CN114114609A

CN114114609A - Projection lens

Info

Publication number: CN114114609A
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: 2022-03-01
Anticipated expiration: 2040-09-01
Also published as: CN114114609B

Abstract

A projection lens comprises a first lens group and a second lens group which are separated by a minimum inner diameter position of a projection lens barrel. The first lens group comprises an aspheric 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 the lenses comprise 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 longest length between the outermost turning points at the two ends of the lens closest to the enlargement side, DL is the longest length between the outermost turning points at the two ends of the lens closest to the reduction side, and the projection lens satisfies 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 the electro-optical technology, image devices such as projectors, digital cameras, and digital 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 to form an image, and therefore, the imaging quality is closely related to the optical quality of the optical lens. In a competitive market, manufacturers are not dedicated to improving the optical quality of the optical lens and reducing the weight, volume and manufacturing cost thereof, so as to improve the competitive advantage of the imaging device. Therefore, it is one of the important issues of those skilled in the art to manufacture a projection lens with small size, high performance, low aberration, large aperture, low cost and high resolution.

Disclosure of Invention

The present invention provides a projection lens according to an aspect, comprising a first lens group and a second lens group separated by a minimum inner diameter (aperture) position of a barrel of the projection lens. The first lens group comprises an aspheric 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 the lenses comprise 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 longest length between the outermost turning points at the two ends of the lens closest to the enlargement side, DL is the longest length between the outermost turning points at the two ends of the lens closest to the reduction side, and the projection lens satisfies L/DL >3.5 and D1/DL > 1.1.

According to another aspect of the present invention, there is provided a projection lens comprising a first lens group and a second lens group arranged in order from a magnification side to a reduction side. The first lens group comprises 2-3 lenses which are arranged in the first lens barrel, one of the lenses is an aspheric lens which is the only aspheric lens of the projection lens, and the lens closest to the amplification side is a glass lens. The second lens group comprises 5-9 lenses and is arranged in the second lens barrel, wherein a plurality of lenses are combined into a cemented lens. L is the shortest length between the outer surfaces of the outermost lenses at two ends of the projection lens, D1 is the radial length of the turning points at the outermost ends closest to the two ends of the magnification side lens, DL is the radial length of the turning points at the outermost ends closest to the two ends of the reduction side lens, 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 the glass lens, and the problems that the first lens is easily scratched and has manufacturability due to the use of the plastic aspheric lens are solved. Furthermore, the use of cemented lenses can reduce the 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 technical solutions of the present invention, and in order to make the technical means of the present invention more clearly understood, the present invention may be implemented in accordance with the content of the description, and in order to make the above and other objects, features, and advantages of the present invention more clearly understood, the following preferred embodiments are described in detail with reference to 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 diagram of a projection lens according to a second embodiment of the present invention.

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

Fig. 4 is a schematic diagram 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 an optical transfer function of the projection lens of the first embodiment of the present invention.

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

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

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

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

Detailed Description

The foregoing and other technical and scientific aspects, features and advantages of the present invention will be apparent from the following detailed description of various embodiments, which is to be read in connection with the accompanying drawings. Directional phrases used in the following embodiments, such as "upper," "lower," "front," "rear," "left," "right," etc., refer only to the orientation of the appended drawings. Accordingly, the directional terminology is used for purposes of illustration and is in no way limiting. In addition, the terms "first" and "second" used in the following embodiments are used for identifying the same or similar elements, and are not used for limiting the elements. In addition, the following embodiments are described with reference to the projection device and the display system, and those skilled in the art can apply the connection system to any required situation according to actual needs. The lens in the invention is capable of allowing at least part of light to penetrate through, and the curvature radius of at least one of the light inlet surface and the light outlet surface is not infinite; in other words, at least one of the light incident surface and the light emergent surface of the lens is not required to be a plane. For example, flat glass is not a lens of the present invention. In addition, the magnification side in the present invention is the side closer to the projection surface (for example, the projection screen) when the fixed focus lens is applied to the projection system; the reduction side is the side of the fixed-focus lens closer to the light valve when the fixed-focus lens is used in the projection system. When the zoom lens is used in an image capturing system, the zoom-in side is a side close to the object to be captured, and the zoom-out side is a side closer to the photosensitive element.

An embodiment of the invention provides a projection lens. By means of the design of the embodiment of the invention, the projection lens design which has good aberration eliminating capability, is easy to miniaturize and can provide better imaging quality can be provided.

Fig. 1 is a schematic diagram 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 lens barrel (not shown), and the lens barrel accommodates components such as a first lens group 20, an aperture 14, and a second lens group 30. The stop 14 is disposed between the first lens group 20 and the second lens group 30. That is, the projection lens 10a may include the first and

second lens groups

20 and 30 with the aperture 14 as a boundary, and a transmissive Smooth image device tsp (not shown), a prism PR (not shown), a glass protective cover CG18 and a light valve LV (not shown) may be further matched on the side of the second lens group 30 opposite to the reduction side. In this example, focusing can be achieved by moving the entire first lens group 20, aperture 14, and second lens group 30 back and forth along the optical axis 12 with respect to the imaging plane 19. 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 whole group focusing. In another embodiment, only the first lens assembly 20 or the second lens assembly 30 can be used alone to move back and forth relative to the image plane 19 for focusing, which is called group focusing. Whereas in this example the imaging plane 19 is coplanar with the surface of the light valve LV. The light valve LV in the present invention refers to an optical device for converting illumination light into image light, such as DMD, LCD, LCOS, etc., which is known to those skilled in the art. In this embodiment, 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 a positive refractive power, and the second lens group 30 has a positive refractive power. The first lens group 20 includes a lens L1, a lens L2, and a lens L3 arranged in this order from the enlargement side (OS, left side in fig. 1) to the 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 this order from the enlargement side to the reduction side along the optical axis 12. The diopters of the lenses L1-L8 are negative, positive and positive, respectively. In addition, 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 lens L1, the lens L2 and the lens L3 is positive, and the sum of the diopters of the lenses L4 to L8 is positive. The lenses L1-L8 are made of glass, plastic, glass and glass, respectively. Assuming that S is a spherical lens and ASP is an aspherical lens, lenses L1 to L8 are S, ASP, S, and S, respectively. The optical surface shapes of the lenses L1 to L8 are convex-concave, convex-convex, concave-convex, convex-concave, respectively. The image enlargement side OS and the image reduction side IS of the embodiments of the present invention are respectively disposed on the left side and the right side of the drawings, and will not be described repeatedly.

The Aperture 14 is an Aperture Stop (Aperture Stop) that is a separate component or is integrated with other optical components, and is generally the minimum position of the inner diameter of the lens barrel. In this embodiment, the aperture is similarly implemented by using a mechanism to block peripheral light and keep the middle portion transparent, and the mechanism can be adjustable. The term adjustable means adjustment of the position, shape or transparency of a machine member. Alternatively, the aperture may be coated with an opaque light-absorbing material on the surface of the lens, and the central portion of the lens is made to transmit light to limit the light path.

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

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

The design parameters of the lenses and their peripheral components of the projection lens 10a are shown in table one. However, the invention is not limited to the details given herein, and those skilled in the art who review this disclosure will readily appreciate that many modifications are possible in the details or arrangement of the features disclosed herein.

Watch 1

Moreover, the expression "in the table" means that the surface is an aspherical surface, and if not indicated, it is spherical. In each of the following design examples of the present invention, the aspheric 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 reciprocal of the radius of the osculating sphere (osculating sphere), i.e., the reciprocal of the radius of curvature near the optical axis a, k is the conic constant (conic constant), and y is the aspheric height, i.e., the height from the center of the lens to the edge of the lens. A to G represent aspherical coefficients of respective orders of the aspherical polynomial, respectively. Table II shows the aspheric coefficients and conic coefficient values of each lens surface in the lens according to the first embodiment of the present invention.

Watch two

	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

In the above-mentioned embodiments, in order to solve the problems of easy scratch, manufacturability and high cost due to the use of aspheric lenses, in this example, the first lens L1 of the front group (zooming side) and the last lens L8 of the rear group (zooming side) are glass spherical lenses, 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, since the first and the last lenses of the previous example use spherical lenses, there is a large amount of lateral chromatic aberration (lateral color) remained in the system, and therefore, the lenses L4, L5, and L6 are arranged as triple cemented lenses to reduce the residual lateral chromatic aberration in the system. That is, the lenses L4, L5, and L6 include three lenses cemented with each other. Note that, in this example, the cemented triplet is disposed between the aperture and the reduction side. The term "cemented lens" as used herein refers to a lens assembly formed by a plurality of lenses fixed to each other, but the means for fixing is not limited to adhesives. For example, in the present embodiment, the three lenses are fixed by an optical adhesive, but not limited thereto, and the three lenses can also be held and fixed by, for example, a mechanical means (e.g., a positioning groove, etc.), if necessary. In another embodiment, the triple cemented lens can also be replaced by one double cemented lens or two double cemented lenses.

In the present embodiment, the surface S18 is coplanar with the image plane 19 of the projection lens 10 a. The back focus length or BFL in the present invention is an equivalent back focus length measured by lenses L1 to L8 when all elements except lenses L1 to L8 are replaced with air, and is an air back focus length (back focus length in air) of the predetermined focal lens. In this embodiment, the second lens group 30 may have a transmissive smoothing lens TSP and a prism PR toward the reduction side, so 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 8.899 mm; TTL is about 67.167 mm; the BFL is about 13.43 mm. The small EFL characteristic of the projection lens 10a allows the projection lens to be used in a portable projector that contains a battery and does not require external power.

The design of a 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), and the lens barrel accommodates the first lens group 20, the diaphragm 14, the second lens group 30, and other elements. The stop 14 is disposed between the first lens group 20 and the second lens group 30. That is, the projection lens 10b may include the first and

second lens groups

20 and 30 with the aperture 14 as a boundary, and a transmissive Smooth image device tsp (not shown), a prism PR (not shown), a glass protective cover CG18 and a light valve LV (not shown) may be further matched on the side of the second lens group 30 opposite to the reduction side. In this example, focusing can be achieved by moving the entire first lens group 20, aperture 14, and second lens group 30 back and forth along the optical axis 12 with respect to the imaging plane 19. 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 10b is fixed. Whereas in this example the imaging plane 19 is coplanar with the surface of the light valve LV. The light valve LV in the present invention refers to an optical device for converting illumination light into image light, such as DMD, LCD, LCOS, etc., which is known to those skilled in the art. In this embodiment, 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 a positive refractive power, and the second lens group 30 has a positive refractive power. The first lens group 20 includes a lens L1, a lens L2, and a lens L3 arranged in this order from the enlargement side (OS, left side of fig. 2) to the reduction side (IS, right side of 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 this order from the enlargement side to the reduction side along the optical axis 12. The diopters of the lenses L1-L9 are negative, positive, negative, positive and positive, respectively. In addition, 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 lens L1, the lens L2 and the lens L3 is positive, and the sum of the diopters of the lenses L4 to L9 is positive. The lenses L1-L9 are made of glass, plastic, glass and glass, respectively. Assuming that S is a spherical lens and ASP is an aspherical lens, lenses L1 to L9 are S, ASP, S, and S, respectively. The optical surface shapes of the lenses L1 to L9 are convex-concave, convex-convex, concave-concave, convex-convex, and convex-convex, respectively.

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

Watch III

The fourth table shows the aspheric coefficients and the conic coefficient values of each order of each lens surface of the lens according to the second embodiment of the present invention.

Watch 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 table three and table four, one of the main differences between the second embodiment and the first embodiment is that the projection lens 10b is provided with a lens L4 between the diaphragm 14 and the cemented triplet.

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

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

Watch five

Table six shows the aspheric coefficients and conic coefficient values of each order of each lens surface of the lens in the third embodiment of the present invention.

Watch six

As can be seen from the above second table, 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 explained below. Referring to fig. 4, in this embodiment, the first lens group 20 has a positive refractive power, and the second lens group 30 has a positive refractive power. The first lens group 20 includes a lens L1, a lens L2, and a lens L3 arranged in this order from the enlargement side (OS, left side of fig. 4) to the reduction side (IS, right side of 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 this order from the enlargement side to the reduction side along the optical axis 12. The diopters of the lenses L1-L8 are negative, positive, negative and positive, respectively. In addition, 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 lens L1, the lens L2 and the lens L3 is positive, and the sum of the diopters of the lenses L4 to L8 is positive. The lenses L1-L8 are made of glass, plastic, glass and glass, respectively. Assuming that S is a spherical lens and ASP is an aspherical lens, lenses L1 to L8 are S, ASP, S, and S, respectively. 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 elements in the projection lens 10d are shown in table seven.

Watch seven

Table eight shows the aspheric coefficients and conic coefficient values of each order of each lens surface of the lens 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 above second table, the main difference between the fourth embodiment and the third embodiment is that the projection lens 10d has only one lens L8 between the cemented triplet and the image 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 a positive refractive power, and the second lens group 30 has a positive refractive power. The first lens group 20 includes a lens L1, a lens L2, and a lens L3 arranged in this order from the enlargement side (left side of OS, 5) to the reduction side (IS, right side of 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 this order from the enlargement side to the reduction side along the optical axis 12. The diopters of the lenses L1-L9 are negative, positive, negative, positive and positive, respectively. In addition, 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 lens L1, the lens L2 and the lens L3 is positive, and the sum of the diopters of the lenses L4 to L9 is positive. The lenses L1-L9 are made of glass, plastic, glass and glass, respectively. Assuming that S is a spherical lens and ASP is an aspherical lens, lenses L1 to L9 are S, ASP, S, and S, respectively. 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 lenses and their peripheral elements of the projection lens 10e are shown in table nine. However, the invention is not limited to the details given herein, and those skilled in the art who review this disclosure will readily appreciate that many modifications are possible in the details or arrangement of the features disclosed herein.

Watch nine

Table ten shows the aspheric coefficients and conic coefficient values of each order of each lens surface in the lens according to the fifth embodiment of the present invention.

Watch ten

	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 above 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 triple cemented lens and the imaging plane 19, and the diopter of the triple cemented lens is positive, negative, and positive in order, while the projection lens 10a has only two lenses L7, L8 between the triple cemented lens and the imaging plane 19, and the diopter of the triple cemented lens is negative, positive, and negative in order.

Fig. 6 to 8 are an optical transfer function graph, an optical simulation data graph of lateral chromatic aberration, and a field curvature and distortion graph of the lens 10a according to the embodiment of the present invention. Fig. 6 is a graph of the optical transfer function (MTF) plotted with the horizontal axis being the spatial frequency per cycle/mm (spatial frequency in cycles per micrometer) and the vertical axis being the modulus of the optical transfer function (module of the OTF), and in fig. 6 is a graph of simulated data made with light having a wavelength between 455 nm and 628 nm. FIG. 7 is an optical simulation data plot of simulated lateral chromatic aberration for light having wavelengths between 455 nm and 628 nm. 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 have the characteristic of good optical imaging quality.

Fig. 9 is a schematic view of a projection lens 10f assembled to a lens barrel according to another embodiment of the present invention. The projection lens includes a first lens group 20 and a second lens group 30 arranged in order from an enlargement side OS to a reduction side IS. The first lens group 20 includes 2 lenses (L1, L2) disposed 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 includes 6 lenses (L3-L8) disposed in the second barrel 30, wherein the lenses (L4, L5, L6) are combined into a cemented lens. The second sleeve 24 covers at least a portion of the first sleeve 22. In one embodiment, the first sleeve 22 may be replaced to cover at least a portion of the second sleeve 24. In one embodiment, the first sleeve and the second sleeve are not overlapped. In an embodiment, the projection lens further includes a main barrel (main barrel) that covers the first sleeve and the second sleeve simultaneously. In one embodiment, the first sleeve is made of plastic and the second sleeve is made of metal. In one embodiment, the second sleeve is made of plastic, and the first sleeve is made of metal. In one embodiment, the materials of the first sleeve and the second sleeve can be both plastics or both metals.

Fig. 10 is a schematic view of a projection lens of another embodiment of the present invention applied to a projection system. The projection system 300 comprises an illumination system 310, a light valve 320, a projection lens 330, and the transmission-type smoothing image apparatus 100. The illumination system 310 has a light source 312 adapted to provide a light beam 314, and a light valve 320 disposed on 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 314 a. 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 transmission-type smoothing image apparatus 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 path of the sub-image 314 a. In the projection system 300, the light source 312 may include, for example, a red led 312R, a green led 312G, and a blue led 312B, the color lights emitted from the leds are combined by a light combining device 316 to form a light beam 314, and the light beam 314 passes through a light integration rod 317, a lens assembly 318, and a total internal reflection Prism (TIR Prism)319 in sequence. The tir prism 319 then reflects the 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 transmission-type smooth image device 100, and are projected onto the image plane T1 through the projection lens 330. In the present embodiment, when the sub-images 314a pass through the transmission smoothing image apparatus 100, the transmission path of a part of the sub-images 314a is changed by the transmission smoothing image apparatus 100. That is, the sub-images 314a passing through the transmission-type smoothing imaging apparatus 100 are projected onto a first position (not shown) on the imaging plane T1, and the sub-images 314a passing through the transmission-type smoothing imaging apparatus 100 are projected onto a second position (not shown) on the imaging plane T1 for another part of 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, since the transmission-type smoothing imaging apparatus 100 can move the imaging positions of the sub-images 314a by a fixed distance in the horizontal direction or/and the vertical direction, the horizontal resolution or/and the vertical resolution of the image can be improved. Of course, the above embodiments are only examples, and the arrangement position and the arrangement manner of the transmission-type smoothing image device in the optical system are not limited at all.

According to the embodiment, the first lens of the projection lens is the glass lens, so that the problems that the first lens is easily scratched and has manufacturability due to the use of an aspheric lens are solved. Furthermore, the residual lateral chromatic aberration in the system can be reduced by the use of cemented lenses. 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 purposes only and are not intended to limit the invention. Although the present invention has been described with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention. For example, in order to reduce the cost, two spherical glass lenses can be replaced by a plastic aspherical lens, so that the total number of lenses is reduced. Or, in order to reduce the weight, two spherical lenses can be replaced by one aspheric lens, so that the total number of lenses is reduced. Or add lenses to improve the resolution, so as to increase the total number of lenses. 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. Therefore, the protection scope of the present invention should be determined by the appended claims. Moreover, it is not necessary for any embodiment or claim of the invention to address all of the objects, advantages, or features disclosed herein. In addition, the abstract and the title of the invention are provided for assisting the search of patent documents and are not intended to limit the scope of the invention.

Claims

1. A projection lens, comprising:

a first lens group and a second lens group arranged in order from the magnification side to the reduction side;

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

the second lens group comprises 5-9 lenses and is arranged in a second lens barrel, wherein a plurality of lenses are combined into a cemented lens;

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

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

3. The projection lens of claim 1 or 2 wherein the projection lens satisfies one of the following conditions: (1) the first sleeve covers at least part of the second sleeve, (2) the projection lens further comprises a main lens cone, and the main lens cone covers the first sleeve and the second sleeve simultaneously, (3) the first sleeve and the second sleeve are not overlapped and covered with each other, and (4) the second sleeve covers at least part of the first sleeve.

4. A projection lens, comprising:

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

the first group of lenses comprises an aspheric lens and 2-4 spherical lenses, the lens closest to the magnifying side is a glass lens, and the diopter of the glass lens is negative;

the second group of lenses comprises 4-7 spherical lenses, and the lenses comprise a cemented lens;

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

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

6. The projection lens of any one of claims 1, 2 and 4, wherein the optical surface shape of the lens from the magnification side to the reduction side satisfies one of the following conditions: (1) the material comprises (1) convex-concave, convex-convex, concave-convex, convex-concave, convex-convex in sequence, (2) convex-concave, convex-convex, convex-concave, convex-convex in sequence, (3) convex-concave, convex-convex, convex-concave, convex-convex in sequence, (4) convex-concave, convex-convex, convex-concave, convex-convex and convex-concave in sequence, and (5) convex-concave in sequence.

7. The projection lens of any one of claims 1, 2 and 4, wherein the lens diopters from the magnification side to the reduction side satisfy one of the following conditions: (1) negative, positive, negative, positive and positive in order, (2) negative, positive, negative, positive and positive in order, (3) negative, positive, negative, positive and positive in order, and (4) negative, positive, negative and positive in order.

8. The projection lens of any one of claims 1, 2 and 4, wherein the second lens of the projection lens counted from the magnification side to the reduction side is a plastic aspheric surface, and the remaining lenses are all glass spherical surfaces.

9. The projection lens of any of claims 1, 2, 4 wherein the projection lens satisfies one of the following conditions: (1) the focusing device comprises (1) whole group focusing, (2) group focusing, (3) a penetrating smooth image device arranged near the lens reduction side, and (4) a prism arranged near the lens reduction side.

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

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