CN109164559B - Large-numerical aperture near-infrared object image bilateral telecentric optical system - Google Patents

Abstract

The invention introduces a large numerical aperture near-infrared object image bilateral telecentric optical system, which includes a first lens, a second lens, a beam splitting prism, a third lens, and a first lens, a second lens, a beam splitting prism, and a third lens arranged in sequence in the propagation direction of light from the image plane to the object plane. The fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, and the diaphragm. The first lens adopts a biconvex positive power lens, the second lens adopts a biconcave negative power lens, the third lens adopts a meniscus positive power lens, and the fourth lens adopts a biconvex positive power lens. power lens, the fifth lens adopts a biconcave negative power lens, the sixth lens adopts a biconvex positive power lens, the seventh lens adopts a biconvex positive power lens, and the eighth lens adopts a biconvex positive power lens. Meniscus positive power lens. The object-side numerical aperture of the invention reaches 0.5, and the detection and light-gathering ability is strong; the resolution reaches 0.85 μm, and high-resolution imaging can be achieved; in addition, the invention can realize bilateral telecentricity and low distortion of the object image.

Description

A large numerical aperture near-infrared object imaging bilateral telecentric optical system

Technical field

The invention relates to the field of optics, and in particular to a large numerical aperture near-infrared object image bilateral telecentric optical system.

Background technique

The current machine vision system uses an object-image bilateral telecentric optical system, which has the advantages of no image deformation, no viewing angle error, ultra-wide depth of field, ultra-low distortion, and constant imaging magnification. Compared with ordinary industrial lenses, it has obvious technical advantages. In precision industry It has been widely used in the field of detection. Bilateral telecentric optical lenses for object images in the existing market are generally used in the visible light detection spectrum band. There are fewer types of telecentric industrial lenses in the near-infrared spectrum band, and they have shortcomings such as insufficient resolution and insufficient detection capabilities.

Contents of the invention

In view of the shortcomings of the existing object-side telecentric optical system, the present invention provides a large numerical aperture near-infrared object image bilateral telecentric optical system.

In order to achieve the above objectives, the present invention adopts the following technical solutions:

A large numerical aperture near-infrared object image bilateral telecentric optical system, including a first lens, a second lens, a dichroic prism, a third lens, and a fourth lens arranged in sequence in the propagation direction of light from the image plane to the object plane. Diaphragm, fifth lens, sixth lens, seventh lens, eighth lens;

The first lens and the second lens constitute a front lens group, and the third lens, fourth lens, fifth lens, sixth lens, seventh lens and eighth lens constitute a rear lens group;

The optical power of the front lens group is set to φA, the optical power of the rear lens group is set to φC, and the optical power of the system is set to φ,

Then the ratio of φA to φ satisfies the following conditions:

1.8≤φA/φ≤2.2;

Then the ratio of φC to φ satisfies the following conditions:

9.1≤φC/φ≤10.5.

Further, the front surface curvature radius of the first lens is 32.863mm, the rear surface curvature radius is -55.462mm, the center thickness is 4.2mm, and the lens clear aperture is φ16.8mm; the curvature radius of the second lens front surface is -24.588 mm, the radius of curvature of the rear surface is 14.602mm, the center thickness is 2.5mm, and the clear aperture of the lens is φ12.2mm; the radius of curvature of the front surface of the third lens is -468.981mm, the radius of curvature of the rear surface is -52.485mm, and the center thickness is 8.7mm, the lens clear aperture is φ52.3mm; the front surface curvature radius of the fourth lens is 140.698mm, the rear surface curvature radius is -162.111mm, the center thickness is 6.7mm, and the lens clear aperture is φ50.2mm; The front surface curvature radius of the fifth lens is -66.202mm, the rear surface curvature radius is 39.859mm, the center thickness is 2.5mm, and the lens clear aperture is φ48.2mm; the sixth lens front surface curvature radius is 39.859mm, The radius of curvature of the rear surface is -185.774mm, the center thickness is 11.9mm, and the clear aperture of the lens is φ48.2mm; the radius of curvature of the front surface of the seventh lens is 50.225mm, the radius of curvature of the rear surface is -578.471, and the center thickness is 9.6mm , the clear aperture of the lens is φ49.1mm; the front surface curvature radius of the eighth lens is 23.513mm, the rear surface curvature radius is 35.756mm, the center thickness is 5.1mm, and the lens clear aperture is φ29.2mm.

Further, the fifth lens and the sixth lens form a double cemented lens.

Further, the first lens adopts a biconvex positive power lens, the second lens adopts a biconcave negative power lens, the third lens adopts a meniscus positive power lens, and the fourth lens adopts a biconvex lens. The fifth lens adopts a biconcave negative power lens, the sixth lens adopts a biconvex positive power lens, the seventh lens adopts a biconvex positive power lens, and the eighth lens adopts a biconvex positive power lens. Adopts meniscus-shaped positive power lens.

Further, the first lens is made of heavy lanthanum flint glass material, the second lens is made of flint glass material, the third lens is made of heavy crown glass material, and the fourth lens is made of crown glass. The fifth lens is made of flint glass material, the sixth lens is made of lanthanum glass material, the seventh lens is made of heavy crown glass material, and the eighth lens is made of heavy lanthanum material. Made of flint glass material.

The beneficial effects of the present invention are as follows:

The present invention uses the near-infrared spectrum band for industrial detection imaging. Compared with the visible spectrum band, it has the advantages of stronger resistance to external stray light and less susceptible to interference;

The invention realizes large numerical aperture detection imaging, solves the problem of insufficient detection capabilities of current CCD or CMOS cameras in the near-infrared spectrum band, and is conducive to obtaining high-contrast image information of the measured object;

The resolution of the present invention reaches 0.85 μm, realizing the detection capability of sub-micron imaging with physical resolution, and meeting the needs of high-end industrial detection machine vision for high-resolution detection imaging.

Description of the drawings

Figure 1 is a schematic diagram of the composition and structure of the optical system of the present invention;

Figure 2 is a graph of the optical transfer function of the optical system of the present invention at 600lp/mm;

Figure 3 is a distortion diagram of the optical system of the present invention.

Detailed ways

In order to facilitate those of ordinary skill in the art to better understand the essence of the present invention, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

With reference to Figures 1, 2 and 3, a large numerical aperture near-infrared object image bilateral telecentric optical system includes a first lens 1 and a second lens arranged sequentially in the direction of light propagation from the image plane 11 to the object plane 12. Lens 2, dichroic prism 3, third lens 4, fourth lens 5, diaphragm 6, fifth lens 7, sixth lens 8, seventh lens 9, eighth lens 10;

The first lens 1 and the second lens 2 constitute a front lens group, and the third lens 4, fourth lens 5, fifth lens 7, sixth lens 8, seventh lens 9 and eighth lens 10 constitute a rear lens. Group.

The near-infrared illumination light source couples the illumination light path and the imaging optical lens through the dichroic prism 3.

In this preferred embodiment, a CCD or CMOS camera can be placed on the image plane 11 to receive the object plane signal amplified by the industrial lens system, thereby obtaining clear and high-magnification object plane information.

The optical power of the front lens group is set to φA, the optical power of the rear lens group is set to φC, and the optical power of the system is set to φ,

Then the ratio of φA to φ satisfies the following conditions:

1.8≤φA/φ≤2.2;

Then the ratio of φC to φ satisfies the following conditions:

9.1≤φC/φ≤10.5.

In this embodiment, the dimensions of each lens are as follows: the front surface curvature radius of the first lens 1 is 32.863mm, the rear surface curvature radius is -55.462mm, the center thickness is 4.2mm, and the lens clear aperture is φ16.8mm; The front surface curvature radius of the second lens 2 is -24.588mm, the rear surface curvature radius is 14.602mm, the center thickness is 2.5mm, and the lens clear aperture is φ12.2mm; the front surface curvature radius of the third lens 4 is -468.981mm. The rear surface curvature radius is -52.485mm, the center thickness is 8.7mm, and the lens clear aperture is φ52.3mm; the front surface curvature radius of the fourth lens 5 is 140.698mm, the rear surface curvature radius is -162.111mm, and the center thickness is 6.7mm, the lens clear aperture is φ50.2mm; the front surface curvature radius of the fifth lens 7 is -66.202mm, the rear surface curvature radius is 39.859mm, the center thickness is 2.5mm, and the lens clear aperture is φ48.2mm; The front surface curvature radius of the sixth lens 8 is 39.859mm, the rear surface curvature radius is -185.774mm, the center thickness is 11.9mm, and the lens clear aperture is φ48.2mm; the front surface curvature radius of the seventh lens 9 is 50.225 mm, the rear surface curvature radius is -578.471, the center thickness is 9.6mm, and the lens clear aperture is φ49.1mm; the front surface curvature radius of the eighth lens 10 is 23.513mm, the rear surface curvature radius is 35.756mm, and the center thickness is 5.1mm, lens clear aperture is φ29.2mm

The fifth lens 7 and the sixth lens 8 form a double cemented lens.

In this embodiment, the materials for each lens are as follows: the first lens 1 is made of heavy lanthanum flint glass material, the second lens 2 is made of flint glass material, and the third lens 4 is made of heavy crown glass material. The fourth lens 5 is made of crown glass material, the fifth lens 7 is made of flint glass material, the sixth lens 8 is made of crown glass material, and the seventh lens 9 The eighth lens 10 is made of heavy crown glass material. The eighth lens 10 is made of heavy lanthanum flint glass material.

The first lens 1 adopts a biconvex positive power lens, the second lens 2 adopts a biconcave negative power lens, the third lens 4 adopts a meniscus positive power thick lens, and the fourth lens 5 A biconvex positive power lens is used, the fifth lens 7 is a biconcave negative power lens, the sixth lens 8 is a biconvex positive power lens, and the seventh lens 9 is a biconvex positive power lens. The eighth lens 10 adopts a meniscus-shaped positive power lens.

In this embodiment, the position relationship between the lenses is: the distance between the first lens 1 and the second lens 2 is 11.2mm; the distance between the second lens 2 and the dichroic prism 3 is 11.7mm; the distance between the dichroic prism 3 and the third lens 4 The distance is 61.7mm; the distance between the third lens 4 and the fourth lens 5 is 3.0mm; the distance between the fourth lens 5 and the aperture 6 is 1.2mm; the distance between the aperture 6 and the fifth lens 7 is 6.1mm; The distance between the sixth lens 8 and the seventh lens 9 is 0.5 mm; the distance between the seventh lens 9 and the eighth lens 10 is 28.5 mm; and the distance between the eighth lens 10 and the object plane 12 is 25 mm.

The optical system of the present invention belongs to the bilateral telecentric optical path of the object image. The angle between the principal ray on the object side and the optical axis does not exceed 0.02°, and the angle between the principal ray on the image side and the optical axis does not exceed 0.05°.

The specific parameters of the large numerical aperture near-infrared object image bilateral telecentric optical system of the present invention are:

The object-side numerical aperture is 0.5; the imaging magnification is 4 times; the object-side working distance is 25mm; the relative distortion does not exceed 0.015%; the object-side resolution is 0.85μm; the imaging spectrum ranges from 800nm to 850nm.

As can be seen from Figure 2, the optical transfer function value of all fields of view of this optical system is close to 0.4 at 600lp/mm, reaching the diffraction limit image quality, and the imaging quality is good.

It can be seen from Figure 3 that in the present invention, within the 10mm field of view of the image side, the distortion does not exceed 0.015%, which is close to zero, and effectively avoids measurement errors caused by distortion.

In the example of the present invention, it mainly solves the technical problem that the detection resolution in the near-infrared spectrum is limited by long wavelengths and cannot be easily improved, and realizes the design of a large numerical aperture optical system with diffraction-limited image quality. In order to achieve a high resolution of 0.85μm, the numerical aperture of this optical system reaches above 0.5; the light collection angle of this system to the object plane reaches 60°. The main aberrations of the optical system are spherical aberration and coma, except for third-order aberration. In addition to the fifth-order aberration, there will also be more than seven-order aberration. In order to solve this problem, the example of the present invention adopts a complex Petzval optical structure type, which mainly carries out complex design of the lens group on the object side, and adopts a nearly halo-free lens to bear the optical power. The spherical aberration at this position is at Minimum value, which can effectively reduce the spherical aberration of the system; use a combination of a doublet lens and a single lens to correct chromatic aberration; use two single lenses to correct spherical aberration and coma caused by the concave surface and the cemented surface of the doublet lens. Judging from the aberration correction results, this design completely corrects spherical aberration, coma, astigmatism, field curvature, distortion and chromatic aberration. Finally, diffraction-limited imaging quality was achieved. When the numerical aperture reaches 0.5, the imaging resolution is better than 0.85μm, which is unachievable with existing products on the market.

And in the example of the present invention, the object-side telecentricity does not exceed 0.02°. The object-side telecentricity design can effectively solve the problem of perspective image distortion and obtain high-resolution images without distortion; the image-side telecentricity does not exceed 0.05°. , reducing the adjustment accuracy of the CCD or CMOS camera and optical system. The full field of view distortion does not exceed 0.015%, which eliminates measurement errors caused by distortion and improves the measurement accuracy of the optical system. It can be known from the optical indicators of the above lens that the total length of the optical system of the present invention is only 195mm, and only 8 lenses are used to achieve diffraction limit imaging quality. It has the advantages of small size, light weight and low manufacturing cost, which is beneficial to the market. To promote.

The above specific embodiments describe the essence of the present invention in detail, but they cannot be used to limit the scope of the present invention. Obviously, inspired by the essence of the present invention, those skilled in the art can also make many improvements and modifications. It should be noted that these improvements and modifications all fall within the scope of the claims of the present invention.

Claims (3)

1. A large numerical aperture near-infrared object image bilateral telecentric optical system, characterized by: including a first lens, a second lens, a beam splitting prism, a third lens arranged in sequence in the propagation direction of light from the image plane to the object plane. Lens, fourth lens, diaphragm, fifth lens, sixth lens, seventh lens, eighth lens; The first lens and the second lens constitute a front lens group, and the third lens, fourth lens, fifth lens, sixth lens, seventh lens and eighth lens constitute a rear lens group; The optical power of the front lens group is set to φA, the optical power of the rear lens group is set to φC, and the optical power of the system is set to φ, Then the ratio of φA to φ satisfies the following conditions: 1.8 φA/φ/> 2.2; Then the ratio of φC to φ satisfies the following conditions: 9.1 φC/φ/> 10.5; The front surface curvature radius of the first lens is 32.863mm, the rear surface curvature radius is -55.462mm, the center thickness is 4.2 mm, and the lens clear aperture is φ16.8mm; the second lens front surface curvature radius is -24.588mm, The radius of curvature of the rear surface is 14.602mm, the center thickness is 2.5 mm, and the clear aperture of the lens is φ12.2mm; the radius of curvature of the front surface of the third lens is -468.981mm, the radius of curvature of the rear surface is -52.485mm, and the center thickness is 8.7 mm, the clear aperture of the lens is φ52.3mm; the front surface curvature radius of the fourth lens is 140.698mm, the rear surface curvature radius is -162.111mm, the center thickness is 6.7mm, and the lens clear aperture is φ50.2mm; The front surface curvature radius of the fifth lens is -66.202mm, the rear surface curvature radius is 39.859mm, the center thickness is 2.5mm, and the lens clear aperture is φ48.2mm; the sixth lens front surface curvature radius is 39.859mm, and the rear surface curvature radius is 39.859mm. The radius of curvature is -185.774mm, the center thickness is 11.9mm, and the clear aperture of the lens is φ48.2mm; the front surface curvature radius of the seventh lens is 50.225mm, the rear surface curvature radius is -578.471, and the center thickness is 9.6mm. The clear aperture is φ49.1mm; the front surface curvature radius of the eighth lens is 23.513mm, the rear surface curvature radius is 35.756mm, the center thickness is 5.1mm, and the lens clear aperture is φ29.2mm; The fifth lens and the sixth lens form a double cemented lens. 2. A large numerical aperture near-infrared object image bilateral telecentric optical system according to claim 1, characterized in that: the first lens adopts a biconvex positive power lens, and the second lens adopts a biconcave lens. A negative power lens, the third lens adopts a meniscus positive power lens, the fourth lens adopts a biconvex positive power lens, the fifth lens adopts a biconcave negative power lens, and the sixth lens adopts a biconcave negative power lens. The lens adopts a biconvex positive power lens, the seventh lens adopts a biconvex positive power lens, and the eighth lens adopts a meniscus positive power lens. 3. A large numerical aperture near-infrared object image bilateral telecentric optical system according to claim 1, characterized in that: the first lens is made of heavy lanthanum flint glass material, and the second lens is made of flint. The third lens is made of crown glass material, the fourth lens is made of crown glass material, the fifth lens is made of flint glass material, and the sixth lens is made of blue glass material. The seventh lens is made of crown glass material, the seventh lens is made of heavy crown glass material, and the eighth lens is made of heavy lanthanum flint glass material.