JP4133753B2 - Method of measuring optical interference of detour surface and interferometer device for detour surface measurement - Google Patents

Description

  The present invention relates to a light-wave interference measuring method of a detour surface for measuring the shape of a detoured test surface over substantially the entire area, and an interferometer device for detour surface measurement.

  Conventionally, an aperture synthesis method is known as a technique used when a surface to be measured is larger than a single measurable range of an interferometer device. In this method, the test surface is divided into a plurality of small areas such that adjacent portions partially overlap, the measurement is performed for each small area, each measurement result is processed, and then the measurement results are connected. Thus, various aperture synthesis methods have been proposed depending on the shape of the target test surface and the data processing method (see Patent Documents 1 to 3 below).

  There is also known an interferometer device including an alignment optical system for aligning a reference surface and a test surface. The alignment optical system is configured to form the return light of the measurement light reflected by the reference surface and the test surface as an alignment light image (both are dotted), and the two alignment light images are It is possible to easily align the reference surface and the test surface by adjusting the inclination of the test surface so as to coincide with each other.

  Conventionally, two alignment light images obtained by such an alignment optical system are displayed on the screen of the display device, and the positions of the two alignment light images are specified on a coordinate system corresponding to the display screen, A technique for automatically aligning a reference surface and a test surface based on information is known (see Patent Document 4 below).

JP 2002-162214 A JP-A-8-219737 JP-A-10-332350 US Pat. No. 5,549,925

  By the way, if the undulation of the test surface is large or wavy, even if the reference surface and the test surface are aligned so that interference fringes are generated on the entire test surface, Since the inclination with respect to the surface becomes steep in a part of the test surface, the density of the generated interference fringes becomes too high for the steep portions, and interference fringes that can be resolved by the imaging means may not be obtained. . In order to measure a test surface having such a steep swell (hereinafter sometimes referred to as “detour”) over substantially the entire area, the test surface is changed by changing the inclination of the test surface with respect to the reference surface several times. It is necessary to measure the inspection surface for each region where interference fringes that can be resolved by the imaging means are obtained, and to connect the obtained measurement results by the aperture synthesis method.

  Until now, when the inclination angle distribution of the entire test surface is known in advance, such as a paraboloid or a spherical surface, the test surface can be changed by sequentially changing the inclination of the test surface according to the inclination angle distribution. It was possible to measure the shape of the entire area. However, in the case of a detour shape in which the inclination angle distribution over the entire test surface cannot be known in advance, the tilt adjustment of the test surface has to rely on judgment based on the experience of the operator. For this reason, there are problems such as that a stable measurement result cannot be obtained, the operator is burdened with a lot of load, and the measurement time is long.

  The present invention has been made in view of such circumstances, and it is possible to easily measure a detoured surface to be measured over substantially the entire area, and to obtain a stable measurement result. An object of the present invention is to provide an interferometer device for measuring a detour surface.

In order to solve the above problems, a method for measuring a light wave interference of a detour surface according to the present invention is as follows:
An interference optical system that obtains an image of interference fringes caused by interference between the reference light reflected from the reference surface and the test surface light reflected from the test surface by irradiating the reference surface and the test surface with measurement light; In an interferometer apparatus that includes an alignment mechanism that adjusts an inclination posture of the test surface with respect to a reference surface, in a detoured surface light wave interference measurement method that obtains a shape of a substantially entire area of the detoured test surface,
After adjusting the inclination posture of the test surface with respect to the reference surface and performing a starting interference fringe generation procedure for generating a first starting interference fringe corresponding to a starting region that is a starting point of the entire area of the test surface,
Origin interference fringe analysis procedure for determining the shape of the origin region based on the origin interference fringes;
An inclination angle calculation procedure for calculating an inclination angle with respect to the reference plane of an adjacent area partially including a peripheral edge of the starting area based on the shape of the starting area;
An adjacent interference fringe that adjusts an inclination posture of the test surface with respect to the reference surface so that an inclination angle of the adjacent region with respect to the reference surface is approximately 0 degrees to generate an adjacent interference fringe corresponding to the adjacent region. The generation procedure
While replacing the adjacent interference fringes with the next starting interference fringes with the adjacent starting fringes, repeatedly performing each time the replacement is performed, and sequentially determining the shape of each area of the test surface, and each of these areas by the aperture synthesis method By connecting different shapes, the shape of substantially the entire region in the measurement region of the surface to be measured is obtained.

When the interferometer device includes an alignment optical system that obtains alignment light images of the reference light and the test surface light, in the starting interference fringe generation procedure,
A distribution range of the alignment light image of the test surface light is obtained on a coordinate system corresponding to the imaging surface of the alignment optical system, and the distribution light is divided into a plurality of areas, and the alignment light image occupies each area. Calculating a ratio, obtaining a center of gravity of the alignment light image in an area where the ratio is maximum, and tilting the test surface with respect to the reference surface so that the center of gravity substantially overlaps the alignment light image of the reference light May be adjusted to generate the first starting interference fringes.

  Further, it is preferable that a smoothing process is performed on the images of the starting interference fringes and the adjacent interference fringes to determine the position ranges of these interference fringes.

In order to solve the above problem, an interferometer device for measuring a detour surface according to the present invention includes:
An interference optical system for obtaining an image of interference fringes caused by optical interference between the reference light reflected from the reference surface and the test surface light reflected from the test surface by irradiating the reference surface and the test surface with illumination light; In an interferometer apparatus comprising an alignment mechanism that adjusts an inclination posture of the test surface with respect to the reference surface,
Adjusting the inclination posture of the test surface with respect to the reference surface, starting interference fringe generating means for generating a first starting interference fringe corresponding to a starting region serving as a starting point of the whole area measurement of the test surface;
Origin interference fringe analysis means for determining the shape of the origin region based on the origin interference fringes;
An inclination angle calculating means for calculating an inclination angle with respect to the reference plane of an adjacent area partially including a peripheral edge of the starting area based on the shape of the starting area;
An adjacent interference fringe that adjusts an inclination posture of the test surface with respect to the reference surface so that an inclination angle of the adjacent region with respect to the reference surface is approximately 0 degrees to generate an adjacent interference fringe corresponding to the adjacent region. Generating means;
While replacing the adjacent interference fringe with the next starting interference fringe with the adjacent starting area, the processing by the fringe analysis inclination angle calculating means and the adjacent interference fringe generating means is repeatedly performed each time the replacement is performed. And a fringe analysis calculation means for obtaining the shape of the entire surface within the measurement region of the surface to be examined by sequentially obtaining the shape of the surface to be examined and connecting the shapes of the regions by an aperture synthesis method. It is what.

  According to the optical interference measurement method for a detour surface according to the present invention, by performing the above-described procedure, it is possible to easily measure the detoured test surface over substantially the entire area and obtain a stable measurement result. be able to.

  Further, according to the interferometer device for measuring a detoured surface according to the present invention, by providing the above configuration, it is possible to automatically measure the detoured test surface over almost the entire area and to be stable. Measurement results can be obtained.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings.
<Interferometer device for detour surface measurement>
First, based on FIG. 1 and FIG. 2, the structure of the interferometer apparatus for detour surface measurement which concerns on one Embodiment of this invention is demonstrated. FIG. 1 is a schematic configuration diagram of an interferometer device for detour surface measurement according to an embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of a controller shown in FIG. In the following description, the horizontal direction in FIG. 1 is referred to as the X direction, the direction perpendicular to the X direction in the paper is referred to as the Z direction, and the direction perpendicular to the paper is referred to as the Y direction.

  An interferometer apparatus 10 shown in FIG. 1 is a Fizeau interferometer apparatus equipped with a light source 11 having a long coherence distance, such as a laser light source, and in the order in which light emitted from the light source 11 travels, a magnifying lens 13 and a beam splitter. 15, 17, a collimator lens 19, and a reference plate 21. Although not shown, the reference plate 21 includes a reference plate alignment mechanism for adjusting the inclination angle of the reference plate 21 with respect to the optical axis (not shown) of the interferometer device 10 and the reference plate 21 in the optical axis direction. A fringe scan adapter is provided for fine movement.

  The subject 27 has a curved test surface 27a. The test surface 27a faces the reference surface 21a of the reference plate 21, and a predetermined distance is provided between the reference surface 21a and the test surface 27a. Is placed on the placement stage 29 so as to be free.

  In the present embodiment, the “detoured test surface” is defined as follows. That is, when the reference surface and the test surface are aligned so that the interference fringes are generated on the entire surface of the test surface on average, the interference fringe image of the test surface imaged on the image sensor (for example, CCD) A test surface in which an interference fringe area that is so fine that it cannot be resolved together with an interference fringe area that can be resolved by the imaging device is referred to as a detoured test surface. Note that the interference fringe area that is so fine that it cannot be resolved by the image sensor means that when the image sensor is a general CCD, one or more fringes are generated in approximately three pixels and the sampling point is sufficient to satisfy the sampling theorem. It means the area where cannot be obtained.

  The placement stage 29 is held by two-stage swivel stages 31 and 33 constituting an alignment mechanism of the test surface 27a. The two swivel stages 31 and 33 are placed on the placement board 37 via the XY stage 35. Has been placed. The swivel stage 31 rotates along the XZ plane (plane extending in the X and Z directions), and the swivel stage 33 rotates along the YZ plane (plane extending in the Y and Z directions). The inclination posture of the test surface 27a with respect to the surface 21a is changed. The XY stage 35 is configured to move the test surface 27a on the XY plane (a plane extending in the X and Y directions), and the test surface 27a generated when the tilt is adjusted by the swivel stages 31 and 33. The positional deviation in the XY plane with respect to the reference plane 21a can be finely adjusted.

  The swivel stages 31 and 33 are configured to be driven by the actuators 32 (only one is shown), and the XY stage 35 is driven by the actuators 36 (only one is shown). Each is driven based on an output signal from 55. Further, the respective rotation centers of the swivel stages 31 and 33 are configured to substantially overlap each other at a substantially central portion of the test surface 27a.

  In addition, the interferometer device 10 includes a photographic lens 43 and an imaging camera 45 for obtaining an image of interference fringes generated by interference between the reference light reflected from the reference surface 21a and the test surface light reflected from the test surface 27a. An imaging lens 39 and a surface sensor 41 for obtaining alignment light images of the reference light and the test surface light, origin interference fringe generation means, origin interference fringe analysis means, inclination angle calculation means, and adjacent interference fringe generation means And a controller 50 including a computer that executes various calculations as fringe analysis calculation means. The above five means are constituted by programs stored in the memory in the computer.

  As shown in FIG. 2, the controller 50 includes a starting interference fringe generation instruction unit 52 for performing a starting interference fringe generation procedure, a starting interference fringe analysis procedure, a tilt angle calculation procedure, and an adjacent interference fringe generation procedure, which will be described later. , A starting interference fringe analysis unit 54, an inclination angle calculation unit 56, an adjacent interference fringe generation instruction unit 58, and a fringe analysis calculation unit 60 that performs calculation as fringe analysis calculation means. Note that the origin interference fringe analysis unit 54, the inclination angle calculation unit 56, and the fringe analysis calculation unit 60 respectively constitute an origin interference fringe analysis unit, an inclination angle calculation unit, and a fringe analysis calculation unit. 52 and the adjacent interference fringe generation instructing unit 58 together with the swivel stages 31 and 33, the actuator 32, and the driver 53 constitute a starting interference fringe generation unit and an adjacent interference fringe generation unit, respectively.

  In the interferometer device 10, the light emitted from the light source 11 is diverged by the magnifying lens 13 and passes through the beam splitters 15 and 17. The divergent light that has passed through the beam splitter 17 enters the collimator lens 19, is converted into parallel light by the collimator lens 19, and is emitted. A part of the parallel light emitted from the collimator lens 19 is retroreflected as reference light on the reference surface 21 a of the reference plate 21, and the remainder passing through the reference plate 21 is irradiated on the test surface 27 a of the subject 27. Is done. The light reflected by the detoured test surface 27a spreads over a wide range. Of the reflected light, the light reflected from a partial region of the test surface 27a passes through the reference plate 21 as the test surface light, and is used as a reference. Along with the reference light reflected from the surface 21 a, the incident light path travels backward, passes through the collimator lens 19, is collected, and enters the beam splitter 17.

  A part of the reference light and the test surface light incident on the beam splitter 17 is reflected at a right angle by the half mirror surface 17 a, and is reflected on the image sensor (CCD) of the imaging camera 45 by the photographing lens 43. An image is formed as an interference fringe image. On the other hand, the remainder of the reference light and test surface light incident on the beam splitter 17 passes through the half mirror surface 17a and reaches the beam splitter 15, and a part thereof is reflected at a right angle by the half mirror surface 15a. 39, the alignment light images of the reference light and the test surface light are formed on the image sensor (CCD) of the surface sensor 41. As described above, in the interferometer device 10, the beam splitter 17, the collimator lens 19, the reference plate 21, the imaging lens 43, the imaging camera 45, and the like constitute an interference optical system, and the beam splitter 15, the collimator lens 19, the reference plate 21, An alignment optical system is configured by the image lens 39, the surface sensor 41, and the like.

  When the test surface 27a is a substantially flat surface, resolvable interference fringes cover substantially the entire surface of the test surface 27a in the image of the test surface 27a formed on the image sensor of the imaging camera 45. Observed. However, when the test surface 27a is curved, a fine interference fringe that cannot be resolved appears in a part of the test surface 27a because the inclination with respect to the reference surface 21a is large. Therefore, in order to obtain the shape of substantially the entire area of the test surface 27a, resolvable interference fringes corresponding to each region of the test surface 27a by sequentially changing the inclination posture of the test surface 27a with respect to the reference surface 21a. Must be obtained sequentially.

  When the test surface 27a is substantially flat, the alignment light image of the test surface light formed on the image sensor of the surface sensor 41 is a point image having a predetermined diameter. However, when the test surface 27a is curved, the test surface light is reflected in various directions depending on the shape of the test surface 27a. Therefore, the test surface light is condensed by the imaging lens 39. However, the alignment light image has a spread corresponding to the inclination angle distribution for each region of the surface 27a to be examined, and is not imaged in the form of dots. Since the reference surface 21a is a flat surface with high accuracy, the alignment light image of the reference light is a point image having a predetermined diameter.

  As will be described in detail later, in the interferometer device 10, resolvable interference fringes corresponding to each region of the test surface 27a can be obtained by sequentially changing the inclination posture of the test surface 27a. The obtained interference fringes for each region of the test surface 27a are subjected to fringe analysis by the controller 50, and the adjacent overlapping portions are joined together using the aperture synthesis method, whereby the shape of the substantially entire surface of the test surface 27a is obtained. Is required. The obtained interference fringe image, alignment light image image, shape analysis result of the test surface 27a, and the like are displayed on the screen of the image display device 57, and the measurement range is specified and the display image is selected. These instructions can be given by an operator via an input device 59 such as a keyboard or a mouse.

<Optical wave interference measurement method of detour surface>
Next, a detour surface lightwave interference measurement method (hereinafter also referred to as “the present embodiment method”) according to an embodiment of the present invention will be described. The main part of the method of this embodiment is composed of a starting interference fringe generation procedure, a starting interference fringe analysis procedure, a tilt angle calculation procedure, and an adjacent interference fringe generation procedure described below.

  FIG. 3 is a diagram illustrating the origin interference fringe generation procedure of the method of the present embodiment in the order of FIGS. 4A to 4D, FIG. 4 is a diagram illustrating an example of the first origin interference fringe image, and FIG. FIG. 6 is a diagram illustrating the starting interference fringe analysis procedure of the method in the order of FIGS. 6A to 6D, and FIG. 6 is a diagram illustrating the tilt angle calculation procedure of the method of the present embodiment. The method of the present embodiment is executed by the interferometer apparatus 10 described above, and the subject 27 has a disc-shaped test surface 27a.

(Starting interference fringe generation procedure)
In this starting point interference fringe generation procedure, the first starting point interference fringe 71 (see FIG. 4) corresponding to the starting point region serving as the starting point of the whole area measurement of the test surface 27a is adjusted by adjusting the inclination posture of the test surface 27a with respect to the reference surface 21a. In the method according to this embodiment, the inclination posture of the test surface 27a is adjusted by the following procedure illustrated in FIG.

  That is, as shown in FIG. 3, on the coordinate system corresponding to the imaging surface of the surface sensor 41, a pixel area whose light intensity exceeding a predetermined threshold is measured as an alignment light area, as shown in FIG. The distribution ranges of the alignment light image 61 of the inspection light and the alignment light image 63 of the reference light are obtained, and a range determination rectangle 65 circumscribing these is set as shown in FIG.

  Next, the range determining rectangle 65 is divided into a plurality of rectangular areas, the ratio of the alignment light image 61 is calculated for each of these areas, and the center of gravity 67 of the alignment light image 61 in the area where the ratio is the maximum. Is obtained ((c) in the figure). Then, based on the positional relationship between the center of gravity 67 and the alignment light image 63 of the reference light, the surface 27a of the test surface 27a with respect to the reference surface 21a required to make the center of gravity 67 substantially overlap the alignment light image 63 of the reference light. Calculate the amount of tilt angle adjustment. These calculations are performed in the origin interference fringe generation instructing unit 52 in the interferometer apparatus 10.

  Next, based on the calculated tilt angle adjustment amount, the tilt posture of the test surface 27a with respect to the reference surface 21a is adjusted so that the center of gravity 67 of the alignment light image 61 substantially overlaps the alignment light image 63 of the reference light. The first starting interference fringe 71 is generated as shown in FIG. In the interferometer apparatus 10, the tilt adjustment is performed by outputting a drive signal from the driver 53 in response to a command from the origin interference fringe generation instruction unit 52 to drive the actuator 32, and the actuator 32 drives the swivel stages 31 and 33. To be executed. When tilt adjustment is performed, a drive signal is output from the driver 55 in response to a command from the controller 50 to drive the actuator 36, and the XY stage 35 is driven by the actuator 36. The positional deviation in the XY plane with respect to the reference surface 21a of the surface 27a is finely adjusted.

(Starting interference fringe analysis procedure)
The starting interference fringe analysis procedure is to obtain the shape of the starting region corresponding to the starting interference fringe 71 on the basis of the starting interference fringe 71. In the method of this embodiment, the starting region is determined by the following procedure illustrated in FIG. Find the shape. It should be noted that which partial region (starting region) of the test surface 27a corresponds to the first starting interference fringe 71 when the first starting interference fringe 71 is imaged. That is, the position information of the starting area is obtained when the first starting interference fringe 71 is imaged, and the tilt angle information of the starting area with respect to the reference plane 21a is obtained by the tilt angle adjustment amount.

  First, the position range of the starting area is determined. In the method of the present embodiment, the imaging magnification of the starting interference fringe 71 is changed in two stages, the position of the center of gravity of the starting area is obtained when the imaging magnification is reduced, and the position range is determined when the imaging magnification is increased. Note that the correspondence between the standard screen area 73 (see FIG. 5) in a state where the imaging magnification is small (for example, 1 time) and the enlarged screen area 75 (see FIG. 5) in a state where the imaging magnification is large (for example, 6 times) is in advance. I ask for it.

  First, fringe scan measurement is performed in a state where the imaging magnification is small, and smoothing processing (for example, averaging filter processing) is performed on the image of the starting interference fringe 71 obtained thereby. Then, the modulation is obtained in the smoothed image, and the center of gravity 79 is obtained for the high modulation region 77 exceeding a predetermined modulation threshold (FIG. 5A).

  Next, the position of the test surface 27 a is adjusted so that the center of gravity 79 substantially overlaps the coordinate position of the standard screen area 73 corresponding to the center 81 of the enlarged screen area 75. In the interferometer apparatus 10, the position adjustment is performed by outputting a drive signal from the driver 55 in response to a command from the origin interference fringe generation instruction unit 52 to drive the actuator 36. The actuator 36 drives the XY stage 35. Is executed.

  After the position adjustment of the test surface 27a is completed, fringe scan measurement is performed with the imaging magnification increased, and the image of the starting interference fringe 71 (FIG. 5 (c)) obtained thereby is smoothed. Then, a modulation is obtained in the smoothed image, and an area that exceeds a predetermined modulation threshold is set as a starting image area 83 (FIG. 5D) corresponding to the starting area, and the starting image area 83 is smoothed. The shape of the starting area is obtained from the image before processing. Thus, by determining the starting image area 83 based on the modulation value, it is possible to reduce high-frequency noise mixed in the image signal of the starting interference fringe 71. In the interferometer apparatus 10, these calculations are performed by the starting interference fringe analyzer 54.

(Tilt angle calculation procedure)
This inclination angle calculation procedure calculates the inclination angle with respect to the reference plane 21a of the adjacent area partially including the peripheral edge of the starting area based on the obtained shape of the starting area. The inclination angle of the adjacent area is obtained by the procedure.

  That is, as shown in FIG. 6, first, the ratio of the origin image area 83 to the enlarged screen area 75 is calculated, and the enlarged screen area 75 is divided into rectangular areas of the number of divisions corresponding to the ratio (for example, If the ratio is 80% or more, it is divided into 4 parts, and if it is 50% to 80%, it is divided into 9 parts, and if it is 10% to 50%, it is divided into 16 parts.

  Next, for each divided area, the ratio of the starting image area 83 occupying each area is obtained, and the area having the maximum ratio is designated as the corresponding area corresponding to the adjacent area. However, if the ratio (for example, 10%) specified in advance is not satisfied in all the areas, the corresponding area is not specified and the measurement in the first enlarged screen area 75 is ended.

  Next, a plane to be fitted to the shape of the starting area included in the corresponding area is obtained by the method of least squares, the inclination angle of this plane (hereinafter referred to as “the least square plane”) is calculated, and this inclination angle is adjacent. The inclination angle of the region with respect to the reference plane 21a is used. In the interferometer apparatus 10, these calculations are performed by the tilt angle calculation unit 56.

(Procedure for generating adjacent fringes)
In this adjacent interference fringe generation procedure, the inclination posture of the test surface 27a with respect to the reference surface 21a is adjusted so that the obtained inclination angle of the adjacent region with respect to the reference surface 21a is approximately 0 degrees, and the adjacent region corresponding to the adjacent region is detected. Interference fringes are generated. In the method of this embodiment, the inclination posture of the test surface 27a with respect to the reference surface 21a is adjusted so that the inclination angle of the least square plane is approximately 0 degrees, and adjacent interference fringes corresponding to the adjacent region are generated.

  In the interferometer apparatus 10, the tilt adjustment is performed by outputting a drive signal from the driver 53 in response to a command from the adjacent interference fringe generation instruction unit 58 to drive the actuator 32, and the actuator 32 drives the swivel stages 31, 33. Is executed by driving. When tilt adjustment is performed, a drive signal is output from the driver 55 in response to a command from the controller 50 to drive the actuator 36, and the XY stage 35 is driven by the actuator 36. The positional deviation in the XY plane with respect to the reference surface 21a of the surface 27a is finely adjusted.

  Thereafter, the above-described adjacent interference fringe analysis procedure, inclination angle calculation procedure and adjacent interference fringe generation procedure are repeated each time the adjacent region is replaced with the next starting point region and the adjacent interference fringes are replaced with the next starting point interference fringes. Thus, the area-specific shapes in the enlarged screen area 75 of the test surface 27a are sequentially obtained. Then, the shapes of the respective regions are connected by the aperture synthesis method to obtain the shape of substantially the entire region in the enlarged screen region 75 (this is the first measurement region) of the test surface 27a.

  In the method of the present embodiment, the obtained area-specific shapes are sequentially connected, and the ratio (for example, 95%) with respect to the size of the enlarged screen area 75 in which the size of the connected area is designated in advance. When it exceeds, the measurement in the enlarged screen area 75 is terminated. In addition, when the obtained shapes by region are sequentially connected, inclination correction is performed based on a difference in inclination angle relative to the reference plane 21a between the connected regions. Further, in the interferometer apparatus 10, calculation related to aperture synthesis is performed in the fringe analysis calculation unit 60.

  Next, the measurement area is moved. In the method of the present embodiment, the measurement region is moved by the following procedure illustrated in FIG. FIG. 7 is a diagram illustrating a method of moving the measurement area.

  First, as shown in FIG. 7, in the standard screen area 73, the position range of the enlarged screen area 75 as the first measurement area is obtained, and the position of the center 81 of the enlarged screen area 75 (see FIG. 5A). To coincide with the center of gravity 79 of the high modulation region 77 shown). Further, in the standard screen area 73, the range of the entire measurement target of the test surface 27a is designated. Here, the range surrounded by the circular outer boundary line 85 and the inner boundary line 87 shown in FIG. 7 is designated as the entire measurement object.

  Next, when a rectangular frame 89 having the same size as the enlarged screen area 75 is moved to a portion adjacent to the enlarged screen area 75 as the first measurement area in the standard screen area 73 shown in FIG. A moving distance necessary to make a part of the rectangular frame 89 overlap the enlarged screen area 75 is obtained. Then, in the standard screen area 73, lattices 91 and 93 (partially omitted in numbering) having the same distance as the moving distance are set vertically and horizontally starting from the position of the center 81, and the intersection 95 of these lattices 91 and 93 is set. (Partial number omitted) is the center of each measurement area.

  Next, the subject 27 is moved to sequentially move from the first measurement region to the adjacent measurement region, and each time the object 27 is moved, the above-described origination interference fringe analysis procedure, inclination angle calculation procedure, and adjacent interference fringe generation procedure are repeatedly performed. Thus, the shape in each measurement region of the test surface 27a is sequentially obtained. Then, these shapes are connected by an aperture synthesis method to obtain the shape of the entire surface to be measured on the test surface 27a.

  When the measurement area is moved, the first interference fringes in the measurement area are obtained by the following procedure. That is, in the measurement region before moving, a portion overlapping with the measurement region after moving is specified, and the inclination angle of the least square plane to be fitted to the shape of this portion is calculated. Then, by adjusting the inclination posture of the test surface 27a with respect to the reference surface 21a so that the inclination angle becomes approximately 0 degrees, the first interference fringes in the measurement area after movement are generated.

  In the embodiment described above, it is assumed that the size of the entire measurement target area of the test surface 27a is larger than the one-time measurable range (the size of the enlarged screen area 75) of the interferometer device 10. When the size of the entire measurement target is smaller than the one-time measurable range, the above-described procedure for moving the measurement range becomes unnecessary.

  Further, although the above-described interferometer apparatus 10 is a Fizeau type, the present invention can also be applied to an equal optical path length type interferometer apparatus such as a Michelson type.

1 is a schematic configuration diagram of an interferometer device for measuring a detour surface according to an embodiment of the present invention. Schematic configuration diagram of the controller shown in FIG. The figure which shows the origin interference fringe generation | occurrence | production procedure which concerns on one Embodiment of this invention method. The figure which illustrates the first origin interference fringe image concerning one embodiment of the method of the present invention The figure which shows the origin interference fringe analysis procedure which concerns on one Embodiment of this invention method The figure which shows the inclination angle calculation procedure which concerns on one Embodiment of this invention method The figure which shows the moving method of the measurement area | region which concerns on one Embodiment of this invention method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Interferometer apparatus 11 Light source 13 Magnifying lens 15, 17 Beam splitter 15a, 17a Half mirror surface 19 Collimator lens 21 Reference plate 21a Reference surface 27 Subject 27a Test surface 29 Placement stage 31, 33 Swivel stage 32, 36 Actuator 35 XY stage 37 Installation board 39 Imaging lens 41 Surface sensor 43 Shooting lens 45 Imaging camera 50 Controller 52 Origination interference fringe generation instruction unit 53, 55 Driver 54 Origination interference fringe analysis unit 56 Inclination angle calculation unit 57 Image display device 58 Adjacent interference fringe Generation instruction unit 59 Input device 60 Stripe analysis calculation unit 61 Alignment light image of test surface light 63 Alignment light image of reference light 65 Rectangle for range determination 67 Center of gravity of alignment light image of test surface light 71 First interference fringe 73 Standard screen area 75 Enlarge Surface area 77 high modulation region 79 high modulation region center 83 the origin image area 85 the intersection of the outer boundary 87 inside the boundary line 89 a rectangular frame 91, 93 grid 95 grid of the center of gravity 81 enlarged screen area

Claims (4)

An interference optical system that obtains an image of interference fringes caused by interference between the reference light reflected from the reference surface and the test surface light reflected from the test surface by irradiating the reference surface and the test surface with measurement light; In an interferometer apparatus that includes an alignment mechanism that adjusts an inclination posture of the test surface with respect to a reference surface, in a detoured surface light wave interference measurement method that obtains a shape of a substantially entire area of the detoured test surface,
After adjusting the inclination posture of the test surface with respect to the reference surface and performing a starting interference fringe generation procedure for generating a first starting interference fringe corresponding to a starting region that is a starting point of the entire area of the test surface,
Origin interference fringe analysis procedure for determining the shape of the origin region based on the origin interference fringes;
An inclination angle calculation procedure for calculating an inclination angle with respect to the reference plane of an adjacent area partially including a peripheral edge of the starting area based on the shape of the starting area;
An adjacent interference fringe that adjusts an inclination posture of the test surface with respect to the reference surface so that an inclination angle of the adjacent region with respect to the reference surface is approximately 0 degrees to generate an adjacent interference fringe corresponding to the adjacent region. The generation procedure
While replacing the adjacent interference fringes with the next starting interference fringes with the adjacent starting fringes, repeatedly performing each time the replacement is performed, and sequentially determining the shape of each area of the test surface, and each of these areas by the aperture synthesis method A method for measuring a light wave interference of a detoured surface, wherein different shapes are connected to obtain a shape of a substantially entire area in a measurement region of the test surface. The interferometer device includes an alignment optical system for obtaining alignment light images of the reference light and the test surface light,
In the origin interference fringe generation procedure,
A distribution range of the alignment light image of the test surface light is obtained on a coordinate system corresponding to the imaging surface of the alignment optical system, and the distribution light is divided into a plurality of areas, and the alignment light image occupies each area. A ratio is calculated, a center of gravity of the alignment light image in an area where the ratio is maximum is obtained, and an inclination posture of the test surface with respect to the reference surface so that the center of gravity substantially overlaps the alignment light image of the reference light The method of claim 1, wherein the first starting interference fringe is generated to adjust the detour surface lightwave interference measurement method.   3. The detour surface lightwave interference measurement method according to claim 1, wherein a smoothing process is performed on the image of the starting interference fringe and the adjacent interference fringe to determine a position range of the interference fringes. An interference optical system for obtaining an image of interference fringes caused by optical interference between the reference light reflected from the reference surface and the test surface light reflected from the test surface by irradiating the reference surface and the test surface with illumination light; In an interferometer apparatus comprising an alignment mechanism that adjusts an inclination posture of the test surface with respect to the reference surface,
Adjusting the inclination posture of the test surface with respect to the reference surface, starting interference fringe generating means for generating a first starting interference fringe corresponding to a starting region serving as a starting point of the whole area measurement of the test surface;
Origin interference fringe analysis means for determining the shape of the origin region based on the origin interference fringes;
An inclination angle calculating means for calculating an inclination angle with respect to the reference plane of an adjacent area partially including a peripheral edge of the starting area based on the shape of the starting area;
An adjacent interference fringe that adjusts an inclination posture of the test surface with respect to the reference surface so that an inclination angle of the adjacent region with respect to the reference surface is approximately 0 degrees to generate an adjacent interference fringe corresponding to the adjacent region. Generating means;
While replacing the adjacent interference fringe with the next starting interference fringe with the adjacent starting area, the processing by the fringe analysis inclination angle calculating means and the adjacent interference fringe generating means is repeatedly performed each time the replacement is performed. And a fringe analysis calculation means for obtaining the shape of the entire surface within the measurement region of the surface to be examined by sequentially obtaining the shape of the surface to be examined and connecting the shapes of the regions by an aperture synthesis method. Interferometer device for detour surface measurement.

Images