JP2001091404A - Lens characteristic inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically measure and inspect a characteristic and an aberration of a lens in a short time with high precision by means of a simple structure without depending on any visual inspection by a worker. SOLUTION: A laser oscillating means 2 radiates a laser beam in the optical axis direction of a tested lens 1 to the tested lens 1, and an image of the laser beam transmitted through the tested lens 1 and focused on a cover glass 5 is expanded by means of a microscope 6 so as to be converted into an image signal by means of a camera 7. On the basis of the image data of the image signal inputted via an image storing means 8, a stage controlling means 9 moves the tested lens l via an XYZ gonio-stage 4 and a lens base 3 so as to control it for collecting the laser beams transmitted through the tested lens 1 on a single point. A length ratio computing measuring means 10 detect the center of gravity of the focused image and stores the length of the images focused around the center of gravity for storing a maximum length L and a minimum length S so as to measure a length ratio between L and S, and then, multiplies the length ratio by a fixed coefficient for computing a dimension of a non-point aberration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens characteristic inspection apparatus for inspecting the characteristics of a lens used for an optical pickup, a video camera or the like.

[0002]

2. Description of the Related Art FIG.
As shown in FIG.

In FIG. 12, reference numeral 1 denotes a test lens, 2 denotes a laser oscillation means used as a light source, 3 denotes a lens base for holding the test lens 1, and 4 denotes a height that allows the test lens 1 to freely rotate in the vertical and horizontal directions. An XYZ gonio stage that moves with high precision, 5 is a cover glass that receives laser light transmitted through the lens 1 to be inspected, 6 is a microscope that enlarges a condensed image, and 7 is a camera that captures an image from the microscope 6 and outputs a video signal. , 18 are binarizing means for binarizing the video signal from the camera 7 to make it easy to see the condensed image, and 19 is a monitor TV for displaying the video from the binarizing means 18.

The operation of the conventional lens characteristic inspection apparatus having the above configuration will be described below with reference to the drawings.

[0005] First, the test lens 1 is set on the lens base 3. Next, the XYZ gonio stage 4 is moved while watching the monitor TV 19, so that the laser light transmitted through the lens 1 to be measured is adjusted so as to converge at one point. Next, the shape of the focused image at that time is visually observed and stored. Next, the test lens 1 is moved up and down by a fixed amount, and the shape of the converged image in a vertically defocused state is visually observed and stored.

Normally, in the case of a lens having no aberration, a converged image has a perfect circular shape. Therefore, it was determined that there was no aberration if the shape did not change in the state of defocusing up and down.

For example, when the shape of an image condensed in a vertically defocused state changes to an ellipse, it has been determined that there is astigmatism. Further, when the size of the circle of the condensed image changes in a vertically defocused state, it is determined that there is spherical aberration.

[0008]

However, as described above, the conventional lens characteristics inspection apparatus is difficult to quantify the inspection due to the visual sensory inspection by the inspector, and the performance of the inspector deteriorates due to individual differences and fatigue. Has caused variations in inspection accuracy. In addition, the cost was increased due to the inspection by the inspector. In addition, since the converged image is affected by aberrations and characteristics of the microscope and the camera, it is impossible to measure only aberrations and characteristics of the lens to be inspected.

The present invention has been made in consideration of the above circumstances, and has as its object to provide an apparatus which can measure the characteristics of a test lens quantitatively with a simple configuration.

[0010]

In order to solve this problem, a lens characteristic inspection apparatus according to the present invention comprises a light source for irradiating a lens with light, a stage for holding the lens and moving the lens in all directions, and Imaging means for capturing an image of transmitted light from the lens disposed on the opposite side of the light source with respect to the lens and outputting a video signal; and outputting the image signal based on the shape and brightness of the collected image. Characteristic calculation means for calculating and measuring characteristics.

Further, the lens characteristic inspection apparatus of the present invention is characterized in that the magnitude of astigmatism is measured by calculating and measuring the length-to-length ratio of a converged image.

Further, the lens characteristic inspection apparatus of the present invention divides the focused image into four parts around the center of gravity, adds the areas of the parts facing each other, and measures the magnitude of astigmatism from the ratio. It is characterized by.

The lens characteristic inspection apparatus of the present invention is characterized in that the degree of astigmatism is measured by calculating and measuring the circularity of the condensed image.

Further, the lens characteristic inspection apparatus of the present invention is characterized in that the magnitude of spherical aberration is measured from a change in the amount of light of a condensed image when defocusing is performed in the optical axis direction at regular intervals.

Further, the lens characteristic inspection apparatus of the present invention is characterized in that the magnitude of spherical aberration is measured from a change in the area of a converged image when defocusing is performed in the optical axis direction at regular intervals.

Further, the lens characteristic inspection apparatus according to the present invention is characterized in that the presence or absence of a characteristic defect is determined from the light quantity at the central part of the focused image and the light quantity at the peripheral part.

Further, the lens characteristic inspection apparatus according to the present invention is characterized in that the measured aberration value uses a previously measured aberration or characteristic value of a microscope or a camera as a correction value.

Hereinafter, description will be made based on an embodiment of the present invention.

[0019]

(Embodiment 1) FIG. 1 is a block diagram showing a configuration of a lens characteristic inspection apparatus according to Embodiment 1 of the present invention.

In FIG. 1, reference numeral 1 denotes a test lens for measuring characteristics, 2 denotes a laser oscillating means for irradiating the test lens 1 with laser light from the optical axis direction of the test lens 1, and 3 holds the test lens 1. 4 is an XYZ gonio stage that has a hollow inside and moves the test lens 1 freely and precisely in the up, down, left and right rotation directions, 5 is a cover glass that receives laser light transmitted through the test lens 1, Reference numeral 6 denotes a microscope for enlarging an image condensed on the cover glass 5, reference numeral 7 denotes a camera which captures an image of the microscope 6 and outputs a video signal, reference numeral 8 denotes an image storage means for storing and holding a video signal from the camera, and reference numeral 9 denotes an XYZ gonio. Stage control means 10 for moving the stage 4 and controlling the laser light transmitted through the lens 1 to be focused to condense.
Is a ratio measurement means for measuring the magnitude of astigmatism by calculating and measuring the length ratio of the condensed image. 11 is a collection and calculation result calculated by the characteristic calculation measurement means 9 and a collection stored in the image storage means 8. Display means for displaying information such as a lighted image.

FIG. 2 is a diagram for explaining the calculation algorithm of the length-to-short ratio calculation and measurement means 9.

In FIG. 2, the left figure is an enlarged view of a focused image without astigmatism, and the right view is an enlarged view of a focused image with astigmatism. L indicates the maximum length, and S indicates the minimum length. As can be seen from the left diagram, L ÷ S = 1 when there is no aberration. However, when there is astigmatism, L ÷ S> 1. L ÷ S is larger than 1 as the astigmatism increases. Therefore, the magnitude of astigmatism can be measured by calculating and measuring the length-to-length ratio.

The operation of the apparatus for inspecting lens characteristics according to the first embodiment configured as described above will be described below with reference to the drawings.

First, the test lens 1 is set on the lens base 3. Next, the laser oscillation means 2 irradiates the test lens 1 with laser light from the optical axis direction of the test lens 1. next,
An image in which the laser beam transmitted through the lens 1 to be measured is condensed by the cover glass 5 is enlarged by the microscope 6 and converted into a video signal by the camera 7. Next, based on the image data of the video signal input through the image storage unit 8, the stage control unit 10
The test lens 1 is moved via the XYZ gonio stage 4 and the lens mount 3, and the laser light transmitted through the test lens 1
It is controlled so as to converge on a point. Next, the length-to-short ratio calculating and measuring means 9 detects the center of gravity of the condensed image, then sequentially measures the length of the condensed image around the center of gravity, and stores the maximum length L and the minimum length S. Next, L ÷ S is calculated to measure the length ratio. Next, the magnitude of astigmatism is calculated by multiplying the ratio by a fixed coefficient. Next, the result is displayed on the display unit 11.

With this series of operations, the presence or absence and size of astigmatism can be measured at high speed and with high accuracy.

(Embodiment 2) FIG. 3 is a block diagram showing the configuration of a lens characteristic inspection apparatus according to Embodiment 2 of the present invention. The same blocks as those described with reference to FIG. And the description is omitted.

In FIG. 3, reference numeral 12 denotes an area calculating and measuring means for dividing the condensed image into four parts around the center of gravity, adding the areas of the parts facing each other, and measuring the magnitude of astigmatism from the difference. .

FIG. 4 is a view for explaining the calculation algorithm of the area calculation and measurement means 12.

In FIG. 4, the left diagram is an enlarged image diagram of a converged image without aberration, and the right diagram is an enlarged image diagram of a condensed image with astigmatism.

The operation of the lens characteristic inspection apparatus according to the second embodiment configured as described above will be described below with reference to the drawings.

As can be seen from the right diagram of FIG. 4, when there is no aberration, (+)-(+) = 0. However, when there is astigmatism, (+) − (+)> 0. The value becomes larger than 0 as the astigmatism increases.

The area calculating and measuring means 12 divides the area into four parts around the center of gravity, adds the areas of the parts facing each other, and calculates the difference. Next, the magnitude of astigmatism is calculated by multiplying the area difference by a constant coefficient. Next, the result is displayed on display means 1.
1 is displayed.

By this series of operations, the presence or absence and size of astigmatism can be measured at high speed and with high accuracy.

The following method will be described as an example of the method of calculating the area in the image calculation / measurement means 12. The image data held in the memory etc.
Scans pixel by pixel. Normally, an image condensed in black (value 0) in the background becomes white (a value larger than 0). Therefore, a pixel having a value larger than a certain value in each pixel data is determined to be a part of the condensed image. I do. Therefore, the area can be calculated by counting the number of pixels having a value larger than a certain value from the total number of pixels.

(Embodiment 3) FIG. 5 is a block diagram showing a configuration of a lens characteristic inspection apparatus according to Embodiment 3 of the present invention. The same reference numerals as those described with reference to FIG. And the description is omitted.

In FIG. 5, reference numeral 13 denotes a circularity calculating and measuring means for calculating and measuring the circularity of the condensed image, and measuring the magnitude of astigmatism from the circularity.

The operation of the lens characteristic inspection apparatus according to the third embodiment having the above-described configuration will be described below with reference to the drawings. Generally, the circularity is

[0038]

(Equation 1)

Is represented by

In the case of a perfect circle,

[0041]

(Equation 2)

Is as follows.

As the astigmatism increases, the ellipse becomes more elliptic, so that the circularity is smaller than 1. Therefore, the circularity calculation / measurement unit 13 calculates and measures the area and the perimeter of the collected image, and then calculates and measures the circularity based on (Equation 1). Next, the magnitude of astigmatism is calculated by multiplying the calculated circularity by a constant coefficient. Next, the result is displayed on the display unit 11.

By this series of operations, the presence or absence and size of astigmatism can be measured at high speed and with high accuracy.

(Embodiment 4) FIG. 6 is a block diagram showing a configuration of a lens characteristic inspection apparatus according to Embodiment 4 of the present invention, wherein the same blocks as those described with reference to FIG. And the description is omitted.

In FIG. 6, reference numeral 14 denotes a light amount calculating and measuring means for calculating and measuring the light amount of the condensed image and measuring the magnitude of the spherical aberration from the change in the light amount.

FIG. 7 is a diagram showing a change in the amount of light with and without spherical aberration.

The operation of the lens characteristic inspection apparatus according to Embodiment 4 configured as described above will be described below with reference to the drawings.

As can be seen from FIG. 7, when there is no spherical aberration, the change in the amount of light of the focused image when the focus position is moved up and down changes sharply, whereas when there is spherical aberration, the focus position changes. The change in the light amount of the converged image when moving up and down gradually changes. The larger the spherical aberration, the gentler the spherical aberration. Also, as the spherical aberration increases, the maximum luminance value decreases.

The stage control means 9 moves the test lens 1 via the XYZ gonio stage 4 and the lens mount 3 to move the focus position up and down. The light amount measuring means 14 measures and stores the light amount of the converged image at each focus position.
Next, the relationship between the stored light amounts at each focus position is approximated by a function, and the magnitude of the spherical aberration is calculated by multiplying the coefficient of the function by a constant coefficient. Next, the result is displayed on the display unit 11.

By this series of operations, the presence or absence and size of spherical aberration can be measured at high speed and with high accuracy.

(Embodiment 5) FIG. 8 is a block diagram showing a configuration of a lens characteristic inspection apparatus according to Embodiment 5 of the present invention. The same reference numerals are used for the same blocks as those described with reference to FIG. And the description is omitted.

In FIG. 8, reference numeral 15 denotes an arithmetic operation for measuring the amount of light of the condensed image, measuring the area of a portion of the condensed image having a certain amount of light or more, and measuring the magnitude of the spherical aberration from the change in the area. This is a light amount area calculation and measurement unit.

FIG. 9 is a diagram showing a change in the area over a certain amount of light with and without spherical aberration.

The operation of the apparatus for inspecting lens characteristics according to Embodiment 4 configured as described above will be described below with reference to the drawings.

As can be seen from FIG. 9, when there is no spherical aberration, when the focus position is moved up and down, the change in the area of the condensed image exceeding a certain amount of light changes sharply.
When there is spherical aberration, the change in the area of the condensed image over a certain amount of light when the focus position is moved up and down gradually changes. The larger the spherical aberration, the gentler the spherical aberration. Also, the larger the spherical aberration, the smaller the area.

The stage control means 9 moves the test lens 1 via the XYZ gonio stage 4 and the lens mount 3 to move the focus position up and down. The light quantity area measuring means 15 measures and stores the area of the condensed image at each focus position having a certain luminance or more. Next, the relationship between the stored areas at each focus position is approximated by a function, and the coefficient of the function is multiplied by a constant coefficient to calculate the magnitude of the spherical aberration. Next, the result is displayed on the display unit 11.

By the series of operations, the presence or absence and size of spherical aberration can be measured at high speed and with high accuracy.

(Embodiment 6) FIG. 10 is a diagram showing a change in light amount when there is a characteristic failure.

The operation of the apparatus for inspecting lens characteristics according to Embodiment 6 configured as described above will be described below with reference to the drawings. The configuration diagram in the present embodiment is an embodiment in which the light quantity calculation / measurement unit 14 in FIG.

In FIG. 10, the upper part is an image of a converged image, and the lower part is a change in the amount of light when the image is scanned in the horizontal direction. When there is no characteristic failure, the light quantity at the center is large and the light quantity at the periphery is small. On the other hand, when there is a characteristic defect, the light amount at the center is not so large and the light amount at the periphery is large.

The light quantity calculation and measurement means 14 calculates and measures the change in the light quantity in the central part and the peripheral part. Then, the light quantity ratio between the central part and the peripheral part and the light quantity value at each part are calculated and measured. Next, the predetermined value is compared with the calculated value to determine whether the characteristics are good or not. Next, the result is displayed on the display means 11. By this series of operations, the presence or absence of the characteristic defect can be measured at high speed and with high accuracy.

(Embodiment 7) FIG. 11 is a block diagram showing a configuration of a lens characteristic inspection apparatus according to Embodiment 7 of the present invention. The same blocks as those described with reference to FIG. And the description is omitted.

In FIG. 11, reference numeral 16 denotes a characteristic operation measuring means for measuring the characteristics and aberration of the lens from information such as the shape and brightness of the converged image.

Reference numeral 17 denotes a characteristic data storage unit that stores data of optical aberrations and characteristics of the microscope 6 and the camera 7 in advance.

The operation of the lens characteristic inspection apparatus according to Embodiment 7 configured as described above will be described below with reference to the drawings.

The characteristic calculating means 16 measures the characteristics and aberration of the lens from information such as the shape and brightness of the converged image. Next, data of optical aberrations and characteristics of the microscope 6 and the camera 7 stored in the characteristic data storage unit 17 are read in advance, and the measured characteristics and aberration results are corrected. Next, a specific correction method for the data stored in the characteristic data storage unit 17 will be specifically described with reference to FIG. If the inspection machine (microscope or camera) has astigmatism, L ÷ S = 1 will not be obtained even if a test lens having no aberration is measured.
Therefore, L ÷ S of the test lens having no aberration is measured in advance. If the value is 1.2, it is the value of astigmatism of the inspection machine. Therefore, this value is stored in the characteristic data storage unit 17. Next, when the actually measured value is 1.5, the astigmatism of only the test lens is 1.5 (actual value) ÷ 1.2 (correction value) = 1.25. Only the aberration value of 1.25 can be calculated and measured. The corrected characteristics and aberration results corrected as described above are displayed on the display unit 11.

By this series of operations, the optical aberrations and characteristics of the microscope and the camera can be canceled, and the aberrations and characteristics of only the lens to be measured can be measured at high speed and with high accuracy.

[0069]

As described above, according to the lens characteristic inspection apparatus of the present invention, the characteristics and aberration of the lens can be measured at high speed and with high accuracy without performing the visual inspection by the operator. In addition, since the measurement result can be digitized, it can be used as a shipping inspection device for quality judgment. In addition, since aberrations and characteristics of the inspection machine itself such as a microscope and a camera can be corrected, high-speed and high-precision measurement of aberrations and characteristics of only the lens to be inspected is possible.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a lens characteristic inspection device according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining an arithmetic algorithm of a length-to-short ratio arithmetic measuring unit 9 according to the first embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a lens characteristic inspection device according to a second embodiment of the present invention.

FIG. 4 is a diagram for explaining a calculation algorithm of an area calculation measurement unit 12 according to the second embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a lens characteristic inspection device according to a third embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a lens characteristic inspection device according to a fourth embodiment of the present invention.

FIG. 7 is a diagram showing a change in the amount of light with and without spherical aberration according to the fourth embodiment of the present invention.

FIG. 8 is a block diagram showing a configuration of a lens characteristic inspection device according to a fifth embodiment of the present invention.

FIG. 9 is a diagram showing a change in an area of a certain light amount or more with and without spherical aberration in a fifth embodiment of the present invention.

FIG. 10 is a diagram showing a change in the amount of light when there is a characteristic failure according to the sixth embodiment of the present invention.

FIG. 11 is a block diagram showing a configuration of a lens characteristic inspection device according to a seventh embodiment of the present invention.

FIG. 12 is a block diagram showing a configuration of a conventional lens characteristic inspection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Test lens 2 Laser oscillation means 3 Lens stand 4 XYZ gonio stage 5 Cover glass 6 Microscope 7 Camera 8 Image storage means 9 Stage control means 10 Length ratio calculation means 11 Display means 12 Area calculation measurement means 13 Roundness calculation measurement means 14 Light intensity calculation / measurement means 15 Light intensity area calculation / measurement means 16 Characteristic calculation / measurement means 17 Characteristic data storage means 18 Binarization means 19 Monitor TV

Claims (8)

[Claims] 1. A light source for irradiating light to a lens, a stage for holding and moving the lens in all directions, and a transmitted light from the lens disposed on a side opposite to the light source with respect to the lens. A lens characteristic test comprising: imaging means for imaging a condensed image and outputting a video signal; and characteristic calculation measuring means for calculating and measuring a characteristic of the lens from the shape and brightness of the condensed image. apparatus. 2. A lens characteristic inspection apparatus according to claim 1, wherein the magnitude of astigmatism is measured by calculating and measuring a length-to-length ratio of the converged image. 3. The method according to claim 1, wherein the converged image is divided into four parts around the center of gravity, the areas of the parts facing each other are added, and the magnitude of astigmatism is measured from the difference or ratio.
The lens characteristic inspection apparatus according to the above. 4. The lens characteristic inspection apparatus according to claim 1, wherein the magnitude of astigmatism is measured by calculating and measuring the circularity of the collected image. 5. The lens characteristic inspection apparatus according to claim 1, wherein the magnitude of spherical aberration is measured from a change in the amount of light of a converged image when defocusing is performed in the optical axis direction at regular intervals. 6. The lens characteristic inspection apparatus according to claim 1, wherein the magnitude of the spherical aberration is measured from a change in the area of the converged image when defocusing is performed in the optical axis direction at regular intervals. 7. The lens characteristic inspection apparatus according to claim 1, wherein the presence / absence of a characteristic defect is determined based on the amount of light in the central portion and the amount of light in the peripheral portion of the collected image. 8. The lens characteristic inspection apparatus according to claim 1, wherein the measured aberration value is corrected based on a previously measured aberration value of the imaging unit.