CN107783258B

CN107783258B - Projection lens

Info

Publication number: CN107783258B
Application number: CN201711260269.3A
Authority: CN
Inventors: 黄林; 宋立通
Original assignee: Zhejiang Sunny Optics Co Ltd
Current assignee: Zhejiang Sunny Optics Co Ltd
Priority date: 2017-12-04
Filing date: 2017-12-04
Publication date: 2019-12-17
Anticipated expiration: 2037-12-04
Also published as: CN107783258A; CN110208928B; CN110208928A

Abstract

the application discloses projection lens, this camera lens include according to the preface by formation of image side to image source side along the optical axis: the lens includes a first lens, a second lens, a third lens and a fourth lens. The first lens has positive focal power, and the imaging side surface of the first lens is a convex surface; the second lens has positive focal power or negative focal power, and the surface of the image source side of the second lens is a convex surface; the third lens has positive focal power; and the fourth lens has positive power or negative power.

Description

Projection lens

Technical Field

The present application relates to a projection lens, and more particularly, to a projection lens including four lenses.

Background

In recent years, depth recognition technology has been rapidly developed, and a three-dimensional depth camera can obtain three-dimensional position and size information of a photographic subject, which is of great significance in application of AR (augmented reality) technology.

Coded structured light technology is one of the most important depth recognition branching technologies. The technical principle of coded structure light depth recognition is as follows: projecting the specially coded image onto a shooting object by a projection lens module; receiving the reflected pattern information by using an imaging receiving module; and processing the depth information of the shot object through a back-end algorithm. The projection lens is used as a core element of the coded structured light depth recognition technology, and directly influences the recognition range and accuracy of depth recognition.

therefore, the invention aims to provide a projection lens with large field of view and miniaturization characteristics so as to better meet the application requirements of the depth recognition projection lens.

Disclosure of Invention

The present application provides a projection lens applicable to a portable electronic product that may solve at least or partially at least one of the above-mentioned disadvantages of the related art.

In one aspect, the present application provides a projection lens, which sequentially includes, from an imaging side to an image source side along an optical axis: the lens includes a first lens, a second lens, a third lens and a fourth lens. The first lens can have positive focal power, and the imaging side surface of the first lens can be a convex surface; the second lens has positive focal power or negative focal power, and the image source side surface of the second lens can be a convex surface; the third lens may have a positive optical power; and the fourth lens has positive power or negative power.

In one embodiment, 0 < (1+ tan (CRA)) TTL/IH < 2.5 may be satisfied between the maximum incident angle CRA of the chief ray, the total optical length TTL of the projection lens, and half of the diagonal length IH of the image source region.

in one embodiment, the maximum half field angle HFOV of the projection lens may satisfy 0.9 < TAN (HFOV) < 1.2.

In one embodiment, the light transmittance of the projection lens may be greater than 85% in the light wave band of 800nm to 1000 nm.

In one embodiment, the effective focal length f1 of the first lens and the effective focal length f2 of the second lens can satisfy 2.0 < | f1/f2| < 2.8.

In one embodiment, a radius of curvature R4 of an image source side surface of the second lens and a radius of curvature R5 of an image side surface of the third lens may satisfy 0.8 < R4/R5 < 1.2.

In one embodiment, a distance SAG31 on the optical axis from an intersection point of the imaging-side surface of the third lens and the optical axis to an effective semi-aperture vertex of the imaging-side surface of the third lens and a distance SAG32 on the optical axis from an intersection point of the image-source-side surface of the third lens and the optical axis to an effective semi-aperture vertex of the image-source-side surface of the third lens may satisfy 0.3 < SAG31/SAG32 < 0.7.

In one embodiment, an effective half caliber DT11 of the image side surface of the first lens and an effective half caliber DT21 of the image source side surface of the first lens may satisfy 0.7 < DT11/DT21 < 1.0.

In one embodiment, the central thickness CT3 of the third lens element on the optical axis and the central thickness CT4 of the fourth lens element on the optical axis satisfy 1.5 < CT3/CT4 < 2.5.

In one embodiment, a separation distance T12 between the first lens and the second lens on the optical axis and a separation distance T23 between the second lens and the third lens on the optical axis may satisfy 0.4 < T12/T23 < 0.7.

In another aspect, the present application further provides a projection lens, sequentially including, from an imaging side to an image source side along an optical axis: the lens includes a first lens, a second lens, a third lens and a fourth lens. The first lens can have positive focal power, and the imaging side surface of the first lens can be a convex surface; the second lens has positive focal power or negative focal power, and the image source side surface of the second lens can be a convex surface; the third lens may have a positive optical power; and the fourth lens has positive power or negative power. The effective focal length f1 of the first lens and the effective focal length f2 of the second lens can satisfy 2.0 < | f1/f2| < 2.8.

In another aspect, the present application further provides a projection lens, sequentially from an image side to an image source side along an optical axis, comprising: the lens includes a first lens, a second lens, a third lens and a fourth lens. The first lens can have positive focal power, and the imaging side surface of the first lens can be a convex surface; the second lens has positive focal power or negative focal power, and the image source side surface of the second lens can be a convex surface; the third lens may have a positive optical power; and the fourth lens has positive power or negative power. Wherein a distance SAG31 on the optical axis from the intersection point of the imaging side surface of the third lens and the optical axis to the effective half caliber vertex of the imaging side surface of the third lens and a distance SAG32 on the optical axis from the intersection point of the image source side surface of the third lens and the optical axis to the effective half caliber vertex of the image source side surface of the third lens may satisfy 0.3 < SAG31/SAG32 < 0.7.

The projection lens has the advantages of being small in size, large in visual field, high in imaging quality, low in sensitivity, capable of meeting the requirement of depth identification and the like by reasonably distributing the focal power, the surface type, the center thickness of each lens, the on-axis distance between the lenses and the like of each lens.

Drawings

Other features, objects, and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments when taken in conjunction with the accompanying drawings. In the drawings:

Fig. 1 shows a schematic structural diagram of a projection lens according to embodiment 1 of the present application;

Fig. 2A to 2C show an axial chromatic aberration curve, an astigmatism curve, and a distortion curve, respectively, of the projection lens of embodiment 1;

Fig. 3 is a schematic structural diagram showing a projection lens according to embodiment 2 of the present application;

Fig. 4A to 4C show an axial chromatic aberration curve, an astigmatism curve, and a distortion curve, respectively, of the projection lens of embodiment 2;

Fig. 5 is a schematic structural diagram showing a projection lens according to embodiment 3 of the present application;

Fig. 6A to 6C show an axial chromatic aberration curve, an astigmatism curve, and a distortion curve, respectively, of the projection lens of embodiment 3;

Fig. 7 is a schematic structural diagram showing a projection lens according to embodiment 4 of the present application;

Fig. 8A to 8C show an axial chromatic aberration curve, an astigmatism curve, and a distortion curve, respectively, of the projection lens of embodiment 4;

fig. 9 is a schematic structural diagram showing a projection lens according to embodiment 5 of the present application;

Fig. 10A to 10C show an axial chromatic aberration curve, an astigmatism curve, and a distortion curve, respectively, of the projection lens of embodiment 5.

Detailed Description

For a better understanding of the present application, various aspects of the present application will be described in more detail with reference to the accompanying drawings. It should be understood that the detailed description is merely illustrative of exemplary embodiments of the present application and does not limit the scope of the present application in any way. Like reference numerals refer to like elements throughout the specification. The expression "and/or" includes any and all combinations of one or more of the associated listed items.

It should be noted that the expressions first, second, etc. in this specification are used only to distinguish one feature from another feature, and do not indicate any limitation on the features. Thus, the first lens discussed below may also be referred to as the second lens, and the second lens may also be referred to as the first lens, without departing from the teachings of the present application.

In the drawings, the thickness, size, and shape of the lens have been slightly exaggerated for convenience of explanation. In particular, the shapes of the spherical or aspherical surfaces shown in the drawings are shown by way of example. That is, the shape of the spherical surface or the aspherical surface is not limited to the shape of the spherical surface or the aspherical surface shown in the drawings. The figures are purely diagrammatic and not drawn to scale.

Herein, the paraxial region refers to a region near the optical axis. If the lens surface is convex and the convex position is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the concave position is not defined, it means that the lens surface is concave at least in the paraxial region. A surface closest to the image source side in each lens is referred to as an image source side surface, and a surface closest to the image forming side in each lens is referred to as an image forming side surface.

It will be further understood that the terms "comprises," "comprising," "has," "having," "includes" and/or "including," when used in this specification, specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, elements, components, and/or groups thereof. Moreover, when a statement such as "at least one of" appears after a list of listed features, the entirety of the listed features is modified rather than modifying individual elements in the list. Furthermore, when describing embodiments of the present application, the use of "may" mean "one or more embodiments of the present application. Also, the term "exemplary" is intended to refer to an example or illustration.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.

The features, principles, and other aspects of the present application are described in detail below.

A projection lens according to an exemplary embodiment of the present application may include, for example, four lenses having optical powers, i.e., a first lens, a second lens, a third lens, and a fourth lens. The four lenses are arranged in sequence from the imaging side to the image source side along the optical axis.

in an exemplary embodiment, the first lens may have a positive optical power, and an imaging-side surface thereof may be convex; the second lens has positive focal power or negative focal power, and the image source side surface of the second lens can be a convex surface; the third lens may have a positive optical power; the fourth lens has positive power or negative power.

In an exemplary embodiment, the second lens may have a positive optical power, and an imaging-side surface thereof may be concave.

In an exemplary embodiment, an image source side surface of the fourth lens may be concave.

In an exemplary embodiment, the projection lens of the present application may satisfy the conditional expression 0 < (1+ tan (CRA)) TTL/IH < 2.5, where CRA is a maximum incident angle of a chief ray, TTL is an optical total length of the projection lens, and IH is a half of a diagonal length of an image source region. The total optical length of the projection lens refers to a distance on the optical axis from the imaging side surface of the first lens to the image source surface, for example, the total optical length TTL in this application may refer to a distance on the optical axis from the imaging side surface of the first lens to the image source surface. More specifically, CRA, TTL and IH may further satisfy 2.0 < (1+ TAN (CRA)) TTL/IH < 2.5, for example, 2.12 ≦ (1+ TAN (CRA)) TTL/IH ≦ 2.31. The condition 0 < (1+ TAN (CRA)) TTL/IH < 2.5 is satisfied, a larger field angle and a shorter optical total length can be obtained, and the requirements of a large depth recognition range and miniaturization of a projection module are satisfied.

in an exemplary embodiment, the projection lens of the present application may satisfy the conditional expression 2.0 < | f1/f2| < 2.8, where f1 is an effective focal length of the first lens and f2 is an effective focal length of the second lens. More specifically, f1 and f2 can further satisfy 2.29 ≦ f1/f2| ≦ 2.63. The condition that the absolute value of f1/f2 is less than 2.8 is satisfied, and the astigmatism error of the system can be effectively eliminated, so that the image quality balance in the meridian and sagittal directions is ensured.

In an exemplary embodiment, the projection lens of the present application may satisfy the conditional expression 0.8 < R4/R5 < 1.2, where R4 is a radius of curvature of an image source-side surface of the second lens and R5 is a radius of curvature of an image-side surface of the third lens. More specifically, R4 and R5 may further satisfy 0.83. ltoreq. R4/R5. ltoreq.1.07. The conditional expression of 0.8 < R4/R5 < 1.2 is satisfied, and the field curvature aberration of the system can be effectively corrected to ensure the balance of the imaging quality of the central area and the edge area.

In an exemplary embodiment, the projection lens of the present application may satisfy the conditional expression 0.3 < SAG31/SAG32 < 0.7, where SAG31 is a distance on an optical axis from an intersection of an imaging-side surface of the third lens and the optical axis to an effective half-aperture vertex of the imaging-side surface of the third lens, and SAG32 is a distance on the optical axis from an intersection of an image-source-side surface of the third lens and the optical axis to an effective half-aperture vertex of the image-source-side surface of the third lens. More specifically, SAG31 and SAG32 may further satisfy 0.40 < SAG31/SAG32 < 0.60, for example, 0.50 ≦ SAG31/SAG32 ≦ 0.53. The conditional expression of 0.3 < SAG31/SAG32 < 0.7 is satisfied, and the spherical aberration of the system can be effectively eliminated so as to obtain a high-definition image.

In an exemplary embodiment, the projection lens of the present application may satisfy the conditional expression 0.7 < DT11/DT21 < 1.0, where DT11 is an effective half aperture of an image-side surface of the first lens and DT21 is an effective half aperture of an image-source-side surface of the first lens. More specifically, DT11 and DT21 may further satisfy 0.86 ≦ DT11/DT21 ≦ 0.95. The condition that DT11/DT21 is more than 0.7 and less than 1.0 is met, so that the total length of the short lens can be obtained, and the miniaturization requirement of the lens can be met.

In an exemplary embodiment, the projection lens of the present application may satisfy the conditional expression 1.5 < CT3/CT4 < 2.5, where CT3 is a central thickness of the third lens on the optical axis, and CT4 is a central thickness of the fourth lens on the optical axis. More specifically, CT3 and CT4 further satisfy 1.64 ≦ CT3/CT4 ≦ 2.43. The condition that the CT3/CT4 is more than 2.5 is satisfied, so that a larger field angle is obtained, and higher imaging quality is ensured.

In an exemplary embodiment, the projection lens of the present application may satisfy the conditional expression 0.4 < T12/T23 < 0.7, where T12 is a separation distance of the first lens and the second lens on the optical axis, and T23 is a separation distance of the second lens and the third lens on the optical axis. More specifically, T12 and T23 may further satisfy 0.56 ≦ T12/T23 ≦ 0.62. The conditional expression of 0.4 < T12/T23 < 0.7 is satisfied, so that tolerance sensitivity of the lens is reduced, and the requirement of the lens machinability is satisfied.

In an exemplary embodiment, the projection lens of the present application has a light transmittance of greater than 85% in a light wavelength band of about 800nm to about 1000 nm. The arrangement is favorable for obtaining a high-brightness projection picture and reducing the diaphragm requirement on the projection lens.

in an exemplary embodiment, the projection lens of the present application may satisfy the conditional expression 0.9 < tan (HFOV) < 1.2, where HFOV is the maximum half field angle of the projection lens. More specifically, the HFOV further can satisfy 0.95 ≦ TAN (HFOV) ≦ 1.04. The requirement of the range of the depth identification area can be met and the higher identification precision can be kept when the conditional expression of 0.9 < TAN (HFOV) < 1.2 is met.

In an exemplary embodiment, the projection lens may further include at least one diaphragm to improve the imaging quality of the lens. The stop may be disposed at any position as needed, for example, the stop may be disposed between the imaging side and the first lens.

Alternatively, the projection lens may further include other well-known optical projection elements, such as a prism, a field lens, and the like.

Compared with a common lens, the projection lens is mainly different in that light rays of the common imaging lens form an image plane from an object side to an imaging side; in general, light from a projection lens projects an image surface to a projection surface in an enlarged manner from an image source side to an image side. The light input of a projection lens is generally controlled by the object numerical aperture and the lens stop.

The projection lens according to the above-mentioned embodiment of the present application may employ, for example, four lenses, so that the projection lens has at least one advantageous effect of miniaturization, a large field of view, low sensitivity, high imaging quality, capability of satisfying depth recognition requirements, and the like by reasonably distributing the power of each lens, the surface type, the center thickness of each lens, the on-axis distance between each lens, and the like.

In the embodiment of the present application, at least one of the mirror surfaces of each lens is an aspherical mirror surface. The aspheric lens is characterized in that: the curvature varies continuously from the center of the lens to the periphery of the lens. Unlike a spherical lens having a constant curvature from the center of the lens to the periphery of the lens, an aspherical lens has better curvature radius characteristics, and has advantages of improving distortion aberration and improving astigmatic aberration. After the aspheric lens is adopted, the aberration generated during imaging can be eliminated as much as possible, thereby improving the imaging quality.

However, it will be appreciated by those skilled in the art that the number of lenses making up the projection lens can be varied to achieve the various results and advantages described in this specification without departing from the claimed subject matter. For example, although four lenses are exemplified in the embodiments, the projection lens is not limited to include four lenses. The projection lens may also include other numbers of lenses, if desired.

specific examples of the projection lens applicable to the above-described embodiments are further described below with reference to the drawings.

Example 1

A projection lens according to embodiment 1 of the present application is described below with reference to fig. 1 to 2C. Fig. 1 shows a schematic structural diagram of a projection lens according to embodiment 1 of the present application.

As shown in fig. 1, a projection lens according to an exemplary embodiment of the present application sequentially includes, from an image side to an image source side along an optical axis: stop STO, first lens E1, second lens E2, third lens E3, and fourth lens E4.

The first lens E1 has positive power, and its image-side surface S1 is convex and its image-source-side surface S2 is concave; the second lens E2 has positive power, and has a concave image-side surface S3 and a convex image-source-side surface S4; the third lens E3 has positive power, and has a concave image-side surface S5 and a convex image-source-side surface S6; and the fourth lens E4 has negative power, and its image-side surface S7 is convex and its image-source-side surface S8 is concave. S9 may be an image source plane, and light from the image source plane of the projection lens passes through the respective surfaces S8 to S1 in order and is finally imaged on a screen (not shown).

The light transmittance of the projection lens is more than 85% in the light wave band of about 800nm to about 1000 nm.

Table 1 shows the surface type, radius of curvature, thickness, material, and conic coefficient of each lens of the projection lens of example 1, wherein the unit of the radius of curvature and the thickness are both millimeters (mm).

TABLE 1

As can be seen from table 1, the image-side surface and the image-source-side surface of any one of the first lens E1 to the fourth lens E4 are aspheric. In the present embodiment, the profile x of each aspheric lens can be defined using, but not limited to, the following aspheric formula:

Wherein x is the rise of the distance from the aspheric surface vertex to the aspheric surface vertex when the aspheric surface is at the position with the height of h along the optical axis direction; c is the paraxial curvature of the aspheric surface, c being 1/R (i.e., paraxial curvature c is the inverse of radius of curvature R in table 1 above); k is the conic coefficient (given in table 1); ai is the correction coefficient of the i-th order of the aspherical surface. Table 2 below shows the high-order coefficient A of each of the aspherical mirror surfaces S1 to S8 used in example 1₄、A₆、A₈、A₁₀、A₁₂、A₁₄And A₁₆。

Flour mark

A4

A6

A8

A10

A12

A14

A16

S1

1.5615E-01

-4.1916E+00

1.0055E+02

-1.0841E+03

5.7844E+03

-1.4246E+04

1.2976E+04

S2

4.9464E-01

6.9931E-01

1.4940E+01

-1.8713E+02

1.8504E+03

-8.8115E+03

1.9038E+04

S3

-4.1066E-01

-2.8918E+01

5.3999E+02

-5.5399E+03

2.9869E+04

-8.1639E+04

9.0669E+04

S4

-2.8917E-01

7.5873E+00

-9.6838E+01

6.3678E+02

-2.2453E+03

3.9455E+03

-2.6261E+03

S5

-3.7771E-01

-1.0334E+00

6.5029E+00

-1.0025E+01

7.1543E+00

-2.4772E+00

3.3604E-01

S6

-1.1253E+00

4.5667E+00

-1.0239E+01

1.3167E+01

-8.9996E+00

3.0492E+00

-4.0198E-01

S7

-1.5132E+00

1.9426E+00

-9.7812E-01

6.1994E-02

1.5356E-01

-6.4488E-02

8.2865E-03

S8

-4.8483E-01

3.1658E-02

3.9269E-01

-4.0333E-01

1.9364E-01

-4.5723E-02

4.1905E-03

TABLE 2

table 3 gives the total optical length TTL (i.e., the distance on the optical axis from the imaging-side surface S1 of the first lens E1 to the image source surface S9), the maximum half field angle HFOV, the total effective focal length f, and the effective focal lengths f1 to f4 of the respective lenses in the projection lens in embodiment 1.

TABLE 3

The projection lens in embodiment 1 satisfies:

(1+ tan (CRA)) TTL/IH of 2.12, where CRA is the maximum incident angle of the chief ray, TTL is the total optical length of the projection lens, and IH is half the diagonal length of the image source region;

I f1/f2| -2.43, where f1 is the effective focal length of the first lens E1 and f2 is the effective focal length of the second lens E2;

R4/R5 is 0.98, where R4 is a radius of curvature of the image source-side surface S4 of the second lens E2, and R5 is a radius of curvature of the image-side surface S5 of the third lens E3;

SAG31/SAG32 is 0.50, wherein SAG31 is a distance on the optical axis from the intersection point of the imaging side surface S5 of the third lens E3 and the optical axis to the effective half-aperture vertex of the imaging side surface S5 of the third lens E3, and SAG32 is a distance on the optical axis from the intersection point of the image source side surface S6 of the third lens E3 and the optical axis to the effective half-aperture vertex of the image source side surface S6 of the third lens E3;

DT11/DT21 is 0.89, where DT11 is the effective half aperture of the image-side surface S1 of the first lens E1, and DT21 is the effective half aperture of the image-source-side surface S2 of the first lens E1;

CT3/CT4 is 1.94, where CT3 is the central thickness of the third lens E3 on the optical axis, and CT4 is the central thickness of the fourth lens E4 on the optical axis;

T12/T23 is 0.56, where T12 is the distance between the first lens E1 and the second lens E2 on the optical axis, and T23 is the distance between the second lens E2 and the third lens E3 on the optical axis;

Tan (HFOV) ═ 1.04, where HFOV is the maximum half field angle of the projection lens.

Fig. 2A shows an on-axis chromatic aberration curve of the projection lens of embodiment 1, which represents the deviation of the convergent focus of light rays of different wavelengths after passing through the lens. Fig. 2B shows an astigmatism curve representing a meridional field curvature and a sagittal field curvature of the projection lens of embodiment 1. Fig. 2C shows a distortion curve of the projection lens of embodiment 1, which represents the distortion magnitude values in the case of different viewing angles. As can be seen from fig. 2A to 2C, the projection lens according to embodiment 1 can achieve good imaging quality.

Example 2

a projection lens according to embodiment 2 of the present application is described below with reference to fig. 3 to 4C. In this embodiment and the following embodiments, descriptions of parts similar to those of embodiment 1 will be omitted for the sake of brevity. Fig. 3 is a schematic structural diagram showing a projection lens according to embodiment 2 of the present application.

As shown in fig. 3, a projection lens according to an exemplary embodiment of the present application sequentially includes, from an image side to an image source side along an optical axis: stop STO, first lens E1, second lens E2, third lens E3, and fourth lens E4.

Table 4 shows the surface type, radius of curvature, thickness, material, and conic coefficient of each lens of the projection lens of example 2, wherein the unit of the radius of curvature and the thickness are both millimeters (mm).

TABLE 4

As is clear from table 4, in embodiment 2, the image-side surface and the image-source-side surface of any one of the first lens E1 to the fourth lens E4 are both aspherical. Table 5 shows high-order term coefficients that can be used for each aspherical mirror surface in example 2, wherein each aspherical mirror surface type can be defined by formula (1) given in example 1 above.

TABLE 5

Table 6 shows the total optical length TTL, the maximum half field angle HFOV, the total effective focal length f, and the effective focal lengths f1 to f4 of the projection lens in embodiment 2.

TABLE 6

Fig. 4A shows an on-axis chromatic aberration curve of the projection lens of embodiment 2, which represents the deviation of the convergent focus of light rays of different wavelengths after passing through the lens. Fig. 4B shows an astigmatism curve representing a meridional field curvature and a sagittal field curvature of the projection lens of embodiment 2. Fig. 4C shows a distortion curve of the projection lens of embodiment 2, which represents the distortion magnitude values in the case of different viewing angles. As can be seen from fig. 4A to 4C, the projection lens according to embodiment 2 can achieve good imaging quality.

Example 3

A projection lens according to embodiment 3 of the present application is described below with reference to fig. 5 to 6C. Fig. 5 is a schematic structural diagram showing a projection lens according to embodiment 3 of the present application.

As shown in fig. 5, a projection lens according to an exemplary embodiment of the present application sequentially includes, from an image side to an image source side along an optical axis: stop STO, first lens E1, second lens E2, third lens E3, and fourth lens E4.

The first lens E1 has positive power, and its image-side surface S1 is convex and its image-source-side surface S2 is concave; the second lens E2 has positive power, and has a concave image-side surface S3 and a convex image-source-side surface S4; the third lens E3 has positive power, and has a concave image-side surface S5 and a convex image-source-side surface S6; and the fourth lens E4 has negative power, and its image-side surface S7 is concave and its image-source-side surface S8 is concave. S9 may be an image source plane, and light from the image source plane of the projection lens passes through the respective surfaces S8 to S1 in order and is finally imaged on a screen (not shown).

Table 7 shows the surface type, radius of curvature, thickness, material, and conic coefficient of each lens of the projection lens of example 3, wherein the unit of the radius of curvature and the thickness are both millimeters (mm).

TABLE 7

As is apparent from table 7, in embodiment 3, the image-side surface and the image-source-side surface of any one of the first lens E1 to the fourth lens E4 are both aspherical. Table 5 shows high-order term coefficients that can be used for each aspherical mirror surface in example 2, wherein each aspherical mirror surface type can be defined by formula (1) given in example 1 above.

Flour mark

A4

A6

A8

A10

A12

A14

A16

S1

3.6418E-01

-4.2484E+00

1.7253E+02

-7.6872E+02

-1.3616E+04

1.5380E+05

-4.3657E+05

S2

2.7243E-01

3.4752E+00

-6.0200E+01

6.5103E+02

-1.5180E+03

-1.2495E+03

0.0000E+00

S3

-5.1748E-01

-2.9525E+01

5.3533E+02

-5.5151E+03

3.0152E+04

-7.9913E+04

9.7487E+04

S4

-2.1095E-01

7.5296E+00

-9.7206E+01

6.3590E+02

-2.2444E+03

3.9587E+03

-2.6054E+03

S5

-2.7582E-01

-1.0365E+00

6.4469E+00

-1.0020E+01

7.1576E+00

-2.4712E+00

3.4350E-01

S6

-1.0491E+00

4.4781E+00

-1.0164E+01

1.3186E+01

-9.0173E+00

3.0361E+00

-3.9036E-01

S7

-1.4776E+00

1.9597E+00

-9.8528E-01

6.4358E-02

1.5180E-01

-6.3891E-02

8.2018E-03

S8

-4.8982E-01

2.9768E-02

4.0658E-01

-4.0842E-01

1.9888E-01

-4.8349E-02

4.3821E-03

TABLE 8

Table 9 gives the total optical length TTL, the maximum half field angle HFOV, the total effective focal length f, and the effective focal lengths f1 to f4 of the respective lenses of the projection lens in embodiment 3.

TABLE 9

Fig. 6A shows an on-axis chromatic aberration curve of the projection lens of embodiment 3, which represents the deviation of the convergent focus of light rays of different wavelengths after passing through the lens. Fig. 6B shows an astigmatism curve representing a meridional field curvature and a sagittal field curvature of the projection lens of embodiment 3. Fig. 6C shows a distortion curve of the projection lens of embodiment 3, which represents the distortion magnitude values in the case of different viewing angles. As can be seen from fig. 6A to 6C, the projection lens according to embodiment 3 can achieve good imaging quality.

Example 4

a projection lens according to embodiment 4 of the present application is described below with reference to fig. 7 to 8C. Fig. 7 is a schematic structural diagram showing a projection lens according to embodiment 4 of the present application.

As shown in fig. 7, a projection lens according to an exemplary embodiment of the present application sequentially includes, from an image side to an image source side along an optical axis: stop STO, first lens E1, second lens E2, third lens E3, and fourth lens E4.

Table 10 shows the surface type, radius of curvature, thickness, material, and conic coefficient of each lens of the projection lens of example 4, wherein the unit of the radius of curvature and the thickness are both millimeters (mm).

Watch 10

As can be seen from table 10, in embodiment 4, the image-side surface and the image-source-side surface of any one of the first lens E1 to the fourth lens E4 are both aspherical. Table 11 shows high-order term coefficients that can be used for each aspherical mirror surface in embodiment 4, wherein each aspherical mirror surface type can be defined by the formula (1) given in embodiment 1 above.

Flour mark

A4

A6

A8

A10

A12

A14

A16

S1

5.3149E-01

-8.3884E+00

1.7885E+02

-7.5712E+02

-1.3476E+04

1.5316E+05

-4.4688E+05

S2

3.6122E-02

5.7148E+00

-8.0089E+01

5.7882E+02

-1.6399E+03

3.7888E+02

0.0000E+00

S3

-3.1367E-01

-2.8910E+01

5.4553E+02

-5.5178E+03

2.9882E+04

-8.1978E+04

8.7675E+04

S4

-9.0248E-02

7.2188E+00

-9.6116E+01

6.3941E+02

-2.2421E+03

3.9436E+03

-2.6396E+03

S5

-3.7940E-01

-1.0355E+00

6.5031E+00

-1.0026E+01

7.1514E+00

-2.4784E+00

3.3924E-01

S6

-1.1388E+00

4.5679E+00

-1.0241E+01

1.3165E+01

-9.0009E+00

3.0484E+00

-4.0259E-01

S7

-1.5062E+00

1.9490E+00

-9.7977E-01

6.5003E-02

1.5082E-01

-6.3256E-02

8.1176E-03

S8

-4.9308E-01

2.9134E-02

4.0407E-01

-4.0863E-01

1.9907E-01

-4.8110E-02

4.5562E-03

TABLE 11

Table 12 gives the total optical length TTL, the maximum half field angle HFOV, the total effective focal length f, and the effective focal lengths f1 to f4 of the respective lenses of the projection lens in embodiment 4.

TABLE 12

Fig. 8A shows an on-axis chromatic aberration curve of the projection lens of embodiment 4, which represents the deviation of the convergent focus of light rays of different wavelengths after passing through the lens. Fig. 8B shows an astigmatism curve representing a meridional field curvature and a sagittal field curvature of the projection lens of embodiment 4. Fig. 8C shows a distortion curve of the projection lens of embodiment 4, which represents the distortion magnitude values in the case of different viewing angles. As can be seen from fig. 8A to 8C, the projection lens according to embodiment 4 can achieve good imaging quality.

Example 5

a projection lens according to embodiment 5 of the present application is described below with reference to fig. 9 to 10C. Fig. 9 is a schematic structural diagram showing a projection lens according to embodiment 5 of the present application.

as shown in fig. 9, a projection lens according to an exemplary embodiment of the present application sequentially includes, from an image side to an image source side along an optical axis: stop STO, first lens E1, second lens E2, third lens E3, and fourth lens E4.

the first lens E1 has positive power, and its image-side surface S1 is convex and its image-source-side surface S2 is concave; the second lens E2 has positive power, and has a concave image-side surface S3 and a convex image-source-side surface S4; the third lens E3 has positive power, and has a concave image-side surface S5 and a convex image-source-side surface S6; and the fourth lens E4 has positive power, and its image-side surface S7 is convex and its image-source-side surface S8 is concave. S9 may be an image source plane, and light from the image source plane of the projection lens passes through the respective surfaces S8 to S1 in order and is finally imaged on a screen (not shown).

Table 13 shows the surface type, radius of curvature, thickness, material, and conic coefficient of each lens of the projection lens of example 5, wherein the unit of the radius of curvature and the thickness are both millimeters (mm).

Watch 13

as is clear from table 13, in embodiment 5, the image-side surface and the image-source-side surface of any one of the first lens E1 to the fourth lens E4 are both aspherical. Table 14 shows high-order term coefficients that can be used for each aspherical mirror surface in example 5, wherein each aspherical mirror surface type can be defined by formula (1) given in example 1 above.

flour mark

A4

A6

A8

A10

A12

A14

A16

S1

5.0519E-01

-8.6079E+00

1.8062E+02

-7.2450E+02

-1.3482E+04

1.5082E+05

-4.3927E+05

S2

-9.8834E-03

5.8792E+00

-7.5804E+01

5.7759E+02

-1.9467E+03

2.1590E+03

0.0000E+00

S3

-3.1328E-01

-2.9784E+01

5.4264E+02

-5.5215E+03

2.9905E+04

-8.1677E+04

9.0278E+04

S4

-9.1581E-02

7.0852E+00

-9.6316E+01

6.3912E+02

-2.2428E+03

3.9412E+03

-2.6493E+03

S5

-3.7945E-01

-1.0358E+00

6.5023E+00

-1.0028E+01

7.1498E+00

-2.4795E+00

3.4191E-01

S6

-1.1307E+00

4.5723E+00

-1.0240E+01

1.3165E+01

-9.0007E+00

3.0486E+00

-4.0225E-01

S7

-1.5099E+00

1.9490E+00

-9.7984E-01

6.4954E-02

1.5081E-01

-6.3254E-02

8.1228E-03

S8

-4.8520E-01

2.9035E-02

4.0341E-01

-4.0887E-01

1.9901E-01

-4.8124E-02

4.5537E-03

TABLE 14

Table 15 gives the total optical length TTL, the maximum half field angle HFOV, the total effective focal length f, and the effective focal lengths f1 to f4 of the respective lenses of the projection lens in embodiment 5.

watch 15

Fig. 10A shows an on-axis chromatic aberration curve of the projection lens of embodiment 5, which represents the deviation of the convergent focus of light rays of different wavelengths after passing through the lens. Fig. 10B shows an astigmatism curve representing a meridional field curvature and a sagittal field curvature of the projection lens of embodiment 5. Fig. 10C shows a distortion curve of the projection lens of embodiment 5, which represents the distortion magnitude values in the case of different angles of view. As can be seen from fig. 10A to 10C, the projection lens according to embodiment 5 can achieve good imaging quality.

In summary, examples 1 to 5 satisfy the relationship shown in table 16, respectively.

TABLE 16

The above description is only a preferred embodiment of the application and is illustrative of the principles of the technology employed. It will be appreciated by a person skilled in the art that the scope of the invention as referred to in the present application is not limited to the embodiments with a specific combination of the above-mentioned features, but also covers other embodiments with any combination of the above-mentioned features or their equivalents without departing from the inventive concept. For example, the above features may be replaced with (but not limited to) features having similar functions disclosed in the present application.

Claims

1. a projection lens in which four lenses having refractive power are provided, and a first lens, a second lens, a third lens and a fourth lens are provided, the first lens to the fourth lens being arranged in order from an image side to an image source side along an optical axis,

The first lens has positive focal power, and the imaging side surface of the first lens is a convex surface;

The second lens has positive focal power or negative focal power, and the surface of the image source side of the second lens is a convex surface;

the third lens has positive optical power;

The fourth lens has positive focal power or negative focal power;

at least one of an image-side surface of the first lens to an image-source-side surface of the fourth lens is an aspherical mirror surface; and

Wherein the effective focal length f1 of the first lens and the effective focal length f2 of the second lens satisfy 2.0 < | f1/f2| < 2.8.

2. The projection lens of claim 1, wherein a radius of curvature R4 of an image source side surface of the second lens and a radius of curvature R5 of an image side surface of the third lens satisfy 0.8 < R4/R5 < 1.2.

3. the projection lens of claim 1, wherein 0.3 < SAG31/SAG32 < 0.7 is satisfied,

SAG31 is the distance between the intersection point of the imaging side surface of the third lens and the optical axis and the effective semi-aperture vertex of the imaging side surface of the third lens on the optical axis, and SAG32 is the distance between the intersection point of the image source side surface of the third lens and the optical axis and the effective semi-aperture vertex of the image source side surface of the third lens on the optical axis.

4. The projection lens of claim 1, wherein an effective half-aperture DT11 of the imaging-side surface of the first lens and an effective half-aperture DT21 of the image-source-side surface of the first lens satisfy 0.7 < DT11/DT21 < 1.0.

5. The projection lens of claim 1, wherein the central thickness CT3 of the third lens element on the optical axis and the central thickness CT4 of the fourth lens element on the optical axis satisfy 1.5 < CT3/CT4 < 2.5.

6. the projection lens of claim 1 wherein the separation distance T12 on the optical axis between the first lens and the second lens and the separation distance T23 on the optical axis between the second lens and the third lens satisfy 0.4 < T12/T23 < 0.7.

7. The projection lens of any of claims 2 to 6 wherein 0 < (1+ TAN (CRA)) TTL/IH < 2.5 is satisfied,

The CRA is a maximum incident angle of a chief ray, the TTL is an optical total length of the projection lens, and the IH is a half of a diagonal length of the image source region.

8. the projection lens according to any of claims 2 to 6, characterized in that the maximum half field angle HFOV of the projection lens satisfies 0.9 < TAN (HFOV) < 1.2.

9. The projection lens according to any of claims 2 to 6, characterized in that the light transmittance of the projection lens is greater than 85% in the light wave band of 800nm to 1000 nm.