BFL/EFL or more and more than 2.8, the f-number of the projection lens is Fno or less and 1.7, the total length of the projection lens is TTL or less and 60mm, the field angle FOV of the projection lens is or more than 63 °, and the light transmission apertures of the first lens L1 to the eighth lens L8 are respectively less than 18 mm. The projection lens is large in aperture diameter of the aperture, so that more light rays pass through the projection lens, the projection brightness can be effectively improved under the conditions of compact structure and small size, and the projection lens is precise in overall structure, convenient to assemble and low in implementation cost. The digital micro-mirror device with the size of 0.23 inch can project a picture of 2125mm (80 inches) at the position of 1500mm, the lens has the MTF value of each field of view of more than 53 percent at the position of a spatial limit frequency of 93lp/mm, the distortion is less than 0.71 percent, and the imaging quality is good.

The above is only a preferred embodiment of the present invention, and it should be noted that the above preferred embodiment should not be considered as limiting the present invention, and the protection scope of the present invention should be subject to the scope defined by the claims. It will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the spirit and scope of the invention, and these modifications and adaptations should be considered within the scope of the invention.

Claims

1. The utility model provides a projection lens, its characterized in that includes fourth lens group (G4), third lens group (G3), diaphragm (10), second lens group (G2) and first lens group (G1) that set gradually along the projection light-emitting direction, diopter of first lens group (G1) for the burden with divergent light beam, diopter of second lens group (G2) for positive with adjustment beam diameter, diopter of third lens group (G3) is for the burden and corrects spherical aberration, colour difference and sinusoidal difference, diopter of fourth lens group (G4) is positive.

2. The projection lens of claim 1, wherein the first lens group (G1) comprises a second lens element (L2) with negative diopter and a first lens element (L1) with negative diopter, which are sequentially arranged along the projection light-emitting direction, the first lens element (L1) is a resin aspheric lens, and both the light-entering side and the light-emitting side of the first lens element (L1) are even aspheric surfaces.

3. The projection lens of claim 2, wherein the second lens (L2) is a biconcave lens, and the radius of curvature of the light inlet side of the second lens (L2) is the same as that of the light outlet side of the second lens.

4. The projection lens as claimed in claim 1, wherein the second lens group (G2) comprises a positive diopter lens four (L4) and a positive diopter lens three (L3) sequentially arranged along the projection light-emitting direction, and both the lens four (L4) and the lens three (L3) are biconvex lenses.

5. The projection lens of claim 1, wherein the third lens group (G3) comprises a sixth lens (L6) with positive diopter and a fifth lens (L5) with negative diopter sequentially arranged along the projection light-emitting direction, and the sixth lens (L6) and the fifth lens (L5) are combined to form a double cemented lens.

6. The projection lens of claim 5, wherein the refractive index of lens five (L5) is higher than the refractive index of lens six (L6), the refractive index of lens five (L5) is greater than or equal to 1.75, and the refractive index of lens six (L6) is less than or equal to 1.55.

7. The projection lens of claim 5 wherein lens five (L5) is a biconcave lens and lens six (L6) is a biconvex lens, the radius of curvature of the light-in side of lens six (L6) being the same as the radius of curvature of the light-out side thereof.

8. The projection lens as claimed in claim 1, wherein the fourth lens group (G4) comprises a positive refractive power lens eight (L8) and a positive refractive power lens seven (L7) sequentially arranged along the projection light-emitting direction, the lens eight (L8) and the lens seven (L7) are both biconvex lenses, and the radius of curvature of the light-entering side of the lens seven (L7) is the same as that of the light-emitting side thereof.

9. A projection lens as claimed in claim 1, characterized by further comprising a dmd (40), a prism (30) and a galvanometer (20) arranged in sequence along the light-projecting direction on the light-entering side of the fourth lens group (G4), wherein the dmd is disposed offset with respect to the optical axis.

10. The projection lens of any one of claims 1 to 9 wherein the effective focal length of the projection lens is 6mm ≤ EFL ≤ 7mm, the ratio of the back focal length of the projection lens to the effective focal length is BFL/EFL ≥ 2.8, the f-number of the projection lens is Fno ≤ 1.7, the total length of the projection lens is TTL ≤ 60mm, the field angle FOV of the projection lens is ≥ 63 °, and the clear aperture of each of the fourth (G4), third (G3), second (G2) and first (G1) lens groups is less than 18 mm.