JP2001215170A - Method for inspecting lens surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently inspect lens surfaces. SOLUTION: A CCD camera 20 and a ring light source 23 are set with a finder 12 held therein. An imaging lens 22 of the CCD camera 20 is focused to meet a focus on the surface of the objective lens 15. The CCD camera 20 moves in a direction of an optical axis of the finder 12. The ring light source 23 moves in the direction of the optical axis of the finer 12 to retreat from an imaging range of the CCD camera 20. The surface of the objective lens 15 is imaged by the CCD camera 20. The obtained image signal is sent to an image processor 21, so that the presence/absence of defects is judged. Thereafter, the CCD camera 20 moves to focus on the surface of the eyepiece 16, and the same process is carried out. The inspection becomes efficient because two lenses can be inspected without disassembling a unit body 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting a surface of a plurality of lenses constituting an optical system.

[0002]

2. Description of the Related Art Various lenses constituting an optical system are important parts in a camera, and it is not preferable that a defect exists on the surface thereof. For example, in a film unit with a lens, if a defect such as a scratch or dust is present on the surface of a lens constituting a viewfinder, the subject becomes difficult to see, which is a great dissatisfaction for the photographer.

[0003] For this reason, a finder surface inspection is performed at the time of manufacturing or recycling a film unit with a lens. This inspection is performed by irradiating inspection light on the surface of the lens constituting the finder, imaging the surface of the lens, which is the object to be inspected, with an imaging device, and performing image processing on the obtained image signal. .

[0004]

In the case where the finder is composed of a plurality of lenses, only one of the lenses can be inspected. Therefore, it is necessary to perform the inspection with the finder disassembled into individual lenses. there were. Also, at the time of recycling, the inspection cannot be performed in the state of the finder unit, and it is necessary to perform the surface inspection in the state of further disassembly. For this reason, the inspection work has been inefficient.

On the other hand, when the finder is composed of a pair of lenses, image pickup devices are provided on both sides of a film unit with a lens, and the surface of each lens is imaged from both sides of the finder. Can be solved. However, since the number of imaging devices required for inspection increases to two, the cost increases and the size of the inspection device increases, so that there is a problem in performing efficient inspection.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide a method for inspecting a lens surface that can efficiently perform a surface inspection.

[0007]

In order to solve the above-mentioned problems, a method for inspecting a lens surface according to the present invention comprises disposing an image pickup device having a focus adjusting function on one side of an optical system, and disposing the image pickup apparatus on the other side of the optical system. An illumination device that illuminates the optical system from the other side at a position outside the imaging range of the imaging device is arranged on the side, and focusing and imaging of the imaging device are performed for each surface of the lens to be inspected, and the lens This is to inspect each surface for the presence or absence of a defect.

Further, the imaging device is moved in the direction of the optical axis of the optical system in accordance with the change of the surface of the lens to be inspected, and the focal length of the imaging lens of the imaging device is changed. Further, on the other side of the optical system, there is provided a screen for dark field within the imaging range of the imaging device. The lighting device is a ring-shaped light source centered on the optical axis of the optical system.

[0009]

FIG. 1 shows the structure of a surface inspection apparatus embodying the present invention. An opening for exposing the photographing lens 11 and the finder 12 to the outside is formed on the front surface of the lens-fitted film unit 10, and a shutter button 13 is provided on the upper part. On the back of the lens-fitted film unit 10, a winding knob 14 for feeding the photographic film loaded therein is provided. The finder 12 is composed of a pair of plastic lenses, and is attached so that the objective lens 15 and the eyepiece 16 are arranged in this order from the object side.

Behind the eyepiece 16 is a CCD camera 2
0 is arranged, and the surface of the finder 12 is imaged and converted into an image signal. The obtained image signal is transmitted to the image processing device 2
The image data is sent to 1 to perform image analysis to determine the presence or absence of a defect on the lens surface. The imaging lens 22 provided inside the CCD camera 20 has a variable focal length, and can focus on the surfaces of the objective lens 15 and the eyepiece 16. In addition, CCD camera 2
0 moves in the direction of the optical axis of the finder 12 to make its imaging range constant. Thus, even when focusing is performed, the imageable range of the CCD camera 20 can be effectively used.

A ring-shaped light source 23 used as an illumination device is arranged in front of the objective lens 15 and irradiates the finder 12 with inspection light. Here, when inspecting the CCD
The ring light source 23 is movable in the optical axis direction of the viewfinder so that the camera 20 does not project the image of the ring light source 23.

FIG. 2 shows how the inspection of the objective lens 15 is performed. The CCD camera 20 moves to a position away from the rear surface of the film unit with lens 10 by a distance L1, and the ring light source 23 moves to a position away from the CCD camera 20 by a distance L2. Ring light source 23 and CC
The position of the D camera 20 is predetermined in a test stage of the apparatus, and is written as position data in a memory (not shown). For example, L1 = 72 mm, L2 = 157 m
m and the focal length of the CCD camera 20 is 12.5 mm, the focus is focused on the surface of the objective lens 15.

Here, the objective lens 15 is a concave lens, and the inspection surface is curved. However, if the curvature is not extremely large, the objective lens 15 can be covered by the depth of field of the imaging lens 22, which greatly affects the inspection. There is no.

The surface image of the objective lens 15 is a CCD camera 2
The image signal obtained by the image processing is transmitted to the image processing device 21. The image processing device 21 compares the reference value written in advance in the internal memory with the signal intensity of each pixel, and determines that there is a defect when the difference becomes a certain value or more. Alternatively, it is also possible to compare the signal intensities of a plurality of adjacent pixels and determine that there is a defect when the difference between the maximum value and the minimum value is equal to or greater than a certain value.

When there is no defect on the surface of the objective lens 15, there is no change in the intensity of the passed inspection light, so that the signal intensity of the imaged pixel is constant. Therefore, the image processing device 22 determines that there is no abnormality. However, when the objective lens 15 has a defect such as dust or a scratch, the inspection light passing through the portion is scattered and a change in intensity occurs. Therefore, a change in the intensity of the inspection light is obtained as a change in the signal intensity by the CCD camera 20, and the image processing device 21 determines that there is an abnormality.

[0016] When an object is present on the light source side at the time of imaging, the object is imaged. Therefore, it may be determined that there is an abnormality even though there is no defect. Therefore, such a situation can be avoided by providing a black screen 24 in front of the ring-shaped light source 23 and performing the inspection in a dark field.

FIG. 3 shows how the eyepiece 16 is inspected. The CCD camera 20 moves to a position L3 away from the back of the lens-fitted film unit 10, and the ring light source 21 moves a distance L from the CCD camera 20.
Move 4 positions away. For example, L1 = 100 mm,
When L2 = 265 mm and the focal length of the CCD camera 20 is 25 mm, the surface of the eyepiece 16 is focused, and the same inspection as that of the objective lens 15 is performed.

Here, the objective lens 15 and the eyepiece 16
Is sufficiently longer than the depth of field of the imaging lens 22. Therefore, for example, even if there is a defect on the surface of the objective lens 15, the defect on the surface of the objective lens 15 will not be captured when the eyepiece 16 is focused. Therefore, only a lens having a defect can be accurately detected.

The operation of the above configuration will be described with reference to the flowchart of FIG. The lens-equipped film unit 10 in which the components are assembled is put into an inspection device, and the finder 12 is inspected. First, the ring-shaped light source 23 is moved to irradiate the surface of the objective lens 15 with the inspection light, and the CCD camera 20 is focused so as to focus on the surface of the objective lens 15.
Then, the surface of the objective lens is imaged by the CCD camera 20, and the obtained image signal is sent to the image processing device 21 to determine a defect.

Here, when it is determined that there is an abnormality,
The inspection ends at that point. The film unit with lens 10 in which an abnormality is found is disassembled, and the objective lens 15 is replaced with a new one. On the other hand, if it is determined that there is no abnormality, the ring-shaped light source 23 moves and the eyepiece 16
The focus of the CCD camera 20 is adjusted so as to focus on the surface of the camera. Then, the same inspection as in the case of the objective lens 15 is performed.

As described above, according to the inspection method of the present invention, the finder can be inspected without disassembling the film unit with the lens. Further, since the inspection system according to the present invention is not different from the conventional system, the accuracy of the inspection is almost the same as the conventional system. Therefore, it is possible to quickly perform a test having the same reliability as a conventional test device,
Inspection efficiency is improved. Further, since two lenses can be inspected using one CCD camera, the inspection apparatus can be reduced in size and cost.

In the above embodiment, the arrangement of the CCD camera 20 and the ring light source 23 can be reversed. Further, the eyepiece 16 may be inspected first.

In the above embodiment, an example in which the finder 12 composed of two lenses is used has been described. However, as shown in FIG. 5, a finder composed of three lenses 25, 26 and 27 is used. Also, the inspection can be performed without disassembling the lens-fitted film unit 10 by focusing the CCD camera 20 so that the desired lens surface is focused.

Further, even when a transparent exterior body 28 is attached to the outside of the main body, such as a film unit with a waterproof lens, the focus of the CCD camera 20 is taken into consideration in consideration of the refractive index of the exterior body 28. By performing alignment,
The inspection can be performed without removing the exterior body 28.

The inspection method of the present invention can be applied not only to a lens for a finder but also to an inspection of an internal part covered by a transparent part such as a two-lens photographic lens. In this case, the inspection can be performed by focusing on the surface of the component to be inspected in consideration of the refractive index of the external transparent body. Further, the inspection method of the present invention is not limited to a film unit with a lens, but can be applied to an inspection of an optical system of a general camera.

[0026]

As described above, according to the present invention,
Each time the lens constituting the finder is inspected, the focus position of the imaging device is adjusted, and the illumination device is moved so that the inspection light efficiently irradiates the lens of the inspection object. The defect inspection of the finder can be performed without disassembly, and the number of imaging devices required for the inspection can be reduced, so that the size and cost of the device can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a finder inspection apparatus.

FIG. 2 is a schematic view showing a state of inspecting an objective lens.

FIG. 3 is a schematic view showing a state of inspecting an eyepiece.

FIG. 4 is a flowchart showing a procedure for inspecting a finder;

FIG. 5 is a schematic view showing a state of inspecting a finder including three lenses.

FIG. 6 is a schematic view showing a state in which a finder is inspected when a film unit body with a lens is covered with a transparent body.

[Explanation of symbols]

 Reference Signs List 10 Film unit with lens 12 Viewfinder 15 Objective lens 16 Eyepiece 20 CCD camera 23 Ring light source

Claims (4)

[Claims] 1. A lens surface inspection method for inspecting the surfaces of a plurality of lenses constituting an optical system in a state where the optical system is configured, comprising: an image pickup device having a focus adjustment function on one side of the optical system. The device is arranged, and an illuminating device for illuminating the optical system from the other side at a position outside the imaging range of the imaging device is arranged on the other side of the optical system, and imaging is performed for each lens surface to be inspected. A method for inspecting a lens surface, comprising performing focusing and imaging of an apparatus, and inspecting each lens surface for the presence or absence of a defect. 2. The imaging device according to claim 1, wherein the imaging device is moved in an optical axis direction of an optical system according to a change in a surface of a lens to be inspected, and a focal length of the imaging lens of the imaging device is changed. 2. The method for inspecting a lens surface according to claim 1. 3. The method for inspecting a lens surface according to claim 1, wherein a screen is provided on the other side of the optical system to make a dark field within an imaging range of the imaging device. 4. The lens surface inspection method according to claim 1, wherein the illumination device is a ring-shaped light source centered on an optical axis of an optical system.