JP2009074837A - Three-dimensional shape measurement apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for reducing a measurement time, and implementing a three-dimensional measurement. <P>SOLUTION: An optical path forming section 5 receives a wideband light from a wideband light source 1, branches it to a reference optical path and a measurement optical path, causes it to enter into the reference optical path and the measurement optical path, combines reflection lights from a reference mirror and a to-be-measured object, and outputs a combined light to an imaging means 10. An optical path length varying means 8 varies an optical path length of the measurement optical path. The imaging means takes an image of an output from the optical path forming section at timing when aliasing occurs in response to a change in the optical path length, and obtains interference pattern data including an interference pattern. The optical path length detecting means 20 is configured so as to remove a frequency component generated by aliasing from the interference pattern data obtained by the imaging means and obtain a particular optical path length indicating a characteristic value of the interference pattern. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a three-dimensional shape measuring apparatus that three-dimensionally measures the shape of an object to be measured using an interference phenomenon caused by broadband light (for example, white light) having a plurality of spectrums (hereinafter, described in terms of wavelengths). In particular, one of the broadband light is incident on a reference optical path having a reference mirror at the far end, and the other of the broadband light is incident on a measurement optical path having an object to be measured at the far end, from the reference mirror (reflecting mirror) and the object to be measured. The shape of the object to be measured based on the optical path length in which the interference fringes obtained by changing the optical path length of either the reference optical path or the measurement optical path in the interference section (interferometer) that causes interference due to each return light The present invention relates to a technique for shortening the time for obtaining the optical path length in which the interference fringes occur.

  In general, the shape measuring apparatus using the above interference phenomenon utilizes the fact that interference fringes exhibit the maximum luminance when the optical path lengths of both the reference optical path and the measurement optical path are equal. That is, the optical path length of either the reference optical path or the measurement optical path is changed (hereinafter, the optical path length of the reference optical path is fixed and the optical path length of the measurement optical path is changed), and the interference fringes generated at that time are the largest. An optical path length at a position indicating luminance (a change amount of the optical path length: hereinafter referred to as “specific optical path length”) is measured as a displacement of the object to be measured in the change direction of the optical path length (Patent Document 1).

  In Patent Document 1, a B component (blue band component), a G component (green band component), and an R component (red color component) are obtained based on interference light obtained by changing the optical path length with time. (Band component) to detect the change in the phase of the interference fringe with respect to the change in the optical path length, and the specific optical path of the position where the interference fringe shows the maximum luminance is the optical path length where the three phases match Certified as head. The shape is measured from the authorized specific optical path length.

Japanese Patent Application No. 2006-371632

  In general, since the shape measuring apparatus measures a large number of objects to be measured, it is desired to reduce the measuring time to some extent. In shortening, the improvement target elements include the variable time (or speed) of the optical path length, the imaging time of the camera, the number of times of imaging, etc., but the imaging time is limited by the inherent minimum exposure time of the imaging element of the camera. receive.

  Therefore, the prior art will be considered below from the viewpoint of measurement time. In the case of Patent Document 1, the phase of the interference fringe is specified based on the interference light data and the specific optical path length is obtained. At this time, the analog data of the interference light is converted into digital data representing the interference light. Thus, the time domain (optical path length domain) data is subjected to an FFT transform and separated into each band component on the frequency domain, and interference fringes of each band component are obtained again in the time domain, and the phase coincidence point is obtained. At this time, in order to reproduce the interference fringes from the acquired digital data, it is generally repeated acquisition that can obtain at least three points of data per cycle of the interference fringes to be reproduced from the sampling theorem or the like. It is necessary to convert to digital data at the timing.

  In general, the interference fringes measured by the interference method in the shape measuring apparatus are represented by the change in luminance with respect to the optical path length changed as shown in FIG. 7A by the digital data, and the spectrum distribution is shown in FIG. It is expressed on the frequency vs. amplitude coordinate as shown in (B). At this time, the envelope width Δt of the interference fringes in FIG. 7A (for example, the half-value width: the width on the horizontal axis where the peak luminance value is halved) is the frequency band of FIG. It is known to have a correlation with the width ΔF (for example, the half width: the width of the horizontal axis where the peak amplitude is halved). Therefore, depending on the envelope width Δt, the bandwidth ΔF is narrowed as shown in FIG. 7B, and a condition having a space of ΔFc in the lower frequency band is obtained. That is, the condition that the bandwidth ΔF does not become a wide band until the frequency approaches 0 (DC component) as indicated by a two-dot chain line in FIG. 7B is obtained.

  According to the sampling theorem, if the sampling frequency Fs is sufficiently higher than the highest frequency component included in the interference fringes, the frequency component of the original interference fringes can be reproduced as shown in FIG. As the sampling frequency Fs is lowered, aliasing occurs. That is, as shown in FIG. 7C, the frequency of the original desired frequency component (solid line portion) and the aliasing frequency component due to aliasing (dotted line portion) is reduced (as in the case of frequency division). 7), they are close to each other as shown in FIG. 7D, and the height is changed over as shown in FIG.

  Therefore, the present inventor has focused on the following. That is, as shown in FIG. 7B, there is a space of ΔFc in the band characteristics of the interference fringe itself, so that by selecting the sampling frequency Fs, a desired frequency component and a folded frequency component as shown in FIG. Can be separated in frequency. Therefore, as shown in FIG. 7F, the aliasing frequency component is removed by a filter, and reproduction is possible by extending the frequency axis as much as the frequency is lowered by further lowering the sampling frequency.

  Then, a desired frequency component of interference fringes can be obtained even at a frequency lower than the frequency that satisfies the sampling theorem. In other words, we focused on shortening the measurement time by reducing the number of times of data acquisition by reducing the sampling frequency Fs.

  The present invention provides a technique capable of performing three-dimensional measurement by shortening the measurement time.

  In order to achieve the above object, it is necessary to consider the relationship between the envelope fringe width Δt, the bandwidth ΔF, and its maximum frequency Fh. In general, the period of the interference fringes determines the original interference. It is about ½ of the period λ of the center wavelength of the light source of the broadband light source that is the source to be generated. The envelope width Δt of the interference fringes at that time depends on the bandwidth ΔF of the broadband light source as described above. In general, since ΔF << [1 / (λ / 2)] <Fh is satisfied, a space ΔFc (= Fh−ΔF) can be sufficiently provided in the lower frequency band as shown in FIG. 7B.

  Specifically, the invention described in claim 1 is a broadband light source (1) that outputs broadband light having a plurality of spectrums, and a measurement optical path in which the broadband includes a reference optical path having an optical reference mirror and an object to be measured. And an optical path forming unit (5) for combining and outputting the reflected light from the reference mirror and each reflected light from the irradiation position of the irradiation range of the object to be measured; An optical path length varying means (8) for changing the optical path length of either the reference optical path or the measurement optical path, and the optical path forming section at a timing at which aliasing occurs with respect to the change of the optical path length by the optical path length varying means Imaging means (10) for acquiring interference fringe data including interference fringes by imaging the output from, and removing frequency components generated by the aliasing from the interference fringe data output from the imaging means; And an optical path length detecting means for obtaining a specific optical path length when indicating the feature values of the serial interference fringes (14), based on 該特 constant light path length was determined and configured to measure the shape of the object to be measured.

  According to a second aspect of the present invention, in the first aspect of the present invention, the timing at which the aliasing occurs with respect to the change in the optical path length by the optical path length varying means is the optical path length by the optical path length varying means. The change is such that the interval exceeds λ / 6, where λ is the central wavelength of the broadband light.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the image pickup means picks up an image with a specific minimum exposure time, and the speed at which the optical path length varying means changes the optical path length is v. In this case, the time interval in which the change in the optical path length exceeds λ / (6v) is taken as the timing.

  The invention according to claim 4 is the invention according to claim 1, 2, or 3, wherein the optical path length detection means converts the interference fringe data output from the imaging means into frequency domain data, An interference fringe data selection unit (14a) for selecting new interference fringe data by removing unnecessary components due to the aliasing in acquiring the data by the imaging means, and the feature value based on the new interference fringe data. An optical path length calculation unit (14c) for obtaining the specific optical path length to be expressed.

  The invention according to claim 5 is the invention according to claim 4, wherein the optical path length detecting means extracts at least two wavelength components from the new interference fringe data selected by the interference fringe data selection unit. A wavelength selection unit (14d) is included, and the optical path length calculation unit obtains the optical path length at which the phase difference between the extracted at least two wavelength components is substantially zero as the specific optical path length.

  According to the present invention, interference fringe data is acquired (sampled) at the timing when aliasing occurs, unnecessary frequency components generated due to the aliasing are removed, and displacement is measured, so that aliasing occurs. In addition, the data acquisition timing period can be lengthened, that is, the number of data acquisition times can be reduced, the optical processing time can be reduced accordingly, and the measurement time can be shortened. In other words, if the main measurement time is represented by [variable optical path length + data acquisition times × (exposure time + acquisition processing time)], the measurement time can be shortened by the reduction in the number of data acquisitions.

  Embodiments according to the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a functional configuration of the first embodiment. FIG. 2 is a diagram for explaining interference fringes. FIG. 3 is a diagram showing a second embodiment in which the optical path length detection unit in FIG. 1 is changed. FIG. 4 is a diagram for explaining the operation of the interference fringe data selection unit of FIG. 5 and 6 are diagrams for explaining the operation of the optical path length varying unit in FIG. 3, FIG. 5 shows interference fringes of each frequency component, and FIG. 6 shows the phase characteristics thereof. FIG. 7 is a diagram for explaining an operation for obtaining interference fringes by removing the influence of aliasing in the embodiment of FIG. FIG. 7 is also a diagram for explaining the background of the present invention in the column “Problems to be Solved by the Invention”.

[1. Overall Configuration of First Embodiment]
In the first embodiment, as described above, the unnecessary timing generated by the aliasing from the respective data obtained by imaging with the camera 10 as the imaging means at the timing later than the timing satisfying the sampling theorem, that is, the timing when aliasing occurs. Excluding the components, data equivalent to the interference fringes obtained at the timing satisfying the original sampling theorem is extracted. Then, the specific optical path length (displacement) is obtained from the optical path length in which the peak value of the intensity of the extracted interference fringe is generated (the optical path length may be the amount of change when the optical path length is changed before the interference fringe is generated). It is a configuration.
In the following description, when the optical path length of the measurement optical path is changed, the optical path length in which the interference fringe is generated (the change amount when the optical path length is changed before the interference fringe is generated) is “specific optical path length”. This indicates the displacement of the shape of the object to be measured.

In FIG. 1, the light source 1 uses a white light source that emits light with low coherency having a large number of wavelength components over a wide band in order to cause interference. The collimator lens 2 collects the white light (broadband light) from the light source 1 and sends it to the beam splitter 3. The beam splitter 3 converts the direction of white light and sends it to the objective lens 4. The objective lens 4 converts white light into parallel light and sends it to the beam splitter 5 (optical path forming unit). The beam splitter 5 branches the white light received from the objective lens 4 in two directions, and one is sent as measurement light to the measurement object 7 (the optical path from the beam splitter 5 to the measurement object 7 is used as a measurement optical path). The other one is sent to the reference mirror 6 as reference light (the optical path from the beam splitter 5 to the reference mirror 6 is taken as the reference optical path). In this example, the distance between the beam splitter 5 and the reference mirror 6 is fixed, that is, the optical path length of the reference optical path is fixed.
Instead of the beam splitter 5, a half mirror can be used.

  The measurement optical path is configured so that a desired irradiation range to be measured on the surface of the object to be measured 7 is simultaneously irradiated with white light.

  The DUT 7 is mounted on a piezo 8 as an optical path length varying unit. The piezo 8 is composed of a piezoelectric element, and in accordance with an instruction from the optical path length control means 16, the object to be measured 7 is continuously moved in the Z-axis direction (FIG. 1) with respect to the XY plane (surface orthogonal to the paper surface of FIG. The optical path length of the measurement optical path is variably controlled at a predetermined speed by being displaced (moved) in the vertical direction of the paper surface.

  Here, the variable method for changing the optical path length in the present invention will be described by assuming that the variable speed is continuous and the variable speed is constant. However, the variable method is variable in finer steps than the data acquisition timing by a camera or the like described later. You may do it.

  The piezo 8 is means (optical path length variable means) that changes the optical path length of the measurement optical path with respect to the fixed position of the beam splitter 5 under the control of the optical path length control means 16. Here, the description will be given by fixing the optical path length of the reference optical path and changing the optical path length of the measurement optical path. However, in order to generate interference fringes, the piezo 8 is attached to the reference mirror 6, the measurement optical path is fixed, A configuration in which the optical path length of the reference optical path is variable is also possible.

  White light (hereinafter also referred to as “returned light”) reflected from each of the reference mirror 6 and the DUT 7 is combined (combined) by the beam splitter 5 and collected by the objective lens 4. To be lighted. The return light passes through the beam splitter 3, is converted into parallel light by the imaging lens 9, and is input to the camera 10.

  At this time, in response to an instruction from the optical path length control means 16, the camera 10 captures the return light according to the distance (or the time interval at which the piezo 8 changes the optical path length of the measurement optical path). Interference fringes due to light are imaged (actually, the imaging only captures the return light, but since there are interference fringes due to the return light that appears when the imaging data is developed later, Is referred to as “imaging”.) The captured interference fringes are stored in the memory 13. At this time, since the measurement optical path is configured to simultaneously irradiate the entire desired irradiation range of the DUT 7 with white light as described above, each irradiation position of the irradiation range, that is, a position to be measured (hereinafter, “ An interference fringe corresponding to the return light from “measurement position” is imaged.

  As a modification of the optical system in FIG. 1, an optical system in which the objective lens 4 is disposed in each of the measurement optical path and the reference optical path instead of the position in FIG. 1 can be configured. The invention is not limited to the optical system of FIG. However, the following description will be described with reference to FIG.

  The timing of shooting by the camera 10 and the timing of storage by the memory 13 are the data acquisition timing of the present invention, and both are output in synchronization by the optical path length control means 16. That is, the optical path length control means 16 variably instructs the piezo 8 on the optical path length at a predetermined speed, while generating a timing signal at predetermined time intervals and sending it to the camera 10 and the memory 13 to acquire data at that timing. . That is, the camera 10 and the memory 13 capture and store the imaging data of the return light (the brightness data indicating the brightness of the return light) at the timing of the timing signal.

  In general, interference fringes due to broadband light have a repetition period that is half the center wavelength λ of broadband light. In order to prevent the occurrence of aliasing in order to acquire and reproduce the waveform of this λ / 2 period, normally, since three data are required in that period, it is faster than λ / (2 × 3). It is necessary to acquire data at repeated timing.

  In the present invention, since data is acquired at the timing when aliasing occurs, the shooting timing by the camera 10 and the storage timing of the memory 13 are slower (longer) than λ / 6 (hereinafter referred to as “sampling timing Fs”). There is.) Specifically, if the speed at which the optical path length control means 16 drives the piezo 8 to change the optical path length is v, the optical path length control means 16 sends a control signal with a time interval slower than λ / 6v to the camera 10 and the memory. The data is acquired at the timing of the control signal. When the optical path length control means 16 drives the piezo 8 in steps instead of analog, it generates a timing signal with a time interval earlier than λ / 6v and instructs the piezo 8 to change the optical path length.

  Eventually, the memory 13 stores imaging data using the time interval of the timing signal as an address. These timing progression directions (that is, address directions) represent the optical path length direction (Z-axis direction). At that time, the imaging data is stored together with the measurement position (Xm, Yp). The information on the measurement position (Xm, Yp) is the position of the pixel in the XY direction corresponding to the position of the image sensor of the camera 10. FIG. 2 shows an example of interference fringes obtained from the data stored in the memory 13 by the processing of the signal processing means 20 described below.

The signal processing means 20 includes an optical path length detection means 14 and a displacement calculation means 15.
As shown in FIG. 1, the optical path length detector 14 includes an interference fringe data selector 14a and an optical path length calculator 14c. The interference fringe data selection unit 14a receives imaging data from the memory 13, for example, data of measurement positions (Xm, Yp), and converts the data into frequency domain data by FFT. Then, as shown in FIG. 7 (E), since there are each data of the frequency component due to aliasing (dotted line portion in FIG. 7 (E)) and the original interference fringe frequency component data, they are separated by a filter and the frequency component due to aliasing is present. The interference fringe component (solid line part in FIG. 7E) is separated and extracted.

  Thereafter, the interference fringe data selection unit 14a returns the scale to the original frequency axis, that is, the frequency axis of the frequency domain when sampling is performed at the sampling timing at the time of data acquisition so as not to cause aliasing ( Since it is amplified at a frequency lower than the original sampling frequency, the frequency axis is expressed in a frequency-divided form, so it is returned.) Re-converted into time-domain data, that is, interference fringe data To the optical path length calculation unit 14c (FIG. 2 shows interference fringe data at that time).

  In the waveform of the interference fringes in FIG. 2, the peak position at the center of the interference fringe, which is the characteristic value of the interference fringes, is when the optical path length of the reference optical path and the optical path length of the measurement optical path are the same. In addition, the wavelength of the interference fringes due to the white light is made by combining the wavelengths that are the elements of the broadband light, and becomes half the wavelength λ at the center of those bands. Further, the spread of interference fringes in the optical path length direction due to white light in FIG. 2, that is, the width Δt of the envelope of the interference fringes depends on the degree of coherency of white light, in other words, the width ΔF of the frequency component in the frequency domain. The lower the coherency, that is, the smaller ΔF, the narrower the width Δ (see FIGS. 7A and 7B). If the maximum frequency of the interference fringe frequency component is Fh, the frequency component width ΔF satisfies ΔF << [1 / (λ / 2)] <Fh, and the width ΔF is reduced (to improve coherency). Since the amplitude of the interference fringe becomes substantially constant and the peak disappears, the width ΔF is determined so that the interference fringe width Δt is such that the peak value of the interference fringe can be grasped. For example, if the bandwidth of the light source 1 is determined so that the width ΔF is less than the maximum frequency Fh / 2 while being described as a model, as shown in FIG. 7E, the right half in the frequency band after sampling is shown. It is possible to extract only the actual frequency component of the interference fringe by a high-pass filter that is divided into the actual frequency component of the interference fringe and the frequency component due to aliasing in the left half and cuts Fh / 2.

  The optical path length detection means 14 obtains the peak position of the interference fringes and determines the optical path length at that position (specific optical path length). “Peak position” (or “peak position”) is a position on the horizontal axis where the luminance (amplitude) of interference fringes due to white light is maximum (hereinafter referred to as “peak”). 2, the horizontal axis is the optical path length direction of the measurement optical path (Z-axis direction: the vertical direction of the drawing in FIG. 1), and the time axis direction when the optical path length is variable (images are taken by the camera 10 at predetermined time intervals). Time axis direction).

  On the other hand, the imaging data stored in the memory 13 is stored at the timing (sampling timing) stored in the memory 13 (FIG. 2 is a continuous representation by connecting them), so the optical path length. The detection means 14 receives discrete data about interference fringes from the interference fringe data selection unit 14a. Because of this discrete nature, the maximum point of the amplitude and the peak position of the envelope may not match, but because of the smooth characteristics, the peak position of the envelope is obtained by interpolation from the front and rear maximum points of the amplitude. May be. For example, as a method of obtaining the peak of interference fringes from discrete imaging data, the optical path length is changed stepwise, and the following processing is performed based on the discrete imaging data taken for each of the changed predetermined optical path lengths. There is technology to do. A direct current component is excluded from the interference fringe data obtained from the imaging data by a digital high-pass filter. The AC component is squared and rectified. Integration is performed through a digital low-pass filter that passes a repetitive component lower than the rectified repetitive component, and envelope data of interference fringes is calculated. At this time, according to a request for the fineness of the peak position, the rectified repetitive components are interpolated with, for example, a square characteristic, and the interpolated repetitive components are integrated to obtain envelope data. The position that becomes the peak of the envelope data is obtained. Regardless of the timing (time interval) of the imaging data and the period of the interference fringes, the signal processing means 20 may obtain the peak position by discrete processing as described in JP-A-9-318329.

  The displacement calculation means 15 is the optical path length of the peak position of the interference fringes at each measurement position in the measurement range of the object 7 to be measured, that is, each specific optical path length, for example, the specific wavelength at the measurement position (Xm, Yp) in FIG. From the difference t0-t1 between the specific wavelength t0 at the reference measurement position (Xs, Ys), which is obtained in the same manner, the displacement of the shape of the object to be measured at the measurement value with respect to the reference measurement position is obtained.

[Second Embodiment]
This will be described with reference to FIGS. 3, 4 and 5 (however, FIG. 4 is also a diagram for explaining the operating principle). In the second embodiment, the peak position of the interference fringes is obtained from the amplitude in the first embodiment of FIG. Is obtained as the specific optical path length. The signal processing means 20 in FIG. 1 is replaced with the signal processing means 20a in FIG. 3, and the camera 10 in FIG. 5 is replaced with a color camera. Accordingly, in FIG. 1, a light source 1 is a light source that includes components in a wavelength band of at least two waves in a large number of wavelength components over a wide band, and here, for example, a light source that includes wavelength bands of red and green colors. Use. You may combine and use the light of the wavelength of each color of red and green. Other configurations, operations, timings, and the like other than the signal processing means 20a are the same as those in FIG. Hereinafter, the signal processing means 20a will be described.

  The interference fringe data selection unit 14e in FIG. 3 is basically the same as the interference fringe data selection unit 14a in FIG. 1, but is also one of the main configurations of the present invention, and will be described with reference to FIG. Since the interference fringe data selection unit 14e acquires data at the timing when the camera 10 and the memory 13 cause aliasing as described above (timing longer than λ / 6), the time-domain data from the memory 13 is acquired. It converts into frequency domain data by FFT, filters the unnecessary component by the aliasing, acquires the frequency component of the interference fringe, returns the frequency axis to the original, and sends it to the wavelength selection unit 14d.

  The interference fringe data selection unit 14e selects the right half data (data shown in light gray in FIG. 4D) as desired data from the obtained data of FIG. Unnecessary components in the previous frequency band are removed. Then, the frequency axis in FIG. 4D is expanded (the right half indicated by the gray area in FIG. 4E) and returned to the wavelength selection unit 14d.

  Here, a general principle will be described with reference to FIG. FIG. 4A shows interference fringes due to red and green wavelength components, and is an example when measured at normal sampling timing T0 (timing earlier than λ / 6v). FIG. 4B shows data converted into the frequency domain of FIG. In this case, the left half data is selected by the filter and used. As in the present invention, for example, when data acquisition (sampling) is performed at half the normal sampling timing T0 and at the timing when aliasing occurs, data in the time domain as shown in FIG. 4C is used instead of FIG. Is obtained. As the data in the frequency domain, instead of the data in FIG. 4B, data in which the left and right distributions are interchanged as compared with the distribution of the frequency components in FIG. 4B as shown in FIG. 4D is obtained. That is, an unnecessary component on the right side of FIG. 4B appears at the frequency position on the left side of FIG. 4D due to aliasing, and the original interference fringe component on the left side of FIG. 4B is the right side of FIG. 4D. Appears at the frequency position. The frequency axis in FIG. 4D is halved in relation to the sampling frequency compared to the frequency axis in FIG. Therefore, since the left component waveform in FIG. 4B and the right component waveform in FIG. 4D are the same, if they are separated by a filter and the scale is changed as shown in FIG. The data of the frequency component in the left half of FIG. 4 (B) can be obtained.

  In FIG. 3, the wavelength selection unit 14 d receives the frequency domain data transmitted from the interference fringe data selection unit 14 e and filters, for example, with a frequency of blue (B) component, green (G) component, red ( R) The components are classified into three components, and each component is sent to the optical path length extension unit 14f. In the optical path length calculation unit 14f, each of the B phase calculation unit 14f1, the G phase calculation unit 14f2, and the R phase calculation unit 14f1m obtains a phase change of a corresponding component in the time domain (for example, obtains a phase by orthogonal demodulation) .) FIG. 5 shows each phase change (vertical axis) with respect to a change in optical path length (horizontal axis). Then, as shown in FIG. 6, the optical path length determination unit 14f4 determines the optical path length in which the phases of the three components coincide with each other as the specific optical path length at the measurement position. At this time, since the data is discrete, when it is difficult to specify the optical path length of the phase coincidence point, a method such as interpolation as described above is used.

  Among the above configurations, the signal processing means 20 and 20a and the optical path length control means 16 can be constituted by a CPU and a memory.

  As described above, since data can be acquired and measured at the timing when aliasing occurs, the number of times of data acquisition can be reduced. Therefore, if the main measurement time is represented by [variable optical path length + number of data acquisition times × (exposure time + acquisition processing time)], the measurement time can be shortened by the reduction in the number of data acquisition times.

It is a figure which shows the function structure of 1st Embodiment. It is a figure for demonstrating an interference fringe. It is a figure which shows 2nd Embodiment which changed the optical path length detection means of FIG. It is a figure for demonstrating operation | movement of the interference fringe data selection part of FIG. It is a figure for demonstrating operation | movement of the optical path length variable means of FIG. 3, and shows the interference fringe of each frequency component. FIG. 4 is a diagram for explaining the operation of the optical path length varying unit in FIG. 3 and shows the phase characteristics of each frequency component. It is a figure for demonstrating the operation | movement which calculates | requires an interference fringe except the influence of aliasing in 1st Embodiment. It is also a diagram for explaining the background of the present invention in the column “Problems to be Solved by the Invention”.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Collimator lens 3 Beam splitter 4 Objective lens 5 Beam splitter 6 Reference mirror 7 Measured object 8 Piezo 9 Imaging lens 10 Camera 13 Memory 14 Optical path length detection means 14a, 14e Interference fringe data selection part 14d Wavelength selection part 14, 14f Optical path length calculation unit 15 Displacement calculation means 16 Optical path length control means 18 User interfaces 20, 20a Signal processing means

Claims (5)

  A broadband light source (1) that outputs broadband light having a plurality of spectrums, and the broadband light is branched and incident on a reference optical path having a reference mirror and a measurement optical path on which an object to be measured is arranged, and reflected from the reference mirror An optical path forming unit (5) for combining and outputting the light and each reflected light from the irradiation position of the irradiation range of the object to be measured, and the optical path length of either the reference optical path or the measurement optical path The optical path length varying means (8) for changing the optical path, and the interference path including interference fringes by imaging the output from the optical path forming section at the timing when aliasing occurs with respect to the change in the optical path length by the optical path length varying means. An imaging unit (10) for acquiring fringe data, and a specific light when the interference fringe data output from the imaging unit excludes a frequency component generated by the aliasing and indicates a characteristic value of the interference fringe And an optical path length detecting means (14) for determining the length, obtained based on 該特 constant light path length, the three-dimensional shape measuring apparatus characterized by measuring the shape of the object to be measured.   The timing at which the aliasing occurs with respect to the change in the optical path length by the optical path length varying means is defined as λ when the change in the optical path length by the optical path length varying means is approximately the center wavelength of the broadband light. The three-dimensional shape measuring apparatus according to claim 1, wherein the distance exceeds / 6.   The image pickup means picks up an image with a specific minimum exposure time, and when the speed at which the optical path length changing means changes the optical path length is v, a time interval in which the change in the optical path length exceeds λ / (6v) The three-dimensional shape measuring apparatus according to claim 2, wherein imaging is performed as the timing.   The optical path length detection means converts the interference fringe data output from the imaging means into frequency domain data, and the imaging means removes unnecessary components due to the aliasing in acquiring the data to obtain new interference fringes. An interference fringe data selection unit (14a) for selecting data, and an optical path length calculation unit (14c) for obtaining the specific optical path length representing the feature value based on the new interference fringe data The three-dimensional shape measuring apparatus according to claim 1, 2 or 3. The optical path length detection means includes a wavelength selection unit (14d) that extracts at least two wavelength components from the new interference fringe data selected by the interference fringe data selection unit,
The three-dimensional shape measurement according to claim 4, wherein the optical path length calculation unit obtains the optical path length at which a phase difference between the extracted at least two wavelength components is substantially zero as the specific optical path length. apparatus.