WO2021014567A1 - Mirror surface shape measurement device, mirror surface shape measurement method, and reflection mirror system - Google Patents

Abstract

A mirror surface shape measurement device (2) comprises: a microlens array (11) comprising a plurality of microlenses (11a) for concentrating light (3) reflected by a mirror (1) under inspection in which a plurality of divided mirrors (1-1)-(1-6) are combined; an image transfer optical system (12) for diffracting a plurality of wavelength components included in the light (3) concentrated by the plurality of microlenses (11a) such that wavelength components with longer wavelengths are diffracted more greatly and forming each diffracted wavelength component into a spot image; an imaging element (17) for imaging the spot images formed by the image transfer optical system (12); and a level difference calculation unit (23) for calculating the level difference between two adjacent divided mirrors from among the plurality of divided mirrors (1-1)-(1-6) on the basis of the spot images from among the plurality of spot images imaged by the imaging element (17) that correspond to the light (3) reflected by the two divided mirrors.

Description

Mirror surface shape measuring device, mirror surface shape measuring method and reflector system

The present invention relates to a mirror surface shape measuring device for calculating a step between a plurality of split mirrors, a mirror surface shape measuring method, and a reflector system.

Among the large-diameter reflectors used for telescopes, there is a reflector in which a plurality of split mirrors are combined. A reflector in which a plurality of split mirrors are combined may have a step between the plurality of split mirrors.
In the following Non-Patent Document 1, two grism arrays that disperse the light reflected by the reflector are used, and the relative piston, which is a step between a plurality of split mirrors of the reflector, is used as an interference fringe. The method of measurement is disclosed. The two grism arrays are dispersion elements having different diffraction directions.
In the method disclosed in Non-Patent Document 1, when measuring the relative piston, the drive mechanism rotates the filter wheel and uses the grism array for the spectroscopy of the light reflected by the reflector among the two grism arrays. I am trying to switch.

In order to measure the step between the plurality of split mirrors of the reflector by the method disclosed in Non-Patent Document 1, it is necessary to provide a drive mechanism for rotating the filter wheel. Since the drive mechanism is not maintenance-free, regular maintenance is required. However, when the reflector is used in outer space, it is difficult to easily maintain the drive mechanism.
Therefore, when measuring the step between a plurality of split mirrors of a reflector used in outer space by the method disclosed in Non-Patent Document 1, there is a risk of failure of the drive mechanism. There was a problem.

The present invention has been made to solve the above-mentioned problems, and it is possible to calculate the step between a plurality of split mirrors possessed by the test mirror without using a drive mechanism that requires maintenance. It is an object of the present invention to obtain a mirror surface shape measuring device, a mirror surface shape measuring method, and a reflector system that can be used.

The mirror surface shape measuring device according to the present invention has a microlens array having a plurality of microlenses for condensing light reflected by a test mirror in which a plurality of dividing mirrors are combined, and a plurality of microlenses for condensing the light. Of the plurality of wavelength components contained in the light, the longer the wavelength component is, the larger the diffraction is performed, and each of the diffracted wavelength components is imaged as a spot image. Of the imaging element that captures each of the imaged spot images and the plurality of spot images imaged by the imaging element, the light is reflected by each of the two dividing mirrors that are adjacent to each other in the plurality of dividing mirrors. It is provided with a step calculation unit for calculating a step between two dividing mirrors based on a spot image corresponding to the light.

According to the present invention, it is possible to calculate the step between a plurality of split mirrors possessed by the test mirror without using a drive mechanism that requires maintenance.

It is a block diagram which shows the reflector system including the mirror surface shape measuring apparatus 2 which concerns on Embodiment 1. FIG. It is a hardware block diagram which shows the hardware of the data processing unit 20. FIG. 5 is a hardware configuration diagram of a computer when the data processing unit 20 is realized by software, firmware, or the like. It is a flowchart which shows the processing procedure of the data processing unit 20. It is explanatory drawing which shows the image of light 3 by a microlens array 11 and the arrangement of a plurality of microlenses 11a which a microlens array 11 has. FIG. 6A is an explanatory view showing a spot image 60 in which the light 3 focused by the microlens 11an is diffracted by the Fresnel zone plate 13 and then imaged on the image pickup element 17 by the lens 14, FIG. 6B. In the explanatory view showing the spot image 70 imaged on the image pickup element 17 by the lens 14 after the light 3 focused by the microlenses 11a- (1) (2) and the like is diffracted by the Frenel zone plate 13. is there. It is a block diagram which shows the reflector system including the mirror surface shape measuring apparatus 2 which concerns on Embodiment 2. FIG. It is explanatory drawing which shows the image of light 3 by a microlens array 11 and the arrangement of a plurality of microlenses 11a which a microlens array 11 has. The image of the light 3 by the microlens array 11, the arrangement of the plurality of microlenses 11a included in the microlens array 11, the arrangement of the first cylindrical lens array 81, and the arrangement of the second cylindrical lens array 82. It is explanatory drawing which shows.

Hereinafter, in order to explain the present invention in more detail, a mode for carrying out the present invention will be described with reference to the accompanying drawings.

Embodiment 1.
FIG. 1 is a configuration diagram showing a reflector system including the mirror surface shape measuring device 2 according to the first embodiment.
In FIG. 1, the test mirror 1 is, for example, a reflector used in outer space. However, the test mirror 1 is not limited to the reflector used in outer space, and may be a reflector used on the earth.
The test mirror 1 is a combination of a plurality of split mirrors 1-1 to 1-6.
Each of the split mirrors 1-1 to 1-6 is a partial mirror that constitutes a part of the test mirror 1.
In the reflector system shown in FIG. 1, the test mirror 1 includes six split mirrors 1-1 to 1-6, but it is sufficient if two or more split mirrors are provided, and five or less split mirrors are used. It may be provided with a mirror or seven or more split mirrors.

The mirror surface shape measuring device 2 is a device that calculates a step or the like between a plurality of split mirrors 1-1 to 1-6 possessed by the test mirror 1. If the step between the plurality of split mirrors 1-1 to 1-6 is calculated by the mirror surface shape measuring device 2, the control unit (not shown) can remove the step, for example, the split mirror 1-1. It is possible to correct the positions of ~ 1-6.
The light 3 is light that is incident on the test mirror 1 from the outside of the mirror surface shape measuring device 2 shown in FIG. 1 and is reflected by the test mirror 1.
The microlens array 11, the Fresnel zone plate 13, the lens 14, and the image sensor 17 are optical systems to be tested in the mirror surface shape measuring device 2.
Each of the test mirror 1, the microlens array 11, the Frenel zone plate 13, the lens 14, and the image pickup element 17 is in a direction parallel to the x-axis in a Cartesian coordinate system in three-dimensional space (hereinafter referred to as "x-direction"). And the plane including the direction parallel to the y-axis (hereinafter referred to as "y-direction") (hereinafter referred to as "xy-plane").
Further, each of the test mirror 1, the microlens array 11, the Fresnel zone plate 13, the lens 14, and the image sensor 17 are arranged in a direction parallel to the z-axis (hereinafter, referred to as "z-direction").
In the reflector system shown in FIG. 1, an optical system may be installed between the mirror 1 to be inspected and the mirror surface shape measuring device 2. Further, inside the mirror surface shape measuring device 2, the optical system may be installed closer to the mirror 1 to be examined than the microlens array 11.

The microlens array 11 is arranged on the pupil surface of the optical system to be examined, and has a plurality of microlenses 11a for condensing the light 3 reflected by the mirror 1 to be examined.
The microlens 11a is an optical element that collects the light 3 reflected by the test mirror 1, and the plurality of microlenses 11a are arranged at equal intervals.
In the mirror surface shape measuring device 2 shown in FIG. 1, the microlens array 11 has 23 microlenses 11a. However, the microlens array 11 is adjacent to each other in the microlens 11a that collects the light 3 reflected by the split mirrors 1-1 to 1-6 and the split mirrors 1-1 to 1-6. It suffices to have a microlens 11a for condensing the light 3 reflected by each of the two split mirrors. Therefore, the number of microlenses 11a included in the microlens array 11 is not limited to the 23 microlenses 11a.

The image change optical system 12 includes a Fresnel zone plate 13 and a lens 14.
The image transfer optical system 12 diffracts the longer wavelength component of the plurality of wavelength components contained in the light 3 condensed by the plurality of microlenses 11a, and diffracts each wavelength component. An image is formed on the image pickup element 17 as a spot image.
The Frenel zone plate 13 is an optical element having chromatic aberration, and among a plurality of wavelength components contained in the light 3 focused by the plurality of microlenses 11a, the longer the wavelength component, the larger the diffraction.
The wavelength component 15 is one of a plurality of wavelength components contained in the light 3 focused by the plurality of microlenses 11a, and is a component having a longer wavelength than the short wavelength component 16.
The wavelength component 16 is one of a plurality of wavelength components contained in the light 3 focused by the plurality of microlenses 11a, and is a component having a shorter wavelength than the short wavelength component 15.
In FIG. 1, two wavelength components 15 and 16 are shown as examples of a plurality of wavelength components contained in the light 3 focused by the plurality of microlenses 11a, respectively. However, this is only an example, and there may be three or more wavelength components contained in the light 3 condensed by the plurality of microlenses 11a.
The lens 14 causes the image pickup device 17 to image each of the plurality of wavelength components diffracted by the Fresnel zone plate 13 as a spot image.

The image sensor 17 captures each spot image formed by the lens 14 of the image transfer optical system 12.
The image sensor 17 outputs spot data to the data extraction unit 21 of the data processing unit 20, which will be described later, as data indicating the imaging results of each spot image.

The data processing unit 20 includes a data extraction unit 21, a split mirror wave surface calculation unit 22, a step calculation unit 23, and a mirror wave surface calculation unit 24 to be inspected.
FIG. 2 is a hardware configuration diagram showing the hardware of the data processing unit 20.

The data extraction unit 21 is realized by, for example, the data extraction circuit 31 shown in FIG.
The data extraction unit 21 is a spot image corresponding to the light 3 reflected by the split mirror 1-n (n = 1,2,3,4,5,6) among the spot data output from the image sensor 17. Spot data indicating the imaging result (hereinafter, referred to as “spot data in the split mirror DD _n ”) is output to the split mirror wave surface calculation unit 22.
For example, the spot data DD ₁ in the split mirror shows the imaging result of the spot image corresponding to the light 3 reflected by the split mirror 1-1, and the spot data DD ₂ in the split mirror is reflected by the split mirror 1-2. The imaging result of the spot image corresponding to the light 3 is shown. Further, the spot data DD ₆ in the split mirror shows the imaging result of the spot image corresponding to the light 3 reflected by the split mirror 1-6.

The data extraction unit 21 corresponds to the light 3 reflected by each of the two dividing mirrors adjacent to each other in the dividing mirrors 1-1 to 1-6 among the spot data output from the image sensor 17. Spot data (hereinafter, referred to as “boundary spot data BD _n ”) indicating the imaging result of the spot image to be imaged is output to the step calculation unit 23.
The dividing mirror 1-1 and the dividing mirror 1-2 are adjacent to each other, and the dividing mirror 1-2 and the dividing mirror 1-3 are adjacent to each other.
Further, the dividing mirrors 1-3 and the dividing mirrors 1-4 are adjacent to each other, and the dividing mirrors 1-4 and the dividing mirrors 1-5 are adjacent to each other.
Further, the dividing mirror 1-5 and the dividing mirror 1-6 are adjacent to each other, and the dividing mirror 1-6 and the dividing mirror 1-1 are adjacent to each other.
For example, the boundary spot data BD ₁ shows the imaging result of the spot image corresponding to the light 3 reflected by the dividing mirror 1-1 and the dividing mirror 1-2, and the boundary spot data BD ₂ is the dividing mirror 1-. The imaging result of the spot image corresponding to the light 3 reflected by each of 2 and the split mirror 1-3 is shown. Further, the boundary spot data BD ₆ shows the imaging result of the spot image corresponding to the light 3 reflected by each of the split mirror 1-6 and the split mirror 1-1.

For example, in the internal memory of the data extraction unit 21, coordinate information indicating at which coordinate of the image sensor 17 the spot image corresponding to the light 3 reflected by the split mirror 1-n is formed is stored. ing.
Further, in the internal memory of the data extraction unit 21, a spot image corresponding to the light 3 reflected by each of the two dividing mirrors adjacent to each other is imaged at the coordinates of the image sensor 17. The indicated coordinate information is stored.
The data extraction unit 21 identifies each of the spot data DD _n in the split mirror and the boundary spot data BD _n included in the spot data output from the image sensor 17 based on the coordinate information stored in the internal memory. To do.

The divided mirror wave surface calculation unit 22 is realized by, for example, the divided mirror wave surface calculation circuit 32 shown in FIG.
The split mirror wave surface calculation unit 22 uses the split mirror based on the spot image corresponding to the light 3 reflected by each of the split mirrors 1-1 to 1-6 among the plurality of spot images captured by the image sensor 17. Calculate each wave surface of 1-1 to 1-6.
That is, the split mirror wave surface calculation unit 22 calculates the wave plane of the split mirror 1-n based on the imaging result of the spot image indicated by the spot data DD _n in the split mirror output from the data extraction unit 21.

The step calculation unit 23 is realized by, for example, the step calculation circuit 33 shown in FIG.
The step calculation unit 23 is the light 3 reflected by each of the two split mirrors adjacent to each other in the split mirrors 1-1 to 1-6 among the plurality of spot images captured by the image pickup element 17. The step between the two split mirrors is calculated based on the spot image corresponding to.
That is, the step calculation unit 23 calculates the step between the two split mirrors based on the imaging result of the spot image indicated by the boundary spot data BD _n output from the data extraction unit 21.

The test mirror wave surface calculation unit 24 is realized by, for example, the test mirror wave surface calculation circuit 34 shown in FIG.
The wave surface calculation unit 24 of the test mirror 1 is based on the step calculated by the step calculation unit 23 and the wave surfaces of the split mirrors 1-1 to 1-6 calculated by the split mirror wave surface calculation unit 22. Is calculated.

In FIG. 1, each of the data extraction unit 21, the split mirror wave surface calculation unit 22, the step calculation unit 23, and the test mirror wave surface calculation unit 24, which are the components of the data processing unit 20, is dedicated hardware as shown in FIG. It is supposed to be realized by ware. That is, it is assumed that the data processing unit 20 is realized by the data extraction circuit 31, the split mirror wave surface calculation circuit 32, the step calculation circuit 33, and the mirror wave surface calculation circuit 34 to be inspected.
Here, each of the data extraction circuit 31, the divided mirror wave surface calculation circuit 32, the step calculation circuit 33, and the test mirror wave surface calculation circuit 34 is, for example, a single circuit, a composite circuit, a programmed processor, or a parallel programmed processor. , ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), or a combination thereof.

The components of the data processing unit 20 are not limited to those realized by dedicated hardware, and even if the data processing unit 20 is realized by software, firmware, or a combination of software and firmware. Good.
The software or firmware is stored as a program in the memory of the computer. A computer means hardware that executes a program, and corresponds to, for example, a CPU (Central Processing Unit), a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a processor, or a DSP (Digital Signal Processor). To do.

FIG. 3 is a hardware configuration diagram of a computer when the data processing unit 20 is realized by software, firmware, or the like.
When the data processing unit 20 is realized by software, firmware, or the like, a program for causing a computer to execute the processing procedures of the data extraction unit 21, the split mirror wave surface calculation unit 22, the step calculation unit 23, and the mirror wave surface calculation unit 24. Is stored in the memory 41. Then, the processor 42 of the computer executes the program stored in the memory 41.
Further, FIG. 2 shows an example in which each of the components of the data processing unit 20 is realized by dedicated hardware, and FIG. 3 shows an example in which the data processing unit 20 is realized by software, firmware, or the like. .. However, this is only an example, and some components in the data processing unit 20 may be realized by dedicated hardware, and the remaining components may be realized by software, firmware, or the like.

Next, the operation of the mirror surface shape measuring device 2 shown in FIG. 1 will be described. FIG. 4 is a flowchart showing a processing procedure of the data processing unit 20.
The light 3 reflected by the test mirror 1 is incident on the microlens array 11.
The plurality of microlenses 11a included in the microlens array 11 collect the light 3 reflected by the test mirror 1 on the Fresnel zone plate 13 of the translocation optical system 12.
The position where the light 3 is focused by the microlens 11a changes depending on the local inclination of the reflection point of the light 3 in the test mirror 1.

FIG. 5 is an explanatory diagram showing an image of light 3 by the microlens array 11 and an arrangement of a plurality of microlenses 11a included in the microlens array 11.
In FIG. 5, the image 51-1 is an image of the light 3 reflected by the split mirror 1-1, the image 51-2 is an image of the light 3 reflected by the split mirror 1-2, and the image 51-3 is an image of the light 3 reflected by the split mirror 1-2. It is an image of light 3 reflected by the split mirror 1-3.
Image 51-4 is an image of light 3 reflected by the split mirror 1-4, image 51-5 is an image of light 3 reflected by the split mirror 1-5, and image 51-6 is an image of light 3 reflected by the split mirror 1-5. It is an image of light 3 reflected by 6.

The microlens 11a-1 is a microlens 11a that collects the light 3 reflected by the split mirror 1-1 among the plurality of microlenses 11a included in the microlens array 11.
The microlens 11a-2 is a microlens 11a that collects the light 3 reflected by the split mirror 1-2 among the plurality of microlenses 11a included in the microlens array 11.
The microlens 11a-3 is a microlens 11a that collects the light 3 reflected by the split mirror 1-3 among the plurality of microlenses 11a included in the microlens array 11.

The microlens 11a-4 is a microlens 11a that collects the light 3 reflected by the split mirrors 1-4 among the plurality of microlenses 11a included in the microlens array 11.
The microlens 11a-5 is a microlens 11a that collects the light 3 reflected by the split mirror 1-5 among the plurality of microlenses 11a included in the microlens array 11.
The microlens 11a-6 is a microlens 11a that collects the light 3 reflected by the split mirror 1-6 among the plurality of microlenses 11a included in the microlens array 11.

In FIG. 5, eight microlenses 11a-1, microlenses 11a-2, microlenses 11a-3, microlenses 11a-4, microlenses 11a-5, and microlenses 11a-6 are arranged. An example is shown. However, this is only an example, and for example, 7 may be arranged or 9 may be arranged.
Further, FIG. 5 shows an example in which each of the microlenses 11a-1 to 11a-6 is arranged so as to be in contact with the adjacent microlens. However, each of the microlenses 11a-1 to 11a-6 may be arranged at equal intervals, and may be arranged at regular intervals with the adjacent microlenses. In FIG. 1, a plurality of microlenses 11a are arranged at regular intervals from adjacent microlenses.

The microlenses 11a- (1) and (2) collect the light 3 reflected by the split mirror 1-1 and the split mirror 1-2 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (2) (3) collect the light 3 reflected by each of the split mirrors 1-2 and the split mirrors 1-3 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (3) (4) collect the light 3 reflected by the dividing mirrors 1-3 and the dividing mirrors 1-4 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.

The microlenses 11a- (4) (5) collect the light 3 reflected by the split mirrors 1-4 and the split mirrors 1-5 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (5) (6) collect the light 3 reflected by the split mirrors 1-5 and the split mirrors 1-6 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (6) (1) collect the light 3 reflected by each of the split mirrors 1-6 and the split mirror 1-1 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.

In FIG. 5, the microlens 11a- (1) (2), the microlens 11a- (2) (3), the microlens 11a- (3) (4), the microlens 11a- (4) (5), the microlens An example is shown in which three 11a- (5) (6) and three microlenses 11a- (6) (1) are arranged. However, this is only an example, and for example, two may be arranged, or four or more may be arranged.
Further, FIG. 5 shows an example in which each of the microlenses 11a- (1) (2) to 11a- (6) (1) is arranged so as to be in contact with the adjacent microlens. However, each of the microlenses 11a- (1) (2) to 11a- (6) (1) need only be arranged at equal intervals, and is arranged at regular intervals with the adjacent microlenses. There may be.

The Fresnel zone plate 13 diffracts more wavelength components having a longer wavelength among the plurality of wavelength components contained in the light 3 focused by the plurality of microlenses 11a.
For example, as shown in FIG. 1, the Fresnel zone plate 13 diffracts the wavelength component 15 having a wavelength longer than that of the short wavelength component 16 more than the short wavelength component 16.
The lens 14 causes the image pickup device 17 to image each of the plurality of wavelength components diffracted by the Fresnel zone plate 13 as a spot image. For example, the lens 14 causes the image sensor 17 to image each of the wavelength component 15 and the wavelength component 16 as spot images.

FIG. 6 is an explanatory diagram showing a spot image formed on the image sensor 17 by the image transfer optical system 12.
FIG. 6A shows a spot image 60 in which the light 3 focused by the microlens 11an is diffracted by the Fresnel zone plate 13 and then imaged on the image sensor 17 by the lens 14.
FIG. 6B shows a spot image 70 formed on the image sensor 17 by the lens 14 after the light 3 focused by the microlenses 11a- (1) and (2) is diffracted by the Fresnel zone plate 13. ing.

The spot image 60 contains a plurality of wavelength components. In the example of FIG. 6A, a short wavelength component 61, an intermediate wavelength component 62, and a long wavelength component 63 are shown as some wavelength components included in the spot image 60.
Since the short wavelength component 61, the intermediate wavelength component 62, and the long wavelength component 63 are components having different wavelengths from each other, the magnitude of diffraction by the Fresnel zone plate 13 is different from each other. Therefore, the shape of the spot image 60 becomes an elliptical shape extending in the radial direction. The radial direction is the direction from the center of the test mirror 1 toward the outer circumference.

The spot image 70 contains a plurality of wavelength components. In the example of FIG. 6B, a short wavelength component 71, an intermediate wavelength component 72, and a long wavelength component 73 are shown as some wavelength components included in the spot image 70.
Since the short wavelength component 71, the intermediate wavelength component 72, and the long wavelength component 73 have different wavelengths from each other, the magnitude of diffraction by the Fresnel zone plate 13 is different from each other. Therefore, the shape of the spot image 70 becomes an elliptical shape extending in the radial direction.
Further, since the spot image 70 is a spot image corresponding to the light 3 reflected by each of the two dividing mirrors adjacent to each other, there are two spot images 70 in the angular direction (see FIG. 5). Bright lines (1), (2), and (3) of light 3 reflected on each of the split mirrors are generated.

There is a step between the two split mirrors that are adjacent to each other, and the wave surface of the light 3 reflected by each of the two split mirrors has a relative piston that is twice the step. In the shape of the spot image 70 shown in FIG. 6B, the relative piston at the intermediate wavelength component 72 is an integral multiple of the wavelength (hereinafter referred to as N times), and the relative piston at the short wavelength component 71 is larger than the N times the wavelength. The shape is somewhat longer, with the relative piston at the long wavelength component 73 being somewhat shorter than N times the wavelength.
The bright line (1) of the spot image 70 crosses the center of the intermediate wavelength component 72 because the light 3 reflected by each of the two dividing mirrors adjacent to each other has the same phase in the intermediate wavelength component 72. The bright line (1) crosses to the right of the center of the short wavelength component 71 because the light 3 reflected by each of the two adjacent split mirrors is slightly out of phase with the short wavelength component 71. .. In the long wavelength component 73, the phase of the light 3 reflected by each of the two dividing mirrors adjacent to each other is shifted by a code opposite to that of the short wavelength component 71, so that the bright line (1) is the long wavelength component. Cross to the left of the center of 73.
Since the phase of the light 3 is aligned at the center of the wavelength component where the relative piston is N-1 times the wavelength or N + 1 times the wavelength, the two are deviated from the bright line (1) in the radial direction. Bright lines (2) and (3) occur. Although FIG. 6B shows a case where there are three bright lines, there are cases where four or more bright lines corresponding to an integral multiple of the wavelength are generated.
The relative phase, which is the phase difference of the light 3 reflected by each of the two split mirrors, is different for all the wavelength components included in the spot image 70, and the position of the bright line changes continuously. When all the wavelength components are combined, an interference fringe 74 having an inclination according to a step between the two split mirrors appears.

The image sensor 17 captures each spot image formed by the lens 14 of the image transfer optical system 12.
The image sensor 17 images, for example, the spot image 60 and the spot image 70, respectively.
The image sensor 17 outputs spot data to the data extraction unit 21 of the data processing unit 20 as data indicating the imaging results of each spot image.

For example, the data extraction unit 21 identifies the spot data DD _n in the split mirror included in the spot data output from the image sensor 17 based on the coordinate information stored in the internal memory, and spots in the split mirror. The data DD _n is output to the split mirror wave surface calculation unit 22 (step ST1 in FIG. 4).
Further, the data extraction unit 21 specifies, for example, the boundary spot data BD _n included in the spot data output from the image sensor 17 based on the coordinate information stored in the internal memory, and the boundary spot data BD _n is output to the step calculation unit 23 (step ST2 in FIG. 4).

When the split mirror wave plane calculation unit 22 receives the spot data DD _n in the split mirror from the data extraction unit 21, the wave plane of the split mirror 1-n is based on the imaging result of the spot image 60 indicated by the spot data DD _n in the split mirror. Is calculated (step ST3 in FIG. 4).
Hereinafter, the wave surface calculation process of the split mirror 1-n by the split mirror wave surface calculation unit 22 will be specifically described.

For example, the lateral magnification of the divided mirror 1-n to the microlens array 11 is ₁ × M, ₂ × M is the transverse magnification of the Fresnel zone plate 13 and the lens 14, the focal length of the microlens array 11 is assumed to be f.
When the mirror surface of the split mirror 1-n is tilted by θ = (θ _x , θ _y ) with respect to the incident surface of the light in the microlens array 11, the light 3 reflected by the split mirror 1-n is is incident on the microlens array 11 only tilted 2 [Theta], is transmitted through the microlens array 11 at an angle magnification 1 / M ₁ times. At this time, the spot image 60 imaged by the lens 14 is eccentric by 2θ _x f / M _{1 in the} x direction from the optical axis of the microlens 11an into which the light 3 is incident, and 2θ _{y in} the y direction. Only f / M _{1 is} eccentric.
Furthermore, the spot image 60, since it is formed on the image sensor 17 at _twice the lateral magnification _M, from the reference position of the spot image _(x 0, _{y 0),} in the x direction by 2 [Theta] _x fM ₂ / _{M 1} eccentric Then, the spot image 60 appears at a position eccentric by ₂ θ _y fM ₂ / M ₁ in the y direction. The position of the reference spot image (x ₀ , y ₀ ) is the position when θ _x = 0 and θ _y = 0.

From the image pickup result of the spot image 60 indicated by the spot data DD _n in the split mirror, the split mirror wave surface calculation unit 22 has a plurality of pixels g _k (k = 1, ..., K) in the image pickup device 17 corresponding to the spot image 60. ) The illuminance L _k and the x-coordinate x _{k in} which a plurality of pixels g _k exist are acquired. K is an integer greater than or equal to 2.
Splitting mirror wavefront calculation unit 22, as shown in the following equation (1), the product of each of the illuminance L _k in a plurality of pixels g _k, and x-coordinate x _k in which a plurality of pixels g _k are present Calculate the total Lx.

As shown in the following equation (2), the split mirror wave plane calculation unit 22 divides the total sum Lx of the products by the sum of the illuminance L _k of the plurality of pixels g _k , thereby dividing the center of gravity of the spot image 60 in the x direction. Calculate C _x .

The split mirror wave surface calculation unit 22 acquires the y coordinate y _{k in} which a plurality of pixels g _k exist from the imaging result of the spot image 60 indicated by the spot data DD _n in the split mirror.
Splitting mirror wavefront calculation unit 22, as shown in the following equation (3), the product of each of the illuminance L _k in a plurality of pixels g _k, and y-coordinate y _k to a plurality of pixels g _k are present Calculate the total Ly.

As shown in the following equation (4), the split mirror wave surface calculation unit 22 divides the total product Ly by the total sum of the illuminance L _k of the plurality of pixels g _k , thereby dividing the center of gravity of the spot image 60 in the y direction. to calculate the C _y.

As shown in the following equations (5) and (6), the split mirror wave surface calculation unit 22 determines the position of the reference spot image (x ₀ , y ₀ ) and the position of the center of gravity of the spot image 60 (C _x , C). _{From y} ) and the eccentricity of the spot image 60 (2θ _x fM ₂ / M ₁ , 2θ _y fM ₂ / M ₁ ), the local inclination (θ _x , θ _y ) of the split mirror 1-n is determined. calculate. The local inclination (θ _x , θ _y ) of the dividing mirror 1-n is the inclination of the reflection point of the light 3 in the dividing mirror 1-n.

The position (x ₀ , y ₀ ) of the reference spot image is an existing value and is stored in, for example, the internal memory of the split mirror wave surface calculation unit 22.
Further, the lateral magnification M ₁ × a lateral magnification M ₂ times, and each of the focal length f, is already values, for example, are stored in the internal memory of the divided mirror wavefront calculator 22.

Splitting mirror wavefront calculation unit 22, the local inclination of the divided mirror _{1-n (θ x, θ} y) when calculating the local slope of the divided mirror _{1-n (θ x, θ} y) from the divided mirror The wave surface of 1-n is calculated.
The wave surface of the split mirror 1-n is a curved surface in three-dimensional space. Assuming that the wave plane of the split mirror 1-n is represented by Z _1-n = W (x _j , y _j ), the wave plane Z _1-n of the split mirror 1-n and the local of the split mirror 1-n There is a relationship with the slope (θ _x , θ _y ) as shown in the following equation (7). (X _j , y _j ) is the position of the spot image 60 related to the split mirror 1-n, and j = 1, ..., J. J is an integer of 2 or more.

From the 2 × J relational expressions shown in the equation (7), it is possible to estimate the wave surface Z _1-n of the split mirror 1-n, which is the shape of the curved surface indicated by W (x _j , y _j ).
Since the process itself of estimating the wave surface Z _1-n of the split mirror 1-n from the 2 × J relational expressions is a known technique, detailed description thereof will be omitted.
In the equations (5), (6) and (7), the mirror surface shape and the wave surface shape are different by twice because of the folding back due to reflection. The fact that the local inclination of the wave surface can be calculated by the equations (5), (6), and (7) is not limited to the case where the test mirror 1 turns the light ray in the incident direction. However, (θ _x , θ _y ) coincides with the local inclination of the test mirror 1 when the test mirror 1 turns back the light beam in the incident direction, and the test mirror 1 emits the light ray in the incident direction. If it does not fold, it is necessary to multiply the local slope of the wave surface by the coefficient according to the fold angle and convert it.

When the step calculation unit 23 receives the boundary spot data BD _n from the data extraction unit 21, the step calculation unit 23 calculates the step gap between the two dividing mirrors based on the imaging result of the spot image 70 indicated by the boundary spot data BD _n (). Step ST4 in FIG. 4).
Hereinafter, the step Gap calculation process by the step calculation unit 23 will be specifically described.

The step calculation unit 23 calculates the inclination of the interference fringes 74 from the imaging result of the spot image 70 indicated by the boundary spot data BD _n .
That is, the step calculation unit 23 uses the imaging result of the spot image 70 as the image I (x, y), performs spatial Fourier transform on the image I (x, y), and obtains the Fourier transform result F (ωx, ωy).
The step calculation unit 23 converts the Fourier transform result F (ωx, ωy) into polar coordinates to obtain the polar coordinate transformation result G (r', θ') as shown in the following equation (8).

In the formula (8), exp (−α _{θ ′} r) is an envelope component of G (r ′, θ ′) that decreases exponentially as r ′ increases. α _θ'is an exponential decrease coefficient, and the smaller the exponential decrease coefficient α _θ' , the slower the decrease rate of the envelope. The exponential reduction coefficients α _θ'and θ'are dependent on each other. g (r', θ') is, for example, a vibration component represented by cos (r').
The step calculation unit 23 changes the θ'of the polar coordinate conversion result G (r', θ'), compares the exponential decrease coefficient α _{θ'corresponding} to each _θ' , and has the smallest exponential decrease coefficient α _{θ. '} Identify.
The direction of θ'corresponding to the smallest exponential decrease coefficient α _{θ'corresponds} to the inclination direction of the interference fringes 74 because it is the direction having the largest autocorrelation in the image I (x, y).
The step calculation unit 23 determines θ'corresponding to the smallest exponential decrease coefficient α _θ'in the inclination direction of the interference fringes 74.

When the step calculation unit 23 determines the inclination direction θ'of the interference fringes 74, the step calculation unit 23 calculates the step Gap between the two split mirrors from the inclination direction θ'.
For example, the formula for calculating the steps Gap _{1 and 2} between the split mirror 1-1 and the split mirror 1-2 is expressed as the following formula (9).

D _{1 and 2} are the aperture diameters of the microlenses 11a- (1) and (2), r _{1 and 2} are the distances from the center of the pupil to the microlenses 11a- (1) and (2), and f _{1 and 2} are the micro lenses. This is the focal length of the lenses 11a- (1) and (2).

Test mirror wavefront calculation unit 24, step _Gap, 1, 2 calculated by the step calculation unit _{23, Gap 2,3, Gap 3,4,} Gap 4,5, Gap 5,6, and _{Gap, 6,1,} divided Wave surfaces of the split mirrors 1-1 to 1-6 calculated by the mirror wave surface calculation unit 22 Z _1-1, Z _1-2, Z _1-3, Z _1-4, Z _1-5, Z _1-6 From, the wave surface of the test mirror 1 is calculated (step ST5 in FIG. 4).
Hereinafter, the wave surface calculation process of the test mirror 1 by the test mirror wave surface calculation unit 24 will be specifically described.

First, the test mirror wave surface calculation unit 24 sets the equation shown in the following equation (10).

Z _1-1 + p _1- (Z _1-2 + p ₂ ) = 2Gap _1,2
Z _1-2 + p _2- (Z _1-3 + p ₃ ) = 2Gap _2,3
Z _1-3 + p _3- (Z _1-4 + p ₄ ) = 2Gap _{3,4
Z 1-4 + p 4 - (Z} 1-5 + p 5) = 2Gap 4,5
Z _1-5 + p _5- (Z _1-6 + p ₆ ) = 2Gap _5,6
Z _1-6 + p _6- (Z _1-1 + p ₁ ) = 2Gap _6,1
(10)
In equation (10), p ₁ , p ₂ , p ₃ , p ₄ , p ₅ , and p ₆ are unknown parameters.
Gap _{1 and 2} are steps between the dividing mirror 1-1 and the dividing mirror 1-2, and Gap _{2 and 3} are steps between the dividing mirror 1-2 and the dividing mirror 1-3, Gap ₃ , ₄ Is a step between the split mirrors 1-3 and the split mirrors 1-4.
Gap ₄ , ₅ is the step between the dividing mirror 1-4 and the dividing mirror 1-5, Gap ₅ , ₆ is the step between the dividing mirror 1-5 and the dividing mirror 1-6, Gap ₆ , ₁ Is a step between the split mirror 1-6 and the split mirror 1-1.

The mirror wave surface calculation unit 24 estimates unknown parameters p ₁ , p ₂ , p ₃ , p ₄ , p ₅ , p ₆ in the equation shown in equation (10) by, for example, the least squares method. Since the estimation process itself of the unknown parameters p ₁ , p ₂ , p ₃ , p ₄ , p ₅ , and p ₆ is a known technique, detailed description thereof will be omitted.
The wave surface calculation unit 24 to be inspected corrects the wave surfaces Z _1-1 to Z _1-6 of the split mirrors 1-1 to _1-6 as in the following equation (11), and the corrected wave surface Z _1- the _{1 '~ Z 1-6',} the wavefront of the mirror 1.

Z _1-1 '= Z _1-1 + p ₁
Z _1-2 '= Z _1-2 + p ₂
Z _1-3 '= Z _1-3 + p ₃
Z _1-4 '= Z _1-4 + p ₄
Z _1-5 '= Z _1-5 + p ₅
Z _1-6 '= Z _1-6 + p ₆
(11)

In the above embodiment 1, the microlens array 11 has a plurality of microlenses 11a for condensing the light 3 reflected by the test mirror 1 in which a plurality of split mirrors 1-1 to 1-6 are combined. Of the plurality of wavelength components contained in the light 3 condensed by the plurality of microlenses 11a, the longer the wavelength component, the larger the diffraction, and each diffracted wavelength component is imaged as a spot image. Of the image pickup element 17 that captures the image of each spot imaged by the image change optical system 12, the image pickup element 17 imaged by the image transfer optical system 12, and the plurality of spot images imaged by the image pickup element 17, a plurality of split mirrors 1-1 In 1-6, the step calculation unit 23 that calculates the step between the two dividing mirrors based on the spot image corresponding to the light reflected by each of the two dividing mirrors adjacent to each other. The mirror surface shape measuring device 2 was configured to be provided. Therefore, the mirror surface shape measuring device 2 can calculate the step between the plurality of split mirrors 1-1 to 1-6 possessed by the test mirror 1 without using a drive mechanism that requires maintenance. ..

Embodiment 2.
In the second embodiment, a mirror surface shape measuring device including the first cylindrical lens array 81 and the second cylindrical lens array 82 will be described.

FIG. 7 is a configuration diagram showing a reflector system including the mirror surface shape measuring device 2 according to the second embodiment. In FIG. 7, the same reference numerals as those in FIG. 1 indicate the same or corresponding parts, and thus the description thereof will be omitted.
In the reflector system shown in FIG. 7, it is assumed that the test mirror 1 is a two-wheeled band mirror.
The test mirror 1 is a combination of a plurality of split mirrors 1-1 to 1-6, 1-11 to 1-22.
Each of the split mirrors 1-1 to 1-6 and 1-11 to 1-22 is a partial mirror that constitutes a part of the test mirror 1.

The first cylindrical relay lens array 81 is arranged between the test mirror 1 and the second cylindrical relay lens array 82, and is arranged parallel to the xy plane.
The first cylindrical relay lens array 81 includes a plurality of cylindrical lenses 81a on the surface on the side of the test mirror 1, and a plurality of cylindrical lenses 81b on the surface on the side of the second cylindrical relay lens array 82.
Each of the plurality of cylindrical lenses 81a and the plurality of cylindrical lenses 81b are arranged in the x direction.
The plurality of cylindrical lenses 81a are paired with any one of the plurality of cylindrical lenses 81b.
The pair of the cylindrical lens 81a and the cylindrical lens 81b are arranged so that the focused lines coincide with each other.
In the pair of the cylindrical lens 81a and the cylindrical lens 81b, the image of the light 3 reflected by any of the dividing mirrors 1-1 to 1-6 and 1-11 to 1-22 is parallel to the y-axis. Axis is inverted as a symmetric axis.

The second cylindrical relay lens array 82 is arranged between the first cylindrical relay lens array 81 and the microlens array 11, and is arranged parallel to the xy plane.
The second cylindrical lens array 82 includes a plurality of cylindrical lenses 82a on the surface of the first cylindrical relay lens array 81, and a plurality of cylindrical lenses 82b on the surface of the microlens array 11 side.
The plurality of cylindrical lenses 82a are paired with any one of the plurality of cylindrical lenses 82b.
The pair of the cylindrical lens 82a and the cylindrical lens 82b are arranged so that the focused lines coincide with each other.
The pair of the cylindrical lens 82a and the cylindrical lens 82b inverts the image of the light 3 emitted from the cylindrical relay lens 81.

The pitch of the plurality of cylindrical lenses 82a is the same as the pitch of the plurality of cylindrical lenses 81a. However, the same pitch is not limited to exactly the same pitch, and the pitch may be different within a range where there is no practical problem.
The arrangement direction of the plurality of cylindrical lenses 82a is different from the arrangement direction of the plurality of cylindrical lenses 81a.
In the mirror surface shape measuring device 2 shown in FIG. 7, the arrangement direction of the plurality of cylindrical lenses 82a is a direction inclined by 60 degrees from the x direction. However, this is only an example, and the arrangement direction of the plurality of cylindrical lenses 82a may be, for example, a direction inclined by 40 degrees from the x direction or a direction inclined by 50 degrees.
Further, in the mirror surface shape measuring device 2 shown in FIG. 7, the first cylindrical relay lens array 81 includes a plurality of cylindrical lenses 81a on the surface on the test mirror 1 side, and the surface on the second cylindrical relay lens array 82 side. Is equipped with a plurality of cylindrical lenses 81b. However, this is only an example, and the first cylindrical relay lens is arranged by arranging the cylindrical lens array provided with the plurality of cylindrical lenses 81a and the cylindrical lens array provided with the plurality of cylindrical lenses 81b so as to face each other. The array 81 may be configured.
Further, in the mirror surface shape measuring device 2 shown in FIG. 7, the second cylindrical relay lens array 82 includes a plurality of cylindrical lenses 82a on the surface on the side of the first cylindrical relay lens array 81, and the surface on the microlens array 11 side. Is equipped with a plurality of cylindrical lenses 82b. However, this is only an example, and the second cylindrical relay lens is provided by arranging the cylindrical lens array provided with the plurality of cylindrical lenses 82a and the cylindrical lens array provided with the plurality of cylindrical lenses 82b so as to face each other. The array 82 may be configured.

FIG. 8 is an explanatory diagram showing an image of light 3 by the microlens array 11 and an arrangement of a plurality of microlenses 11a included in the microlens array 11. In FIG. 8, the same reference numerals as those in FIG. 5 indicate the same or corresponding parts, and thus the description thereof will be omitted.
Image 51-11 is an image of light 3 reflected by the split mirror 1-11, image 51-12 is an image of light 3 reflected by the split mirror 1-12, and image 51-13 is an image of light 3 reflected by the split mirror 1-12. It is an image of light 3 reflected by 13.
Image 51-14 is an image of light 3 reflected by the split mirror 1-14, image 51-15 is an image of light 3 reflected by the split mirror 1-15, and image 51-16 is an image of light 3 reflected by the split mirror 1-15. It is an image of light 3 reflected by 16.
Image 51-17 is an image of light 3 reflected by the split mirror 1-17, image 51-18 is an image of light 3 reflected by the split mirror 1-18, and image 51-19 is an image of light 3 reflected by the split mirror 1-18. It is an image of light 3 reflected by 19.
Image 51-20 is an image of light 3 reflected by the split mirror 1-20, image 51-21 is an image of light 3 reflected by the split mirror 1-21, and image 51-22 is an image of light 3 reflected by the split mirror 1-21. It is an image of light 3 reflected by 22.

The microlens 11a-11 is a microlens 11a that collects the light 3 reflected by the split mirror 1-11 among the plurality of microlenses 11a included in the microlens array 11.
The microlens 11a-12 is a microlens 11a that collects the light 3 reflected by the split mirror 1-12 among the plurality of microlenses 11a included in the microlens array 11.
The microlens 11a-13 is a microlens 11a that collects the light 3 reflected by the split mirror 1-13 among the plurality of microlenses 11a included in the microlens array 11.

The microlens 11a-14 is a microlens 11a that collects the light 3 reflected by the split mirror 1-14 among the plurality of microlenses 11a included in the microlens array 11.
The microlens 11a-15 is a microlens 11a that collects the light 3 reflected by the split mirror 1-15 among the plurality of microlenses 11a included in the microlens array 11.
The microlens 11a-16 is a microlens 11a that collects the light 3 reflected by the split mirror 1-16 among the plurality of microlenses 11a included in the microlens array 11.

The microlens 11a-17 is a microlens 11a that collects the light 3 reflected by the split mirror 1-17 among the plurality of microlenses 11a included in the microlens array 11.
The microlens 11a-18 is a microlens 11a that collects the light 3 reflected by the split mirror 1-18 among the plurality of microlenses 11a included in the microlens array 11.
The microlens 11a-19 is a microlens 11a that collects the light 3 reflected by the split mirror 1-19 among the plurality of microlenses 11a included in the microlens array 11.

The microlens 11a-20 is a microlens 11a that collects the light 3 reflected by the split mirror 1-20 among the plurality of microlenses 11a included in the microlens array 11.
The microlens 11a-21 is a microlens 11a that collects the light 3 reflected by the split mirror 1-21 among the plurality of microlenses 11a included in the microlens array 11.
The microlens 11a-22 is a microlens 11a that collects the light 3 reflected by the split mirror 1-22 among the plurality of microlenses 11a included in the microlens array 11.

The microlenses 11a- (11) (12) collect the light 3 reflected by each of the split mirrors 1-11 and the split mirrors 1-12 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (12) (13) collect the light 3 reflected by each of the split mirrors 1-12 and the split mirrors 1-13 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (13) (14) collect the light 3 reflected by each of the split mirrors 1-13 and the split mirrors 1-14 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.

The microlenses 11a- (14) (15) collect the light 3 reflected by each of the split mirrors 1-14 and the split mirrors 1-15 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (15) (16) collect the light 3 reflected by each of the split mirrors 1-15 and the split mirrors 1-16 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (16) (17) collect the light 3 reflected by each of the split mirrors 1-16 and the split mirrors 1-17 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.

The microlenses 11a- (17) (18) collect the light 3 reflected by each of the split mirrors 1-17 and the split mirrors 1-18 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (18) (19) collect the light 3 reflected by each of the split mirrors 1-18 and the split mirrors 1-19 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (19) (20) collect the light 3 reflected by each of the split mirrors 1-19 and the split mirrors 1-20 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.

The microlenses 11a- (20) (21) collect the light 3 reflected by each of the split mirror 1-20 and the split mirror 1-21 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (21) (22) collect the light 3 reflected by each of the split mirrors 1-21 and the split mirrors 1-22 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (22) (11) collect the light 3 reflected by each of the split mirrors 1-22 and the split mirrors 1-11 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.

The microlenses 11a- (1) (11) collect the light 3 reflected by each of the split mirror 1-1 and the split mirror 1-11 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (2) (11) collect the light 3 reflected by each of the split mirrors 1-2 and the split mirrors 1-11 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (2) (12) collect the light 3 reflected by each of the split mirrors 1-2 and the split mirrors 1-12 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.

The microlenses 11a- (2) (13) collect the light 3 reflected by each of the split mirrors 1-2 and the split mirrors 1-13 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (3) (13) collect the light 3 reflected by the split mirrors 1-3 and the split mirrors 1-13 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (3) (14) collect the light 3 reflected by each of the split mirrors 1-3 and the split mirrors 1-14 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.

The microlenses 11a- (3) (15) collect the light 3 reflected by each of the split mirrors 1-3 and the split mirrors 1-15 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (4) (15) collect the light 3 reflected by the split mirrors 1-4 and the split mirrors 1-15 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (4) (16) collect the light 3 reflected by the split mirrors 1-4 and the split mirrors 1-16 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.

The microlenses 11a- (4) (17) collect the light 3 reflected by each of the split mirrors 1-4 and the split mirrors 1-17 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (5) (17) collect the light 3 reflected by each of the split mirrors 1-5 and the split mirrors 1-17 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (5) (18) collect the light 3 reflected by each of the split mirrors 1-5 and the split mirrors 1-18 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.

The microlenses 11a- (5) (19) collect the light 3 reflected by each of the split mirrors 1-5 and the split mirrors 1-19 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (6) (19) collect the light 3 reflected by each of the split mirrors 1-6 and the split mirrors 1-19 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (6) (20) collect the light 3 reflected by each of the split mirrors 1-6 and the split mirrors 1-20 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.

The microlenses 11a- (6) (21) collect the light 3 reflected by each of the split mirrors 1-6 and the split mirrors 1-21 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (1) (21) collect the light 3 reflected by each of the split mirror 1-1 and the split mirror 1-21 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.
The microlenses 11a- (1) and (22) collect the light 3 reflected by the split mirror 1-1 and the split mirror 1-22 among the plurality of microlenses 11a included in the microlens array 11. It is a shining microlens 11a.

FIG. 9 shows an image of light 3 by the microlens array 11, an arrangement of a plurality of microlenses 11a included in the microlens array 11, an arrangement of a first cylindrical lens array 81, and a second cylindrical lens array. It is explanatory drawing which shows the arrangement of 82.
The plurality of microlenses 11a shown in FIG. 9 are arranged so that the effective diameter of the microlenses 11a with respect to the lens pitch is √3 / 2.
The arrangement direction of the plurality of cylindrical lenses 81a is the x direction.
Each of the cylindrical lenses 81a is arranged in parallel with the plurality of microlenses 11a arranged in a row in the y direction among the plurality of microlenses 11a included in the microlens array 11.
The pitch of the plurality of cylindrical lenses 81a is 1 / of the pitch of the plurality of microlenses 11a arranged in a direction inclined by 30 degrees from the x direction among the plurality of microlenses 11a included in the microlens array 11. It is cos (30) times.

The arrangement direction of the plurality of cylindrical lenses 82a is a direction inclined by about 60 degrees from the x direction.
Each of the cylindrical lenses 82a is arranged in parallel with a plurality of microlenses 21a arranged in a row in a direction inclined by 30 degrees from the x direction among the plurality of microlenses 11a included in the microlens array 11. ing.
The pitch of the plurality of cylindrical lenses 82a is 1 / cos (30) times the pitch of the plurality of microlenses 12a arranged in the y direction among the plurality of microlenses 11a included in the microlens array 11. ..
The light 3 focused by each of the plurality of microlenses 11a shown in FIG. 9 is light that is not divided by the boundaries of the plurality of cylindrical lenses 81a, and is not divided by the boundaries of the plurality of cylindrical lenses 82a. It is light.

As shown in FIGS. 1 and 5, when the test mirror 1 is a one-wheeled mirror and a plurality of split mirrors 1-1 to 1-6 are combined, a step between the two split mirrors. Bright lines (1) to (3) corresponding to are generated in the angular direction.
In the mirror surface shape measuring device 2 shown in FIG. 1, the transposition optical system 12 has a larger wavelength component among a plurality of wavelength components contained in the light 3 condensed by the plurality of microlenses 11a, respectively. It is diffracted, and each of the diffracted wavelength components is imaged on the image pickup device 17 as a spot image. Therefore, the step calculation unit 23 can calculate the inclination of the interference fringes 74 from the imaging result of the spot image 70, and calculate the step between the two split mirrors from the inclination of the interference fringes 74.

However, as shown in FIGS. 7 and 8, the test mirror 1 is a two-wheeled band mirror, and a plurality of split mirrors 1-1 to 1-6, 1-11 to 1-22 are combined. In this case, a plurality of bright lines corresponding to the steps between the two split mirrors arranged in the radial direction are generated in the radial direction.
Even if the transposition optical system 12 diffracts the longer wavelength component of the plurality of wavelength components contained in the light 3 condensed by the plurality of microlenses 11a, the longer the wavelength component, the larger the wavelength component is generated in the radial direction. Multiple bright lines overlap. Therefore, the step calculation unit 23 cannot calculate the inclination of the interference fringes 74 from the imaging result of the spot image 70, and cannot calculate the step between the two split mirrors arranged in the radial direction. ..

In the mirror surface shape measuring device 2 shown in FIG. 7, the arrangement direction of the plurality of cylindrical lenses 81a and the arrangement direction of the plurality of cylindrical lenses 82a are different by 60 degrees. Further, each of the cylindrical lens 81a and the cylindrical lens 82a inverts the image of the light 3 reflected by any of the dividing mirrors 1-1 to 1-6 and 1-11 to 1-22. There is. As a result, the image of the light 3 reflected by any of the split mirrors is rotated by 120 degrees.
When the arrangement directions of the plurality of cylindrical lenses 81a and the arrangement directions of the plurality of cylindrical lenses 82a differ by 60 degrees, a plurality of bright lines corresponding to the steps between the two dividing mirrors arranged in the radial direction. Tilts 120 degrees with respect to the radial direction. Further, the plurality of bright lines corresponding to the steps between the two split mirrors arranged in the angular direction are inclined by 30 degrees with respect to the radial direction.
Due to the difference in inclination with respect to the radial direction, the step calculation unit 23 includes a plurality of bright lines corresponding to the steps between the two split mirrors arranged in the radial direction and the two split mirrors arranged in the angular direction. It is possible to distinguish from a plurality of bright lines corresponding to the steps between them.
Therefore, the step calculation unit 23 can calculate a plurality of bright lines corresponding to the steps between the two dividing mirrors arranged in the radial direction as the inclination of the interference fringes 74 from the imaging result of the spot image 70. it can. Further, the step calculation unit 23 can calculate a plurality of bright lines corresponding to the steps between the two dividing mirrors arranged in the angular direction as the inclination of the interference fringes 74 from the imaging result of the spot image 70. ..

Hereinafter, the step calculation process by the step calculation unit 23 will be specifically described.
Due to the difference in inclination with respect to the radial direction, the step calculation unit 23 includes a plurality of bright lines corresponding to the steps between the two split mirrors arranged in the radial direction and the two split mirrors arranged in the angular direction. Distinguish between multiple bright lines corresponding to the steps between them.
The step calculation unit 23 determines the inclination direction θ'of the interference fringes 74 for the plurality of bright lines corresponding to the steps between the two split mirrors arranged in the radial direction, as in the first embodiment.
In the step calculation unit 23, since a plurality of bright lines corresponding to the steps between the two split mirrors arranged in the radial direction are inclined by 120 degrees with respect to the radial direction, the step calculation unit 23 is 120 degrees with respect to the radial direction. The inclination direction θ'of the interference fringe 74 is corrected based on the inclination of.
For example, the correction formula for the inclination direction θ _{1, 22'of the} interference fringes 74 related to the split mirror 1-1 and the split mirror 1-22 is expressed as the following formula (12).

In the formula (12), β ₁ , ₂₂ are the inclination directions of the corrected interference fringes 74.

The step calculation unit 23 calculates the step Gap between the two split mirrors arranged in the radial direction from the tilt direction of the corrected interference fringes 74.
For example, the calculation formula for the steps Gap _{1 and 22} between the split mirror 1-1 and the split mirror 1-22 is expressed as the following formula (13).

D _1,22 is the aperture diameter of the microlenses 11a- (1) (22), r _1,22 is the distance from the center of the pupil to the microlenses 11a- (1) (22), and f _1,22 is the micro. This is the focal length of the lenses 11a- (1) and (22).

The step calculation unit 23 determines the inclination direction θ'of the interference fringes 74 for the plurality of bright lines corresponding to the steps between the two split mirrors arranged in the angular direction, as in the first embodiment.
In the step calculation unit 23, since a plurality of bright lines corresponding to the steps between the two split mirrors arranged in the angular direction are inclined by 30 degrees with respect to the radial direction, the step calculation unit 23 is 30 degrees with respect to the radial direction. The inclination direction θ'of the interference fringe 74 is corrected based on the inclination.
For example, the correction formula for the inclination directions θ ₁₂ , 13'of the interference fringes 74 related to the split mirror 1-12 and the split mirror 1-13 is expressed as the following formula (14).

In the formula (14), β _{12 and 13} are the inclination directions of the corrected interference fringes 74.

The step calculation unit 23 calculates the step Gap between the two split mirrors arranged in the angular direction from the tilt direction of the corrected interference fringes 74.
For example, the calculation formulas for the steps Gap _{12 and 13} between the split mirrors 1-12 and the split mirrors 1-13 are expressed as the following formula (15).

D _{12 and 13} are the aperture diameters of the microlenses 11a- (12) and (13), r _{12 and 13} are the distances from the center of the pupil to the microlenses 11a- (12) and (13), and f _{12 and 13} are the micro lenses. It is the focal length of the lenses 11a-(12) (13).

In the second embodiment as described above, the first cylindrical lens array 81 having the plurality of cylindrical lenses 81a and the second cylindrical lens array 82 having the plurality of cylindrical lenses 82a are provided, and the first cylindrical lens array 81 and the first cylindrical lens array 81 are provided. Each of the second cylindrical lens arrays 82 is arranged between the test mirror 1 and the microlens array 11, and the arrangement direction of the plurality of cylindrical lenses 81a included in the first cylindrical lens array 81 and the second The mirror surface shape measuring device 2 is configured so that the arrangement directions of the plurality of cylindrical lenses 82a included in the cylindrical lens array 82 are different from each other. Therefore, in the mirror surface shape measuring device 2, even if the mirror 1 is a two-wheeled mirror, the mirror surface measuring device 2 is used between a plurality of split mirrors possessed by the mirror 1 without using a drive mechanism that requires maintenance. Steps can be calculated.

In the mirror surface shape measuring device 2 shown in FIG. 7, the mirror 1 to be inspected is a two-wheeled band mirror, and the step calculation unit 23 is a plurality of split mirrors 1 possessed by the inspected mirror 1 which is a mirror of the two-wheeled band. The step between -1 to 1-6 and 1-11 to 1-22 is calculated. However, this is only an example, and the test mirror 1 may be a mirror having a three-wheeled band or more, and the step calculation unit 23 may have a step between a plurality of split mirrors possessed by the mirror having the three-wheeled band or more. May be calculated.

In the present invention, within the scope of the invention, it is possible to freely combine each embodiment, modify any component of each embodiment, or omit any component in each embodiment. ..

The present invention is suitable for a mirror surface shape measuring device, a mirror surface shape measuring method, and a reflector system for calculating a step between a plurality of split mirrors.

1 Specimen to be inspected, 1-1 to 1-6, 1-11 to 1-22 Divided mirror, 2 Mirror surface shape measuring device, 3 Light, 11 Microlens array, 11a Microlens, 11a-1, 11a-2, 11a -3,11a-4,11a-5,11a-6,11a-11,11a-12,11a-13,11a-14,11a-15,11a-16,11a-17,11a-18,11a-19 , 11a-20, 11a-21,11a-22 Microlens, 11a- (1) (2), 11a- (2) (3), 11a- (3) (4), 11a- (4) (5) , 11a- (5) (6), 11a- (6) (1), 11a- (11) (12), 11a- (12) (13), 11a- (13) (14), 11a- (14) ) (15), 11a- (15) (16), 11a- (16) (17), 11a- (17) (18), 11a- (18) (19), 11a- (19) (20), 11a- (20) (21), 11a- (21) (22), 11a- (22) (11), 11a- (1) (11), 11a- (2) (11), 11a- (2) (12), 11a- (2) (13), 11a- (3) (13), 11a- (3) (14), 11a- (3) (15), 11a- (4) (15), 11a -(4) (16), 11a- (4) (17), 11a- (5) (17), 11a- (5) (18), 11a- (5) (19), 11a- (6) ( 19), 11a- (6) (20), 11a- (6) (21), 11a- (1) (21), 11a- (1) (22) Microlens, 12 conversion optical system, 13 Frenel zone Plate, 13 lens, 15 wavelength component, 16 wavelength component, 17 image pickup element, 20 data processing unit, 21 data extraction unit, 22 split mirror wave surface calculation unit, 23 step calculation unit, 24 test mirror wave surface calculation unit, 31 data extraction Circuit, 32 split mirror wave surface calculation circuit, 33 step calculation circuit, 34 test mirror wave surface calculation circuit, 41 memory, 42 processor, 51-1, 51-2, 51-3, 51-4, 51-5, 51- 6,51-11,51-12,51-13,51-14,51-15,51-16,51-17,51-18,51-19,51-20,51-21,51-22 Image , 60 spot image, 61 short wavelength component, 62 intermediate wavelength component, 63 long wavelength component, 70 spot image, 71 short wavelength component, 72 intermediate wavelength component, 73 long wavelength component, 74 interference fringes, 81 First Cylindrical Relay Lens Array, 81a, 81b Cylindrical Lens, 82 Second Cylindrical Relay Lens Array, 82a, 82b Cylindrical Lens.

Claims (6)

1. A microlens array having multiple microlenses that collects the light reflected by the test mirror, which is a combination of multiple split mirrors.
   Of the plurality of wavelength components contained in the light focused by the plurality of microlenses, the longer the wavelength component is, the larger the diffraction is, and each diffracted wavelength component is imaged as a spot image. Optical system and
   An image sensor that captures each spot image formed by the image transfer optical system,
   Of the plurality of spot images captured by the image sensor, the above 2 is based on the spot image corresponding to the light reflected by the two split mirrors adjacent to each other in the plurality of split mirrors. A mirror surface shape measuring device equipped with a step calculation unit that calculates the step between two split mirrors.
2. Among the plurality of spot images captured by the image sensor, a split mirror wave surface calculation unit that calculates the wave plane of each split mirror based on the spot image corresponding to the light reflected by each split mirror is provided. The mirror surface shape measuring device according to claim 1.
3. A test mirror wave surface calculation unit for calculating the wave surface of the test mirror from the step calculated by the step calculation unit and the wave surface of each of the split mirrors calculated by the split mirror wave surface calculation unit is provided. The mirror surface shape measuring device according to claim 2.
4. A first cylindrical lens array with multiple cylindrical lenses,
   With a second cylindrical lens array with multiple cylindrical lenses,
   Each of the first cylindrical lens array and the second cylindrical lens array is arranged between the test mirror and the microlens array.
   The mirror surface shape measurement according to claim 1, wherein the arrangement direction of the plurality of cylindrical lenses included in the first cylindrical lens array is different from the arrangement direction of the plurality of cylindrical lenses included in the second cylindrical lens array. apparatus.
5. A microlens array having multiple microlenses that collects the light reflected by the test mirror, which is a combination of multiple split mirrors.
   Of the plurality of wavelength components contained in the light focused by the plurality of microlenses, the longer the wavelength component is, the larger the diffraction is, and each diffracted wavelength component is imaged as a spot image. Optical system and
   When an image sensor for capturing each spot image formed by the image transfer optical system is provided.
   Among the plurality of spot images imaged by the image sensor, the step calculation unit creates a spot image corresponding to the light reflected by each of the two split mirrors adjacent to each other in the plurality of split mirrors. A mirror surface shape measuring method for calculating a step between the two split mirrors based on the above.
6. A test mirror in which multiple split mirrors are combined,
   A mirror surface shape measuring device for calculating a step between two divided mirrors adjacent to each other among the plurality of divided mirrors is provided.
   The reflector system according to any one of claims 1 to 4, wherein the mirror surface shape measuring device is the mirror surface shape measuring device according to any one of claims 1 to 4.

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