CN114690369B

CN114690369B - Projection lens

Info

Publication number: CN114690369B
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: 2023-10-13
Anticipated expiration: 2040-12-25
Also published as: CN114690369A

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 diverge light beams, the diopter of the second lens group is positive to adjust the caliber of the light beams, the diopter of the third lens group is negative and corrects spherical aberration, chromatic aberration and sine difference, and the diopter of the fourth lens group is positive. The projection lens provided by the invention combines the lens groups with negative diopter, positive diopter and negative diopter, can effectively diverge light beams to ensure projection size, adjusts the aperture of the light beams to converge light rays, corrects spherical aberration, chromatic aberration and sine difference, reduces distortion, improves imaging quality, reduces the use amount of the lenses, improves structural compactness, reduces occupied volume, and is easy to assemble and low in cost.

Description

Projection lens

Technical Field

The present disclosure relates to projection devices, and particularly to a projection lens.

Background

In recent years, projection display technology has been rapidly developed, and a projection apparatus can project a large-sized image with a small apparatus volume. The projection lens is the key for influencing the quality of a projection picture, the current projection device tends to be miniaturized, the occupied volume of the projection lens is required to be smaller, the aperture number of the projection lens is increased, and the light quantity of a projection optical system is reduced. The existing shadow lens has the defects of more lenses, larger imaging distortion, insufficient compactness, 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, providing a projection lens and solving the problems of a projection device in the prior art that the number of lenses of the projection lens is large, the structure is compact and the imaging distortion is large.

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

the utility model provides a projection lens, includes fourth lens group, third lens group, diaphragm, second lens group and the first lens group that set gradually along the direction of projection light, the diopter of first lens group be negative with the light beam that diverges, the diopter of second lens group be positive with the adjustment light beam bore, the diopter of third lens group be negative and correct spherical aberration, colour difference and sinusoidal difference, the diopter of fourth lens group is positive. The projection lens disclosed by the invention is combined by adopting a plurality of lens groups, the first lens group effectively diverges light beams to ensure that large-size image pictures are projected, the second lens group adjusts the aperture of the light beams and effectively converges light rays, the light beams can be compensated with distortion and spherical aberration generated by the first lens group, the imaging quality is ensured, the aperture of an aperture of a diaphragm is reduced, the whole occupied volume of the projection lens can be effectively reduced, the structural compactness is improved, the spherical aberration, chromatic aberration and sinusoidal difference are further corrected by utilizing the third lens group positioned on the light inlet side of the diaphragm, the imaging quality is improved, the diopter of the fourth lens group is positive to effectively restrict the aperture of the light beams, the projection lens can be ensured to have a longer back working distance, enough space is provided for placing optical elements such as a galvanometer and a prism digital micro-mirror device, the assembly production is facilitated, the structural compactness is improved, and the projection quality is ensured.

Further, the first lens group comprises a second lens with negative diopter and a first lens with negative diopter, which are sequentially arranged along the projection light emitting direction, wherein the first lens is a resin aspheric lens, which is favorable for improving the view angle of the system, correcting off-axis aberration, reducing the use quantity of the spherical lens, greatly reducing the complexity of the projection lens system, reducing the cost and improving the structural compactness, and the light inlet side and the light outlet side of the first lens are both even aspheric surfaces, and the off-axis aberration is effectively corrected by reasonably optimizing the aspheric coefficients.

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 can effectively diverge light beams on the premise that a plurality of common spherical lenses are not used, the subsequent lens groups can conveniently perform aberration elimination and collimation on the light beams, the number of lenses is reduced, the structural compactness is improved, and the cost of a projection lens is reduced.

Further, the second lens group comprises a lens IV with positive diopter and a lens III with positive diopter which are sequentially arranged along the projection light emitting direction, the lens IV and the lens III are biconvex lenses, the aperture of the light beam can be more accurately restrained by reasonably optimizing the curvature and the interval of the lens IV and the lens III, the light can completely pass through the diaphragm to the maximum extent, the light energy loss is reduced, and the projection quality is improved.

Further, 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.

Further, the refractive index of the lens five is higher than that of the lens six, the refractive index of the lens five is more than or equal to 1.75, and the refractive index of the lens six is less than or equal to 1.55, so that spherical aberration, chromatic aberration and sinusoidal difference can be corrected simultaneously, and projection quality is improved.

Further, the lens five is a biconcave lens, the lens six is a biconvex lens, the curvature radius of the six light inlet side of the lens is the same as the curvature radius of the light outlet side of the lens, the manufacturing is convenient, the cost is reduced, and the production and assembly process is simplified.

Further, the fourth lens group includes eight lenses of positive diopter and seven lenses of positive diopter that set gradually along the direction of projection light-emitting, can retrain the light beam bore effectively, guarantee longer back working distance, be convenient for place optical elements such as galvanometer, prism digital micromirror device to ensure can assemble conveniently, eight lenses of lens and seven lenses be the lenticular lens, seven light-in side's radius of curvature be the same with its light-out side's radius of curvature, be convenient for make, reduce cost.

Further, the light-emitting device comprises a digital micro-mirror device, a prism and a vibrating mirror which are sequentially arranged on the light-in side of the fourth lens group along the light-emitting direction of projection, wherein the digital micro-mirror device is arranged in an offset mode relative to the optical axis, so that an outgoing picture is ensured to be offset upwards during projection operation, the outgoing light beam is higher than the position of a projection lens, and the projection picture cannot be shielded by the projection lens.

Further, the effective focal length of the projection lens is 6mm less than or equal to EFL less than or equal to 7mm, the ratio of the lens back focal length of the projection lens to the effective focal length is BFL/EFL less than or equal to 2.8, the f-number of the projection lens is FNo less than or equal to 1.7, the total length of the projection lens is TTL less than or equal to 60mm, the field angle FOV of the projection lens is greater than or equal to 63 degrees, and the light transmission caliber of each lens in the fourth lens group, the third lens group, the second lens group and the first lens group is less than 18mm. The aperture diameter is larger, namely the aperture of the transmitted light is larger, the number of received light rays is larger, the small size is ensured, the structural compactness is improved, and meanwhile, the brightness is improved, so that the projection quality is effectively improved.

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

the projection lens provided by the invention combines the lens groups with negative diopter, positive diopter and negative diopter, can effectively diverge light beams to ensure projection size, adjusts the aperture of the light beams to converge light rays, corrects spherical aberration, chromatic aberration and sine difference, reduces distortion, improves imaging quality, reduces the use amount of the lenses, improves structural compactness, reduces occupied volume, and is easy to assemble and low in cost.

Drawings

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

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

The projection lens disclosed by the embodiment of the invention effectively inhibits distortion, improves the chromatic aberration of a projection system, has a compact structure, small occupied space, low cost and large aperture diameter, 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 sequentially disposed along a projection light-emitting direction, wherein diopter of the first lens group G1 is negative to diverge light beams, diopter of the second lens group G2 is positive to adjust aperture of the light beams, diopter of the third lens group G3 is negative and corrects spherical aberration, chromatic aberration and sinusoidal difference, diopter of the fourth lens group G4 is positive, and diopter of the fourth lens group G4 is positive, negative, positive and negative along the projection light-emitting direction, so as to form a large-caliber high-performance fixed focus projection lens, effectively improving aberration-eliminating capability of the fixed focus projection lens, and having low distortion, large caliber aperture, low cost and compact structure. The occupied space is small.

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

the lens I L1 is a resin aspheric lens, the light inlet side and the light outlet side of the lens I L1 are both even aspheric surfaces, and the polynomial formula of the lens I L1 is as follows:

the off-axis aberration can be effectively corrected by reasonably optimizing the coefficients of the aspherical lenses, 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 L2, the cost is greatly reduced, the production assembly process is simplified, the first lens L1 and the second lens L2 are matched, the light beams can be effectively diverged on the premise that a plurality of common spherical lenses are not used, and the other lens groups are convenient for aberration elimination and collimation of the light beams. Specifically, the radius of curvature of the surface of the light incident side of the first lens L1 is-50 mm to 20mm, the radius of curvature of the surface of the light emergent side of the first lens L1 is 10mm to 60mm, the radius of curvature of the surface of the light incident side of the second lens L2 is-50 mm to 0mm, and the radius of curvature of the surface of the light emergent side of the second lens L2 is 0mm to 50mm;

the four lenses L4 and the three lenses L3 are biconvex lenses, and the aperture of the light beam can be more accurately restrained by reasonably optimizing the curvature and the interval of the four lenses L4 and the three lenses L3, so that the light rays can completely pass through the diaphragm to the maximum extent, the light energy loss is reduced, and the projection quality is improved. Specifically, the radius of curvature of the light-in side surface of the lens III L3 is 0 mm-50 mm, the radius of curvature of the light-out side surface of the lens III L3 is-70 mm-20 mm, the radius of curvature of the light-in side surface of the lens IV L4 is 0 mm-50 mm, and the radius of curvature of the light-out side surface of the lens IV L4 is-100 mm-50 mm;

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

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

In order to improve projection quality, the aspheric surface of the first lens L1 is used for correcting distortion, astigmatism, coma and spherical aberration, the light-emitting side surface of the second lens L2 generates positive distortion, and the light-entering side surface of the second lens L2 generates negative spherical aberration; the light-emitting side surface of the lens III L3 can generate positive spherical aberration, negative spherical aberration of the light-emitting side of the lens II L2 can be corrected, negative distortion can be generated on the light-emitting side surface of the lens IV L4, positive distortion of the light-emitting side of the lens II L2 can be compensated, the lens IV L4 is close to the diaphragm 10, light can be effectively converged, 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-emitting side surface of the lens IV L7, negative distortion of the light-emitting side surface of the lens IV 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 incident side of the fourth lens group G4 along the light emergent direction, wherein the digital micro-mirror device is arranged in an offset mode relative to the optical axis, the outgoing picture is ensured to be upwards offset when the projection work is performed, the outgoing light beam is higher than the position of the projection lens, the projection picture cannot be shielded by the projection lens, and the vibrating mirror enables the projection lens to simultaneously obtain the inherent resolution of the DMD when the vibrating mirror is static and the high resolution when the vibrating mirror shakes.

In the whole, the effective focal length of the projection lens is 6mm less than or equal to EFL less than or equal to 7mm, the ratio of the back focal length of the projection lens to the effective focal length of the projection lens is BFL/EFL less than or equal to 2.8, the f-number of the projection lens is FNo less than or equal to 1.7, the total length of the projection lens is TTL less than or equal to 60mm, the field angle FOV of the projection lens is more than or equal to 63 degrees, and the light transmission apertures of the first lens L1 to the eighth lens L8 are respectively smaller than 18mm. The aperture of the projection lens is large, so that more light passes through the aperture, projection brightness can be effectively improved under the conditions of compact structure and small volume, and the projection lens has the advantages of precise integral structure, convenience in assembly and low implementation cost. The digital micro-mirror device with 0.23 inch can project 2125mm (80 inch) pictures at 1500mm, and the lens has MTF value of each field of view larger than 53% at 93lp/mm of spatial limit frequency, distortion smaller than 0.71% and good imaging quality.

The foregoing is merely a preferred embodiment of the present invention, and it should be noted that the above-mentioned preferred embodiment should not be construed as limiting the invention, and the scope of the invention should be defined by the appended 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 such modifications and adaptations are intended to be comprehended 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 direction of projection light, the diopter of first lens group (G1) be negative with the light beam that diverges, the diopter of second lens group (G2) be positive with the adjustment light beam bore, the diopter of third lens group (G3) be negative and correct spherical aberration, colour difference and sinusoidal difference, the diopter of fourth lens group (G4) be positive, third lens group (G3) include six (L6) of positive diopter and five (L5) of negative diopter that set gradually along the direction of projection light, six (L6) of lens and five (L5) of lens combine to form two cemented lenses, fourth lens group (G4) include eight (L8) of positive diopter and seven (L7) of positive diopter that set gradually along the direction of projection light.

2. The projection lens according to claim 1, wherein the first lens group (G1) includes a second lens (L2) with negative refractive power and a first lens (L1) with negative refractive power, which are sequentially arranged along the projection light-emitting direction, the first lens (L1) is a resin aspheric lens, and the light-entering side and the light-emitting side of the first lens (L1) are both 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 entrance side of the second lens (L2) is the same as the radius of curvature of the light exit side thereof.

4. The projection lens according to claim 1, wherein the second lens group (G2) includes a fourth lens (L4) with positive refractive power and a third lens (L3) with positive refractive power, which are sequentially arranged along the projection light emitting direction, and the fourth lens (L4) and the third lens (L3) are lenticular lenses.

5. The projection lens according to claim 1, wherein the refractive index of the fifth lens (L5) is higher than the refractive index of the sixth lens (L6), the refractive index of the fifth lens (L5) is 1.75 or more, and the refractive index of the sixth lens (L6) is 1.55 or less.

6. The projection lens of claim 1, wherein the fifth lens (L5) is a biconcave lens, the sixth lens (L6) is a biconvex lens, and the radius of curvature of the light entrance side of the sixth lens (L6) is the same as the radius of curvature of the light exit side thereof.

7. The projection lens of claim 1, wherein the eight (L8) and seven (L7) lenses are biconvex lenses, and the seven (L7) lenses have the same radius of curvature on the light entrance side as on the light exit side.

8. The projection lens according to claim 1, further comprising a digital micromirror device (40), a prism (30) and a galvanometer (20) arranged in this order along the projection light-out direction on the light-in side of the fourth lens group (G4), said digital micromirror device being offset with respect to the optical axis.

9. The projection lens according to any one of claims 1 to 8, wherein the effective focal length of the projection lens is 6mm +.efl +.7mm, the ratio of the lens back focal length to the effective focal length of the projection lens 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 +.60 mm, the field angle FOV of the projection lens is +.63 °, and the aperture of each of the fourth lens group (G4), third lens group (G3), second lens group (G2) and first lens group (G1) is less than 18mm.