CN102944564A - Portable stray light detection device of double far center inclined lighting structure - Google Patents

Abstract

A portable double-telecentric oblique lighting structure stray light detection device belongs to the field of optical detection technology. In order to solve the problems of high cost, poor equipment portability and low efficiency of the existing optical system stray light detection method, the device consists of a lighting system, Composed of a bi-telecentric imaging system and a CCD system; the object space position of the bi-telecentric imaging system is the surface of the lens to be inspected, and the CCD system is placed at the image space, and the lens to be inspected, the bi-telecentric imaging system and the CCD system are coaxially placed, and the illumination The outgoing light of the system enters the lens to be inspected at an oblique angle and is focused by the lens to be inspected. The focal point is outside the bi-telecentric imaging system. The distance imaging system images on the CCD system, and the device has the advantages of low cost, high efficiency, and portability.

Description

A portable stray light detection device with bi-telecentric oblique illumination structure

technical field

The invention relates to a portable double-telecentric oblique illumination structure stray light detection device, which belongs to the technical field of optical detection.

Background technique

At present, in high-precision optical systems, stray light directly affects the performance of the system, and the smoothness of the optical lens, which is an important part of the optical system, has always affected the level of stray light in the system. There is no straightforward solution to the astigmatism detection problem. Usually, the surface microscopic inspection is carried out by using microscopic inspection instruments such as atomic force microscopes, or the system inspection is carried out after the lens is assembled into the lens by using an integrating sphere and other equipment. These methods have many disadvantages such as high cost, poor equipment portability, and low efficiency. The problem of system stray light has also become a bottleneck for the continued development of high-end optical systems.

Contents of the invention

In order to solve the problems of high cost, poor equipment portability and low efficiency of the existing optical system stray light detection method, the present invention provides a portable double telecentric oblique illumination structure stray light detection device.

The present invention is achieved through the following technical solutions:

A portable stray light detection device with a bi-telecentric oblique illumination structure, the device is composed of an illumination system, a bi-telecentric imaging system and a CCD system; the object space position of the bi-telecentric imaging system is the surface of the lens to be inspected, and the CCD is placed at the image space position system, and the lens to be inspected, the bi-telecentric imaging system and the CCD system are coaxially placed, the outgoing light of the illumination system is incident on the lens to be inspected at an oblique angle, and is focused by the lens to be inspected, and the focal point is outside the bi-telecentric imaging system. Part of the light in the system is scattered by the scattering points on the surface of the lens to be inspected, and the scattered light is imaged on the CCD system by the limited long-distance imaging system.

Beneficial effects of the present invention: the light emitted from the lighting system of the device of the present invention is incident on the surface of the lens to be inspected along a direction at a certain angle with the optical axis of the lens to be inspected, and the light is focused by the lens to be inspected outside the bi-telecentric imaging system to avoid entering the back The system affects the detection; part of the light incident on the stray point of the lens to be inspected is scattered to form scattered light, and the scattered light is imaged on the CCD system through the bi-telecentric imaging system, thereby realizing the stray light detection of the lens to be inspected; The imaging system in the device adopts a double-telecentric structure. Since the object-side depth of field and the image-side depth of field of the double-telecentric imaging system are large, it avoids inaccurate focusing of the imaging system, excessive curvature of the lens to be inspected, and CCD deviation from the image. The detection error caused by the surface position; the device has the advantages of low cost, high efficiency, and easy to carry.

Description of drawings

Figure 1: Schematic diagram of a portable double-telecentric oblique illumination structure stray light detection device of the present invention.

Fig. 2: Another schematic diagram of a portable double-telecentric oblique illumination structure stray light detection device of the present invention.

In the figure: 1. Illumination system, 2. Lens to be inspected, 3. Bi-telecentric imaging system, 4. CCD system, 5. Eyepiece system.

Detailed ways

The technical scheme of the present invention will be described in further detail below in conjunction with the accompanying drawings.

As shown in Figure 1, a portable double telecentric oblique illumination structure stray light detection device of the present invention is composed of an illumination system 1, a double telecentric imaging system 3 and a CCD system 4, and the double telecentric imaging system 3 and the CCD The system needs to be placed coaxially; the parallel light emitted by the illumination system 1 and the optical axis of the lens 2 to be inspected are obliquely incident on the lens 2 to be inspected at an angle A, and the light is focused by the lens 2 to be inspected outside the bi-telecentric imaging system 3. In order not to enter the following system to affect the detection result; part of the light from the illumination system 1 is scattered by the scattering points on the surface of the lens 2 to be inspected to form scattered light, and the scattered light is imaged on the CCD system 4 through the bi-telecentric imaging system 3 .

The light emitted by the illumination system 1 is parallel light or light with a certain divergence angle (convergence angle). The light is obliquely incident on the lens 2 to be inspected at an angle A with the optical axis of the lens to be inspected. A receiving screen can be used to receive and focus Point, when other devices and the lens 2 to be inspected are not moving, the outgoing light of the conversion lighting system 1 is incident on the lens 2 to be inspected, and the incident angle is angle A. When the focus received by the receiving screen has just moved out of the double telecentric imaging When the field of view of system 3 is used, the angle at this time is θ, then the range of angle A should be greater than or equal to θ but less than 90°.

The bi-telecentric imaging system 3 belongs to the short-distance imaging system, and the system design wavelength is the wavelength of the illumination source. The bi-telecentric imaging system 3 is composed of 7 mirrors. The three lenses from the object side are regarded as the front mirror group, and the rear 4 lenses are regarded as the rear mirror group. The right focus of the front mirror group and the left focus of the rear mirror group Coincident, the aperture is set at this focal point. The image formed by the diaphragm passing through the front mirror group is the entrance pupil. In the bi-telecentric imaging system 3, the object space is infinitely far away. The image formed by the diaphragm passing through the rear mirror group is the exit pupil. In the bi-telecentric imaging system 3 The image square of is infinite. The chief ray passing through the center of the diaphragm must exit the object space and image space of the bi-telecentric imaging system 3 in parallel, otherwise the chief ray of the light beam emitted by the object plane of the bi-telecentric imaging system must pass through the entrance pupil, diaphragm and exit pupil and perpendicular to the image plane; while the chief ray of the beam emitted by the image plane of the double telecentric imaging system must pass through the center of the exit pupil, diaphragm and entrance pupil, and be perpendicular to the object plane. If the lens 2 to be inspected undergoes a certain translation along the optical axis, its real image plane will deviate from the position of the CCD system 4, but its chief ray still passes through the same position of the CCD; in the same way, if the translation of the CCD system 4 occurs along the optical axis, its The conjugate object plane will also deviate from the position of the lens to be inspected, but the chief ray of the point imaged on the CCD can still be regarded as coming from the corresponding position of the lens to be inspected 2 . According to above-mentioned situation, adopt bi-telecentric imaging system 3, can make the device of the present invention under the situation that the lens to be inspected deviates from the object plane, the focus of the imaging system is inaccurate, the curvature of the lens to be inspected is too large, and the CCD deviates from the position of the image plane. There will be no measurement error, and a clear image can be formed. The bi-telecentric imaging system 3 is an imaging system with relatively large object-side depth of field and image-side depth of field, which can avoid detection errors within the range of depth of field.

The lens 2 to be inspected is placed at the object distance position of the bi-telecentric imaging system 3, and the lens 2 to be inspected is placed coaxially with the imaging system 3, and part of the light from the illumination system 1 is captured by the defects, flaws or surface dust of the lens 2 to be inspected. Scattering to form scattered light. For the bi-telecentric imaging system 3, this part of the scattered light is emitted by a point light source with the surface of the lens 2 to be inspected as the object distance. The scattered light is imaged by the bi-telecentric imaging system 3.

Use the CCD system 4 to receive the image point of the above scattered light. The CCD system 4 is placed at the image distance position of the bi-telecentric imaging system and placed coaxially with the bi-telecentric imaging system 3. It is in a conjugate position relationship with the lens 2 to be inspected. The signal collected by the system 4 is processed by the computer and observed through the display screen, so that the defects of the lens to be inspected, the distribution of defect points and the density of dust pollutants can be observed.

As shown in Figure 2, the eyepiece system 5 is placed behind the bi-telecentric imaging system 3, so that the object plane position of the eyepiece system 5 coincides with the image plane position of the bi-telecentric imaging system 3, and the image of the scattered light is captured by the eyepiece system 5 Projected to infinity for direct observation by the human eye.

Claims (3)

1. portable two heart oblique illumination structure parasitic light pick-up units far away is characterized in that this device is comprised of illuminator (1), two telecentric imaging systems (3) and CCD system (4); The object space position of two telecentric imaging systems (3) is lens to be checked (2) surfaces, CCD system (4) is put in the image aspect, and lens to be checked (2), the coaxial placement of two telecentric imaging systems (3) and CCD system (4), the emergent light of illuminator (1) incides lens to be checked (2) with the angle of inclination, focused on by lens to be checked (2), focus is outside two telecentric imaging systems (3), the part light of illuminator (1) is by lens to be checked (2) surface scattering point scattering, and the light after the scattering is imaged in the CCD system (4) by finite distance imaging system (3).

2. a kind of portable two heart oblique illumination structure parasitic light pick-up units far away according to claim 1 is characterized in that illuminator (1) becomes an angle of inclination with lens to be checked (2) optical axis; The emergent light of illuminator (1) incides on the lens to be checked (2) with the angle of inclination.

3. a kind of portable two far away heart oblique illumination structure parasitic light pick-up units according to claim 1, it is characterized in that, described CCD system (4) can replace to eyepiece system (5), and light is through being imaged on the object plane position of eyepiece system (5) through two telecentric imaging systems (3) after the scattering again.

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