JP4307321B2 - Dynamic shape measuring device - Google Patents

Description

The present invention relates to a field of motion performance evaluation of a movable object, for example, a dynamic shape measuring apparatus for obtaining a surface shape of a measured object during displacement such as dynamic shape measurement of a polygon mirror. Relates to the device to perform.

Conventionally, the object to be measured is irradiated with pulsed light in synchronization with the periodic movement of the object to be measured, and the interference fringes obtained by causing interference between the reflected light from the object to be measured and the reference light are time-modulated. A technique for measuring the amount of displacement during movement on the order of nanometers has been proposed (see, for example, Patent Document 1).
In Patent Document 1, the object to be measured is also detected by irradiating the object to be measured with a period slightly different from the movement period of the object to be measured, and detecting the change in the intensity of the interference fringes accompanying the difference between the periods. It is disclosed that the amount of displacement during the movement of the robot is measured on the order of nanometers.
The interference fringes in normal interference measurement are observed when the object to be measured is stationary. However, if the object to be measured moves, the interference fringes disappear and measurement is not possible. By pulsing the light applied to the object, the interference fringes can be observed even when the object to be measured is moving.
In addition, a dynamic measuring method and apparatus for a vibrating object that simultaneously measures the dynamic shape of the resonant mirror and the angle with respect to the resonating base have been studied. This technology uses pulsed light interference and phase shift method or Fourier transform method. Apply and measure.
Moreover, in the dynamic shape measurement of movable objects using the Fourier transform method, the dynamic shape measurement device for movable objects solves the problems of increase in measurement time and decrease in operability due to non-periodic motion components of the object to be measured. And methods have also been studied.
Furthermore, in the dynamic shape measurement of a movable object using the Fourier transform method, the dynamic shape measurement apparatus and method for the movable object for measuring the shape after clarifying the sign (shape unevenness) of the shape of the object to be measured are also provided. It has been studied.
Japanese Patent No. 3150239

FIG. 16 shows an example of a movable object to be measured related to the present invention, which is a polygon mirror used in a writing optical system of an image device such as a laser printer or a digital copier.
The polygon mirror 1 rotates at high speed around the axis 1b, and scans the light beam irradiated from the light source onto the polygon mirror surface (1a in the figure) at high speed. The rotation speed of the polygon mirror is determined according to the writing speed required for the image equipment.
In recent polygon mirrors that require high-speed writing and high-speed rotation, the mirror surface may be deformed due to the influence of heat and centrifugal force accompanying rotation. Since the beam reflected by the deformed surface does not form an image at a predetermined position, there is a demand for accurately measuring and evaluating the surface shape of the polygon mirror during high-speed rotation.
An interferometer can be used to measure the surface shape of a polygon mirror in a stationary state. However, since the interference fringes cannot be observed when the mirror surface rotates, the polygon mirror surface shape during rotation cannot be measured.
As a method capable of measuring the dynamic shape of a movable object such as a polygon mirror on the order of nanometers, there is a measurement device for minute periodic vibration displacement disclosed in Patent Document 1. In this device, a slight difference is given between the period of the signal input to the object to be measured and the period of the signal for causing the light source to emit pulses, and the surface displacement of the object to be measured is used as a beat signal based on the difference between the two periods. It is characterized by measuring.
In the method shown in the reference example of Patent Document 1, surface displacement is captured as still image data by instantaneously generating a light source in synchronization with a signal given to an object to be measured that is displaced according to the signal. Measure with
However, in the above measurement method, since the time width of the pulsed light with respect to the operating speed of the object to be measured is not clarified, interference fringes are generated when the operating speed of the object to be measured becomes faster than the time width of the pulsed light. There is a defect that it becomes impossible to observe.
When an ultrashort pulse light source such as a femtosecond pulse light source is used, interference light can be observed because pulse light with a time width sufficiently shorter than the operating speed of many movable objects can be observed. The time width is used, and an extra cost is required accordingly.
The same applies to the above-described dynamic measurement method and apparatus for a vibrating object, dynamic shape measurement apparatus and method for a movable object, and dynamic shape measurement apparatus and method for a movable object that are currently being studied.

FIG. 17 is a schematic diagram for explaining a minute displacement of the surface to be measured. FIG. 18 is a schematic diagram for explaining a minute displacement of the surface to be measured different from FIG. Even during the light emission time of the light source or the light reception time of the light receiving means, the surface to be measured is slightly displaced, and the manner of displacement varies depending on the timing of starting light emission or light reception.
Specifically, FIG. 17 and FIG. 18 show the difference in displacement. In FIG. 17, the surface to be measured 1 a and the reference axis (for example, the irradiation optical system optical axis) 2, the surface to be measured with respect to the reference axis 2. The displacement amount when 1a becomes vertical (solid line 1a in the figure) is set to zero.
Assuming that the upward displacement (dotted line 1a ′ in FIG. 17) is a positive displacement and the downward displacement (dashed line 1a ″ in FIG. 17) is a negative displacement, The amount of displacement is A.
In FIG. 17, when the measured surface 1a is perpendicular to the reference axis 2 (displacement amount 0), the measured surface 1a is displaced by an equal displacement amount ± A / 2. On the other hand, in FIG. 18, it is displaced by A in the positive direction with respect to the displacement amount 0, and the displacement in the negative direction is zero.
As described above, the method of displacing the surface to be measured with respect to the reference differs depending on the timing at which light emission and light reception are started.
The angle of the surface to be measured with respect to the reference surface affects the interval between the interference fringes, and the most accurate measurement value can be obtained when the interference fringe interval is an integer multiple of the pixels in the means for receiving the interference fringes. Therefore, accurate measurement can always be performed when light emission from the light source or light reception by the light receiving means is started at a timing such that the interference fringe interval becomes an integral multiple of the pixels in the light receiving means.
When the object to be measured is an object that is displaced approximately periodically, light is emitted in synchronization with the displacement period, but if there is an error in the displacement period, that is, if the period fluctuates, it is difficult to perform measurement. Become.
In consideration of the above-described circumstances, the present invention provides a measurement object with a time width such that the amount of displacement of the measurement object during the light emission time of the light source or the light reception time of the light receiving means is less than half of the light source wavelength. By irradiating pulsed light or receiving the interference fringes, an interference fringe reflecting the shape of the object under measurement in operation is acquired, and the shape of the object to be measured is obtained from the acquired interference fringes. Accordingly, an object of the present invention is to provide a dynamic shape measuring apparatus that can reliably measure the dynamic shape of an object to be measured without incurring extra costs.

In order to solve the above-described problem, the invention according to claim 1 is directed to a first light source that irradiates light to the object under displacement, and to irradiate the object to be measured with light from the first light source. An irradiation optical system, timing adjustment means for adjusting the timing of displacement of the object to be measured and light irradiation to the object to be measured, and reflected light from the object to be measured and reference light to interfere with each other Interference optical system, light receiving means for receiving interference fringes by the interference optical system, image forming means for imaging the interference fringes on a light receiving surface, and interference by the interference optical system detected by the light receiving means In a dynamic shape measuring apparatus for determining the surface shape of the object under displacement, comprising a computing unit for determining the surface shape of the object to be measured from fringes, during the light emission time of the light source or the light reception time of the light receiving means The amount of displacement of the object to be measured is the light By half to become such time width or less of the wavelength, the irradiation of the pulsed light to the measurement object, or receives the interference fringes, determine the shape contour of the object to be measured in the displacement from the resulting interference fringes Rutotomoni The light receiving time of the first light source or the light receiving time of the light receiving means with reference to the measured surface angle when the interval between the interference fringes on the light receiving surface of the light receiving means is an integral multiple of the pixels of the light receiving means The dynamic shape measuring apparatus is configured to start light emission of the first light source or light reception of the light receiving means so that the change in angle of the surface to be measured is substantially uniform .

According to a second aspect of the present invention, there is provided a second light source for irradiating the object to be measured to detect an angle of the surface to be measured with respect to the optical axis of the irradiation optical system, and reflected by the object to be measured. The second light receiving means for receiving the light from the second light source and the first light source for producing interference fringes based on the output of the second light receiving means to the light to be measured dynamic shape measurement of the irradiation timing or the first and second operator for calculating a timing for receiving the interference fringe by the light receiving unit, further claim 1, wherein a configuration in which a for receiving interference fringes, Features the device.
According to a third aspect of the present invention, the first light source and the second light source have different wavelengths, and the first light receiving means from the measured object of reflected light from the measured object. The dynamic shape measuring apparatus according to claim 2, wherein a band-pass filter that cuts light other than light having a wavelength close to that of the first light source is provided in the optical path .
According to a fourth aspect of the present invention, the first light source and the second light source have different polarization directions, and the measurement object is in the optical path of the reflected light from the measurement object. The dynamic shape measuring apparatus according to claim 2 , wherein a polarizing filter that cuts light other than light close to a polarization direction of the first light source is provided in a portion between the first light receiving unit and the first light receiving unit .
According to a fifth aspect of the present invention, the timing adjustment means for the displacement of the object to be measured and the irradiation of light to the object to be measured is installed in the optical path from the first light source to the object to be measured. wherein the dynamic shape measuring apparatus according to claim 1, wherein using the delay optical system.
The invention described in claim 6 is characterized in that the dynamic shape measuring apparatus according to claim 5 uses an optical fiber for the delay optical system.

  According to the present invention, the time width of light emission of the light source is set in accordance with the displacement speed of the object to be measured so that the amount of displacement of the object to be measured within the light emission time of the light source is equal to or less than half of the light source wavelength. This makes it possible to clarify the time width of the required pulsed light with respect to the operating speed of the object to be measured, thereby making it possible to reliably observe interference fringes and measure the dynamic shape contour without incurring extra costs. be able to.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of a first embodiment of a dynamic shape measuring apparatus according to the present invention. In FIG. 1, a polygon mirror 1 which is an object to be measured is rotated by a driver 4 in response to a pulse signal having a predetermined frequency from a pulse generator 3.
A semiconductor laser 5, which is a light source (first light source) that emits pulsed light having a predetermined pulse width, inputs a signal from the pulse generator 3 to the laser driver 6 as an external trigger, and emits light at a predetermined emission frequency. An ND filter 7 and a beam expander 8 for adjusting the intensity of light from the semiconductor laser 5 are provided.
A part of the light expanded by the beam expander 8 passes through the beam splitter 9 and a part thereof is reflected by the beam splitter 9. The light that has passed through the beam splitter 9 is applied to the polygon mirror 1 that is the object to be measured.
The light reflected by the polygon mirror (object to be measured) 1 travels back along the incoming optical path, is reflected by the beam splitter 9, and reaches the CCD camera 11 via the imaging lens 10.
On the other hand, the light reflected by the beam splitter 9 is applied to the reference mirror 12, and the light reflected by the reference mirror 12 travels back through the optical path that has arrived, passes through the beam splitter 9, and forms the imaging lens 10. To the CCD 11 via

For the object light reflected by the polygon mirror 1 and the reference light reflected by the reference mirror 12, the difference between the optical path length of the object light and the optical path length of the reference light is used as a light source semiconductor laser (first light source) 5 If the optical axes of the object beam and the reference beam are substantially coincided with each other, they cause interference and generate interference fringes.
The position of the imaging lens 10 is adjusted so that the image of the DUT 1 is formed on the imaging surface of the CCD camera 11. Interference fringes generated between the object light and the reference light are imaged by the CCD camera 11.
The interference fringes are captured by the frame grabber 13, transferred to the computer 14, stored in the memory of the computer 14, and displayed on the computer monitor. Reference numeral 15 denotes a CCD driver.
In order to obtain the polygon mirror surface shape contour from the interference fringes picked up by the CCD camera 11, for example, a predetermined amount of inclination is given between the polygon mirror surface and the reference mirror surface to spatially modulate the interference fringes. An arithmetic unit (not shown) that executes the Fourier transform method is used.
Alternatively, a piezo actuator for finely moving the reference mirror 12 in the direction of the optical axis may be attached to the reference mirror 12, and an arithmetic unit (not shown) that performs phase modulation by time-modulating the interference fringes may be used. .

FIG. 2 is a diagram showing the timing of the pulse voltage signal supplied to the polygon mirror driver and the pulse voltage signal supplied to the semiconductor laser driver. By supplying a signal to both drivers from the common pulse generator 3, the rotation of the polygon mirror 1 and the light emission of the semiconductor laser 5 can be synchronized.
When signals are supplied to the respective drivers from different channels of the same pulse generator 3, the frequency of the signal for the semiconductor laser is made to coincide with the frequency of the signal for the polygon mirror, or set to a divisor, and the signal between the channels is If the phase is adjusted, the timing can be adjusted after synchronization between the rotation and the light emission.
By adjusting the timing of the signal, the angle of the polygon mirror surface with respect to the optical axis of the measurement optical system at the moment when the polygon mirror 1 is irradiated with light can be adjusted, so that the polygon mirror surface is substantially perpendicular to the optical axis of the measurement optical system. by adjusting the timing of the signal as a reflected light and the reference light interference fringe Shi may cause interference occurs from the polygon mirror 1 can image the interference pattern at the CCD camera 11.
When the emission frequency of the semiconductor laser 5 is lower than the imaging frequency of the CCD camera 11, a signal having the same frequency synchronized with the supply signal to the semiconductor laser driver 6 is supplied to the CCD driver 15 and the frame grabber 13 to trigger an external trigger. In this case, the timing is adjusted so that the semiconductor laser 5 emits light during the exposure time of the CCD camera 11.
When the emission frequency of the semiconductor laser 5 is higher than the imaging frequency of the CCD camera 11, the imaging may be performed in synchronization with the CCD camera 11. In this case, the emission frequency of the semiconductor laser 5 is divided by the imaging frequency of the CCD camera 11. As a result, an averaged intensity image is obtained as many times as the quotient.
Regarding the time width of light emission of the semiconductor laser 5 and the rotation speed of the polygon mirror 1, assuming that the displacement speed in the optical axis direction of the polygon mirror surface accompanying the rotation is V (x) and the light emission time width is t, light emission During the time, the polygon mirror surface is displaced by V (x) · t in the optical system optical axis direction.
x represents the position in the longitudinal direction of the polygon mirror surface, where the center of the polygon mirror surface is 0 and the extreme end of the mirror surface is ± xmax, V (0) is zero and V (± xmax) is the maximum. Become.

FIG. 3 is a schematic diagram showing interference fringes obtained when the time width of light emission of the semiconductor laser is sufficiently shorter than the displacement speed of the polygon mirror surface in the optical system optical axis direction. FIG. 4 is a schematic diagram showing an interference fringe image obtained when the light emission time width is not sufficiently short with respect to the displacement speed.
3 and 4, on the monitor screen represented by reference numeral 16, 1a is a mirror surface similar to that in FIG. 16, 1b is a rotation axis, and 1d is an interference fringe. In FIG. 4, interference fringes are observed in a region where the displacement speed in the optical axis direction near the center on the polygon mirror surface is small.
However, the displacement speed increases as approaching the end in the longitudinal direction of the polygon mirror surface, and accordingly, the contrast of the interference fringe 1d is lowered (see 1d ′), and it becomes impossible to observe normally. If the interference fringes cannot be observed normally, the shape contour cannot be obtained.
FIG. 5 is a diagram showing a simulation example of the cross-sectional intensity distribution in the longitudinal direction of the polygon mirror of the interference fringes obtained when the polygon mirror surface is substantially perpendicular to the optical axis of the optical system. FIG. 6 is a diagram showing a simulation example of the cross-sectional intensity distribution when the angle is slightly deviated from 90 degrees.
Since the polygon mirror 1 changes the angle with respect to the optical axis of the optical system during rotation, the synthesis of the interference fringes during the semiconductor laser emission time when the polygon mirror surface is nearly perpendicular to the optical axis of the optical system is observed as an interference fringe image. Will be.
FIG. 7 is a diagram showing a simulation example of the cross-sectional intensity distribution of the synthetic interference fringes during the semiconductor laser emission time. FIG. 8 is a diagram showing a simulation example of the cross-sectional intensity distribution of the synthetic interference fringe when the displacement of the polygon mirror surface during the light source emission time is smaller than half of the light source wavelength at the end portion in the longitudinal direction of the polygon mirror.

FIG. 9 is a diagram showing a simulation example of the sectional intensity distribution of the synthetic interference fringes when the displacement of the polygon mirror surface during the semiconductor laser emission time is larger than half of the light source wavelength.
However, the contrast of the interference fringes is lost when the displacement of the polygon mirror surface during the semiconductor laser emission time becomes larger than half the wavelength of the semiconductor laser 5 as in the end portion of the polygon mirror 1 in FIG.
Therefore, the maximum speed Vmax is obtained from the specifications of the polygon mirror 1, and a semiconductor laser having a pulse emission time width that satisfies the following equation (1) may be used as the light source.
Vmax · t <λ / 2 (1)
A light source other than a semiconductor laser that emits pulsed light may be used, or a CW light such as a He-Ne laser is used as a light source, which is modulated by an external pulse modulator such as a rotating chopper for a predetermined time. You may obtain the pulsed light of width.
Further, by using a CW light source and adjusting the exposure time of the CCD camera, the same effect as adjusting the pulse emission time width of the light source may be obtained. In that case, t in equation (1) corresponds to the exposure time of the CCD camera.
In the measurement method in which interference fringes that are spatially modulated as in the Fourier transform method are recorded as a one-shot image and the shape of the DUT 1 is determined, the interval between the interference fringes is an integral multiple of the pixels of the light receiving means such as a CCD camera. Sometimes the most accurate measurement is obtained. For example, a more accurate measurement result can be obtained when one interference fringe is observed per 3.5 pixels than when one interference fringe is observed per 3.5 pixels.

FIG. 10 is a diagram showing a simulation example of the longitudinal sectional shape of the polygon mirror obtained when the interference fringe interval is an integral multiple of the pixel. FIG. 11 is a diagram showing a simulation example of the shape obtained when the interference fringe interval is not an integer multiple of the pixel.
However, a measurement error occurs in FIG. 11 with respect to FIG. Since the interval between the interference fringes is determined by the inclination between the optical axis of the reflected light of the object to be measured 1 and the optical axis of the reference light, the object so that the interference fringes are an integer multiple of the pixels while the object to be measured 1 is stationary. The angle between the reflected light and the reference light may be adjusted, and then the measurement object 1 may be displaced to perform measurement.
However, as shown in the examples of FIGS. 17 and 18, since the inclination of the object reflected light with respect to the reference light changes depending on the light emission timing of the light irradiating the DUT 1, the interval between the interference fringes slightly changes accordingly. End up. In the present invention, measurement is always performed in the state of FIG. 18 so that the error is minimized.
For example, the polygon mirror 1 is set in a stationary state so as to be substantially perpendicular to the optical axis of the irradiation optical system, and the interference fringe interval observed at that time is an integer multiple of the CCD pixel. Adjust the mirror tilt. Thereafter, the polygon mirror 1 is rotated.
When the resolution of the signal delay by the phase adjustment between the channels of the pulse generator 3 is smaller than the pulse emission time width of the first light source (semiconductor laser) 5, the respective drivers 4 of the polygon mirror 1 and the semiconductor laser 5, 6 is supplied with a signal from the pulse generator 3, and the phase between channels is adjusted until interference fringes are observed on the monitor of the CCD image.
When the interference fringes are observed, the phase between the channels is further finely adjusted, and the upper and lower limits of the inter-channel phase where the interference fringes can be observed are confirmed while observing the monitored interference fringes, and the phases are aligned with the centers of the upper and lower limits.
Then, when the measured surface 1a is perpendicular to the optical axis 2 of the irradiation optical system (displacement amount 0), the measured surface 1a is displaced by a uniform displacement amount ± A / 2 with respect to the reference. It will be. Therefore, if interference fringes are recorded after measurement in such a state, measurement can always be performed in the state of FIG. 10, and measurement errors can be reduced.

FIG. 12 is a schematic diagram showing the configuration of the second embodiment of the dynamic shape measuring apparatus according to the present invention. In FIG. 12, the parts having the same numbers as those in FIG. 1 are the same as those in FIG.
In FIG. 12, a semiconductor laser (second light source) 17 for irradiating the rotating polygon mirror 1 to be measured with CW laser light irradiates substantially parallel light 7/9. The semiconductor laser 17 is driven by a laser driver 18.
Light from the semiconductor laser 17 is reflected and scanned by the rotating polygon mirror 1, and part of the scanned light is received by a photodiode (second light receiving means) 19. It is desirable that the photodiode 19 responds at a high speed so that light reflected by each surface of the polygon mirror 1 can be detected as a pulse.
The converter 20 performs current-voltage conversion on the output from the photodiode 19, and the counter 21 counts the output of the photodiode 19. A pulse-like signal detected by the photodiode 19 with the rotation of the polygon mirror 1 is counted by the counter 21. After counting a predetermined number of times, a trigger signal for generating a pulse signal is output to the pulse generator 3.
For example, since the polygon mirror 1 in FIG. 12 is a hexahedron, it is only necessary to output a trigger signal to the pulse generator 3 every time six pulse signal outputs are counted. When performing pulsed light emission, the number of counts may be increased accordingly.
Since the current-voltage converted signal is analog, if the signal has noise, the pulse waveform may be shaped using a filter or a comparator. While the polygon mirror 1 is rotated, a trigger is applied by the output of the photodiode 19 to cause the semiconductor laser 17 to emit light.
The delay of light emission of the semiconductor laser 5 with respect to the trigger signal is adjusted so that the interference fringes can be observed. If the interference fringes can be observed, the delay amount is further finely adjusted by adjusting the phase between channels of the pulse generator 3 as described above.
When the upper and lower limits of the delay amount at which the interference fringes can be observed are confirmed while observing the monitored interference fringes, and the delay amount is adjusted to the center between the upper and lower limits, the surface to be measured 1a is positioned with respect to the optical axis 2 of the irradiation optical system. The measured surface 1a is displaced by a symmetrical displacement amount ± A / 2 with respect to the vertical direction (the displacement amount is 0).
As a result, even when the rotational frequency of the polygon mirror 1 fluctuates, measurement can always be performed in the state shown in FIG. 10, and measurement errors can be reduced.

FIG. 13 is a schematic view showing the configuration of the third embodiment of the dynamic shape measuring apparatus according to the present invention. 13, parts having the same numbers as those in FIG. 12 are the same as those in FIG.
FIG. 13 shows a wavelength filter 22 that transmits only light of a predetermined wavelength. For example, the wavelength of the light of the semiconductor laser 5 for measuring the shape of the polygon mirror surface is 635 nm, and the wavelength of the light of the semiconductor laser 17 for monitoring the rotational frequency fluctuation of the polygon mirror is 405 nm.
Therefore, when a filter that transmits only light having a wavelength in the vicinity of 635 nm is used as the wavelength filter 22, only interference fringes for shape measurement are observed in the CCD camera 11. Since noise light can be prevented, accurate measurement is possible.
FIG. 14 is a schematic view showing the configuration of the fourth embodiment of the dynamic shape measuring apparatus according to the present invention. 14, parts having the same numbers as those in FIG. 1 have the same functions as those in FIG.
In FIG. 14, a mirror 23 for turning back and extracting light from the first light source (semiconductor laser) 5 is shown. The light extracted by the mirror 23 is folded back by the mirror 24 and folded in the direction of arrival by the retro-reflector 25.
The light reflected by the retro-reflector 25 is reflected by the mirrors 26 and 27 and becomes measurement light that irradiates the DUT 1. A time delay is given to the measurement light by an amount corresponding to the optical path from the mirror 23 to the mirror 27. The amount of delay can be changed continuously by moving the retro-reflector 25 back and forth in the direction of the arrow.

FIG. 15 is a schematic view showing the configuration of the fifth embodiment of the dynamic shape measuring apparatus according to the present invention. 15, parts having the same numbers as those in FIG. 1 are the same as those in FIG. 1, and their functions are also the same.
FIG. 15 shows a mirror 23 for turning back and extracting light from the light source 5, and the light extracted from the irradiation optical system optical path by this mirror 23 is guided to the optical fiber 30 by the coupling lens 29, It is taken out from the optical fiber 30 by the ring lens 31 and returned to the irradiation optical system optical path by the mirror 27 .
The light reflected by the mirror 27 becomes measurement light irradiated on the measurement object 1. Since the light travels about 30 cm in 1 nanosecond, the timing of the light applied to the DUT 1 can be adjusted at the nanosecond level by specifying the length of the optical fiber 30.
If the end of the optical fiber is standardized with an FC connector or the like, it can be easily replaced. Therefore, if several optical fibers having different lengths are prepared, adjustment according to the required delay amount becomes possible.
More accurate timing can be achieved by using the optical fiber 30 to complement the adjustment of the delay below the resolution of the electrical delay by using the electrical time delay using the pulse generator 3 and the like and the delay by the optical fiber 30 together. Adjustment is possible.
The timing may be adjusted by the length of the electric cable connecting the pulse generator 3 and the light source (semiconductor laser) driver 6 based on the transmission length concept similar to that of the optical fiber 30 described above.
If the delay optical system by the retroreflector 25 described above is used in combination and a large delay amount is given by the optical fiber 30 and a small delay is given by the retroreflector 25, high resolution and a wide range of delay can be achieved without increasing the size of the apparatus. Obtainable.

According to the present invention, the displacement of the measured surface within the time of light emission or light reception with respect to the measured surface when substantially perpendicular to the optical axis of the irradiation optical system is substantially symmetric, By irradiating light to the object to be measured 1 or receiving light reflected from the object to be measured 1, the amount of displacement of the surface to be measured within the light emission or light reception time is made positive and negative equal, thereby The error in the shape measurement result can be minimized.
According to the present invention, the timing adjustment means includes a first light source 5 that irradiates light to the object 1 to be measured, and a light receiving means 19 that receives reflected light from the object 1 to be measured by the first light source 5; An arithmetic unit (counter) 21 that calculates the irradiation timing of light from the first light source 5 (light source for generating interference fringes) to the DUT 1 based on the output of the light receiving means 19 is configured.
By irradiating light to the object 1 or receiving reflected light from the object 1 at the predetermined timing while following the displacement period fluctuation of the object 1 to be measured, the displacement period of the object 1 varies. Even if it exists, the influence can be suppressed and the angle detection with respect to the irradiation optical system optical axis of a to-be-measured surface can be implemented.
According to the present invention, the first light source 5 for shape measurement and the second light source 17 for frequency fluctuation detection are used with different wavelengths, and the reflected light from the device under test 1 is received from the device under test 1. A band pass filter 22 for cutting light other than light having a wavelength close to that of the light source 5 for shape measurement is provided in the optical path to the means 9.
Thereby, the light from the light source 5 for shape measurement is prevented from entering the light receiving means 9. Thereby, for shape measurement, light from the second light source 17 that becomes noise light is removed from the interference fringe image, and more accurate shape measurement can be realized.
According to the present invention, the light polarization direction of the light is different between the light source 5 for shape measurement and the second light source 17 for frequency fluctuation detection, and the reflected light from the object to be measured (light source for shape measurement) 1 is reflected. A polarizing filter that cuts light other than light close to the polarization direction of the first light source 5 for shape measurement is provided in a portion between the measured object 1 and the light receiving means 9 in the optical path .
This prevents the light from the second light source 17 from entering the light receiving means. Thereby, for shape measurement, light from the second light source 17 that becomes noise light is removed from the interference fringe image, and more accurate shape measurement can be realized.
According to the present invention, an optical system for increasing the optical path length is installed in the optical path between the first light source 5 and the object to be measured 1, and the optical path length becomes longer at the timing of the light irradiating the object to be measured. The timing adjustment is performed by giving a delay corresponding to that amount. Thereby, the apparatus cost can be reduced.
By using the optical fiber 30 in the delay optical system described above, a large optical delay amount can be obtained without increasing the size of the apparatus.

Schematic which shows the structure of 1st Embodiment of the dynamic shape measuring apparatus by this invention. The figure which shows the timing of the pulse voltage signal supplied to a polygon mirror driver, and the pulse voltage signal supplied to a semiconductor laser driver. The schematic diagram which shows the interference fringe obtained when the time width | variety of light emission of a semiconductor laser is sufficiently short with respect to the displacement speed to the optical system optical axis direction of a polygon mirror surface. The schematic diagram which shows the interference fringe image obtained when the light emission time width is not sufficiently short with respect to the displacement speed. The figure which shows the example of a simulation of the cross-sectional intensity distribution with respect to the polygon mirror longitudinal direction of the interference fringe obtained when a polygon mirror surface becomes substantially perpendicular | vertical with respect to an optical system optical axis. The figure which shows the example of a simulation of cross-sectional intensity distribution when an angle has shifted | deviated slightly from 90 degree | times. The figure which shows the example of a simulation of the cross-sectional intensity distribution of the synthetic | combination interference fringe during semiconductor laser light emission time. The figure which shows the example of a simulation of the cross-sectional intensity | strength distribution of a synthetic | combination interference fringe when the displacement of the polygon mirror surface in light source light emission time is smaller than half of the light source wavelength in the extreme end part of the longitudinal direction of a polygon mirror. The figure which shows the example of a simulation of the cross-sectional intensity distribution of a synthetic | combination interference fringe when the displacement of the polygon mirror surface in a semiconductor laser light emission time is larger than half of a light source wavelength. The figure which shows the simulation example of the longitudinal direction cross-sectional shape of the polygon mirror calculated | required when the interference fringe space | interval is an integral multiple of a pixel. The figure which shows the example of a simulation of the shape calculated | required when the interference fringe space | interval is not an integer multiple of a pixel. Schematic which shows the structure of 2nd Embodiment of the dynamic shape measuring apparatus by this invention. Schematic which shows the structure of 3rd Embodiment of the dynamic shape measuring apparatus by this invention. Schematic which shows the structure of 4th Embodiment of the dynamic shape measuring apparatus by this invention. Schematic which shows the structure of 5th Embodiment of the dynamic shape measuring apparatus by this invention. The figure which shows the polygon mirror used in the writing optical system of imaging devices, such as a laser printer and a digital copy machine, in an example of the movable object used as the measuring object relevant to this invention. Schematic explaining the minute displacement of a to-be-measured surface. FIG. 18 is a schematic diagram for explaining a minute displacement of a measured surface different from FIG. 17.

Explanation of symbols

1 Object to be measured (polygon mirror)
3 Timing adjustment means (pulse generator)
5 First light source (semiconductor laser)
7 Irradiation optical system (ND filter)
8 Irradiation optical system (beam expander)
9 Irradiation optics (beam splitter)
10 Imaging means (resolution lens)
11 Light receiving means (CCD camera)
12 Interferometric optical system 17 Second light source (semiconductor laser)
19 Second light receiving means 22 Band pass filter 30 Delay optical system (timing adjusting means, optical fiber)

Claims (6)

A first light source for irradiating light to the object under displacement, an irradiation optical system for irradiating the object with light from the first light source, a displacement of the object to be measured, and the object to be measured Timing adjustment means for adjusting the timing of light irradiation to the object, an interference optical system for causing the reflected light from the object to be measured and the reference light to interfere, and light reception for receiving interference fringes by the interference optical system Means, an imaging means for forming an image of the interference fringe on the light receiving surface, and an arithmetic unit for obtaining the surface shape of the object to be measured from the interference fringes by the interference optical system detected by the light receiving means. In the dynamic shape measuring apparatus for determining the surface shape of the object under displacement, the amount of displacement of the object measured during the light emission time of the light source or during the light reception time of the light receiving means is less than half of the wavelength of the light source. Depending on the time span Irradiating the pulsed light on an object, or receives the interference fringes, Rutotomoni determined the shape contour of the object to be measured in the displacement from the resulting interference fringes, the spacing of the interference fringes on the light receiving surface of said light receiving means the light The angle change of the measured surface during the light emission time of the first light source or the light receiving time of the light receiving means is made substantially equal with respect to the measured surface angle when it becomes an integer multiple of the pixel of the means, A dynamic shape measuring apparatus configured to start light emission of the first light source or light reception of the light receiving means . A second light source for irradiating light to said object to be measured in order to detect the angle with respect to the irradiation optical axis of the optical system of the surface to be measured, the light from the second light source reflected by the object to be measured The timing of irradiating the object to be measured from the second light receiving means for receiving light and the first light source for creating interference fringes based on the output of the second light receiving means, or the first light receiving the interference fringes dynamic shape measuring apparatus according to claim 1, wherein the second operator for calculating a timing for receiving the interference fringes by the first receiving means, further comprising a. It is assumed that the first light source and the second light source have different wavelengths, and the reflected light from the object to be measured is in the optical path from the object to be measured to the first light receiving unit. 3. The dynamic shape measuring apparatus according to claim 2, further comprising a bandpass filter that cuts light other than light having a wavelength close to that of the wavelength. The first light source and the second light source have different polarization directions, and in a portion between the measured object and the first light receiving means in the optical path of reflected light from the measured object. The dynamic shape measuring apparatus according to claim 2, further comprising a polarizing filter that cuts light other than light close to a polarization direction of the first light source. A delay optical system installed in an optical path from the first light source to the object to be measured is used as timing adjustment means for the displacement of the object to be measured and the irradiation of light to the object to be measured. Item 3. The dynamic shape measuring apparatus according to Item 1 . 6. The dynamic shape measuring apparatus according to claim 5, wherein an optical fiber is used for the delay optical system.

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