JP2000097805A - Double refraction measuring method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a double refraction measuring method and device capable of providing an image having little effect of optical distortion and transmitted through a lens under test, performing accurate double refraction measurement overt the whole surface of the lens, facilitating the change of kinds of lens and improving the flexibility. SOLUTION: This method and device comprise an illumination optical system 2 for applying divergent light in a given polarized state to a lens 1 under test, a light applying side displacement means 11 for adjusting a position of the illumination optical system 2 to the lens 1 in the optical-axis direction, a polarizing element 15 for changing a polarized state of the transmitted light from the lens 1, a rotating means 21 for rotating the polarizing element 15 almost in the direction of the transmitted light, a rotation angle detecting means 25 for detecting a rotation angle of the polarizing element 15, an array type photodetector 12 for receiving the light transmitted through the polarizing element 15, an image focusing optical system 13 for focusing the light transmitted through the polarizing element 15 on the photodetector 12, and a computing means 23 for computing a double refraction of the lens 1 on the basis of the rotation angle detected and a light receiving output being detected by the photodetector 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a birefringence measuring apparatus and a birefringence measuring apparatus for measuring birefringence of a lens to be measured such as a plastic lens used for optical writing or pickup used in a laser printer or the like. About the method.

[0002]

2. Description of the Related Art Hitherto, as a method of measuring birefringence of a test object such as a test lens of this type, a phase modulation method and a rotation analyzer method are known. In these methods, a transparent object is irradiated with a parallel beam, the transmitted light from the object is received by a light-receiving element such as a photodiode, and the polarization state of the transmitted light due to the birefringence of the object. The birefringence of the test object is obtained by detecting the change in

In the phase modulation method, the "optical technology contact" V
ol. 27. No. 3 (1989), "Measurement and application of birefringence by phase modulation method" 127-P. 134, etc., the irradiation light is phase-modulated using a photoelastic modulator (PEM), and the birefringence is obtained from the phase of the beat signal and the modulation signal of the light transmitted through the transparent test object. I want to ask.

[0004] In the rotating analyzer method, "Ellipsometry" in "Optical Measurement Handbook" (published July 25, 1981, edited by Toshiharu Tada, Junpei Tsujiuchi, Shigeo Minami, Asakura Shoten) is described in P.K. 256
~ P. 265, etc., the transmitted light is received by the light receiving element on the back of the analyzer while rotating the analyzer placed on the back of the transparent test object. The birefringence is determined from the change in the light receiving output.

Further, according to Japanese Patent Application Laid-Open Nos. 4-58138 and 7-77490, a parallel test object is irradiated with an expanded parallel light, and the transmitted light is transmitted to a two-dimensional sensor such as a CCD camera. The birefringence of the test object is obtained by receiving the light at, and the surface measurement of the birefringence is enabled.

[0006]

In both of the phase modulation method and the rotating polarizer method, so-called "point measurement" in which, for example, a thin parallel beam is irradiated on an object and received by a photodiode.
Therefore, it is necessary to adjust the test object and the measuring device to measure the entire surface of the test object. Particularly, when a non-flat plate such as a lens is used as the test object, Since the irradiated light beam is refracted by the test lens, it is difficult to set the test object and the measuring device.

The technique disclosed in Japanese Patent Application Laid-Open No. 4-58138 is "surface measurement", and therefore does not require adjustment of a test object or the like. In the case of a lens having a large aperture, such as a lens (usually an fθ lens), there is a problem that the difference in refractive power between the central portion and the peripheral portion of the lens becomes large, and optical distortion tends to occur after transmission. The example shown in FIG.
0 and the objective lens 101 so as to form an afocal system.
Is arranged, and the collimated light (parallel light) 102 is irradiated on the test lens 100, the light transmitted through the test lens 100 is collimated by the objective lens 101, and then polarized as the measurement light 103. The light is guided to the light receiving element side via the element, the light is received by the light receiving element, and the measurement is performed based on the received light output.

In this case, the refractive power of the light beam 102c passing through the central portion of the test lens 100 is different from that of the light beam 102e passing through the peripheral portion. As a result, if the two lenses 100 and 101 are disposed so that their focal points are aligned, even if the objective lens 10
Even if the lens is an ideal lens having an extremely small aberration of 1, the light rays 102e passing through the peripheral portion of the test lens 100 overlap and travel toward the light receiving element as the measurement light 103e, so that the entire surface of the test lens 100 is sharp. A photoelastic interference fringe image cannot be obtained. FIG. 18 shows a photoelastic interference fringe 105 obtained on the light receiving element 104 by the measuring optical system as shown in FIG. An example is shown in which there is a portion 106 that is brighter than the portion and that an image is affected by stray light. It becomes difficult to measure the extremely bright portion 105e and the portion 106 where the influence of stray light is generated.

When an optical writing lens 200 used in a laser printer or the like is used as a lens to be tested, in actual use, as shown in FIG.
In many cases, the light beam passing through 00 is not parallel to the optical axis of the optical system. The illustrated example is a semiconductor laser unit 201.
Is a system for exposing and scanning the image plane on the surface of the photoconductor 206 through the collimating lens 202, the polygon mirror 203, the lenses 204 and 205, and the optical writing lens 200. Therefore, when the birefringence measurement is performed with the setting of the measuring optical system such that the light beam transmitted through the optical writing lens 200 (test lens) is parallel to the optical axis of the optical system, the optical writing lens 200 The transmission path of the light beam passing through is greatly different from the actual use state. Since the size of the birefringence changes depending on the transmission path of the light beam, it is desirable to perform the measurement in a state close to the actual use of the optical writing lens 200 (test lens). If the transmitted light of the lens to be measured is not parallel to the optical axis of the optical system, the light enters the polarizing element obliquely, and since this polarizing element generally has an incident angle dependency, a measurement error Leads to.

Further, in order to overcome the above-mentioned problems, the distance between the optical system for irradiating the test lens with light and the test lens can be arbitrarily set, and the test lens can be observed while observing the transmitted image of the test lens. By adjusting the distance between the light source and the point light source (the focal point of the microscope objective lens), it is possible to obtain a transmitted image (photoelastic interference fringe image) of the test lens which is less affected by optical distortion. It is desired to be able to accurately measure birefringence over the entire surface of the lens, and at the same time, to be able to easily respond to changes in the type of lens to be inspected and to improve versatility.

This point will be described in more detail. In recent lenses for writing optical systems, the focal length in the main scanning direction and the sub-scanning direction (longitudinal direction and short direction of the scanning optical system lens) are different. Different lenses may be used. When measuring the birefringence of such a lens, it is difficult to irradiate the test lens with an axisymmetric spherical wave using the above-described apparatus to make the transmitted light of the test lens parallel. If the light beam transmitted through the lens to be inspected is not a parallel light beam, the light is obliquely incident on the polarizing element surface disposed in front of the light receiving element. , A measurement error occurs. Further, in the above-described apparatus, an imaging lens is used to form an image-forming relationship between the vicinity of the surface of the lens to be inspected and the light receiving element surface. Is obtained), but if the focal length is different between the main scanning direction and the sub-scanning direction of the lens to be inspected, the image forming position is different between the main scanning and the sub-scanning. An image is obtained, and the position of the lens to be measured and the measured value on the obtained image plane cannot be corresponded.

Accordingly, an object of the present invention is to solve such a problem. That is, the first object of the present invention is to
It is possible to obtain a transmitted image of the test lens having a small influence of optical distortion, and thus to accurately measure the birefringence over the entire surface of the test lens. It is an object of the present invention to provide a birefringence measuring device and a birefringence measuring method which can easily cope with the above and improve the versatility.

A second object of the present invention is to provide a multi-function device capable of performing accurate measurement with a smaller measurement error over the entire surface of a test lens such as an optical writing lens. An object of the present invention is to provide a refraction measuring device and a birefringence measuring method.

Further, a third object of the present invention is to provide an irradiation optical system with a main scanning direction and a sub-scanning direction when the focal length of the lens to be inspected is different between the main scanning direction and the sub-scanning direction. An object of the present invention is to provide a more versatile birefringence measuring device by adding a correction optical system using lenses having different focal lengths so that light transmitted through a lens to be inspected is substantially parallel.

In addition, a fourth object of the present invention is to combine a non-axisymmetric lens and a general axisymmetric lens even when the focal length of the lens to be inspected is long. It is an object of the present invention to provide a birefringence measuring device capable of expanding the range of adaptation to a change in the type of, and further increasing the versatility of measurement.

Finally, a fifth object of the present invention is to provide a large distance between the lens to be inspected and the irradiation optical system when the focal length of the lens to be inspected is long. Since the size of the device becomes large, the lens to be inspected is regarded as a substantially parallel plate (the curvature of the lens surface is infinite).
It is conceivable to irradiate the test lens with the irradiation light from the irradiation optical system before it is converted into a parallel light beam. It is necessary to irradiate a parallel light beam having a large diameter (more than the diameter of the test lens). However,
In order to uniformly collimate the entire light beam having a large diameter exceeding the diameter of the lens to be inspected, a complicated and expensive optical system must be used, which is costly. Therefore, it becomes difficult to perform the area division measurement of the entire test lens by moving the light receiving element side.
Accordingly, the present invention provides a birefringence that enables a divided measurement of the entire area of a test lens by moving the test lens in a direction substantially perpendicular to the optical system optical axis even when the focal length of the test lens is long. It is an object to provide a measuring device and a birefringence measuring method.

[0017]

In order to achieve the above object, the invention according to claim 1 is directed to an irradiation optical system for irradiating divergent light to a test lens in a predetermined polarization state, and an optical system for the test lens. An irradiation-side displacement unit that moves and adjusts the position of the irradiation optical system in the optical axis direction, a polarization element that changes the polarization state of the transmitted light from the lens to be measured, and Rotating means for rotating, rotation angle detecting means for detecting a rotation angle of the polarizing element by the rotating means, an array of light receiving elements for receiving light transmitted through the polarizing element, and light transmitted through the polarizing element. An image forming optical system for forming an image on the light receiving element, and a calculation for calculating a birefringence of the lens to be measured based on a rotation angle detected by the rotation angle detecting means and a light receiving output detected by the light receiving element. And projecting, the birefringence measurement apparatus equipped with a key feature.

According to a second aspect of the present invention, there is provided a birefringence measuring apparatus according to the first aspect, further comprising a light receiving side displacement means for integrally moving the polarizing element, the imaging optical system, and the light receiving element in a direction substantially perpendicular to the optical axis. The device is the main feature.

According to a third aspect of the present invention, there is provided a distance detecting means for detecting a moving distance by the light receiving side displacement means.
The described birefringence measuring device is a main feature.

According to a fourth aspect of the present invention, a polarizing element, an image forming optical system, and a light receiving element are integrated with each other to change an angle with respect to a traveling direction of light transmitted from a lens to be inspected, and the angle is detected. An angle detecting means, comprising:
Or, the birefringence measuring device described in 3 is a main feature.

According to a fifth aspect of the present invention, there is provided a light shielding member for shielding light transmitted through the peripheral portion of the lens to be inspected, and light shielding member moving means for moving the position of the light shielding member. Or, the birefringence measuring device described in 4 is a main feature.

According to a sixth aspect of the present invention, the predetermined distance by the irradiation optical system with respect to the test lens is adjusted while arbitrarily adjusting the distance in the optical axis direction of the irradiation optical system with respect to the test lens disposed at a predetermined position. Irradiating the diverging light of the polarization state of, the polarization element that changes the polarization state of the transmitted light from the test lens is rotated about the traveling direction of the transmitted light, and the rotation angle is detected, and the polarization element is detected. The transmitted light is imaged substantially on the light receiving surface of the array of light receiving elements by an imaging optical system, and the test object is detected based on the detected rotation angle of the polarizing element and the received light output detected by the light receiving element. The main feature is a birefringence measuring method for calculating the birefringence of a lens.

According to a seventh aspect of the present invention, the polarizing element, the imaging optical system, and the light receiving element are integrally movable and adjustable in a direction substantially orthogonal to the optical axis, and can be adjusted in accordance with the measurement target area on the lens to be measured. The main feature is the method for measuring birefringence according to claim 6, wherein the movement is adjusted.

According to an eighth aspect of the present invention, the polarizing element, the imaging optical system, and the light receiving element are integrally formed so that the angle can be freely changed with respect to the traveling direction of the transmitted light from the test lens. The main feature is the method for measuring birefringence according to claim 6 or 7, wherein the angle is adjusted in accordance with the angle of light transmitted through the target area.

According to a ninth aspect of the present invention, there is provided a light-shielding member for blocking light transmitted through the peripheral portion of the lens to be inspected, and the position of the light-shielding member is arbitrarily set so that stray light generated by transmitting through the peripheral portion is eliminated. The main feature of the method is the birefringence measurement method according to claim 6, 7 or 8, which is adjusted and set.

According to a tenth aspect of the present invention, there is provided an irradiation optical system for irradiating a test lens with divergent light in a predetermined polarization state, and irradiation for moving and adjusting the position of the irradiation optical system with respect to the test lens in the optical axis direction. Side displacement means, a polarization element for changing the polarization state of the transmitted light from the lens to be measured, a rotation means for rotating the polarization element substantially in the traveling direction of the transmitted light, and the polarization element by hand-rotation A rotation angle detecting means for detecting a rotation angle of the light-receiving element, an array of light-receiving elements for receiving light transmitted through the polarizing element, and forming an image of the light transmitted through the polarizing element substantially on a light-receiving surface of the light-receiving element. An imaging optical system having a variable imaging magnification, and a light receiving side displacement unit that integrally adjusts the polarization element, the rotation unit, the light receiving element, and the imaging optical system as a light receiving unit in a direction substantially orthogonal to the optical axis; , The rotation angle detection Calculating means for calculating the birefringence of the lens under test based on the received light output which is received and detected by the rotation angle and the light receiving element is detected by means of the birefringence measurement apparatus equipped with a key feature.

According to an eleventh aspect of the present invention, there is provided an irradiation optical system for irradiating the test lens with divergent light in a predetermined polarization state, and irradiation for moving and adjusting the position of the irradiation optical system with respect to the test lens in the optical axis direction. Side displacement means, a polarizing element for changing the polarization state of the transmitted light from the lens to be measured, a rotating hand for rotating the polarizing element substantially in the traveling direction of the transmitted light, and the polarizing element by the rotating means A rotation angle detecting hand for detecting the rotation angle of the light, an array of light receiving elements for receiving the light transmitted through the polarizing element, and an image of the light transmitted through the polarizing element substantially on the light receiving surface of the light receiving element A plurality of light receiving units each having an imaging optical system as one unit; branching means for splitting transmitted light from the lens to be detected and entering each of the light receiving units; and the rotation angle in each light receiving unit. A birefringence measuring device mainly includes: a calculating means for calculating a birefringence of the test lens based on a rotation angle detected by the detection hand throw and a light reception output detected by the light receiving element.

According to a twelfth aspect of the present invention, each of the light receiving units is disposed with respect to the branching means so as to receive the transmitted light from a different measurement area of the lens to be measured. The main feature is a refractometer.

According to a thirteenth aspect of the present invention, the main feature of the birefringence measuring device according to the eleventh or twelfth aspect is that each imaging optical system is capable of changing the imaging magnification independently for each light receiving unit. I do.

According to a fourteenth aspect of the present invention, the imaging optical system comprises:
14. The birefringence according to claim 10, wherein an imaging magnification is automatically set based on a transmission image of the test lens obtained when the transmitted light from the test lens is formed on a light receiving surface of the light receiving element. The main feature is the measuring device.

According to a fifteenth aspect of the present invention, there is provided an irradiation optical system for irradiating a test lens with light in a predetermined polarization state, and an irradiation side for moving and adjusting a position of the irradiation optical system with respect to the test lens in an optical axis direction. Displacement hand throwing, a correction optical system disposed on the irradiation side of the lens to be inspected to make a light beam transmitted through the lens to be substantially parallel light, and changing a polarization state of light transmitted from the lens to be inspected. A polarizing element, rotating means for rotating the polarizing element about a traveling direction of the transmitted light, rotation angle detection hand-detection for detecting a rotating angle of the polarizing element by the rotating means, and light transmitted through the polarizing element. An array-shaped light receiving element that receives light, an imaging optical system that forms an image of light transmitted through the polarizing element substantially on a light receiving surface of the light receiving element,
A birefringence measurement device comprising: a rotation angle detected by the rotation angle detection means; and a calculating means for calculating birefringence of the lens to be detected based on a light reception output detected by the light receiving element. I do.

The invention according to claim 16 is characterized by the birefringence measuring apparatus according to claim 15, wherein the correction optical system is a combination of a plurality of optical elements having different optical characteristics.

The invention according to claim 17 is characterized in that the birefringence measuring apparatus according to claim 15 or 16 is provided with lens displacement means for moving and adjusting the test lens in a direction orthogonal to the optical axis thereof.

The invention according to claim 18 is that, after arbitrarily adjusting the distance in the optical axis direction of the irradiation optical system with respect to the test lens disposed so as to be movable at a predetermined position in a direction orthogonal to the optical axis, While adjusting the position of the test lens in the direction orthogonal to the optical axis in accordance with the measurement target area on the test lens, a predetermined polarization state of the irradiation optical system with respect to the measurement target area of the test lens is obtained. Light is applied to the test lens through the correction optical system to emit substantially parallel transmitted light, and a polarizing element that changes the polarization state of the transmitted light from the test lens is directed substantially in the traveling direction of the transmitted light. While rotating around, the rotation angle is detected, and the light transmitted through the polarization element is imaged substantially on the light receiving surface of the array of light receiving elements by an imaging optical system, and the detected rotation angle of the polarization element and Received by the light receiving element The birefringence measurement method as the sequentially calculates the birefringence of the measurement target region of the lens based on the detected light output is mainly characterized.

[0035]

According to the birefringence measuring device of the first aspect and the refraction measuring method of the sixth aspect, the image forming apparatus configured as described above basically has a rotary analyzer method. According to the above, the transmitted light transmitted through the lens to be measured is incident on a polarizing element that changes the polarization state, and the birefringence of the lens to be tested is detected by rotating the polarizing element and receiving and detecting the light with an array of light receiving elements. The distance between the irradiation optical system that irradiates the test lens with the divergent light and the test lens can be set arbitrarily, and the distance between the test lens and the irradiation optical system can be calculated while observing the transmission image of the test lens. By adjusting it, a photoelastic interference fringe, which is a transmitted image of the test lens with little influence of optical distortion, can be obtained, so that birefringence measurement can be accurately performed over the entire surface of the test lens. The type of lens to be inspected Et al, even easily cope, it is possible to provide a high birefringence measuring apparatus or method versatile.

According to the birefringence measuring device according to the second and third aspects and the birefringence measuring method according to the seventh aspect,
Since the polarizing element, the imaging optical system, and the light receiving element are integrally moved in a direction substantially perpendicular to the optical axis, that is, moved in the longitudinal direction of the lens to be measured, the measurement can be performed while dividing the lens. Refraction measurement can be realized at low cost without lowering the resolution.

According to the birefringence measuring device of the invention described in claim 4 and the birefringence measurement method of the invention described in claim 8, the lens to be inspected may be a scanning lens used for optical writing. Basically, the measurement system can be set to a state close to actual use by a configuration in which the distance between the test lens and the irradiation optical system can be set arbitrarily. By adjusting the angle integrally with the polarizing element and the like, the light can be incident in a state close to vertical, and more accurate measurement can be performed.

According to the birefringence measuring device of the fifth aspect and the birefringence measuring method of the ninth aspect, when the light transmitted through the peripheral portion of the lens to be detected enters the light receiving element as stray light, the measurement is performed. However, since a light-blocking member is provided for such a peripheral portion, it is possible to eliminate the influence of stray light, to eliminate an unmeasurable area, and to enable measurement over the entire surface of the lens to be measured. In particular, by appropriately moving the light-shielding member by the light-shielding member moving means, it is possible to completely remove the influence of stray light in a form suitable for the lens to be inspected.

According to the tenth aspect, the irradiation optical system for irradiating the test lens with the divergent light in a predetermined polarization state, and the position of the irradiation optical system in the optical axis direction with respect to the test lens are adjusted. Irradiation side displacement means, a polarizing element for changing the polarization state of the transmitted light from the lens to be inspected, a rotating means for rotating the polarizing element substantially in the traveling direction of the transmitted light, A rotation angle detecting means for detecting the rotation angle of the polarizing element, an array of light receiving elements for receiving the light transmitted through the polarizing element, and connecting the light transmitted through the polarizing element to substantially the light receiving surface of the light receiving element; An imaging optical system with a variable imaging magnification to be imaged, and a light-receiving-side displacement that moves and adjusts the polarizing element, the rotating unit, the light-receiving element, and the imaging optical system as a light-receiving unit integrally in a direction substantially orthogonal to the optical axis. Means and said times The operation according to claim 1, further comprising: an arithmetic unit configured to calculate a birefringence of the test lens based on the rotation angle detected by the angle detection unit and a light reception output detected by the light receiving element. In addition to the effect, the polarizing element and the light receiving element are generally limited in size (element area), and are not suitable for receiving transmitted light from an entire lens having a large aperture such as a lens used in an optical writing system. It is difficult in terms of size to use a general polarizing element or light receiving element, and if a large polarizing element or light receiving element is used, the manufacturing cost increases. On the other hand, if the transmitted light from the entire test lens is optically reduced according to the size of a general polarizing element or light receiving element, the optical system becomes complicated, and the spatial image of the photoelastic interference fringes is increased. Is reduced, and the spatial resolution of the measurement is reduced accordingly. In this regard, the polarizing element, the imaging optical system, and the light receiving element are integrally formed as a light receiving unit in a direction substantially orthogonal to the optical axis, that is,
Since the measurement can be performed while moving the test lens in the longitudinal direction while dividing the test lens, the measurement of the birefringence of the entire test lens can be realized at low cost without lowering the resolution. At this time, when several lenses to be measured are measured or when one lens to be measured is divided into several areas to be measured, birefringence may be generated depending on the lens to be measured or the location of the lens to be measured. May be different. In particular, since the interval between the interference fringes differs depending on the state of occurrence of birefringence, the reliability of the measurement decreases in a region where the interval between the interference fringes is close to or smaller than the size of the minimum unit pixel of the light receiving element. . In this regard, since the imaging magnification of the imaging optical system is variable, it is necessary to optimally set the imaging magnification according to the state of birefringence that varies depending on the lens to be inspected or the location of the lens to be inspected. Thereby, accurate measurement can be performed regardless of the state of occurrence of birefringence. In other words, the birefringence measurement can be accurately performed over the entire surface of the lens to be inspected, and at the same time, the type of the lens to be inspected can be easily changed and a highly versatile birefringence measuring apparatus can be provided. Above, regardless of the state of occurrence of birefringence, by setting the imaging magnification of the imaging optical system optimally in accordance with the state of occurrence of birefringence depending on the lens to be inspected or the location of the lens to be inspected Accurate measurement can be performed.

According to the eleventh aspect of the invention, it is basically the same as the tenth aspect of the invention, except that a plurality of light receiving units are provided, and the transmitted light from the lens to be inspected is divided by the branching means. Since the light is branched and incident toward each light receiving unit, even if the lens to be measured is a lens having a large diameter such as a lens used in an optical writing system, the resolution is not reduced and the light is not received. It is possible to simultaneously measure the entire test lens without moving the unit side.
That is, since a plurality of light receiving units are provided, the entire lens to be measured can be measured simultaneously without moving the light receiving unit side.

According to a twelfth aspect of the present invention, each of the light receiving units of the birefringence measuring device according to the eleventh aspect is arranged with respect to the branching means such that each of the light receiving units receives transmitted light from a different measurement area of the lens to be measured. Since it is provided, simultaneous measurement of the entire test lens can be performed with high efficiency and operability.

According to the thirteenth aspect of the present invention, when one test lens is divided into several test areas and measured simultaneously, even in the same test lens, for example, the vicinity of the lens center and the lens peripheral portion In many cases, since the cooling rate of the temperature in the lens molding is different, the way in which birefringence occurs is often different. For this reason, for example, the interval between the photoelastic interference fringes may be large near the center of the lens, and the interval between the photoelastic interference fringes may be small near the periphery, and the interval between the interference fringes may be close to the pixel size of the light receiving element, or In an area smaller than the size, the reliability of the measurement decreases. In this regard, since the imaging magnification of each imaging optical system can be changed independently for each light receiving unit, the occurrence of birefringence that varies depending on the lens to be measured or depending on the position of the lens to be measured in the measurement area. By setting the imaging magnification optimally for each light receiving unit in accordance with the state, more accurate measurement can be performed regardless of the state of occurrence of birefringence.

According to the fourteenth aspect of the present invention, the imaging magnification is automatically adjusted based on the transmitted image of the test lens obtained when the transmitted light from the test lens is formed substantially on the light receiving surface of the light receiving element. Is set. Since the appropriate imaging magnification is automatically set based on the interval data of interference fringes in the actual transmitted image from the lens to be inspected, etc., the operability as a measuring device is improved and the imaging magnification is optimized. You can also plan.

According to the fifteenth aspect of the invention, basically, according to the rotary analyzer method, the light is transmitted to the polarizing element for changing the polarization state of the transmitted light transmitted through the lens to be measured, and this polarizing element is The birefringence of the test lens is calculated by detecting the light received by the array of light receiving elements while rotating, but the distance between the irradiation optical system that irradiates the test lens with divergent light and the test lens can be set arbitrarily. By adjusting the distance between the test lens and the irradiation optical system while observing the transmission image of the test lens, it is possible to obtain a photoelastic interference fringe that is a transmission image of the test lens having a small influence of optical distortion. Birefringence can be accurately measured over the entire surface of the lens. At this time, even if the lens to be inspected has a different focal length between the main scanning direction and the sub-scanning direction, for example, a lens having a different focal length between the main scanning direction and the sub-scanning direction is provided downstream of the irradiation optical system. By adding a correction optical system and making the light flux transmitted through the test lens substantially parallel, the above-described birefringence measurement can be performed without impairing the normal operation of the optical element after the polarizing element,
Versatility increases.

According to a sixteenth aspect of the present invention, in the birefringence measuring apparatus according to the fifteenth aspect, the correction optical system is composed of a combination of a plurality of optical elements having different optical characteristics. Not only when the focal length is different from the scanning direction but also when the focal length is long, for example, a plurality of optical characteristics different from each other, such as a combination of a non-axisymmetric lens and a normal axisymmetric lens. By configuring the correction optical system with the optical element, it is possible to freely respond to a change in the type of the lens to be inspected, and the versatility is enhanced.

According to a seventeenth aspect of the present invention, there is provided the birefringence measuring apparatus according to the fifteenth or sixteenth aspect, further comprising lens displacement means for moving and adjusting the test lens in a direction orthogonal to its optical axis. Even when the focal length of the lens is long, by moving the lens to be examined in a direction orthogonal to the optical axis, it is possible to perform a divided measurement of the entire area of the lens to be examined. This makes it possible to measure the birefringence of the entire test lens at low cost without lowering the resolution.

In the method for measuring birefringence according to the eighteenth aspect of the present invention, the distance in the optical axis direction of the irradiation optical system with respect to the lens to be inspected, which is disposed so as to be movable in a direction perpendicular to the optical axis at a predetermined position, can be arbitrarily set. After the adjustment, the irradiation optical system adjusts the position of the lens to be measured in the direction perpendicular to the optical axis while adjusting the position of the lens to be measured on the lens to be measured by adjusting the position of the lens to be measured on the lens to be measured. Light having a predetermined polarization state is applied to the lens under test through a correction optical system to emit substantially parallel transmitted light, and transmitted through the polarizing element that changes the polarization state of light transmitted from the lens under test. The rotation angle is detected while rotating about the traveling direction of the light, and the light transmitted through the polarizing element is imaged on the light receiving surface of an array of light receiving elements by an imaging optical system, and the detected polarization is detected. The rotation angle of the element and the Since the birefringence of the measurement target area of the lens to be measured is sequentially calculated based on the light receiving output detected and detected by the optical element, basically, the birefringence of the lens to be measured is transmitted through the lens to be measured according to the rotation analyzer method. The birefringence of the lens to be measured is calculated by causing the arrayed light-receiving elements to detect and detect light while rotating the polarizing element, and then diverging the light to the lens. Influence of optical distortion by adjusting the distance between the test lens and the irradiation optical system while observing the transmitted image of the test lens by arbitrarily setting the distance between the irradiation optical system and the test lens. Since a photoelastic interference fringe, which is a transmitted image of the test lens having a small value, can be obtained, the birefringence can be accurately measured over the entire surface of the test lens. At this time, even if the lens to be inspected has a different focal length between the main scanning direction and the sub-scanning direction, for example, a lens having a different focal length between the main scanning direction and the sub-scanning direction is provided downstream of the irradiation optical system. By adding a correction optical system so that the luminous flux transmitted through the lens to be inspected is almost parallel, the above-described birefringence measurement can be performed without impairing the normal operation of the optical element after the polarization element, and versatility is improved. Increase. In addition, even when the focal length of the test lens is long, by moving the test lens in a direction perpendicular to its optical axis, it is possible to perform a divided measurement of the entire area of the test lens. This makes it possible to measure the birefringence of the entire test lens at low cost without lowering the resolution.

[0048]

FIG. 1 shows a first embodiment of the present invention.
A description will be given based on FIG. The test lens 1 to be measured in the present embodiment is held by a holder (not shown). An irradiation optical system 2 for irradiating the test lens 1 with light in a predetermined polarization state is provided for the test lens 1. The irradiation optical system 2 includes a He-Ne laser 3 as a light source that emits a randomly polarized light beam, an ND filter 4 for adjusting a light amount, mirrors 5 and 6 for deflection, and a He-Ne laser.
A polarizing plate 7 for converting light from the Ne laser 3 into linearly polarized light;
Λ / 4 for converting linearly polarized light by the polarizing plate 7 to circularly polarized light
It is composed of a plate 8, a lens 9, and a pinhole 10. The lens 9 plays a role equivalent to that of an objective lens in a microscope, and irradiates the test lens 1 with divergent light. The pinhole 10 functions as a shale filter. The lens 9 and the pinhole 10 are mounted on a stage 11 that can move in the optical axis direction, and move forward and backward in the optical axis direction by rotation of a stepping motor (not shown) for driving the stage 11. . Here, an irradiation-side displacement unit is configured by the stage 11 and a stepping motor, and the position (distance) of the lens 9 with respect to the test lens 1 in the optical axis direction is adjustable. The stepping motor is provided with a rotation origin position sensor. The distance between the lens 9 and the test lens 1 is set to a predetermined distance in advance, and the state is set to the stage 11.
When the number of pulses supplied to the stepping motor is counted, a change in the distance between the lens 9 and the test lens 1 due to the movement of the stage 11 can be detected. This distance is detected based on the counting operation of the number of pulses in the step (distance detecting means).

A CCD camera 12 is provided on the optical axis on the transmitting and emitting side of the test lens 1 as an array of light receiving elements for receiving the transmitted light. Test lens 1 and C
An imaging optical system 13 is provided between the camera and the CD camera 12. The image forming optical system 13 converts a light beam, which has become elliptically polarized light close to circularly polarized light due to its birefringence, into the elliptically polarized light close to linearly polarized light, by passing through the test lens 1.
And a lens 16 that forms an image of light passing through a polarizing plate 15 as a polarizing element on a CCD camera 12. The lens 16 is located near the surface of the lens 1 to be inspected and a CCD.
The position is adjusted in advance so that an image-forming relationship is established with the camera 12. The lens 16 is made of a material such as a glass lens from which the internal birefringence has been sufficiently removed.

The λ / 4 plate 14 and the polarizing plate 15 are provided with stepping motors 17 and 18 and gear systems 19 and 20 for rotating the λ / 4 plate 14 and the polarizing plate 15 about the traveling direction of light. . A rotation origin position sensor (not shown) is attached to each of the stepping motors 17 and 18, and the λ / 4 plate 14 and the polarizing plate 15
Each rotation angle can be detected (actually,
Based on the operation of counting the number of pulses in the personal computer described later, λ
The rotation angle of each of the / 4 plate 14 and the polarizing plate 15 is detected ...
Rotation angle detecting means). A motor driver 22 drives the stepping motors 17 and 18 and drives the stepping motors 17 and 18 by receiving pulses from the personal computer 23 and the pulse generator 24.

The image data picked up by the CCD camera 12 is fetched into the memory of the personal computer 23 through the image input device 25, and a predetermined calculation is performed based on the image data and the rotation angle data of the stepping motors 17 and 18. The birefringence phase difference and principal axis direction of the test lens 1 are calculated by the method. An arithmetic processing function such as a CPU included in the personal computer 23 executes a function as an arithmetic means for calculating the birefringence of the lens 1 to be measured. Incidentally, the image captured by the CCD camera 12 is displayed on the monitor of the personal computer 23 or a dedicated monitor.

In such a configuration, the setting state of the birefringence measuring device in the case of the present embodiment will be described. First, the azimuth of the polarizing plate 7 is set in a direction horizontal to the plane of the paper, and the azimuth of the λ / 4 plate 8 is set to 45 degrees with respect to the plane of the paper. It is set. Before performing the measurement, for example, the azimuth of the λ / 4 plate 14 is set to 45 degrees with respect to the direction parallel to the plane of the paper, and the azimuth of the polarizing plate 15 is rotated while the test lens 1 is not set. The azimuth angle of the polarizing plate 15 is set so that the transmitted light intensity from the polarizing plate 15 becomes the smallest (the transmitted light becomes the darkest). This azimuth angle is stored as the rotation origin in the measurement. In this case, a glass lens having almost no birefringence may be temporarily set at the position of the lens 1 to be inspected, and the light beam incident on the polarizing plate 15 and the CCD camera 12 may be collimated. Regarding the distance between the lens 9 and the lens 1 to be inspected, for example, a state in which the lens 9 and the lens 1 to be inspected physically approach each other is set as a movement origin, and the stage 11 is moved from this movement origin. The distance between the lens 9 and the test lens 1 can be detected. In the present embodiment, an example of measurement in a state where the focal point of the lens 9 and the focal point of the lens 1 to be inspected are almost matched will be described. In this state, the transmitted light of the test lens 1 is generally almost parallel light, but as described with reference to FIG. 8, light rays from the periphery of the test lens are observed in an overlapping manner, or the transmitted image of the test lens is In the case of distorted observation, the overlap of light beams can be removed by adjusting the distance between the lens 9 and the test lens while observing the transmitted image of the test lens 1.

Further, regarding the writing optical system, the position where the light beam is reflected by the scanning mirror is assumed to be the focal position of the lens 9 in FIG. 1, and the distance between the scanning mirror surface and the test lens in the writing optical system. If the lens 9 and the test lens 1 are set at an interval position corresponding to the above, it is possible to measure the transmission path of the light beam in the test lens 1 in a state closer to the actual use. Further, when the writing optical system is composed of several lenses, another lens constituting the writing optical system may be arranged on the optical axis in order to further approximate actual use. Good.

At the time of actual measurement, first, the test lens 1 is held by a holder and set at a predetermined position.
The polarizing plate 15 is rotated by (180 / n) degrees from the rotation origin position in a state where the direction of the plate 14 is 45 degrees with respect to the direction parallel to the paper surface. n is the number of measurement points set in advance. Therefore, every time the polarizing plate 15 rotates by (180 / n) degrees, the CCD image data read by the CCD camera 12 is fetched into the memory of the personal computer 23, and the rotation angle data of the polarizing plate 15 and the n CCD image data are converted. get. Next, the direction of the λ / 4 plate 14 is set to 0 with respect to the direction parallel to the paper surface.
In the same manner as described above, while rotating the polarizing plate 15 by (180 / n) degrees from the rotation origin position,
The CCD image data is taken into the memory of the personal computer 23 to acquire the rotation angle data of the polarizing plate 15 and the n pieces of CCD image data. The birefringence of the lens 1 to be inspected is calculated by the arithmetic unit based on the 2n CCD image data acquired by the personal computer 23 and the rotation angle data of the polarizing plate 15 in the following procedure. Ask.

Now, it is assumed that the state of change of the polarization state in the optical system in the measuring apparatus shown in FIG. 1 is represented using a Mueller matrix. Let L be the mueller matrix of the circularly polarized light incident on the lens 1 to be tested, T be the mute matrix of the lens 1 to be tested, Q be the mulle matrix of the λ / 4 plate 14, A be the mueller matrix of the polarizing plate 15, and be the Stokes parameter S. Ask.

First, the Stokes parameter S ₄₅ when the azimuth of the λ / 4 plate 14 is set at 45 degrees with respect to the direction parallel to the paper surface is expressed by the following equation (1).

[0057]

(Equation 1)

From equation (1), the light intensity I ₄₅ obtained by the CCD camera 12 is as shown in equation (2).

[0059]

(Equation 2)

In the equations (1) and (2), θ is the polarization plate 15
Is the birefringent phase difference of the lens 1 to be measured, and φ is the principal axis direction of the lens 1.

When the polarizing plate 15 is rotated by the stepping motor 18, θ in these equations changes, and the light intensity I _{45 of the} equation (2) obtained by the CCD camera 12 changes.
FIG. 2 shows how the light intensity I ₄₅ changes with the rotation of the main axis direction of the polarizing plate 15. However, the value of the light intensity I _{45 on} the vertical axis is normalized such that the maximum value is 1 and the minimum value is 0.

Here, assuming that the resolution for reading the rotation angle of the polarizing plate 15 is R (rotation angle corresponding to one pulse of the stepping motor 18), the phase of the light intensity change due to the rotation of the main axis direction of the polarizing plate 15 is obtained. φ ₄₅ can be obtained from the actually measured CCD image data and the rotation angle data of the polarizing plate 15 as shown in Expression (3).

[0063]

(Equation 3)

Next, the Stokes parameter So when the azimuth of the λ / 4 plate 14 is set to 0 ° with respect to the direction parallel to the plane of the paper is expressed by equation (4).

[0065]

(Equation 4)

From equation (4), the light intensity I ₀ obtained by the CCD camera 12 is as shown in equation (5).

[0067]

(Equation 5)

In equations (4) and (5), θ is
5 is the principal axis direction, δ is the birefringence phase difference of the lens 1 to be measured, and φ is the principal axis direction of the lens 1 to be measured.

The phase φ ₀ of the light intensity change due to the rotation of the main axis direction of the polarization slope 15 is calculated as in the case of the equation (3).
It is obtained as in equation (6).

[0070]

(Equation 6)

By transforming equations (2) and (5), the phase φ
_{When 45 and} φ ₀ are obtained, they are expressed by equations (7) and (8).

[0072]

(Equation 7)

Therefore, the phase difference δ and the principal axis direction φ can be obtained from the equations (3), (6), (7), and (8) as in the equations (9) and (10).

[0074]

(Equation 8)

Therefore, according to the present embodiment, basically, according to the rotation analyzer method, the transmitted light transmitted through the lens 1 to be measured is made incident on the polarizing plate 15 for changing its polarization state. While rotating the polarizing plate 15, the CCD camera 12
The birefringence of the lens 1 to be measured is calculated by detecting the light reception in the step (1). By adjusting the distance between the test lens 1 and the lens 9 while observing the transmission image of the test lens, it is possible to obtain a photoelastic interference fringe which is a transmission image of the test lens which is less affected by optical distortion. Birefringence measurement can be accurately performed over the entire surface of the inspection lens 1. At the same time, the test lens 1
Can easily cope with the change of the type, and a highly versatile birefringence measuring apparatus or method can be obtained.

FIGS. 3 and 4 show a second embodiment of the present invention.
It will be described based on. The same portions as those described in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the present embodiment, the λ / 4 plate 14, the polarizing plate 15, the lens 16, the CCD camera 12, and the rotating means 21 are mounted on the base 31, and the guide 32 guides the direction substantially perpendicular to the optical axis of the measuring optical system ( It is movable in the vertical direction indicated by the arrow in the drawing). The base 31 is driven to be displaced by a stepping motor 33. Here, these base 31, guide 32, stepping motor 33
The polarizing plate 15, the lens 16, and the CCD camera 12
And a light receiving side displacement means 34 for moving and adjusting in the direction orthogonal to the optical axis.

In such a configuration, in the measuring optical system shown in FIG. 3, it is assumed that the lens 16 and the imaging surface of the CCD camera 12 have an image forming relationship in the vicinity of the lens 1 to be measured. For this reason, the spatial image of the photoelastic interference fringes generated near the test lens 1 due to the birefringence of the test lens 1
5, the divergent light illuminating the test lens 1 is almost collimated by the test lens 1, so that the photoelastic interference fringe generated near the test lens 1 The aerial image has substantially the same size (area) as the lens 1 to be measured.

On the other hand, the λ / 4 plate 1 constituting the measuring optical system
4. The size (area) of the polarizing plate 15 is at most 5 in diameter.
It is about 0 mm, and a spatial image of a photoelastic interference fringe having a size exceeding 0 mm cannot be transmitted at a time. As a result, when the diameter of the test lens 1 increases, the test lens 1
Measurement of birefringence over the entire surface becomes impossible. At this point, the λ / 4 plate 1 is obtained by temporarily reducing the spatial image of the photoelastic interference fringes.
4. The light may be transmitted through the polarizing plate 15, but in this case, the measurement optical system becomes complicated and the aerial image of the photoelastic interference fringes becomes small, so that the spatial resolution in the measurement is reduced, and When the birefringence of the inspection lens 1 is large, the fringe interval of the photoelastic interference fringes becomes smaller than the size of the CCD camera 12, and the measurement itself may not be possible.

For this reason, in the present embodiment, the λ / 4 plate 1
By integrating the fourth and subsequent optical system elements and moving them in a direction substantially perpendicular to the optical system optical axis, a spatial image of photoelastic interference fringes having substantially the same size as the test lens 1 is partially formed. The measurement is performed by dividing and observing with the CCD camera 12. For example, as shown in FIG. 4, first, the base 31 is moved by the stepping motor 33 so that the measured area E1 of the lens 1 to be observed can be observed. Measure the main axis direction. Subsequently, the measured area E2 of the lens 1 to be measured
The base 31 is moved by the stepping motor 33 so that the object can be observed. In this state, the phase difference and the principal axis direction are measured in the same manner. Then, the phase difference and the principal axis direction may be measured in the same manner in this state.

In the present embodiment, when determining the area to be measured of the lens 1 to be measured, for example, it is necessary to observe the photoelastic interference fringes monitored and imaged by the CCD camera 12 while moving the base 31. Then, an appropriate area may be selected. Alternatively, a rotation origin position sensor is attached to the stepping motor 33 so that the moving distance of the base 31 can be detected by the number of pulses supplied to the stepping motor 33, and the area to be measured is determined in advance, and the area can be observed. The base 31 may be automatically moved to the position. In the latter case, the moving distance of the base 31 (therefore, the polarizing plate 15 or the like) is actually detected based on the operation of counting the number of pulses in the personal computer 23 (distance detecting means).

As described above, according to the present embodiment,
The birefringence of the entire lens 1 to be measured can be measured without lowering the resolution.

A third embodiment of the present invention will be described with reference to FIG. In the present embodiment, the polarizing plate 15 and the lens 1
A base 31 on which 6 and the like are mounted is mounted and provided on a rotary stage 35 serving as angle varying means. This allows
The angle of the polarizing plate 15 and the like with respect to the traveling direction of the transmitted light from the test lens 1 can be changed. Although not particularly shown, an angle detecting means for detecting the direction (angle) of the polarizing plate 15 or the like by the rotating stage 35 is provided.

As described above, when the focal point of the lens and the focal point of the test lens 1 are substantially coincident, the transmitted light of the test lens 1 extends over the entire surface of the test lens 1 with respect to the optical axis of the optical system. Since they are substantially parallel, it is not necessary to rotate the directions of the λ / 4 plate 14 and the polarizing plate 15. However, the distance between the lens 9 and the lens 1 to be inspected is set as described above (both focal positions) when the lens 1 to be inspected is an aspheric surface or in order to make the lens 1 closer to the actual use state in the optical writing system as illustrated in FIG. Are substantially shifted from each other), the test lens 1
Is not parallel to the optical axis of the optical system, and the traveling angle of the light beam with respect to the optical axis of the optical system differs depending on the measurement area of the lens 1 to be measured. Further, the λ / 4 plate 14 and the polarizing plate 15 have an incident angle dependency of light rays, and unless the light rays are incident perpendicularly to the element surface, they do not perform a predetermined function and cause a measurement error. Therefore, in the present embodiment, in such a situation, the λ / 4 slope 14 and the polarizing plate 1
5. Rotating stage 3 with lens 16 and CCD camera 12
By rotating the optical element 5 integrally, these optical elements face the light transmitted through the lens 1 to be measured.

Incidentally, strictly speaking, even within a partially measured area that can be observed at a time, the traveling angle of the light beam varies slightly depending on the location. Polarizer 15 for the traveling angle of
By rotating the rotary stage 35 so that the element surface is perpendicular (directly facing), measurement with less error can be performed. Further, as for the advancing angle of the light beam with respect to the optical axis of the optical system, for example, an angle at each lens height of the test lens 1 after passing through the test lens is previously obtained by a ray tracing simulation. The average traveling angle of the light beam in the partial area to be measured may be obtained based on the shape of the optical system or the setting of the measuring optical system. Further, in the case of a test lens having different curvatures in the main and sub directions, such as a toroidal surface, a tilt mechanism is provided on the base 31 in addition to the rotary machine groove such as the rotary stage 35. What is necessary is just to make it perform the same operation | movement as mentioned above dimensionally.

Therefore, according to the present embodiment, even when the test lens 1 is a scanning lens used for optical writing, basically, the distance between the test lens 1 and the lens 9 The measurement system can be set to a state close to actual use by a configuration that can be arbitrarily set, and the angle is almost perpendicular by integrally adjusting the angle of the polarizing plate 15 and the like with the traveling direction of the transmitted light of the test lens 1. It can be made to enter in a state, and more accurate measurement becomes possible.

FIGS. 6 and 7 show a fourth embodiment of the present invention.
It will be described based on. In the present embodiment, it is assumed that the test lens 1 used in each of the above-described embodiments has a large diameter, or has a flat portion 1a at the periphery as shown in FIG. ing.

Under such an assumption, in the present embodiment,
In a holder 41 for holding the lens 1 to be tested, a light blocking member 4 for blocking light transmitted through a peripheral portion of the lens 1 to be tested.
2 are provided. The light-shielding member 42 is mounted on a stage 44 that is movable along a guide 43 on the holder 41 and serves as a light-shielding member moving unit, and the position of the light-shielding member 42 with respect to the lens 1 to be measured can be changed in a direction perpendicular to the optical axis. It is adjustable.

In such a configuration, in the case of a test lens having a large diameter or a test lens having a flat portion at the peripheral portion, transmitted light from the peripheral portion of the test lens 1 overlaps or becomes stray light. Heading toward the measurement system may interfere with the measurement. In this respect, in the present embodiment, the light shielding member 42
Is provided so as to block the light transmitted through the peripheral portion, so that there is no influence of light that hinders the measurement. In general, a portion that generates stray light, such as the flat portion 1a of the lens 1 to be inspected, is often an ineffective region as a lens and does not need to be measured. The provision of such an arrangement does not interfere with the original measurement.

When trying to shield light that hinders measurement, the stage 44 on which the light shielding member 42 is mounted is moved in a direction substantially perpendicular to the optical axis of the optical system (see FIG. 7 in the direction indicated by the arrow)
What is necessary is just to find the position of the stage 44 where the influence of the stray light disappears. The monitor image in this case may be observed by the CCD camera 12, or may be projected on a simpler screen.

Therefore, according to the present embodiment, if the light transmitted through the peripheral portion of the lens 1 to be measured enters the CCD camera 12 as stray light, it may hinder the measurement. Since it is provided, there is no influence of stray light, and it is possible to eliminate the unmeasurable region, thereby enabling measurement over the entire surface of the lens 1 to be measured. In particular, by appropriately moving the light shielding member 42 by the stage 44, the influence of stray light can be completely removed in a form suitable for the lens 1 to be measured.

The fifth embodiment of the present invention will be described again with reference to FIG. In the present embodiment, the same parts as those described in the second embodiment described above are denoted by the same reference numerals, and description thereof will be omitted. The difference between the second embodiment and the present embodiment is that, in the present embodiment, the λ / 4 plate 14
Subsequent optical elements are integrally formed as a light receiving unit 26 in FIG. By moving the light receiving unit in a direction substantially perpendicular to the optical axis of the optical system, the spatial image of the photoelastic interference fringe having substantially the same size as the lens 1 to be inspected is partially divided into several parts. By observing at 12, measurement is performed. This is the same as the above-described FIG. 4 and the description thereof.

The lens 16 according to the present embodiment is a set lens having a variable focal length constituted by a plurality of lenses.
By changing the distance between the constituent lenses, the focal length as a set lens can be changed, and the imaging magnification can be changed. If the position of the lens 16 is adjusted in advance so that an imaging relationship is established with the vicinity of the lens 1 to be inspected, the imaging magnification of the imaging optical system 13 can be changed while maintaining the imaging relationship. It is.

As shown in FIG. 8, for example, as shown in FIG. 8, the interval between the interference fringes in the central portion 1c of the lens to be inspected is large, and the interval between the interference fringes is small in the peripheral portion 1e. And the interval between the interference fringes is
Or smaller than the pixel size. In such an area, even if the birefringence changes significantly in one pixel of the CCD camera 12 (an area corresponding to one pixel), the average value is output as a measured value in that pixel. , The reliability of the measured values in that region is reduced. In this regard, in the measuring apparatus of the present embodiment, in the region where the interval between the interference fringes is narrow, the focal length of the lens 16 is set to be long, and the imaging magnification of the imaging optical system 13 is increased to increase the interference. By performing the measurement with the fringes enlarged, more accurate measurement can be performed over the entire surface of the lens 1 to be measured.

The setting state of the birefringence measuring apparatus in the case of the fifth embodiment is exactly the same as that of the above-described second embodiment, and the actual measurement is the same as that of the above-described first embodiment. Therefore, the explanation is referred to here, and the explanation is omitted here.

As described above, according to the present embodiment,
The birefringence of the entire lens 1 to be measured can be measured without lowering the resolution.

A sixth embodiment of the present invention will be described with reference to FIG. The same parts as those shown in FIG. 3 of the embodiment are denoted by the same reference numerals, and description thereof will be omitted. In the present embodiment, the light receiving side displacement means 34 such as the base 31, the guide 32, and the stepping motor 33 in FIG. 3 of the above embodiment is omitted, and a single light receiving unit 26 of FIG. Light receiving units 26
a and 26b are different from FIG. That is, the light receiving unit 26a is a λ / 4 plate 14a,
The light receiving unit 26b includes a λ / 4 plate 14b, a polarizing plate 15b, a lens 16b, a CCD, and a polarizing plate 15a, a lens 16a, a CCD camera 12a, and a rotating unit 21a.
It comprises a camera 12b and a rotating means 21b. Here, the lens 1 to be inspected is located downstream of the lens 1 to be inspected.
From the transmitted light from the light receiving unit 2
Prism 5 as a branching means for entering light into 6a and 26b
1 is provided. Regarding the separation of the light transmitted through the lens to be inspected by the prism 51, P-polarized light (light that vibrates in a direction parallel to the reflection surface of the prism 51) due to reflection on the prism surface.
The angle of incidence of the transmitted light of the lens to be measured on the prism reflecting surface is adjusted so that there is no phase jump difference between the S-polarized light and the S-polarized light (light oscillating in the direction perpendicular to the reflecting surface of the prism 51). It is set larger than the Brewster angle. Note that fixed focus lenses are used as the lenses 16a and 16b, and the vicinity of the lens 1 to be inspected and the CCD cameras 12a and
The positions are adjusted so that the image pickup surface 2b and the image pickup surface 2b are substantially in an image forming relationship. As a material, a material from which birefringence is almost removed, such as a glass lens, is used.

In such a configuration, the two light receiving units 26a and 26b are connected to the test lens 1 with respect to the transmitted light transmitted through the test lens 1 and branched by the prism 51.
By arranging them so that transmitted light from different measurement areas is incident, measurement can be performed simultaneously on different measurement areas of the lens 1 to be measured, and measurement operability is improved. As a measuring method, two CCD cameras 1
The images taken by 2a and 12b are input to the image input device 25.
a, 25b to the personal computer 23, and the processing contents are the same as in the above embodiment. Therefore, according to the present embodiment, the light receiving unit 2
The entire surface of the test lens 1 can be measured simultaneously without moving the lenses 6a and 26b.

As a modification of the structure of the present embodiment, the lenses 16a and 16b are, as in the case of the first embodiment, set as variable focal length lenses composed of a plurality of lenses. By changing the distance between the constituent lenses, the focal length as a set lens may be changed, and the imaging magnification may be independently and freely variable. That is, the lens 1 is set so that an imaging relationship is established with the vicinity of the lens 1 to be inspected.
If the positions of 6a and 16b are adjusted in advance, it is possible to change the imaging magnification of the imaging optical systems 13a and 13b in each of the light receiving units 26a and 26b while maintaining the imaging relationship. Thereby, each light receiving unit 26
In the area where the interference fringes are narrowed in the area to be measured by a and 26b, the focal length of the lens 16a or the lens 16b is set to be long, and the imaging optical system 13a,
13b with the imaging magnification increased and interference fringes enlarged.
By causing the CD cameras 12a and 12b to form an image and perform the measurement, more accurate measurement can be performed in any of the light receiving units 26a and 26b.

Note that the actual measurement in this embodiment is exactly the same as that in the first embodiment described above, so that the description is referred to and the description is omitted here.

A seventh embodiment of the present invention will be described with reference to FIGS. In the present embodiment, the focal length (and thus the imaging magnification of the imaging optical system 13) is determined for the lens 16 whose focal length can be varied (the same applies to the lenses 16a and 16b having the variable focal length in the above-described modified example). ) Is automatically set.

First, an image of the photoelastic interference fringes 52 of the test lens 1 captured by the CCD camera 12 is, for example, as shown in FIG. E indicates an area observed by the CCD camera 12. FIG. 11 shows the pixel density distribution of the image in the cross section taken along the line AA ′ in this case. The interval between the minimum values (or the maximum values) of the pixel density distribution in FIG. 11 can be regarded as the interval between the interference fringes. In the example shown in FIG. 11, it corresponds to the interval between the points B and B ', and this interval corresponds to 10 pixels of the CCD camera 12. Since such an imaging result is obtained, the interval between the minimum values (or the maximum values) of the pixel density distribution is, for example, “If the interval is not larger than 5 pixels, the interval between the interference fringes is too narrow, and the measured value becomes too small. The CCD camera 12 determines the interval between the minimum values (or the maximum values).
A threshold value (for example, 5 pixels) is set with the number of pixels of
In the measurement area where the interval between the minimum values (or the maximum values) is smaller than the threshold value, the distance between the lenses of the variable focal length lens 16 is adjusted so that the interval becomes larger than the threshold value. The distance may be increased and the imaging magnification of the imaging optical system 13 may be increased.

FIG. 12 is a flowchart of a process for automatically adjusting and setting the imaging magnification based on such a principle. The “ridge line” in the figure indicates the minimum value of the pixel density (or
(Maximum value).
“X” is the minimum interval between the ridge lines in the area E observed by the CCD camera 12, and corresponds to the minimum interval between the interference fringes in the area E observed by the CCD camera 12. “S” is a threshold value of a stripe interval in units of a preset number of pixels of the CCD camera 12.

First, an image captured by the CCD camera 12 is captured (step S1). Then, as processing for obtaining the minimum fringe interval in the area E observed by the CCD camera 12, averaging processing (smoothing) is performed on neighboring pixels (S2), and a ridge line is detected (S3). By removing unnecessary ridge lines and thinning them (S4), the minimum ridge line interval X is detected (S5). The detected minimum ridge line interval X is compared with a threshold value S (S6), and if smaller (shorter) than the threshold value S, the image forming magnification is increased (S6).
7) is repeated, and finally, the minimum ridge line interval X becomes the threshold value S
In the above state, the measurement of birefringence as described above is started. Therefore, according to the present embodiment, it is possible to improve the operability as a measuring device and to optimize the imaging magnification.

For the lens 16 composed of a lens group having a variable focal length, the distance between the constituent lenses can be adjusted, for example, by mounting each constituent lens on a stage and moving the stage using a motor as a drive source. 1
The adjustment may be performed so that the focal length as a group lens changes while maintaining the image forming relationship between the vicinity of and the imaging surface of the CCD camera 12. Alternatively, a zoom mechanism of a commercially available zoom lens may be used.

An eighth embodiment of the present invention will be described with reference to FIG. In this embodiment, the same portions as those shown in FIG. 3 in the description of the above-described second embodiment are denoted by the same reference numerals, and description thereof will be omitted. The difference between the second embodiment and the present embodiment is that the test lens 1 to be measured in the present embodiment has a main scanning direction (a direction parallel to the paper) and a sub-scanning direction (a direction parallel to the paper). (Perpendicular to the direction) is a non-axisymmetric lens having a different focal length. This non-axisymmetric lens is held by a holder (not shown).
An irradiation optical system 2 for irradiating the test lens 1 with light in a predetermined polarization state is provided for the test lens 1. The irradiation optical system 2 is different from the second embodiment described above in that a semiconductor laser 3 that emits a linearly polarized light beam having a short coherent length and a λ / that converts linearly polarized light from the semiconductor laser 3 into circularly polarized light. Four plates 4, a lens 9,
And a pinhole 10. Regarding the light source of this type of measuring device, it is desirable to use a monochromatic laser light source rather than a white light source mixed with several wavelengths of light because the polarizing plate 15 and the like have wavelength dependence. However, when a laser light source having a long coherent length, such as a He-Ne laser, is used, in addition to the photoelastic interference fringes generated by the birefringence of the lens 1 to be measured, due to multiple reflections in the measurement optical system, etc. Noise interference fringes occur and overlap with photoelastic interference fringes, which may cause measurement errors. In this regard, in the present embodiment, since the semiconductor laser 3 having a short coherent length is used as the light source, an effect of making it difficult to generate noise interference fringes due to multiple reflection or the like in the measurement optical system is also obtained.

A correction lens 54 constituting a correction optical system 53 is provided on the optical axis between the irradiation optical system 2 and the lens 1 to be measured. The correction lens 54 has a characteristic opposite to that of the lens 1 in the main scanning direction and the sub-scanning direction, that is, has a refractive power only in the sub-scanning direction (a direction perpendicular to the paper surface). 1
It has a function to convert the light transmitted through into a parallel light flux. The correction lens 54 is also mounted on a stage 55 movable in the optical axis direction, and moves forward and backward in the optical axis direction by rotation of a stepping motor (not shown) for driving the stage 55. Here, a correction system displacement hand throw is configured by the stage 55 and the stepping motor, and the position (distance) of the correction lens 54 with respect to the test lens 1 in the optical axis direction is adjustable. In addition, the stepping motor is provided with a rotation origin position sensor. If the distance between the correction lens 54 and the lens 1 to be measured is set to a predetermined distance in advance and the state is set as the movement origin of the stage 55, the By counting the number of pulses supplied to the motor, a change in the distance between the correction lens 54 and the test lens 1 due to the movement of the stage 55 can be detected (actually,
This distance is detected based on the counting operation of the number of pulses in the personal computer, which will be described later.

The operation of the correcting lens 54 of the correcting optical system 53 for collimating the transmitted light of the test lens 1 added according to the present embodiment will be described with reference to FIG.
Basically, when the test lens 1 is an axially symmetric lens, the focus of the lens 9 and the focus of the test lens 1 can be substantially matched without providing the correction lens 54, so that Since the test lens 1 forms an afocal system,
The light transmitted through the lens 1 to be examined is almost collimated. However, when the test lens 1 is a non-axisymmetric lens having different focal lengths in the main scanning direction and the sub-scanning direction as used in the present embodiment, the focus of the lens 9 and the lens 1 Since the focal points in the main and sub-scanning directions cannot be made coincident with each other, it is difficult to irradiate an axisymmetric spherical wave to collimate the light transmitted through the lens to be measured.
In this regard, in the present embodiment, the correcting lens 54 having refractive power only in the sub-scanning direction is disposed between the lens 9 and the lens 1 to be tested, and the divergent light from the lens 9 is converted into non-axisymmetric light After the conversion, the test lens 1 is irradiated.

Here, as shown in FIG. 14, the focal length of the test lens 1 in the main scanning direction is f1, the focal length in the sub-scanning direction is f2 (where f1> f2), and the focal length of the lens 9 is fo, the focal length of the correction lens 54 in the sub-scanning direction is fs (the focal length in the main scanning direction is infinite), the thickness is t,
When the refractive index is ns, the distance between the lens 9 and the test lens 1 (distance between principal points) is △ 1, and the distance between the correction lens 54 and the test lens 1 is △ 2, (11) (12) If the intervals △ 1 and △ 2 are set to satisfy the expression
Light transmitted through 1 is almost collimated.

[0109]

(Equation 9)

Here, such an interval is set, for example, by setting the state in which the lens 9 and the test lens 1 and the correction lens 54 and the test lens 1 are physically closest to each other as the origin of each movement. By moving the stages 11 and 55 from the movement origin, the distance between the lens 9 and the lens
1. The distance △ 2 between the correction lens 54 and the lens 1 to be measured can be detected. However, when the type of the lens 1 to be inspected is limited, it is not necessary to move the correction lens 54 in the optical axis direction.
The optical system may be set in advance so that the intervals △ 1 and △ 2 satisfy the expression (2).

A ninth embodiment of the present invention will be described with reference to FIG. The same portions as those described in the eighth embodiment are denoted by the same reference numerals, and description thereof is omitted. The test lens 1 to be measured in the present embodiment is assumed to have a very long focal length. In this case, in order to form an afocal system with the lens 9 and the lens 1 to be inspected, it is necessary to set a very large interval between the two, and there is a problem that the apparatus becomes large. However, if such a test lens 1 is regarded as a flat plate whose both surfaces are substantially parallel, and the parallel light is emitted, it is possible to avoid an increase in the size of the measuring apparatus. In the present embodiment, an example is shown in FIG.

That is, in FIG. 15, a correction lens 54 constituting a correction optical system 53 is provided on the optical axis between the lens 9 of the irradiation optical system 2 and the lens 1 to be measured. ing. The correcting lens 54 is an ordinary axially symmetric convex lens having a function of converting the light irradiated to the test lens 1 and the transmitted light into a parallel light flux. Such a correction lens 54 is also mounted on the stage 55 so as to be movable and adjustable in the optical axis direction.

With such a configuration, the divergent light from the lens 9 is converted into a parallel light beam by the correcting lens 54, and then emitted to the lens 1 to be measured. At this time, since the test lens 1 is not actually a parallel flat plate, the light transmitted through the test lens 1 is shifted from the parallel light flux and becomes a divergent or convergent light flux, but the focal length of the test lens 1 is sufficient. In this case, the deviation of the transmitted light from the test lens 1 from the parallel light beam becomes a very small angle, so that the error caused by the deviation can be ignored. Therefore, even if the test lens 1 to be measured has a very long focal length, measurement can be performed without increasing the size of the apparatus, and versatility can be improved.

Here, in the present embodiment, for example,
The test lens 1 has a different focal length between the main scanning direction and the sub-scanning direction, and can be regarded as a parallel plate in the main scanning direction.
If the correction optical system 53 cannot be regarded as a parallel flat plate in the sub-scanning direction, the correction optical system 53 may be configured as a combination of the correction lens 54 and another correction lens 56. The correcting lens 56 has a different optical characteristic from the correcting lens 54. Here, a non-axisymmetric lens having a refractive power only in the sub-scanning direction is used. According to this, the test lens 1
Lens 1 to be inspected so that the light beam transmitted through
Can be irradiated with light.

Therefore, considering a general theory, if a correction optical system is configured by combining a plurality of optical elements (usually lenses) having different optical characteristics, it is possible to cope with a lens having a very long focal length. The transmitted light can be made substantially parallel to a non-axisymmetric test lens, and the versatility is enhanced.

For example, in the configuration shown in FIG.
The correction lenses 54 and 56 can be detachable,
If it is configured to be interchangeable with a different type (lens having a different focal length or aperture), the range of response to a change in the type of the test lens 1 is expanded, and versatility is further enhanced.

The tenth embodiment of the present invention will be described with reference to FIG. This embodiment can be applied to the eighth embodiment as shown in FIG. 13, but here, it is applied to a birefringence measuring apparatus and a measuring method as shown in FIG. Have been. In the present embodiment, the stage 57 on which the lens 1 to be measured can move in a direction orthogonal to the optical axis thereof.
And is moved in a direction perpendicular to the optical axis by rotation of a stepping motor (not shown) for driving the stage 57. Here, a lens displacement means is constituted by the stage 57 and a stepping motor, and the position of the lens 1 to be measured can be freely adjusted in the direction orthogonal to the optical axis according to the measurement target area on the lens 1 to be measured. Have been.

In such a configuration, by moving the lens 1 to be inspected in the direction perpendicular to the optical axis by the stage 57, the incident position of the parallel light beam from the correction optical system 53 to the lens 1 is gradually changed. The measurement is performed while dividing the entire area of the lens 1 to be measured. That is, the method is the same as the method of performing split measurement by moving the light receiving unit 26 side in the direction perpendicular to the optical axis in accordance with the measurement target area described with reference to FIG. The lens 1 is replaced so as to be movable.

The birefringence measuring apparatus and the measuring method according to the present invention have been clarified by all the embodiments described above.

[0120]

According to the present invention, the birefringence measuring apparatus according to the first aspect and the sixth aspect of the present invention are constructed as described above.
According to the refraction measurement method of the invention described, basically, according to the rotation analyzer method, the transmitted light transmitted through the lens to be measured is incident on the polarization element that changes the polarization state, and the polarization element is rotated. The birefringence of the lens to be measured is calculated by detecting the light received by the array of light receiving elements while allowing the lens to be illuminated. By adjusting the distance between the test lens and the irradiation optical system while observing the test lens transmission image, photoelastic interference fringes, which are test lens transmission images that are less affected by optical distortion, can be obtained. , The birefringence can be accurately measured over the entire surface of the lens to be inspected, and at the same time, the type of the lens to be inspected can be easily changed.
A highly versatile birefringence measuring device or method can be provided.

According to the birefringence measuring device according to the second and third aspects and the birefringence measuring method according to the seventh aspect,
Since the polarizing element, the imaging optical system, and the light receiving element are integrally moved in a direction substantially perpendicular to the optical axis, that is, moved in the longitudinal direction of the lens to be measured, the measurement can be performed while dividing the lens. It is possible to provide a birefringence measurement device or method capable of inexpensively measuring refraction without lowering the resolution.

According to the birefringence measurement apparatus of the invention described in claim 4 and the birefringence measurement method of the invention described in claim 8, the lens to be inspected may be a scanning lens used for optical writing. Basically, the measurement system can be set to a state close to actual use by a configuration in which the distance between the test lens and the irradiation optical system can be set arbitrarily. By adjusting the angle of the polarizing element and the like integrally, the light can be incident in a state close to perpendicular, and a birefringence measuring apparatus or method capable of performing more accurate measurement can be provided.

According to the birefringence measuring device of the fifth aspect and the birefringence measuring method of the ninth aspect, when light transmitted through the periphery of the lens to be measured enters the light receiving element as stray light, the measurement is performed. However, since a light-blocking member is provided for such a peripheral portion, it is possible to eliminate the influence of stray light, to eliminate an unmeasurable area, and to enable measurement over the entire surface of the lens to be measured. In particular, it is possible to provide a birefringence measuring apparatus or method capable of completely removing the influence of stray light in a form suitable for the lens to be inspected by appropriately moving the light shielding member by the light shielding member moving means. .

According to the tenth aspect, the irradiation optical system for irradiating the test lens with the divergent light in a predetermined polarization state, and the irradiation for moving and adjusting the position of the irradiation optical system with respect to the test lens in the optical axis direction. Side displacement means, a polarizing element for changing the polarization state of the transmitted light from the lens to be measured, a rotating means for rotating the polarizing element substantially in the traveling direction of the transmitted light, and a rotation angle of the polarizing element by the hand throw A rotation angle detection hand that detects the light, an array-shaped light-receiving element that receives the light transmitted through the polarizing element, and a variable imaging magnification that forms an image of the light transmitted through the polarizing element almost on the light-receiving surface of the light-receiving element. Imaging optics,
A light receiving side displacement unit that integrally adjusts the polarization element, the rotation unit, the light receiving element, and the imaging optical system as a light receiving unit in a direction substantially orthogonal to the optical axis, and a rotation angle detected by the rotation angle detection unit. And calculating means for calculating the birefringence of the test lens based on the light receiving output detected and detected by the light receiving element. Is limited by the size (area of the element). To receive transmitted light from the entire lens having a large diameter such as a lens used in an optical writing system, a general polarizing element or a light receiving element may be used. It is difficult in terms of size, and if a polarizing element or a light receiving element having a large size is used, the manufacturing cost increases. On the other hand, if the transmitted light from the entire test lens is optically reduced according to the size of a general polarizing element or light receiving element, the optical system becomes complicated, and the spatial image of the photoelastic interference fringes is increased. Becomes smaller,
Accordingly, the spatial resolution of the measurement is reduced. In this regard, since the polarizing element, the imaging optical system, and the light receiving element can be integrally measured as a light receiving unit while moving and splitting in a direction substantially orthogonal to the optical axis, that is, in the longitudinal direction of the lens to be measured, Measurement of the entire birefringence can be realized at low cost without lowering the resolution. At this time, when several lenses to be measured are measured or when one lens to be measured is divided into several areas to be measured, birefringence may be generated depending on the lens to be measured or the location of the lens to be measured. May be different. In particular, since the interval between the interference fringes differs depending on the state of occurrence of birefringence, the reliability of the measurement decreases in a region where the interval between the interference fringes is close to or smaller than the size of the minimum unit pixel of the light receiving element. . In this regard,
Since the imaging magnification of the imaging optical system is variable, by setting the imaging magnification optimally in accordance with the state of birefringence that varies depending on the lens to be inspected or the location of the lens to be inspected, Accurate measurement can be performed regardless of the state of occurrence of refraction. In other words, the birefringence measurement can be accurately performed over the entire surface of the lens to be inspected, and at the same time, the type of the lens to be inspected can be easily changed and a highly versatile birefringence measuring apparatus can be provided. Above, regardless of the state of occurrence of birefringence, by setting the imaging magnification of the imaging optical system optimally in accordance with the state of occurrence of birefringence depending on the lens to be inspected or the location of the lens to be inspected A birefringence measuring device or method capable of performing accurate measurement can be provided.

According to the eleventh aspect of the present invention, it is basically the same as the tenth aspect of the invention, except that a plurality of light receiving units are provided, and the transmitted light from the lens to be inspected is split by the branching means. Since the light is branched and directed toward each light receiving unit, even if the lens to be measured is a lens having a large diameter such as a lens used in an optical writing system, the resolution is not reduced and the light is not received. It is possible to simultaneously measure the entire test lens without moving the unit side.
In other words, since a plurality of light receiving units are provided, it is possible to provide a birefringence measuring device or method capable of simultaneously measuring the entire test lens without moving the light receiving unit side.

According to a twelfth aspect of the present invention, each of the light receiving units of the birefringence measuring device according to the eleventh aspect is arranged with respect to the branching means so as to receive transmitted light from a different measurement area of the lens to be measured. Since it is provided, it is possible to provide a birefringence measuring apparatus or method capable of simultaneously measuring the entire test lens with high efficiency and operability.

According to the thirteenth aspect of the present invention, when one test lens is divided into several test areas and measured simultaneously, even in the same test lens, for example, the vicinity of the lens center and the lens peripheral portion In many cases, since the cooling rate of the temperature in the lens molding is different, the way in which birefringence occurs is often different. For this reason, for example, the interval between the photoelastic interference fringes may be large near the center of the lens, and the interval between the photoelastic interference fringes may be small near the periphery, and the interval between the interference fringes may be close to the pixel size of the light receiving element, or In an area smaller than the size, the reliability of the measurement decreases. In this regard, since the imaging magnification of each imaging optical system can be changed independently for each light receiving unit, the occurrence of birefringence that varies depending on the lens to be measured or depending on the position of the lens to be measured in the measurement area. By optimally setting the imaging magnification for each light receiving unit according to the state, it is possible to provide a birefringence measuring apparatus or method capable of performing more accurate measurement regardless of the state of occurrence of birefringence.

According to the fourteenth aspect of the present invention, the imaging magnification is automatically adjusted based on the transmitted image of the test lens obtained when the transmitted light from the test lens is formed substantially on the light receiving surface of the light receiving element. Is set. Since the appropriate imaging magnification is automatically set based on the interval data of the interference fringes in the actual transmitted image from the lens to be inspected, etc., the operability as a measuring device is improved and the imaging magnification is optimized. A birefringence measurement device or method can be provided which can also be achieved.

According to the fifteenth aspect of the invention, basically, according to the rotation analyzer method, the light is transmitted to the polarizing element for changing the polarization state of the transmitted light transmitted through the lens to be measured, and this polarizing element is The birefringence of the test lens is calculated by detecting the light received by the array of light receiving elements while rotating, but the distance between the irradiation optical system that irradiates the test lens with divergent light and the test lens can be set arbitrarily. By adjusting the distance between the test lens and the irradiation optical system while observing the transmission image of the test lens, it is possible to obtain a photoelastic interference fringe that is a transmission image of the test lens having a small influence of optical distortion. Birefringence can be accurately measured over the entire surface of the lens. At this time, even if the lens to be inspected has a different focal length between the main scanning direction and the sub-scanning direction, for example, a lens having a different focal length between the main scanning direction and the sub-scanning direction is provided downstream of the irradiation optical system. By adding a correction optical system and making the light flux transmitted through the test lens substantially parallel, the above-described birefringence measurement can be performed without impairing the normal operation of the optical element after the polarizing element,
It is possible to provide a birefringence measuring device or method with increased versatility.

According to a sixteenth aspect of the present invention, the correcting optical system in the birefringence measuring device according to the fifteenth aspect is composed of a combination of a plurality of optical elements having different optical characteristics. Not only when the focal length is different from the direction but also when the focal length is long, for example,
Like a combination of a non-axisymmetric lens and a normal axisymmetric lens, the correction optical system is composed of multiple optical elements with different optical characteristics, making it possible to respond to changes in the type of lens to be inspected. It is possible to provide a birefringence measuring device or method which is more versatile.

According to a seventeenth aspect of the present invention, in the birefringence measuring apparatus according to the fifteenth or sixteenth aspect, a lens displacement means for moving and adjusting the test lens in a direction orthogonal to its optical axis is provided. Even if the focal length of the lens is long, moving the lens to be examined in a direction perpendicular to the optical axis makes it possible to divide and measure the entire area of the lens to be measured. Thus, it is possible to provide a birefringence measuring apparatus or method capable of inexpensively measuring the birefringence of the entire lens to be measured without lowering the resolution.

In the method for measuring birefringence according to the present invention, the distance in the optical axis direction of the irradiation optical system with respect to a test lens disposed so as to be movable at a predetermined position in a direction perpendicular to the optical axis can be arbitrarily set. After the adjustment, while adjusting the position of the lens to be measured in the direction orthogonal to the optical axis according to the region to be measured on the lens to be measured, a predetermined polarization by the irradiation optical system is applied to the region to be measured of the lens to be measured. The light in the state is applied to the test lens through the correction optical system to emit substantially parallel transmitted light, and the polarization element that changes the polarization state of the transmitted light from the test lens is rotated around the traveling direction of the transmitted light. The rotation angle is detected while rotating, and the light transmitted through this polarization element is imaged almost on the light receiving surface of the array of light receiving elements by the imaging optical system, and the detected rotation angle of the polarization element and the light receiving element are detected. Received light detected by Since the birefringence of the measurement target area of the test lens is sequentially calculated based on the force, the polarization state of the transmitted light transmitted through the test lens is basically changed according to the rotation analyzer method. The birefringence of the test lens is calculated by making the light incident on the polarizing element and detecting the light received by the light receiving element in an array while rotating the polarizing element.
The distance between the irradiation optical system that irradiates the test lens with divergent light and the test lens can be set arbitrarily, and the distance between the test lens and the irradiation optical system is adjusted while observing the transmission image of the test lens. Since a photoelastic interference fringe, which is a transmitted image of the test lens with little influence of optical distortion, is obtained, birefringence measurement can be accurately performed over the entire surface of the test lens. At this time, even if the lens to be inspected has a different focal length between the main scanning direction and the sub-scanning direction, for example, a lens having a different focal length between the main scanning direction and the sub-scanning direction is provided downstream of the irradiation optical system. By adding a correction optical system so that the luminous flux transmitted through the lens to be inspected is almost parallel, the above-described birefringence measurement can be performed without impairing the normal operation of the optical element after the polarization element, and versatility is improved. Increase. In addition, even when the focal length of the test lens is long, by moving the test lens in a direction perpendicular to its optical axis, it is possible to perform a divided measurement of the entire area of the test lens. Thus, it is possible to provide a birefringence measuring apparatus or method capable of inexpensively measuring the birefringence of the entire lens to be measured without lowering the resolution.

[Brief description of the drawings]

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

FIG. 2 is a characteristic diagram showing a rotation angle-light intensity characteristic of a polarizing plate.

FIG. 3 is a configuration diagram showing second and fifth embodiments of the present invention.

FIG. 4 is a front view showing how a region to be measured is divided.

FIG. 5 is a configuration diagram showing a third embodiment of the present invention.

FIG. 6 is a side view of an example of a shape of a lens to be inspected, showing a fourth embodiment of the present invention.

FIG. 7 is a structural diagram showing a light shielding structure.

FIG. 8 is a front view showing an example of a photoelastic interference fringe due to birefringence of the test lens of the present invention.

FIG. 9 is a configuration diagram showing a sixth embodiment of the present invention.

FIG. 10 is a front view illustrating a state in which a CCD camera captures an image of photoelastic interference fringes according to a seventh embodiment of the present invention.

FIG. 11 is a characteristic diagram showing a pixel density distribution in a cross section taken along line AA ′.

FIG. 12 is a flowchart illustrating an automatic setting process of an imaging magnification.

FIG. 13 is a configuration diagram illustrating an eighth embodiment of the present invention.

14A and 14B are diagrams for explaining the operation of the correction optical system, where FIG. 14A is a plan view as viewed in a main scanning direction, and FIG. 14B is a side view as viewed in a sub-scanning direction.

FIG. 15 is a configuration diagram showing a ninth embodiment of the present invention.

FIG. 16 is a configuration diagram showing a tenth embodiment of the present invention.

FIG. 17 is a configuration diagram schematically showing an optical system configuration for explaining a defect of a conventional measurement system.

FIG. 18 is an explanatory diagram showing a state of a corresponding photoelastic interference fringe.

FIG. 19 is a plan view schematically showing a configuration example of an optical system for optical writing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Test lens 2 Irradiation optical system 3 Light source 12 Light receiving element 13 Imaging optical system 15 Polarizing element 21 Rotating means 34 Light receiving side displacement means 35 Angle variable means 42 Light shielding member 44 Light shielding member moving means 51 Branching means 53 Correction optical system

Claims (18)

[Claims] 1. An irradiation optical system for irradiating a test lens with divergent light in a predetermined polarization state, irradiation side displacement means for moving and adjusting a position of the irradiation optical system with respect to the test lens in an optical axis direction, A polarizing element for changing the polarization state of the transmitted light from the lens to be inspected; a rotating means for rotating the polarizing element substantially in the traveling direction of the transmitted light; and a rotation for detecting a rotation angle of the polarizing element by the rotating means. An angle detecting unit, an array-shaped light receiving element that receives light transmitted through the polarizing element, an imaging optical system that forms an image of the light transmitted through the polarizing element on the light receiving element, and the rotation angle detecting unit. A birefringence measuring device comprising: a calculation hand for calculating a birefringence of the test lens based on the detected rotation angle and a light reception output detected by the light receiving element. 2. The birefringence measuring apparatus according to claim 1, further comprising a light receiving side displacement means for integrally moving the polarizing element, the imaging optical system, and the light receiving element in a direction substantially perpendicular to the optical axis. 3. The birefringence measuring apparatus according to claim 2, further comprising a distance detecting means for detecting a moving distance by the light receiving side displacement means. 4. An angle varying means for integrally varying a polarizing element, an imaging optical system and a light receiving element with respect to an advancing direction of transmitted light from a test lens, and an angle detecting means for detecting the angle. The birefringence measuring device according to claim 1, 2 or 3. 5. The birefringence according to claim 1, further comprising: a light-shielding member that shields light transmitted through a peripheral portion of the lens to be inspected; and a light-shielding member moving unit that moves a position of the light-shielding member. measuring device. 6. A divergent light of a predetermined polarization state by the irradiation optical system with respect to the test lens while arbitrarily adjusting a distance of the irradiation optical system with respect to the test lens disposed at a predetermined position in an optical axis direction. Irradiating the polarizing element that changes the polarization state of the transmitted light from the test lens while rotating the polarizing element substantially in the direction of travel of the transmitted light, detecting the rotation angle thereof, and forming an image of the light transmitted through the polarizing element. An image is formed on the light receiving surface of the array of light receiving elements by the optical system, and the birefringence of the lens to be measured is calculated based on the detected rotation angle of the polarizing element and the received light output detected by the light receiving element. Birefringence measurement method. 7. The polarizing element, the imaging optical system, and the light receiving element are integrally movable and adjustable in a direction substantially perpendicular to the optical axis, and are moved and adjusted in accordance with a measurement target area on the lens to be measured. The method for measuring birefringence according to claim 6. 8. A light that is integrally formed with a polarizing element, an image forming optical system, and a light receiving element so as to be variable in angle with respect to a traveling direction of light transmitted from a lens to be measured, and is transmitted through a measurement target area on the lens to be measured. 8. The method for measuring birefringence according to claim 6, wherein the angle is adjusted in accordance with the angle of the birefringence. 9. A light-shielding member for shielding light transmitted through a peripheral portion of the test lens, and the position of the light-shielding member is arbitrarily adjusted and set so that stray light generated by transmitting through the peripheral portion is eliminated. The method for measuring birefringence according to claim 6. 10. An irradiation optical system for irradiating a test lens with divergent light in a predetermined polarization state, irradiation side displacement means for moving and adjusting a position of the irradiation optical system with respect to the test lens in an optical axis direction, A polarizing element for changing the polarization state of the transmitted light from the lens to be inspected; rotating means for rotating the polarized light element substantially in the traveling direction of the transmitted light; and detecting a rotation angle of the polarizing element by the manual throw. A rotation angle detection hand, an array-shaped light receiving element that receives light transmitted through the polarizing element, and an imaging magnification that forms an image of the light transmitted through the polarizing element almost on a light receiving surface of the light receiving element is variable. An imaging optical system; a light receiving side displacement unit that integrally adjusts the polarization element, the rotation unit, the light receiving element, and the imaging optical system as a light receiving unit in a direction substantially orthogonal to the optical axis; and the rotation angle detection unit. Detected by Birefringence measuring apparatus and a calculating means for calculating the birefringence of the subject lens on the basis of the light reception output rotation angle to be received and detected by the light receiving element. 11. An irradiation optical system for irradiating a test lens with divergent light in a predetermined polarization state; irradiation-side displacement means for moving and adjusting a position of the irradiation optical system with respect to the test lens in an optical axis direction; A polarizing element for changing the polarization state of the transmitted light from the lens to be inspected; a rotating hand for rotating the polarizing element substantially in the traveling direction of the transmitted light; and detecting a rotation angle of the polarizing element by the rotating means. A rotation angle detection hand casting, an array-shaped light receiving element that receives light transmitted through the polarizing element, and an imaging optical system that forms an image of light transmitted through the polarizing element substantially on a light receiving surface of the light receiving element. A plurality of light receiving units as one unit; branching means for branching transmitted light from the lens to be inspected to be incident on each of the light receiving units; Birefringence measuring apparatus and a calculating means for calculating the birefringence of the lens under test based on the received light output which is received and detected by the rotation angle and the light receiving element is. 12. The birefringence measuring apparatus according to claim 11, wherein each of the light receiving units is provided to the branching means so as to receive transmitted light from a different measurement area of the lens to be measured. 13. The image forming optical system is capable of changing the image forming magnification independently for each light receiving unit.
The birefringence measuring device according to the above. 14. An image forming optical system automatically sets an image forming magnification based on a transmitted image of the test lens obtained when the transmitted light from the test lens is formed substantially on the light receiving surface of the light receiving element. 14. The birefringence measurement device according to claim 10, wherein the measurement is performed. 15. An irradiation optical system that irradiates a test lens with light in a predetermined polarization state; an irradiation-side displacement hand that moves and adjusts a position of the irradiation optical system with respect to the test lens in an optical axis direction; A correction optical system that is disposed on the irradiation side of the lens to be examined and converts a light beam transmitted through the lens to be examined into substantially parallel light; a polarizing element that changes a polarization state of light transmitted from the lens to be examined; Rotating means for rotating the element about the traveling direction of the transmitted light; rotation angle detecting means for detecting a rotation angle of the polarizing element by the rotating means; and an array for receiving light transmitted through the polarizing element. A light receiving element; an imaging optical system that forms an image of light transmitted through the polarizing element on substantially a light receiving surface of the light receiving element; a rotation angle detected by the rotation angle detection unit and light reception detected by the light receiving element Received light Birefringence measuring apparatus and a calculating means for calculating the birefringence of the subject lens on the basis of and. 16. The birefringence measurement apparatus according to claim 15, wherein the correction optical system is composed of a combination of a plurality of optical elements having different optical characteristics. 17. A lens displacing means for moving and adjusting said lens to be examined in a direction orthogonal to the optical axis thereof.
Or the birefringence measurement device according to 16. 18. A method for arbitrarily adjusting a distance in an optical axis direction of an irradiation optical system with respect to a test lens disposed so as to be movable in a direction orthogonal to the optical axis at a predetermined position, and then performing measurement on the test lens. While adjusting the position in the direction orthogonal to the optical axis of the lens to be inspected in accordance with the target area, light of a predetermined polarization state by the irradiation optical system is passed through the correction optical system with respect to the measurement target area of the lens to be inspected. By irradiating the test lens with transmitted light that has been converted into substantially parallel light, the polarizing element that changes the polarization state of the transmitted light from the test lens is rotated around the traveling direction of the transmitted light while rotating the polarizing element. The rotation angle is detected, and the light transmitted through the polarization element is focused on the light receiving surface of the array of light receiving elements by an imaging optical system, and the detected rotation angle of the polarization element and the light reception detected by the light receiving element are detected. Received light output and A birefringence measuring method for sequentially calculating the birefringence of the measurement target area of the test lens based on