WO2022032920A1

WO2022032920A1 - Projection lens

Info

Publication number: WO2022032920A1
Application number: PCT/CN2020/130542
Authority: WO
Inventors: 杜向丽; 彭思龙; 汪雪林; 顾庆毅
Original assignee: 苏州中科全象智能科技有限公司
Priority date: 2020-08-11
Filing date: 2020-11-20
Publication date: 2022-02-17
Also published as: CN111897094A; CN111897094B

Abstract

A projecting lens, comprising a first lens (1), a second lens (2), a third lens (3), a fourth lens (5), a fifth lens (6), a sixth lens (7), and a seventh lens (8) sequentially provided along an optical axis from an image projecting surface (12) to an image source surface (11). The first lens (1) has a positive focal power. The second lens (2) has a positive focal power. The third lens (3) has a negative focal power. The fourth lens (5) has a positive focal power. The fifth lens (6) has a negative focal power. The sixth lens (7) has a positive focal power. The seventh lens (8) has a positive focal power. An aperture (4) is provided between the third lens (3) and the fourth lens (5).

Description

projection lens

This disclosure claims the priority of a Chinese patent application with application number 202010801870.4 filed with the China Patent Office on August 11, 2020, the entire contents of which are incorporated into this disclosure by reference.

technical field

The present application relates to the technical field of photoelectric projection, for example, to a projection lens.

Background technique

3D structured light is a popular research direction for stereo vision image processing applications in recent years. Different from binocular stereo vision and TOF (time of flight), 3D structured light camera is a non-contact measuring instrument based on structured light measurement method. The camera device records the sequence of structured light images, and uses a specific algorithm to obtain the three-dimensional data of the measured object. It can be seen that the projection lens is an important part of the 3D structured light camera, and the projection resolution and distortion will greatly affect the accuracy of 3D reconstruction, especially for the accuracy of measurement and detection.

With the development of 3D structured light cameras, projection lenses in related technologies can no longer meet industrial needs such as high-precision measurement and detection. The projection lens in the related art has large distortion, which is about 1%, and the accuracy is low for 3D point cloud reconstruction. Therefore, it is necessary to provide a lens with high resolution, low distortion and small aberration to meet the requirements of 3D structured light. Cameras are used for high-precision measurement and inspection needs. Research on this issue has gradually become a trend.

In Chinese patent document CN111239977A, a low-distortion industrial projection lens is disclosed. The projection lens includes a diaphragm, a lens with positive refractive power and a lens with negative refractive power, along the optical axis from the projection side to the display chip side The first lens to the ninth lens are respectively provided, which are the first lens with positive refractive power, the second lens with negative refractive power, the third lens with negative refractive power, the fourth lens with negative refractive power, the positive light The fifth lens with negative power, the sixth lens with negative power, the seventh lens with positive power, the eighth lens with positive power, and the ninth lens with positive power; the diaphragm is located between the third lens and the first lens. between the four lenses. The focal length of the first lens is 21mm<f1<28mm, the focal length of the second lens is -51mm<f2<-42mm, the focal length of the third lens is -195mm<f3<-110mm, and the focal length of the fourth lens is -55mm<f4 <-32mm, the focal length of the fifth lens is 23mm<f5<35mm, the focal length of the sixth lens is -10mm<f6<-6mm, the focal length of the seventh lens is 20mm<f7<25mm, the focal length of the eighth lens is 14mm< f8<18mm, the focal length of the ninth lens is 52mm<f9<63mm. This solution adopts a 9-piece lens structure, which is relatively complex in design and high in cost.

In Chinese patent document CN104991329A, a high-resolution projection lens for an industrial 3D scanning system is disclosed, which is mainly composed of an optical lens group, an iris assembly, a prism and a chip. The optical lens group extends from the object side to the The image side is provided with a first lens with positive power, a second lens with negative power, a third lens with negative power, a fourth lens with negative power, and a lens with negative power. A cemented lens composed of a fifth lens and a sixth lens with positive refractive power, a seventh lens with positive refractive power, and an eighth lens with positive refractive power, the iris assembly is provided on the fourth lens and the Between the fifth lenses, the prism is arranged between the eighth lens and the chip; the first lens is a biconvex lens, and the second lens is a meniscus positive lens with a concave surface facing the image plane , the third lens is a meniscus negative lens with a concave surface facing the image surface, the fourth lens is a meniscus negative lens with a concave surface facing the image surface, the fifth lens is a biconcave lens, and the sixth lens is A biconvex lens, the seventh lens is a biconvex lens, and the eighth lens is a biconvex lens; the air space between the first lens and the second lens is between 0.1 mm and 1 mm, and the second lens and The air space between the third lens is between 0.5mm and 1.5mm, the air space between the third lens and the fourth lens is between 2mm and 4mm, the fourth lens and the iris diaphragm The air space between the components is between 7mm and 9mm, the air space between the iris assembly and the fifth lens is between 2mm and 4mm, and the air space between the sixth lens and the seventh lens is between 2mm and 4mm. The air space is between 12mm and 14mm, the air space between the seventh lens and the eighth lens is between 4mm and 6mm, and the air space between the eighth lens and the prism is between 6mm and 8mm The focal length of the first lens is between 35mm and 45mm, the focal length of the second lens is between 25mm and 35mm, and the focal length of the third lens is between -5mm and -15mm, so The focal length of the fourth lens is between -25mm and -35mm, the focal length of the cemented lens is between 35mm and 45mm, the focal length of the seventh lens is between 55mm and 75mm, and the eighth lens The focal length is between 45mm and 55mm. The invention has high distortion and large aberration, and adopts double cemented lens at the same time, which has large volume and high cost.

The related technologies have at least the following deficiencies:

1. The lens field curvature of the comparison file 2 is less than 0.1mm, and the accuracy is not enough.

2. Although the image quality of the lens in Comparative Document 1 is better, the number of lenses is relatively large, the lens design is relatively complex, and the cost is also high.

3. The lens aberration of the comparison file 2 is relatively large, the distortion is large, and the spot size is also large, which is larger than the imaging DMD pixel, which will waste energy.

SUMMARY OF THE INVENTION

The present application provides a projection lens capable of achieving high resolution and low distortion.

The present application provides a projection lens, including:

a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens arranged in sequence from the projection surface to the image source surface along the optical axis;

The first lens has a positive refractive power; the second lens has a positive refractive power; the third lens has a negative refractive power; the fourth lens has a positive refractive power; the fifth lens has a negative refractive power degree; the sixth lens has positive refractive power; the seventh lens has positive refractive power.

Description of drawings

1 is a structural diagram of a projection lens of the present application;

Fig. 2 is the structure diagram of the WD=80mm projection lens of the present application;

Fig. 3 is the structure diagram of the WD=190mm projection lens of the present application;

Fig. 4 is the structure diagram of the WD=350mm projection lens of the present application;

Fig. 5 is the imaging quality MTF curve diagram of the WD=80mm projection lens of the present application;

Fig. 6 is the field curvature diagram of the WD=80mm projection lens of the present application;

Fig. 7 is the distortion curve diagram of the WD=80mm projection lens of the present application;

Fig. 8 is the axial aberration curve diagram of the WD=80mm projection lens of the present application;

Fig. 9 is the imaging quality MTF curve diagram of the WD=190mm projection lens of the present application;

Fig. 10 is the field curvature diagram of the WD=190mm projection lens of the present application;

Fig. 11 is the distortion curve diagram of the WD=190mm projection lens of the present application;

Fig. 12 is the axial aberration curve diagram of the WD=190mm projection lens of the present application;

Fig. 13 is the imaging quality MTF curve diagram of the WD=350mm projection lens of the present application;

14 is a field curvature diagram of the WD=350mm projection lens of the present application;

Fig. 15 is the distortion curve diagram of the WD=350mm projection lens of the present application;

Fig. 16 is the axial aberration curve diagram of the WD=350mm projection lens of the present application;

The figures are marked as: 1, the first lens; 2, the second lens; 3, the third lens; 4, the diaphragm; 5, the fourth lens; 6, the fifth lens; 7, the sixth lens; 8, the first lens Seven lenses; 9. Prism; 10. Protective glass; 11. Image source surface; 12. Projection surface.

detailed description

The specific embodiments of the present application will be described below with reference to the accompanying drawings 1-16.

The present application provides a high-resolution low-distortion projection lens, including:

a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens;

The positional relationship of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens is:

The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seven lenses; the projection surface is used to display the projected image; the image source surface is used to display the image to be projected;

The first lens helps to eliminate spherical aberration and axial chromatic aberration; the second lens helps to eliminate spherical aberration and coma, the third lens helps to eliminate astigmatism, the fourth lens and all The fifth lens helps to eliminate field curvature and axial chromatic aberration, and the sixth lens and the seventh lens help to eliminate field curvature and magnification chromatic aberration.

Since the projection lens has reasonable positive and negative refractive power, a projection lens with ultra-high resolution, small aberration and distortion less than 0.01% can be designed with a working distance (hereinafter referred to as WD) of 0-350mm.

As an optional implementation manner, the projection lens further includes a diaphragm, and the diaphragm is located between the third lens and the fourth lens to help eliminate astigmatism, distortion and chromatic aberration of magnification.

As an optional implementation manner, the air space between the first lens and the second lens is in the range of 0.2-0.7 mm, the air space between the second lens and the third lens is in the range of 1.2-1.6 mm, and the third lens and the diaphragm are in the range of 1.2-1.6 mm. The air space between the diaphragm and the fourth lens is in the range of 4.9-5.3mm, the air space between the diaphragm and the fourth lens is in the range of 6-6.3mm, the air space between the fourth lens and the fifth lens is in the range of 0.9-1.2mm, and the fifth lens and the fifth lens are in the range of 0.9-1.2mm. The air interval between the sixth lens is 0.7-0.9 mm, the air interval between the sixth lens and the seventh lens is 0.2-0.4 mm, and the air interval between the seventh lens and the prism is 6-9 mm.

As an optional implementation:

The focal length of the first lens is between 41mm and 46mm;

the focal length of the second lens is between 55mm and 73mm;

The focal length of the third lens is between -14mm and -11mm;

the focal length of the fourth lens is between 115mm and 134mm;

The focal length of the fifth lens is between -30mm and -26mm;

The focal length of the sixth lens is between 23mm and 28mm;

The focal length of the seventh lens is between 16mm and 21mm.

As an optional implementation manner, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are all spherical surfaces lens.

As an optional implementation manner, the lenses of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are all For glass lenses.

As an optional embodiment, the working wavelength of the high-resolution low-distortion projection lens is between 444 nm and 465 nm.

As an optional implementation manner, the refractive indices of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are They are: 1.87, 1.876, 1.911, 1.873, 1.826, 1.86 and 1.917.

As an optional implementation manner, the refractive indices of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are They are: 1.869, 1.861, 1.913, 1.743, 1.863, 1.76 and 1.907.

As an optional implementation manner, the refractive indices of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are They are: 1.856, 1.854, 1.915, 1.69, 1.864, 1.763 and 1.91.

Example 1

According to a specific embodiment of the present application, the present application will be described with reference to Fig. 2 and Figs. 5-8.

Using the 7-piece spherical optical power structure, a WD=80mm projection lens is designed, the working wavelength λ=444nm-465nm, the lens focal length f=27.5mm, F/#=2.9, the design structure is shown in Figure 2, and the design parameters are shown in the table ( 1).

Table (1) WD=80mm projection lens design parameters

The surface number 0 is the projection surface, the

surface numbers

1 and 2 are the first lens, the

surface numbers

3 and 4 are the second lens, the

surface numbers

5 and 6 are the third lens, and the surface number 7 It is the diaphragm, the fourth lens with

surface numbers

8 and 9, the fifth lens with

surface numbers

10 and 11, the sixth lens with surface numbers 12 and 13, and the seventh lens with surface numbers 14 and 15 For lenses, those with surface numbers 16 and 17 are prisms, and those with surface numbers 18 and 19 are protective glass. The distance shown in the table is the distance between each surface of the lens and the surface of the previous lens. If it is the distance between the two surfaces of the same lens, it means the thickness of the lens. If it is the distance between the surfaces of different lenses, it means the distance between the lenses. The spacing shown in the row with the serial number 0 represents the distance between the surface of the first surface lens whose surface serial number is 1 and the projection surface.

Figure 5 is the MTF curve of the image quality of the WD=80mm projection lens, it can be seen that all fields of view are close to the diffraction limit, Figure 6 is the field curve of the WD=80mm projection lens, Figure 7 is the distortion curve of the WD=80mm projection lens, It can be seen that the field curvature is less than 20μm and the distortion is less than 0.01% under the full field of view. Figure 8 is the axial aberration curve of the WD=80mm projection lens, and it can be seen that the full aperture aberration is less than 0.01mm.

It can be seen from the data analysis of the above figures that the projection lens design has the advantages of full field of view ultra-high resolution imaging, small aberration, and ultra-low distortion.

Example 2

According to a specific embodiment of the present application, the present application will be described with reference to FIG. 3 and FIGS. 9-12 .

Using the 7-piece spherical optical power structure, a WD=190mm projection lens is designed. The working wavelength is λ=444nm-465nm, the lens focal length is f=30mm, and F/#=3.1. The design structure is shown in Figure 3, and the design parameters are shown in Table (2). ).

Table (2) WD=190mm projection lens design parameters

The surface number 0 is the projection surface, the

surface numbers

1 and 2 are the first lens, the

surface numbers

3 and 4 are the second lens, the

surface numbers

8 and 9, the fifth lens with

surface numbers

Figure 9 is the MTF curve of the imaging quality of the WD=190mm projection lens, it can be seen that the entire field of view is close to the diffraction limit, Figure 10 is the field curve of the WD=190mm projection lens, Figure 11 is the distortion curve of the WD=190mm projection lens, It can be seen that the field curvature is less than 20 μm and the distortion is less than 0.01% under the full field of view. Figure 12 is the axial aberration curve of the WD=190mm projection lens, and it can be seen that the full aperture aberration is less than 0.008mm.

It can be seen from the data analysis of the above figures that the projection lens design has the advantages of ultra-high-resolution imaging in the full field of view, small aberration, and ultra-low distortion.

Example 3

According to a specific embodiment of the present application, the present application will be described with reference to FIG. 4 and FIGS. 13-16 .

Using the 7-piece spherical optical power structure, a WD=350mm projection lens is designed. The working wavelength is λ=444nm-465nm, the lens focal length is f=28mm, and F/#=2.9. The design structure is shown in Figure 4, and the design parameters are shown in Table (3). ).

Table (3) WD=350mm projection lens design parameters

The surface number 0 is the projection surface, the

surface numbers

1 and 2 are the first lens, the

surface numbers

3 and 4 are the second lens, the

surface numbers

8 and 9, the fifth lens with

surface numbers

Figure 13 is the MTF curve of the imaging quality of the WD=350mm projection lens, it can be seen that the entire field of view is close to the diffraction limit, Figure 14 is the field curve of the WD=350mm projection lens, Figure 15 is the distortion curve of the WD=350mm projection lens, It can be seen that the field curvature is less than 20 μm and the distortion is less than 0.01% under the full field of view. Figure 16 is the axial aberration curve of the WD=350mm projection lens, and it can be seen that the full aperture aberration is less than 0.009mm.

Compared with the related art, the present application has the following advantages:

1. In this application, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are sequentially arranged along the optical axis projection surface to the image source surface; the first lens has a positive optical focus The second lens has positive power; the third lens has negative power; the fourth lens has positive power; the fifth lens has negative power; the sixth lens has positive power; the seventh lens has positive power A diaphragm is set between the third lens and the fourth lens, with a reasonable positive and negative power, and can design a projection with a working distance of 0-350mm with ultra-high resolution, small aberration, and distortion less than 0.01% The lens is suitable for high-precision 3D measurement.

2. The application of 7 spherical lenses can miniaturize the projection lens and save costs.

Claims

A projection lens, comprising:

a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens arranged in sequence from the projection surface to the image source surface along the optical axis;

The first lens has a positive refractive power; the second lens has a positive refractive power; the third lens has a negative refractive power; the fourth lens has a positive refractive power; the fifth lens has a negative refractive power degree; the sixth lens has positive refractive power; the seventh lens has positive refractive power.
The projection lens of claim 1, further comprising a diaphragm located between the third lens and the fourth lens.
The projection lens according to claim 2, wherein the air interval between the first lens and the second lens is in the range of 0.2-0.7 mm, and the air interval between the second lens and the third lens is in the range of 0.2-0.7 mm. is 1.2-1.6mm, the air interval between the third lens and the diaphragm is 4.9-5.3mm, the air interval between the diaphragm and the fourth lens is 6-6.3mm, the The air space between the fourth lens and the fifth lens is in the range of 0.9-1.2mm, the air space between the fifth lens and the sixth lens is in the range of 0.7-0.9mm, and the sixth lens and the The air space between the seventh lenses is in the range of 0.2-0.4 mm, and the air space between the seventh lens and the prism is in the range of 6-9 mm.
The projection lens of claim 1, wherein,

The focal length of the first lens is between 41mm and 46mm;

the focal length of the second lens is between 55mm and 73mm;

The focal length of the third lens is between -14mm and -11mm;

the focal length of the fourth lens is between 115mm and 134mm;

The focal length of the fifth lens is between -30mm and -26mm;

The focal length of the sixth lens is between 23mm and 28mm;

The focal length of the seventh lens is between 16mm and 21mm.
The projection lens of claim 1, wherein the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the The seventh lenses are all spherical lenses.
The projection lens of claim 1, wherein the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the The lenses of the seventh lens are all glass lenses.
The projection lens of claim 1, wherein an operating wavelength of the projection lens is between 444 nm and 465 nm.
The projection lens of claim 1, wherein the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the The refractive indices of the seventh lens are: 1.87, 1.876, 1.911, 1.873, 1.826, 1.86 and 1.917, respectively.
The projection lens of claim 1, wherein the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the The refractive indices of the seventh lens are: 1.869, 1.861, 1.913, 1.743, 1.863, 1.76 and 1.907, respectively.
The projection lens of claim 1, wherein the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the The refractive indices of the seventh lens are: 1.856, 1.854, 1.915, 1.69, 1.864, 1.763 and 1.91, respectively.