CN105652413B - A kind of image-forming objective lens suitable for RGB D cameras - Google Patents

Abstract

An imaging objective lens suitable for RGB-D cameras disclosed by the present invention has a first lens, a first spacer, a second lens and a third lens that are bonded sequentially from the object side to the image side in the lens barrel to form an imaging lens . The imaging objective lens adopts a three-piece spherical mirror structure, and each lens has one mirror surface as a plane and the other as a spherical surface, with low processing cost. At the same time, the second lens and the third lens are closely attached without spacers, and the structure is compact. It is compact, and the radius of the three lenses is the same, and the assembly process is simple. In the wide spectral region from visible light to near-infrared, the imaging resolution is high, the optical performance is excellent, and it can reach a large field of view of 65°, and the distortion is less than 3.2%. A depth imaging system that can be applied to infrared auxiliary lighting to achieve friendly and easy-to-use natural human-computer interaction.

Description

An imaging objective lens suitable for RGB-D camera

technical field

The invention relates to an imaging objective lens suitable for RGB-D cameras, which is suitable for the fields of depth imaging and human-computer interaction.

Background technique

With the continuous popularization and development of computer technology, friendly and easy-to-use natural human-computer interaction will become a major trend in the development of human-computer interaction. Depth imaging technology, as an important input technology in natural human-computer interaction technology, makes non-contact gesture and gesture interaction possible. The RGB-D camera is the key device for depth imaging. The system uses it to obtain the three-dimensional depth information of the scene. Therefore, its imaging quality directly affects the accuracy and resolution of depth imaging, which in turn affects the human-computer interaction experience.

Existing imaging lenses only optimize image quality for the visible light region, and perform poorly in the near-infrared region. It is necessary to add an infrared cut filter in front of the image sensor to eliminate the influence of infrared light.

For the depth imaging system, the near-infrared region is an important spectral region. When the ambient light is poor, the near-infrared light source is usually used for auxiliary lighting. In terms of technology, the near-infrared light source is an important illumination source, so the imaging quality in the near-infrared region should also be considered. Therefore, in order to meet the application needs of RGB-D cameras, it is necessary to design an imaging objective lens with good imaging quality in a wide spectral region from visible light to near-infrared.

Contents of the invention

Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a compact structure, simple assembly process, high image definition, large field of view and small distortion in the wide spectral region from visible light to near infrared, suitable for RGB-D The imaging objective lens of the camera.

A kind of imaging objective lens that is suitable for RGB-D camera of the present invention comprises three lenses altogether in the lens barrel, and from the object side to the image side there are the first lens, the first spacer, the second lens and the first lens that fit successively. Three lenses constitute an imaging lens. Wherein the first lens is a positive lens, which faces the object side as a convex surface, and faces the image side as a plane; the second lens is a negative lens, which faces the object side as a plane, and faces the image side as a concave surface; the third lens is a positive lens, which faces The object space is a plane, and the image side is a convex surface. A first spacer located between the first lens and the second lens simultaneously functions as an aperture stop. Behind the third lens is a pressure ring, which is screwed and fitted with the lens barrel through threads. The end of the lens barrel has an external thread to cooperate with the lens mount.

In the above technical solution, the lens radii of the first lens, the first spacer, the second lens and the third lens are all 1.1000mm.

The first lens can be made of H-ZLAF52 glass material, the curvature radius of the convex surface of the first lens is 2.9630mm, the mirror distance is 0.8100mm, the mirror radius is 0.9000mm, the plane curvature radius of the first lens is infinite, and the mirror distance is 0.3000mm , the mirror radius is 0.6130mm.

The second lens can be made of H-ZF1 glass material, the plane radius of curvature of the second lens is infinite, the mirror distance is 0.4000mm, the mirror radius is 0.1800mm, the concave curvature radius of the second lens is 2.3310mm, and the mirror distance is 0.1053mm, Mirror radius 0.6927mm.

The third lens can be made of H-LAK3 glass material, the plane radius of curvature of the third lens is infinite, the mirror distance is 0.9500mm, the mirror radius is 1.1000mm, the convex curvature radius of the third lens is -1.5880mm, and the mirror radius is 0.9000mm .

An imaging objective lens suitable for RGB-D cameras of the present invention adopts a three-piece spherical mirror structure, and each lens has one mirror surface as a plane and the other surface as a spherical surface, and the processing cost is low. At the same time, the second lens and the third lens Tight fit, no need for spacer, compact structure, small size, and the three lenses have the same radius, and the assembly process is simple. The optical design is easy, the image definition is high in the wide spectral region from visible light to near-infrared, and the optical performance is excellent. It can achieve a large field of view of 65°, less than 3.2% distortion, and a very high optical transfer function (MTF).

Description of drawings

Fig. 1 is a schematic diagram of the overall structure of the present invention.

Figure 2 is the optical transfer function of the present invention.

Figure 3 is the distortion of the present invention.

Detailed ways

Further illustrate the present invention below in conjunction with accompanying drawing.

As shown in Fig. 1, a kind of imaging objective lens that is applicable to RGB-D camera of the present invention comprises three lenses 1, 2, 3 altogether, and there are first lens 1, first spacer successively from object side to image side in lens barrel 6 The ring 4, the second lens 2 and the third lens 3 are bonded to form an imaging lens. Wherein the first lens 1 is a positive lens, which faces the object side as a convex surface, and faces the image side as a plane; the second lens 2 is a negative lens, which faces the object side as a plane, and faces the image side as a concave surface; the third lens 3 is a positive lens , which is a plane facing the object side and a convex surface facing the image side. The first spacer 4 located between the first lens 1 and the second lens 2 simultaneously functions as an aperture stop. Behind the third lens 3 is a pressure ring 5, which is screwed and fitted with the lens barrel 6 through threads. The end of lens barrel 6 has external thread and can cooperate with lens holder.

When applied to RGB-D cameras, the imaging objective lens of the present invention can obtain clear imaging from visible light to near-infrared, and after cooperating with the lighting system and image acquisition and processing software system, a scene depth map with high accuracy and resolution precision will be obtained . There are three lenses 1, 2, and 3 in the lens barrel 6 of the imaging objective lens suitable for RGB-D cameras in this example, and there are 6 mirror surfaces in total, which are defined successively from the object side to the image side: the convex surface of the first lens 1 is the first One mirror, the plane of the first lens 1 is the second mirror; the plane of the second lens 2 is the third mirror, and the concave surface of the second lens 2 is the fourth mirror; the plane of the third lens 3 is the fifth mirror, and the third lens The convex surface of 3 is the sixth mirror surface. The structural parameters of the six mirrors are shown in Table 1:

Table 1

Figures 2 and 3 illustrate the optical imaging performance of the present invention.

Figure 2 calculates the optical transfer function values of the three fields of view in the normalized coordinates with a field angle of 0° (central field of view), a field of view of 22.75° (0.7 field of view), and a field of view of 32.5° (edge field of view). As seen from Fig. 2, when the transfer function of the present invention is 0.3, the transfer function value of the angle of view 32.5 ° (edge field of view) can reach 70lp/mm, and the transfer function value of the angle of view 22.75 ° (0.7 field of view) can reach 91lp/mm, the transfer function value of the field of view 0° (central field of view) can reach 105lp/mm. It shows that the maximum field of view of an imaging objective lens suitable for RGB-D cameras of the present invention can reach 65°, and clear imaging can be obtained. Fig. 3 is a distortion curve of an imaging objective lens suitable for RGB-D cameras of the present invention at 470nm, 535nm, 640nm and 850nm. Specifically, the maximum distortion of the imaging objective lens at a wavelength of 470nm is 3.08143%, the maximum distortion at a wavelength of 535nm is 3.06866%, the maximum distortion at a wavelength of 640nm is 3.07992%, and the maximum distortion at a wavelength of 850nm is 3.12895% , are controlled below 3.2%. Figure 2 and Figure 3 show that an imaging objective lens suitable for RGB-D cameras of the present invention has the advantages of large field of view, small distortion and high resolution in the wide spectral region from visible light to near infrared.

Claims (1)

1. An imaging objective lens suitable for RGB-D cameras, characterized in that: it comprises a lens barrel (6), in which the first lens (1), the second A spacer (4), the second lens (2) and the third lens (3) constitute an imaging lens; wherein the first lens (1) is a positive lens with a convex surface facing the object side and a plane facing the image side; The second lens (2) is a negative lens, which faces the object side as a plane, and faces the image side as a concave surface; the third lens (3) is a positive lens, which faces the object side as a plane, and faces the image side as a convex surface; the first spacer ( 4) At the same time, it acts as an aperture diaphragm. There is a pressure ring (5) behind the third lens (3), and the pressure ring (5) is screwed to fit the lens barrel (6) through threads; the end of the lens barrel (6) There are external threads to cooperate with the lens holder; the lens radii of the first lens (1), the second lens (2) and the third lens (3) are all 1.1000mm; The first lens (1) is made of H-ZLAF52 glass material, the convex curvature radius of the first lens is 2.9630mm, the mirror distance is 0.8100mm, the mirror radius is 0.9000mm, the plane curvature radius of the first lens is infinite, and the mirror distance is 0.3000mm, the mirror radius is 0.6130mm; the second lens (2) is made of H-ZF1 glass material, the plane curvature radius of the second lens is infinite, the mirror distance is 0.4000mm, the mirror radius is 0.1800mm, the concave surface of the second lens The radius of curvature is 2.3310mm, the mirror distance is 0.1053mm, and the mirror radius is 0.6927mm; the third lens (3) is made of H-LAK3 glass material, the plane radius of curvature of the third lens is infinite, the mirror distance is 0.9500mm, and the mirror radius is 1.1000 mm, the radius of curvature of the convex surface of the third lens is -1.5880mm, and the radius of the mirror surface is 0.9000mm.