JPH01199103A - Apparatus for measuring surface shape - Google Patents

Abstract

PURPOSE:To express the fine uneven shape of a surface to be inspected and to measure a surface shape with high sensitivity and high accuracy, by changing the converging position of an optical probe with respect to the surface to be inspected on the basis of a signal for judging the focus matching state of the optical probe to the surface to be inspected. CONSTITUTION:The focus matching state of an optical probe to the surface to be inspected of an object 30 to be measured is judged by the focus matching state judging optical system of an automatic focus microscope 20 and a fine adjustment motor 17 is driven according to the focus matching state thereof to move the microscope 20 and a focus position is locked to a point to be measured and the object 30 to be measured is revolved around a revolving shaft 21 to perform the scanning of the ridgeline thereof. The distance from the revolving shaft 21 to the point to be measured and an angle of inclination are calculated from the output of the focus matching state judging optical system by a focus state detector 50 and an angle-of-inclination detector 51. The cross-section shape of the object 30 to be measured is measured according to a polar coordinates system by a control computer 60 and a data processing computer 61. Further, the object 30 to be measured is rotated around an indexing shaft 22 to perform multisurface measurement and the surface thereof is measured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a surface shape measuring device, and more particularly to a surface shape measuring device that measures the shape of an aspherical surface such as an aspherical lens at high speed and with high precision.

In particular, the present invention is suitable for projecting a non-contact probe such as an optical probe onto a test surface and measuring the shape of the test surface based on the state of projection of reflected light from the test surface onto a detection sensor. be.

[Prior art]

Conventionally, as a method for measuring the surface shape of an aspherical lens, etc., the object to be measured is moved in an x-y coordinate system, the surface of the object to be measured is scanned with a contact probe, and the shape of the object is determined by the amount of movement of the probe. This method was commonly used.

On the other hand, as a surface shape measurement method using a non-contact probe,
JP-A-61-17907, JP-A-61-1790
As shown in Publication No. 8, a focus state determining optical system and a moving means for focusing this optical system on the surface of the object to be measured are provided, and the surface shape of the object to be measured is determined from the amount of movement of this moving means. There is a way to measure it.

When using the above-mentioned contact type probe to move and scan the object to be measured in the X-Y coordinate system, if the object to be measured is a lens with a large opening angle, the inclination angle of the surface of the object to be measured due to the scanning of the probe It was difficult to measure because of its large size. Another problem has arisen in that a long stroke for length measurement must be taken. There was also the problem that when the object to be measured was scanned with a contact probe, the object to be measured was scratched.

A method using a non-contact type probe such as an optical probe can prevent damage to the object to be measured caused by the above-mentioned method using a contact type probe, and is extremely useful as this type of measurement method.

However, in the conventional measurement method, the shape of the test surface was measured using only the length measuring means, regardless of the type of probe such as contact type or non-contact type. It was impossible to express the shape of the object, and it could not be called a high-resolution measuring device.

Furthermore, measuring devices using non-contact probes are disclosed in the aforementioned Japanese Patent Laid-Open No. 61-17907 and Japanese Patent Laid-open No. 61-17908.
As shown in the publication, it is common to measure the surface shape by determining the amount of movement of the focusing state determining optical system using a length measuring means.

Therefore, the length measurement accuracy depends on the focusing accuracy of the optical probe on the surface to be measured, and if the focusing cannot follow minute irregularities, the measurement accuracy of the surface shape deteriorates.

[Summary of the invention]

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a surface shape measuring device capable of high-resolution and high-accuracy measurement, and capable of expressing the shape of fine irregularities on a surface to be inspected. It is an object.

In order to achieve the above object, the surface shape measuring device according to the present invention includes a focusing state determining means for determining the focusing state of the optical probe on the test surface, and a focusing state determining means for determining the focusing state of the optical probe on the test surface. A control means for changing the focusing position of the optical probe, a detecting means for detecting the amount of change in the focusing position, and a measuring means for measuring the shape of the surface to be inspected using signals obtained from the detecting means and the discriminating means. It is characterized by having

Further features of the present invention will become clear from the following examples.

1 is a schematic configuration diagram showing a shape measuring device for a surface lens and an aspheric lens.

In FIG. 1, a swing bearing 2, an encoder 3, and a swing motor (not shown) are fixed to a surface plate l. An aerostatic bearing system is used between the pivot bearing 2 and the pivot shaft 21 fixed to the R alignment guide 6 for aligning the center of curvature of the lens with the pivot shaft 21. Furthermore, the space between the swing guide 4 fixed to the surface plate 1 and the swing slide 5 fixed to the R alignment guide 6 is also configured by an aerostatic pressure guide system. The rotating shaft 21 is connected to a rotating motor (not shown) by a steel belt (not shown). As described above, a pivot shaft drive mechanism for rotating the R alignment guide 6 around the pivot shaft 21 is configured.

An indexing bearing 8 and an indexing motor 9 are fixed to the R matching slide 7, and the space between the indexing bearing 8 and the indexing shaft 22 is configured by an aerostatic bearing system. The object to be measured 30 such as an aspherical lens is
It is fixed by a chuck indexing shaft 22 (not shown) so that its optical axis coincides with the indexing shaft 22. As described above, the object to be measured 30 for rotating the object to be measured 30 around its optical axis.
configuring the indexing mechanism.

The space between the R alignment guide 6 and the R alignment slide 7 is constructed using an air static pressure guide system, and by sliding the R alignment slide 7 with respect to the R alignment guide 6, the center of curvature of the object to be measured 30 can be rotated. An R alignment mechanism is configured to match the shaft 21. The space between the coarse movement guide 10 fixed to the surface plate l and the coarse movement slide 11 is constructed using an aerostatic pressure guide system. Coarse movement motor 12 and coarse movement slide 1 fixed to coarse movement guide lO
．． 1 and 1 are connected by a screw 12' such as a ball screw or a trapezoidal screw, which is a rotation-to-linear conversion mechanism. A coarse movement grating scale 13 fixed to the coarse movement slide 11 and a grating pitch reading device 14 fixed to the coarse movement guide 10 measure the amount of movement of the coarse movement slide 11 .

The space between the fine movement guide 15 fixed to the coarse movement slide 11 and the fine movement slide 16 is constructed using an aerostatic pressure guide system. A fine movement motor 17 constituted by a linear motor is fixed to the coarse movement slide 11, and its slide portion is fixed to the fine movement slide 16 by fitting the fine movement guide 15 therethrough.

The autofocus microscope 20 is fixed to the fine movement slide 16, and the amount of movement of the autofocus microscope 20 is controlled by the fine movement grating scale 18 fixed to the autofocus microscope 20 and the grating pitch reading device 19 fixed to the coarse movement slide 11. Measure. Further, the surface plate l is fixed to a vibration isolation table (not shown) to eliminate the influence of external vibrations.

FIG. 2 is a schematic configuration diagram showing the internal configuration of the autofocus microscope 20, which is the same as the three-dimensional shape measuring system disclosed by the applicant in Japanese Patent Application Laid-Open No. 17-907-1983.

Therefore, a detailed explanation will be omitted here, and the functions of this optical system will be briefly described.

In the autofocus microscope 20 shown in FIG. 2, the objective lens 41 of the object to be measured 30 is
By detecting the in-focus state of the object and driving the fine movement motor 17 according to the in-focus state to move the autofocus microscope 20, a point where the surface of the object to be measured 30 and the optical axis of the objective lens 41 intersect at all times, That is, an autofocusing mechanism is provided to lock the focal position of the objective lens 41 at the point to be measured. At the same time, the inclination angle of the surface of the object to be measured 30 at the point to be measured is measured by the inclination angle measuring optical system 43.

The inclination angle at this time is measured as the inclination angle around the rotation axis 21 in the direction of rotation indicated by the arrow (θ).

According to this embodiment, the optical probe is projected onto the test surface of the object to be measured 30 by the focusing state discriminating optical system 42 in such a manner that the central ray of the optical probe is inclined with respect to the optical axis. The beam is incident obliquely on the surface to be inspected. This inclination occurs within the plane of the paper in FIG. 2, and the direction of deviation of the reflected beam from the surface to be inspected lies within the plane of the paper.

On the other hand, since the object to be measured 30 is rotated around the rotation axis 21, the optical probe is scanned over the surface of the object to be measured 30 in a direction perpendicular to the plane of the paper.

The object to be measured 30, such as a spherical or aspherical lens, has a constant shape along its circumferential direction, and has an inclination angle in a direction perpendicular to the turning direction shown in FIG. 2 at the measured point on the surface to be measured. is considered to be zero.

Therefore, as shown in FIG. 2, the direction of deviation of the reflected beam of the focusing state determination optical system 42 and the direction of rotation of the object to be measured 30 are configured to be approximately perpendicular, preferably at an angle of 90±20°. By doing so, it is possible to eliminate minute shifts in the reflected beam due to the inclination of the surface to be measured of the object to be measured 30 and interference with the beam for measuring the inclination angle. The height (position) in the optical axis direction can be accurately detected. Therefore, the accuracy of focusing state determination can be significantly improved.

In FIG. 2, in the focusing state determination optical system 42, 80 is a light source, 100 is a collimator lens, 120 is a knife lens, 140 is a polarizing beam splitter, and 160 is a half mirror. - and 1
80 is a 1/4 wavelength plate, 241 is an objective lens, 220 is a band pass filter, 240 is a lens, and 244 is an optical sensor.

In the tilt angle measuring optical system 43, 280 is a light source;
300 and 320 are lenses, 340 is a polarizing beam splitter, 360 is a band pass filter, and 45 is an optical sensor. Furthermore, this optical system 43
In this case, the half mirror 160S1/4 wavelength plate 180 and the objective lens 41 are shared with the optical system 42.

FIG. 3 shows a control system block diagram of the measuring device shown in FIGS. 1 and 2. The output signal of the sensor 44 of the focus state determination optical system 42 installed inside the autofocus microscope 20 is input to the focus state detector 50, and the focus state signal and light amount shown in FIGS. 4 and 5 are obtained. The signal is processed into a signal (see Japanese Patent Laid-Open No. 61-017907). In other words, when the point to be measured on the surface to be measured of the object to be measured 30 is at the focal position of the objective lens 41 in FIG. 2, the in-focus state signal becomes point a in FIG. In accordance with the deviation of the point from the focal position of the objective lens 41, the focus state signal changes linearly near point a. At this time, the light amount signal indicating the total amount of light received by the sensor 44 changes as shown in FIG. Therefore, as can be seen from FIGS. 4 and 5, the in-focus state detectable region is determined when the level of the amount of light received by the sensor 44 exceeds a certain value. .

A focus state signal and a light amount signal generated by the focus state detector 50 are input to a servo driver 52 and a control computer 60. Furthermore, the output of the servo driver 52 is connected to the fine movement motor 17, and the fine movement slide 16. Autofocus microscope 20. Object to be measured 309 Focus Focus state display 0. The servo driver 52 and the fine motor 17 form an autofocusing servo mechanism loop.

The output signal of the sensor 45 of the tilt angle measurement optical system 43 installed inside the autofocus microscope 20 is input to the tilt angle detector 51, and is processed as the tilt angle of the point to be measured in the rotation direction (Japanese Patent Application Laid-Open No. 61-017907).

Further, the tilt angle signal processed by the tilt angle detector 51 is input to the control computer 60.

The output signal of the grating pitch reading device 19 is input to the fine movement slide movement amount detector 53 and is processed as a signal as the movement amount of the fine movement slide 16. Further, the amount of movement of the fine slide 16 is input to the servo driver 52 and the control computer 60. At this time, the fine movement slide 16. Microtremor grating scale 18. Grating pitch reading device 19. Fine slide movement amount detector 53. Servo driver 52. Fine movement motor 17
A positioning servomechanism loop of the autofocus microscope 20 is formed by this.

The coarse motor driver 54 is driven by a command from the control computer 60, and the coarse motor 12 connected to the coarse motor driver 54 rotates, so that the screw 12 is rotated.
' The coarse slide 11 connected to each other moves.

The output signal of the grating pitch reading device 14 fixed to the coarse movement guide IO, which reads the scale of the coarse movement grating scale 13, is input to the coarse movement slide movement amount detector-55, and is output as a signal as the movement amount of the coarse movement slide 11. Processed and controlled computer 6
It is input to 0.

The rotation axis motor driver 56 is driven by a command from the control computer 60, and a rotation motor (not shown) connected to the rotation axis motor driver 56 rotates. At this time, a pivot shaft 21 connected to a pivot motor is rotated by a steel belt (not shown), and the object to be measured 30 is pivoted around the pivot shaft 21 .

The signal from the encoder 3 is input to the rotation angle detector 57, and the rotation angle of the rotation axis 21, that is, the rotation axis 2 of the object to be measured 30 is detected.
The signal is processed as a turning angle θ centered at 1, and is input to the control computer 60.

The index shaft motor driver 58 is driven by a command from the control computer 60, and the index shaft motor 9 connected to the index shaft motor driver 58 rotates.

As a result, the object to be measured 30 is rotated by a certain angle around the indexing axis, and the cross section to be measured is indexed.

The operation panel 59 includes various displays (not shown) such as a focus state display, a light amount display, a tilt angle display, a fine slide movement amount display, a coarse slide movement amount display, and a turning angle display, as well as an autofocusing servo mechanism and an autofocus. Microscope positioning servo mechanism changeover switch, fine slide drive switch, coarse slide drive switch, rotation axis drive switch,
It is equipped with control switches such as an index axis drive switch and a measurement start/stop switch, and is connected to a control computer 60 to provide a man-machine interface.

The control computer 60 is connected to a data processing computer 61, and outputs from the control computer 60 the focus state, inclination angle and fine slide movement amount of the object 30 to be measured,
Measurement data of the coarse slide movement amount and the turning angle are input to the data processing computer 61. Further, measurement condition data for the object to be measured 30, such as the measurement turning range, the number of measurement points, and the turning speed, outputted from the data processing computer 61 are input to the control computer 60.

The above-mentioned measurement data inputted by the data processing computer 61 are processed and converted into shape data of the surface to be measured of the object to be measured 30, and the disk 62. Plotter 63゜Printer 6
It will be output as 4th grade.

Next, a method for measuring the shape of an aspherical lens in this example will be explained below.

FIG. 6 is an explanatory diagram for showing one embodiment of the method of the present invention, showing the measuring mechanism section and the control section in the form of a block diagram.

The measurement mechanism section in FIG. 6 is a top view of FIG. 1 viewed from above. As shown in FIG. 6, this measuring device locks the focal position of the objective lens 41 at the point to be measured on the object to be measured 30 using the above-mentioned autofocusing servo mechanism.
The object to be measured 30 is rotated around the center of curvature (rotation axis 21) of 0, the ridgeline of the object to be measured 30 is scanned, and the object to be measured is determined by the rotation angle θ and the distance r from the rotation axis 21 to the point to be measured. This is a measuring device using a polar coordinate r-θ method for measuring the cross-sectional shape of an object 30.

Furthermore, the object to be measured 30 is rotated around the indexing shaft 22 to perform multi-sectional measurements, and the surface shape of the object to be measured 30 is measured.

First, the fine movement slide 1 is placed in the operating position of a proximity sensor (not shown) provided between the fine movement guide 15 and the fine movement slide 16.
6, and reset the output of the fine slide movement amount detector 53 to O. Further, the coarse movement slide 11 is placed at the operating position of a proximity sensor (not shown) provided between the coarse movement guide lO and the coarse movement slide 11 shown in FIG. 1, and the focal position of the objective lens 41 in this state is The output of the coarse slide movement amount detector 55 is preset so that the distance from the rotation axis 21 is equal to the sum of the output of the fine slide movement amount detector 53 and the output of the coarse slide movement amount detector 55. In other words, it has been calibrated so that the sum of the output of the fine slide movement amount detector 53 and the output of the coarse slide detector 55 is 0 when the focal position of the objective lens 41 coincides with the rotation axis 21. Become.

Next, the axis of the object to be measured 30, that is, the optical axis of the lens and the indexing axis 22.
The object to be measured 30 is fixed to the indexing shaft 22 by a chuck mechanism (not shown) so that the positions coincide with each other.

Next, move the coarse slide 11 and the fine slide so that the sum of the output of the fine slide movement amount detector 53 and the output of the coarse slide movement amount detector 55 becomes the radius of curvature R (design value) of the object to be measured 30. Drive the slide 16. At this time, it is assumed that the fine movement slide 16 is being driven by a positioning servo mechanism. Next, the R alignment slide 7 is driven, and the object to be measured 30 is placed on the autofocus microscope 20 until the in-focus state of the autofocus microscope 20 can be detected as shown in FIGS. 4 and 5.
bring the surface to be measured closer together. In this state, the positioning servomechanism loop is switched to the autofocusing servomechanism loop. As a result, the point to be measured is locked to the approximate focal position of the objective lens 41. Here, the R adjusting slide 7 is driven for fine adjustment so that the sum of the output of the fine slide movement amount detector 53 and the output of the coarse slide movement amount detector 55 becomes the radius of curvature R of the object to be measured 30.

Using the method described above, the measurement origin is set as the center of curvature of the object to be measured 30 such as a lens, and R is set relative to the origin on the center of curvature.
By presetting the object to be measured 30 and the autofocus microscope 20 to form a −θ coordinate system, the conventional
The center of curvature of the object to be measured 30 and the axis of rotation 21 can be easily aligned without considering the wall thickness of the object to be measured 30 as in the measurement method based on the -Y coordinate system.

Furthermore, since the optical probe of the autofocus microscope 20 rotates and scans the curved surface to be measured of the object to be measured 30 to detect irregularities on the surface to be measured, the stroke of the optical probe varies from the aspherical base curved surface (curvature radius R). The length measurement stroke can be shortened.

Furthermore, each mechanism of the measuring device has a simple configuration, and the amount of movement of the drive mechanism is small, making the measuring device compact.

Here, the process of switching from the positioning servomechanism loop of the autofocus microscope 20 to the autofocusing servomechanism loop will be described in detail. When the point to be measured on the surface to be measured of the object to be measured 30 is at the focal point of the objective lens 41, the reflected beam from the point to be measured is centered on the sensor 44 consisting of a CCD or the like of the focusing state determination optical system 42. A spot image is formed (see Japanese Patent Laid-Open No. 61-017907). Therefore, by observing the video signal of the sensor 44 with an oscilloscope monitor (not shown), it is possible to move the point to be measured to a region where the in-focus state can be detected. In other words, the in-focus state detectable area is detected in a state where the video signal of the sensor 44 is present near the center of the sensor 44. In this state, by switching from the positioning servomechanism loop to the autofocusing servomechanism loop using the changeover switch, the point to be measured is automatically locked at the focal position of the objective lens 41.

Next, a turning motor (not shown) is driven to rotate the turning shaft and turn the object to be measured 3o. Thereby, the optical probe of the autofocus microscope 20 scans the ridgeline of the object to be measured 30, and the cross-sectional shape including the lens apex is measured by detecting the reflected beam from the surface to be measured. Furthermore, the indexing shaft 22
The surface shape of the object to be measured 30 is measured radially by driving the object to be measured 30 to rotate the object to be measured 3 degrees around the axis, changing the scanning ridge line, and performing the same measurement.

Now, during measurement as described above, or in any other case, when the fine movement slide 16 is driven by the autofocusing servo mechanism loop, there may be scratches, dust, etc. at the point to be measured, and the optical system for determining the focusing state may When the reflected beam from the measurement point 42 is scattered, the field of view incident on the objective lens 41 is extremely reduced, and the amount of light reaching the sensor 44 is reduced. Therefore, the focus state determination optical system 42
becomes inoperable, the autofocusing servo mechanism loop is cut off, and the fine movement slide 16 becomes inoperable.
control becomes impossible. Therefore, it is predicted that a dangerous situation will occur, such as the autofocus microscope 20 colliding with the object to be measured 3o. Therefore, during measurement, even if the point to be measured becomes free of scratches, dust, etc. due to rotational scanning, the measurement cannot be continued and the measurement is interrupted. In order to cope with these abnormal situations, the following safety measures are taken in the apparatus of this embodiment. In other words, when the fine movement slide 16 is driven by the autofocusing servo mechanism loop, if it deviates from the focus state determination area shown in FIGS. 4 and 5 due to some influence, including scratches or dust, the automatic automatically switches to the positioning servomechanism loop and locks the autofocus microscope 2o in that position. This results in
This prevents the autofocus microscope 2° from colliding with the object to be measured 30. Furthermore, considering the case where the point to be measured passes through scratches, dust, etc. during measurement, as shown in FIG. It is locked to the position just before passing through garbage, etc. Here, the minute scanning range Δθ
, the displacement Δr of the point to be measured in the direction of the indexing axis 22
can be said to be minute. Therefore, even if the autofocusing servo mechanism becomes uncontrollable due to minute scratches, dust, etc., and the positioning servo mechanism is switched to the positioning servo mechanism loop, the surface to be inspected will be in focus again as soon as the scan passes through the scratches, dust, etc. By detecting this and automatically returning to the autofocusing servomechanism loop, the focal position of the objective lens 41 is displaced from C to d, and measurement is continued. The above flowchart is shown in FIG. 8 for reference.

Next, a surface shape data processing method in this embodiment will be explained.

In FIG. 6, according to instructions from the control computer 6o,
The rotating shaft 21 is driven at a constant speed of V¥0, and the object to be measured 30
The ridge line is scanned at a constant speed by the optical probe of the autofocus microscope 2o. At this time, the control computer 6
The turning angle θ is measured by 0. is output and input to A of the comparator 68. Furthermore, the output of the turning angle detector 57 is detected by the comparator 6.
It is input to B of 8.

Here, the measured turning angle θ is set by the control computer 60. and the turning angle θ. When the current value and the current value match, the comparator 68 outputs an A=B signal. Furthermore, according to the A=B signal, a focus state signal that is the output of the focus state detector 50, a fine slide movement amount that is the output of the fine slide movement amount detector 53, and a tilt angle that is the output of the tilt angle detector 51. are latched by latches 65, 66 and 67, respectively.

Each latched data is transmitted to the data processing computer 61 via the control computer 60. By sequentially performing this for a large number of measurement turning angles, data on one cross section of the object to be measured 30 is acquired. These data are processed by the data processing computer 61 and processed into cross-sectional shape data.

Next, a method of processing measurement data into shape data will be explained. As mentioned above, the sum of the output of the fine slide movement amount detector 53 and the output of the coarse slide movement amount detector 55 in the initial state where the focal position of the objective lens 41 and the rotation axis 21 coincide is O. Calibrated. Further, the output of the focus state detector 50 is the amount of deviation of the point to be measured from the focus of the objective lens 41. Therefore, the focus state detector 5
0, the output of the fine slide movement amount detector 53, and the output of the coarse slide movement amount detector 55. It is nothing but the distance r. Furthermore, the object to be measured 30
The aspherical amount δ is determined by setting the radius of curvature to R (generally r at the apex of the object to be measured 30) and performing data processing of δ=R−r. However, since the coarse slide 11 is locked by the air-down method during measurement, the actual r is the sum of the output of the focus state detector 50 and the output of the fine slide movement amount detector 53. The quantity δ is being calculated. At the same time, the inclination angle α of the point to be measured is measured as the output of the inclination angle detector 51, which is the angle α shown in FIG. This is the angle formed with the tangential plane at a point intersecting the optical axis of the spherical objective lens 44 having the same center of curvature.

As a result of the above, the position information of the point to be measured is determined by the index angle (not shown) (rotation angle and turning angle θ of the object to be measured 30 around the index axis 22).
The surface shape data of the object to be measured 30 is constituted by the aspherical amount δ and the inclination angle α as the measured point information. Further, the data processing computer 61 files these onto a disk 62 and outputs the surface shape of the object to be measured 30 to a plotter 63 and printer 64, thereby establishing a man-machine interface.

As described above, when converting measurement data into surface shape data, by using both the output of the focus state detector 50 and the output of the fine slide movement amount detector 53, the device shown in FIG. Even in cases where the mechanism for cutting the probe onto the surface to be inspected is so large that the autofocus servo cannot follow it, it is possible to obtain accurate shape data of the surface to be inspected at all times.

Furthermore, by obtaining the inclination angle data via the inclination angle measurement system as described above, the position and inclination of the measured point on the test surface can be known, and a more detailed surface shape can be expressed.

Now, the scanning form of the optical probe in this measuring device will be explained. Since this measuring device is equipped with a turning means for turning the object to be measured 30 and an indexing means for rotating the object to be measured 30, each scanning shown in FIG. 9, FIG. 10, and FIG. form is possible. Furthermore, Figure 9,
10 and 11 are views of the object to be measured 30 viewed from its apex side, and the center of the circle in each figure is the apex of the object to be measured 30. FIG.

In order to realize the radiation scanning shown in FIG. 9, the indexing shaft 22 is driven as described above so that the direction of the section aa' in FIG. 9 coincides with the turning direction. Next, the section a-a' is scanned while acquiring data for each measured turning angle. Similarly, the indexing shaft 22 is driven so that the direction of the cross section b'-b and the turning direction match, and the cross section b'-b is scanned while acquiring data for each measured turning angle. In this way, each cross section a-a', b'-b, c-c'
, d'-d, ee'.

Data is acquired by scanning eight cross sections f'-f, gg', and h'-h. The number of sampling points at this time is 1000 points/cross section.

Next, the annular scanning shown in FIG. 10 will be explained with reference to FIG. 12. Similar to FIG. 6, the mechanism portion in FIG. 12 is also a view of FIG. 1 viewed from above. The rotating shaft 21 is driven to align the angle between the indexing shaft 22 and the optical axis of the objective lens 41 to nθ. Next, the indexing shaft motor driver 58 is driven by a command from the control computer 60, and the indexing shaft motor 9 is driven at a constant speed. At this time, a signal from a rotary encoder (not shown) installed on the indexing shaft 22 is input to the indexing angle detector 69, and the indexing angle is output as the output of the indexing angle detector 69. Connected to B. Furthermore, the measured index angle is output by the control computer 60 and the comparator 68
is connected to input A of At this time, the A=B signal, that is, the output of the focus state detector 50, the output of the fine slide movement amount detector 53, and the output of the tilt angle detector 51 at the timing when the measured index angle and the current value for index match. are latched, respectively, and the aspherical amount δ and the inclination angle α at the measurement index angle are
It is measured as. A similar measurement is made from the index angle O0 to 360
The measurement of one annular zone is completed by performing the measurement for °. Furthermore, by performing the above-mentioned measurements for the turning angles O1θ, 2θ, .

Next, the spiral scanning shown in FIG. 11 will be explained with reference to FIG. 13. Similar to FIG. 6, the mechanism portion in FIG. 13 is also a view of FIG. 1 viewed from above. The measurement starts from the apex of the object 30 to be measured. First, in response to a command from the control computer 60, the indexing shaft motor driver 58 and the turning shaft motor driver 56 are driven, and the indexing shaft 22 and the turning shaft 21 connected to each driver are respectively driven at a constant speed. At this time, the instrument side exit angle is outputted to the indexing shaft 22 as an installation output, and is connected to the input B of the comparator 68. Furthermore, the measured index angle is outputted by the control computer 60 and connected to input A of the comparator 68. At this time, at the timing when the A=B signal, that is, the measured index angle and the current index angle match, the output of the focus state detector 50 and the fine slide movement amount detector 53
and the output of the inclination angle detector 51 are respectively latched and measured as the aspheric amount δ and the inclination angle α at the measured index angle. By performing similar measurements from the turning angle of 0° to θ, the surface shape of the object to be measured 30 is continuously measured in a spiral manner.

As shown above, by providing the rotating means and the indexing means, it is possible to measure the shape of the entire surface to be measured with a simple mechanism, and it is also possible to measure the scanning form of the optical probe in the desired form. . This not only speeds up and automates measurement, but also increases the degree of freedom in measurement form, making it possible to extract arbitrary surface shape data.

←ii Kakujo→→ FIG. 14 is a schematic configuration diagram showing a second embodiment of the aspheric lens shape measuring device of the present invention. In this example,
The point at which the probe side turns is the first point at which the object to be measured turns.
This is different from the first embodiment shown in the figure.

In FIG. 14, the swing slide 5 is fixed to a coarse movement guide 10, and the R alignment guide 6 is fixed to a surface plate l.

By locking the focal position of the objective lens 41 on the surface of the object to be measured 30 whose center of curvature is on the rotation axis 21 and rotating the entire probe side including the autofocus microscope 20 around the rotation axis 21, the object to be measured 30 is rotated. by scanning the surface of
The surface shape of the object to be measured 30 is measured in the same manner as in the first embodiment.

In the above embodiment, a grating interference method is used as the length measuring means for measuring the respective movement amounts of the fine movement slide 16 and the coarse movement slide 11, but it can also be realized using a laser interference method.

According to the aspherical lens surface shape measuring device of the embodiment shown above, it is possible to measure over a wide area in the measurement range of curvature, aperture angle, aspherical surface amount, etc. Aspherical lens shape measurement using a spot can be performed at high speed. Since the inclination angle of the surface of the object to be measured can be measured at the same time, accurate information regarding the shape of the aspherical lens can be obtained in a short time.

Furthermore, according to this measurement device, there is no need to consider the possibility of scratches, etc., which is seen with the contact probe method, when measuring objects made of various materials such as glass lenses, plastic lenses, and molding dies. .

〔Effect of the invention〕

As described above, the surface shape measuring device according to the present invention utilizes the signal obtained from the focusing state determining means and the signal indicating the amount of change in the focusing position when focusing the light beam on the surface to be inspected. By adding both signals, the distance of the surface to be measured from the reference surface is calculated and the shape of the surface to be tested is determined, so even minute irregularities on the surface to be tested can be detected with high accuracy, providing more detailed surface shape data. can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of a measuring device according to the present invention. FIG. 2 is a schematic diagram showing the inside of the autofocus microscope shown in FIG. 1. FIG. 3 is a control system block diagram of the measuring device shown in FIG. 1. FIG. 4 is an explanatory diagram showing the relationship between the position of the measured point and the focus state signal. FIG. 5 is an explanatory diagram showing the relationship between the position of the measured point and the level of the amount of light received by the sensor. FIG. 6 is an explanatory diagram showing one embodiment of the measuring method of the present invention. FIG. 7 is an explanatory diagram showing the measurement procedure when dust or scratches are present on the surface to be inspected. FIG. 8 is a flowchart showing a method of switching between an autofocusing servomechanism loop and a positioning servomechanism loop. FIGS. 9 to 11 are schematic diagrams showing the scanning form of an optical probe that scans a surface to be inspected. FIG. 12 is an explanatory diagram illustrating a measurement method when scanning in the scanning form shown in FIG. 10. FIG. 13 is an explanatory diagram illustrating a measurement method when scanning in the scanning form shown in FIG. 11. FIG. 14 is a schematic configuration diagram showing another embodiment of the measuring device according to the present invention. l・・・・・・・・・・Surface plate 2・・・・
......Swivel bearing 3...Encoder 4...Swivel guide 5...
・・・・・・・・・Rotating slide 6・・・・・・・・・
...R matching guide 7...R matching slide 8...... Index bearing 9...
......Split shaft motor 10...Coarse movement guide 11...Coarse movement slide 12.
...Coarse motor 12'808. screw
13... Microtremor lattice scale 14...
・・・・・・・・・・・・・・・・・・・・・・・・
......Grating pitch reading device 15...
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・・・・・・・・・・・・Fine movement guide 16・・・・・・
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・・・・・・・・・・・・Fine movement slide 17・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・Fine movement motor 18・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・
......Microlattice scale 19...
・・・・・・・・・・・・・・・・・・・・・・・・
......Grating pitch reading device 20...
・・・・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・Auto focus microscope 30
・・・・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・Object to be measured 41...
・・・・・・・・・・・・・・・・・・・・・・・・
......Objective lens 42...
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......Focus state determination optical system 43...
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・・・・・・・・・・Inclination angle measurement optical system 44,
45・・・・・・・・・・・・・・・・・・・・・・・・
・・・・・・Sensor ai: Aθl te wobbling compound interest fixed point, d upright procedure in the direction of resistance (Method) February 21, 1999

Claims (1)

[Claims] A focusing state determining means for determining a focusing state of the optical probe with respect to the test surface, a control means for changing a focusing position of the optical probe with respect to the testing surface based on a signal from the determining means, and an amount of change in the focusing position. A surface shape measuring device comprising: a detecting means for detecting the detection means; and a measuring means for measuring the shape of the surface to be inspected using signals obtained from the detecting means and the discriminating means.