JPH11304640A - Inspection apparatus for optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an inspection apparatus by which a lens to be inspected can be inspected wholly in a short time by a method wherein the lens to be inspected is inspected by transmitted light and only scattered light which is radiated from the lens to be inspected is detected selectively. SOLUTION: The parallel luminous flux of a laser 1 is expanded by a beam expansion system 3, it is incident on a convex lens 3 as a parallel luminous flux, and the radiant light of a lens 5 to be inspected is changed into a parallel luminous flux by a convex lens 4. The position of the convex lens 3 and that of the convex lens 4 are decided while their drive is controlled by a control device 13 on the basis of information on the lens 5 to be inspected. The radiant light of the lens 5 to be inspected is incident on a taking lens 6 and a beam splitter 7, its transmitted light is incident on a spatial filter 8 in the rear focus position of the taking lens 6, the parallel luminous is cut off, its pattern is selected, and scattered light in a specific direction is extracted. The reflected light of the beam splitter 7 is incident on an imaging element 10, an imaged signal is image-processed by a processor 12, and the deviation of the lens 5 to be inspected is measured. On the basis of the position of the lens 5 to be inspected is fine adjusted by the control device 13, the imaged signal is image-processed by the processor 12, and the quality of the lens 5 to be inspected is judged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection system for an optical system or an optical element used in various optical instruments.

[0002]

2. Description of the Related Art In the manufacture of an optical system, an appearance inspection of an optical element such as a lens constituting the optical system is required.
However, since lenses have various curvatures, unlike flat glass, inspection under a single condition is impossible, and inspection must be performed with various configurations according to the shape.

In the conventional inspection of a lens, it is common to irradiate white light to a lens to be inspected and visually inspect the scattered light from the lens or perform image processing to inspect the lens.

[0004]

However, in the conventional scattered light detection using white light, there are many types of lenses, and there is a problem that it is difficult to determine conditions for covering various objects. The effect of the large variation in the shape of the target lens is, for example, that the inspection area is not limited to the entire lens but is limited to a range in which the inspection can be performed stably, and it is not possible to perform the entire inspection at once and it takes time. Also,
The arrangement of the inspection optical system differs depending on the curvature of the lens, which may cause the illumination system and the imaging system constituting the inspection optical system to need to be largely moved.

[0005]

SUMMARY OF THE INVENTION An optical element inspection apparatus according to the present invention has been made in view of the above problems, and realizes a change of an inspection optical system with a minimum movement for various lens shapes and a short inspection time. It aims to inspect the whole lens in time. For this reason, the present invention is characterized in that a lens as an object to be inspected is inspected with transmitted light, and only scattered light emitted from the lens to be inspected is selectively detected. In the present invention, the change of the parameter as the lens to be tested,
For example, it is characterized in that all changes in the convex lens, the concave lens, the focal length, and the like are adjusted and realized by moving the system on the entrance side of the inspection optical system with respect to the test lens.

[0006]

FIG. 1 shows an inspection optical system of an optical element inspection apparatus according to Embodiment 1 of the present invention. In the figure, 1 is a laser of a light source, 2 is a beam expanding system, 3 is a convex lens 1, 4 is a convex lens 2, 5 is a test lens, 6 is a photographing lens, 7 is a beam splitter, 8 is a spatial filter, 9
And 10 are imaging elements which are photoelectric elements, 11 is a processing device,
Reference numeral 12 denotes a control device.

The parallel light beam emitted from the laser 1 is expanded by the beam expansion system 2 in accordance with the inspection range of the lens 5 to be inspected, and is incident on the three convex lenses 1 as a parallel light beam. The 3 convex lenses 1 and 4 have a role of generating a wavefront corresponding to the test lens 5 so that the light beams emitted from the test lens 5 become parallel. 3 convex lenses 1, 4
The convex lens 2 may be a lens group composed of a plurality of lenses, or may be a zoom lens with a variable focal length. The arrangement of the two convex lenses 3 and 4 differs depending on whether the test lens 5 is a convex lens or a concave lens.

FIG. 2 shows an arrangement in the case where the test lens 5 is a concave lens in the first embodiment. The light beam emitted from the fourth convex lens 2 is convergent light, and the focal point coincides with the rear focal position of the lens 5 to be measured. Therefore, the converging point of the three convex lenses 1 on which the parallel light beam enters is formed on the laser side from the front focal position of the fourth convex lens 2. The convex lens 2 of 4 is 3
A real image is formed such that the focal point of the convex lens 1 coincides with the rear focal position of the test lens 5 as described above.

FIG. 3 shows an arrangement in the case where the lens 5 to be inspected is a convex lens in the first embodiment. The focal point of the third convex lens 1 is set to be closer to the test lens than the front focal position of the fourth convex lens 2. Therefore, the convex lens 2 of 4
Is divergent light emitted from the position of the virtual image. The positions of the three convex lenses 1 and 4 are determined in accordance with the focal length of the lens 5 to be measured. 4 convex lens 2
If the converging point of the real image or virtual image generated in step (1) coincides with the front focal position of the test lens 5, a parallel light beam can be generated on the exit side of the test lens 5. Also in FIG. 3, since the front focal position of the test lens 5 coincides with the virtual image of the convex lens 2 of 4, the light beams emitted from the test lens 5 are almost parallel.

The positions of the three convex lenses 1 and 4 are determined based on information on the lens 5 to be measured. The drive system controlled by the control device 13 is moved according to the determined position to realize a desired arrangement.

In the present invention, since the state of all the light beams emitted from the test lens 5 can be controlled by the adjustment function of the optical system before entering the test lens 5, it is not necessary to move the test lens 5. Since the light beam is controlled by guiding the inspection optical system to an arrangement corresponding to the test lens 5, the light beam emitted from the test lens 5 is almost always a parallel light beam.

The collimated light beam emitted from the test lens 5 then enters the photographing lens 6 and the beam splitter 7. The beam splitter 7 divides a light beam with an amplitude ratio of 1: 1 between reflection and transmission. If dust or the like adheres to the surface of the beam splitter 7, it becomes a noise source and can be removed as necessary.

The luminous flux transmitted through the beam splitter 7 is converted into a spatial filter 8 disposed at a rear focal position of the photographing lens 6.
Incident on. Since the light beam emitted from the test lens 5 is a parallel light beam, the light beam is transmitted through the photographing lens 6 and then condensed at the rear focal position of the photographing lens 6. The spatial filter 8 is the lens 5 to be inspected.
And has a role of cutting the parallel light beam that has exited.

However, the light transmitted through the test lens 5 is not limited to the parallel light described above. The light of the component which is not parallel light is scattered light generated from a defective portion of the lens. Spatial filter 8 placed at rear focal position of photographing lens 6
By selecting the pattern described above, it is possible to selectively extract a component of light in a specific direction that is not parallel to the optical axis from the light emitted from the test lens 5.

In this embodiment, a portion of about 1 to 2 mm including the optical axis is arranged, and all components other than the parallel light beam are detected. The component that has passed through the spatial filter 8 is an image sensor 9
To reach. The position of the image sensor 9 is conjugate with the lens 5 to be inspected by the photographing lens 6. Due to the conjugate relationship and the action of the spatial filter 8, light other than the parallel component emitted from the test lens 5, that is, scattered light, forms an image on the image sensor 9, and an image of a defective portion of the test lens 5 is formed Is done. In this case, ghosts and flares generated inside the photographing lens 6 ride on the image sensor 9 as offsets, but this component is removed by image processing.

On the other hand, the reflected light from the beam splitter 7 enters the image pickup device 10. The image sensor 10 is adjusted to a position near the rear focal position of the photographing lens 6 where the signal from the image sensor 10 is not saturated. The light beam emitted from the lens 5 to be inspected is almost a parallel light beam, but the degree of parallelism is slightly different depending on the type of the lens 5 to be inspected. Image sensor 10
Monitors the parallel state of the light emitted from the lens 5 to be inspected. The signal of the image sensor 10 is image-processed by the processing device 12, and the displacement of the lens 5 is measured. On the basis of the measured shift information, the control device 13 controls the three convex lenses 1,
The position of the convex lens 2 or the position of the test lens 5 is finely adjusted in a plane orthogonal to the optical axis. After the fine adjustment, when the positions of the 3 and 4 convex lenses 1 and 2 or the position of the test lens 5 are determined, the signal of the imaging element 9 is subjected to image processing by the processing device 11,
The quality of the test lens 5 is determined.

The system shown in FIG. 1 is a basic arrangement of the present invention. If a cut-off portion of the spatial filter 8 is arranged according to a spatial component to be cut, a desired spatial component can be selectively imaged. . In order to increase the degree of freedom in selecting a spatial component, it is possible to employ a device such as a liquid crystal as the spatial filter 8 and make the size of the cutoff portion variable. The three convex lenses 1 and 4 constituting the incident optical system may be a lens group composed of a plurality of lenses or a zoom lens with a variable focal length.

Instead of the image pickup device 10 for detecting the parallel state from the test lens disposed in the detection system, a split sensor is disposed near the rear focal position of the photographing lens 6 and the optical axis of the test lens 5 May be detected in a plane perpendicular to.

[0019]

As described above, the optical element inspection apparatus of the present invention has at least two positive powers for the state of the inspection light incident on the lens to be inspected according to the type of the lens to be inspected. By controlling the relative positions of the lens groups by changing the relative positions, it has become possible to realize an optical element measuring apparatus having flexibility that can be used for test lenses having various shapes. Since the control of the state of the incident light can be easily performed at intervals between at least two lens groups, the inspection time is also reduced.

Further, in the present invention, scattered light can be extracted using an optical sky filter, so that measurement can be performed at low cost and with a short inspection time without requiring complicated electric processing.

[Brief description of the drawings]

FIG. 1 is a diagram showing an optical element inspection apparatus according to a first embodiment of the present invention;

FIG. 2 is a diagram illustrating a configuration of an inspection optical system when a test lens is a concave lens in the first embodiment.

FIG. 3 is a diagram illustrating a configuration of an inspection optical system when a lens to be inspected is a convex lens in the first embodiment.

[Explanation of symbols]

 Reference Signs List 1 light source (laser), 2 beam expansion system, 3 convex lens 1, 4 convex lens 2, 5 test lens, 6 photographing lens, 7 beam splitter, 8 spatial filter, 9 image sensor, 10 image sensor, 11 processing device, 12 control Device, 13 control device

Claims (9)

[Claims] 1. An optical element inspection apparatus for inspecting a defect of an optical element, wherein the inspection apparatus has an adjustment optical system having an adjusting function of converting a light beam emitted from the optical element to be examined into a substantially parallel light beam;
An optical element inspection apparatus, comprising: a photographing lens disposed following the parallel light beam; a spatial filter disposed at a focal position of the photographing lens; and a photoelectric detection element. 2. The optical system according to claim 1, wherein the spatial filter cuts a parallel light beam component emitted from the optical element to be detected, and detects only scattered light generated inside the surface of the optical element to be inspected. Device inspection device. 3. An optical element inspection apparatus according to claim 2, wherein said incident optical system comprises at least two convex lens systems, and a distance between said two convex lens systems is variable. 4. The optical element inspection apparatus according to claim 3, wherein the light beam exiting from the incident optical system is condensed at a position near the front or rear focal point of the test optical element. 5. An optical element inspection apparatus according to claim 4, wherein said convex lens system constituting said incident optical system is a zoom lens. 6. The apparatus according to claim 4, wherein a beam splitter is arranged between said taking lens and said spatial filter, and a photoelectric element for monitoring a state of a light beam emitted from said optical element to be inspected is arranged. Optical element inspection device. 7. An optical element inspection apparatus according to claim 6, wherein said monitor photoelectric element is arranged near a focal position of said taking lens. 8. The optical element inspection apparatus according to claim 7, wherein the position of the incident optical system or the position of the test optical element is adjusted based on the output of the monitor photoelectric element. 9. An optical element inspection apparatus according to claim 2, wherein the shape of said spatial filter is variable.