JP2020060480A - Eccentricity measuring method - Google Patents

Abstract

To reduce the time required for eccentricity measurement, and accurately perform eccentricity measurement on a test surface that is difficult to be measured.SOLUTION: An eccentricity measuring method measures eccentricity in a test optical system 6 formed of a plurality of lens units each including one or more lenses. The method includes: acquiring, in a first state of the test optical system, first data related to the eccentricity of a test surface in the test optical system through measurement using light from an objective optical system 5 (S1, 2); acquiring, in a second state different in interval between the lens units from the first state, second measurement data related to the eccentricity of the test surface through the measurement using the light from the objective optical system; and acquiring the eccentricity of the test surface by using the first data and second data (S3 to S7).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for measuring the amount of eccentricity of a test optical system.

  In an optical system composed of a plurality of lenses, the optical performance deteriorates because any one of the lenses is displaced from the optical axis. Therefore, it is necessary to measure the deviation (eccentricity) of the lens from the optical axis with high accuracy, readjust the lens arrangement, and review the lens manufacturing process. As a method for measuring the eccentricity, there is an autocollimation method. In this method, a part of the optical system is driven in the direction of the optical axis to project the index on the apparent center of curvature of the surface to be inspected, and the inspection is performed based on the position of the reflection image from the surface to be inspected with respect to the measurement reference axis. Calculate the amount of eccentricity of the surface.

  In Patent Document 1, light from a light source is irradiated onto a surface to be inspected of an optical system to be inspected through an optical system that adjusts a condensing position, and a reflection image is taken in a state where the optical system to be inspected is rotated and reflected. A method of determining the amount of eccentricity of the surface to be inspected by measuring the rotation radius and the rotation direction of the image is disclosed.

  Further, in Patent Document 2, when a part of the optical system to be inspected is driven in a direction orthogonal to the optical axis without rotating the optical system to be inspected and the reflection image of the inspected surface is located at the reference position. A method of measuring the amount of eccentricity of the surface to be inspected from the driving amount is disclosed. In this method, the reflected light on the surface where the light is not vertically irradiated (concentrated at the center of curvature) is diverged and the intensity is weakened and is not detected. Depending on the reflected light from the surface where the light is vertically irradiated, Only the signal obtained is obtained. Further, since the position of the reflected image from the surface to be inspected changes due to the surface eccentricity in front of the surface to be inspected, the surface eccentricity in front of the surface to be inspected is taken into consideration, and the eccentricity of the surface to be inspected by paraxial ray tracing calculation The amount is calculated.

JP, 2006-112896, A Japanese Patent No. 4474150

  Some optical systems including a plurality of lens units have a zoom function that changes the optical magnification by changing the distance between the lens units. However, since there is a risk of decentering of the lens that constitutes one of the lens units due to zooming, it is necessary to perform decentering measurement in various zoom states (for example, wide, middle, and tele).

  However, if the number of test surfaces on which eccentricity measurement is performed is large, the time required for measurement becomes long. In addition, a lens unit having a large number of lenses may have a surface to be inspected for which highly accurate decentering measurement is difficult.

  The present invention provides a method for measuring the amount of eccentricity that shortens the time required for measuring the eccentricity, and that enables accurate measurement of the eccentricity even on a surface to be measured that is difficult to measure.

  An eccentricity amount measuring method according to one aspect of the present invention is a method of measuring an eccentricity amount in an optical system to be tested, which is composed of a plurality of lens units each including one or more lenses. The method includes a first step of obtaining first data regarding decentering of a surface to be inspected in the optical system to be measured by measurement using light from the objective optical system in a first state of the optical system to be inspected. , In the second state in which the distance between the lens units is different from the first state of the optical system to be inspected, the second measurement data regarding the eccentricity of the inspected surface is obtained by the measurement using the light from the objective optical system. And a third step of acquiring the amount of eccentricity of the surface to be inspected by using the first and second data.

  A method of measuring the amount of eccentricity according to another aspect of the present invention is a method of measuring the amount of eccentricity in an optical system to be tested, which is composed of a plurality of lens units each including one or more lenses. According to the method, in a first state in which each of the plurality of lens units is a single lens unit, measurement is performed using light from the objective optical system to determine a first decentering of a surface to be inspected in the single lens unit. The first step of acquiring data and the second step of acquiring the decentering amount of the surface to be measured using the first data in the second state in which the optical system to be measured is composed of a plurality of lens units It is characterized by having.

  An apparatus for measuring the amount of eccentricity in the optical system to be tested using the above method and a computer program that causes a computer to perform the processing according to the above method also constitute another aspect of the present invention.

  According to the present invention, the time required for the eccentricity measurement can be shortened, and further, the eccentricity measurement can be accurately performed even on the surface to be measured which is difficult to measure.

The figure which shows the structure of the eccentricity measuring apparatus of Examples 1-3 of this invention. 3 is a flowchart showing an eccentricity amount measurement process of the first embodiment. 6 is a flowchart showing an eccentricity amount measuring device according to a third embodiment. The figure which shows the structure of the eccentricity measuring apparatus of Example 4.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First Embodiment FIG. 1 shows the configuration of an eccentricity measuring device that is a first embodiment of the present invention. In FIG. 1, an axis extending in the left-right direction in the figure is defined as an X-axis, a left direction with respect to an apex of a first surface of a test optical system (test lens) 6 to be described later as an origin is represented by a minus, and a right direction is represented by a plus. To do. Further, the axis extending in the vertical direction in the figure is the Y axis, and the axis extending perpendicular to the paper surface of the figure is the Z axis.

  The light from the illumination light source 1 illuminates the index chart 2. The light transmitted through the index chart 2 is transmitted through the half mirror (beam splitter) 3, is converted into parallel light by the collimator 4, passes through the objective optical system (objective lens) 5, and is irradiated onto the optical system 6 to be tested. It The light reflected by the surface 6 a of the optical system 6 to be inspected passes through the objective optical system 5 and the collimator 4 and forms an image (reflection image) on the image plane chart 7. The reflected image and the image plane chart 7 are picked up by an image sensor 9 as a light receiving sensor via an image forming lens 8.

  In the index chart 2, the small-diameter aperture forming the transmissive portion has a shape that is asymmetric with respect to the cross line, the Y axis, or the Z axis. A cross-shaped dotted line is drawn on the imaging plane chart 7, and the coordinates at which the dotted lines intersect are the origin (optical axis).

  Since the index chart 2 and the image plane chart 7 are arranged at positions equivalent to the half mirror 3, the reflected image of the index chart 2 is formed at the position of the image plane chart 7 as an inverted equal-magnification image. To be done.

  The objective optical system 5 is disposed on the drive stage 10 and is driven by the drive stage 10 in the optical axis (X) direction. The test optical system 6 is held by the rotary stage 11 and is rotated about the optical axis.

  The image sensor 9 is a CMOS camera or a CCD camera, and captures the light intensity of the reflected image of the index chart 2 reflected by the surface 6a to be inspected in the optical system 6 to be inspected. The computer 12 acquires the position coordinates of the reflection image captured by the image sensor 9, and uses this to calculate the amount of eccentricity of the test surface 6a. The computer 12 controls driving of the drive stage 10 and the rotary stage 11.

  At the time of eccentricity measurement, the objective optical system 5 is moved in the optical axis direction by the drive stage 10, and the image of the index chart 2 is projected on the apparent spherical center position of each test surface of the test optical system 6. When the test optical system 6 is rotated around the optical axis (X axis) by the rotary stage 11, the image reflected by the test surface 6a forms an arc. The radius of the arc is a value that depends on the amount of eccentricity of the surface 6a to be inspected, and the amount of eccentricity is acquired by performing paraxial approximation ray tracing calculation.

  The optical system 6 to be inspected is a zoom lens capable of zooming by changing the optical magnification, and is composed of a plurality of lens units whose mutual intervals change during zooming. Each lens unit is composed of one or more lenses. The zoom state (first and second states: hereinafter referred to as zoom state) of the optical system 6 to be inspected includes wide with low optical magnification and tele with high optical magnification.

In this embodiment and other embodiments described later, the amount of eccentricity of the surface to be inspected is measured by the autocollimation method using the light from the objective optical system 5. However, as described above, when the number of lenses forming the test optical system 6 increases, there may be a test surface on which decentering measurement is difficult. Specifically, the eccentricity measurement becomes difficult due to the following factors.
-The apparent optical axis position is too long to drive the objective optical system 5.
The objective optical system 5 interferes with the test optical system 6 because the apparent spherical center position is too short.
The reflected image is formed outside the imaging field of the image sensor 9 due to the large eccentricity of the surface to be inspected.
-The apparent spherical center positions of a plurality of surfaces to be inspected are close to each other, so that the correspondence between the reflection image and the surfaces to be inspected cannot be known.
-The reflected image is blurred due to spherical aberration.

  The first embodiment provides an eccentricity amount measuring method capable of accurately measuring the eccentricity amount of the surface to be inspected, which is difficult to measure the eccentricity as described above. Specifically, the eccentricity measurement is not performed for the surface to be measured whose eccentricity is difficult, and the eccentricity amount of the surface to be measured is calculated using the radius gyration or the eccentricity of the reflection image measured in different zoom states.

  As a premise, the eccentricity of the lens unit changes before and after the zoom state changes, but it is assumed that the relative eccentricity amount in the lens unit does not change and one reflection image in the lens unit is rotated while rotating the optical system 6 to be tested. Measure the radius of gyration of. Then, using the radius gyration of the reflected image measured before the zoom state changes, the eccentricity amount of the other unmeasured test surface in the lens unit before and after the zoom state change is obtained.

  The eccentricity amount measuring method of this embodiment will be specifically described with reference to FIG. S in the figure means a step.

  In step 1, the number of zoom states of the test optical system 6 is M, and the number of lens units forming the test optical system 6 is G. Here, as an example, it is assumed that the test optical system 6 is composed of three lens units (G = 3), and each lens unit is composed of three lenses. The number of surfaces to be inspected for eccentricity measurement is 18 because the number of lenses is 9. Further, the frontmost lens unit (the leftmost unit in FIG. 1) in the optical system 6 to be tested is the first lens unit, and the rearward lens units are the second and third lens units in order. The test optical system 6 performs zooming by changing the distance between the lens units. Here, as an example, there are three zoom states (M = 3), and each zoom state is represented by j (= 1, 2, 3).

  The radius of curvature, the surface spacing, and the refractive index of the i-th surface in zoom state j are R (i), d (i, j), and n (i), respectively. i is an integer from 1 to 18. The eccentric amount of the i-th surface in the zoom state j is Δy (i, j), and the radius of rotation of the reflected image formed by the reflected light from the i-th surface of the image sensor 9 is r (i, j). Here, only the eccentricity in the Y direction will be described. Instead of rotating the test optical system 6, the difference between the position coordinate of the reflected image on the image sensor 9 and the center coordinate of the image on the image plane chart 7 may be used instead of the radius gyration of the reflected image.

  The eccentricity amount measurement process of the following steps is executed by the computer 12 according to a computer program.

  In step 2, the computer 12 causes the rotation radius of the reflected image of each surface to be inspected on the image sensor 9 in each of the zoom states 1 to 3 (the radius of the trajectory of the reflected image when the optical system 6 to be inspected is rotated). ) Is measured. This step 2 corresponds to the first step and the second step. Further, the turning radii of the reflected images obtained in the zoom states 1 to 3 correspond to the first data and the second data regarding the eccentricity of the surface to be inspected obtained in each of the plurality of zoom states.

  In the description here, it is assumed that all of the radius gyrations r (1 to 6, 1 to 3) of the reflected images of the first surface to the sixth surface of the first lens unit can be measured in each of the zoom states 1 to 3. To do. Regarding the second lens unit, in the zoom state 1, it is possible to measure only the radii of rotation r (7 to 9, 1) of the reflected images of the seventh surface to the ninth surface, and in the zoom state 2, the ninth surface to the eleventh surface. It is assumed that only the radius of gyration r (9 to 11, 2) of the reflection image of can be measured. Furthermore, in zoom state 3, it is assumed that only the radii of rotation r (11 to 12,3) of the reflected images of the 11th and 12th surfaces can be measured. The rotation radius r of the reflected image can be measured for each zoom state is different because the distance between the lens units changes depending on the zoom, and the above-mentioned five factors change to measure the rotation radius r of the reflected image. This is because the test surface that can be measured and the test surface that cannot be measured change.

  The following step 3 and subsequent steps correspond to the third step. In step 3, the computer 12 sets p of the p-th lens unit to 1.

  In step 4, the computer 12 determines that the tilt error of the second lens unit caused by the zoom is small, and the relative parallel eccentricity Δv (2,2) of the second lens unit in the zoom states 2 and 3 with respect to the zoom state 1 is small. Calculate Δv (2,3).

  Next, in step 5, the computer 12 uses the relative parallel eccentricity amount of the lens unit described above to calculate the eccentricity amount of each test surface in the lens unit. Steps 4 and 5 are repeated through step 7 until p reaches G in step 6. In step 7, the computer 12 increments p by 1 and returns to step 4.

  With respect to the first lens unit, since the reflected images of all the surfaces to be inspected can be measured in each zoom state, the inside of the first lens unit in each of zoom states 1 to 3 is calculated without calculating the relative parallel decentering amount. The eccentricity amount Δy (1 to 6, 1 to 3) of the surface to be inspected is calculated from the radius gyration r (1 to 6, 1 to 3) of the reflection image measured in step 2.

  In the zoom state 1, since the turning radii Δr (7 to 9) of the reflected images on the 7th to 9th surfaces can be measured, the respective eccentricity amounts Δy (7 to 9, 1) can be calculated. In the calculation of the eccentricity amount Δy of the seventh to ninth surfaces, paraxial ray tracing calculation is performed using the calculated eccentricity amount Δy (1 to 6,1) of the first to sixth surfaces.

  Next, the computer 12 causes the relative parallel decentering amount Δv (2,2) of the second lens unit in which the radius of gyration of the reflected image of the ninth surface on the image sensor 9 in the zoom state 2 is r (9,2). To calculate. Here, the eccentricity amounts Δy (1 to 6, 2) of the first to sixth surfaces in the zoom state 2, the eccentricity amounts Δy (7 to 9,1) of the seventh to ninth surfaces in the zoom state 1, and the optical test object. Using the radius of curvature R (1 to 9), the surface spacing d (1 to 8, 2), and the refractive index n (1 to 8) as the design values of the system 6, paraxial ray tracing calculation is performed. The eccentricity amount Δy (7 to 9,2) of the seventh to ninth surfaces in the zoom state 2 is the eccentricity amount Δy (7 to 9,1) of the seventh to ninth surfaces in the zoom state 1 and the second lens in the zoom state 2. Using the relative parallel eccentricity amount Δv (2,2) of the unit, the calculation can be performed by the equation (1).

Next, the computer 12 measures the radii of gyration r (10,2), r (11,2) of the reflected images of the tenth surface and the eleventh surface in the zoom state 2 and the first to the ninth in the zoom state 2. Surface eccentricity Δy (1 to 9, 2), radius of curvature R (1 to 11) as a design value of the optical system 6 to be tested, surface spacing d (1 to 10, 2), refractive index n (1 to 1) From 10), the eccentricity amounts Δy (10,2) and Δy (11,2) of the 10th and 11th surfaces are calculated.

  Next, the computer 12 causes the relative parallel decentering amount Δv (2,3) of the second lens unit in which the radius of gyration of the reflected image of the eleventh surface on the image sensor 9 in the zoom state 3 is r (11,3). To calculate. Here, the eccentricity amounts Δy (7 to 11,2) of the 7th to 11th surfaces in the zoom state 2, the eccentricity amounts Δy (1 to 6, 3) of the 1st to 6th surfaces in the zoom state 3, and the optical test object. Using the radius of curvature R (1 to 11), the surface distance d (1 to 10, 3), and the refractive index n (1 to 10) as the design values of the system 6, paraxial ray tracing calculation is performed. The eccentricity amount Δy (7 to 11,3) of the seventh to eleventh surfaces in the zoom state 3 is equal to the eccentricity amount Δy (7 to 11,2) of the seventh to eleventh surfaces in the zoom state 2 and the second amount in the zoom state 2. The relative parallel eccentricity amount Δv (2,2) of the lens unit and the relative parallel eccentricity amount Δv (2,3) of the second lens unit in the zoom state 3 can be used to perform the calculation by Expression (2).

Further, the computer 12 determines that the eccentricity Δy (12,3) of the twelfth surface in the zoom state 3 is the measured rotation radius r (12,3) of the reflected image of the twelfth surface in the zoom state 3 and the zoom state 3 Eccentricity amount Δy (1 to 11, 3) of the 1st to 11th surfaces, radius of curvature R (1 to 12) as a design value of the optical system 6 to be measured, surface distance d (1 to 11, 3), and refraction Calculation is performed using the rate n (1 to 11). With this, the measurement is performed on all the surfaces in the second lens unit in the zoom state 3.

  Further, the computer 12 calculates the eccentricity amount Δy (12,2) of the twelfth surface in the zoom state 2 and the eccentricity amount Δy (12,3) of the twelfth surface measured and calculated in the zoom state 3 and the zoom state 2 in the zoom state 2. The relative parallel eccentricity amount Δv (2,2) of the second lens unit and the relative parallel eccentricity amount Δv (2,3) of the second lens unit in the zoom state 3 are used to calculate by Expression (3).

  With this, the measurement is performed on all the surfaces to be inspected in the second lens unit in the zoom state 2.

  Further, the computer 12 zooms the eccentricity amount Δy (10 to 12,1) of the 10th to 12th surfaces in the zoom state 1 and the eccentricity amount Δy (10 to 12,2) of the 10th to 12th surfaces in the zoom state 2. Using the relative parallel eccentricity amount Δv (2,2) of the second lens unit in the state 2 and the eccentricity amount Δy (10-12,3) of the 10th to 12th surfaces in the zoom state 3 and The relative parallel eccentricity amount Δv (2,3) of the second lens unit in the zoom state 3 is used to calculate by the equation (5).

  Here, i is an integer of 10-12. With this, the measurement is performed on all the surfaces to be inspected in the second lens unit in the zoom state 1.

  By the above method, the eccentricity amounts of all the test surfaces in the second lens unit in all zoom states are measured. Also for the third lens unit, the eccentricity amount of all the test surfaces in all zoom states is calculated by the same method as the method of calculating the eccentricity amount of each test surface of the second lens unit.

  As described above, in the first embodiment, the eccentricity amount Δy of the surface to be inspected having a small surface number is sequentially calculated for each zoom state from the rotation radius r of the reflected image. When the eccentricity amount Δy of the surface to be inspected having the same surface number is obtained in different zoom states, the relative eccentricity amount Δv of the lens unit including the surface to be inspected can be calculated. Therefore, even if the surface to be measured is not measured or is difficult to measure, if it is measured in different zoom states, the eccentricity of the surface to be measured is calculated using the relative eccentricity amount Δv of the lens unit including the surface to be measured. The amount can be calculated.

  Therefore, according to the present embodiment, even if there is a test surface for which eccentricity measurement is not possible in each zoom state, it is possible to obtain the eccentricity amount of all test surfaces in all zoom states. Moreover, since the number of test surfaces to be measured is small, the measurement time can be shortened.

  When the number of test surfaces in the lens unit is N and the number of zoom states (3 in this embodiment) is M, the eccentricity of all test surfaces in all lens units in all zoom states is calculated. At least (N + M-1) measurements are required to obtain.

  Further, in the present embodiment, as an example, the case where the tilt eccentricity of the lens unit due to the zoom is small has been described. However, assuming that the parallel eccentricity of the lens unit is small, the tilt eccentricity of the lens unit is calculated and each of the surfaces to be inspected is calculated. The amount of eccentricity can also be calculated. If the center coordinates of the tilt of the lens unit are the vertex coordinates of the surface to be inspected having the smallest surface number in the lens unit, for example, equation (1) may be changed to equation (6). In Expression (6), Δθ (2, 2) is the tilt eccentric amount of the second lens unit with respect to the zoom state 1 in the zoom state 2, and d (k, 2) is the k-th surface and the k + th surface in the zoom state 2. It is the surface spacing between one surface.

Here, i is an integer of 7-9. Other formulas (2) to (5) may be similarly changed.

  In the first embodiment, the parallel eccentricity amount or the tilt eccentricity amount of the lens unit is calculated, but in the second embodiment, the radii of rotation of the reflected images of at least two test surfaces in the lens unit are measured, and the parallel eccentricity amount of the lens unit is measured. And the tilt eccentricity amount are both calculated to calculate (measure) the eccentricity amount of the test surface with higher accuracy.

  The configuration of the eccentricity measuring device and the optical system 6 to be tested are the same as in the first embodiment. Here, it is assumed that the eccentricity amounts Δy (1 to 18, 1) of all the surfaces to be measured can be measured in the zoom state 1 (a part of the plurality of zoom states). It is also assumed that in the zoom state 2, the radii of rotation r (2,2), r (5,2) of the reflected images of the second surface and the fifth surface on the image sensor 9 can be measured. Then, in the zoom state 2, the relative parallel eccentric amount of the first lens unit with respect to the zoom state 1 is Δv (1,2), and the tilt eccentric amount is θ (1,2).

  The computer 12 measures the eccentricity amounts Δy (1,1) to Δy (5,1) of the first to fifth surfaces measured in the zoom state 1 and the radius of curvature R (i = 1) as the design value of the optical system 6 to be tested. ˜5), the surface spacing d (1 to 4, 2) and the refractive index n (1 to 4) are used to perform paraxial approximation ray tracing calculations. Then, the computer 12 causes the first lens unit in the zoom state 2 in which the turning radii of the reflected images of the second surface and the fifth surface on the image sensor 9 are r (2,2) and r (5,2), respectively. The parallel eccentricity amount Δv (1,2) and the tilt eccentricity amount θ (1,2) are calculated. At this time, the rotation center of the tilt of the first lens unit is the vertex coordinates of the first surface. The computer 12 calculates the eccentricity amount Δy (1 to 6, 2) of each surface to be inspected of the first lens unit in the zoom state 2 and the eccentricity amount Δy (1 to 6, 1) of each surface to be inspected in the zoom state 1. It is calculated by the equation (7) using the parallel eccentricity amount Δv (1,2), the tilt eccentricity amount Δθ (1,2) and the surface distance d (1-5,2) of the first lens unit in the zoom state 2. be able to.

  Here, i is an integer of 1 to 6. By the above method, the eccentricity amounts Δy (1 to 6, 2) of all the test surfaces of the first lens unit in the zoom state 2 are calculated as the turning radii of the reflection images of the two test surfaces in the first lens unit. You can get it just by measuring. Similarly, regarding the second lens unit and the third lens unit in the zoom state 2, the turning radii of the reflection images of the two test surfaces out of the 7th to 12th surfaces and the 8th to 18th surfaces in the zoom state 2 are calculated. The eccentric amount Δy (7 to 18, 2) of the 7th to 12th surfaces and the 8th to 18th surfaces can be obtained only by measuring.

  Conventionally, it was necessary to perform 18 times of eccentricity measurement in the zoom state 2, but the method of the present embodiment may perform 6 times of eccentricity measurement. Therefore, the measurement time can be shortened to 1/3. Further, even if parallel eccentricity or tilt eccentricity occurs in the lens unit during zooming, the eccentricity of the surface to be inspected in the lens unit can be measured with high accuracy.

  When the number of test surfaces in the lens unit is N and the number of zoom states (3 in this embodiment) is M, the eccentricity of all test surfaces in all lens units in all zoom states is calculated. At least (N + 2M-2) measurements are required to obtain.

  The method of this embodiment can be applied to the first embodiment. For example, if the turning radii of the reflected images of the 7th to 10th surfaces in the zoom state 1, the 9th to 11th surfaces in the zoom state 2, and the 10th to 12th surfaces in the zoom state 3 are measured, the second rotations in the zoom states 2 and 3 are measured. The relative parallel decentering amount v (2, 2 to 3) and the tilt decentering amount θ (2 to 2) of the lens unit can be calculated. Therefore, it is possible to obtain the eccentricity amount of all the test surfaces in the second lens unit in each zoom state by the same calculation as the above-described calculation.

  The test surface to be measured does not have to be continuous, and there may be a test surface not to be measured between the test surfaces to be measured. For example, in the zoom state 1, the radii of rotation of the reflected images on the 9th, 11th, and 12th surfaces are measured, in the zoom state 2, the radii of rotation of the reflected images on the 7th to 9th, 12th surfaces are measured, and in the zoom state 3, the 8th surface is measured. By measuring the radii of gyrations of the reflected images on the 10th, 10th, and 11th surfaces, the eccentricity of all the surfaces to be detected in the second lens unit in each zoom state can be obtained.

  In the first and second embodiments, the method of calculating the eccentricity amount of the surface to be inspected using the measurement data caused by the surface eccentricity in different zoom states has been described. On the other hand, in the third embodiment, a method of calculating the amount of eccentricity after the optical system to be tested is assembled by using the eccentricity measurement data obtained by a single lens unit will be described.

  The configuration of the eccentricity measuring device and the optical system 6 to be tested are the same as in the first embodiment. The eccentricity amount measuring method of this embodiment will be specifically described with reference to FIG. In step 11 (first step), each lens unit is individually installed in the eccentricity amount estimation device (first state). Then, the computer 12 measures the radius of gyration (first data) of the reflected image on the image sensor 9 of each surface to be inspected of the individually installed lens unit, and uses the radius of gyration to calculate the eccentricity Δys (i). ) Is calculated. i is an integer of 1-18. In this embodiment, the number of lenses for which the eccentricity measurement is performed at one time is small, so that the eccentricity measurement is easy.

  Next, in step 12, the lens units are arranged according to the design values and the optical system 6 to be tested is assembled.

  Next, in step 13, the assembled optical system 6 to be inspected is installed in the decentering amount measuring device (second state), and the radii of gyration of the reflected images of at least two inspected surfaces in each lens unit are measured. Here, the radii of rotation r (2), r (6), r (8), r (12), r (of the reflected image on the image sensor 9 of the second, sixth, eighth, twelve, thirteenth and sixteenth surfaces. 13) and r (16) shall be measured.

  Next, at step 14, the computer 12 calculates the amount of eccentricity of the lens unit. First, the parallel eccentricity amount of the j-th (= 1 to 3) lens unit with respect to the optical axis of the eccentricity amount measuring device is Δv (j), and the tilt eccentricity amount is Δθ (j). The computer 12 uses the lens unit alone to measure the eccentricity Δys (1 to 6) of each surface to be measured, the radius of curvature R (1 to 6) as a design value of the optical system 6 to be measured, and the surface distance d (1 to 1). 5) and the refractive index n (1 to 5) are used to perform paraxial approximation ray tracing calculations. At this time, the computer 12 causes the parallel eccentricity amount Δv (1 of the first lens unit in which the turning radii of the reflected images on the image sensor 9 of the second surface and the sixth surface are r (2) and r (6), respectively. ) And the tilt eccentricity amount Δθ (1) are calculated.

  Next, in step 15, the computer 12 calculates the eccentricity amount Δy (i) of the i-th surface (i = 1 to 6) in the lens unit by the following formula (8).

Here, i is an integer of 1 to 6. The computer 12 also calculates the eccentricity amount of each test surface of the second lens unit in the same manner as in step 14 and step 15. That is, the computer 12 measures the eccentricity amount Δys (1 to 12) of each measured surface, the radius of curvature R (1 to 12) as a design value, the surface distance d (1 to 11), and the refractive index n (1. ~ 11) is used to perform paraxial approximation ray tracing calculations. At this time, the computer 12 causes the parallel eccentricity amount Δv (2 of the second lens unit in which the turning radii of the reflected images of the eighth surface and the twelfth surface on the image sensor 9 are r (8) and r (12), respectively. ) And the tilt eccentricity amount Δθ (2) are calculated. The decentering amount Δy (i) of the i-th surface (i = 7 to 12) in the second lens unit can be calculated by the following equation (9).

  Here, i is an integer of 7-12. The computer 12 also calculates the eccentricity amount of each surface to be inspected of the third lens unit in the same manner as in step 14 and step 15. That is, the computer 12 measures the eccentricity Δys (1 to 16) of each measured surface, the radius of curvature R (1 to 16) as a design value, the surface spacing d (1 to 15), and the refractive index n (1. 15) is used to perform paraxial approximation ray tracing calculations. At this time, the computer 12 causes the parallel eccentricity amount Δv (3 of the third lens unit in which the radii of rotation of the reflected images on the image sensor 9 of the 13th and 16th surfaces are r (13) and r (16), respectively. ) And the tilt eccentricity amount Δθ (3) are calculated. The decentering amount Δy (i) of the i-th surface (i = 13 to 18) in the third lens unit can be calculated by the following formula (10).

  Here, i is an integer of 13-18. By the above method, the eccentricity measurement data obtained by the lens unit alone is used to calculate the eccentricity amount after the optical system 6 to be tested is assembled. It should be noted that only the lens unit having a high eccentricity sensitivity is selected in the optical system 6 to be measured, the eccentricity measurement is performed by the lens unit alone, and the eccentricity measurement is performed after the optical system 6 is assembled. Of these, at least two test surfaces may be measured for eccentricity to obtain the eccentricity amount of each test surface in the lens unit.

  According to this embodiment, since the eccentricity measurement is performed by each lens unit alone, highly accurate eccentricity measurement can be easily performed.

  In Examples 1 to 3, the test optical system 6 was rotated, and the eccentricity of the test surface was calculated from the radius of gyration of the reflected image of the test surface on the image sensor 9. On the other hand, in Example 4, the test optical system 6 is fixed without being rotated, the objective optical system 5 is driven in a plane orthogonal to the optical axis, and the eccentricity of the test surface is determined from the driving amount. The method of calculating is explained.

  FIG. 4 shows the configuration of the eccentricity measuring device according to the fourth embodiment. The eccentricity measuring apparatus of the present embodiment is provided with a YZ stage 13 for driving the objective optical system 5 in a plane (YZ plane) orthogonal to the optical axis, and a drive for rotating the test optical system 6. It is different from the eccentricity measuring device of the first embodiment (FIG. 1) in that there is no mechanism.

  The eccentricity amount measuring method in this embodiment is as follows. In this embodiment, the objective optical system 5 is driven in the X direction so that the light is focused on the apparent spherical center position of the surface 6a to be tested. At this time, the image of the index chart 2 (reflection image) formed by the light reflected by the surface 6 a to be inspected is captured by the image sensor 9. When the surface 6a to be inspected is eccentric, the coordinates of the reflected image deviate from the center of the image on the image plane chart 7.

Therefore, the objective optical system 5 is driven in the YZ plane using the YZ stage 13 so that the center of the image of the index chart 2 coincides with the center of the image of the image plane chart 7. The driving amount at that time corresponds to the radius of gyration of the reflected image on the image sensor 9 described in the first to third embodiments. Therefore, the computer 12 measures the drive amount of the objective optical system 5 on each surface to be inspected, and calculates the eccentricity amount of each surface to be inspected by the method described in Examples 1 to 3. By driving the objective optical system 5 in the YZ plane orthogonal to the optical axis, it is possible to measure the amount of eccentricity of the test surface even if the reflected image deviates from the field of view of the image sensor 9.
(Other embodiments)
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program. It can also be realized by the processing. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

  The embodiments described above are merely representative examples, and various modifications and changes can be made to the embodiments when implementing the present invention.

1 Light Source 2 Index Chart 5 Objective Optical System 6 Test Optical System 6a Test Surface 7 Imaging Surface Chart 9 Image Sensor 11 Rotary Stage 12 Computer

Claims (11)

A method for measuring an eccentricity amount in an optical system to be tested, which is composed of a plurality of lens units each including one or more lenses,
A first step of obtaining, in the first state of the test optical system, first data regarding decentering of a test surface in the test optical system by measurement using light from the objective optical system;
In the second state in which the distance between the lens units is different from the first state of the test optical system, the second state regarding the eccentricity of the test surface is measured by the measurement using the light from the objective optical system. The second step of obtaining the measurement data,
And a third step of acquiring the amount of eccentricity of the surface to be inspected using the first and second data. In the second step, acquiring the second data in each of the plurality of second states with different intervals,
The eccentricity amount measuring method according to claim 1, wherein, in the third step, the eccentricity amount is acquired using the second data acquired in each of the plurality of second states.   In the third step, the eccentricity amount is acquired by using the second data acquired in a part of the second states of the plurality of second states with different intervals in the second step. The method for measuring the amount of eccentricity according to claim 2, wherein   When N is the number of surfaces to be inspected in the lens unit and M is the number of the plurality of second states, at least (N + 2M-2) pieces of the second data are used in the second step. , M of the eccentricity amounts in the second state are acquired, and the eccentricity amount measuring method according to claim 3. In the first step and the second step, the first data and the second data for at least two test surfaces are obtained for each lens unit,
The eccentricity amount measuring method according to claim 3 or 4, wherein in the third step, the parallel eccentricity and the tilt eccentricity of the lens unit are acquired. A method for measuring an eccentricity amount in an optical system to be tested, which is composed of a plurality of lens units each including one or more lenses,
In a first state in which each of the plurality of lens units is a single lens unit, the first data regarding the eccentricity of the test surface in the single lens unit is obtained by measurement using light from the objective optical system. The first step to get,
A second step of obtaining the decentering amount of the surface to be inspected using the first data in a second state where the optical system to be inspected is constituted by the plurality of lens units. Eccentricity measurement method.   7. The eccentricity measuring device according to claim 6, wherein in the first step, the data regarding at least two of the surfaces to be inspected are acquired for each of the lens units.   The first and second data are the position coordinates of an image on the light receiving sensor of the light reflected by the surface to be measured, which is measured by the autocollimation method using the light from the objective optical system, or the optical system to be tested. 8. The eccentricity amount measuring method according to claim 1, wherein a radius of an image locus of the light reflected by the surface to be inspected at the light receiving sensor when is rotated.   The first and second data are driven according to the position coordinates of the image on the light receiving sensor of the light reflected by the surface to be measured, which is measured by the autocollimation method using the light from the objective optical system. The eccentricity amount measuring method according to any one of claims 1 to 7, which is a driving amount of the objective optical system.   An eccentricity measuring device, wherein the eccentricity is measured by using the eccentricity measuring method according to any one of claims 1 to 9.   The eccentricity measuring method according to any one of claims 1 to 9, wherein a computer of an eccentricity measuring device that measures an eccentricity in a test optical system configured by a plurality of lens units each including one or more lenses. A computer program characterized by causing it to perform processing according to.