CN114114609B

CN114114609B - Projection lens

Info

Publication number: CN114114609B
Application number: CN202010906286.5A
Authority: CN
Inventors: 张硕杰; 陈信德; 王国权
Original assignee: Young Optics Inc
Current assignee: Young Optics Inc
Priority date: 2020-09-01
Filing date: 2020-09-01
Publication date: 2024-06-21
Anticipated expiration: 2040-09-01
Also published as: CN114114609A

Abstract

A projection lens comprises a first lens group and a second lens group which are separated by a minimum position of the inner diameter of a lens barrel of the projection lens. The first group of lenses comprises an aspherical lens and 2-4 spherical lenses, and the lens closest to the magnifying side is a negative diopter glass lens. The second group of lenses comprises 4-7 spherical lenses, and one of the lenses comprises a cemented lens. L is the shortest length between the outer surfaces of the outermost lenses at the two ends of the projection lens, D1 is the maximum length between the outermost turning points at the two ends of the lens closest to the magnification side, DL is the maximum length between the outermost turning points at the two ends of the lens closest to the reduction side, and the projection lens meets L/DL >3.5 and D1/DL >1.1.

Description

Projection lens

Technical Field

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

Background

With the progress of photoelectric technology, image devices such as projectors, digital video cameras and digital still cameras have been widely used in daily life. One of the core components of these imaging devices is an optical lens. By adjusting the optical lens, the image is focused on the screen or the charge coupled device clearly, so that the imaging quality is closely related to the optical quality of the optical lens. In the highly competitive market, various manufacturers do not aim to improve the optical quality of the optical lens and reduce the weight, volume and manufacturing cost of the optical lens so as to improve the competitive advantage of the imaging device. Therefore, how to manufacture a projection lens with small size, high performance, low aberration, large aperture, low cost, and high resolution is one of the important subjects of those skilled in the art.

Disclosure of Invention

According to one aspect, the present invention provides a projection lens including a first lens group and a second lens group separated by a minimum position (aperture) of an inner diameter of a lens barrel of the projection lens. The first group of lenses comprises an aspherical lens and 2-4 spherical lenses, and the lens closest to the magnifying side is a negative diopter glass lens. The second group of lenses comprises 4-7 spherical lenses, and one of the lenses comprises a cemented lens. L is the shortest length between the outer surfaces of the outermost lenses at the two ends of the projection lens, D1 is the maximum length between the outermost turning points at the two ends of the lens closest to the magnification side, DL is the maximum length between the outermost turning points at the two ends of the lens closest to the reduction side, and the projection lens meets L/DL >3.5 and D1/DL >1.1.

According to another aspect of the present invention, there is provided a projection lens including a first lens group and a second lens group sequentially arranged from an enlargement side to a reduction side. The first lens group comprises 2-3 lenses, one of the lenses is an aspheric lens which is the only aspheric lens of the projection lens, and the lens closest to the amplifying side is a glass lens. The second lens group comprises 5-9 lenses and is arranged in the second lens barrel, wherein the plurality of lenses are combined into a cemented lens. L is the shortest length between the outer surfaces of the outermost lenses at the two ends of the projection lens, D1 is the radial length of the outermost turning points at the two ends of the lens at the closest magnification side, DL is the radial length of the outermost turning points at the two ends of the lens at the closest reduction side, and the projection lens meets the requirements of L/D1>2.5 and D1/DL >1.1.

The first lens of the projection lens of the embodiment uses a glass lens, which solves the problems of easy scratch and manufacturability when using a plastic aspherical lens. Furthermore, the use of a cemented lens may reduce residual lateral chromatic aberration in the system. Therefore, a projection lens design with good aberration eliminating capability, easy miniaturization and better imaging quality can be provided.

The foregoing description is only an overview of the present invention, and is intended to be implemented in accordance with the teachings of the present invention, as well as the preferred embodiments thereof, together with the following detailed description of the invention, given by way of illustration only, together with the accompanying drawings.

Drawings

Fig. 1 is a schematic view of a projection lens according to a first embodiment of the present invention.

Fig. 2 is a schematic view of a projection lens according to a second embodiment of the present invention.

Fig. 3 is a schematic view of a projection lens according to a third embodiment of the present invention.

Fig. 4 is a schematic view of a projection lens according to a fourth embodiment of the present invention.

Fig. 5 is a schematic view of a projection lens according to a fifth embodiment of the present invention.

Fig. 6 is a graph of optical transfer function of a projection lens according to a first embodiment of the present invention.

Fig. 7 is an optical analog data diagram of lateral chromatic aberration of a projection lens of the first embodiment of the present invention.

Fig. 8 is a graph of curvature of field and distortion of a projection lens according to a first embodiment of the present invention.

Fig. 9 is a schematic view of a projection lens assembled in a lens barrel according to an embodiment of the invention.

FIG. 10 is a schematic diagram of a projection system according to an embodiment of the invention.

Detailed Description

The foregoing and other features, aspects and advantages of the present invention will become more apparent from the following detailed description of various embodiments, which proceeds with reference to the accompanying drawings. The directional terms mentioned in the following embodiments, such as "upper", "lower", "front", "rear", "left", "right", etc., are only directions referring to the attached drawings. Thus, directional terminology is used for purposes of illustration and is not intended to be limiting of the invention. In addition, the terms "first" and "second" used in the following embodiments are used to identify the same or similar elements, and are not intended to limit the elements. In addition, the following embodiments are further described with respect to the projection device and the display system, and those skilled in the art can apply the connection system to any desired situation according to actual requirements. The lens in the present invention is at least capable of allowing part of light to pass through, and at least one of the light incident and light emergent surfaces has a radius of curvature which is not infinite; in other words, at least one of the light incident surface and the light emergent surface of the lens is not planar. But for example, flat glass is not the lens to which the present invention refers. In addition, the magnification side is a side closer to a projection surface (e.g., a projection screen) when the specified focus lens is applied to a projection system; the reduced side is the side closer to the light valve when the specified focus lens is used in a projection system. When the fixed focus lens is applied to an image capturing system, the enlarged side is the side close to the object to be photographed, and the reduced side is the side closer to the photosensitive element.

An embodiment of the invention provides a projection lens. By the design of the embodiment of the invention, a projection lens design with good aberration eliminating capability, easy miniaturization and better imaging quality can be provided.

Fig. 1 is a schematic view of a projection lens according to an embodiment of the invention. Referring to fig. 1, in the present embodiment, a projection lens 10a has a barrel (not shown) in which components such as a first lens group 20, an aperture 14, a second lens group 30 and the like are accommodated. The diaphragm 14 is disposed between the first lens group 20 and the second lens group 30. That is, with the aperture 14 as a dividing line, the projection lens 10a may include the first lens assembly 20 and the second lens assembly 30, and the second lens assembly 30 may further be matched with the through-type smooth image device TSP (Transmissive Smooth Picture) (not shown), the prism PR (not shown), the glass protection cover CG18 and the light valve LV (not shown) on a side opposite to the reduction side. In this example, the entire first lens group 20, the diaphragm 14 and the second lens group 30 can be moved back and forth along the optical axis 12 relative to the imaging plane 19 to be focused. That is, in focusing, the distance (Interval) between the first lens group 20, the diaphragm 14, and the second lens group 30 of the projection lens 10a is fixed, and this focusing method is also called overall focusing. In another embodiment, only the first lens group 20 or the second lens group 30 can be used to move back and forth relative to the imaging plane 19 for focusing, which is called as group focusing. In this case, the imaging plane 19 is coplanar with the surface of the light valve LV. The light valve LV in the present invention is an optical device capable of converting illumination light into image light, such as DMD, LCD, LCOS, and is known to those skilled in the art. In this example, the light valve is a DMD. In this example, the projection lens 10a is a telecentric (TELECENTRIC) lens.

In this example, the first lens group 20 has positive diopter, and the second lens group 30 has positive diopter. The first lens group 20 includes a lens L1, a lens L2, and a lens L3 arranged in order from an enlargement side (OS, left side in fig. 1) to a reduction side (IS, right side in fig. 1) along the optical axis 12. The second lens group 30 includes a lens L4, a lens L5, a lens L6, a lens L7, and a lens L8, which are arranged in order from the enlargement side to the reduction side along the optical axis 12. The diopters of lenses L1-L8 are negative, positive, negative, positive and positive, respectively. The sum of the diopters of the lenses L1 and L2 is negative, and the sum of the diopters of the lenses L3 to L8 is positive; the sum of the diopters of the lenses L1, L2 and L3 is positive, and the sum of the diopters of the lenses L4 to L8 is positive. The materials of the lenses L1-L8 are glass, plastic, glass glass, and glass. In addition, if S is a spherical lens and ASP is an aspherical lens, lenses L1-L8 are S, ASP, S, S, S, S, S, S and S, respectively. In addition, the optical surface shapes of the lenses L1 to L8 are convex-concave, convex-convex, concave-convex, convex-convex, and convex-concave, respectively. The image enlargement side OS of each embodiment of the present invention IS disposed on the left side of each drawing, and the image reduction side IS disposed on the right side of each drawing, respectively, and will not be repeated.

The diaphragm 14 is an Aperture Stop (Aperture Stop), which is a separate element or integrated with other optical elements, and is typically the minimum inner diameter of the lens barrel. In this embodiment, the aperture is similar to the aperture by blocking the peripheral light and leaving the middle portion transparent, and the mechanism may be adjustable. By adjustable, it is meant that the position, shape or transparency of the machine element is adjusted. Alternatively, the aperture may be coated with an opaque light absorbing material on the surface of the lens, and the light absorbing material may be made to pass through the central portion of the aperture to limit the light path.

Each lens defines a lens diameter. For example, as shown in fig. 1, the lens diameter refers to the distance between the outermost turning points P1 and Q1 of the lens L1 and the optical axis 12 in the direction perpendicular to the optical axis 12 (e.g., the maximum length between the outermost turning points of the lens L1, or the radial distance between the outermost turning points P1 and Q1 of the lens L1 and the optical axis 12), or the distance between the outermost turning points P2 and Q2 of the lens L8 and the optical axis 12 in the direction perpendicular to the optical axis 12 (e.g., the maximum length between the outermost turning points of the lens DL 8, or the radial distance between the outermost turning points P2 and Q1 of the lens L8 and the optical axis 12). In addition, EFL as referred to herein refers to the effective focal length (EFFECTIVE FOCAL LENGTH) of the system. And L refers to the shortest distance of the first surface of the lens closest to the magnification side to the second surface of the lens closest to the reduction side of the projection lens. Furthermore, in the present invention, the projection lens satisfies L/DL >3.5 and D1/DL >1.1 or L/D1>2.5 and D1/DL >1.1. While TTL refers to the distance along the optical axis 12 from the first surface of the lens closest to the magnification side to the second surface of the lens closest to the reduction side of the projection lens.

The aperture value of the present invention is represented by F/# as indicated in the above table. When the lens is applied to a projection system, an imaging surface is a light valve surface. In the embodiment of the invention, F/# is less than or equal to 1.8. In the present invention, the full field angle FOV refers to the angle of the light receiving of the optical surface S1 closest to the image magnification end, i.e., the field of view (field of view) measured by diagonal line. In the present invention, the FOV is between 45 degrees and 85 degrees.

The design parameters of the lens and its peripheral components of the projection lens 10a are shown in table one. However, the following description is not intended to limit the invention, and persons skilled in the art will recognize that other suitable modifications may be made to the parameters or settings of the invention, while still remaining within the scope of the invention.

List one

Furthermore, the designations shown in the tables refer to the surfaces as being aspheric, and are spherical if not labeled. In each of the following design examples of the present invention, the aspherical polynomial is expressed by the following formula:

In the above formula, x is the offset (sag) in the direction of the optical axis a, c' is the inverse of the radius of the sphere of revolution (osculating sphere), that is, the inverse of the radius of curvature near the optical axis a, k is the conic coefficient (conic constant), and y is the aspherical height, that is, the height from the center of the lens to the edge of the lens. a-G represent each order aspheric coefficient of the aspheric polynomial, respectively. Table two lists the aspherical coefficients and the quadric coefficient values of each order of each lens surface in the lens barrel according to the first embodiment of the present invention.

Watch II

	S3	S4
			K	-2.10E+00	-9.49E-01
A	-9.46E-04	-2.09E-03
			B	1.85E-05	4.10E-05
C	-2.12E-07	-5.98E-07
			D	1.34E-09	4.91E-09
E	-3.58E-12	-1.75E-11

According to the design of the above embodiment, in order to solve the problems of easy scratching, manufacturability and high cost of using aspheric lenses, in this example, the glass spherical lens is used for the first lens L1 of the front group (the enlargement side) and the last lens L8 of the rear group (the reduction side), and the lens L2 is designed as a plastic aspheric lens, and the lens L2 is disposed in the first lens group 20.

In addition, the first lens and the last lens of the previous example use spherical lenses, and more lateral chromatic aberration (lateral chromatic aberration) remains in the system, so that the lenses L4, L5, L6 are arranged as triple cemented lenses to reduce the residual lateral chromatic aberration in the system. That is, the lenses L4, L5, L6 include three lenses cemented to each other. It should be noted that in this example, the three cemented lenses are disposed between the aperture stop and the stop side. The lens-to-lens bonding or the bonding lens in the present invention refers to a lens group formed by fixing a plurality of lenses to each other and fixing the lenses, but the fixing means is not limited to an adhesive. For example, in the present embodiment, the three lenses are fixed by optical colloid, but the invention is not limited thereto, and the three lenses may be clamped and fixed by mechanical means (such as positioning grooves) when needed. In another embodiment, the three cemented lenses may be replaced by one cemented doublet or two cemented doublets.

In the present embodiment, the surface S18 is coplanar with the imaging plane 19 of the projection lens 10 a. In the present invention, the back focal length or BFL is an air back focal length (back focal lengthequivalent in air) of a specified focal lens, and for example, the back focal length BFL is an equivalent back focal length obtained by the lenses L1 to L8 when all elements other than the lenses L1 to L8 are replaced with air. Since the second lens group 30 has a transmissive smooth image device TSP and a prism PR in the shrinking direction in this example, the BFL is longer than that of a conventional lens.

In this example, the aperture value of the projection lens 10a is about 1.6; EFL is about 8.899mm; TTL is about 67.167mm; BFL is about 13.43mm. The small EFL characteristic of the projection lens 10a allows the projection lens to be used in portable projectors that include batteries and do not require external power.

The design of the second embodiment 10b of the projection lens of the present invention will be described below. Referring to fig. 2, in the present embodiment, the projection lens 10b has a lens barrel (not shown), in which the first lens group 20, the aperture 14, the second lens group 30 and other elements are accommodated. The diaphragm 14 is disposed between the first lens group 20 and the second lens group 30. That is, with the aperture 14 as a dividing line, the projection lens 10b may include the first lens assembly 20 and the second lens assembly 30, and the second lens assembly 30 may further be matched with the through-type smooth image device TSP (Transmissive Smooth Picture) (not shown), the prism PR (not shown), the glass protection cover CG18 and the light valve LV (not shown) on a side opposite to the reduction side. In this example, the entire first lens group 20, the diaphragm 14 and the second lens group 30 can be moved back and forth along the optical axis 12 relative to the imaging plane 19 to be focused. That is, the distance (Interval) between the first lens group 20, the diaphragm 14, and the second lens group 30 of the projection lens 10b is fixed during focusing. In this case, the imaging plane 19 is coplanar with the surface of the light valve LV. The light valve LV in the present invention is an optical device capable of converting illumination light into image light, such as DMD, LCD, LCOS, and is known to those skilled in the art. In this example, the light valve is a DMD. In this example, the projection lens 10b is a telecentric (TELECENTRIC) lens.

In this example, the first lens group 20 has positive diopter, and the second lens group 30 has positive diopter. The first lens group 20 includes a lens L1, a lens L2, and a lens L3 arranged in order from an enlargement side (OS, left side in fig. 2) to a reduction side (IS, right side in fig. 2) along the optical axis 12. The second lens group 30 includes a lens L4, a lens L5, a lens L6, a lens L7, a lens L8, and a lens L9, which are arranged in order from the enlargement side to the reduction side along the optical axis 12. The diopters of lenses L1-L9 are negative, positive, negative, positive, and positive, respectively. The sum of the diopters of the lenses L1 and L2 is negative, and the sum of the diopters of the lenses L3 to L9 is positive; the sum of the diopters of the lenses L1, L2 and L3 is positive, and the sum of the diopters of the lenses L4 to L9 is positive. The materials of the lenses L1-L9 are glass, plastic, glass glass, and glass. In addition, if S is a spherical lens and ASP is an aspherical lens, lenses L1-L9 are S, ASP, S, S, S, S, S, S and S, respectively. In addition, the optical surface shapes of the lenses L1 to L9 are convex-concave, convex-convex, concave-concave, convex-convex, concave-convex, convex-convex and convex-convex respectively.

In this example, the design parameters of the lens and its peripheral components in the projection lens 10b are shown in table three.

Watch III

Table four lists the aspherical coefficients and the quadric coefficient values of each order of each lens surface of the lens barrel in the second embodiment of the present invention.

Table four

	S3	S4
			K	-1.04E+00	-8.29E-01
A	-8.24E-04	-1.33E-03
			B	9.69E-06	1.17E-05
C	-6.55E-08	-9.51E-08
			D	1.90E-10	-2.74E-11

As can be seen from tables three and four, one main difference between the second embodiment and the first embodiment is that the projection lens 10b is provided with a lens L4 between the aperture 14 and the three cemented lens.

The design of the third embodiment 10c of the projection lens of the present invention will be described below. Referring to fig. 3, in this example, the first lens group 20 has positive diopter, and the second lens group 30 has positive diopter. The first lens group 20 includes a lens L1, a lens L2, and a lens L3 arranged in order from an enlargement side (OS, left side in fig. 3) to a reduction side (IS, right side in fig. 3) along the optical axis 12. The second lens group 30 includes a lens L4, a lens L5, a lens L6, a lens L7, a lens L8, and a lens L9, which are arranged in order from the enlargement side to the reduction side along the optical axis 12. The diopters of lenses L1-L9 are negative, positive, negative, positive, and positive, respectively. The sum of the diopters of the lenses L1 and L2 is negative, and the sum of the diopters of the lenses L3 to L9 is positive; the sum of the diopters of the lenses L1, L2 and L3 is positive, and the sum of the diopters of the lenses L4 to L9 is positive. The materials of the lenses L1-L9 are glass, plastic, glass glass, and glass. In addition, if S is a spherical lens and ASP is an aspherical lens, lenses L1-L9 are S, ASP, S, S, S, S, S, S and S, respectively. In addition, the optical surface shapes of the lenses L1 to L9 are convex-concave, convex-convex, concave-convex, convex-convex and convex-concave, respectively.

In this example, the design parameters of each lens and its peripheral components in the projection lens 10c are shown in table five.

TABLE five

Table six shows the aspherical coefficients and the quadric coefficient values of each order of each lens surface of the lens barrel in the third embodiment of the present invention.

TABLE six

As can be seen from the two tables, the main difference between the third embodiment and the second embodiment is that the lens L4 diopter of the projection lens 10c changes from negative to positive.

The design of the fourth embodiment 10d of the projection lens of the present invention will be described below. Referring to fig. 4, in this example, the first lens group 20 has positive diopter, and the second lens group 30 has positive diopter. The first lens group 20 includes a lens L1, a lens L2, and a lens L3 arranged in order from an enlargement side (OS, left side in fig. 4) to a reduction side (IS, right side in fig. 4) along the optical axis 12. The second lens group 30 includes a lens L4, a lens L5, a lens L6, a lens L7, and a lens L8, which are arranged in order from the enlargement side to the reduction side along the optical axis 12. The diopters of lenses L1-L8 are negative, positive, negative and positive, respectively. The sum of the diopters of the lenses L1 and L2 is negative, and the sum of the diopters of the lenses L3 to L8 is positive; the sum of the diopters of the lenses L1, L2 and L3 is positive, and the sum of the diopters of the lenses L4 to L8 is positive. The materials of the lenses L1-L8 are glass, plastic, glass glass, and glass. In addition, if S is a spherical lens and ASP is an aspherical lens, lenses L1-L8 are S, ASP, S, S, S, S, S and S, respectively. In addition, the optical surface shapes of the lenses L1 to L8 are convex-concave, convex-convex, convex-concave, convex-convex, concave-convex and convex-flat, respectively.

In this example, the design parameters of each lens and its peripheral components in the projection lens 10d are shown in table seven.

Watch seven

Table eight lists the respective order aspherical coefficients and quadric surface coefficient values of the respective lens surfaces of the lens barrel in the fourth embodiment of the present invention.

Table eight

	S3	S4
			K	-9.06E-01	-9.83E-01
A	-1.15E-03	-1.42E-03
			B	1.41E-05	1.97E-05
C	-1.09E-07	-1.78E-07
			D	3.67E-10	6.12E-10

As can be seen from the two tables, the main difference between the fourth embodiment and the third embodiment is that the projection lens 10d has only one lens L8 between the triple cemented lens and the imaging plane 19.

Fig. 5 is a schematic diagram of a projection lens 10e according to an embodiment of the invention. Referring to fig. 5, in the present embodiment, the first lens group 20 has positive diopter, and the second lens group 30 has positive diopter. The first lens group 20 includes a lens L1, a lens L2, and a lens L3 arranged in order from the enlargement side (left side of OS, 5) to the reduction side (right side of IS, fig. 5) along the optical axis 12. The second lens group 30 includes a lens L4, a lens L5, a lens L6, a lens L7, a lens L8, and a lens L9, which are arranged in order from the enlargement side to the reduction side along the optical axis 12. The diopters of lenses L1-L9 are negative, positive, negative, positive, and positive, respectively. The sum of the diopters of the lenses L1 and L2 is negative, and the sum of the diopters of the lenses L3 to L9 is positive; the sum of the diopters of the lenses L1, L2 and L3 is positive, and the sum of the diopters of the lenses L4 to L9 is positive. The materials of the lenses L1-L9 are glass, plastic, glass glass, and glass. In addition, if S is a spherical lens and ASP is an aspherical lens, lenses L1-L9 are S, ASP, S, S, S, S, S, S and S, respectively. In addition, the optical surface shapes of the lenses L1 to L9 are convex-concave, convex-convex, concave-concave, convex-convex, concave-convex, convex-convex and convex-concave, respectively.

The design parameters of the lens and its peripheral elements of the projection lens 10e are shown in table nine. However, the following description is not intended to limit the invention, and persons skilled in the art will recognize that other suitable modifications may be made to the parameters or settings of the invention, while still remaining within the scope of the invention.

Table nine

Table ten shows the aspherical coefficients and the quadric coefficient values of each order of each lens surface in the lens barrel in the fifth embodiment of the present invention.

Ten meters

	S3	S4
			K	-9.19E-01	-9.90E-01
A	-1.15E-03	-1.50E-03
			B	1.26E-05	1.98E-05
C	-8.71E-08	-1.69E-07
			D	2.56E-10	5.98E-10

As can be seen from the two tables, the main difference between the fifth embodiment and the first embodiment is that the projection lens 10e is provided with three lenses L7, L8, L9 between the three cemented lens and the imaging plane 19, and the refractive powers of the three cemented lenses are positive, negative, and positive in sequence, while the projection lens 10a is provided with only two lenses L7, L8 between the three cemented lens and the imaging plane 19, and the refractive powers of the three cemented lenses are negative, positive, and negative in sequence.

Fig. 6 to 8 are graphs of optical transfer functions, graphs of optical analog data of lateral chromatic aberration, and graphs of curvature of field and distortion of the lens 10a according to an embodiment of the present invention, respectively. Fig. 6 is a graph of optical transfer function (modulation transfer function, MTF) with the horizontal axis representing spatial frequency per millimeter (spatial frequency IN CYCLES PER MILLIMETER), and the vertical axis representing the modulus of optical transfer function (modulus of the OTF), and in fig. 6 is a graph of simulated data for light having a wavelength between 455 nm and 628 nm. Fig. 7 is an optical simulation data plot of lateral chromatic aberration simulated with light having a wavelength between 455 nanometers and 628 nanometers. In fig. 8, a curve S is data in the sagittal (sagittal) direction, and a curve T is data in the meridional (tangential) direction. The graphs shown in the simulated data graphs of fig. 6 to 8 are all within the standard range, so that it can be verified that the projection lens 10a of the present embodiment can actually have the characteristics of good optical imaging quality.

Fig. 9 is a schematic diagram showing a projection lens 10f according to another embodiment of the invention assembled in a lens barrel. The projection lens includes a first lens group 20 and a second lens group 30 sequentially arranged from a magnification side OS to a reduction side IS. The first lens group 20 includes 2 lenses (L1, L2), and is provided in the first barrel 22, and the lens L2 is an aspherical lens, and the aspherical lens L2 is the only aspherical lens of the projection lens 10f, and the lens L1 closest to the magnification side OS is a glass lens. The second lens group 30 comprises 6 lenses (L3-L8) and is arranged in the second lens barrel 30, wherein the lenses (L4, L5 and L6) are combined into a cemented lens. The second sleeve 24 encloses at least a portion of the first sleeve 22. In one embodiment, the first sleeve 22 may be replaced with a sleeve that encloses at least a portion of the second sleeve 24. In one embodiment, the first sleeve and the second sleeve do not overlap each other. In an embodiment, the projection lens further includes a main barrel (main barrel), and the main barrel covers the first sleeve and the second sleeve at the same time. In one embodiment, the first sleeve material is plastic and the second sleeve material is metal. In one embodiment, the second sleeve material is plastic and the first sleeve material is metal. In one embodiment, the first sleeve and the second sleeve may be both plastic or both metal.

Furthermore, please refer to fig. 10, which is a schematic diagram illustrating a projection lens according to another embodiment of the present invention applied to a projection system. The projection system 300 includes an illumination system 310, a light valve 320, a projection lens 330, and a transmissive smooth image device 100. Wherein the illumination system 310 has a light source 312 adapted to provide a light beam 314, and the light valve 320 is configured in a transmission path of the light beam 314. The light valve 320 is adapted to convert the light beam 314 into a plurality of sub-images 314a. In addition, the projection lens 330 is disposed on the transmission path of the sub-images 314a, and the light valve 320 is located between the illumination system 310 and the projection lens 330. In addition, the transmissive smooth image device 100 may be disposed between the light valve 320 and the projection lens 330, for example, between the light valve 320 and the tir prism 319 or between the tir prism 319 and the projection lens 330, and is located on the transmission paths of the sub-images 314a. In the projection system 300, the light source 312 may include, for example, a red light emitting diode 312R, a green light emitting diode 312G, and a blue light emitting diode 312B, and the color light emitted by each light emitting diode is combined by a light combining device 316 to form a light beam 314, and the light beam 314 sequentially passes through a light collecting column (light integration rod) 317, a lens group 318, and a total internal reflection Prism (TIR Prism) 319. The tir prism 319 then reflects the light beam 314 to the light valve 320. At this time, the light valve 320 converts the light beam 314 into a plurality of sub-images 314a, and the sub-images 314a sequentially pass through the tir prism 319 and the transmissive smooth image device 100, and project the sub-images 314a onto the imaging plane T1 through the projection lens 330. In the present embodiment, when the sub-images 314a pass through the transmissive smooth image device 100, the transmissive smooth image device 100 changes the transmission path of a part of the sub-images 314a. That is, the sub-images 314a passing through the transmissive smooth image device 100 are projected at a first position (not shown) on the imaging plane T1, and the sub-images 314a passing through the transmissive smooth image device 100 are projected at a second position (not shown) on the imaging plane T1 for a part of the time, wherein the first position and the second position are different by a fixed distance in the horizontal direction (X-axis) or/and the vertical direction (Z-axis). In the present embodiment, the through-type smooth image device 100 can move the imaging positions of the sub-images 314a by a fixed distance in the horizontal direction or/and the vertical direction, so as to improve the horizontal resolution or/and the vertical resolution of the image. Of course, the above embodiments are merely examples, and the arrangement position and arrangement manner of the transmissive smooth image device in the optical system are not limited at all.

In the above embodiments, a glass lens is used for the first lens of the projection lens, which solves the problems of easy scratch and manufacturability due to the use of an aspherical lens. Furthermore, residual lateral chromatic aberration in the system can be reduced by the use of a cemented lens. Therefore, a projection lens design with good aberration eliminating capability, easy miniaturization and better imaging quality can be provided.

The parameters listed in tables one through ten are for illustration only and are not limiting of the invention. Although the invention has been described with reference to preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention. For example, to reduce the cost, two spherical glass lenses can be replaced by one plastic aspherical lens, so that the total lens number is reduced. Or in order to reduce the weight, two spherical lenses can be replaced by one aspherical lens, so that the total lens number is reduced. Or the lens is added to improve the resolution, so that the total lens number is increased. Or in order to reduce chromatic aberration, a lens can be replaced by a cemented lens, so that the total number of lenses is increased. The scope of the invention is therefore defined in the appended claims. Furthermore, not all of the objects, advantages, or features of the present disclosure are required to be achieved by any one embodiment or claim of the present disclosure. Furthermore, the abstract sections and headings are for use only in assisting patent document searching and are not intended to limit the scope of the claims.

Claims

1. A projection lens, comprising:

A first lens group and a second lens group which are sequentially arranged from the enlarging side to the reducing side;

The first lens group comprises 2-3 lenses, is arranged in a first lens barrel, one of the lenses is an aspheric lens, the aspheric lens is the only aspheric lens of the projection lens, and the lens closest to the amplifying side is a glass lens;

the second lens group comprises 5-6 lenses, and is arranged in a second lens cone, wherein a plurality of lenses are combined into a cemented lens; and

The diopter of the lens from the magnification side to the reduction side satisfies one of the following conditions: (1) negative, positive and positive in this order, (2) negative, positive, negative, positive and positive in this order, (3) negative, positive, negative, positive and positive in this order, (4) negative, positive, negative, and positive in that order;

L is the shortest length between the outer surfaces of the outermost lenses at the two ends of the projection lens, D1 is the radial length of the outermost turning points at the two ends of the lens at the closest magnification side, DL is the radial length of the outermost turning points at the two ends of the lens at the closest reduction side, and the projection lens meets the requirements of L/D1>2.5 and D1/DL >1.1.

2. The projection lens of claim 1, further comprising a first sleeve and a second sleeve, wherein the first sleeve material is plastic and the second sleeve material is metal.

3. The projection lens of claim 2 wherein the projection lens satisfies one of the following conditions: the projection lens further comprises a main lens barrel, wherein the main lens barrel simultaneously covers the first sleeve and the second sleeve, (3) the first sleeve and the second sleeve are not overlapped and cover, and (4) the second sleeve covers at least part of the first sleeve.

4. A projection lens, comprising:

a first lens group and a second lens group separated by the minimum position of the inner diameter of the lens barrel;

The first lens group comprises an aspheric lens and 2-3 spherical lenses, the lens closest to the magnifying side is a glass lens, and the diopter of the glass lens is negative;

the second lens group comprises 5-6 spherical lenses, and the lens comprises a cemented lens; and

L is the shortest length between the outer surfaces of the outermost lenses at the two ends of the projection lens, D1 is the maximum length between the outermost turning points at the two ends of the lens closest to the magnification side, DL is the maximum length between the outermost turning points at the two ends of the lens closest to the reduction side, and the projection lens meets L/DL >3.5 and D1/DL >1.1.

5. The projection lens of any one of claims 1, 2, 4, wherein the projection lens satisfies one of the following conditions: (1) aperture value is 1.8 or less, (2) field angle is between 45 degrees and 85 degrees, (3) EFL refers to effective focal length of projection lens, the projection lens satisfies L/EFL >6, (4) L <75mm.

6. The projection lens of any one of claims 1, 2, 4, wherein the projection lens has an optical surface shape from a magnification side to a reduction side that satisfies one of the following conditions: (1) the sequence of convex-concave, convex-convex, concave-concave, convex-concave-convex, convex-convex and convex-concave, (2) the sequence of convex-concave, convex-convex, concave-convex, convex-convex and convex-convex, (3) the sequence of convex-concave, convex-convex, concave-convex, convex-convex and convex-concave, (4) the sequence of convex-concave, convex-convex, concave-convex and convex-flat, (5) the steps of convex-concave, convex-convex, concave-convex, convex-convex and convex-concave are sequentially carried out.

7. The projection lens of any one of claims 1, 2 and 4, wherein the second lens from the enlargement side to the reduction side of the projection lens is a plastic aspherical surface, and the other lenses are glass spherical surfaces.

8. The projection lens of any one of claims 1,2, 4, wherein the projection lens satisfies one of the following conditions: the lens comprises a lens, a lens reduction side, a lens group focusing device, a lens reduction side, a lens group focusing device and a lens group focusing device.

9. The projection lens of any one of claims 1,2, 4, wherein the cemented lens is a triple cemented lens or a double cemented lens.

10. The projection lens of any of claims 1,2,4, wherein the projection lens is applied to a projection system that further comprises a light source and a light valve.