JP3437479B2 - Birefringence measurement 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 birefringence measuring device, and more particularly, to a birefringence for evaluating a plastic lens such as an optical writing lens for a laser printer, a camera lens, a lens for an optical pickup. The present invention relates to a birefringence measuring device for measuring.

[0002]

2. Description of the Related Art As a conventional method for measuring the birefringence of a plastic lens of this type, a phase modulation method, a rotation analyzer method and the like are known. In these methods, a transparent beam is irradiated onto a lens to be inspected, the transmitted light is received by a light receiving element such as a photodiode, and the polarization state of the transmitted light is changed by birefringence of the lens to be inspected. By detecting, the birefringence of the lens to be inspected is measured.

Particularly, in the phase modulation method, the irradiation light is phase-modulated using a photoelastic modulator, and the birefringence is obtained from the phase difference between the beat signal and the modulation signal of the light transmitted through the lens to be tested. In the rotating analyzer method, the transmitted light is received by the light receiving element installed after the analyzer while rotating the analyzer installed after the lens to be inspected, and the output from the light receiving element changes with the rotation of the analyzer. It seeks refraction.

Further, as another measuring method, a birefringence is obtained in which a magnified parallel light is applied to a lens to be inspected and the transmitted light is received by a two-dimensional sensor such as a CCD camera to obtain birefringence of the lens to be inspected. There are surface measurement methods described in Japanese Patent Application Laid-Open No. 4-58138, Japanese Patent Application Laid-Open No. 6-147986, and Japanese Patent Application Laid-Open No. 7-77490.

[0005]

However, in the former phase modulation method and rotation analyzer method, for example, in so-called point measurement, in which a thin parallel beam is applied to the lens to be detected and is received by a photodiode. Therefore, in order to measure the entire surface of the lens to be inspected, it is necessary to adjust the lens to be inspected and the measuring device, and when measuring a spherical surface or an aspherical lens (non-parallel plate) that is not a flat surface, I had a problem that the setting was difficult.

Further, in the latter surface measuring method, since the surface measurement is performed, it is not necessary to adjust the lens to be inspected, but a lens having a large aperture such as a lens for optical writing or the NA of the lens is used. When the value is large, the difference in refraction between the central part and the peripheral part of the lens becomes large, and optical distortion occurs in the transmitted image, which causes a problem that the measured value and the position on the lens under test cannot be matched. Will occur.

Further, the light rays transmitted through the peripheral portion of the lens to be inspected are overlapped with each other, or the light rays transmitted through the peripheral portion are not vignetted in the optical system path to the light receiving element and do not reach the light receiving element. There has been a problem that a portion corresponding to the peripheral portion of the lens to be inspected becomes a shadow.

That is, it was not possible to accurately measure the birefringence over the entire surface of the lens to be inspected.

Further, in order to accurately measure the birefringence over the entire surface of the lens, it is necessary that the peripheral edge portion and the central portion of the lens to be inspected and the light receiving element have a substantially image forming relationship. The reason is that if such an imaging relationship is not established, an image of the lens under test that is out of focus (out of focus) will be obtained, so the portion corresponding to the periphery of the lens under test is observed thick. I don't know where is the edge,
In addition, when there are slight scratches or dust on the surface of the lens to be inspected, they are observed as thick and large and uneven light amount can occur in the transmitted image of the lens to be inspected, so the absolute value of the birefringence phase difference measured and This is because it causes an error in the distribution.

In particular, in the case of a lens having a large NA, the difference in the distance to the light receiving element (length in the optical axis direction of the optical system) between the central portion and the peripheral portion of the lens becomes large, and one portion is focused. In that case, the degree of out-of-focus of the other portion becomes severe, and the measurement error due to it becomes large.

Here, in order to make the vicinity of the surface of the lens to be inspected and the light receiving element have a substantially image-forming relationship, the distance between the image-forming optical systems may be varied to perform the focusing adjustment. , The magnification of the imaging optical system varies depending on the location where the lens is measured, and the size of the image of the lens varies, so when trying to grasp the distribution of birefringence over the entire surface of the lens, the birefringence distribution of the measurement result It takes a long time to process the image as a two-dimensional image by enlarging or reducing it, and since the data is processed, the reliability of the measured value also decreases.

Therefore, according to the present invention, the birefringence can be measured with high accuracy over the entire surface of the lens to be inspected, the measurement time is increased by processing the measurement result, and the reliability of the measured value is lowered. An object of the present invention is to provide a birefringence measuring device capable of preventing the above.

[0013]

The invention according to claim 1 is
In order to solve the above problems, a light source, a first polarization unit that changes the light emitted from the light source into a predetermined polarization state, and a light beam that is polarized by the first polarization unit are diverged or converged. An irradiation optical system that is incident on the lens to be inspected, a second polarization unit that is rotatably provided around the optical system, and that changes the polarization state of the light that has passed through the lens to be inspected at equal angles. Light receiving means for receiving the light transmitted through the second polarizing means, and light interposed between the second polarizing means and the light receiving means for transmitting the light passing through the second polarizing means on the light receiving surface of the light receiving means. A birefringence measuring apparatus comprising: an image forming optical system for forming an image; and a calculation means for calculating a birefringence of the lens to be inspected based on received light data received by the light receiving means at equal angles. Holds the image optical system and the light receiving unit as one A holding member, a holding member control means for moving the holding member in the optical axis direction of the optical system and a direction substantially orthogonal to the optical axis direction, and an input means for inputting thickness data of the lens surface to be tested in the depth direction. Based on the thickness data input from the input unit, the holding member control unit always has a substantially image-forming relationship between the surface of the lens to be inspected facing the image forming optical system and the light receiving surface of the light receiving element. As described above, the holding member is integrally moved in the optical axis direction of the optical system and in a direction substantially orthogonal to the optical axis direction.

In this case, based on the thickness data of the lens to be inspected, the holding member is used as an optical system so that the vicinity of the surface of the lens to be inspected facing the imaging optical system and the light receiving surface of the light receiving element are always in a substantially image forming relationship. Since the birefringence of the lens to be measured is measured by integrally moving the lens in the optical axis direction and in a direction substantially orthogonal to the optical axis direction, the blurring of the measurement result regardless of the center portion and the peripheral portion of the lens is detected. The impact can be reduced.

Further, since the image forming optical system and the light receiving element are moved integrally with the lens to be inspected, the magnification of the image forming optical system can always be kept constant, and the birefringence of the entire surface of the lens to be inspected can be suppressed. It is not necessary to process the measurement results to know the distribution.

As a result, the birefringence can be measured with high accuracy over the entire surface of the lens to be inspected, and it is possible to prevent the measurement time from being increased and the reliability of the measured value from being lowered. can do.

Further, based on the thickness data of the lens to be inspected,
The holding member is integrated in the optical axis direction of the optical system and in a direction substantially orthogonal to the optical axis direction so that the vicinity of the surface of the lens to be tested facing the imaging optical system and the light receiving surface of the light receiving element are always in a substantially image forming relationship. Since the birefringence of the lens to be measured is measured by moving the lens automatically, the birefringence can be easily measured with a simple and low-cost device configuration.

Specifically, in order to maintain the image forming relationship between the entire surface of the lens to be inspected and the light receiving element, the light receiving element and the image forming optical system are moved in a direction orthogonal to the optical axis direction of the optical system to be inspected. It is necessary to move the light receiving element and the imaging optical system in the optical axis direction of the optical system so that the surface of the lens to be inspected is in focus each time the lens measurement location changes.

In this case, regarding the movement of the light receiving element and the imaging optical system, a detecting means for detecting the distance from the light receiving element to the surface of the lens to be inspected is separately provided, and the light receiving element is adjusted so that the distance becomes a predetermined amount. It is conceivable to move the image forming optical system and the image receiving optical element and the image forming optical system in a direction in which the defocus is improved while processing the image of the lens to be inspected picked up by the light receiving element to check the degree of defocus. It is also possible to move.

However, if a means for detecting the distance from the light receiving element to the surface of the lens to be inspected is provided, the apparatus structure becomes complicated and costly, and if image processing is performed, it takes time to perform the measurement. It takes a long time.

According to the first aspect of the present invention, the thickness data of the lens to be inspected is input in advance, and the vicinity of the surface of the lens to be inspected facing the imaging optical system and the light receiving surface of the light receiving element are always substantially based on the data. Since the holding member is integrally moved in the optical axis direction of the optical system and in a direction substantially orthogonal to the optical axis direction so as to form an image-forming relationship, the birefringence can be easily measured with a simple and low-cost device configuration. be able to.

In order to solve the above-mentioned problems, the invention of claim 2 irradiates a light flux parallel to the lens to be inspected between the lens to be inspected and the first polarizing element in the invention of claim 1. While providing a parallel optical system to provide a test lens control means for moving the test lens in a direction substantially orthogonal to the optical axis direction of the optical system, based on the thickness data input from the input means, The test lens control means is moved in a direction substantially orthogonal to the optical axis direction of the optical system so that the vicinity of the surface of the test lens facing the imaging optical system and the light receiving surface of the light receiving element always have a substantially imaging relationship. In addition, the holding member control means moves in the optical axis direction of the optical system.

This is done in order to obtain a measuring device which can easily and inexpensively realize highly accurate measurement of birefringence over the entire surface of the lens to be inspected.

The reason will be described below.

If the test lens has a long focal length and the diverging or converging light is applied to the test lens to collimate the transmitted light of the test lens, the measuring apparatus becomes large. Therefore, in such a case, the light to be radiated to the lens to be inspected is preliminarily collimated, and the parallel light is radiated to the lens to be inspected to prevent the measuring device from becoming large. Then, at that time, when measuring the entire surface of the lens to be inspected, the imaging optical system and the light receiving means are fixed without moving in a direction substantially orthogonal to the optical axis of the optical system, and instead, the lens to be inspected is optically moved. The entire surface of the lens to be inspected is observed while moving in a direction substantially perpendicular to the optical axis of the system.

According to a second aspect of the invention, the thickness data in the optical axis direction of the optical system of the lens to be inspected and the position in the direction substantially orthogonal to the optical axis of the optical system of the lens to be inspected (in the main scanning direction of the lens to be inspected). From the lens height data, the amount by which the imaging optical system and the light receiving means should move in the optical axis direction of the optical system is calculated, and the imaging optical system and the light receiving means are moved accordingly.

That is, while the imaging optical system and the light receiving means are moved in the optical axis direction of the optical system, and the lens under test is moved in a direction substantially orthogonal to the optical axis, an image is formed between the surface of the lens under test and the light receiving element. By measuring the entire surface of the lens to be inspected while maintaining the relationship, it is possible to obtain a measuring device that can inexpensively and easily realize highly accurate measurement of birefringence over the entire surface of the lens to be inspected. is there.

[0028]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to the drawings.

1 and 2 are views showing a first embodiment of a birefringence measuring apparatus according to the present invention.

First, the structure will be described. In FIG. 1, 1
Is a semiconductor laser (light source), and the linearly polarized light beam from the laser light source 1 is a λ / 4 plate (first polarizing means) 2
Is converted into circularly polarized light. This circularly polarized light is converted into divergent light by a lens (irradiation optical system) 3 having the same function as that of a microscope objective lens, and is then incident on a lens 4 to be inspected. Not held in the holder. As the lens 4 to be inspected, a plastic lens such as a lens for optical writing such as a laser printer, a camera lens, a lens for an optical pickup or the like is used.

Further, the lens 3 is mounted on a stage 5, a pinhole 6 acting as a spatial filter is mounted on the stage 5, and the stage 5 is driven by a stepping motor (not shown) to form an optical system. It is movable along the optical axis.

This stepping motor is provided with a rotation origin position sensor. The distance between the lens 3 and the lens 4 to be inspected is set to a known distance, and the state is set as the movement origin of the stage 5. It is possible to detect the change in the distance between the lens 3 and the lens 4 to be inspected due to the movement of the stage 5 by counting the number of pulses supplied to.

Further, the light transmitted through the lens 4 to be inspected is set to a position where the lens 3 satisfies the expression 1, that is, the lens 3 and the lens 4 to be inspected constitute an afocal system to form a parallel light beam. can do.

[Equation 1] Here, f0 is the focal length of the lens 3, f1 is the focal length of the lens 4 to be inspected, and Δ is the distance between the lens 3 and the lens 4 to be inspected.

Further, the light beam which has passed through the lens 4 to be inspected and has become elliptical polarized light close to circularly polarized light due to the birefringence of the lens 4 to be inspected is elliptical close to linearly polarized light by the λ / 4 plate (second polarizing means) 7. After being converted into polarized light, a polarizing plate (second polarizing means)
Polarized by 8 and further lens (imaging optical system) 9
The light is received (imaged) on the light receiving surface of the CCD camera (light receiving means) 10.

The lens 9 is adjusted to a position near the center (optical axis) of the lens 4 to be inspected and the CCD camera 10 so that a substantially image-forming relationship is established, and its material is like glass. The one in which the birefringence inside thereof is sufficiently removed is used.

Reference numerals 11 and 12 denote stepping motors for rotating the λ / 4 plate 7 and the polarizing plate 8 around the optical axis of the optical system. The motors 11 and 12 have rotation origin position sensors (not shown). The λ / 4 plate 7 and the polarizing plate 8 are provided by counting the number of pulses supplied to the motors 11 and 12.
The rotation angle of can be detected.

The motors 11 and 12 are driven by a motor driver 13.
Reference numeral 13 is adapted to drive the motors 11 and 12 by receiving a pulse from a pulse generator 15 which is driven based on a command signal from a computer (calculating means) 14.

The image data picked up by the CCD camera 10 is designed to be taken into the memory of the computer 14 through the image input device 16.
This image data and sensor from the rotation origin position sensor 1
The birefringence phase difference and the principal axis azimuth of the subject lens 4 are calculated based on the rotation angle information of 1 and 12.

On the other hand, the λ / 4 plate 7, the polarizing plate 8, the lens 9 and the CCD camera 10 are integrally held by a stage 17, and the stage 17 is driven by a motor driver 13 to drive an optical system by a stepping motor 18. It is designed to move in the optical axis direction. Also, stage 17 is stage 19
The stage 19 is driven by a stepping motor 21 driven by a motor driver 13 so as to move along the guide 20 in a direction substantially orthogonal to the optical axis of the optical system.

Further, the computer 14 has a keyboard (input means), and the thickness data in the depth direction (optical axis direction) of the lens 4 to be inspected is inputted from this keyboard.

The computer 14 controls the motors 18 and 21 by outputting a command signal to the motor driver 13 based on this thickness information, and the lens 4 to be inspected facing the lens 9
The stages 17 and 19 are moved in the optical axis direction of the optical system and in a direction substantially orthogonal to the optical axis direction so that the vicinity of the surface and the light receiving surface of the CCD camera 10 are always in a substantially image-forming relationship.

In this embodiment, the stages 17 and 19 form a holding member, and the computer 14, the motor driver 13 and the motors 18 and 21 form a holding member control means.

Next, the principle of the method for measuring the birefringence of the lens 4 under test will be described.

In this embodiment, the polarization direction of the semiconductor laser 1 is set to be horizontal with respect to the ground, and λ
The azimuth (transmission axis azimuth) of the / 4 plate 2 is set to 45 ° with respect to the horizontal direction on the ground, and the lens 4 to be inspected is irradiated with circularly polarized light.
The rotation origin in the measurement is when the azimuths of the / 4 plate 7 and the polarizing plate 8 are horizontal to the ground.

First, after the lens 4 to be inspected is set at a predetermined position by the holder, when linearly polarized light from the semiconductor laser 1 is irradiated, the linearly polarized light beam is converted into circularly polarized light by the λ / 4 plate 2 and circularly polarized. After the polarized light is converted into divergent light by the lens 3, it is incident on the lens 4 to be inspected.

Here, the stage 5 is moved in the optical axis direction of the optical system, and the distance between the lens 3 for irradiating the lens 4 to be inspected with divergent light and the lens 4 to be inspected is set to an optimum one.

Then, by the stepping motor 11, λ
When the azimuth of the / 4 plate 7 is rotated by 45 ° from the rotation origin, the polarizing plate 8 is rotated by (180 / n) ° from the rotation origin at equal angles, and the polarizing plate 8 is rotated by (180 / n) °. The light beam polarized by the polarizing plate 8 is transferred to the CCD by the lens 9.
By forming an image on the camera 10, image data is picked up by the CCD camera 10. Note that n is a predetermined measurement point.

This image data is loaded into the computer 14, the rotation angle data of the polarizing plate 8 and the n CCD cameras 10 are taken.
Get the image data of. Then, after returning the azimuth of the λ / 4 plate 7 to the origin of rotation, the polarizing plate 8 is rotated by (180 / n) ° from the origin of rotation in the same manner as described above, and the CCD is rotated.
The image data of the camera 10 is loaded into the computer 14 to obtain the rotation angle data of the polarizing plate 8 and the image data of n sheets.

Then, the computer 14 obtains the birefringence of the lens 4 to be inspected by the following arithmetic processing based on the acquired image data of 2 × n and the rotation angle data of the polarizing plate 8.

With the rotation of the polarizing plate 8 when the azimuth of the λ / 4 plate 7 is rotated by 45 ° from the rotation origin, the light intensity I45 detected by each pixel of the CCD camera 10 is given by the formula 2. .

[Equation 2] Further, when the azimuth of the λ / 4 plate 7 is returned to the rotation origin, the light intensity I0 detected by each pixel of the CCD camera 10 according to the rotation of the polarizing plate 8 is given by Expression 3.

[Equation 3] In Equations 2 and 3, θ is the principal axis azimuth of the polarizing plate 8, δ is the birefringence phase difference of the lens 4 to be inspected, and φ is the principal axis azimuth of the lens 4 to be inspected. Assuming that the phases of the light intensity change due to the rotation of the polarizing plate 8 are φ45 and φ0, respectively, φ45 and φ0 are expressed by Equation 4 and Equation 5 from Equations 2 and 3, respectively.

[Equation 4]

[Equation 5] Further, φ45 and φ0 are calculated by the equations 6 and 7 based on the captured image data of the CCD camera 10 and the rotation angle data of the polarizing plate 8.

[Equation 6]

[Equation 7] Therefore, the phase difference δ and the principal axis direction φ are obtained by the equations 8 and 9 by the equation 4, the equation 5, the equation 6, and the equation 7.

[Equation 8]

[Equation 9] Next, based on the above-described method of measuring birefringence, a method of measuring the birefringence of the lens 4 to be measured while moving the stages 17 and 19 based on the thickness data of the lens 4 to be measured in the depth direction will be described.

In the above-mentioned measurement of the birefringence of the lens to be inspected 4, the aerial image of the photoelastic interference fringes generated in the vicinity of the surface of the lens to be inspected 4 due to the birefringence of the lens to be inspected 4 shows the polarization plate 8. The CCD camera 10 captures an image through the divergent light, and the divergent light emitted to the lens 4 to be inspected is substantially collimated by the lens 4 to be inspected. It has substantially the same size (area) as the lens 4 to be inspected.

On the other hand, the λ / 4 plate 7 and the polarizing plate 8 constituting the measurement optical system are limited in size, and when the aperture of the lens 4 to be inspected is large, the photoelastic interference fringes cannot be transmitted at one time. Therefore, in that case, it becomes impossible to measure the birefringence over the entire surface of the lens 4 to be inspected.

Here, the aerial image of the photoelastic interference fringes may be once reduced and then transmitted through the λ / 4 plate 7 and the polarizing plate 8, but in that case, the optical system becomes complicated and expensive. Since the aerial image of the photoelastic interference fringes becomes small, the spatial resolution in the measurement deteriorates. Therefore, in the apparatus configuration of FIG. 1, a stage equipped with the polarizing plate 8 and the CCD camera 10
By moving 19 in a direction substantially orthogonal to the optical axis of the optical system, the aerial image of the photoelastic interference fringes having substantially the same size as the lens to be inspected is partially divided and observed by the CCD camera 10. Measure.

For example, as shown in FIG. 2, the stage 21 is moved by the motor 21 in a direction substantially orthogonal to the optical axis direction of the optical system so that the measured region of the lens 4 to be measured can be observed, and the phase difference and principal axis direction are changed. To measure. In the same manner, the measurement area and the stage 19 are moved with respect to the measurement area, and each measurement is performed.

At this time, in the measuring optical system, if the image forming relationship between the surface of the lens 4 to be inspected and the image forming surface of the CCD camera 10 is not established, the birefringence is measured over the entire surface of the lens 4 to be inspected with high accuracy. Can not do it.

Since the lens 4 to be inspected shown in FIG. 1 has a curvature on the surface facing the lens 9, the position of the surface of the lens 4 to be inspected is relative to the image pickup surface of the CCD camera 10 by the optical axis of the optical system. However, the image forming relationship between the vicinity of the surface of the lens 4 to be inspected and the image pickup surface of the CCD camera 10 is not established.

Therefore, in this embodiment, every time the stage 19 is moved in a direction substantially orthogonal to the optical axis of the optical system, the stage 17 is moved in the optical axis direction of the optical system to move the lens 4 to be inspected. An image forming relationship is established between the vicinity of the surface and the image forming surface of the CCD camera 10.

The method will be specifically described.

First, the depth and thickness data of the lens 4 to be measured is measured by a measuring device (not shown) and input to the input device. In this case, the thickness data of the lens 4 to be tested is given to the computer 14 by sampling the data of the curvature surface of the surface facing the lens 9 and inputting this data to the input device.

Based on this data, the computer 14 moves the stage 17 in the optical axis direction of the optical system each time the stage 19 is moved in the direction substantially orthogonal to the optical axis of the optical system. The following processing is performed.

The vicinity of the center of the lens 4 to be inspected (optical axis) is the origin of movement of the stage 19, and the amount of movement of the stage 19 is ± h. Further, when the radius of curvature of the surface of the lens 4 to be inspected facing the lens 9 is R, the surface of the lens 4 to be inspected becomes d in Equation 10 due to movement of the stage 19 in a direction substantially perpendicular to the optical axis of the optical system. It is displaced in the direction of the optical axis of the optical system by the indicated amount.

[Equation 10] Therefore, when the stage 19 moves by h in the direction substantially orthogonal to the optical system optical axis, the stage 17 is moved by d in the optical optical axis direction so that the lens 9 and the CCD camera 10 can be arbitrarily moved with respect to the lens 4 to be inspected. When it is moved to the position, the imaging relationship between the surface of the lens 4 to be inspected and the light receiving surface of the CCD camera 10 is established, so that accurate birefringence can be measured in the region to be measured.

In order to move the stage 17 in the optical axis direction of the optical system, instead of inputting the curved surface data of the lens 4 to be inspected as described above, the surface of the lens 4 to be inspected and the CCD camera 10 take an image. A means for detecting a change in the distance to the surface may be provided, and the detection information from this detection means may be input to the computer 14 to grasp the above-described amount of deviation, or the image captured by the CCD camera 10 may be out of focus. The stage 17 may be gradually moved by inputting the movement amount of the motor 18 from the keyboard so that the out-of-focus blur is eliminated while checking the degree.

As described above, in this embodiment, the lens 4 under test is
Based on the thickness data of the stages, the stages 17 and 19 are arranged in the optical axis direction and the optical axis of the optical system so that the vicinity of the surface of the lens 4 to be inspected facing the lens 9 and the light receiving surface of the CCD camera 10 are always in a substantially image forming relationship. Since the birefringence of the lens 4 to be measured is measured by integrally moving the lens 4 in a direction substantially orthogonal to the direction, the influence of defocus on the measurement result should be reduced regardless of the central portion and the peripheral portion of the lens 4. You can

Since the lens 9 and the CCD camera 10 are moved integrally with the lens 4 to be inspected, the lens 9
Can always be made constant, and it is not necessary to process the measurement result in order to know the distribution of birefringence over the entire surface of the lens 4 under test.

As a result, it is possible to measure the birefringence over the entire surface of the lens 9 to be measured with high accuracy, and to increase the measurement time by processing the measurement result and reduce the reliability of the measured value. Can be prevented.

Further, based on the thickness data of the lens 4 to be inspected, the vicinity of the surface of the lens 4 to be inspected facing the lens 9 and CC
The stages 17 and 19 are integrally moved in the optical axis direction of the optical system and in a direction substantially orthogonal to the optical axis direction so that the light receiving surface of the D camera 10 is always in a substantially image forming relationship. Since the birefringence is measured, the birefringence can be easily measured with a simple and low-cost device configuration.

Further, in this embodiment, the stage 5 is moved in the optical axis direction of the optical system, and the interval between the lens 3 for irradiating the lens 4 to be inspected with divergent light and the lens 4 to be inspected is set to an optimum one. Since the light flux passing through the lens to be inspected 4 can be made substantially parallel, the optical distortion is small, and the light to be transmitted through the peripheral edge of the lens to be inspected 4 is not overlapped or vignetting is small. It is possible to obtain a transmission image of 4 (photoelastic interference fringe image).

FIG. 3 shows a second embodiment of the birefringence measuring device according to the present invention.
It is a figure which shows embodiment. In the present embodiment, the first
The same configurations as those of the embodiment are denoted by the same reference numerals and the description thereof will be omitted.

In the present embodiment, as shown in FIG. 3, a lens (parallel optical system) 31 for irradiating a light beam parallel to the lens 4 to be inspected is interposed between the lens 3 and the lens 4 to be inspected, and
The lens 4 to be inspected is held by a stage 32, and the stage 32 is moved by a stepping motor 33 driven by a motor driver 13 in a direction substantially orthogonal to the optical axis direction of the optical system.

Then, the computer 14 determines the vicinity of the surface of the lens 4 to be inspected facing the lens 9 and the CCD camera 10 based on the thickness data of the lens 4 to be inspected inputted from the keyboard.
The stage 17 is moved in the optical axis direction of the optical system and the stage 32 is moved in a direction substantially orthogonal to the optical axis direction of the optical system so that the light receiving surface of the optical system is always in a substantially image-forming relationship.

In this embodiment, the computer 14,
The motor driver 13 and the motor 33 constitute a lens control unit to be inspected.

In this embodiment, the structure is as follows.
The reason is as follows.

When the focal length of the lens 4 to be inspected is long, the lens 4 to be inspected is irradiated with diverging or converging light and the lens 4 to be inspected
If the transmitted light is collimated, the measuring device becomes large. Therefore, in such a case, the light to be radiated to the lens 4 to be inspected is preliminarily collimated, and the parallel light is radiated to the lens 4 to be inspected, thereby preventing an increase in size of the measuring apparatus.
Then, at that time, when measuring the entire surface of the lens 4 to be inspected, the lens 9 and the CCD camera 10 are fixed without being moved in a direction substantially orthogonal to the optical axis of the optical system, and the lens 4 to be inspected is used instead. The entire surface of the lens 4 to be inspected is observed while moving in a direction substantially perpendicular to the optical axis of the optical system.

In this embodiment, the thickness data in the optical axis direction of the optical system of the subject lens 4 and the position in the direction substantially orthogonal to the optical system optical axis of the subject lens 4 (in the main scanning direction of the subject lens 4) From the lens height data, the lens 9
And the amount by which the CCD camera 10 should move in the optical axis direction of the optical system is calculated, and the lens 9 and the CCD camera 10 are calculated accordingly.
To move.

That is, the lens 9 and the CCD camera 10
Is moved in the direction of the optical axis of the optical system, and the lens 4 to be inspected is moved in a direction substantially orthogonal to the optical axis, while the imaging relationship between the vicinity of the surface of the lens 4 to be inspected and the CCD camera 10 is maintained. By measuring the entire surface of the measurement target lens 4, it is possible to obtain a measuring device that can easily and accurately realize high-precision measurement of birefringence over the entire surface of the lens 4 to be tested.

[0076]

According to the first aspect of the present invention, the birefringence can be measured with high accuracy over the entire surface of the lens to be inspected, and the measurement time increases due to the processing of the measurement result and the measured value. It is possible to prevent the reliability of the device from decreasing. Further, the birefringence can be easily measured with a simple and low-cost device configuration.

According to the second aspect of the present invention, the surface of the lens to be inspected is moved while moving the imaging optical system and the light receiving means in the optical axis direction of the optical system and the lens to be inspected in a direction substantially orthogonal to the optical axis. By measuring the entire surface of the lens under test while maintaining the imaging relationship between the vicinity and the light receiving element, it is possible to easily and inexpensively realize highly accurate birefringence measurement over the entire surface of the lens under test. A measuring device can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of a birefringence measuring device according to the present invention, and is a schematic configuration diagram thereof.

FIG. 2 is a diagram showing a measurement region of a lens to be inspected according to the first embodiment.

FIG. 3 is a diagram showing a second embodiment of the birefringence measuring device according to the present invention, and is a schematic configuration diagram thereof.

[Explanation of symbols]

1 Semiconductor Laser (Light Source) 2 λ / 4 Plate (First Polarizing Means) 3 Lens (Irradiation Optical System) 4 Test Lens 7 λ / 4 Plate (Second Polarizing Means) 8 Polarizing Plate (Second Polarizing Means) ) 9 lens (imaging optical system) 10 CCD camera (light receiving means) 13 motor driver (holding member control means, test lens control means) 14 computer (calculation means, holding member control means, test lens control means) 17, 19 Stage (holding member) 18, 21 Stepping motor (holding member control means) 31 Lens (parallel optical system) 32 Stage (lens control means for test) 33 Stepping motor (lens control means for test)

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01N 21/00-21/01 G01N 21/17-21/61 G01J 3/00-3/52 G01J 4/00-4 / 04 G01M 11/00-11/08 Practical file (PATOLIS) Patent file (PATOLIS) WPI (DIALOG)

Claims (2)

(57) [Claims] 1. A light source, a first polarization means for changing the light emitted from the light source into a predetermined polarization state, and a lens to be inspected for diverging or converging the light polarized by the first polarization means. An illumination optical system that is incident on the optical system, a second polarization unit that is rotatably provided around the optical system, and that changes the polarization state of the light that has passed through the lens under test at equal angles. A light receiving means for receiving the light transmitted through the polarizing means; and a second light receiving means interposed between the second polarizing means and the light receiving means.
And an image forming optical system for forming an image on the light receiving surface of the light receiving means by the light transmitting means, and the birefringence of the lens under test is calculated based on the light receiving data received by the light receiving means at equal angles. In a birefringence measuring device including a computing means, a holding member that integrally holds the imaging optical system and the light receiving means, and the holding member that is substantially orthogonal to the optical axis direction of the optical system and the optical axis direction. Holding member control means for moving in the direction, and an input means for inputting thickness data in the depth direction of the lens surface to be inspected, the holding member control means, based on the thickness data input from the input means, The holding member is arranged in the optical axis direction of the optical system and substantially orthogonal to the optical axis direction so that the vicinity of the surface of the lens to be inspected facing the imaging optical system and the light receiving surface of the light receiving element always have a substantially image forming relationship. Integrated in the direction Birefringence measuring apparatus characterized by moving the. 2. A parallel optical system for irradiating a light beam parallel to the lens to be inspected is interposed between the lens to be inspected and the first polarizing element, and the lens to be inspected is arranged in an optical axis direction of the optical system. A test lens control means for moving in a direction substantially orthogonal to the test piece is provided, and based on the thickness data input from the input means, the vicinity of the surface of the test lens facing the imaging optical system and the light receiving surface of the light receiving element are always The subject lens control means moves in a direction substantially orthogonal to the optical axis direction of the optical system, and the holding member control means moves in the optical axis direction of the optical system so as to be in a substantially imaging relationship. The birefringence measuring device according to claim 1.