JP5648903B2 - Shape measuring device, shape measurement control program, and shape measuring method - Google Patents

Description

  The present invention relates to a shape measuring apparatus, a shape measurement control program, and a shape measuring method for optically measuring the shape of an object to be measured. For example, it is possible to precisely measure the shape of an optical element such as a lens or mirror used in a camera, a semiconductor manufacturing apparatus, a telescope, etc., and is particularly suitable for measuring an aspherical shape.

  As a shape measuring device for measuring the shape of an object to be measured, a three-dimensional measuring device using a stylus type touch probe has been widely used. In this method, the height position is measured by bringing the stylus into contact with the measurement surface of the object to be measured, this is measured at multiple points on the measurement surface, and the measurement points are processed by curve fitting or the like. It was configured to measure the shape. In order to eliminate measurement errors due to wear, a relatively hard stylus tip such as an industrial ruby or ceramic is attached to the tip of the stylus. Therefore, when measuring the shape of an optical element such as a lens or a mirror, there is a problem that contact marks may remain on the measurement surface.

  Therefore, instead of a stylus-type touch probe, a measurement head of a laser measuring instrument is mounted, and the return light of the probe light irradiated on the measurement surface of the object to be measured is received and the distance between the measurement head and the measurement surface (measurement) There has been proposed a non-contact type shape measuring apparatus that measures the shape of an object to be measured by measuring the height position of the surface (see, for example, Patent Document 1). Thus, according to the non-contact type shape measuring apparatus that optically measures the shape of the object to be measured, the problem of the contact mark can be solved.

Japanese Patent Laid-Open No. 11-51624

  However, in the conventional non-contact type shape measuring apparatus as described above, there is a problem that it is difficult to eliminate errors associated with the movement of the table or the portal frame for moving the object to be measured and the measuring head together. It was. For example, when the measurement site on the measurement surface for multipoint measurement is a first measurement site, a second measurement site, a third measurement site,..., The measurement site is moved by moving the measured object and the measurement head relative to each other. When the measurement object is moved as follows: first measurement site → second measurement site → third measurement site. In the case where fluctuations (for example, frequency fluctuations) occur in the light, all of the conventional non-contact type shape measuring devices are measured as changes in the height position of the measurement surface and separately detect these errors. Unless it is provided, it was difficult to correct the error accompanying the relative movement.

  The present invention has been made in view of the circumstances as described above, and can eliminate an error associated with movement of a table or the like that moves the object to be measured and the measurement head together, and the shape of the object to be measured can be reduced. An object of the present invention is to provide a shape measuring device capable of measuring with high accuracy, and also to provide a shape measuring control program and a shape measuring method capable of obtaining the same effect.

In order to achieve the above object, a first aspect illustrating the present invention is a shape measuring apparatus. This shape measuring device is a shape measuring device that optically measures the shape of the object to be measured, and the first probe light and the second probe whose irradiation positions are separated from the measurement surface of the object to be measured along the measurement line by a predetermined distance. Probe light irradiation means for irradiating light (for example, the light source unit 21 and the probe light generation unit 22 in the embodiment) and the reflected light of the first and second probe light reflected by the measurement surface are received according to the light receiving position. Reflected light receiving means for outputting the first received light signal and the second received light signal (for example, the light receiving unit 25 in the embodiment), and on the measurement surface based on the first and second received light signals output from the reflected light receiving means. The angle calculation means for calculating the tilt angle of each irradiation position of the first and second probe lights (for example, the calculation unit 53 in the embodiment), the object to be measured, and the first and second probe lights are moved relative to each other. First step on the measurement surface Over Bed light and the second irradiation position moving means for moving the measurement site of the inclination angle by the probe light (e.g., workpiece movement unit 10 in the embodiment, the mirror unit 30, etc.) and, a reference shape of the measurement surface along a measurement line Reference shape storage means (for example, the storage unit 52 in the embodiment) that is set and stored in advance, and angle conversion means (for example, the calculation unit 53 in the embodiment) that converts the reference shape that is set and stored in the reference shape storage means into a reference inclination angle. ) And control means (for example, the control unit 50 in the embodiment) for controlling the operation of the probe light irradiating means, the reflected light receiving means, the angle calculating means, and the irradiation position moving means. The control means sequentially moves the measurement site along the measurement line by the irradiation position moving device to a position spaced apart from the predetermined interval, and performs the measurement based on the reference inclination angle calculated by the angle conversion unit at each measurement site . The operation of the irradiation position moving means is controlled so that the first probe light irradiated to the part is perpendicularly incident on the measurement surface, and the irradiation positions of the first and second probe lights calculated at the first measurement part are inclined. The position where the irradiation position of the first and second probe lights overlaps at the angle and the inclination angle of the irradiation position of the first and second probe lights calculated at the second measurement part adjacent to the first measurement part based on the calculated two inclined angle was, calculates an error component of the tilt angle in the second or first measurement site of the measurement surface along the measurement line by correcting the error component Configured to derive a Jo.

The error component of the tilt angle can be the sum of error components unique to the measurement site .

Further, the control means sequentially calculates the error component of the tilt angle of the other measurement site by setting the error component of the tilt angle of the predetermined measurement site in the plurality of measurement sites along the measurement line as a predetermined value. It can correct | amend and can comprise so that the shape of the measurement surface along a measurement line may be derived | led-out.

  The probe light irradiating means reflects the first and second probe lights emitted from the optical unit provided so as to be swingable about an axis extending horizontally and the first and second probe lights. And the irradiation position moving means moves the work holder in a biaxial direction perpendicular to each other in a horizontal plane. The first and second probe lights emitted from the optical unit by swinging the XY stage to be moved and the mirror provided above the work holder are measured on the measurement surface of the object to be measured held by the work holder. And a scanning mechanism that moves along the line, and the operation of sequentially moving the measurement site along the measurement line is performed by swinging the mirror by the scanning mechanism. There. The irradiation position moving means has a Z stage for moving the work holder up and down, and the control means has optical path lengths of the first and second probe lights emitted from the optical unit and irradiated on the measurement surface. You may comprise so that the action | operation of an irradiation position moving means may be controlled so that it may become substantially the same in a measurement site | part.

  In addition, a rotation mechanism (for example, a θz stage in the embodiment) that relatively rotates the object to be measured and the measurement line about a rotation axis extending vertically, and the object to be measured held by the work holder is rotated around the rotation axis. The shape along the measurement line at an arbitrary turning angle position of the object to be measured may be derived by relative rotation. In this case, the object to be measured held by the work holder by the turning mechanism is relatively rotated around the turning axis at a predetermined angular pitch, and the shape along the measurement lines at a plurality of turning angle positions is measured. It can be configured to derive the shape of the surface.

A second aspect illustrating the present invention is a shape measurement control program. This shape measurement control program is a shape measurement control program executed by the control means in the following shape measurement apparatus. The shape measuring apparatus includes probe light irradiating means for irradiating the first probe light and the second probe light whose irradiation positions are separated from each other along the measurement line on the measurement surface of the object to be measured (for example, the light source unit 21 and Probe light generator 22) and reflected light receiving means for receiving the reflected light of the first and second probe lights reflected by the measurement surface and outputting the first received light signal and the second received light signal according to the received light position ( For example, the angle for calculating the inclination angle of each irradiation position of the first and second probe lights on the measurement surface based on the light receiving unit 25) in the embodiment and the first and second light receiving signals output from the reflected light receiving means. The measurement unit (for example, the calculation unit 53 in the embodiment), the object to be measured, and the first and second probe lights are moved together to move the measurement portion of the tilt angle by the first and second probe lights on the measurement surface. Irradiation position Moving means (e.g., workpiece movement unit 10 in the embodiment, the mirror unit 30, etc.) and the reference shape memory means for previously setting storing reference shape of the measurement surface along a measurement line (for example, the storage unit 52 in the embodiment) , Angle conversion means (for example, the arithmetic unit 53 in the embodiment) that converts the reference shape set and stored in the reference shape storage means to the reference inclination angle, probe light irradiation means, reflected light receiving means, angle calculation means, and irradiation position It comprises control means (for example, control unit 50 in the embodiment) for controlling the operation of the moving means. The shape measurement control program according to the second aspect includes a step of sequentially moving the measurement site along the measurement line by the irradiation position moving unit to a position spaced apart from the predetermined interval, and an angle conversion unit at each measurement site. Based on the reference inclination angle calculated by step (1), the step of causing the first probe light irradiated to the measurement site to be perpendicularly incident on the measurement surface by the irradiation position moving unit, and the first output from the reflected light receiving unit at each measurement site 1, obtaining a second received light signal, calculating an inclination angle of the irradiation position of the first and second probe lights by the angle calculating means from the obtained first and second received light signals, and a first measurement The tilt angle of the irradiation position of the first and second probe lights calculated at the site and the first and second profiles calculated at the second measurement site adjacent to the first measurement site. And a step of obtaining the inclination angle of the irradiation position of the probe light, and two inclination angles calculated for the positions where the irradiation positions of the first and second probe lights overlap in the first and second measurement sites. , Calculating an error component of the tilt angle at the second or first measurement site, and the irradiation position of the first and second probe lights at the second or first measurement site based on the calculated error component And a step of correcting the calculated value of the tilt angle .

The error component of the tilt angle can be the sum of error components specific to each measurement site .

Further, the step of correcting the calculated value of the tilt angle of the irradiation position of the first and second probe light in the second or first measurement site may include the step of correcting a predetermined measurement site in a plurality of measurement sites along the measurement line. By setting the error component of the tilt angle to a predetermined value, the error component of the tilt angle of another measurement site can be calculated and corrected sequentially .

A third aspect illustrating the present invention is a shape measuring method. This shape measuring method is a shape measuring method for optically measuring the shape of the object to be measured, and the measurement surface of the object to be measured by the probe light irradiation means (for example, the light source unit 21 and the probe light generation unit 22 in the embodiment). Are irradiated with the first probe light and the second probe light separated by a predetermined distance along the measurement line, and at this time , the reference shape of the measurement surface along the measurement line is converted into a reference inclination angle, and based on the reference inclination angle. The object to be measured is moved and reflected by the irradiation position moving means (for example, the workpiece moving unit 10 and the mirror unit 30 in the embodiment) so that the first probe light irradiated to the measurement site is perpendicularly incident on the measurement surface. The reflected light of the first and second probe lights reflected by the measurement surface by the light receiving means (for example, the light receiving unit 25 in the embodiment) is received, and the light receiving position is received from the reflected light receiving means. The angle calculation means (for example, the calculation unit 53 in the embodiment) based on the first light reception signal and the second light reception signal output in accordance with the angle of inclination of each irradiation position of the first and second probe lights on the measurement surface The object to be measured and the first and second probe lights are moved relative to each other by the irradiation position moving means, and the measurement site of the inclination angle by the first and second probe lights on the measurement surface is measured along the measurement line. Based on the two inclination angles calculated for the positions where the irradiation positions of the first and second probe lights overlap in the first and second measurement sites, sequentially moved to positions spaced as much as the interval . Alternatively, an error component of the tilt angle at the first measurement site is calculated, and a calculated value of the tilt angle of the irradiation position of the first or second probe light at the second or first measurement site is calculated based on the calculated error component. Supplement To be configured to derive the shape of the measurement surface along the measurement line.

The error component of the tilt angle can be the sum of error components unique to each measurement site .

In addition, the correction of the calculated value of the tilt angle of the irradiation position of the first or second probe light in the second or first measurement site is performed by changing the tilt angle of the predetermined measurement site in the plurality of measurement sites along the measurement line. By setting the error component to a predetermined value, it is possible to sequentially calculate and correct the error component of the tilt angle of another measurement site .

  In this specification, the first and second probe lights before and after the movement overlap when the first and second probe lights are moved along the measurement line at a predetermined distance. Within the range of error, the position area within the error range where the tilt angles measured before and after the movement can be regarded as the same, for example, 0.5d to 2d when the irradiation position interval of the first and second probe lights is d A position separated by a certain degree (preferably a position separated by about 0.8 to 1.2 d) is applicable.

  In the shape measuring apparatus according to the first aspect of the present invention, the control means sequentially moves the measurement site along the measurement line to a position separated by the same distance as the beam interval by the irradiation position moving device, and sets the angle for each measurement site. The calculation means is configured to calculate the tilt angles of the irradiation positions of the first and second probe lights, and to derive the shape of the measurement surface along the measurement line based on the calculated tilt angle information of the plurality of measurement sites. The That is, the movement interval of the measurement site moved along the measurement line by the irradiation position moving means is approximately the same as the interval of the irradiation position along the measurement line of the first and second probe lights, and is measured on the measurement surface. Each time the part is moved, the inclination angle at substantially the same position is sequentially and repeatedly measured by the first probe light and the second probe light, and the shape of the measurement surface along the measurement line based on such inclination angle information Is derived.

  According to the shape measuring apparatus of such an aspect, for example, as described above, the measurement sites on the measurement line of the measurement surface that performs multipoint measurement are the first measurement site, the second measurement site, the third measurement site, and so on. In this case, the measurement head having the probe light irradiating means, the reflected light receiving means, etc. and the object to be measured are moved relative to each other to change the measurement part as follows: first measurement part → second measurement part → third measurement part. When moved, it is possible to detect whether or not the object to be measured has been tilted by a relatively small angle at the second measurement site.

  That is, the inclination angle of the irradiation position of the first and second probe light in the second measurement site is measured by the first and second probe light in the first measurement site and the third measurement site. ing. When the object to be measured is tilted at a relatively small angle at the second measurement site, the tilt angles of the two irradiation positions of the first and second probe lights at the second measurement site are the same in the same direction. It changes by angle. Therefore, the above error components can be eliminated based on the tilt angle information regarding a plurality of measurement sites. Therefore, according to the shape measuring apparatus of the first aspect, with a simple configuration, it is possible to eliminate errors associated with movement of a table or the like that moves the object to be measured and the measurement head together, and the shape of the object to be measured It is possible to provide a shape measuring apparatus capable of measuring the above with high accuracy.

  In the shape measurement control program according to the second aspect of the present invention, the step of sequentially moving the measurement site to a position that is approximately the same as the beam interval along the measurement line, and the first and second probe lights at each measurement site A step of obtaining a light reception signal, a step of calculating an inclination angle of the irradiation position of the first and second probe lights, and a shape of the measurement surface along the measurement line based on the calculated inclination angle information of the plurality of measurement parts And a step of outputting the shape of the measurement surface along the derived measurement line.

  According to the shape measurement control program of such an aspect, the probe light irradiating means and the reflected light receiving means are based on the tilt angle information regarding the plurality of measurement parts, as described for the shape measuring apparatus of the first aspect. It is possible to eliminate an error component that may occur when the measurement head having the above and the object to be measured are moved relative to each other. Therefore, according to the shape measurement control program of the second aspect, it is possible to eliminate an error associated with movement of a table or the like that moves the object to be measured and the measurement head with a simple control configuration. It is possible to provide a shape measuring apparatus capable of measuring the shape of the above with high accuracy.

  In the shape measurement method according to the third aspect of the present invention, the first probe light and the second probe light that are separated from each other by a predetermined distance are irradiated on the object to be measured, and the first and second probe lights reflected by the measurement surface are reflected. The inclination angle of each irradiation position of the first and second probe lights is calculated based on the first and second received light signals that are received according to the light reception position and received, and the inclination by the first and second probe lights is calculated. A plurality of measurements are performed by calculating the tilt angles of the irradiation positions of the first and second probe lights in each measurement part by sequentially moving the measurement part of the angle along the measurement line to a position spaced apart from the predetermined interval. A shape of the measurement surface along the measurement line is derived based on the inclination angle information of the part.

  According to the shape measuring method of such an aspect, an error component that can be generated when the probe light is moved relative to the object to be measured can be eliminated, as in each of the aspects described above. Therefore, according to the shape measuring method of this aspect, with a simple configuration, it is possible to eliminate an error associated with movement of the object to be measured and the probe light, and to accurately measure the shape of the object to be measured. It is possible to provide a shape measuring method capable of being measured.

It is a schematic block diagram of the shape measuring apparatus which illustrates the aspect of this invention. It is a general | schematic block diagram of the control system in the said shape measuring apparatus. It is a schematic diagram which illustrates the movement pattern of probe light. It is a schematic diagram which illustrates the other movement pattern of probe light. It is a schematic block diagram of an optical unit. It is a schematic diagram which illustrates the structure of a reflected light separation element, (a) is a birefringence herving, (b) is a Wollaston prism. It is explanatory drawing for demonstrating the shape of a measurement surface, and the setting of a measurement line. It is another explanatory drawing for demonstrating the shape of a measurement surface, and the setting of a measurement line. It is a schematic diagram which shows the relationship between the 1st, 2nd probe light irradiated to a measurement surface, and the measurement position on a measurement line. It is the table | surface which put together the relationship with the reference | standard inclination angle in each measurement site | part on a measurement line, a measurement inclination angle, the sum total of an error component, and an actual inclination angle. It is a flowchart of the control program of shape measurement. It is a flowchart which shows the detail of step S60 in the said flowchart.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. First, the overall configuration of the shape measuring apparatus will be outlined with reference to FIGS. 1 and 2. FIG. 1 is a schematic configuration diagram of a shape measuring apparatus LMS illustrating an embodiment of the present invention, and FIG. 2 is a schematic block diagram of a control system in the shape measuring apparatus LMS.

  In order to clarify the explanation, a coordinate system composed of an x-axis, a y-axis and a z-axis orthogonal to each other is defined and shown in FIG. Here, the x axis is an axis extending left and right along the paper surface, the y axis is an axis extending front and back through the paper surface, the z axis is an axis extending vertically along the paper surface, the xy plane is a horizontal plane, The z axis corresponds to the vertical axis. For convenience of explanation, the direction along the x axis in the posture shown in FIG. 1 may be referred to as the horizontal direction, the direction along the y axis may be referred to as the front-rear direction, and the direction along the z axis may be referred to as the vertical direction. The method of taking each of the y and z axes is arbitrary, and does not define the position and orientation.

[Outline of shape measuring device]
The shape measuring apparatus LMS is broadly divided into a workpiece moving unit 10 that moves a workpiece (work) W in the x, y, and z axial directions, and a shape measuring probe light PL (first probe light). PL1 and second probe light PL2), a mirror unit 30 that reflects the probe light PL emitted from the optical unit 20 and irradiates the object to be measured, and a workpiece moving unit based on an operator's operation. 10, a control unit 50 that controls the operation of each unit such as the optical unit 20 and the mirror unit 30.

  The workpiece moving unit 10, the optical unit 20, and the mirror unit 30 are installed in an environmental chamber 82 based on a common base frame 81 and managed so that the temperature and humidity are constant at a predetermined value.

  The workpiece moving unit 10 is provided on a surface plate 85 supported by a base frame 81 via a precision vibration isolator 83, and includes a workpiece holder 15 that holds the workpiece W, a surface plate 85, and the workpiece holder 15. The x-stage 11 and the y-stage 12 that are provided in between and move the work holder 15 in the x-axis direction (left-right direction) and the y-axis direction (front-rear direction), respectively, in a horizontal plane are mainly configured. In this configuration, the z stage 13 that moves the work holder 15 in the z-axis direction (vertical direction), and the θz stage (swivel mechanism) that rotates the work holder 15 about the θz axis (swivel axis) extending vertically. The structure provided with 14 is shown. Note that the θz stage may be configured to rotate the mirror unit 30 around a vertical axis perpendicular to the θy axis described later.

  A gate frame 18 is attached to the base frame 81 via a precision vibration isolator 84 so as to straddle the workpiece moving unit 10 from side to side and the upper beam 18 b passes above the workpiece holder 15. The portal frame 18 includes an x sensor 41 for feedback control that detects the position of the work holder 15 in the x-axis direction, the y-axis direction, and the z-axis direction, a y sensor 42 (not shown in FIG. 1), and a z sensor 43. The position detection signals of the work holder 15 detected by the sensors in the x-axis direction, the y-axis direction, and the z-axis direction are input to the control unit 50.

  The θz stage 14 is provided with a θz sensor 44 that detects a turning angle position of the work holder 15, and a position detection signal of the turning angle of the work holder 15 detected by the θz sensor 44 is input to the control unit 50. Has been. As the x sensor 41, the y sensor 42, and the z sensor 43, for example, a length measuring interferometer, a linear scale, or the like can be used. As the θz sensor 44, a linear scale having a curved surface shape or a rotary encoder is used. it can.

  The optical unit 20 is mounted above the leg portion 18a of the portal frame 18, and the probe light PL (PL1, PL2) emitted from the optical unit 20 is in the x-axis direction along the upper beam 18b of the portal frame. Is emitted. Details of the optical unit 20 will be described later.

  The mirror unit 30 is attached to the central portion of the upper beam 18b located immediately above the work holder 15. The mirror unit 30 reflects the probe light PL emitted in the x-axis direction from the optical unit 20 along the upper beam 18 b and irradiates the object W to be measured held by the work holder 15, and the mirror 31. Is configured to include a θy drive mechanism (referred to as a θy stage) 35 that swings around a θy axis (oscillation axis) 33 extending horizontally in the front-rear direction. The θy axis is set so as to pass through the reflecting surface of the mirror 31 (more specifically, the incident position of the probe light).

The mirror unit 30 is provided with a θy sensor 45 for detecting the swing angle position of the θy stage 35 (mirror 31). The position detection signal of the swing angle of the mirror 31 detected by the θy sensor 45 is a control unit. 50 is input. As the θy sensor 45, a linear scale having a curved surface shape, a rotary encoder, or the like can be used.

  The control unit 50 is based on an operation unit 51 in which an operator performs an operation, a storage unit 52 that stores a reference shape or the like of an object to be measured, a calculation unit 53 that performs various calculation processes, and a command signal output from the calculation unit 53. The stage controller 54 for controlling the operation of the stages 11, 12, 13, 14, and 35 of x, y, z, θz, and θy and the optical unit 20 to be described later based on a command signal output from the calculator 53. A measurement control unit 55 for controlling the operation, an I / O unit 56 for inputting / outputting signals to / from the outside, and the like are provided.

  In the profile measuring apparatus LMS configured as described above, the probe light PL emitted from the optical unit 20 is irradiated onto the measurement surface of the object W via the mirror 31, and the reflected light reflected by the measurement surface is reflected. By detecting the light receiving position by receiving light with the light receiving element in the optical unit 20, the inclination angle of the irradiation position irradiated with the probe light PL can be obtained. Then, the operation of each stage is controlled by the control unit 50 to move the probe light PL and the object W to be measured together, and by sequentially moving the irradiation position of the probe light PL, the inclination angle of each part on the measurement surface can be adjusted. The shape of the measurement surface can be derived by calculating the tilt angle data measured at multiple points by a method such as integration processing or fitting processing.

3 and 4 illustrate movement patterns in which the probe light PL and the object W to be measured are moved together to move the probe light irradiation position. Both figures are schematic views of the object to be measured W (W ₁ , W ₂ ) held on the work holder 15 from above, and a measurement line on the measurement surface on which the probe light PL moves (probe light scanning line). ) Are denoted by L _{1 to} L ₃ .

Figure 3 is an example of a preferred movement pattern when measuring a rectangular flat plate shape of the workpiece W _1. In this example, the probe light PL is moved along the measurement line L ₁ by operating the x stage 11 intermittently or continuously from the state in which the probe light PL is irradiated to the start point SP at the upper left end of the measurement surface. , to measure the shape of the measurement surface along the measurement line L ₁ from the tilt angle detected at each measurement point on the measurement line L _1. Next, after moving the workpiece W by actuating the y-stage 12 upward in FIG. 3, by operating the x stage 11 is moved along the probe light to the measurement line L _2, the upper measurement line L ₂ measuring the shape of the measurement surface along the inclination angle detected in the measurement line L ₂ at each measurement point. Similarly, the y stage 12 and the x stage 11 are operated to measure the shape of the measurement surface along the measurement line L ₃ .

Thereby, it is possible to obtain measurement data obtained by measuring the shape of the entire measurement surface of the object to be measured W ₁ in parallel lines. Further, after the above measurement, the object W is rotated by a predetermined angle (for example, 90 degrees) by the θz stage 14 and held at the turning angle position, and the x stage 11 and the y stage 12 are moved along the measurement line again by the alternate movement. By measuring the shape of the measurement surface, measurement data obtained by measuring the shape of the entire measurement surface in a lattice shape can be obtained.

Figure 4 is an example of a preferred movement pattern when measuring a circular plate-shaped object to be measured W _2. In this example, when the x-axis stage 11 is actuated to move the object to be measured W ₂ , or when the θy stage 35 is actuated to move the probe light PL, the probe is moved relative to each other. The y-axis direction position of the workpiece W is aligned by the y stage 12 so that the light PL passes through the center of the circle of the workpiece W.

Then, as shown in FIG. 4A, the x-stage 11 is operated intermittently or continuously from the state in which the probe light PL is irradiated to the start point SP at the left end of the measurement surface, and the probe light PL is measured. is moved along the L _1, the shape of the measurement surface measures a along the measurement line L ₁ from the tilt angle detected at each measurement point on the measurement line L _1. Next, as shown in FIG. 4B, the workpiece W is rotated by a predetermined angle (for example, 2 degrees) by the θz stage 14 and held at the turning angle position, and the x stage 11 is again irradiated with the probe light. It is moved along the measurement line L _2, to measure the shape of the measurement surface along the measurement line L ₂ from the tilt angle detected by the measurement points on the measurement line L _2. Similarly, the θz stage 14 and the x stage 11 are operated to measure the shape of the measurement surface along the measurement line L ₃ .

Accordingly, it is possible to obtain a measurement data shape measurement across the measuring surface radially about the measured object W _2. As for the object to be measured W ₂ , it is possible to measure the shape of the entire measurement surface with a linear or grid-like movement pattern in the same manner as the object to be measured W ₁ described above, and a radial movement pattern for the object to be measured W _1. It is also possible to measure the shape of the entire measurement surface.

[Configuration of optical unit]
Next, the optical unit 20 will be described with reference to FIG. The optical unit 20 includes a light source unit 21 that emits laser light, a probe light generation unit 22 that emits laser light emitted from the light source unit 21 as a plurality of probe lights extending in parallel at a predetermined beam interval, and a probe light generation unit. The light receiving unit 25 that receives the reflected light emitted from 22 and reflected by the measurement surface Ws of the workpiece W is mainly configured. The optical unit 20 corresponds in principle to an autocollimator-type angle measuring device that measures the inclination angle of the measurement surface Ws.

  In the embodiment, the laser light LB generated by the light source unit 21 is divided into two at the probe light generation unit 22 and combined to be emitted in parallel at a predetermined interval and the second probe light. The structure which produced | generated PL2 is illustrated. Moreover, the structure which provided the probe light monitor part 23 which detects the fluctuation | variation of the 1st, 2nd probe light PL1, PL2 produced | generated in the probe light production | generation part 22 in the optical unit 20 is illustrated.

  The light source unit 21 includes a laser light source 211 that generates laser light LB, an isolator 212 that blocks return light from the probe light generation unit 22 side, a shutter 213 that switches on and off the laser light LB generated by the laser light source 211, and the like. It is configured with.

  The laser light source 211 is a laser that stably generates laser light that is stabilized at a predetermined wavelength and has high pointing stability. For example, a DFB (Distributed Feedback) semiconductor laser or a DBR (Distributed Bragg Reflector) semiconductor whose oscillation wavelength is in a visible region. A laser or a He—Ne laser whose frequency is stabilized is preferably used. The laser beam LB emitted from the laser light source 211 is output as linearly polarized light or circularly polarized light whose polarization plane intersects the paper surface at an angle of 45 degrees. The shutter 213 can be configured using an electronic shutter using an EOM (Electro Optic Modulator) or an AOM (Acousto Optic Modulator), or a mechanical shutter that mechanically blocks an optical path.

  The probe light generation unit 22 includes a deflection beam splitter 221 that divides the laser beam LB emitted from the laser beam generation unit 21, a polarization beam splitter 222 that couples the beam, and a half-wave plate provided in each of the divided optical paths. 223, 224, shutters 225, 226, mirrors 227, 228 and the like.

  The polarization beam splitter 221 divides the laser beam LB emitted from the laser beam generation unit 21 into p-polarized laser beam having a polarization plane parallel to the paper surface and s-polarized laser light perpendicular to the paper surface. For example, a p-polarized laser beam having a polarization plane parallel to the paper surface is transmitted and separated into an s-polarized laser beam having a polarization plane perpendicular to the paper surface. The p-polarized laser light and the s-polarized laser light are transmitted through the half-wave plates 223 and 224 provided in the respective optical paths, so that stray light is removed and linearly polarized laser light having a high polarization rate is obtained.

  The polarization beam splitter 222 integrally couples p-polarized laser light and s-polarized laser light, and generates first probe light PL1 and second probe light PL2 that are emitted in parallel at a predetermined interval. For example, by transmitting a p-polarized laser beam and reflecting an s-polarized laser beam, the laser beams of both polarization components are combined together, and the p-polarized first probe light PL1 and the s-polarized second probe light PL2 are combined. Is generated.

  Here, the mirror 228 is provided with a mirror adjustment mechanism 229 capable of adjusting the distance between the first probe light PL1 and the second probe light PL2 by adjusting the position and angle of the mirror 228. The mirror adjustment mechanism 229 adjusts the position of the mirror 228 (the position in the horizontal or vertical direction along the plane of the paper in FIG. 5) and the angle adjustment of adjusting the angular position of the mirror 228 about the axis orthogonal to the plane of the paper. It is constituted by the structure.

  By adjusting the position of the mirror 228 (for example, the position in the left-right direction in FIG. 5) by the mirror adjustment mechanism 229, the incident position of the s-polarized laser light incident on the polarization beam splitter 222 is translated to the left and right. The interval between the first probe light PL1 and the second probe light PL2 can be adjusted. Further, by adjusting the angular position of the mirror 228 by the mirror adjusting mechanism 229, the incident angle of the s-polarized laser light incident on the polarization beam splitter 222 is changed, and the first probe light PL1 and the second probe light PL2 are changed. The degree of parallelism can be adjusted. By combining these, the probe light generation unit 22 can emit the p-polarized first probe light PL1 and the s-polarized second probe light PL2 in parallel at an arbitrary interval.

  The shutters 225 and 226 can be configured using EOM, AOM, or the like, similar to the shutter 213 described above. By providing the shutters 225 and 226, the p-polarized first probe light PL1 and the s-polarized second probe light PL2 can be selectively switched and emitted from the probe light generation unit 22.

  The first probe light PL <b> 1 and the second probe light PL <b> 2 emitted from the probe light generation unit 22 are incident on the beam splitter 251, some are guided to the probe light monitor unit 23, and others are emitted from the optical unit 20.

  The probe light monitor unit 23 includes a beam splitter 231 that divides the introduced first and second probe lights PL1 and PL2 into two parts, and a first detector that detects an interval between the first probe light PL1 and the second probe light PL2. A one beam interval sensor 235 and a second beam interval sensor 236 are provided. The first beam interval sensor 235 is provided close to the beam splitter 231 and detects the beam interval (first beam interval) in a short optical path with a short optical path length from the laser light source 211 to the sensor. On the other hand, the second beam interval sensor 236 is provided apart from the beam splitter 231 and detects a beam interval (second beam interval) in a long optical path having a long optical path length from the laser light source 211 to the sensor.

  Therefore, by monitoring the first beam interval and the second beam interval detected by the first beam interval sensor 235 and the second beam interval sensor 236, fluctuations (fluctuations) in the first and second probe lights PL1 and PL2 are detected. The state can be detected. That is, when the irradiation position of the first and second probe lights PL1 and PL2 is changed, whether the position fluctuation is a parallel shift or an angle change of the first and second probe lights PL1 and PL2, and the shift amount and angle. The amount of change can be detected, and correction can be performed based on this.

  The first probe light PL1 and the second probe light PL2 emitted from the optical unit 20 are applied to the measurement surface Ws of the object W to be measured through a condenser lens (not shown) and the mirror 31 of the mirror unit. At this time, as will be described in detail later, the operation of the stages 11, 12, 13, 14, and 35 of x, y, z, θz, and θy is controlled by the control unit 50, regardless of the measurement site of the measurement surface Ws. The first and second probe lights PL1 and PL2 emitted from the optical unit 20 are controlled so as to be perpendicularly incident on the measurement surface Ws with a substantially constant optical path length.

  The direction in which the first and second probe lights PL1 and PL2 are arranged on the measurement surface Ws, that is, the direction in which the line segment connecting the beam center of the first probe light PL1 and the beam center of the second probe light PL2 extends, It is set along the measurement line that the probe light scans. In the present configuration, the measurement line is in the x-axis direction, and the first and second probe lights PL1 and PL2 emitted side by side in the z-axis direction from the optical unit 20 are reflected by the mirror 31, and on the measurement surface Ws. Irradiated side by side in the x-axis direction.

  The beam interval d of the first and second probe lights PL1 and PL2 on the measurement surface Ws can be appropriately selected according to the curvature of the measurement surface Ws, the target resolution, and the like, and can be set by the mirror adjustment mechanism 229. . For example, when the curvature radius of the measurement surface Ws is larger than 10 m and the target resolution is on the order of nm, the beam interval d of the first and second probe lights PL1 and PL2 on the measurement surface Ws = 10 to 10. About 50 μm is exemplified as a suitable beam interval.

  Reflected light (hereinafter referred to as “first reflected light”) RL1 of the first probe light PL1 specularly reflected by the measurement surface Ws and reflected light (hereinafter referred to as “second reflected light”) RL2 of the second probe light PL2. Returns to the optical unit 20 via the mirror 31, is reflected by the beam splitter 251, and enters the light receiving unit 25.

  The light receiving unit 25 receives the first reflected light RL1 and the second reflected light RL2, and according to the light receiving position of the first reflected light signal LS1 and the second reflected light RL2 according to the light receiving position of the first reflected light RL1. A light receiving element 255 that outputs the second light receiving signal LS2 is provided. The light receiving element 255 can be configured using, for example, a charge coupled device (CCD) or a complementary metal oxide semiconductor image sensor (CMOS). The beam position of the reflected light RL (first reflected light RL1, second reflected light RL2) incident on the light receiving element 255 is obtained by processing an image (pixel signal) of the reflected light RL by a known method.

  In this configuration, the first reflected light RL1 and the second reflected light RL2 are not overlapped by the light receiving element 255 between the beam splitter 251 and the light receiving element 255, that is, the first reflected light RL1 and the second reflected light. A reflected light separation element 253 that separates the first reflected light RL1 and the second reflected light RL2 is provided so that the light RL2 is incident as two independent beams.

  In the present configuration example, the reflected light separation element 253 can be configured by utilizing the difference in polarization characteristics between the first reflected light RL1 and the second reflected light RL2. For example, as shown in FIG. 6A, a birefringence herving 253a using a birefringent material having a refractive index different depending on the polarization direction of the incident light, and as shown in FIG. 6B, the refractive index depends on the polarization direction of the incident light. Can be configured using a Wollaston prism 253b, a lotion prism (not shown), and the like, which are formed by combining birefringent materials having different values.

  Thus, by providing the reflected light separation element 253 that separates the first reflected light RL1 and the second reflected light RL2 between the beam splitter 251 and the light receiving element 255, the first reflected light RL1 and the second reflected light. The position detection accuracy of RL2 can be improved. That is, the beam interval d (for example, 30 μm) of the first and second probe lights PL1 and PL2 on the measurement surface Ws is smaller than the spot size (for example, φ2 mm) of each probe light. Even in the case where the one reflected light RL1 and the second reflected light RL2 form one overlapping dharma beam, it can be separated into two independent circular beams by the reflected light separating element 253. The position detection accuracy of the first and second reflected lights RL1 and RL2 can be greatly improved. Note that the first reflected light RL1 and the second reflected light RL2 may be temporally separated by the shutters 225 and 226 provided in the probe light generation unit 22.

  The first light reception signal LS1 and the second light reception signal LS2 detected by the light receiving element 255 and output from the light receiving element 255 in this way are the positions of the first reflected light RL1 and the second reflected light RL2 that have propagated through a predetermined optical path length. The inclination angle of the irradiation position of the first and second probe lights PL1 and PL2 on the measurement surface Ws can be calculated based on the light reception signals LS1 and LS2. Then, by changing the irradiation position of the first and second probe lights PL1 and PL2 on the measurement surface Ws, the inclination angle of the measurement surface is measured at a plurality of measurement parts, and the measured inclination angle information of each measurement part is integrated. The shape of the measurement surface Ws can be derived by performing the fitting process.

  In the above-described embodiment, the configuration in which one laser beam LB generated by the light source unit 21 is divided into two at the probe light generation unit 22 and combined to generate two probe beams is illustrated. The number of probe lights emitted from 20 may be plural (n (n is a natural number of 2 or more)). For example, one laser beam LB generated by the light source unit 21 may be divided into three or more in the probe light generation unit 22 and combined, and a plurality of laser beams LB emitted from the light source unit 21 (for example, having a polarization state) (N different laser beams or n laser beams having different wavelengths) may be combined in the probe light generation unit 22.

[Control unit configuration]
Next, the configuration of the control unit 50 device will be described in a little more detail with reference to FIG. 2 again. As described in the outline, the control unit 50 includes an operation unit 51 where the operator operates, a storage unit 52 that stores a reference shape of the workpiece W, a calculation unit 53 that performs various calculation processes, and a calculation unit 53. Based on the command signal output from the calculation unit 53 and the stage control unit 54 that controls the operation of the stages 11, 12, 13, 14, and 35 of x, y, z, θz, and θy based on the command signal that is output. And a measurement control unit 55 for controlling the operation of the optical unit 20 and an I / O unit 56 for inputting / outputting signals to / from the outside.

  The operation unit 51 includes a liquid crystal display panel for displaying various images, icons, measurement results, a keyboard for inputting numerical values and character information, a mouse for selecting an icon, various switches such as an on / off switch and a rotary switch. A reader / writer that can read and write the reference shape data and measurement results of the measurement surface Ws recorded on a magnetic recording medium, a USB memory, etc., and the type of the measurement surface Ws (for example, flat surface) , Spherical, aspherical, cylindrical, etc.) and measurement patterns (line, grid, radial, etc.) can be measured.

  The storage unit 52 includes a plurality of storage elements such as ROM and RAM. In the ROM, a control program for controlling the operation of each part of the shape measuring apparatus LMS, a measurement program corresponding to the type and measurement pattern of the workpiece W, and the like are set and stored in advance. The type and measurement pattern of the workpiece W are selected and set in the operation unit 51, and a corresponding measurement program is incorporated into the control program, whereby a shape measuring apparatus suitable for the workpiece W is configured.

  In the RAM, the reference shape (vector data of design values) of the measurement surface Ws of the measurement object read via the reader / writer provided in the operation unit 51 or the I / O unit 56, and the measurement set in the measurement program The reference inclination angle of each probe light irradiation position at the measurement site on the line, the first light reception signal LS1 and the second light reception signal LS2 of each measurement site output from the light receiving element 255 during the execution of the measurement program, and the like are temporarily stored. The

  The arithmetic unit 53 is configured by a CPU, a shift register, and the like, performs various arithmetic processes based on a control program and a measurement program set and stored in advance in the storage unit 52, and instructs the stage control unit 54, the measurement control unit 55, and the like. A signal is output to control the operations of the workpiece moving unit 10, the optical unit 20, and the mirror unit 30.

  The stage control unit 54 drives the x stage 11, y stage 12, z stage 13, θz stage 14, θy stage 35 of the mirror unit 30, etc. based on the command signal output from the calculation unit 53. Is output to control the operation of each stage. Based on the command signal output from the calculation unit 53, the measurement control unit 55 includes the light source unit 21 (laser light source 211, shutter 213) of the optical unit 20 and the probe light generation unit 22 (shutters 225, 226, mirror adjustment mechanism 229). Then, a measurement control signal is output to the light receiving unit 25 (light receiving element 255) or the like to control the shape measurement of the measurement surface Ws.

  The calculation unit 53 outputs the first, second, and second light emitted from the optical unit 20 for each of the stages 11, 12, 13, 14, and 35 of x, y, z, θz, and θy regardless of the measurement site on the measurement surface Ws. Control is performed so that the probe lights PL1 and PL2 are perpendicularly incident on the measurement surface Ws with a substantially constant optical path length.

  Specifically, the following control is executed based on a control program in order to realize a constant optical path length of the probe light and perpendicular incidence to the measurement surface. The computing unit 53 calculates the reference shape (cross-sectional shape) of the measurement surface Ws along the measurement line set by the measurement program from the reference shape of the entire measurement surface Ws set and stored in the storage unit 52. Next, the inclination angle of the measurement point is calculated for the measurement point set on the measurement line in the measurement program.

  Next, from the calculated inclination angles of the respective measurement points, the angle positions of the θz stage 14 (measurement object W) and the θy stage 35 (mirror 31) for allowing the probe light PL to vertically enter the measurement site, and the mirror The coordinate positions of the x stage 11, the y stage 12, and the z stage 13 for setting the distance between 31 to the measurement point to a predetermined value are calculated. Next, a drive signal based on the calculated position of each stage is generated, and a drive signal is output to each of the stages 11, 12, 13, 14, and 35 of x, y, z, θz, and θy to be measured. W and mirror 31 are positioned.

  Then, a measurement control signal for turning on the shutter 211 of the optical unit 20 is output from the measurement control unit 55 to the measured object W, and the first and second probe lights PL1 and PL2 are emitted from the optical unit 20. . Thereby, the first and second probe lights PL1 and PL2 emitted from the optical unit 20 can be perpendicularly incident on the measurement surface Ws with a substantially constant optical path length.

  As the simplest example, when the object to be measured W is a rectangular flat plate, the measurement line is initially set to a parallel line as shown in FIG. 3, and when the object to be measured W is a circular flat plate, the measurement line is As shown in FIG. 4, the initial setting is a radial pattern passing through the center. In these cases, since the measurement surface Ws is a flat surface, the inclination angles of the measurement points set on the measurement line along the x axis are all horizontal. Accordingly, the calculation unit 53 outputs a command signal that causes the reflection surface of the mirror 31 to tilt at 45 degrees in the xz plane to the θy stage 35 and fixes the command signal at the angular position. A command signal for setting the measurement surface Ws to a predetermined coordinate position is output and fixed at the height position. Thereafter, by moving only the x stage 11 at a predetermined interval, the first and second probe lights PL1 and PL2 emitted from the optical unit 20 at each measurement site can be vertically incident with a constant optical path length.

  When the measurement surface Ws of the object to be measured is a spherical shape or aspherical shape having axial symmetry, the measurement line is initially set to a radial shape passing through the central target axis. In this case, as shown in FIG. 7, the diameter of the measurement object is relatively small (within the scanning angle range of the probe light due to the swing of the mirror 31), and the curvature radius r of the measurement surface Ws is relatively small (for example, In the case of a concave spherical shape (about 100 to 500 mm), only the θy stage 35 is operated, and the first and first light emitted from the optical unit 20 at each measurement site on the measurement line along the x-axis. The two probe lights PL1 and PL2 can be incident substantially perpendicularly with a constant optical path length.

  That is, the first and second probe lights PL1 and PL2 enter the central portion along the target axis of the measurement surface Ws at an angular position where the reflection surface of the mirror 31 is inclined 45 degrees downward in the xz plane. By initializing the position of the measurement surface Ws so that the distance between the measurement surface Ws and the curvature radius r coincides with each other, the probe beam is oscillated at a predetermined angle pitch by the θy stage 35 and then the x-axis is obtained. The first and second probe lights PL1 and PL2 can be incident substantially perpendicularly with a constant optical path length at each measurement site on the measurement line along.

  On the other hand, when the radius of curvature r of the measurement surface Ws is relatively large, a convex surface, or an aspheric surface, simply adjusting the angular position of the mirror 31 at each measurement site on the measurement line. It is difficult to make the first and second probe lights PL1 and PL2 vertically incident with a fixed optical path length.

For example, the measurement surface Ws of the object to be measured has an aspherical shape, and as shown in FIG. 8A, the radius of curvature of the measurement part Pwa in the axial center is r ₁ , and the curvatures of the measurement parts Pwb and Pwc in the peripheral part. This is the case when the radius is r ₂ . In this case, the first and second probe lights PL1 and PL2 cannot be vertically incident on the measurement sites Pwb and Pwc only by adjusting the angular position of the mirror 31, and when the inclination angle of the measurement site Pwa is measured. (specifically, the reflection point P ₃₁ of the mirror 31 the distance between the measurement site Pwa) optical path length and the reflection point P of the optical path length (ibid, mirror 31 when measuring the inclination angle of the measurement site Pwb and Pwc The distance between ₃₁ and the measurement site Pwb or Pwc) cannot be made constant.

  In such a case, the calculation unit 53 reads the reference shape of the entire measurement surface Ws preset and stored in the storage unit 52, calculates the reference shape of the measurement surface along the measurement line, and sets it on the measurement line. For the measurement sites Pwa, Pwb, Pwc..., The inclination angle of each measurement point is calculated. Next, for example, with reference to the optical path length when measuring the tilt angle of the measurement site Pwa, as shown in FIG. 8B, the incident angle of the probe light when measuring the tilt angle of the measurement site Pwb (for example, The incident angle of the first probe light, or the crossing angle of the probe optical axis described later) is perpendicular to the measurement surface, and the optical path length is the same as the optical path length when measuring the tilt angle of the measurement site Pwa. The angular position of the θy stage 35 and the coordinate positions of the x stage 11 and the z stage 13 are calculated.

  Then, a drive signal based on the stage position calculated according to each measurement site is output to the x, z, θy stages 11, 13, and 35, and the object to be measured W and the mirror 31 are moved and positioned, thereby optically. The first and second probe lights PL1 and PL2 emitted from the unit 20 can be perpendicularly incident on the measurement surface Ws with a substantially constant optical path length. When the curvature radius r of the measurement surface Ws is relatively large or convex, the first and second probe lights PL1 and PL2 are perpendicularly incident on the measurement surface Ws with a substantially constant optical path length by performing the same processing. Can be made.

  When the probe light is perpendicularly incident on the measurement surface Ws, the stage position can be calculated based on either the first probe light PL1 or the second probe light PL2, and the optical axis of the first probe light PL1. And a virtual probe optical axis passing through the middle of the optical axis of the second probe light PL2 are defined, and the stage position can be calculated so that this probe optical axis intersects the measurement surface Ws perpendicularly. In the case of this configuration, the beam interval between the first probe light and the second probe light is about several tens of μm, and the first probe light and the second probe light are substantially constant in any optical path regardless of which is the reference. Long and perpendicular incidence is possible.

  Strictly speaking, in the former case, the relative inclination angle of the second probe light or the first probe light that is slightly inclined from the normal incidence is added as a correction term. In the latter case, the first probe light and the first probe light are added. For both of the two probe lights, the relative inclination angle of each irradiation position of the first and second probe lights PL1 and PL2 with respect to the inclination angle of the measurement surface where the probe optical axes intersect is added as a normal incidence correction term.

[Inclination angle measurement using two probe lights]
As described above, the first and second probe lights PL1 and PL2 perpendicularly incident on the measurement surface Ws with a constant optical path length are separated by a predetermined distance d along the measurement line L extending in the x-axis direction on the measurement surface. Irradiated. FIG. 9A is a plan view schematically showing the first and second probe lights PL1 and PL2 irradiated on the measurement surface Ws. The two probe lights are combined into one set by driving the stage. The measurement site that moves automatically is formed. In the figure, for convenience, the measurement site is indicated by an ellipse surrounding the first and second probe lights PL1 and PL2.

  In the shape measuring apparatus LMS, as shown in FIG. 9B, on the measurement line L along the x-axis, an interval similar to the beam interval of the first and second probe lights (in this embodiment, the beam interval). Measuring points 1, 2, 3, 4, 5... Are set at the same interval d). And the measurement site | part which consists of 1st, 2nd probe light PL1, PL2 is relatively moved to the position of I, II, III, IV ... sequentially with the movement pitch d, and the inclination of the irradiation position of 1st probe light PL1 in each measurement site | part. The angle and the inclination angle of the irradiation position of the second probe light PL2 are measured.

  Specifically, at the measurement site I, each stage is moved and positioned so that the optical axis length of the probe intersects perpendicularly to the measurement surface and the optical path length becomes a predetermined value, and the first probe light PL1 and the measurement are measured at the measurement point 1. The point 2 is irradiated with the second probe PL2, and the inclination angle of each measurement point is calculated. Next, at the measurement site II, each stage is moved and positioned so that the probe optical axes intersect perpendicularly to the measurement surface and the optical path length becomes a predetermined value, and the first probe light PL1 and the measurement point 3 are measured and held at the measurement point 2, respectively. The tilt angle of each measurement point is calculated by irradiating the second probe light PL2. The same applies to the subsequent measurement sites III, IV.

At this time, the irradiation position of the second probe light PL2 when the measurement site is I and the irradiation position of the first probe light PL1 when the measurement site is II are the same measurement position 2 on the measurement surface. And the irradiation position of the second probe light PL2 when the measurement site is II, and the irradiation position of the second probe light PL2 when the first irradiation position of the probe light PL1 when the measurement site is III, and the measurement site III As for the irradiation position of the first probe light PL1 when the measurement site is IV, the measurement positions on the measurement surface are 3 and 4, respectively, and are the same. That is, in the shape measuring apparatus LMS, the inclination angle at the same measurement position is repeatedly measured by the first probe light PL1 and the second probe light PL2 in accordance with the change of the measurement site.

  Here, as is apparent from the above description, moving the measurement site along the measurement line L means that at least one of the x, y, z, θz, θy stages 11, 12, 13, 14, and 35. This means that the probe light PL (PL1, PL2) and the object to be measured W are relatively moved. Each stage contains an error component that is difficult to remove, and a fine shift or tilt occurs on the measurement surface as the measurement site moves. This error component becomes a unique value for each measurement site I, II, III, IV,.

Now, the ideal inclination angles of the measurement points 1, 2, 3, 4... Calculated by the calculation unit 53 based on the reference shape (design value) of the measurement surface Ws set and stored in the storage unit 52 are k ₁ , k ₂ , k ₃ , k ₄ ..., and the actual inclination angles of the measurement points 1, ₂ , ₃ , ₄ ... on the workpiece W are S ₁ , S ₂ , S ₃ , S ₄ .

Further, for each measurement point 1, 2, 3, 4..., The calculation unit 53 based on the first light reception signal (signal corresponding to the light reception position of the reflected light of the first probe light) LS1 output from the light receiving element 255. The calculated inclination angles of the measurement points 1, 2, 3, 4... Are D ₁₁ , D ₂₁ , D ₃₁ , D ₄₁ ..., And a second light reception signal (a signal corresponding to the light reception position of the reflected light of the second probe light). ) Let the inclination angles of the measurement points 1, 2, 3, 4... Calculated by the calculation unit 53 based on LS2 be D ₁₂ , D ₂₂ , D ₃₂ , D ₄₂ .

Further, let T ₁ , T ₂ , T ₃ , T ₄ ... Be the total sum of error components synchronized with the tilt and the like of each stage at the measurement sites I, II, III, IV.

  At this time, the inclination angle measured by moving the measurement site like I, II, III, IV... N is expressed by the equations shown in FIG.

Here, it is assumed that the sum T _{1 of} error components synchronized with the tilt and the like of each stage in the measurement region I is zero. Then, the arithmetic unit 53 solves the simultaneous equations shown in FIG. 10 and calculates the actual inclination angles S ₁ , S ₂ , S ₃ , S ₄ ... At each measurement point. Specifically, the inclination angles S ₁ , S ₂ , S ₃ , S ₄ ... Of the measurement points are calculated as follows.

First, by setting the total error component T ₁ = 0, the inclination angle between the irradiation position (measurement point 1) of the first probe light PL1 and the irradiation position (measurement point 2) of the second probe light PL2 in the measurement site I is changed. ceremony,
S ₁ = D ₁₁ −k ₁ (1)
S ₂ = D ₂₂ −k ₂ (2)

The expression of the inclination angle between the irradiation position (measurement point 2) of the first probe light PL1 and the irradiation position (measurement point 3) of the second probe light PL2 in the measurement site II is
S ₂ + T ₂ = D ₂₁ −k ₂ (3)
S ₃ + T ₂ = D ₃₂ −k ₃ (4)
Here, the actual inclination angle S ₂ of the measurement point 2 is obtained by the equation (2) and is known. Therefore (3) the sum T ₂ of the error component in the measurement site II from equation is obtained by the following (3) 'equation, a T ₂ determined (4) is substituted into equation T ₂ = D ₂₁ -k ₂ -S ₂ ... (3) '
S ₃ = D ₃₂ −k ₃ −T ₂ (4) ′

Thereafter, the sum T ₃ , T ₄ ... Of the error components is obtained in the same manner, and the inclination angles S ₄ , S ₅ ... Of the respective measurement points are sequentially calculated using the obtained T ₃ , T ₄ . Thus, the actual tilt angles S ₁ , S ₂ , S of the respective measurement points are eliminated by eliminating the influence of the inherent error components that are randomly generated for each measurement site with reference to the sum T ₁ of error components in the measurement site I. ₃ , S ₄ ... Then, based on the calculated inclination angle information of each measurement point, the shape of the measurement surface Ws along the measurement line L is derived.

Specifically, the calculated inclination angles S ₁ , S ₂ , S ₃ , S ₄ ... Of the measurement points ₁ , ₂ , ₃ , ₄ ... Are integrated using the interval d between the measurement points in the calculation unit 53. (The simplest example is trapezoidal integration), and the inclination angle of each measurement point is converted into the shape of the measurement surface Ws. At this time, in order to compensate for the continuity of the fragmented shape for each measurement site, the calculation unit 53 executes reduction of integration error using a function such as spline interpolation. In addition, you may comprise so that it may convert into the shape of the measurement surface Ws by function fitting using a differential Zernike function. According to the function fitting method using the differential Zernike function, an error caused by the integration process can be reduced, and the accuracy of the process of converting the inclination angle into the shape of the measurement surface Ws can be improved.

For simplicity of explanation, the case where the total T ₁ of error components in the measurement site I is assumed to be zero has been described. However, the total T ₁ of error components in the measurement site I is set to a predetermined value other than zero, or an arbitrary The sum of error components at the measurement site may be zero or a predetermined value.

  As described above, the shape measuring apparatus LMS measures the “inclination angle” of each measurement point on the measurement line, and integrates or fits the measured inclination angle of each measurement point along the measurement line. The shape of the measured surface Ws is derived. With this configuration, it is possible to measure with high accuracy a shape that does not have a minute elevation on the measurement surface Ws.

  That is, in the case of a configuration that measures the height of the measurement point (distance between the optical unit and the measurement point), if the resolution of the height measurement is 1 nm, the shape of the measurable measurement surface Ws is Regardless of the measurement point interval d, the height difference is limited to 1 nm or more. On the other hand, according to the present configuration for measuring the tilt angle of the measurement point, the resolution can be improved by changing the distance d between the measurement points, in addition to the fact that the resolution can be improved according to the optical path length by the light lever principle. Can be improved.

  For example, when the difference in height between two measurement points separated by d is = 1 nm, assuming that the inclination angle detected when d = 1 mm is 1 μrad, it is detected when d = 0.1 mm. The tilt angle detected is 10 μrad, and the tilt angle detected when d = 0.01 mm is 100 μrad. Paradoxically, in a system with a resolution of the tilt angle of 1 μrad, it is possible to measure a shape where the height difference of the measurement points is 0.01 nm by setting the distance d of the measurement points to 0.01 mm.

  In the shape measuring apparatus LMS, the first and second probe lights PL1 and PL2 are “perpendicularly incident” on the measurement surface Ws, and the first and second reflected lights RL1 and RL2 reflected by the measurement surface Ws are optical units. 20 light receiving elements 255 are configured to enter. Therefore, a system with a high angular resolution can be constructed using a relatively small light receiving element 255. In addition, it is possible to obtain an effect that it is hardly affected by vibrations of the stage or the like.

  In the shape measuring apparatus LMS, the optical path lengths of the first and second probe lights PL1 and PL2 incident on the measurement surface Ws are controlled to be constant. Therefore, the beam diameters of the first and second probe lights PL1 and PL2 incident on the measurement surface Ws and the first and second reflected lights RL1 and RL2 incident on the light receiving element 255 are constant, and stable shape measurement is possible. It has become.

  Further, the shape measuring apparatus LMS is configured such that the first and second probe lights PL1 and PL2 separated by a distance d in the measurement line direction (x-axis direction) move relative to each other on the measurement line at the movement pitch d. Is done. That is, every time the measurement site moves on the measurement line, the inclination angle of the same measurement point is repeatedly measured by the first and second probe lights PL1 and PL2 at each measurement site. With this configuration, it is possible to surely eliminate error components (tilt, synchronization error, etc.) inherent to each measurement site that occur as a result of stage movement to positioning stop, and to realize highly accurate shape measurement.

[Flow of shape measurement by shape measuring device]
Next, the flow of shape measurement by the shape measuring apparatus LMS will be described. The operator selects the type and measurement pattern of the workpiece W in the operation unit 51 and reads the reference shape data of the measurement surface Ws and stores it in the storage unit 52. Next, “alignment” is selected and executed in the operation unit 51, and the object to be measured held by the work holder 15 is aligned.

  Specifically, the calculation unit 53 follows the measurement surface based on the type and measurement pattern of the workpiece W selected and set in the operation unit 51 and the reference shape of the measurement surface stored in the storage unit 52. The first and second probe lights PL1 and PL2 are roughly scanned to confirm that light can be received by the light receiving element 255, and the position of the workpiece W held by the work holder 15 is calculated. Then, based on the calculated position of the object to be measured, the x, y, z, θz stages 11, 12, 13, 14, etc. are actuated, and for example, the object W to be measured is an aspheric lens having axial symmetry. The position of the workpiece W is adjusted so that the measurement line intersects the central axis. And the to-be-measured object W is moved to the origin position according to a measurement pattern, and alignment processing is completed.

  After completion of the alignment process, when “shape measurement” is selected and started in the operation unit 51, the control unit 50 controls each part of the workpiece moving unit 10, the optical unit 20, and the mirror unit 30 based on the shape measurement control program. To control the shape of the measurement surface Ws. Here, a case where shape measurement is performed along the measurement line described in the section of [Inclination Angle Measurement Using Two Probe Lights] will be described with reference to the flowchart F of the shape measurement control program shown in FIG.

In step S10, a stage position calculation process is performed. With this processing, the x, y, z, θz, and θy stages that allow the probe light to vertically enter the measurement site on the measurement line (referred to as measurement site I in FIG. 9) with a constant optical path length along the x axis. The positions of 11, 12, 13, 14, and 35 are calculated. Specifically, the calculation unit 53 reads the reference shape of the measurement surface Ws set and stored in the storage unit 52, and an ideal inclination angle (“reference inclination angle”) for each measurement point on the measurement line along the x axis. K ₁ and k ₂ are calculated and temporarily stored in the RAM of the storage unit 52. Next, at the measurement points 1 and 2 to be measured, for example, each stage position where the probe optical axis intersects perpendicularly to the measurement surface Ws is calculated at the measurement points 1 and 2 to be measured.

  In step S20, a stage moving process is performed based on the stage position calculated in step S10. Specifically, the calculation unit 53 outputs a command signal corresponding to the stage position calculated in step S10 to the stage control unit 54. The stage control unit 54 outputs a drive signal corresponding to the command signal to each stage, and drives each of the stages 11, 12, 13, 14, and 35 of x, y, z, θz, and θy to measure the object W and the probe. The light is relatively moved and positioned at the measurement site I on the measurement line, and the process proceeds to step S30.

In step S30, the first and second light reception signals are acquired by the optical unit 20. At this time, a command signal is output from the measurement control unit 55 to the optical unit 20, the shutter 213 is opened, and the first probe light PL1 and the second probe light PL2 are irradiated to the measurement point 1 and the measurement point 2 of the measurement site I. The The first reflected light RL1 and the second reflected light RL2 reflected at these measurement points are incident on the light receiving element 255, and the sum of error components specific to the inclinations of the measurement points 1 and 2 and the measurement site I from the light receiving element 255. the first light receiving signal LS1 and the second light receiving signal LS2 containing T ₁ is inputted to the control unit 50 is outputted. Note that the first and second probe lights PL1 and PL2 may be configured to be constantly irradiated onto the measurement surface from the alignment processing stage.

  In step S40, an inclination angle calculation process is performed based on the first and second light reception signals LS1 and LS2 acquired in step S30. The first light receiving signal LS1 and the second light receiving signal LS2 represent the positions of the first reflected light RL1 and the second reflected light RL2 that have propagated through the predetermined optical path length, and are received by vertically incident the first and second probe lights. The amount of deviation of each reflected light from the reference light receiving position in the element 255 represents the amount of deviation from the reference inclination angle of each measurement point.

The calculation unit 53 calculates the tilt angle of each measurement point from the first and second light reception signals LS1 and LS2 based on the conversion coefficient determined by the configuration of the optical unit 20. At this time, the deviation from the normal incidence of the first and second probe lights PL1 and PL2, that is, the inclination angle corrected by the aforementioned normal incidence correction term is calculated. The tilt angle of the measurement point calculated in this way corresponds to the tilt angles D ₁₁ and D ₂₂ described in the section “Measurement of tilt angle with two probe lights”. The calculated tilt angle (referred to as “measurement tilt angle”) is temporarily stored in the RAM of the storage unit 52, and the process proceeds to step S50.

  In step S50, it is determined whether or not the inclination angle has been measured for all measurement points set on the measurement line. For example, when n measurement points are set on the measurement line in the measurement program, whether or not the stage movement process in step S20 has been executed n times, or the tilt angle calculation process in step S40 has been executed n times. Judgment is made based on whether or not it has been done. When it is determined that the tilt angle measurement is not performed for all the measurement points set on the measurement line, the process returns to step S10 and the tilt angle measurement of the next measurement point on the measurement line is performed. When it is determined that the tilt angle measurement has been performed for the point, the process proceeds to step S60.

In step S60, processing for deriving the shape of the measurement surface Ws along the measurement line is performed. Through the steps so far, the RAM of the storage unit 52 performs measurement using the design reference tilt angles k ₁ , k ₂ , k ₃ , k ₄ ..., The first and second probe lights at all measurement points on the measurement line. The tilt angles (D ₁₁ , D ₂₂ ), (D ₂₁ , D ₃₂ ), (D ₃₁ , D ₄₂ )... Are stored. The calculation unit 53 reads the reference inclination angle and the measurement inclination angle, and derives the shape of the measurement surface along the measurement line from the angular distribution of the measurement points on the measurement line. Details of the shape derivation process (step S60) along this measurement line are shown in FIG.

In step S60, the shape derivation process starts with reference inclination angles k ₁ , k ₂ , k ₃ , k ₄ ... And measurement inclination angles (D ₁₁ , D ₂₂ ), (D ₂₁ , D ₃₂ ), A reading process of (D ₃₁ , D ₄₂ ) is performed. In the subsequent step S63, after the processing of the equations (1) and (2) is performed in the arithmetic unit 53, the arithmetic processing of the equations (3) '(4)' is sequentially performed, and the sum of the error components of the measurement sites II, III, IV. T ₂ , T ₃ , T ₄ ... And actual inclination angles S ₁ , S ₂ , S ₃ , S ₄ .

In step S65, the shape of the measurement surface along the measurement line is derived based on the calculated inclination angles S ₁ , S ₂ , S ₃ , S ₄ . Specifically, function fitting using an integration process and a differential Zernike function is applied to discrete inclination angle data S ₁ , S ₂ , S ₃ , S ₄ ... Changing at predetermined intervals d (for example, d = 30 μm). By performing processing, spline interpolation processing, etc., the shape of the measurement surface whose inclination angle changes continuously (smoothly) is derived.

  When the process of deriving the shape of the measurement surface Ws along the measurement line is completed in this way, the calculated shape data of the measurement line (first measurement line) is stored in the storage unit 52 together with the set position of the first measurement line. The data is recorded in the RAM, and the process proceeds to step S70 (FIG. 11).

  In step S70, it is determined whether or not the shape along the measurement line has been derived for all the measurement lines on the measurement surface Ws set by the measurement program. For example, when m measurement lines are set on the measurement surface in the measurement program, whether or not the shape derivation process of the measurement surface along the measurement line in step S60 has been executed m times, or the RAM of the storage unit 52 It is determined by whether or not the shape data of the measurement surface along the m measurement lines is recorded.

  If it is determined that the shape along the measurement line is not derived for all the measurement lines set on the measurement surface, the θz stage is driven to rotate in step S75, and the object to be measured is angled to the next measurement line. The position is positioned, and the process returns to step S10 to perform the shape derivation process along the next measurement line. On the other hand, when it is determined that the shape derivation process along the measurement line has been performed for all the measurement lines, the process proceeds to step S80.

  In step S80, a process for deriving the shape of the entire measurement surface Ws is performed. Specifically, based on radial (parallel line, grid, etc.) shape data derived along each measurement line and recorded in the storage unit 53, the shape of the entire measurement surface Ws (for example, three-dimensional Aspherical shape) is derived. The derived shape data of the entire measurement surface Ws is recorded in the RAM of the storage unit 53, and the process proceeds to step S90.

  In step S90, the shape data of the measurement surface Ws derived in step S80 is output. For example, a three-dimensional image or analysis image of the measurement surface Ws image-processed by an image processing unit (not shown) is displayed on the liquid crystal display panel of the operation unit 51, or externally (for example, a measurement surface) via the I / O unit 56. Output to a printer that prints the shape data, and another computer that processes the data.

  The operator can selectively switch the display information using the operation unit 51, and displays a three-dimensional image of Ws on the measurement surface, the shape of the measurement surface along an arbitrary measurement line, various analysis images, and the like on the liquid crystal display panel. Can be made. Thereby, it is possible to easily grasp the shape of Ws of the measurement surface measured with high accuracy, the position, size, range, etc. of the error region compared with the reference shape (design value).

  As described above, according to the aspect of the present invention, it is possible to eliminate an error associated with movement of a stage or the like that moves the probe light and the object to be measured together, and to increase the shape of the measurement surface of the object to be measured. It is possible to provide a shape measuring means capable of measuring with high accuracy. As examples of objects to be measured that can be measured accurately for the first time by using the present invention, a lens used in an optical system of a projector, a printer scanner lens, a rear projection TV lens, a concentrating solar power generation system Examples thereof include a lens (CVP), a camera lens, a lens used in an optical system of an exposure apparatus, a long mirror, a mirror for emitted light, and a high-precision mold.

10 Work Moving Unit 11 x Stage 12 y Stage 13 z Stage 14 θz Stage 15 Work Holder 20 Optical Unit 21 Light Source (211 Laser Light Source)
22 Probe light generator 25 Light receiver (255 light receiving element)
30 mirror unit 35 θy stage 50 control unit 52 storage unit 53 calculation unit 54 stage control unit 55 measurement control units I, II, III, IV... Measurement site d beam interval F of first and second probe lights on the measurement surface Flowchart L (L _{1 to} L ₃ ) of measurement control program Measurement line LMS shape measuring device LS1 First light reception signal LS2 Second light reception signal PL1 First probe light PL2 Second probe light W (W ₁ , W ₂ ) Object Ws Measurement surface S10 Step S20 for calculating the stage position Step S30 for performing the stage moving process Step S40 for acquiring the first and second received light signals Step S40 for calculating the tilt angle S50 All measurements on the measurement line Step S60 for Determining Whether the Point is Completed Step S6 for Deriving the Shape of the Measurement Surface along the Measurement Line Step S63 for reading out the reference tilt angle and the measured tilt angle Step S63 for calculating the sum of error components at each measurement site and the actual tilt angle at each measurement point Derivation processing of the shape of the measurement surface along the measurement line is performed Step S70 Step S75 for determining whether all measurement lines on the measurement surface are completed Step S80 Position the object to be measured at the angular position of the next measurement line Step S80 Step for deriving the shape of the entire measurement surface S90 Shape data of the measurement surface Step to output

Claims (13)

A shape measuring device for optically measuring the shape of an object to be measured,
A probe light irradiating means for irradiating the first probe light and the second probe light whose irradiation positions are separated by a predetermined distance along the measurement line on the measurement surface of the measurement object;
Reflected light receiving means for receiving reflected light of the first and second probe lights reflected by the measurement surface and outputting a first received light signal and a second received light signal according to the light receiving position;
Angle calculating means for calculating an inclination angle of each irradiation position of the first and second probe lights on the measurement surface based on the first and second light receiving signals output from the reflected light receiving means;
An irradiation position moving means for moving the measurement part of the tilt angle by the first and second probe lights on the measurement surface by moving the measured object and the first and second probe lights together;
Reference shape storage means for presetting and storing a reference shape of the measurement surface along the measurement line;
Angle conversion means for converting the reference shape set and stored in the reference shape storage means into a reference inclination angle;
Control means for controlling the operation of the probe light irradiating means, the reflected light receiving means, the angle calculating means, and the irradiation position moving means,
The control means includes
The irradiation position moving means sequentially moves the measurement site along the measurement line to a position that is approximately the same as the predetermined interval, and based on the reference inclination angle calculated by the angle conversion means at each measurement site . While controlling the operation of the irradiation position moving means so that the first probe light irradiated to the measurement site is perpendicularly incident on the measurement surface,
The inclination angle of the irradiation position of the first and second probe lights calculated at the first measurement site, and the first and second calculated at the second measurement site adjacent to the first measurement site. The tilt angle at the second or first measurement site based on the two tilt angles calculated for the positions at which the first and second probe light irradiation positions overlap at the tilt angle of the two probe light irradiation positions. The shape measuring apparatus is configured to calculate the error component of, and correct the error component to derive the shape of the measurement surface along the measurement line. The shape measuring apparatus according to claim 1 , wherein the error component of the tilt angle is a sum of error components specific to the measurement site . The control means sequentially calculates the error component of the tilt angle of the other measurement site by setting the error component of the tilt angle of the predetermined measurement site in the plurality of measurement sites along the measurement line as a predetermined value. The shape measuring apparatus according to claim 1, wherein the shape measuring apparatus corrects the error. The probe light irradiation means
An optical unit that emits the first and second probe lights, and an object to be measured by reflecting the first and second probe lights that are provided so as to be swingable around a horizontally extending axis and emitted from the optical unit. A mirror for irradiating the measurement surface of
The irradiation position moving means includes
A workpiece holder that holds the object to be measured, an XY stage that moves the workpiece holder in two orthogonal directions in a horizontal plane, and the mirror provided above the workpiece holder is swung to move the workpiece holder. A scanning mechanism for moving the first and second probe lights emitted from the optical unit along the measurement line on the measurement surface of the object to be measured held by the work holder;
The shape measurement according to any one of claims 1 to 3, wherein the operation of sequentially moving the measurement site along the measurement line is performed by swinging the mirror by the scanning mechanism. apparatus. The irradiation position moving means has a Z stage for moving the work holder up and down,
The control means controls the operation of the irradiation position moving means so that the optical path lengths of the first and second probe lights emitted from the optical unit and irradiated on the measurement surface are substantially the same at each measurement site. The shape measuring device according to any one of claims 1 to 4, wherein the shape measuring device is used.   A turning mechanism that relatively turns the object to be measured and the measurement line around a turning axis extending vertically, and relatively turning the object to be measured held by the work holder around the turning axis; The shape measuring apparatus according to claim 1, wherein a shape along a measurement line at an arbitrary turning angle position in the object to be measured can be derived.   By measuring the shape along the measurement lines of a plurality of turning angle positions by relatively rotating the object to be measured held by the turning mechanism at a predetermined angular pitch around the turning axis, The shape measuring apparatus according to claim 6, wherein the shape measuring device is configured to derive a shape of the measurement surface. Probe light irradiating means for irradiating a first probe light and a second probe light whose irradiation positions are separated from each other by a predetermined distance along the measurement line on the measurement surface of the object to be measured, and the first and second reflected by the measurement surface Reflected light receiving means for receiving the reflected light of the probe light and outputting a first received light signal and a second received light signal according to the light receiving position, and the first and second received light signals output from the reflected light receiving means. An angle calculating means for calculating an inclination angle of each irradiation position of the first and second probe lights on the measurement surface, and the object to be measured and the first and second probe lights are moved relative to each other, An irradiation position moving means for moving the measurement part of the inclination angle by the first and second probe lights on the measurement surface; a reference shape storage means for presetting and storing a reference shape of the measurement surface along the measurement line; Reference shape memory means An angle converting means for converting the set stored the reference shape to a reference inclination angle, the probe light irradiating means, the reflected light receiving means, and control means for controlling the operation of the angle calculating means and the irradiation position moving means A shape measurement control program executed by the control means in a shape measuring apparatus comprising:
Sequentially moving the measurement site by the irradiation position moving means to a position spaced apart from the predetermined interval along the measurement line;
In each measurement site, based on the reference tilt angle calculated by the angle conversion unit, the first probe light irradiated to the measurement site by the irradiation position moving unit is perpendicularly incident on the measurement surface;
Obtaining the first and second light receiving signals output from the reflected light receiving means at each measurement site;
Calculating an inclination angle of an irradiation position of the first and second probe lights by the angle calculating means from the acquired first and second light receiving signals;
The tilt angle of the irradiation position of the first and second probe lights calculated at the first measurement site, and the first and second calculated at the second measurement site adjacent to the first measurement site. Obtaining an inclination angle of the irradiation position of the two probe light;
Based on the two tilt angles calculated for the positions where the irradiation positions of the first and second probe lights overlap in the first and second measurement sites, the tilt angle at the second or first measurement site is determined. Calculating an error component;
And a step of correcting the calculated value of the tilt angle of the irradiation position of the first and second probe light at the second or first measurement site based on the calculated error component. Characteristic shape measurement control program. The shape measurement control program according to claim 8, wherein the error component of the tilt angle is a sum of error components specific to each measurement site . The step of correcting the calculated value of the tilt angle of the irradiation position of the first and second probe lights in the second or first measurement site is a predetermined measurement site in the plurality of measurement sites along the measurement line. The shape measurement control program according to claim 8 or 9, wherein an error component of an inclination angle of another measurement region is sequentially calculated and corrected by setting an error component of the inclination angle to a predetermined value . A shape measuring method for optically measuring the shape of an object to be measured,
The probe light irradiating means irradiates the measurement surface of the object to be measured with the first probe light and the second probe light separated by a predetermined distance along the measurement line,
At this time, the reference shape of the measurement surface along the measurement line is converted into a reference inclination angle so that the first probe light irradiated on the measurement site based on the reference inclination angle is perpendicularly incident on the measurement surface. The object to be measured is moved by the irradiation position moving means,
The reflected light receiving means receives the reflected light of the first and second probe lights reflected by the measurement surface, and outputs a first received light signal and a second light output from the reflected light receiving means according to the light receiving position. An inclination angle of each irradiation position of the first and second probe lights on the measurement surface is calculated by an angle calculation unit based on a light reception signal,
By the irradiation position moving means, the object to be measured and the first and second probe lights are moved relative to each other, and the measurement part of the inclination angle by the first and second probe lights on the measurement surface is along the measurement line. To sequentially move to a position spaced apart by the predetermined interval,
The tilt angle of the irradiation position of the first and second probe lights calculated at the first measurement site, and the first and second calculated at the second measurement site adjacent to the first measurement site. 2 Obtain the tilt angle of the irradiation position of the probe light,
Based on the two tilt angles calculated for the positions where the irradiation positions of the first and second probe lights overlap in the first and second measurement sites, the tilt angle at the second or first measurement site is determined. Calculate the error component,
Based on the calculated error component, correcting the calculated value of the tilt angle of the irradiation position of the first and second probe light in the second or first measurement site,
Deriving the shape of the measurement surface along the measurement line. The shape measuring method according to claim 11, wherein the error component of the tilt angle is a total sum of error components unique to each measurement site . Correction of the calculated value of the tilt angle of the irradiation position of the first or second probe light in the second or first measurement site is performed by tilting a predetermined measurement site in the plurality of measurement sites along the measurement line. 13. The shape measuring method according to claim 11 , wherein the angle error component is set to a predetermined value, and the error component of the tilt angle of the other measurement part is sequentially calculated and corrected .

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