CN117849994A

CN117849994A - Projection lens and projection display device

Info

Publication number: CN117849994A
Application number: CN202410137891.9A
Authority: CN
Inventors: 王志煌; 李文宗
Original assignee: Shenzhen Shengyang Optical Technology Co ltd
Current assignee: Shenzhen Shengyang Optical Technology Co ltd
Priority date: 2023-12-12
Filing date: 2024-02-01
Publication date: 2024-04-09
Also published as: CN117389100A

Abstract

The invention discloses a projection lens and projection display equipment, and relates to the technical field of projection display. The projection lens has an optical axis, and the projection lens includes: the rear group lens group, the middle group lens group and the front group lens group are distributed along the transmission direction of the image light, the image light is incident to the front group lens group through the rear group lens group and the middle group lens group, and the front group lens group can reflect the image light to form a projection picture; wherein, projection lens satisfies: l1 is equal to or greater than L2; wherein L1 is a distance between a center position of a side of the middle group lens group, which is close to the front group lens group, and a side of the front group lens group, which is far from the middle group lens group, in the optical axis direction; l2 is a distance between a center position of a side of the middle group lens group away from the rear group lens group and the rear group lens group in the optical axis direction.

Description

Projection lens and projection display device

Technical Field

The present invention relates to the field of projection display technologies, and in particular, to a projection lens and a projection display device.

Background

In recent years, ultra-short focal projection technology is becoming a hotspot of the domestic projection display market. The ultra-short focal projection display device has small requirements on distance, and often only needs a projection distance of tens of centimeters to project a large picture. In the related art, a projection lens in the ultra-short focal technology generally performs short-distance projection in a reflective manner, resulting in a large volume of the projection lens.

Disclosure of Invention

The present invention aims to solve at least one of the technical problems in the related art to some extent. Therefore, the invention provides the projection lens and the projection display device, which can enable the volume of the projection lens to be smaller and realize the effect of smaller projection ratio.

In a first aspect, an embodiment of the present invention provides a projection lens, the projection lens having an optical axis; the projection lens includes: a rear group lens group, a middle group lens group and a front group lens group which are distributed along the transmission direction of image light, wherein the image light is incident to the front group lens group through the rear group lens group and the middle group lens group, and the front group lens group can reflect the image light to form a projection picture; wherein, the projection lens satisfies: l1 is equal to or greater than L2; wherein L1 is a distance between a center position of a side of the middle group lens group, which is close to the front group lens group, to a side of the front group lens group, which is far from the middle group lens group, in the optical axis direction; l2 is a distance between a center position of a side of the middle group lens group away from the rear group lens group and the rear group lens group along the optical axis direction.

According to the embodiment of the invention, the distance between the front group lens group and the middle group lens group and the distance between the middle group lens group and the rear group lens group are reasonably set, so that the volume of the projection lens can be effectively reduced under the condition of being beneficial to high imaging quality, and the effect of smaller projection ratio can be realized.

In some embodiments, the projection lens satisfies: L1/L2 is less than or equal to 1 and less than or equal to 5.0. Through the arrangement, the total length of the projection lens can be effectively shortened and the volume of the projection lens can be reduced under the condition of being beneficial to high imaging quality.

In some embodiments, the projection lens satisfies: l3 is less than L2; wherein L3 is an optical length of the rear group lens group along the optical axis direction. Through the arrangement, the total length of the projection lens can be effectively shortened and the volume of the projection lens can be reduced under the condition of being beneficial to high imaging quality.

In some embodiments, the projection lens satisfies: l3 is less than L1; wherein L3 is an optical length of the rear group lens group along the optical axis direction. Through the arrangement, the total length of the projection lens can be effectively shortened and the volume of the projection lens can be reduced under the condition of being beneficial to high imaging quality.

In some embodiments, a cemented lens is included in both the middle group lens group and the rear group lens group, and the number of lenses in the rear group lens group is the same as the number of lenses in the middle group lens group. Through set up the cemented lens respectively in well group lens group and back group lens group to combine the framework that lens quantity is equal in well group lens group and the back group lens group, not only can effectively correct the aberration problem, can also make the lens have less projection ratio, thereby realize little projection ratio, high performance's effect.

In some embodiments, the middle group lens group comprises a second lens, a third lens and a fourth lens in sequence along a direction away from the front group lens group; the third lens is glued with the fourth lens, the third lens is a negative focal power lens, and the fourth lens is a positive focal power lens. By reasonably setting the focal power, the surface shape and the like of each lens in the middle group lens group, the focal length and the aberration of the middle group lens group can be effectively reduced, and therefore the effects of small projection ratio and high performance are achieved.

In some embodiments, in a direction away from the front group of lenses, the middle group of lenses further comprises, in order: a fifth lens, a sixth lens, a seventh lens and an eighth lens; wherein the fifth lens is positioned at one side of the fourth lens, which is away from the front group lens group; the surface of the fifth lens facing the fourth lens is a convex surface, the surface of the sixth lens facing the fifth lens is a convex surface, the surface of the sixth lens facing away from the fifth lens is a concave surface, the surface of the seventh lens facing the sixth lens is a convex surface, and the surface of the eighth lens facing the seventh lens is a concave surface. By reasonably setting the focal power, the surface shape and the like of each lens in the middle group lens group, the focal length and the aberration of the middle group lens group can be effectively reduced, and therefore the effects of small projection ratio and high performance are achieved.

In some embodiments, the rear group lens group includes, in a direction away from the middle group lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, a thirteenth lens, and a fourteenth lens in that order; wherein the ninth lens is cemented with a tenth lens, the eleventh lens is cemented with a twelfth lens, and the thirteenth lens is cemented with a fourteenth lens. Through the arrangement, the effects of large aperture and low chromatic aberration can be achieved, and higher imaging quality is obtained.

In some embodiments, the ninth lens is a positive power lens and the tenth lens is a negative power lens; the eleventh lens is a negative focal power lens, and the twelfth lens is a positive focal power lens; the thirteenth lens is a positive power lens, and the fourteenth lens is a negative power lens.

In some embodiments, the projection lens further includes an aperture, the aperture being disposed in an optical path between the middle group lens group and the rear group lens group, and a center distance between a cemented lens of the middle group lens group, which is closer to the rear group lens group, and the aperture being greater than a center distance between a cemented lens of the rear group lens group, which is closer to the middle group lens group, and the aperture along an optical axis direction of the projection lens. Through the distance setting, and the combination of the setting of positive and negative focal power of the cemented lens, chromatic aberration can be effectively corrected, imaging quality is improved, aperture size of the lens is reduced, and volume and cost of the lens are reduced.

In some embodiments, a center distance between the aperture and a cemented lens in the middle group lens group is less than 4mm.

In some embodiments, the middle group lens group comprises a plurality of groups of double-cemented lens groups, and a single lens is arranged between every two adjacent groups of double-cemented lens groups. Through the arrangement, the effects of large aperture and low chromatic aberration can be realized.

In some embodiments, the middle group lens group comprises at least one group of cemented lens groups; and/or the rear group lens group comprises at least one group of three cemented lens groups. Through the arrangement, the aberration problems such as chromatic aberration, spherical aberration and the like can be effectively corrected, so that the imaging quality is improved.

In some embodiments, the front group lens group includes a first lens having a transmissive face toward the middle group lens group and a reflective face away from the middle group lens group; the projection lens satisfies the following conditions: 0.3880R 1/R2 is less than or equal to 0.5820; wherein R1 is the radius of curvature of the reflecting surface of the first lens; r2 is the radius of curvature of the transmission surface of the first lens.

In a second aspect, an embodiment of the present invention further provides a projection display apparatus, including: a projection lens as claimed in any preceding claim, and a spatial light modulator, projection light source; the projection light source is used for generating illumination light, the illumination light is modulated Cheng Yingxiang by the spatial light modulator, the image light is projected to the projection lens, and a projection picture is formed by the projection lens.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

FIG. 1 is a schematic view of a projection lens according to an exemplary embodiment;

FIG. 2 is a graph of a modulation transfer function provided by an exemplary embodiment;

FIG. 3 is a graph of distortion provided by an exemplary embodiment;

FIG. 4 is a longitudinal spherical aberration plot of a projection lens provided by an exemplary embodiment;

fig. 5 is an astigmatic curve diagram of a projection lens provided by an exemplary embodiment.

Reference numerals illustrate:

10-front group lens group; 11-a first lens; 20-middle group lens group; 21-a second lens; 22-a third lens; 23-fourth lens; 24-a fifth lens; 25-sixth lens; 26-seventh lens; 27-eighth lens; 30-a rear group lens group; 31-a ninth lens; 32-tenth lens; 33-eleventh lens; 34-a twelfth lens; 35-thirteenth lens; 36-fourteenth lens; 37-fifteenth lens; 40-plate glass group; 41-a first sheet glass; 42-a second flat glass; 43-third flat glass.

Detailed Description

Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.

The structure, function and implementation of the projection lens according to the embodiment of the present invention are described below by way of example with reference to the accompanying drawings.

In addition, other structures and functions of the projection lens according to the embodiments of the present invention are known to those skilled in the art, and are not described herein for redundancy reduction.

Fig. 1 is a schematic view of a projection lens according to an exemplary embodiment. The dotted line in the figure is used to illustrate the projected light.

Referring to fig. 1, the projection lens provided in the present embodiment has an optical axis, and the projection lens includes: the rear group lens group 30, the middle group lens group 20 and the front group lens group 10 are arranged along the transmission direction of the image light, the image light is incident to the front group lens group 10 through the rear group lens group 30 and the middle group lens group 20, and the front group lens group 10 can reflect the image light to form a projection picture.

The projection lens satisfies: l1 is equal to or greater than L2; wherein L1 is a distance between a center position of a side of the middle group lens group 20 close to the front group lens group 10 to a side of the front group lens group 10 far from the middle group lens group 20 in the optical axis direction; l2 is a distance between a center position of a side of the middle group lens group 20 away from the rear group lens group 30 and the rear group lens group 30 in the optical axis direction.

Generally, the surface of each lens closest to the imaging surface is referred to as the image side of the lens, and the surface of the lens that is intended to face away from the image side is the object side. The image light is transmitted from the image side to the object side of the lens.

Wherein the front group lens group 10 includes a first lens 11; for convenience of description, this embodiment will be described by taking this as an example. Illustratively, the first lens 11 has a transmissive surface facing the middle group lens group 20 and a reflective surface facing away from the middle group lens group 20; that is, the image side surface of the first lens element 11 is a transmissive surface, and the object side surface of the first lens element 11 has at least a partially reflective surface. The image light emitted from the group lens group 20 is incident into the first lens 11 from the transmission surface of the first lens 11, is refracted, is reflected by the reflection surface of the first lens 11 to the transmission surface of the first lens 11, and is projected from the transmission surface of the first lens 11 to form a projection screen. In other examples, the front group lens group 10 may also include a plurality of lenses, and may be specifically configured according to actual needs.

The radius of curvature R2 of the transmission surface of the first lens 11 and the radius of curvature R1 of the reflection surface of the first lens 11 satisfy: 0.3880.ltoreq.R1/R2.ltoreq. 0.5820, for example, R1/R2 may be 0.3880 or 0.45 or 0.4850 or 0.5 or 0.5820, or a ratio between any two of the above.

The group lens group 20 includes a plurality of lenses, and any two adjacent lenses in the plurality of lenses may have an air space therebetween or may be glued. Optionally, at least two lenses of the plurality of lenses of the middle group lens assembly 20 are cemented to correct chromatic aberration, spherical aberration, and other aberration problems. Wherein, each lens that is glued together can be called a cemented lens respectively, and the cemented lens group can be called a cemented lens group. When there are two cemented lenses in a cemented lens group, the cemented lens group may be referred to as a cemented doublet. When there are three cemented lenses in the cemented lens group, the cemented lens group may be referred to as a triple cemented lens group.

The rear group lens assembly 30 may also include a plurality of lenses, and any two adjacent lenses in the plurality of lenses may have an air space therebetween or may be cemented. Optionally, at least two lenses of the plurality of lenses of the rear group lens assembly 30 are cemented to correct chromatic aberration, spherical aberration, and other aberration problems.

Optionally, the front group lens group 10 has positive optical power; the middle group lens group 20 has negative optical power; the rear group lens group 30 has negative optical power. The imaging quality can be effectively improved by reasonably distributing the positive and negative focal power of each lens group of the projection lens. In addition, the front group lens group 10 has positive focal power, the middle group lens group 20 has negative focal power, and the rear group lens group 30 has negative focal power, so that spherical aberration and chromatic aberration generated by the lens groups can be effectively balanced, imaging quality is improved, definition of a projection picture is improved, the length of a projection lens can be reduced, and cost is reduced.

For convenience of description, a distance L1 between a side of the front group lens group 10 away from the middle group lens group 20 and a center of the middle group lens group 20 in the optical axis direction; the distance between the center of the rear group lens group 30 and the side of the middle group lens group 20 away from the rear group lens group 30 in the optical axis direction is L2. The center distance in this embodiment refers to a distance between center positions of two optical elements (or optical modules).

In other words, L1 is the distance between the point on the optical axis of the reflecting surface of the first lens 11 and the point on the optical axis of the object side surface of the lens in the middle group lens group 20, which is close to the front group lens group 10. L2 is the distance between the point on the optical axis of the object side surface of the lens in the middle group lens group 20, which is close to the front group lens group 10, and the point on the optical axis of the object side surface of the lens in the rear group lens group 30, which is close to the middle group lens group 20.

The projection lens satisfies one of the following: l1=l2; or L1 > L2. When L1 is greater than L2, the difference between L1 and L2 may be set according to actual needs.

In this embodiment, the distance between the front group lens group 10 and the middle group lens group 20 and the distance between the middle group lens group 20 and the rear group lens group 30 are reasonably set, so that the volume of the projection lens can be effectively reduced, and the effect of smaller projection ratio can be realized.

In some embodiments, the projection lens satisfies: L1/L2 is less than or equal to 1 and less than or equal to 5.0. Illustratively, L1/L2 may be 1 or 1.5 or 2 or 2.5 or 3 or 3.5 or 4 or 4.5 or 5, or a value between any two of the above. Through the arrangement, the total length of the projection lens can be effectively shortened and the volume of the projection lens can be reduced under the condition of being beneficial to high imaging quality.

In some embodiments, the projection lens satisfies: l3< L2. Wherein L2 is a center distance between a side of the middle group lens group 20 away from the rear group lens group 30 and the rear group lens group 30 along the optical axis direction; l3 is the optical length of the rear group lens group 30 along the optical axis direction.

The difference between L3 and L2, or the ratio between L3 and L2 may be set according to actual needs. Illustratively, 0.4.ltoreq.L3/L2 < 1. For example, L3/L2 may be 0.4 or 0.47 or 0.5 or 0.6 or 0.7 or 0.8 or 0.9 or 0.99, or a value between any two of the above. Through the arrangement, the total length of the projection lens can be effectively shortened and the volume of the projection lens can be reduced under the condition of being beneficial to high imaging quality.

In some embodiments, the projection lens satisfies: l3< L1; wherein L1 is a center distance between a side of the front group lens group 10 away from the middle group lens group 20 and the middle group lens group 20 along the optical axis direction; l3 is the optical length of the rear group lens group 30 along the optical axis direction.

The difference between L3 and L2, or the ratio between L3 and L2 may be set according to actual needs. Illustratively, 0.4.ltoreq.L3/L2 < 1. For example, L3/L2 may be 0.4 or 0.47 or 0.5 or 0.6 or 0.7 or 0.8 or 0.9 or 0.99, or a value between any two of the above. Through the arrangement, the total length of the projection lens can be effectively shortened and the volume of the projection lens can be reduced under the condition of being beneficial to high imaging quality. In some embodiments, the middle group lens group 20 and the rear group lens group 30 each include a cemented lens therein. The specific number of the cemented lenses can be set according to actual needs. With the arrangement, the present embodiment can effectively correct aberration problems such as chromatic aberration and spherical aberration through the cemented lens.

Alternatively, the number of cemented lenses in the rear group lens group 30 is greater than the number of cemented lenses in the middle group lens group 20. For example, the middle group lens group 20 may have a double cemented lens group, and the rear group lens group 30 may have two or three double cemented lens groups, so as to achieve the effects of large aperture and low chromatic aberration, and improve imaging quality.

In some examples, the number of lenses in the rear group lens group 30 is the same as the number of lenses in the middle group lens group 20, so that aberration problems of the projection lens, such as chromatic aberration, distortion, or coma, can be corrected. For example, 7 lenses may be included in the rear group lens group 30 and the middle group lens group 20, respectively.

In the present embodiment, by respectively arranging the cemented lenses in the middle group lens group 20 and the rear group lens group 30 and combining the architectures that the number of lenses in the middle group lens group 20 and the rear group lens group 30 is equal, not only can the aberration problem be effectively corrected, but also the lens has a smaller projection ratio, thereby realizing the effects of small projection ratio and high performance.

In some embodiments, the middle group lens group 20 includes a second lens 21, a third lens 22, and a fourth lens 23 in order along a direction away from the front group lens group 10, i.e., a direction from the object side to the image side. The third lens 22 is glued with the fourth lens 23, and the third lens 22 is a negative power lens, and the fourth lens 23 is a positive power lens.

The surface of the second lens 21 facing the front group lens assembly 10 (i.e., the object side surface) is concave. The object-side surface of the third lens element 22 can be concave, the image-side surface of the third lens element 22 can be concave, the object-side surface of the fourth lens element 23 can be convex, the image-side surface of the fourth lens element 23 can be convex, and the image-side surface of the third lens element 22 can be cemented with the object-side surface of the fourth lens element 23. Wherein, the air interval between the second lens 21 and the third lens 22 can be set according to actual needs.

In some examples, the middle group lens group 20 further includes, in order, in a direction away from the front group lens group 10, i.e., in a direction from the object side to the image side: fifth lens 24, sixth lens 25, seventh lens 26 and eighth lens 27. Wherein the fifth lens 24 is located at a side of the fourth lens 23 facing away from the front group lens 10. The surface of the fifth lens element 24 facing the fourth lens element 23 (i.e., the object-side surface) is convex, and the image-side surface of the fifth lens element 24 can be concave. The surface of the sixth lens 25 facing the fifth lens 24 (i.e., the object side) is convex, and the surface of the sixth lens 25 facing away from the fifth lens 24 (i.e., the image side) is concave. The surface of the seventh lens element 26 facing the sixth lens element 25 (i.e., the object-side surface) is convex, and the image-side surface of the seventh lens element 26 is concave. The surface of the eighth lens 27 facing the seventh lens 26 (i.e., the object-side surface) is concave, and the image-side surface of the eighth lens 27 is concave.

Optionally, the air space between the second lens 21 and the third lens 22 is greater than the air space between the remaining adjacent and spaced apart lenses in the middle group lens group 20. Optionally, the air space between the fourth lens 23 and the fifth lens 24 is smaller than the air space between the remaining adjacent and spaced lenses in the middle group lens group 20. Wherein the air space between adjacent lenses refers to the distance between points in the optical axis direction of the surfaces of the adjacent lenses facing each other.

In this embodiment, by reasonably setting the focal power, the surface shape, and the like of each lens in the middle group lens group 20, the focal length and the aberration of the middle group lens group 20 can be effectively reduced, thereby realizing the effects of small projection ratio and high performance.

In some embodiments, the rear group lens group 30 includes, in order, a ninth lens 31, a tenth lens 32, an eleventh lens 33, a twelfth lens 34, a thirteenth lens 35, and a fourteenth lens 36 in a direction away from the middle group lens, that is, in a direction from the object side to the image side; wherein the ninth lens 31 is cemented with the tenth lens 32, the eleventh lens 33 is cemented with the twelfth lens 34, and the thirteenth lens 35 is cemented with the fourteenth lens 36. Through the arrangement, the effects of large aperture and low chromatic aberration can be achieved, and higher imaging quality is obtained.

Illustratively, the image side of the ninth lens element 31 is convex, the object side of the tenth lens element 32 is concave, the image side of the tenth lens element 32 is convex, and the image side of the ninth lens element 31 is cemented with the object side of the tenth lens element. The object-side surface of the eleventh lens element 33 is concave, the image-side surface of the eleventh lens element 33 is concave, the object-side surface of the twelfth lens element 34 is convex, the lateral surface of the twelfth lens element 34 may be concave, and the image-side surface of the eleventh lens element 33 is cemented with the object-side surface of the twelfth lens element 34. The object-side surface of the thirteenth lens element 35 can be concave, the image-side surface of the thirteenth lens element 35 can be concave, the object-side surface of the fourteenth lens element 36 can be convex, the image-side surface of the fourteenth lens element 36 can be concave, and the image-side surface of the thirteenth lens element 35 is cemented with the object-side surface of the fourteenth lens element 36.

The ninth lens 31 is a positive power lens, and the tenth lens 32 is a negative power lens; the eleventh lens 33 is a negative power lens, and the twelfth lens 34 is a positive power lens; the thirteenth lens 35 is a positive power lens, and the fourteenth lens 36 is a negative power lens. In other examples, the positive and negative powers between the two lenses in the same group of doublet lenses may also be reversed, depending on the actual needs, e.g., on the imaging specifications.

In addition, the rear group lens assembly 30 further includes a fifteenth lens element 37, and both an object-side surface and an image-side surface of the fifteenth lens element 37 are convex. The distance between the object side surface of the tenth lens 32 in the rear group lens group 30 and the image side surface of the eighth lens 27 in the middle group lens group 20 is larger than the distance between the image side surface of the fifteenth lens 37 in the rear group lens group 30 and the plate glass group 40.

In this embodiment, by reasonably setting the focal power, the surface shape, and the like of each lens in the rear group lens group 30, the aberration of the middle group lens group 20 can be effectively reduced, which is beneficial to realizing the effects of small projection ratio and high performance.

In some embodiments, the projection lens further includes an aperture (not shown) disposed in the propagation path between the middle group lens group 20 and the rear group lens group 30. The center distance between the cemented lens of the middle group lens group 20 closer to the rear group lens group 30 and the aperture is larger than the center distance between the cemented lens of the rear group lens group 30 closer to the middle group lens group 20 and the aperture in the optical axis direction of the projection lens. Wherein, the cemented lens of the middle group lens group 20 closer to the rear group lens group 30 is the fourth lens 23; the cemented lens of the rear group lens group 30 that is closer to the middle group lens group 20 is a ninth lens 31. The difference between the distance between the cemented lens in the middle group lens group 20 and the diaphragm and the distance between the cemented lens in the rear group lens group 30 and the diaphragm can be set according to actual needs. In some examples, the center distance between the aperture stop and the cemented lens in the middle group lens group 20 that is near the rear group lens group is less than 4mm. For example, the center distance between the aperture stop and the cemented lens in the middle group lens group 20 near the rear group lens group may be 3.5mm or 3mm or 2.5mm or 2mm or 1.5mm or 1mm or 0.5mm or 0.1mm, or a spacing between any two of the above.

Through the distance setting, and the combination of the setting of positive and negative focal power of the cemented lens, chromatic aberration can be effectively corrected, imaging quality is improved, aperture size of the lens is reduced, and volume and cost of the lens are reduced.

In some embodiments, the middle group lens group 20 includes multiple sets of doublet lens groups, with a single lens disposed between each adjacent two sets of doublet lens groups. Illustratively, the middle group lens group 20 may include, in a direction away from the front group lens group 10: the second lens 21, the third lens 22, the fourth lens 23, the fifth lens 24, the sixth lens 25, the seventh lens 26, and the eighth lens 27. Wherein the third lens 22 and the fourth lens 23 are cemented and form a group of cemented doublet lens groups, the sixth lens 25 and the seventh lens 26 are cemented and form a group of cemented doublet lens groups, the fifth lens 24 is a single lens between the two groups of cemented doublet lens groups, the third lens 22 and the sixth have negative optical power, and the fourth lens 23 and the seventh lens 26 have positive optical power. Of course, the number of lenses in the middle group lens group 20 is not limited thereto, and the present embodiment is merely exemplified herein. Through the arrangement, the large aperture and low chromatic aberration effect can be achieved.

In some embodiments, at least one of the middle group lens group 20 and the rear group lens group 30 comprises at least one set of cemented lens groups. That is, the middle group lens group 20 includes at least one group of triple cemented lens groups, and/or the rear group lens group 30 includes at least one group of triple cemented lens groups.

Illustratively, the middle group lens group 20 has one set of three cemented lens groups therein, and the rear group lens group 30 may have three sets of two cemented lens groups or two sets of three cemented lens groups therein.

Alternatively, the middle group lens group 20 has a group of cemented doublet lens groups therein; the rear group lens may have one or two sets of three cemented lens groups, or the rear group lens group 30 has one set of two cemented lens groups and one set of three cemented lens groups, or the rear group lens group 30 has two sets of two cemented lens groups and one set of three cemented lens groups.

Alternatively, the middle group lens group 20 has two groups of cemented doublet lens groups; the rear group lens group 30 may have two groups of double cemented lens groups, or the rear group lens group 30 may have one group of double cemented lens groups and one group of triple cemented lens groups, or the rear group lens group 30 may have one group of double cemented lens groups and two groups of triple cemented lens groups, or the rear group lens group 30 may have two groups of double cemented lens groups and one group of triple cemented lens groups.

In this embodiment, by the above arrangement, aberration problems such as chromatic aberration and spherical aberration can be effectively corrected, thereby improving imaging quality.

The structure and effects of the projection lens shown in fig. 1 will be described below by way of example. The projection lens includes: the first lens 11, the second lens 21, the third lens 22, the fourth lens 23, the fifth lens 24, the sixth lens 25, the seventh lens 26, the eighth lens 27, the ninth lens 31, the tenth lens 32, the eleventh lens 33, the twelfth lens 34, the thirteenth lens 35, the fourteenth lens 36 and the fifteenth lens 37 are sequentially arranged from the object side to the image side, and the image light sequentially passes through the fifteenth lens 37, the fourteenth lens 36, the thirteenth lens 35, the twelfth lens 34, the eleventh lens 33, the tenth lens 32, the ninth lens 31, the eighth lens 27, the seventh lens 26, the sixth lens 25, the fifth lens 24, the fourth lens 23, the third lens 22 and the second lens 21, is incident on the first lens 11, and is reflected by the first lens 11 to form a projection image. Wherein the third lens 22 is glued with the fourth lens 23; the ninth lens 31 is cemented with the tenth lens 32, the eleventh lens 33 is cemented with the twelfth lens 34, and the thirteenth lens 35 is cemented with the fourteenth lens 36.

The fourteenth lens 36 is provided with a plate glass group 40 on the image side; the sheet glass group 40 includes a first sheet glass 41, a second sheet glass 42, and a third sheet glass 43, which are disposed in this order, in a direction from the object side toward the image side.

In the optical axis direction, the center distance between the object side surface of the first lens 11 and the object side surface of the second lens 21 is L1; a center distance between the object side surface of the second lens 21 and the object side surface of the ninth lens 31 in the optical axis direction is L2; in the optical axis direction, the optical length of the rear group lens group 30, that is, the center distance between the object side surface of the ninth lens 31 and the image side surface of the fifteenth lens 37 is L3. The projection lens satisfies: l1/l2=1.07; l3/l2=0.50.

In this embodiment, the surface type of each lens is set as follows: the object side surface S1 of the first lens element 11 is convex, and the image side surface S2 is concave; the object side surface S3 of the second lens element 21 is concave, and the image side surface S4 is concave; the object side surface S5 of the third lens element 22 is concave, and the image side surface S6 is concave; the fourth lens element 23 has a convex object-side surface S7 and a convex image-side surface S8; the fifth lens element 24 has a convex object-side surface S9 and a concave image-side surface S10; the object side surface S11 of the sixth lens element 25 is convex, and the image side surface S12 is concave; the object side surface S13 of the seventh lens element 26 is convex, and the image side surface S14 is concave; the object side surface S15 of the eighth lens element 27 is concave, and the image side surface S16 is concave; the object side surface S17 of the ninth lens element 31 with a concave surface and the image side surface S18 with a convex surface; the tenth lens element 32 has a concave object-side surface S19 and a convex image-side surface S20; the object side surface S21 of the eleventh lens element 33 has a concave surface, and the image side surface S22 has a concave surface; the object side surface S23 of the twelfth lens element 34 is convex, and the image side surface S24 is concave; the thirteenth lens element 35 has a concave object-side surface S25 and a convex image-side surface S26; the object-side surface S27 of the fourteenth lens element 36 is concave, and the image-side surface S28 is convex; the fifteenth lens element 37 has a convex object-side surface S29 and a convex image-side surface S30; the first sheet glass 41 has an object side surface S31 and an image side surface S32; the second plate glass 42 has an object side surface S33 and an image side surface S34; the third plate glass 43 has an object side surface S35 and an image side surface S36. The surfaces S3 to S7 are aspherical surfaces, and the rest are spherical surfaces. The projection ratio of this embodiment can be less than 0.21.

In the present embodiment, the surface shape x of the aspherical lens can be defined by, but not limited to, the following aspherical formula (1):

wherein x is the distance vector height from the vertex of the aspheric surface when the aspheric surface is at the position with the height h along the optical axis direction; c is the paraxial curvature of the aspheric surface, c=1/R (i.e., paraxial curvature c is the inverse of radius of curvature R); k is a conic coefficient; ai is the correction coefficient of the aspherical i-th order.

Table 1 below shows basic parameters of the projection lens of the present embodiment, in which the unit of curvature radius and thickness are both millimeters (mm). Table 2 below shows K values and higher order coefficients A4, A6, A8, a10, a12, a14, a16, and a18 of respective aspherical mirror surfaces S1 (i.e., surface 4 in table 1) to S4 (i.e., surface 8 in table 1) that can be used in the projection lens of the present embodiment.

TABLE 1

TABLE 2

FIG. 2 shows MTF curves of the imaging quality of the projection lens of the present embodiment, which are used to represent the imaging quality of the light beam at different fields of view, where the different curves correspond to different fields of view; as can be seen from fig. 2, the MTF curves have an abscissa of 93lp/mm (line pair/mm) corresponding to an ordinate of more than 60%, which means that each pixel can be clearly analyzed, resulting in good image quality.

Fig. 3 shows a distortion curve of the projection lens of the present embodiment by using light beams with wavelengths of 455mm, 550mm and 630mm, and the distortion value can be reduced to 0.35% while ensuring the resolution, and fig. 3 reflects that the projection lens of the present embodiment has a lower optical distortion level to some extent.

Fig. 4 shows longitudinal spherical aberration curves of the projection lens according to the present embodiment, which represent spherical aberrations corresponding to different focal lengths, using light rays with wavelengths of 455mm, 550mm, and 630 mm. Fig. 5 shows astigmatic curves of the projection lens provided in this embodiment using light with wavelengths 455mm, 550mm, and 630 mm. It shows meridian image surface curvature (curves T1, T2 and T3) and sagittal image surface curvature (curves S1, S2 and S3), and fig. 4 and 5 reflect that the projection lens has a low optical distortion level to some extent.

As can be seen from fig. 3 to 5, the projection lens of the present embodiment has good imaging quality.

The present embodiment also provides a projection display apparatus including: a projection lens, a spatial light modulator, and a projection light source; the projection light source is used for generating illumination light, the illumination light is modulated Cheng Yingxiang by the spatial light modulator, the image light is projected to the projection lens, and a projection picture is formed by the projection lens. The structure, function and implementation process of the projection lens are the same as or similar to those of the projection lens in any of the foregoing embodiments, and the description of this embodiment is omitted here.

It should be noted that: in the drawings, the thickness, size, and shape of the lenses have been slightly exaggerated for convenience of explanation. In particular, the spherical or aspherical shape shown in the drawings is shown by way of example. That is, the shape of the spherical or aspherical surface is not limited to the shape of the spherical or aspherical surface shown in the drawings. The figures are merely examples and are not drawn to scale.

In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present invention.

Furthermore, the terms "first," "second," and the like, as used in embodiments of the present invention, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or as implying any particular number of features in the present embodiment. Thus, a feature of an embodiment of the invention that is defined by terms such as "first," "second," etc., may explicitly or implicitly indicate that at least one such feature is included in the embodiment. In the description of the present invention, the word "plurality" means at least two or more, for example, two, three, four, etc., unless explicitly defined otherwise in the embodiments.

In the present invention, unless explicitly stated or limited otherwise in the examples, the terms "mounted," "connected," and "fixed" as used in the examples should be interpreted broadly, e.g., the connection may be a fixed connection, may be a removable connection, or may be integral, and it may be understood that the connection may also be a mechanical connection, an electrical connection, etc.; of course, it may be directly connected, or indirectly connected through an intermediate medium, or may be in communication with each other, or in interaction with each other. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to specific embodiments.

In the present invention, unless expressly stated or limited otherwise, a first feature "up" or "down" a second feature may be the first and second features in direct contact, or the first and second features in indirect contact via an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.

While embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention.

Claims

1. A projection lens, wherein the projection lens has an optical axis, the projection lens comprising: a rear group lens group, a middle group lens group and a front group lens group which are distributed along the transmission direction of image light, wherein the image light is incident to the front group lens group through the rear group lens group and the middle group lens group, and the front group lens group reflects the image light to form a projection picture;

wherein, the projection lens satisfies:

L1≧L2；

wherein L1 is a distance between a center position of a side of the middle group lens group, which is close to the front group lens group, to a side of the front group lens group, which is far from the middle group lens group, in the optical axis direction; l2 is a distance between a center position of a side of the middle group lens group away from the rear group lens group and the rear group lens group along the optical axis direction.

2. The projection lens of claim 1, wherein the projection lens satisfies: L1/L2 is more than or equal to 1.0 and less than or equal to 5.0.

3. The projection lens of claim 1, wherein the projection lens satisfies:

L3＜L2；

wherein L3 is an optical length of the rear group lens group along the optical axis direction;

and/or the number of the groups of groups,

the projection lens satisfies the following conditions: l3 is less than L1;

wherein L3 is an optical length of the rear group lens group along the optical axis direction.

4. The projection lens of claim 1 wherein the middle group lens group and the rear group lens group each comprise cemented lenses, and the number of lenses in the rear group lens group is the same as the number of lenses in the middle group lens group.

5. The projection lens of claim 1 wherein the middle group lens group comprises a second lens, a third lens and a fourth lens in that order in a direction away from the front group lens group;

the third lens is glued with the fourth lens, the third lens is a negative focal power lens, and the fourth lens is a positive focal power lens.

6. The projection lens of claim 5 wherein the middle group lens group further comprises, in order, in a direction away from the front group lens group: a fifth lens, a sixth lens, a seventh lens and an eighth lens;

wherein the fifth lens is positioned at one side of the fourth lens, which is away from the front group lens group;

the surface of the fifth lens facing the fourth lens is a convex surface, the surface of the sixth lens facing the fifth lens is a convex surface, the surface of the sixth lens facing away from the fifth lens is a concave surface, the surface of the seventh lens facing the sixth lens is a convex surface, and the surface of the eighth lens facing the seventh lens is a concave surface.

7. The projection lens of claim 1 wherein the rear group lens group comprises, in order, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, a thirteenth lens, and a fourteenth lens in a direction away from the middle group lens;

wherein the ninth lens is cemented with a tenth lens, the eleventh lens is cemented with a twelfth lens, and the thirteenth lens is cemented with a fourteenth lens.

8. The projection lens of claim 7 wherein the ninth lens is a positive power lens and the tenth lens is a negative power lens;

the eleventh lens is a negative focal power lens, and the twelfth lens is a positive focal power lens;

the thirteenth lens is a positive power lens, and the fourteenth lens is a negative power lens.

9. The projection lens according to claim 1, further comprising an aperture, the aperture being provided in an optical path between the middle group lens group and the rear group lens group, a center distance between a cemented lens of the middle group lens group close to the rear group lens group and the aperture being greater than a center distance between a cemented lens of the rear group lens group close to the middle group lens group and the aperture in an optical axis direction of the projection lens.

10. The projection lens of claim 9 wherein a center distance between the aperture and a cemented lens of the middle group lens group that is adjacent to the rear group lens group is less than 4mm.

11. The projection lens of claim 1 wherein the front group lens group comprises a first lens having a transmissive surface facing the middle group lens group and a reflective surface facing away from the middle group lens group; the projection lens satisfies the following conditions:

0.3880≤R1/R2≤0.5820；

wherein R1 is the radius of curvature of the reflecting surface of the first lens; r2 is the radius of curvature of the transmission surface of the first lens.

12. A projection display device, comprising: the projection lens of any one of claims 1 to 11, and a spatial light modulator, projection light source;

the projection light source is used for generating illumination light, the illumination light is modulated Cheng Yingxiang by the spatial light modulator, the image light is projected to the projection lens, and a projection picture is formed by the projection lens.