JP3365881B2 - Lens refractive index inspection device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens refractive index inspecting apparatus for inspecting the refractive index of an optical lens.

[0002]

2. Description of the Related Art In recent years, a molded lens made of a plastic material has been widely used as an optical lens used in an optical device such as a laser printer or a camera. This plastic molded lens is excellent in manufacturability of an aspherical lens and cheaper than a glass-polished lens, but it is difficult to stabilize the refractive index in manufacturing.

Conventionally, as a method of measuring the refractive index of an optical lens, a method of measuring a refraction angle by a V-block method using a precision differential refractometer or the like to obtain a refractive index, a Fizeau interferometer, or a Maha Zehnder A method has been used in which the transmitted wavefront is measured by analyzing an interference fringe image using an interferometer or the like and the refractive index is obtained.

[0004]

As described above, the conventional method for inspecting the refractive index of an optical lens requires high precision processing into a predetermined shape, and the optical lens to be inspected must be destroyed. did not become.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a lens refractive index inspecting device which can be easily inspected without destroying the refractive index of an optical lens.

[0006]

Means adopted by the present invention for solving the above-mentioned problems will be described. A device for inspecting the refractive index of a lens, which comprises a light source for emitting light, a collimating optical system for collimating the light emitted from the light source, and an image for forming a light beam output from the collimating optical system. An optical system, a cell in which a liquid having a refractive index substantially equal to the refractive index of a lens, which is an object to be inspected, is inserted between the collimating optical system and the imaging optical system, and a light beam output from the imaging optical system. And an image forming position detecting means for detecting an image forming distance difference between a case where a lens which is an object to be inspected is inserted in the cell and a case where the lens is not inserted.

Further, the light source for emitting the light is composed of a laser diode for emitting a single light. Further, the output light surface of the cell is constituted by one surface of the image forming optical system. Further, the image forming position detected by the image forming position detecting means is detected by the double knife edge method.

[0008]

The light emitted from the light source becomes parallel rays in the collimating optical system, passes through the liquid having a refractive index almost equal to the refractive index of the lens of the object in the cell, and is condensed by the imaging optical system. Form an image.

The image forming position detecting means measures and outputs the length of the image forming position when the lens as the object to be inspected is inserted into the cell and when it is not inserted. When the refractive index of the liquid in the cell and the refractive index of the lens of the test object inserted in the cell are equal, the difference in the image forming distance output from the image forming position detecting means becomes 0, and when the refractive index is different, The difference in imaging distance corresponding to the difference in refractive index is output to inspect the refractive index of the lens.

As the light source, a laser diode which emits a single light is used. Further, the output light surface of the cell is constituted by one surface of the image forming optical system. Further, the image formation position detecting means detects the image formation position by the double knife edge method. As described above, the light emitted from the light source is made into parallel rays, and a liquid having a refractive index almost equal to the refractive index of the lens of the test object is passed through,
The transmitted light is imaged by the imaging optical system, and the difference in the imaging distance between when the lens of the test object is inserted into the liquid and when it is not inserted is output. However, the refractive index can be easily inspected without breaking.

Further, by immersing the lens to be inspected in a matching liquid having substantially the same refractive index, the inspection can be performed without being affected by the surface shape or surface accuracy error. Also,
Since the light source is a laser diode that emits a single light,
Since the number of image forming points is one, the image forming position can be accurately measured.

Further, since the output light surface of the cell is constituted by one surface of the image forming optical system, the number of optical components is reduced and the size is reduced, and the light attenuation is reduced to detect the image forming position. The sensitivity can be increased. Further, since the image formation position is detected by using the double knife edge method, it is possible to detect with high accuracy.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of an embodiment of the present invention. In FIG. 1, 10 is a light source that emits light, 11 is a collimating optical system that collimates the light emitted from the light source, 12 is a cell in which the matching liquid 13 is placed, and 14 is a connection that images the light beam that has passed through the matching liquid. It is an image optical system.

Further, 20 is a double knife edge, 21 is a motor for rotating the double knife edge 20, 22 is a stage for moving the double knife edge 20 in the optical axis direction, 23 is a light receiving element, and 24 is an imaging distance difference output. The image forming position detecting section. An optical flat 12a is used for the surface of the cell 12 on which parallel rays are incident from the collimating optical system, and one surface of the imaging optical system 14 is used for the emitting surface so that the matching liquid 13 does not flow out.

As the matching liquid in the cell 12, a liquid having a refractive index almost equal to that of the lens 15 of the object to be tested is used. By thus immersing the lens 15 in the matching liquid 13 having almost the same refractive index, it is possible to eliminate the influence of the surface shape of the lens and the surface accuracy error.

As shown in FIG. 2 (A), the double knife edge 20 is composed of discs 20-1 and 20-2, and knife edges 20a and 20b for blocking the passage of light are recorded, and the double knife edge 20 is recorded as shown in FIG. As shown in B), they are installed in parallel at a certain distance. Also, the double knife edge 20 is
The position where the light passing through the image forming optical system 14 forms an image is installed between the knife edges 20a and 20b,
It is rotated by the motor 21.

The disks 21 and 2 are driven by the motor 21.
When the 0-2 rotates and the light rays received by the light receiving element 23 by the knife edges 20a and 20b are shielded as shown in FIG. 2 (B), the output of the light receiving element 23 is as shown in FIG. 2 (C). Output decreases. Image position is knife edge 2
When located at the center of 0a and 20b, the output reduction value of the light receiving element 23 due to the light shielding of the knife edges 20a and 20b becomes the same value, but when it is not located at the center, FIG.
As shown in FIG.

That is, the image forming position is the knife edge 20a.
If it is on the left side of the intermediate point between 20 and 20b, the shading of the knife edge 20a is larger than the shading of the knife edge 20b. The imaging position detector 24 detects the peak value of the output from the light receiving element 23, and when the peak value of the knife edge 20a is larger than the knife edge 20b, the stage 22 is detected as shown in FIG. To move the double knife edge 20 to the left, so that the peak value becomes equal.
Move 2 and record equal positions.

Next, as shown in FIG. 1, the matching liquid 1
The lens 15, which is the object to be inspected, is inserted into the lens 3. Lens 1
When the refractive index of 5 is equal to the refractive index of the matching liquid 13, the image forming position recorded by the image forming position detecting unit 24 does not change. , The light is refracted and the imaging position is different. Imaging position detector 2
4 outputs this difference.

If the distance difference output from the imaging position detector 24 is larger than a certain value, the refractive index of the lens is judged to be out of the standard. The distance difference value to be determined may be obtained in advance using lenses having different refractive indexes, or may be calculated.

Further, the distance difference is previously obtained for lenses having different refractive indexes, the lens of the object to be inspected is inserted into the matching liquid to output the distance difference, and the lens difference of the object to be inspected is output from the output distance difference. The refractive index can also be obtained. A laser diode that emits a single light may be used as the light source 10 of the embodiment. By using such a laser diode, the number of image forming points becomes one, and an accurate image forming position can be obtained.

[0022]

As described above, according to the present invention, the following effects can be obtained. The light emitted from the light source is made into parallel rays, and the liquid having a refractive index almost equal to the refractive index of the lens of the test object is passed through, and the passed light is imaged by the imaging optical system, and the test object is immersed in the liquid. Since the difference in the imaging distance between when the lens is inserted and when the lens is not inserted is output, the refractive index can be easily inspected without destroying the lens of any shape.

Further, by immersing the lens to be inspected in the matching liquid having substantially the same refractive index, it is possible to perform the inspection without being affected by the surface shape or surface accuracy error. Also,
Since the light source is a laser diode that emits a single light,
Since the number of image forming points is one, the image forming position can be accurately measured.

Further, since the output light surface of the cell is constituted by one surface of the image forming optical system, the number of optical components is reduced and the size is reduced, and the light attenuation is reduced to detect the image forming position. The sensitivity can be increased. Further, since the image formation position is detected by using the double knife edge method, it is possible to detect with high accuracy.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a double knife edge according to the same embodiment.

[Explanation of symbols]

10 light sources 11 Collimating optical system 12 cells 13 Matching liquid 14 Imaging optical system 15 lenses 20 double knife edge 20a, 20b knife edge 21 motor 22 stages 23 Light receiving element 24 Image formation position detector

Claims (4)

(57) [Claims] 1. A device for inspecting the refractive index of a lens, comprising: a light source that emits light; a collimating optical system that collimates the light emitted from the light source; and a light beam output from the collimating optical system. An image forming optical system for forming an image; a cell in which a liquid having a refractive index substantially equal to a refractive index of a lens as a test object is inserted between the collimating optical system and the image forming optical system; An image forming position detecting unit that detects a difference in image forming distance of a light beam output from the cell when a lens that is a test object is inserted into the cell and when the lens is not inserted into the cell. Refractive index inspection device. 2. The lens refractive index inspection device according to claim 1, wherein the light source for emitting the light is a laser diode for emitting a single light. 3. The output light surface of the cell is constituted by one surface of the imaging optical system.
Alternatively, the lens refractive index inspection device according to the item 2. 4. The refractive index inspection of a lens according to claim 1, wherein the image forming position detected by said image forming position detecting means is detected by a double knife edge method. apparatus.