JP5412959B2 - Optical applied measuring equipment - Google Patents

Optical applied measuring equipment Download PDF

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JP5412959B2
JP5412959B2 JP2009129962A JP2009129962A JP5412959B2 JP 5412959 B2 JP5412959 B2 JP 5412959B2 JP 2009129962 A JP2009129962 A JP 2009129962A JP 2009129962 A JP2009129962 A JP 2009129962A JP 5412959 B2 JP5412959 B2 JP 5412959B2
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JP2010197370A (en
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満宏 石原
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株式会社高岳製作所
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Description

  The present invention relates to an optical applied measurement apparatus that measures physical properties such as the surface shape of an object using light.

  There are various techniques for measuring the displacement of the object and the shape of the surface by analyzing the fringes. A two-beam interferometer, a grating pattern projection surface shape measuring machine, and the like. The two-beam interferometer has long been used as an essential technique for precision measurement, and a lattice pattern projection surface shape measuring machine has been widely used as a shape measuring technique for automobiles, semiconductors, airplanes, and the like.

  The two-beam interferometer has numerous variations in how to split the two light beams, but is basically common in the sense of causing the two light beams to interfere with each other. Other variations can be divided into a low-coherence interferometer and an interferometer using high-coherence light (which is not a general term, but is hereinafter referred to as a high-coherence interferometer). A low-coherence interferometer detects a so-called zeroth-order interference fringe that appears when the optical path lengths of two light beams that interfere with each other (each of which will be referred to as an arm hereinafter) coincide with each other. It is used to measure the surface shape of objects with large undulations and the interlayer spacing inside objects. The high coherence interferometer is used for measuring a smooth curved surface or a flat object having no step like the lens surface. The major difference in structure is that the optical path lengths of the two arms must be the same in the low coherence interferometer, and the two arms do not necessarily have the same optical path length in the high coherence interferometer. If the degree of coherence is high, interference fringes can be observed even if there is a difference of tens of meters.

  The low coherence interferometer is a technique for obtaining a position where the optical path lengths of two arms are exactly the same from the zeroth-order interference fringes by changing the optical path length of one arm. FIG. 9 shows the structure of a low coherence interferometer using a Michelson interferometer. When the value of a certain pixel of the CCD camera 108 is observed while changing the optical path length of one arm using the Z table 116, a waveform as shown in FIG. 2 is observed. Interference fringes are generated in the vicinity of the equal optical path lengths of both arms and vibrates violently. The maximum position of the vibration amplitude (interference amplitude) is the position of the equal optical path length to be obtained and the position of the zeroth order interference. The surface shape of the object can be determined by determining the position of the zero-order interference for all pixels.

  Since the high coherence interferometer has a long coherence length, the amplitude of interference hardly changes even if one arm is changed, and a waveform as shown in FIG. 10 is observed. In this case, it is impossible to specify the zeroth-order interference fringe, so the absolute position of the object surface cannot be specified. However, in the range of λ / 2, which is the optical path difference corresponding to one fringe, the pixel A is The surface shape can be obtained relatively in the form of how many nm higher than the B pixel. Specifically, it is realized by changing one arm several times a predetermined amount, obtaining data in which at least three stripes are shifted, and obtaining the initial phase of the stripe for each pixel from those data. The phase is proportional to the surface shape height. Such a method is called a fringe scanning method or a phase shift method. Hereinafter, it is referred to as a phase shift method.

  The grid pattern projection method does not use the interference phenomenon as a wave of light. For example, an image of an object that is striped by periodically changing the transmittance or reflectivity of an object using an illumination light source and a lens is used. This is a method of projecting onto the surface. When a stripe is projected onto an object from an oblique direction and the stripe is observed from a direction different from the projection direction, the stripe is distorted and observed according to the undulation of the object. Since the undulation information of the object is included in the fringe distortion, the surface shape height of the object is measured by obtaining the phase of the fringe in the same way, although it is different in principle from the two-beam interferometer. Is possible. Specifically, it is realized by using a phase shift method for obtaining a phase by shifting a fringe by a specified amount as in the high coherence interferometer.

Although the advantages and disadvantages of the conventional interferometer and grating pattern projection method have been briefly described above, details are described in Non-Patent Document 1, for example.
Edited by Toru Yoshizawa, "Latest 3D optical measurement", Asakura Shoten, 2006

  One of the challenges of these methods is the high speed of measurement. In recent years, in-line measurement or on-machine measurement in which precision measurement is performed in a production process or on a processing machine has become widespread. Needless to say, speed is more important than just accuracy in these measurements. In particular, the low-coherence interferometry, which is an extremely versatile and important measurement method, is a typical method that requires a great deal of data and takes a considerable amount of measurement time.

  In general, it is necessary to follow the sampling theorem for digital data input. According to the sampling theorem, it is necessary to sample at a frequency at least twice the maximum frequency. That is, data must be taken twice or more within one change of light and dark in FIG. 2. Since one light and dark is λ / 2, it is necessary to take data at intervals of 130 nm or less with λ = 550 nm. In general, sampling is often performed at intervals of several tens of nanometers with an emphasis on accuracy. Even if it is considered to be 100 nm, in order to measure about 100 μm, data exceeding 1000 points is required. This makes high-speed measurement difficult.

  In recent years, a technique capable of restoring the original waveform even if data is taken at a rough interval that does not satisfy a general sampling theorem for speeding up has been developed and put into practical use. Unlike the general waveform, the low coherence interference waveform is a so-called gorgeous band waveform that not only restricts high-frequency components but also restricts low-frequency components, so even if it does not satisfy the general sampling theorem The original waveform can be restored.

  In reality, even with such a high-speed method, it is difficult to realize sufficient speedup while maintaining accuracy. In actual measurement, data is acquired at a certain interval, for example, every 100 nm while continuously changing the optical path length of one arm, but in the case of surface shape measurement, the data is an image, and the CCD or When two-dimensional detectors such as CMOS are used, and it is necessary to secure a certain exposure time (shutter time) when images are obtained with these two-dimensional detectors, the optical path length moves greatly during the exposure time. Then, a good sample value cannot be obtained. For example, in an extreme case, if it is moved by one period of light and dark during the exposure time, the interference fringes are not obtained and measurement is impossible. Even if it does not go so far, the contrast is lowered due to the smoothing effect, which is not preferable. Conversely, if the exposure time is reduced, signal light having a sufficient S / N cannot be obtained, which is also not preferable in terms of accuracy and reliability. Eventually, the increase in speed causes a decrease in accuracy, or the movement speed is lowered and the measurement is performed at a low speed.

  For high coherence interferometry, usually use three or more images that are mechanically shifted in the phase of fringes, each shifted in time, but simultaneously use three images that are shifted in phase using polarized light. Real time phase shift interferometers have been proposed that can be obtained. However, the fact is that there is no such speed-up method in the lattice pattern projection method.

  The present invention provides a solution to the problem of speeding up.

To solve this challenge,
Periodic change signal light generating means for generating signal light whose intensity periodically changes on the time axis;
Linearly polarized light changing means for linearly polarizing the periodic change signal light and changing the polarization direction thereof;
Analyzing means for dividing the light that has passed through the linearly polarized light changing means into at least two different linearly polarized light components;
Receiving each of the divided incident light, photoelectrically converting it according to the amount of light, and outputting it as an electrical signal, at least two storage-type detectors performing synchronized operations;
An analysis device that analyzes a plurality of signals output from the storage type detector,
The frequency of the periodic change signal light and the change frequency of the transmittance due to the combination of the linearly polarized light changing means and the detecting means are close to each other, and the accumulation type detector uses at least one period of the periodic change signal light. The optical application is performed so as to perform periodic change signal light analysis processing for calculating a value and / or phase proportional to the amplitude of the periodic change signal light from the plurality of electrical signals obtained by exposing and storing the light. Configure the measuring device.

  The storage type detector is a storage type image detector in which detectors are arranged in a two-dimensional array, and the periodic change signal light analysis process is performed for each pixel of the image by the analysis device. You can also.

  The light detection means may be attached to each pixel of the storage type image detector so that adjacent pixels receive light of different polarization directions.

Alternatively, a periodic change signal light generating means for generating signal light whose intensity periodically changes on the time axis,
A signal proportional to the product of a signal obtained by receiving the periodic change signal light and performing photoelectric conversion according to the amount of light, and at least two types of base electrical signals having different phases, which are generated by themselves or given from the outside, is output. At least two correlation detectors;
An analysis device that analyzes signals output from the plurality of correlation detectors,
The frequency of the periodic change signal light and the change frequency of the base electrical signal are close to each other, and a plurality of electrical signals obtained by correlation detection of signal light of at least one period of the periodic change signal light by the correlation detector. The optical applied measurement apparatus is configured to perform a period change signal light analysis process in which a value and / or a phase proportional to the amplitude of the period change signal light is calculated from the signal by the analysis apparatus.

  The correlation detector may be a correlation image detector in which detectors are arranged in a two-dimensional array, and the periodic change signal light analysis processing may be performed for each pixel of the image by the analysis device. it can.

The period change signal light generating means includes:
A two-beam interferometer that bifurcates the light from the light source and causes the reflected light from the reference mirror and the reflected light from the object to interfere with each other;
An optical path length changing means capable of changing at least one of the two optical paths, and
The optical applied measurement device is configured to generate the periodically changing signal light by periodically changing the intensity value of interference by changing the optical path length at a constant speed by the optical path length changing means.

  The light source is a light source that emits low-coherent light, is an equal optical path length interferometer in which two optical paths of the two-beam interferometer are substantially equal, and the optical path length of one optical path is changed by the optical path length changing means. The undulating shape of the surface of the target object is obtained by detecting the position where the two optical paths are exactly equal in optical path length by repeating the periodic change signal light analysis process a plurality of times while changing at a constant speed. .

  The period-change signal light analysis processing is performed at intervals so as to be about 3 to 10 times in the interference section observed near the position where the optical path lengths of the two optical paths are equal, and the optical paths of the two optical paths. The position where the lengths coincide with each other is speeded up by obtaining the position where the amplitude obtained by the periodic change signal light analysis processing is maximized with a resolution smaller than the interval by an interpolation method.

The period-change signal light analysis processing is performed at intervals so as to be about 3 to 10 times in the interference section observed near the position where the optical path lengths of the two optical paths are equal, and the optical paths of the two optical paths. The position where the lengths exactly match is determined by using the amplitude and phase obtained by the periodic change signal light analysis processing, and the phase when the amplitude is maximum and the periodic change signal light is regarded as a Cos wave is 2π · n ( The speed may be increased by obtaining a position where n is an integer .

  Alternatively, the light source is a light source that emits highly coherent light, and the optical path lengths of the two optical paths of the two-beam interferometer are not necessarily equal optical path lengths, and one of the optical paths is changed by the optical path length changing means. The period change signal light analysis process is performed by the analysis device while changing the optical path length at a constant speed, and the undulation shape of the surface of the target object is obtained from the calculated phase information.

At this time, the period change signal light generating means is
A light source, and a lattice pattern projector that projects illumination light from the light source onto the object as a checkered pattern;
A phase shift mechanism that continuously shifts the projected grating pattern, and
The optical applied measurement device is configured to have a function of generating periodically changing signal light by periodically changing the brightness of each point on the target object by shifting the lattice pattern phase at a constant speed by the phase shift mechanism.

  An optical applied measurement device is used to change the lattice fringe pattern at a constant speed by the phase shift mechanism and perform the periodic change signal light analysis processing by the analysis device, and obtain the undulation shape of the target object surface from the calculated phase information. It can also be configured.

  By configuring as described above, it is possible to realize an optical applied measuring device excellent in high speed.

  In the following, embodiments that are considered to be the best for concrete implementation of the present invention will be described.

  First, a first example of an embodiment embodying the present invention will be described with reference to FIG.

  The light source 101 is a discharge type or filament type broadband light source or LED, or a laser having a relatively wide bandwidth and a short coherent length, and has a band filter 102 for controlling the bandwidth. The illumination light whose band is controlled by the band filter 102 is directed toward the objective lens 104 by the half mirror 103, passes through the objective lens 104, and is irradiated toward the object 106. The illumination light is divided into the object direction and the reference mirror 107 direction by the half mirror 105 between the objective lens 104 and the object 106, and the light reflected by each of them is again superimposed by the half mirror 105 and passes through the objective lens 104 again. Then, the light passes through the half mirror 103 toward the CCD camera 108 which is a storage type image detector.

  Two CCD cameras 108 are prepared. By splitting the light incident on the CCD camera 108 by the half mirror 109, both are optically arranged so that they can be regarded as the same position. Polarizing filters (hereinafter referred to as analyzers) 110a and 110b are arranged in front of the CCD cameras 108a and 108b, respectively, so that the two CCD cameras 108a and 108b receive π / 4 different polarization components. It is configured. The half mirror 109 is a non-polarization half mirror having a function of only dividing light intensity into two regardless of polarization.

A mechanism for generating rotating linearly polarized light is inserted between the half mirror 103 and the half mirror 109.
A polarization filter (hereinafter referred to as a polarizer) 111 converts the light into linearly polarized light, and then a λ / 4 retardation film 112 converts it into circularly polarized light. Further, another λ / 4 retardation film 113 is arranged in the bearing hollow portion to form an inner track. A ring (hereinafter referred to as an inner ring) is rotated by a motor 114 to obtain rotating linearly polarized light.

  Various mechanisms for generating rotating linearly polarized light are also conceivable. The simplest realization method is a method of rotating the polarizing plate. As before, it can be realized by attaching a polarizing plate to the hollow part of the bearing and rotating the inner ring by a motor. However, in this case, it is sufficient that the incident light to the polarizing plate is completely unpolarized, but if it is polarized, the transmitted light intensity changes depending on the direction of polarization. In the previous example, the transmission intensity does not change due to the change in the polarization direction.

  Alternatively, light linearly polarized by a polarizer can be electrically rotated using an electro-optical element having optical activity such as liquid crystal. If the operation of changing the azimuth of polarized light from a certain azimuth to an orthogonal azimuth and changing it to the original azimuth is repeated, it becomes the same as rotating linearly polarized light.

  The speed of the changing polarization azimuth can be expressed by an angular speed ω, and the change in transmittance through which linearly polarized light rotating at the angular speed ω passes through the analyzers 110a and 110b in front of the two CCD cameras 108a and 108b is about π / 2. It can be expressed by a sine wave K (1 + Cos (2ωt)) and K (1 + Sin (2ωt)) having a phase difference. Here, t represents time, and K represents a coefficient for adjusting to the actual transmittance determined by the characteristics of the polarizing element. K is a fixed value.

  The object 106 is placed on the Z table 116 that can move in the optical axis direction, and the optical path length difference between the two arms separated by the half mirror 103 can be changed by the movement of the Z table 116. By moving the Z table 116, the reflected light directed to the CCD camera 108 interferes with the half mirror 103. If the phase difference of light from both arms is 0 or a multiple of wavelength λ n · λ (n is an integer), it is strengthened by positive interference, and the phase difference is half wavelength λ / 2 or half wavelength + multiple of wavelength (1 / 2 + n) If they are shifted by λ, they are weakened by negative interference. When the Z table 116 is moved at a constant speed, the phase difference continuously changes, so that positive interference and negative interference repeat with a period of movement amount λ / 2 (the phase difference is twice the movement amount). A waveform will be obtained. If the moving speed of the Z table 116 is v, the intensity of the signal light is expressed as a + b × Cos (4πvt / λ + φ). Here, a represents the light intensity when there is no interference (does not), and b represents the vibration amplitude (so-called interference fringe visibility). φ is an initial phase, and has a different value depending on the position (XY coordinate value) according to the undulation of the object.

  Here, if the speed of the Z table 116 and the rotational speed (angular speed) of the rotating linearly polarized light are adjusted to be ω = 2πv / λ, the signals V1 and V2 obtained by the CCD cameras are (a + b × Cos (2ωt + φ) ) × K (1 + Cos (2ωt)) and (a + b × Cos (2ωt + φ)) × K (1 + Sin (2ωt)) are respectively obtained by integrating the exposure time Δt.

  If the exposure time Δt is appropriately selected so that 2ωΔt = 2π · n, the integration of Sin (n · 2ωt) and Cos (n · 2ωt) becomes 0, and can be expressed as follows.

  Further, if KaΔt can be obtained in some form, the values of b and φ can be easily obtained by subtracting KaΔt from the obtained signal values V1 and V2, respectively.

  Consider a case where a so-called low coherence interference waveform as shown in FIG. In this case, the wavelength λ is considered as the center (center of gravity) wavelength of the band, and can be considered as a model that attenuates as the coherence decreases as the distance from the zeroth-order interference position increases. In this case, at the position where the vibration waveform does not appear sufficiently away from the 0th-order interference position (that is, the region where the optical path length difference exceeds the coherent length), b representing the amplitude of the vibration waveform is 0, so the value of KaΔt is directly Will be obtained. If the value of KaΔt is obtained, the value of the vibration amplitude b or the initial phase φ can be obtained from the above formula.

  Assuming that KaΔt has already been obtained, the vibration amplitude b at that position is obtained using V1 and V2 obtained by exposing vibrations of several cycles as shown by v · Δt in FIG. be able to. Although the vibration amplitude is not constant within the exposure time, it can be considered that an average b within the exposure range is obtained.

FIG. 3 depicts a change in the value of the local amplitude b (z) of the vibration waveform of FIG. 2 obtained in this way.
For example, if the value of b is obtained at regular intervals as indicated by the black circles in FIG. Furthermore, the maximum position can be estimated with higher accuracy by using the interpolation method. For example, considering that the maximum position Zpeak is estimated by fitting a Gaussian function from three points of the maximum value b (z0) of b and values b (z1) and b (z-1) before and after the maximum value b (z0) as follows. Can be calculated.

  As described above, it is difficult to increase the speed of low-coherence interferometry, but if such a method is used, it is possible to significantly increase the speed. For example, consider a case where illumination light having a coherent length of 30 μm is used. Although it is not accurate, it is assumed here that the coherent length corresponds to the length of the bottom of the mountain in FIG. If b values of at least three points within this coherent length can be obtained, the position of the zeroth order interference can be obtained from (Equation 4), and values can be obtained at intervals of 10 μm, and vibration waveforms can be generated during exposure. Since it is premised on a change, a sufficient exposure time can be taken even if the Z table 116 is moved at a high speed.

  For example, to measure a measurement range of 100 μm, it is only necessary to acquire about a dozen images, so even if a normal TV camera with a frame rate of 30 frames / second is used, data acquisition is possible. Only about 0.4 s is required. Compared with the conventional method, the speed can be increased by an order of magnitude.

  As described above, the zero-order interference position can be specified only by the amplitude b of the vibration waveform, but more accurate measurement is possible if the phase is taken into consideration. The phase of the zeroth-order interference position is specified because positive interference is the maximum position. That is, the position is φ = 2π · n in terms of Cos wave. If a rough zero-order interference position is estimated from the value of b and a position that gives a phase that satisfies the above condition is used as the final result, the accuracy can be further improved.

  Although a CCD camera is assumed here as a detector, any detector may be used as long as it is a storage type detector. There is no need to be a two-dimensional detector, and a one-dimensional detector called a so-called line sensor may be used, or a zero-dimensional detector that detects only one point may be used.

  Further, although the object 106 is moved by the Z table 116, the reference mirror 107 may be moved if the NA of the objective lens 104 is small and defocusing is not a big problem. Moreover, although the interferometer is a Michelson type, it may be a Miro interferometer or a linic interferometer. Any interferometer that functions as a low coherence interferometer may be used. The number of detectors, the method of interpolation calculation, and the like are only shown here, and other methods may be used.

  Next, let us consider a case where the band-pass filter 102 is significantly narrowed or a high coherence interferometer is formed by using a laser having high coherency. As described above, the high-coherence interferometer cannot obtain the zeroth-order interference position, but can obtain the relative measurement by obtaining the initial phase. With low coherence interference, the amplitude and phase of the vibration waveform were obtained at certain intervals over a wide measurement range, but with high coherence interference, it is only necessary to obtain the initial phase (in other words, only that is possible). Only one measurement is required.

  Similar to the case of low coherence interference, it is sufficient to move the Z table 116 and obtain the initial phase. However, in this case, since the value corresponding to the aΔt is not known, the same calculation method as in the case of low coherence interference is used. Then, the initial phase cannot be obtained. In this case, at least three detectors are required. For example, as shown in FIG. 4, an optical element 401 that divides light into an intensity ratio of 1: 2 and a half mirror 109 are combined so that the intensity can be divided by 1/3, and each transmits a different polarization direction. For example, analyzers 110a, 110b, and 110c that transmit polarized light having azimuth angles of 0 degrees, π / 3, and 2π / 3 are configured in front of three detectors 108a, 108b, and 108c. Since there are three unknowns (a, b, and φ) in (Equation 3), the initial phase φ can be obtained if three or more data are obtained.

  Alternatively, as shown in FIG. 5, the same can be realized by attaching analyzers having different polarization directions to four adjacent pixels of the CCD camera. In this case, it can be considered that four images having a ¼ pixel number and different polarization directions can be obtained. Since the spot size of the imaging light incident on the pixel usually has a size of several pixel levels so as to satisfy the sampling theorem, there is basically no problem even in the polarization division based on such a position.

  FIG. 6 is substantially the same as FIG. 1 showing the first embodiment, but only the peripheral portion of the detector is different. In the first embodiment, with respect to the temporal vibration waveform of incident light, the transmittance is periodically changed by the rotating linearly polarized light generation mechanism and the analyzer, and integration processing is performed for the exposure time. This is because the incident light is multiplied by the sine wave and time-integrated, that is, the correlation value between the incident time change waveform and the sine wave is obtained. Since the directions of the analyzers placed in front of the plurality of detectors are different, the frequency of the change waveform of the transmittance is the same, and a plurality of correlation values are simultaneously obtained with sine waves having different phases. For example, when two detectors and analyzers having different π / 4 polarization axes are used, correlations between sine waves having different π / 2 phases, that is, Sin waves and Cos waves are detected simultaneously. The expansion is based on a so-called orthogonal function.

Such correlation detection can be performed optically as in the first embodiment, but can also be performed electrically. That is, a circuit for multiplying a current signal of a photodiode generated in proportion to incident light by a sine wave signal (basic electrical signal) and integrating the signal for a certain time may be formed. A two-dimensional correlation detector 117 can be manufactured by two-dimensionally arranging elements having such functions. Further, if a plurality of correlation detection circuits are provided for one photodiode so that a plurality of sine wave signals having different phases can be detected simultaneously, the same operation as that of the first embodiment is electrically performed. It will be possible.

  Next, an example of the grid pattern projection method will be described with reference to FIGS. The mask pattern 118 is a sinusoidal lattice pattern having a sinusoidal transmittance distribution as shown in FIG. 8, is transmitted and illuminated by the illumination light source 101, and is projected onto the object 106 by the illumination optical system.

  The grating pattern projected onto the object 106 is imaged by an imaging optical system having an optical axis in a direction different from that of the illumination optical system. As in the first embodiment, a polarizing plate 111, a λ / 4 phase difference plate 112, and a λ / 4 phase difference plate 113 that is rotated at a constant speed by a motor 114 are inserted into the image forming optical path by the objective lens 104, and the amount of light is reduced to 1. / Prisms 401 and 109 divided into three, analyzers 110a, 110b and 110c having different polarization azimuth angles, and CCD cameras 108a, 108b and 108c.

  Basic operations, calculations, and the like are exactly the same as in the case of the high coherence interferometer in the first embodiment. The difference is that in order to obtain a waveform that oscillates in time when the Z table is moved, the physical principle of light wave interference is used in the first embodiment. It is only that it is based on the imaging projection of the mask pattern 118 that has been shaped.

  That is, by moving the Z table 116, the brightness of each point on the object 106 increases and decreases sinusoidally as the transmittance of the mask pattern 118 changes. When exposure is performed for a predetermined time in a state where the cycle and the cycle of transmittance change of the imaging optical system are matched, the values of the same coordinate values of the three CCD cameras 108a, 108b, and 108c are sine having different phases. The result of correlation detection using waves is obtained. From these results, the initial phase φ of the projected grating pattern can be calculated. Since the initial phase φ includes the undulation information of the object 106, the surface shape can be measured.

  With respect to the lattice pattern projection method, polarization splitting as shown in FIG. 5 is possible, and the correlation detection portion can be electrically performed as in the second embodiment.

  In this example, the Z table 116 is moved in order to obtain a waveform that oscillates with time, but other methods can of course be considered. For example, the mask pattern 118 can be moved by using a linear actuator, or can be realized by linearly moving the entire illumination optical system. Any method can be used.

  The present invention is considered to be in great demand in applications that are valuable for high speed, such as in-line and on-machine measurements.

It is the figure which showed the 1st Example of this invention. It is a figure for demonstrating a low coherence interference waveform. It is a figure which shows the change of the vibration amplitude of the waveform of FIG. It is a figure for demonstrating the method to isolate | separate into three types of polarization directions. It is a figure for demonstrating the other method of isolate | separating a polarization direction into multiple types. It is the figure which showed the 2nd Example of this invention. It is the figure which showed the 3rd Example of this invention. It is a figure for demonstrating a mask pattern. It is a figure for demonstrating the conventional low coherence interference measurement. It is a figure which shows the interference waveform by high coherence light.

DESCRIPTION OF SYMBOLS 101 ... Light source 102 ... Band-pass filter 103 ... Half mirror 104 ... Objective lens 105 ... Half mirror 106 ... Object 107 ... Reference mirror 108a, 108b, 108c ... CCD camera 109 ... Half mirror 110a, 110b, 110c ... Analyzer 111 ... Polarizing filter DESCRIPTION OF SYMBOLS 112 ... (lambda) / 4 phase difference plate 113 ... (lambda) / 4 phase difference plate 114 ... Motor 115 ... Analysis apparatus 116 ... Z table 117 ... Two-dimensional correlation detector 118 ... Mask pattern 401 ... Optical element

Claims (12)

  1. Periodic change signal light generating means for generating signal light whose intensity periodically changes on the time axis;
    Linearly polarized light changing means for linearly polarizing the periodic change signal light and changing the polarization direction thereof;
    Analyzing means for dividing the light that has passed through the linearly polarized light changing means into at least two different linearly polarized light components;
    Receiving each of the divided incident light, photoelectrically converting it according to the amount of light, and outputting it as an electrical signal, at least two storage-type detectors performing synchronized operations;
    An analysis device that analyzes a plurality of signals output from the storage type detector,
    The frequency of the periodic change signal light and the change frequency of the transmittance due to the combination of the linearly polarized light changing means and the detecting means are close to each other, and the accumulation type detector uses at least one period of signal light of the periodic change signal light. Performing periodic change signal light analysis processing for calculating a value and / or a phase proportional to the amplitude of the periodic change signal light by the analysis device from a plurality of electrical signals obtained by exposure and accumulation of Optical application measuring device.
  2. The storage-type detector is a storage-type image detector in which detectors are arranged in a two-dimensional array, and the periodic change signal light analysis process is performed for each pixel of the image by the analysis device. The optical applied measuring device according to claim 1, wherein
  3. 3. The applied optical measurement apparatus according to claim 2, wherein the light detection unit is attached to each pixel of the storage type image detector, and adjacent pixels receive light having different polarization directions.
  4. Periodic change signal light generating means for generating signal light whose intensity periodically changes on the time axis;
    A signal proportional to the product of a signal obtained by receiving the periodic change signal light and performing photoelectric conversion according to the amount of light, and at least two types of base electrical signals having different phases, which are generated by themselves or given from the outside, is output. At least two correlation detectors;
    An analysis device that analyzes signals output from the plurality of correlation detectors,
    The frequency of the periodic change signal light and the change frequency of the base electrical signal are close to each other, and a plurality of electrical signals obtained by correlation detection of signal light of at least one period of the periodic change signal light by the correlation detector. An optical applied measurement apparatus, wherein a periodic change signal light analysis process is performed for calculating a value and / or phase proportional to the amplitude of the periodic change signal light from the signal by the analysis apparatus.
  5. The correlation detector is a correlation image detector in which detectors are arranged in a two-dimensional array, and the periodic change signal light analysis processing is performed for each pixel of an image by the analysis device. The optical applied measuring device according to claim 4.
  6. The period change signal light generating means includes:
    A two-beam interferometer that bifurcates the light from the light source and causes the reflected light from the reference mirror and the reflected light from the object to interfere with each other;
    An optical path length changing means capable of changing at least one of the two optical paths, and
    6. The function according to claim 1, further comprising a function of generating periodically changing signal light by periodically changing the intensity value of interference by changing the optical path length at a constant speed by the optical path length changing means. Optical application measuring device.
  7. The light source is a light source that emits low-coherent light, is an equal optical path length interferometer in which two optical paths of the two-beam interferometer are substantially equal, and the optical path length of one optical path is changed by the optical path length changing means. The periodic change signal light analysis processing is repeated a plurality of times by the analysis device while changing at a constant speed, and the undulation shape of the surface of the target object is obtained by detecting the position where the two optical paths have the same optical path length accurately. The optical applied measuring device according to claim 6.
  8. The period-change signal light analysis processing is performed at intervals so as to be about 3 to 10 times in the interference section observed near the position where the optical path lengths of the two optical paths are equal, and the optical paths of the two optical paths. 8. The applied optical measurement according to claim 7, wherein a position where the lengths exactly coincide is obtained with a resolution finer than the interval by an interpolation method, wherein a position where the amplitude obtained by the periodic change signal light analysis processing is maximized is obtained. apparatus.
  9. The period-change signal light analysis processing is performed at intervals so as to be about 3 to 10 times in the interference section observed near the position where the optical path lengths of the two optical paths are equal, and the optical paths of the two optical paths. The position where the lengths exactly match is determined by using the amplitude and phase obtained by the periodic change signal light analysis processing, and the phase when the amplitude is maximum and the frequency change signal light is regarded as a Cos wave is 2π · n ( The optical applied measuring device according to claim 7 , wherein a position where n is an integer) is obtained .
  10. The light source is a light source that emits highly coherent light, the optical path lengths of the two optical paths of the two-beam interferometer are not necessarily equal optical path lengths, and the optical path length of one optical path by the optical path length changing means. 7. The applied optical measurement device according to claim 6, wherein the periodic change signal light analysis process is performed by the analysis device while the undulation shape of the target object surface is obtained from the calculated phase information. .
  11. The period change signal light generating means includes:
    A light source, and a lattice pattern projector that projects illumination light from the light source onto the object as a checkered pattern;
    A phase shift mechanism that continuously shifts the projected grating pattern, and
    6. A function of generating a periodic change signal light by periodically changing the luminance of each point on the target object by shifting the phase of the lattice pattern at a constant speed by a phase shift mechanism. The optical applied measuring device according to any one of the items.
  12. The grid pattern is changed at a constant speed by the phase shift mechanism, the period change signal light analysis processing is performed by the analysis device, and the undulation shape of the target object surface is obtained from the calculated phase information. 11. An optical applied measuring device according to 11 .
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