JP4885154B2 - Method for measuring surface shape by multiple wavelengths and apparatus using the same - Google Patents

Description

  The present invention provides a plurality of wavelengths for measuring unevenness of a measurement object having flatness such as a semiconductor wafer, a liquid crystal panel, a plasma display panel, a magnetic film, a glass substrate, and a metal film using a plurality of monochromatic lights having different wavelengths. The present invention relates to a method for measuring a surface shape by means of and a device using the same.

  Conventionally, the method of measuring the surface shape of the surface to be measured is performed as follows. The first monochromatic light and the second monochromatic light having different wavelengths are output at individual timings, and each monochromatic light is irradiated to the surface of the wafer, which is the measurement object, and the reference mirror by the beam splitter, and reflected from both to return. The reflected light is again collected by the beam splitter, and interference fringes are generated through the same optical path. At this time, the reflected light for each monochromatic light is detected by the two-dimensional image detector. The detected reflected light appears as interference fringes, and the interference fringes shift at the stepped portion of the surface. That is, the step difference of the pattern of the wafer is obtained based on the shift amount of the portion where the shift amounts are close among the shift portions of the continuous interference fringes generated by both monochromatic lights (see Patent Document 1).

JP 2002-340524 A

  However, the conventional method has the following problems.

  When the surface step of the measurement object is imaged, the interference fringe portion displayed on the display screen shifts at the steep step portion, so that the presence or absence of the step can be determined. However, when the state of the step is unknown, it cannot be determined whether the step at the shifted portion of the interference fringe has a convex shape or a concave shape. Therefore, the sharp edge portion of the measurement target surface cannot be obtained accurately.

  Moreover, since each interference fringe cannot be detected unless monochromatic light of different wavelengths is irradiated at different timings, it takes time to measure the step and shape of the entire surface of the measurement object. That is, if the monochromatic light cannot be continuously scanned over the entire surface of the measurement object, the monochromatic light cannot be continuously scanned over a plurality of measurement objects.

  The present invention has been made in view of such circumstances, and a method for measuring a surface shape by a plurality of wavelengths and an apparatus using the same capable of accurately measuring uneven steps on the surface of a measurement object at high speed. The main purpose is to provide

The first invention irradiates the measurement target surface and the reference surface with monochromatic light via the branching unit, and reflects the intensity of the interference fringes generated by the reflected light that is reflected from both the measurement target surface and the reference surface and returns on the same optical path. Based on the surface shape measurement method with multiple wavelengths to obtain the surface height and surface shape of the measurement target surface,
An image of interference fringes generated by arranging the reference surface in an inclined posture at an arbitrary angle with respect to the light traveling direction and simultaneously irradiating the measurement object and the reference surface with a plurality of monochromatic lights having different wavelengths is obtained. The first process,
A second step of obtaining the intensity value of the interference fringe of each pixel in the acquired image for each monochromatic light;
For each of the pixels using an expression for obtaining an interference fringe waveform, the intensity value of each pixel and the intensity values of a plurality of neighboring pixels are used, and the DC component, the AC amplitude of the interference fringe waveform at those pixels, and Assuming that the phases are equal, a third process for determining the phase of each pixel for each monochromatic light;
A fourth step of obtaining a surface height candidate group from the phase of each pixel obtained for each monochromatic light, and obtaining a common height as an actual height from each wavelength candidate group;
A fifth step of obtaining the surface shape of the measurement object from the obtained actual height;
It is provided with.

  (Operation / Effect) According to the surface shape measuring method according to the first aspect of the present invention, a plurality of monochromatic lights having different wavelengths are simultaneously irradiated onto the measurement object and the reference surface, and the reference surface is at an arbitrary angle with respect to the light traveling direction. Are arranged in an obliquely inclined posture, and interference fringes are generated for each monochromatic light by the reflected light returning from the measurement target surface and the reference surface on the same optical path. The intensity value of this interference fringe is obtained in units of pixels for each monochromatic light. Then, for each pixel, using the expression for obtaining the interference fringe waveform, the intensity value of each pixel and the intensity value of the neighboring pixel for each pixel are used, and the DC component of the interference fringe waveform included in each pixel Assuming that the AC amplitude and phase are equal, the phase of each pixel is determined for each monochromatic light. At this time, the direct current component and the alternating current amplitude in each pixel can be canceled, and there is no need to perform low-pass filter processing for removing the spatial frequency component. Therefore, it is possible to accurately obtain the edge portion of the steep portion of the measurement coping surface without reducing the spatial resolution.

  A candidate group for the surface height of the measurement object is obtained for each monochromatic light from the obtained phase, and a common height is obtained from each candidate group as an actual height. Therefore, the actual height can be accurately obtained from a wider candidate range than the surface height is obtained from a single phase, and the upper limit of the height that can be measured by the combination of wavelengths used can be increased.

  In addition, since it is possible to simultaneously output a plurality of monochromatic lights and simultaneously detect the reflected light composed of these monochromatic lights to measure the surface height and surface shape of the measurement object, it is possible to obtain measurement results under the same conditions. Can do. In other words, it becomes difficult to be affected by disturbances such as vibration. Furthermore, the work efficiency can be improved.

A second invention is a method for measuring a surface shape according to the first or second invention,
The first to fifth processes are repeated for each measurement pair position at predetermined time intervals while relatively moving the light directed to the measurement object and one or more measurement objects, and the measurement object It is characterized by obtaining the surface shape of an object.

  (Operation / Effect) According to this method, the surface height and the surface shape of the measurement object can be obtained in real time while continuously irradiating the entire surface of the measurement object with monochromatic light.

A third invention is a method for measuring a surface shape according to the first invention,
The obtained phase for each wavelength is obtained by fitting the intensity value g (x, y) of each pixel to an expression of the interference fringe waveform in the vicinity of the pixel g (x, y) = a + bcos {2πf _x x + 2πf _y y + φ}. It is characterized by obtaining from the above.

(Function / Effect) According to this method, the intensity value g (x) of each pixel is fitted to the expression fringe waveform g (x, y) = a + bcos {2πf _x x + 2πf _y y + φ} in the vicinity of the pixel. Thus, the phase of each pixel can be easily obtained. That is, the first invention can be preferably implemented by using a simple arithmetic expression.

4th invention is the surface shape measuring method which concerns on either 1st thru | or 3rd invention,
The image of the interference fringes is captured by an imaging unit having a filter that separates a plurality of monochromatic lights,
Intensity values of interference fringes of other monochromatic light included in each monochromatic light are removed by the influence of crosstalk caused by the filter characteristics.

  (Operation / Effect) According to this method, it is possible to remove the intensity value of the interference fringes of other unnecessary monochromatic light generated by the filter characteristics included in the monochromatic light to be measured. Therefore, the surface shape of the measurement object can be obtained with high accuracy.

According to a fifth aspect of the present invention, the intensity of interference fringes generated by reflected light that irradiates the measurement target surface and the reference surface through the branching means and reflects from both the measurement target surface and the reference surface and returns on the same optical path. Based on the surface shape measuring device with multiple wavelengths to obtain the surface height and surface shape of the measurement target surface,
The reference surface is arranged in an inclined posture at an arbitrary angle with respect to the traveling direction of light,
Holding means for placing and holding the measurement object;
Illumination means for simultaneously outputting a plurality of monochromatic lights having different wavelengths;
An imaging unit that images the measurement target surface by generating interference fringes for each monochromatic light by reflected light that is irradiated with the plurality of monochromatic lights and reflected from the measurement object and the reference surface and returns on the same optical path;
Sampling means for capturing the measured measurement target surface as an interference fringe intensity value for each pixel;
Storage means for storing an interference fringe intensity value group that is the intensity value captured by the sampling means;
The intensity value is read out for each pixel from the intensity value group stored in the storage means, and the intensity value of each pixel and the intensity value of a neighboring pixel are used for each pixel, and the DC of the interference fringe waveform included in each pixel Assuming that the components, AC amplitude, and phase are equal, using the expression for obtaining the interference fringe waveform, obtain the phase of each pixel for each monochromatic light,
Obtain a plurality of surface height candidate groups from the phase of each pixel obtained for each monochromatic light, obtain the common height from each candidate group as the actual height,
Further, a calculation means for obtaining a surface shape from the obtained surface height of the measurement target surface,
It is provided with.

Further, the tenth invention irradiates the measurement target surface and the reference surface with monochromatic light via the branching means, reflects the interference fringes generated by the reflected light that is reflected from both the measurement target surface and the reference surface and returns on the same optical path. In the surface shape measuring device with multiple wavelengths to obtain the surface height and surface shape of the measurement target surface based on the value,
The reference surface is arranged in an inclined posture at an arbitrary angle with respect to the traveling direction of light,
Holding means for placing and holding the measurement object;
Illuminating means for outputting light having a plurality of wavelengths;
Separating means for separating the reflected light that is irradiated with the light and reflected from the measurement object and the reference surface and returns on the same optical path into a plurality of monochromatic lights having different wavelengths;
Imaging means for imaging the measurement target surface by generating interference fringes for each of the separated monochromatic lights;
Sampling means for capturing the measured measurement target surface as an interference fringe intensity value for each pixel;
Storage means for storing an interference fringe intensity value group that is the intensity value captured by the sampling means;
The intensity value is read out for each pixel from the intensity value group stored in the storage means, and the intensity value of each pixel and the intensity value of a neighboring pixel are used for each pixel, and the DC of the interference fringe waveform included in each pixel Assuming that the components, AC amplitude, and phase are equal, using the expression for obtaining the interference fringe waveform, obtain the phase of each pixel for each monochromatic light,
From a plurality of surface height candidate groups obtained by conversion from the phase of each pixel obtained for each monochromatic light, obtain a common height as the actual height,
Further, a calculation means for obtaining a surface shape from the obtained surface height of the measurement target surface,
It is provided with.

  (Operation / Effect) According to these configurations, the holding means places and holds the measurement object. The illumination unit outputs a plurality of monochromatic lights having different wavelengths simultaneously. The imaging means images the measurement target surface by generating interference fringes by reflected light that is irradiated with a plurality of monochromatic lights, reflected from the measurement target and the reference surface, and returned on the same optical path. The sampling means captures the imaged measurement target surface as an interference fringe intensity value for each pixel. The storage means stores an interference fringe intensity value group that is an intensity value captured by the sampling means. The calculation means reads the intensity value for each pixel from the intensity value group stored in the storage means, and uses the intensity value of each pixel and the intensity value of the neighboring pixel for each pixel, and the interference fringes included in each pixel Assuming that the DC component, AC amplitude, and phase of the waveform are equal, the expression of the interference fringe waveform is used to obtain the phase of each pixel for each monochromatic light, and from the phase of each pixel obtained for each monochromatic light A plurality of candidate groups for the surface height are obtained, a common height is obtained from each candidate group as an actual height, and a surface shape is obtained from the obtained surface height of the measurement target surface.

  In other words, a plurality of monochromatic lights having different wavelengths can be simultaneously irradiated onto the measurement object and the reference surface, and a plurality of surface height candidate groups can be obtained for each different wavelength from reflected light returning from the same optical path. . Further, a common height is obtained from each candidate group and is set as an actual height. Therefore, an accurate surface height can be obtained from a wide candidate range. As a result, the surface height of the measurement object can be obtained from the obtained plurality of surface heights. That is, the first invention can be suitably realized.

  In the above configuration, the illuminating means may be configured to have, for example, a plurality of single color light sources that output different wavelengths, or a predetermined different plurality of white light sources and light output from the white light sources. It is also possible to configure it with optical means for separating the light into monochromatic light having a wavelength of 1 and directing it to the branching means.

  According to this configuration, it is possible to realize a configuration that easily irradiates the measurement object and the reference surface with monochromatic light having different wavelengths.

  In addition, the illumination unit uses a device that outputs light having a plurality of wavelengths, and a separating unit (for example, a filter) that separates the light into a plurality of monochromatic lights having different wavelengths is provided in or in front of the imaging unit. It may be configured. At this time, it is more preferable that the calculation means removes the intensity value of the interference fringes of other monochromatic light included for each monochromatic light due to the influence of crosstalk caused by the filter characteristics. According to this configuration, the intensity value of the interference fringes of the monochromatic light to be measured can be obtained with high accuracy, and the surface shape of the measurement target can be obtained with high accuracy.

A twelfth aspect of the invention is the surface shape measuring apparatus according to the fifth to eleventh aspects of the invention,
The calculation means obtains the intensity value g (x) of each pixel by fitting it to the expression of interference fringe waveform in the vicinity of the pixel g (x, y) = a + bcos {2πf _x x + 2πf _y y + φ}. Features.

(Operation / Effect) According to this configuration, the intensity value g (x) of each pixel is fitted to the interference fringe waveform expression g (x, y) = a + bcos {2πf _x x + 2πf _y y + φ} in the vicinity of the pixel. Thus, the phase of each pixel can be easily obtained. That is, the third method invention can be suitably realized.

  According to the surface shape measuring method using a plurality of wavelengths and the apparatus using the same according to the present invention, interference fringes are generated by reflected light returning from the same optical path from a reference surface having an arbitrary oblique inclination and a substantially flat measurement target surface. Thus, an intensity value for each pixel is obtained. Then, using the expression for obtaining the interference fringe waveform, the intensity value of each pixel and the intensity value of the neighboring pixel for each pixel, the DC component, AC amplitude, and phase of the interference fringe waveform included in each pixel are equal. And the phase of each pixel is obtained. Therefore, the DC component and AC amplitude of the interference fringe waveform in each pixel can be canceled. As a result, it is not necessary to perform a filtering process such as a low-pass filter process for removing the spatial frequency component. In addition, it is possible to avoid a decrease in spatial resolution caused by the filtering process, to accurately obtain the sharp edge portion of the measurement target surface, and to accurately obtain the uneven step on the measurement target surface.

  Further, by obtaining a plurality of surface height candidate groups obtained from the phase for each monochromatic light, and further obtaining the common surface height actual height from each candidate group, the measurement accuracy can be improved. Moreover, the upper limit of the height which can be measured can be raised by increasing the candidate of surface height.

  In addition, while simultaneously irradiating the measurement object and the reference surface with a plurality of monochromatic lights of different wavelengths through the branching means, the phase for each pixel for each wavelength is obtained in real time, and the surface height of the measurement object is calculated from this phase. And surface shape can be measured in real time. Therefore, measurement results under the same conditions can be obtained. In other words, it becomes difficult to be affected by disturbances such as vibration.

  Furthermore, the height and the surface shape can be continuously measured for the entire surface of one measurement object, and the measurement process can be continuously performed over a plurality of measurement objects. As a result, the processing time can be shortened. That is, work efficiency can be improved.

  Embodiments of the present invention will be described below with reference to the drawings. In the present embodiment, a surface shape measuring apparatus that measures the surface height and the surface shape of a measurement object having a substantially flat surface using interference fringes will be described as an example.

  FIG. 1 is a diagram showing a schematic configuration of a surface shape measuring apparatus according to an embodiment of the present invention.

  This surface shape measuring apparatus is a monochromatic light of a specific wavelength band on a substantially flat measuring object 30 having fine uneven steps on the surface of a semiconductor wafer, a liquid crystal panel, a plasma display panel, a magnetic film, a glass substrate, a metal film or the like. Is provided with an optical system unit 1 that irradiates the optical system unit 1, a control system unit 2 that controls the optical system unit 1, and a holding table 40 that places and holds the measurement object 30.

  The optical system unit 1 includes an illumination device 10 that outputs monochromatic light having a plurality of different wavelengths toward the measurement target surface 30A and the reference surface 15, a collimator lens 11 that converts each monochromatic light into parallel light, and both monochromatic lights to be measured. The half mirror 13 that reflects light from the direction of the measurement object 30 while reflecting in the direction of the object 30, the objective lens 14 that condenses the monochromatic light reflected by the half mirror 13, and the objective lens 14 The monochromatic light thus transmitted is divided into reference light reflected to the reference surface 15 and measurement light passed to the measurement target surface 30A, and the reference light reflected on the reference surface 15 and measurement light reflected on the measurement target surface 30A. Are combined again to generate interference fringes, an imaging lens 18 that forms monochromatic light in which the reference light and the measurement light are collected, and the measurement target surface 3 together with the interference fringes. And an imaging device 19 for imaging the A.

The illumination device 10 includes a first light source 10A and a second light source 10B that output light of two different wavelengths, and an optical member 10C that aligns both lights output from different directions in the same direction. As each light source 10A, 10B of the present embodiment, for example, an LED (Light Emitting Diode) is used and, for example, outputs light of the next wavelength. The first light source 10A has a wavelength λ ₁ = 470 nm, and the second light source has a wavelength λ ₂ = 627 nm. The lighting device 10 corresponds to the lighting means of the present invention.

  The half mirror 13 reflects the parallel light from the collimator lens 11 toward the measurement object 30, while allowing the reflected light returned from the measurement object 30 to pass therethrough.

  The objective lens 14 is a lens that condenses the incident monochromatic light on the measurement target surface that has the focal point.

  The beam splitter 17 divides the light collected by the objective lens 14 into reference light that is reflected by the reference surface 15 and measurement light that is reflected by the measurement target surface 30A. In addition, interference is generated by regrouping the reference light and the measurement light that are reflected from each surface and return on the same optical path. The beam splitter 17 corresponds to the branching means of the present invention.

  The reference surface 15 has a mirror-finished surface, and is attached in an obliquely inclined posture in the front-rear direction with respect to the traveling direction of the reference light. The reference light reflected by the reference surface 15 reaches the beam splitter 17, and the reference light is reflected by the beam splitter 17.

In addition, by attaching the reference surface 15 in a slanting posture in front and back with respect to the traveling direction of the reference light, the reach distance of the reference light and the distance until the reflected light reaches the imaging device 19 vary depending on the position of the reflective surface. To do. This is equivalent to moving the reference surface 15 and changing the distance L ₁ between the reference surface 15 and the beam splitter 17.

  That is, the measurement light that has passed through the beam splitter 17 is collected toward the focal point and reflected by the measurement target surface 30A. The reflected measurement light reaches the beam splitter 17 and passes through the beam splitter 17.

The reference beam and the measurement beam are combined again by the beam splitter 17. At this time, an optical path difference is generated due to a difference between the distance L ₁ between the reference surface 15 and the beam splitter 17 and the distance L ₂ between the beam splitter 17 and the measurement target surface 30A. The reference light and the measurement light interfere with each other according to this optical path difference.

  The imaging device 19 captures an image of the measurement target surface 30A that is projected by the measurement light. At this time, because the reference surface 15 is tilted, an interference fringe that is a spatial variation in luminance due to interference is captured in the captured image of the measurement target surface 30A. The captured image data is collected by the memory 21 of the control system unit 2. Further, as will become clear later, the drive unit 24 of the control system unit 2 is configured to move the optical system unit 1 in the x, y, and z axis directions in FIG. In addition, the imaging device 19 captures images of the measurement target surfaces 30 </ b> A and 30 </ b> B at a predetermined sampling timing, and the image data is collected by the control system unit 2. The imaging device 19 corresponds to the imaging means of the present invention, and the control system unit 2 functions as the sampling means of the present invention.

  The imaging device 19 in the present embodiment may be configured to detect a plurality of monochromatic lights having different wavelengths. For example, a CCD solid-state imaging device, a MOS image sensor, a CMOS image sensor, a photoelectric imaging tube, an avalanche electron multiplication effect imaging Tube, EB-CCD, etc.

  The control system unit 2 performs overall control of the entire surface shape measuring apparatus and CPU 20 for performing predetermined arithmetic processing, and various data and programs such as image data and arithmetic results sequentially collected by the CPU 20. A memory 21 to be stored, an input unit 22 such as a mouse or a keyboard for inputting other setting information such as a sampling timing and an imaging area, and a monitor 23 for displaying an image of the measurement target surface 30A and the like. Further, the optical system unit 1 is driven to move up, down, left and right in accordance with an instruction from the CPU 20. For example, it is configured by a computer system including a drive unit 24 configured by a drive mechanism such as a three-axis drive type servo motor. The CPU 20 corresponds to the calculation means in the present invention.

  The CPU 20 is a so-called central processing unit that controls the imaging device 19, the memory 21, and the drive unit 24, and based on the image data of the measurement target surface 30 </ b> A including the interference fringes captured by the imaging device 19. A phase calculation unit 25 that performs calculation processing for obtaining the surface height of the object 30 and an image data creation unit 27 that obtains a surface shape from a plurality of obtained surface height data are provided. The processing of the phase calculation unit 25 and the image data creation unit 27 in the CPU 20 will be described later. Further, a monitor 23 and an input unit 22 such as a keyboard and a mouse are connected to the CPU 20, and the operator can observe various operation information displayed on the monitor 23 from the input unit 22. Input. Further, the monitor 23 displays a surface image of the measurement target surface 30A, a concavo-convex shape, and the like as numerical values and images.

  The drive unit 24 is a device that moves, for example, the optical system unit 1 in the x, y, and z axis directions in FIG. 1 to a desired imaging location. The drive unit 24 is configured by a drive mechanism including, for example, a three-axis drive type servo motor that drives the optical system unit 1 in the x, y, and z axis directions according to instructions from the CPU 20. In the present embodiment, the optical system unit 1 is operated. For example, the holding table 40 on which the measurement object 30 is placed may be changed in the three orthogonal axes. Further, there may be two or less moving axes or none.

  Hereinafter, processing performed in the entire surface shape measuring apparatus, which is a characteristic part of the present embodiment, will be described with reference to a flowchart shown in FIG.

  In the present embodiment, the case where the reference surface 15 is inclined as shown in FIG. 1 will be described as an example. In this case, the captured image is as shown in FIG. In the present embodiment, the case of the x-axis direction will be described as an example in order to simplify the description.

<Step S1> Acquisition of Measurement Data The CPU 20 drives a drive system such as a stepping motor (not shown), and the drive unit 24 moves the optical unit 1 to the imaging region of the measurement object 30. When the imaging position is determined, the optical system unit 1 simultaneously outputs monochromatic lights λ ₁ and λ ₂ having different wavelengths from the light sources 10A and 10B of the illumination device 10. Both the monochromatic lights are collected by the optical member 10 c and directed to the half mirror 13.

The imaging device 19 operates in conjunction with the output of the monochromatic light, and for example, the measurement target surface 30A having the convex portion 30B shown in FIG. 1 is imaged once. Image data of the interference fringes of the measurement target surface 30 </ b> A obtained by this imaging is stored in the memory 21. That is, the memory 21 stores, for each monochromatic light, image data of interference fringes generated by the reflected light from the tilted reference surface 15 and the reflected light reflected by the measurement target surface 30A. At this time, the propagation distance of light reflected by the reference surface 15 (twice L ₁ ) varies regularly at the reflection position on the reference surface 15. Therefore, in the portion where the height of the measurement target surface 30A is flat, the propagation distance of reflected light from the measurement target surface 30A (twice L ₂ ) does not vary at the measurement location, and thus is imaged by the imaging device 19. Interference fringes in the image appear spatially and regularly in the imaging surface in accordance with the direction and angle of inclination of the reference surface 15. (2 times L ₁₎ and the difference is lambda _1/2 = 235 nm and the propagation distance of the reflected light from the object surface 30A (twice the L ₂₎ the interference fringes propagation distance of the reflected light from the reference surface 15 Every λ ₂ /2=313.5 nm appears for one period.

  On the other hand, as shown in FIG. 1, in the portion where the height of the measurement target surface 30 </ b> A fluctuates, an irregular fringe pattern in which interference fringes are shifted appears.

  This process corresponds to the first process in the present invention.

<Step S2> Acquisition of Interference Light Intensity Value Group The CPU 20 takes in the intensity value of each pixel stored in the memory 21, that is, the intensity value of the interference light on the measurement target surface 30A from the image data. At this time, the spatial phase of the interference fringes is near the pixel numbers 200 and 330 shown in FIG. 4 where the heights of the measurement target surface 30A and the convex portion 30B vary (for example, in the X-axis direction in this embodiment of FIG. 4). ) Appears as misaligned irregular stripes.

  This process corresponds to the second process in the present invention.

<Step S3> Calculation of Phases φ1 and φ2 in Pixel Units for Each Wavelength The phase calculation unit 25 of the CPU 20 determines the phase of the pixel to be calculated on the measurement target surface 30A as a pixel adjacent to the pixel (this embodiment) In the example, it is obtained by using a calculation algorithm determined in advance using the light intensity value of each interference fringe (pixel adjacent in the x-axis direction). Specifically, the light intensity value of the interference fringe in the pixel to be calculated and the pixel adjacent to the pixel is applied to an expression for obtaining the interference fringe waveform (fitting) to obtain the phase.

  First, the intensity value of the interference fringe light in the pixel to be calculated is described as the following equation (1).

  g (x) = a (x) + b (x) cos {2πfx + φ (x)} (1)

  Here, x is the position coordinate of the pixel to be calculated, a (x) is a direct current component included in the interference fringe waveform, b (x) is an alternating current component (amplitude of vibration component) included in the interference fringe waveform, and (Referred to as “AC amplitude” as appropriate), f is a spatial frequency component of the interference fringe g (x), and φ (x) is to be calculated with a phase corresponding to a predetermined pixel of the measurement target surface 30A. Note that the position coordinates of the pixel to be calculated are expressed in two dimensions (x, y), but in this embodiment, the y coordinates are omitted to simplify the description.

  Next, since adjacent pixels are shifted from the pixel to be calculated by a minute distance Δx in the x-axis direction, the light intensity value of the interference fringes is expressed by the following equation (2).

  g (x + Δx) = a (x + Δx) + b (x + Δx) cos {2πf (x + Δx) + φ (x + Δx)} (2)

  Here, in this embodiment, since the pitch between the pixel to be calculated and the adjacent pixel is a minute distance, it is assumed that the DC component, AC amplitude, and phase included in the interference fringe extending over each pixel are equal, and The relational expressions (3) to (5) are used.

a (x) = a (x + Δx) = a (3)
b (x) = b (x + Δx) = b (4)
φ (x) = φ (x + Δx) = φ (5)
Here, a, b, and φ are constants.

  Assuming the above (3) to (5), the expressions (1) and (2) can be replaced as the following expressions (1a) and (2a).

  g (x) = a + bcos (2πfx + φ) (1a)

  g (x + Δx) = a + bcos {2πf (x + Δx) + φ} (2a)

  Next, the equations (1a) and (2a) are modified to create the following equations (6) and (7).

  G (x) = g (x) −a = bcos (2πfx + φ) (6)

  G (x + Δx) = g (x + Δx) −a = bcos {2πf (x + Δx) + φ} (7)

  Next, equations (6) and (7) are transformed into the following equations (8) and (9) by the addition theorem.

G (x) = bcos (2πfx + φ)
= B {cos (2πfx) cosφ−sin (2πfx) sinφ} (8)

G (x + Δx) = bcos {2πf (x + Δx) + φ}
= B [cos {2πf (x + Δx)} cosφ−sin (2πfx + Δx) sinφ] (9)

  Next, these equations (8) and (9) are represented by a matrix (10).

A is expressed as follows.

  Here, the following equations (11) and (12) are obtained by multiplying the left side of the matrix (10) by the inverse matrix of A and expanding.

  By using these equations (11) and (12), the following equation (13) can be obtained. Here, bsinφ and bcosφ are set to bsinφ = S and bcosφ = C, respectively, and tanφ = S / C.

φ = arctan {S / C} + n′π (13)
Note that n ′ is an integer.

  Here, the CPU 20 further includes a code determination unit 26, and the code determination unit 26 refers to the code information of sinφ and cosφ. If this code information is used, the existence range of φ can be expanded from π to 2π from the combination of the codes of sinφ and cosφ. FIG. 5 is a specific diagram for specifying the range of φ with reference to the sign information of sin φ and cos φ as shown in equation (13). Therefore, using the sign information of sinφ and cosφ, equation (13) can be expressed by the following equation (14).

φ = arctan {S / C} + 2nπ (14)
Note that n is an integer.

Therefore, if G (x) and the spatial frequency f of the interference fringe waveform are known, the phase φ can be obtained by Expression (14). G (x) is composed of the luminance information g (x) and g (x + Δx) of the pixel and the direct current component a of the interference fringe waveform, so that g (x) and g (x + Δx), the direct current component a of the interference fringe waveform, interference If the spatial frequency f of the fringe waveform is known, φ can be obtained by the equation (14). That is, the respective phases φ1 and φ2 in the case of the wavelengths λ ₁ and λ ₂ are obtained by using the above arithmetic expressions.

  g (x) and g (x + Δx) can be obtained as luminance information of the pixels of the imaging device 19.

  For example, a can be obtained by a method of setting the average value of the luminance of all the pixels observed by the imaging device 19, a method of setting the average value of pixels near the phase calculation target pixel, or a method of measuring the reflectance in advance. .

  For example, f can be obtained by a method of obtaining from the installation angle of the reference surface 15 or a method of obtaining from the number of interference fringes in the screen of the interference fringe waveform when a flat surface is observed in advance as a measurement object.

  This process corresponds to the third process of the present invention.

<Step S4> Calculation of Surface Heights z ₁ and z ₂ in Pixel Units for Each Wavelength The CPU 20 calculates the phase φ ₁ of the calculation target pixel for each wavelength λ ₁ and λ ₂ from the above equation (14). Substituting x) and φ ₂ (x) into the following equation (15), the respective heights z ₁ (x) and z ₂ (x) are obtained.

z (x) = [φ (x) / 4π] λ + z ₀ (15)

Note that z ₀ is the reference height of the measurement object 30.

Here, when the wavelength is λ, there are surface height solution candidate value groups for each range of λ / 2. Therefore, each surface height solution candidate value group is in the range of lambda _1/2 and lambda _2/2 of the least common multiple of the two candidate values groups of two wavelengths lambda _1, when utilizing the lambda ₂ as in this embodiment Exists periodically.

  Since there is only one surface height to be obtained, a common height is obtained from both candidate value groups as the actual height. That is, among the solution candidate values for the surface height obtained in each candidate value group, the closest height is defined as the actual height.

For example, FIG. 6A shows a solution candidate value group of λ ₁ that periodically exists, and FIG. 6B shows a solution candidate value group of λ ₂ . Here, the portion corresponding to the bottom 30A of the measurement object 30 shown in FIG. 1 is from about 0 to 200 and 330 to 500 of the pixel number, and the convex portion 30B is from the vicinity of the central pixel number 200 to 330. . Therefore, both candidate value groups are compared for each pixel, and the ones whose surface heights of the bottom portion 30A and the convex portion 30B are substantially the same are extracted. That is, one of the bottom portion 30A, so that matches the height z ₁₁ and the wavelength lambda ₂ of the height z ₂₁ wavelengths lambda _1, the value of this time and the actual height. The other convex portion 30B since the height z ₁₃ and the multi-height z ₂₃ of the wavelength lambda ₂ wavelength lambda ₁ is substantially coincident, the value of this time and the actual height.

That is, based on this principle, the respective surface heights are obtained from the phases φ ₁ (x) and φ ₂ (x) measured at the wavelengths λ ₁ and λ ₂ by the following equations (15a) and (15b).

_{z 1 (x) = [φ} 1 (x) / 2π + n 1] · (λ 1/2) ··· (15a)
_{z 2 (x) = [φ} 2 (x) / 2π + n 2] · (λ 2/2) ··· (15b)

<Step S5> Calculate actual height Z in pixel units Further, the actual height Z is obtained by the following equation (15c) using the above two equations.

  Z = [Φ (x) / 2π + N] · (Λ / 2) (15c)

However, Φ = φ ₁ −φ ₂ ; (−π <Φ ≦ π), Λ = (λ ₁ λ ₂ ) / | λ ₁ −λ ₂ |, and N = n ₁ −n ₂ .

  This process corresponds to the fourth process in the present invention.

<Step S6> Completion of calculation for all pixels?
CPU20 repeats the process of step S3-S6 until the calculation of a phase and height is complete | finished about all the pixels, and calculates | requires a phase and surface height.

<Step S7> Display of Surface Shape The image data creation unit 27 of the CPU 20 creates display images of the measurement target surfaces 30A and 30B from the calculated actual surface height information. Then, based on the information created by the image data creation unit 27, the CPU 20 displays information on the surface height of the measurement object 30 on the monitor 23 as shown in FIG. A three-dimensional or two-dimensional image based on the height information is displayed. The operator can grasp the concavo-convex shape on the surface of the measurement target surface 30A by observing these displays. Thus, the measurement process of the surface shape of the measurement target surface 30A is completed.

  This process corresponds to the fifth process in the present invention.

  As described above, in the process of calculating the intensity value of the interference fringe light for each pixel and the intensity values of a plurality of neighboring pixels from the image data captured by the imaging device 19, the direct current included in the interference fringe waveform of each pixel. Canceling DC component and AC amplitude of interference fringes in each pixel by simultaneous comparison assuming that component a (x), AC amplitude b (x), and phase φ (x) are equal for each pixel be able to.

  Therefore, since the surface height of the measurement target surface 30A can be measured without using a low-pass filter, the surface height of the steep edge portion of the measurement target surface 30A is accurately obtained as shown in FIG. be able to. As a result, the surface shape of the measurement target surface 30A can be accurately measured.

In addition, a candidate value group for the surface height of the object to be measured is obtained for each monochromatic light from the obtained phase, and a common height is obtained from each candidate group as the actual height. The actual height can be obtained with high accuracy from a wider candidate range. Moreover, the upper limit of the height which can be measured with the combination of the wavelength to be used can be made high. For example, if the difference between the wavelengths λ ₁ and λ ₂ is reduced, a higher uneven step can be detected.

  Moreover, since the surface height of the measuring object 30 is calculated | required from a phase, the uneven | corrugated state of a surface can also be discriminate | determined.

  Furthermore, since the surface height and the surface shape of the measuring object 30 can be measured by simultaneously outputting and simultaneously detecting the reflected light composed of a plurality of monochromatic lights, the working efficiency can be improved.

  The present invention is not limited to the embodiment described above, and can be modified as follows.

  (1) In the above embodiment, the height of the measurement target surface 30A is obtained using the intensity value of the interference light of one pixel adjacent to the pixel to be calculated, but it is in the vicinity of the pixel to be calculated. Using two pixels, the height of the measurement target surface 30A may be obtained from a total of three pixels.

  In this case, three unknown variables can be obtained by solving a ternary simultaneous equation. Therefore, when compared with the case where the intensity value of the interference light of one pixel adjacent to the pixel to be calculated is used, one of the DC component a of the interference fringe waveform and the spatial frequency f of the interference fringe waveform is calculated. Can be added as an unknown variable.

When f is estimated by another method and a is added as an unknown variable, the intensity of interference light of a total of three pixels, that is, the pixel x + Δx ₁ and the neighboring pixels x + Δx ₂ and x + Δx ₃ are calculated. Using the value, the height of the predetermined pixel is obtained as in the following equation (16).

_{However, g 1 = g (x +} Δx 1), g 2 = g (x + Δx 2), which is _{g 3 = g (x + Δx} 3).

  Through the above arithmetic processing, the surface height of the predetermined pixel of the measurement target surface 30A can be obtained with high accuracy.

  In the present invention, the height of the measurement target surface 30A may be obtained using four or more neighboring pixels. In this case, since φ (x) is obtained on the basis of information on the intensity values of a large number of pixels, there is a feature that the influence of the measurement value on the luminance noise at the time of imaging and the quantization error at the time of calculation can be reduced.

That is, in the above-described embodiment apparatus, the phase calculation unit 25 of the CPU 20 determines the phase of the pixel x on the measurement target surface 30A to be obtained as the pixel x and a plurality (N) of pixels x + Δx _{i in} the vicinity of the pixel x. (i = 1, 2, 3,..., N) (in this embodiment, a plurality of pixels existing in the x-axis direction) is used to calculate the light intensity value of each interference fringe, using a predetermined calculation algorithm. I will ask. Specifically, the intensity value of the interference fringe light at the pixel x to be calculated is obtained by the following equation (17).

g (x + [Delta] _xi ) = a (x + [Delta] _xi ) + b (x + [Delta] _xi ) cos {2 [pi _] .f. (x + [Delta] _xi ) + [phi] (x + [Delta] _xi )} (17)

  In this case as well, as in the above-described embodiment, it is assumed that the DC component, AC amplitude, and phase included in the interference fringes of each pixel are equal, and the relational expressions (3) to (5) are applied. In the case of the present embodiment, the following expressions (18) to (20) are obtained.

a (x _i ) = a (x + Δx _i ) = a (18)
b (x _i ) = b (x + Δx _i ) = b (19)
φ (x _i ) = φ (x + Δx _i ) = φ (20)

  By assuming the above equations (18) to (20), the equation (17) can be expressed as the following equation (21).

g (x + Δx _i ) = a + bcos {2π · f · (x + Δx _i ) + φ}
= a + bcosφ · cos {2π · f · (x + Δx _i )} − bsinφ · sin {2π · f · (x + Δx _i )} (21)

  From these simultaneous equations of N elements, the DC component a, AC amplitude b, spatial frequency f, and phase φ of the interference fringe waveform are obtained by estimation by fitting. Here, the DC component a of the interference fringe waveform and the spatial frequency f of the interference fringe waveform may be obtained by another method as in the case of calculating the phase φ from two or three pixels.

  Next, an example will be described in which the spatial frequency f of the interference fringe waveform is estimated, and the DC component a of the interference fringe waveform is obtained by estimation by fitting.

  In particular, in the present modification, the calculation process for estimating the spatial frequency f is performed between step S2 and step S3 of the flowchart shown in FIG. That is, the overall flowchart of this modification is as shown in FIG. Therefore, first, the algorithm for estimating the spatial frequency f in step S3 will be described.

<Step S3> Estimation of Spatial Frequency f First, for example, the Prony method is used to estimate the spatial frequency f. That is, sampling is performed sequentially while correcting the sample point frequency fs from a plurality of equally spaced sample values acquired in advance. Finally, the spatial frequency f is estimated while converging to fs = 4f. Specifically, the following algorithm is used.

The spatial frequency f is obtained from the following equation (22) using four points of equidistant sample points x ₀ , x ₁ , x ₂ , x ₃ from a plurality of equidistant sample values acquired in advance.

f = (fs / 2π) acos [(x ₃ -x ₂ + x ₁ -x ₀ ) / {2 * (x ₂ -x ₁ )}] (22)

  Note that acos is an arc cosine.

  Here, the spatial frequency estimation accuracy by the Prony method increases as the sampling frequency fs approximates to four times the spatial frequency f to be estimated (fs = 4f). Therefore, the sampling frequency fs is converged to fs = 4f while being sequentially corrected.

  Since the sampling point interval t can only be an integer multiple of one pixel, the frequency when the ratio between the sampling frequency fs and the obtained spatial frequency f is closest to 4 is estimated as the spatial frequency f.

  In the present embodiment, the estimation of the spatial frequency f is executed as follows along the flowchart shown in FIG.

Set <Step S10>'provisional value fs of the sampling frequency to the initial value f ₁ set previously acquired sample point data' provisional value fs of the sampling frequency f1. Specifically, the sampling frequency f ₁ is set to be larger than twice the estimated frequency, and the sampling point interval t is set to be smaller than the Nyquist interval. For example, as shown in FIG. 10, the provisional sampling frequency f ₁ is set in a range where the sampling point interval t falls within ½ of the period T.

<Step S11> Calculation of sampling point interval t The sampling point interval t is calculated from the equation t = round (1 / fs'). Here, round means rounding to an integer.

<Step S12> Convergence determination The previously calculated interval t and the newly calculated interval t are compared, and when the calculated values are the same, it is determined that the interval has converged. For example, as shown in the red stripe experimental data in FIG. 11, when the calculation was repeated four times, the sampling point interval t changed in the order of 6, 9, 10, and 10. That is, it determines with having converged by the 4th calculation. In this way, when the newly calculated interval t becomes the same value as the previous interval t, the present process is terminated and the process proceeds to step S4. If the new interval t is not the same as the previous time, the process proceeds to the next step S13.

<Step S13> Calculation of Sampling Frequency fs When the interval t is determined, the sampling frequency fs is calculated as fs = 1 / t.

<Step S14> Calculation of Spatial Frequency f Four sample points x ₀ , x ₁ , x ₂ , x ₃ are selected at intervals t for each pixel in the region to be measured, and using equation (22) The spatial frequency f is calculated, and the average value over the entire region is calculated.

<Step S15> Calculation of Temporary Value fs ′ of New Sampling Frequency When the spatial frequency f is obtained, a temporary value fs ′ of a new sampling point frequency is calculated using the relationship of fs = 4f. When the provisional value fs ′ is obtained, the process returns to step S11, and the subsequent steps are repeated until the previous interval t coincides with the new interval t in step S12.

Next, the estimation of the spatial frequency f is terminated with respect to formula (21), satisfies the following equation (23) the intensity of a plurality of pixels values g a (x + [Delta] x _i) based on (a, bcosφ, bsinφ) Ask for a pair. Of these, φ may be obtained from (bcosφ, bsinφ).

Here, the following expressions (24), (25), and (26) are set.

  Next, α satisfying the equation (23) can be obtained as the following equation (27).

α = (A ^T・ A) ⁻¹・ A ^T・ G (27)

  Then, the phase φ can be obtained from the vector component of α using the following equation (28).

  From this equation (28), φ can be obtained in the same manner as equations (13) and (14) shown in the above embodiment.

  As described above, even if a plurality of neighboring pixels of the pixel are used for the pixel to be calculated, the height of the pixel can be obtained with high accuracy. In this modified embodiment, a plurality of neighboring pixels in the X-axis direction are used. However, the use pixels are not particularly limited, such as using pixels in the Y-axis direction.

(2) In the above embodiment, the description has been given using the neighboring pixels distributed on one axis in the X-axis or Y-axis direction, but neighboring pixels distributed on the XY plane may be used. In this case, for the pixel on the (x, y) coordinate to be calculated, the coordinates of the pixel in the vicinity of the pixel are solved as {(xi, yi)} (i = 1, 2,... N). The arithmetic processing may be performed by setting the above formula (1) as g (x, y) = a + bcos {2πf _x x + 2πf _y y + φ}.

  (3) In the above embodiment, the measurement object 30 is imaged in a stationary state. However, while moving a long measurement object or a plurality of measurement objects 30 at a predetermined speed, the movement speed is synchronized with the movement speed. Alternatively, the image of the measurement target surface 30A may be captured at a predetermined sampling time to obtain the surface height.

  (4) In the above embodiment, the average of candidate values may be calculated and used in the process of calculating the actual height from the surface height candidate value group obtained for each monochromatic light. Thereby, the solid error of the apparatus or the like can be canceled.

  (5) In the said Example, a white light source is utilized for the light source of the illuminating device 10, and the monochromatic light of different wavelengths is extracted from white light on the optical path until white light reaches | attains a measurement object surface and a reference surface. Optical means may be provided. Further, similar engineering means may be provided on the optical path until the reflected light reaches the imaging device 30. Further, each monochromatic light may be detected by an individual imaging device 19.

  (6) In the above embodiment, the surface height and the surface shape of one measuring object 30 are obtained, but the following configuration may be adopted. For example, all the measurement objects 30 can be conveyed while the plurality of measurement objects 30 are continuously conveyed along the conveyance path, or the plurality of measurement objects 30 aligned on the movable table are moved on the XY plane. You may comprise the thing 30 so that the surface height and surface shape may be calculated | required.

  (7) In the above-described embodiment, the measurement is performed by arbitrarily setting the angle of the reference surface 15 in a state where the parallelism of the measurement object 30 is maintained in advance. For example, a standard region having a known flatness and a flatness is provided on the measurement surface side of the measurement object 30, and after setting the angle of the reference surface 15, the height of this region is measured in advance. The inclination of the measurement object 30 is measured. Then, it may be configured to calculate the correction amount of the obtained slope and correct it using the result. Thereby, the spatial frequency component of the interference fringe waveform can be estimated.

  (8) In the above embodiment, two LEDs having different wavelengths are used as the light source. Instead of this LED, for example, Red (R) having a wavelength λ = 627 nm and Green (G) having a wavelength λ = 530 nm. ), And an RGB-LED made of Blue (B) having a wavelength λ = 470 nm may be used. In this case, as shown in FIG. 13, for example, the imaging device 19 uses a color camera including a filter that can separate reflected light from these three light sources into monochromatic light. In addition, the wavelength of each LED is not limited to the said value.

  Depending on the characteristics of the filter, as shown in FIG. 13, the separated monochromatic light includes light in the frequency band of other monochromatic light. That is, crosstalk occurs.

  Therefore, when a plurality of monochromatic lights having different frequency bands are used as in the modification, it is preferable to remove crosstalk that occurs during actual measurement.

  For crosstalk removal, a correction coefficient necessary for removing other monochromatic light contained in each separated monochromatic light is obtained in advance by experiments and simulations, and the intensity value for each pixel obtained by observation is corrected by the correction coefficient. Do.

  The correction coefficient can be obtained by the following method, for example.

  First, a crosstalk model and a correction formula will be described. In an image obtained by irradiating with an RGB-LED light source, the luminance signal I can be expressed by the following equation (29) depending on the additivity of luminance by individual irradiation of each light source.

  I (R, G, B) = I (R) + I (G) + I (B) (29)

  Here, it is considered that the true luminance (B, G, R) is obtained from the observed luminance (B ′, G ′, R ′) of each pixel. In this case, the observed luminance (B ′, G ′, R ′) of each monochromatic light includes the luminance of each light source due to the influence of crosstalk. Therefore, the relationship between the observed luminance and the true luminance can be expressed by the following model equations (30a) to (30c).

B ′ = B + aG + bR (30a)
G ′ = cB + G + dR (30b)
R ′ = eB + fG + R (30c)

  Here, a to f in the equations (30a) to (30c) are coefficients representing the magnitude of the crosstalk.

  From the formulas (30a) to (30c), the true luminance corresponding to each light source can be ignored when the coefficients are small, and the product terms of the coefficients can be ignored, and the following formulas (31a) to (31c) are approximated. Can be obtained.

B = B′−aG′−bR ′ (31a)
G = G′−cB′−dR ′ (31b)
R = R′−eB′−fG ′ (31c)

  Next, a method for obtaining the crosstalk magnitudes a to f will be described.

  First, each light source is turned on individually. At this time, RGB luminances output to the monitor are obtained for a plurality of pixels. For example, the RGB luminance when only the Green LED is turned on is obtained. Similarly, Red and Blue LEDs are individually turned on, and respective RGB outputs are obtained for a plurality of pixels.

  Here, a correlation diagram as shown in FIGS. 14 to 16 is obtained from the obtained RGB output, and a correction coefficient is obtained from the correlation with other light sources included in each observation light source.

  For example, when only the Blue LED is turned on, as shown in FIG. 14, the correction coefficient for the crosstalk from Blue to Green is 0.23, and the correction coefficient for the crosstalk from Blue to Red is 0. .00. Similarly, when only Red is turned on, as shown in FIG. 15, the correction coefficient for the crosstalk from Red to Blue is 0.00, and the correction coefficient for the crosstalk from Red to Green is 0.04. It becomes. When only Green is turned on, as shown in FIG. 16, the correction coefficient for crosstalk from Green to Blue is 0.08, and the correction coefficient for crosstalk from Green to Red is 0.13. .

  As another method, the correction coefficient can be obtained by applying the above method to an image acquired by simultaneously irradiating all light sources of RGB-LED. However, in this case, a very large number of luminance data is required.

  As a result of imaging the measurement object with the three-wavelength LEDs turned on, luminance distributions before and after the correction process were obtained as shown in FIG. In other words, in the luminance distribution before correction indicated by the broken line, the change in the vicinity of the x-coordinates 210 to 240 corresponding to the step portion of the measurement object is small, but the luminance change after correction changes so much that it can be easily read visually. Results are obtained.

  Similarly, when the phase of the pixel unit is obtained using the luminance distribution data, the following results are obtained. That is, when the pre-correction distribution data shown in FIG. 18 is used, even a flat portion without a step has a wavy shape, making it difficult to distinguish from the step portion. On the other hand, after the correction, as shown in FIG. 19, except for the step portions 210 to 240, it was substantially flat, and a large change was observed only in the step portion.

  Therefore, according to this embodiment, even when a plurality of monochromatic lights in adjacent frequency bands are used, unnecessary luminance (light intensity value) of other monochromatic lights due to crosstalk can be removed.

It is a figure which shows schematic structure of the surface shape measuring apparatus which concerns on a present Example. It is a flowchart which shows the process in a surface shape measuring apparatus. It is a figure which shows the captured image data of a measurement object surface. It is a figure which shows the X-axis direction luminance change of a captured image. It is a figure which shows that the range of (phi) can be specified using the code | symbol information of sin (phi) and cos (phi). It is a figure which shows extraction of real surface height. It is a figure which shows the measurement result at the time of measuring a steep level difference using an Example apparatus. It is a flowchart which shows the process in the surface shape measuring apparatus of a modification. It is a flowchart which shows the estimation process of a spatial frequency. It is a schematic diagram which shows the estimation process of a spatial frequency. It is a figure which shows the estimation experiment result of a spatial frequency. It is a figure which shows the measurement result using the modification method. It is a figure which shows a color filter characteristic. It is a figure which shows the crosstalk which arises at the time of light source light emission of Blue. It is a figure which shows the crosstalk which arises at the time of red light source light emission. It is a figure which shows the crosstalk which arises at the time of light source light emission of Green. It is a figure which shows the non-corrected luminance data and corrected luminance data of crosstalk. It is a figure which shows the uncorrected phase data of crosstalk. It is a figure which shows the correction | amendment phase data of crosstalk.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical system unit 2 ... Control system unit 10 ... Illuminating device 11 ... Collimating lens 13 ... Half mirror 14 ... Objective lens 15 ... Reference surface 17 ... Beam splitter 18 ... Imaging lens 19 ... Imaging device 20 ... CPU
DESCRIPTION OF SYMBOLS 21 ... Memory 22 ... Input part 23 ... Monitor 24 ... Drive part 25 ... Phase calculation part 26 ... Sign determination part 27 ... Image data creation part 30 ... Measurement object 30A ... Measurement object surface 30B ... Convex part of measurement countermeasure surface

Claims (12)

The measurement target surface is irradiated with monochromatic light on the measurement target surface and the reference surface through the branching means, and is reflected from both the measurement target surface and the reference surface and returns from the same optical path. In the surface shape measurement method with multiple wavelengths to obtain the surface height and surface shape of
An image of interference fringes generated by arranging the reference surface in an inclined posture at an arbitrary angle with respect to the light traveling direction and simultaneously irradiating the measurement object and the reference surface with a plurality of monochromatic lights having different wavelengths is obtained. The first process,
A second step of obtaining the intensity value of the interference fringe of each pixel in the acquired image for each monochromatic light;
For each of the pixels using an expression for obtaining an interference fringe waveform, the intensity value of each pixel and the intensity values of a plurality of neighboring pixels are used, and the DC component, the AC amplitude of the interference fringe waveform at those pixels, and Assuming that the phases are equal, a third process for determining the phase of each pixel for each monochromatic light;
A fourth step of obtaining a surface height candidate group from the phase of each pixel obtained for each monochromatic light, and obtaining a common height as an actual height from each wavelength candidate group;
A fifth step of obtaining the surface shape of the measurement object from the obtained actual height;
A surface shape measuring method using a plurality of wavelengths. The surface shape measurement method using a plurality of wavelengths according to claim 1,
The first process to the fifth process are repeated for each measurement position of the measurement object at predetermined time intervals while relatively moving the light directed to the measurement object and one or more measurement objects. A method for measuring the surface shape of a plurality of wavelengths, wherein the surface shape of a measurement object is obtained. In the measuring method of the surface shape by multiple wavelengths according to claim 1 or claim 2,
The obtained phase for each wavelength is obtained by fitting the intensity value g (x, y) of each pixel to an expression of the interference fringe waveform in the vicinity of the pixel g (x, y) = a + bcos {2πf _x x + 2πf _y y + φ}. A method for measuring a surface shape using a plurality of wavelengths. In the measuring method of the surface shape by multiple wavelengths according to any one of claims 1 to 3,
The image of the interference fringes is captured by an imaging unit having a filter that separates a plurality of monochromatic lights,
A method of measuring a surface shape using a plurality of wavelengths, wherein intensity values of interference fringes of other monochromatic light included for each monochromatic light are removed due to the influence of crosstalk caused by the filter characteristics. The measurement target surface is irradiated with monochromatic light on the measurement target surface and the reference surface through the branching means, and is reflected from both the measurement target surface and the reference surface and returns from the same optical path. In the surface shape measuring device with multiple wavelengths to obtain the surface height and surface shape of
The reference surface is arranged in an inclined posture at an arbitrary angle with respect to the traveling direction of light,
Holding means for placing and holding the measurement object;
Illumination means for simultaneously outputting a plurality of monochromatic lights having different wavelengths;
An imaging unit that images the measurement target surface by generating interference fringes for each monochromatic light by reflected light that is irradiated with the plurality of monochromatic lights and reflected from the measurement object and the reference surface and returns on the same optical path;
Sampling means for capturing the measured measurement target surface as an interference fringe intensity value for each pixel;
Storage means for storing an interference fringe intensity value group that is the intensity value captured by the sampling means;
The intensity value is read out for each pixel from the intensity value group stored in the storage means, and the intensity value of each pixel and the intensity value of a neighboring pixel are used for each pixel, and the DC of the interference fringe waveform included in each pixel Assuming that the components, AC amplitude, and phase are equal, using the expression for obtaining the interference fringe waveform, obtain the phase of each pixel for each monochromatic light,
Obtain a plurality of surface height candidate groups from the phase of each pixel obtained for each monochromatic light, obtain the common height from each candidate group as the actual height,
Further, a calculation means for obtaining a surface shape from the obtained surface height of the measurement target surface,
A surface shape measuring apparatus using a plurality of wavelengths. In the surface shape measuring apparatus with multiple wavelengths according to claim 5,
At least the illumination unit, the imaging unit, the branching unit, and the reference surface constitute an optical system unit,
Drive means for moving at least one of the holding means and the optical system unit so that the light directed to the measurement object and one or a plurality of measurement objects move relatively in parallel;
Control means for controlling the operation of each means so as to obtain the surface shape of the measurement object while relatively translating the optical system unit and the holding means;
A surface shape measuring apparatus using a plurality of wavelengths. In the surface shape measuring apparatus with multiple wavelengths according to claim 5 or 6,
The illumination means has a plurality of monochromatic light sources that output different wavelengths. In the surface shape measuring apparatus with multiple wavelengths according to claim 7,
The imaging means includes a filter that separates a plurality of monochromatic lights,
The surface shape measuring apparatus using a plurality of wavelengths, wherein the computing unit removes an intensity value of an interference fringe of other monochromatic light included for each monochromatic light due to the influence of crosstalk caused by the filter characteristics. In the surface shape measuring apparatus with multiple wavelengths according to claim 5 or 6,
The illumination means includes a white light source,
An apparatus for measuring a surface shape using a plurality of wavelengths, comprising: optical means for separating monochromatic light having a plurality of predetermined different wavelengths from a white light source and directing the light to the branching means. The measurement target surface is irradiated with monochromatic light on the measurement target surface and the reference surface through the branching means, and is reflected from both the measurement target surface and the reference surface and returns from the same optical path. In the surface shape measuring device with multiple wavelengths to obtain the surface height and surface shape of
The reference surface is arranged in an inclined posture at an arbitrary angle with respect to the traveling direction of light,
Holding means for placing and holding the measurement object;
Illuminating means for outputting light having a plurality of wavelengths;
Separating means for separating the reflected light that is irradiated with the light and reflected from the measurement object and the reference surface and returns on the same optical path into a plurality of monochromatic lights having different wavelengths;
Imaging means for imaging the measurement target surface by generating interference fringes for each of the separated monochromatic lights;
Sampling means for capturing the measured measurement target surface as an interference fringe intensity value for each pixel;
Storage means for storing an interference fringe intensity value group that is the intensity value captured by the sampling means;
The intensity value is read out for each pixel from the intensity value group stored in the storage means, and the intensity value of each pixel and the intensity value of a neighboring pixel are used for each pixel, and the DC of the interference fringe waveform included in each pixel Assuming that the components, AC amplitude, and phase are equal, using the expression for obtaining the interference fringe waveform, obtain the phase of each pixel for each monochromatic light,
From a plurality of surface height candidate groups obtained by conversion from the phase of each pixel obtained for each monochromatic light, obtain a common height as the actual height,
Further, a calculation means for obtaining a surface shape from the obtained surface height of the measurement target surface,
A surface shape measuring apparatus using a plurality of wavelengths. In the surface shape measuring apparatus with multiple wavelengths according to claim 10,
The separation means is a filter that separates a plurality of monochromatic lights,
The surface shape measuring apparatus using a plurality of wavelengths, wherein the computing unit removes an intensity value of an interference fringe of other monochromatic light included for each monochromatic light due to the influence of crosstalk caused by the filter characteristics. In the surface shape measuring apparatus with multiple wavelengths according to any one of claims 5 to 11,
The computing means is obtained by fitting the intensity value g (x, y) of each pixel to g (x, y) = a + bcos {2πf _x x + 2πf _y y + φ} which is an expression of the interference fringe waveform in the vicinity of the pixel. A surface shape measuring apparatus using a plurality of wavelengths.

Images