Low-distortion lens device suitable for pupil tracking

Abstract

The utility model relates to the technical field of optical design, in particular to a low-distortion lens device suitable for pupil tracking, which comprises a mounting frame, a first lens, a second lens and a third lens are mounted on one side of the mounting frame, the visual angle of the first lens is 60 degrees, the diagonal visual angle of the first lens is 78 degrees, and the visual angle of the second lens is 90 degrees. One side of the third lens is provided with an infrared optical filter, the thickness of the infrared optical filter is set to be 0.145 mm, and the optical back focal length of the third lens is set to be 1.02 mm. According to the utility model, the visual angle of the first lens is 60 degrees, and the diagonal visual angle reaches 78 degrees, so that the lens can keep better imaging quality in a wider visual angle range; and the optical back focal length of the third lens is set to be 1.02 mm, which is matched with the thickness of the infrared filter and the mechanical back focal length of the imaging plane, so that the overall optical performance is further optimized, and the imaging definition and detail expressive force are ensured.

Description

Technical Field

[0001] The utility model relates to the technical field of optical design, and particularly relates to a low-distortion lens device suitable for pupil tracking. Background Art

[0002] Eye tracking, also known as gaze tracking, is a technology for estimating the line of sight and / or fixation point of the eye by measuring eye movements. The most mainstream eye tracking method at present is called the pupil-corneal reflection method. The principle of this method is as follows: An infrared light source is directed at the eye, and the reflection point formed by the light source on the cornea is called a light spot (also called the Purkinje spot). An image acquisition device takes pictures of the eye, and thus an eye image with a light spot is obtained. When the eye rotates, the relative positional relationship between the pupil center and the light spot changes accordingly. A plurality of eye images with light spots collected by the image acquisition device reflect the corresponding positional change relationship, and the line of sight / fixation point can be estimated according to the positional change relationship.

[0003] After retrieval, the Chinese patent document application number: 201510494300.4 discloses an imaging lens, an iris imaging module, and a binocular iris recognition device, belonging to the field of biometric identification. The imaging lens sequentially includes, along the optical axis direction from front to back: a first lens, the first lens is a convex-concave lens with a positive optical power, its front surface is convex, and its rear surface is concave; a second lens, the second lens is a concave-convex lens with a negative optical power, its front surface is concave, and its rear surface is convex; a third lens, the third lens is a biconvex lens with a positive optical power, its front surface is convex, and its rear surface is convex; a fourth lens, the fourth lens is a biconcave lens with a negative optical power, its front surface is concave, and its rear surface is concave; the front surface and / or rear surface of the first lens, the second lens, the third lens, and the fourth lens are aspherical surfaces. This imaging lens has a simple structure and a small volume; good imaging quality and small distortion; and is suitable for binocular iris acquisition.

[0004] However, the above-mentioned imaging lens, iris imaging module, and binocular iris recognition device still have the following defects:

[0005] This device uses four groups of lenses for binocular iris acquisition, with relatively high costs and large shooting distortion, which affects the imaging quality. Therefore, we need a low-distortion lens device suitable for pupil tracking to solve the above problems. Summary of the Utility Model

[0006] The purpose of the present utility model is to provide a low-distortion lens device suitable for pupil tracking. By mainly combining a first lens, a second lens, and a third lens, and adopting an aspherical design for the front surface and / or the rear surface, the lens device can significantly reduce distortion during imaging. The viewing angle of the first lens is 60°, and the diagonal viewing angle reaches 78°. Such a design enables the lens to maintain good imaging quality within a relatively wide viewing angle range. At the same time, the optical back focal length of the third lens is set to 1.02 mm, which cooperates with the thickness of the infrared filter (i.e., 0.145 mm) and the mechanical back focal length of the imaging plane (i.e., 0.55 mm), further optimizing the overall optical performance and ensuring the clarity and detail expressiveness of the imaging.

[0007] To achieve the above object, the present utility model provides the following technical solution: A low-distortion lens device suitable for pupil tracking, including a mounting frame. One end of the mounting frame is installed with a sleeve. Inside the sleeve, a first lens, a second lens, and a third lens are installed. The first lens is a convex-concave lens, the second lens is a concave-convex lens, and the third lens is a concave-concave lens. The front surface and / or the rear surface of the first lens, the second lens, and the third lens are aspherical. The viewing angle of the first lens is 60°, the diagonal viewing angle of the first lens is 78°. One side of the third lens is provided with an infrared filter, the thickness of the infrared filter is set to 0.145 mm, the optical back focal length of the third lens is set to 1.02 mm. The outside of the infrared filter is provided with an imaging plane, the mechanical back focal length of the imaging plane is set to 0.55 mm, and the optical total length from the first lens to the imaging plane is set to 2.46 - 2.56 mm.

[0008] Preferably, the thickness of the first lens is 0.42 - 0.48 mm. The front surface of the first lens is convex, and the rear surface is concave, having a positive optical power.

[0009] By adopting the above technical solution, its optical power can be further optimized to ensure the clarity and accuracy of imaging.

[0010] Preferably, the viewing angle of the first lens is set as the vertical viewing angle and the horizontal viewing angle, and both the vertical viewing angle and the horizontal viewing angle are 60°.

[0011] By adopting the above technical solution, it can be ensured that when the user's head or eyes move slightly, the system can still continuously and accurately track the pupil position.

[0012] Preferably, a first diaphragm is installed at the connection between the second lens and the first lens, a second diaphragm is installed at the connection between the second lens and the third lens, and the thickness of the first diaphragm and the second lens is set to 1.11 mm.

[0013] By adopting the above technical solution, it is possible to ensure an appropriate amount of light entering the imaging plane, avoid overexposure or underexposure, and improve the imaging quality.

[0014] Preferably, the front surface of the second lens is concave and the rear surface is convex, having a negative optical power. The front surface of the third lens is concave and the rear surface is concave, having a negative optical power.

[0015] By adopting the above technical solution, the distribution and path of light can be controlled more flexibly, which helps to reduce the scattering and reflection of light inside the lens, improve the utilization rate of light and the imaging contrast.

[0016] Preferably, the mounting frame is square-shaped, the inner wall side length of the mounting frame is set to 2.35 mm, and the outer wall side length of the mounting frame is set to 2.72 - 2.78 mm.

[0017] By adopting the above technical solution, installation problems caused by size mismatch can be reduced.

[0018] Preferably, snap fasteners are installed on the four side walls of the mounting frame. The clamping end of the snap fastener is clamped at one end of the sleeve, and a sealing ring is provided on the inner wall of the sleeve.

[0019] By adopting the above technical solution, the lens device can be quickly installed on the sleeve or the corresponding installation position.

[0020] Preferably, bolts are installed at the four corners of the mounting frame, and the distance between the two bolts is set to 1.60 mm.

[0021] By adopting the above technical solution, the relative position between the mounting frame and the device or bracket can be ensured to be accurate, avoiding performance degradation or damage caused by installation errors.

[0022] Compared with the prior art, the beneficial effects of the present utility model are as follows:

[0023] 1. The present utility model mainly combines the first lens, the second lens and the third lens, and adopts an aspherical design for the front surface and / or the rear surface. The lens device can significantly reduce the distortion during imaging. The viewing angle of the first lens is 60°, and the diagonal viewing angle reaches 78°. Such a design enables the lens to maintain good imaging quality within a relatively wide viewing angle range. At the same time, the optical back focal length of the third lens is set to 1.02 mm, which cooperates with the thickness of the infrared filter (i.e., 0.145 mm) and the mechanical back focal length of the imaging plane (i.e., 0.55 mm) to further optimize the overall optical performance and ensure the imaging clarity and detail expressiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the three-dimensional structure of the present utility model;

[0025] Figure 2 Side view of the three-dimensional structure of the present utility model;

[0026] Figure 3 Cross-sectional view of the interior of the three-dimensional structure of the present utility model.

[0027] In the figure: 1, sleeve; 2, first lens; 3, first diaphragm; 4, second lens; 5, second diaphragm; 6, third lens; 7, infrared filter; 8, mounting frame; 9, buckle; 10, sealing ring; 11, bolt. Specific embodiments

[0028] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of the embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present utility model.

[0029] Please refer to Figures 1-3 , the present utility model provides a technical solution: a low-distortion lens device suitable for pupil tracking, including a mounting frame 8. One end of the mounting frame 8 is provided with a sleeve 1. The inside of the sleeve 1 is provided with a first lens 2, a second lens 4 and a third lens 6. The first lens 2 is a convex-concave lens, the second lens 4 is a concave-convex lens, and the third lens 6 is a concave-concave lens. The front surface and / or the rear surface of the first lens 2, the second lens 4 and the third lens 6 is an aspherical surface. The viewing angle of the first lens 2 is 60°, the diagonal viewing angle of the first lens 2 is 78°. One side of the third lens 6 is provided with an infrared filter 7. The thickness of the infrared filter 7 is set to 0.145 mm. The optical back focal length of the third lens 6 is set to 1.02 mm. The outside of the infrared filter 7 is provided with an imaging plane. The mechanical back focal length of the imaging plane is set to 0.55 mm. The total optical length from the first lens 2 to the imaging plane is set to 2.46 - 2.56 mm;

[0030] During use, through the combination of the first lens 2, the second lens 4, and the third lens 6, and by adopting aspherical designs for the front surface and / or the rear surface, the lens device can significantly reduce distortion during imaging. The viewing angle of the first lens 2 is 60°, and the diagonal viewing angle reaches 78°. Such a design enables the lens to maintain good imaging quality within a relatively wide viewing angle range. At the same time, the optical back focal length of the third lens 6 is set to 1.02 mm, which cooperates with the thickness of the infrared filter 7 (i.e., 0.145 mm) and the mechanical back focal length of the imaging plane (i.e., 0.55 mm), further optimizing the overall optical performance and ensuring imaging clarity and detail representation. By setting the infrared filter 7 on one side of the third lens 6, it can effectively filter out the interference of infrared light, improving the purity and contrast of the imaging.

[0031] The thickness of the first lens 2 is 0.42 - 0.48 mm. The front surface of the first lens 2 is convex, and the rear surface is concave, having a positive optical power. By precisely controlling the thickness of the first lens 2 (i.e., 0.42 - 0.48 mm), its optical power can be further optimized to ensure imaging clarity and accuracy.

[0032] The viewing angle of the first lens 2 is set for the vertical viewing angle and the horizontal viewing angle, both of which are 60°. The design with both the vertical and horizontal viewing angles of 60° means that the lens can cover a relatively wide field of view in both the horizontal and vertical directions, which is particularly important for pupil tracking applications because a wider field of view can ensure that the system can continuously and accurately track the pupil position even when the user's head or eyes move slightly.

[0033] A first diaphragm 3 is installed at the connection between the second lens 4 and the first lens 2, and a second diaphragm 5 is installed at the connection between the second lens 4 and the third lens 6. The thickness of the first diaphragm 3 and the second lens 4 is set to 1.11 mm. The settings of the first diaphragm 3 and the second diaphragm 5 can respectively control the light between the first two groups of lenses and the last two groups of lenses, ensuring an appropriate amount of light enters the imaging plane, avoiding overexposure or underexposure, and improving imaging quality.

[0034] The front surface of the second lens 4 is concave, and the rear surface is convex, having a negative optical power. The front surface of the third lens 6 is concave, and the rear surface is concave, having a negative optical power. Through the negative optical power designs of the second lens 4 and the third lens 6, the distribution and path of light can be controlled more flexibly, which helps to reduce the scattering and reflection of light inside the lens, improving the light utilization rate and imaging contrast.

[0035] The mounting frame 8 is square-shaped. The inner wall side length of the mounting frame 8 is set to 2.35 mm, and the outer wall side length of the mounting frame 8 is set to 2.72 - 2.78 mm. In the pupil tracking device, the standardized mounting frame 8 can ensure that the lens device can be accurately and stably mounted into the device, reducing installation problems caused by size mismatches.

[0036] Snap fasteners 9 are installed on the four side walls of the mounting frame 8. The clamping end of the snap fastener 9 is clamped at one end of the sleeve 1. A sealing ring 10 is provided on the inner wall of the sleeve 1. The design of the snap fastener 9 enables the lens device to be quickly mounted onto the sleeve 1 or the corresponding mounting position. At the same time, it is also convenient for disassembly and maintenance. The installation method without additional tools or complex steps improves the usability and maintenance efficiency of the device.

[0037] Bolts 11 are installed at the four corners of the mounting frame 8. The distance between the two bolts 11 is set to 1.60 mm. Setting the distance between the two bolts 11 to 1.60 mm helps to ensure the position accuracy of the mounting frame 8 during the installation process. Through precise measurement and positioning, it can be ensured that the relative position between the mounting frame 8 and the device or bracket is accurate without error, avoiding performance degradation or damage caused by installation errors.

[0038] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A low-distortion lens device applicable to pupil tracking, characterized in that: It includes an installation frame (8). One end of the installation frame (8) is installed with a sleeve (1). Inside the sleeve (1), a first lens (2), a second lens (4), and a third lens (6) are installed. The first lens (2) is a convex-concave lens, the second lens (4) is a concave-convex lens, and the third lens (6) is a concave-concave lens. The front surface and / or the rear surface of the first lens (2), the second lens (4), and the third lens (6) is an aspherical surface. The viewing angle of the first lens (2) is 60°, the diagonal viewing angle of the first lens (2) is 78°. One side of the third lens (6) is provided with an infrared filter (7). The thickness of the infrared filter (7) is set to 0.145 mm. The optical back focal length of the third lens (6) is set to 1.02 mm. The outside of the infrared filter (7) is provided with an imaging plane. The mechanical back focal length of the imaging plane is set to 0.55 mm. The total optical length from the first lens (2) to the imaging plane is set to 2.46 - 2.56 mm.

2. The low-distortion lens device applicable to pupil tracking according to claim 1, wherein: The thickness of the first lens (2) is 0.42 - 0.48 mm. The front surface of the first lens (2) is convex, and the rear surface is concave, having a positive optical power.

3. The low-distortion lens device applicable to pupil tracking according to claim 2, characterized in that: The viewing angle of the first lens (2) is set as the vertical viewing angle and the horizontal viewing angle, and both the vertical viewing angle and the horizontal viewing angle are 60°.

4. The low-distortion lens device applicable to pupil tracking according to claim 3, wherein: A first diaphragm (3) is installed at the connection between the second lens (4) and the first lens (2), and a second diaphragm (5) is installed at the connection between the second lens (4) and the third lens (6). The thickness of the first diaphragm (3) and the second lens (4) is set to 1.11 mm.

5. The low-distortion lens device applicable to pupil tracking according to claim 4, wherein: The front surface of the second lens (4) is concave, and the rear surface is convex, having a negative optical power. The front surface of the third lens (6) is concave, and the rear surface is concave, having a negative optical power.

6. The low-distortion lens device applicable to pupil tracking according to claim 5, wherein: The installation frame (8) is square-shaped. The inner wall side length of the installation frame (8) is set to 2.35 mm, and the outer wall side length of the installation frame (8) is set to 2.72 - 2.78 mm.

7. The low-distortion lens device applicable to pupil tracking according to claim 6, characterized in that: Clasps (9) are installed on the four side walls of the installation frame (8). The clamping end of the clasp (9) is clamped at one end of the sleeve (1), and a sealing ring (10) is arranged on the inner wall of the sleeve (1).

8. A low-distortion lens device applicable to pupil tracking according to claim 7, characterized in that: Bolts (11) are installed at the four corners of the installation frame (8). The distance between the two bolts (11) is set to 1.60 mm.

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