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JP2014025782A - Shape measuring device - Google Patents

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JP2014025782A
JP2014025782A JP2012165607A JP2012165607A JP2014025782A JP 2014025782 A JP2014025782 A JP 2014025782A JP 2012165607 A JP2012165607 A JP 2012165607A JP 2012165607 A JP2012165607 A JP 2012165607A JP 2014025782 A JP2014025782 A JP 2014025782A
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imaging
luminance
measured
amplitude
projection
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JP6019886B2 (en
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Keiichi Watanabe
恵一 渡辺
Tomohiro Hirose
知弘 廣瀬
Koji Kitayama
綱次 北山
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Toyota Central R&D Labs Inc
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Abstract

PROBLEM TO BE SOLVED: To prevent received luminance amplitude from lowering due to a modulation transfer function of an optical system.SOLUTION: A shape measuring device 10 comprises projection means (a light source 12, input signal adjustment means 14 and lattice fringe creation means 23) for projecting a lattice fringe image having a prescribed space period and prescribed projection luminance amplitude on a measured surface 22. When projecting the lattice fringe image having a first space period and first projection luminance amplitude and also projecting the lattice fringe image having a second space period and second projection luminance amplitude, if the first space period is shorter than the second space period, the first projection luminance amplitude is set so as to be larger than the second projection luminance amplitude.

Description

本発明は、位相シフト法を用いた、形状測定装置に関する。   The present invention relates to a shape measuring apparatus using a phase shift method.

従来から、位相シフト法を利用して、被測定面の三次元形状を測定する、形状測定装置が知られている。位相シフト法では、直線状の格子縞のパターンを被測定面上に投影する。被測定面上には、その形状に応じた変形格子像が生じる。この変形格子像を、投影軸とは異なる方向から撮像する。撮像された変形格子像の変形具合を解析することで、被測定面の三次元形状を演算する。   2. Description of the Related Art Conventionally, a shape measuring apparatus that measures a three-dimensional shape of a surface to be measured using a phase shift method is known. In the phase shift method, a linear lattice pattern is projected onto the surface to be measured. On the surface to be measured, a deformed lattice image corresponding to the shape is generated. The deformed grid image is picked up from a direction different from the projection axis. By analyzing the degree of deformation of the captured deformed lattice image, the three-dimensional shape of the surface to be measured is calculated.

具体的には、被測定面に格子縞像を投影させる際に、その格子縞像の位相を変化させる。さらに、被測定面上の、位相変化する格子縞像を撮像するとともに、撮像手段における、位相変化に対応した輝度の変化を測定する。測定された輝度変化に基づいて、撮像面上の所定位置に入射した反射光の輝度の位相成分φを求める。   Specifically, when the lattice fringe image is projected onto the surface to be measured, the phase of the lattice fringe image is changed. Further, a lattice fringe image changing in phase on the surface to be measured is picked up, and a change in luminance corresponding to the phase change in the image pickup means is measured. Based on the measured luminance change, the phase component φ of the luminance of the reflected light incident on a predetermined position on the imaging surface is obtained.

被測定面における反射光の反射点(測定点)の、所定の基準面からの距離yと、上記位相φとは、対応関係にあることが知られている。したがって、位相φを求めることで、測定点の距離yを求めることができる。   It is known that the distance y from the predetermined reference surface of the reflection point (measurement point) of the reflected light on the surface to be measured and the phase φ are in a correspondence relationship. Therefore, the distance y of the measurement point can be obtained by obtaining the phase φ.

また、撮像する格子縞の空間周期が短い(空間周波数が高い)ほど、距離yの算出の精度が高くなることが知られている。そこで、特許文献1〜4では、測定点の距離yを求める際に、空間周期の長い格子縞によって求めた測定点の距離yを、空間周期の短い格子縞を用いることで補正している。   Further, it is known that the accuracy of the calculation of the distance y increases as the spatial period of the lattice pattern to be imaged is shorter (the spatial frequency is higher). Therefore, in Patent Documents 1 to 4, when obtaining the distance y of the measurement points, the distance y of the measurement points obtained by the lattice fringes having a long spatial period is corrected by using the lattice fringes having a short spatial period.

特開平6−66527号公報JP-A-6-66527 特開2001−159510号公報JP 2001-159510 A 特開2010−203867号公報JP 2010-203867 A 特開2010−151842号公報JP 2010-151842 A

ところで、格子縞を被測定面に投影させてこれを撮像する投受光光学系は、格子縞の空間周期に応じた光の透過特性を示す、周波数透過特性(MTF、Modulation Transfer Function)を有している。周波数透過特性により、格子縞の空間周期が短くなるほど、その透過性は低下する。そうなると、図19に例示するように、空間周期の異なる複数の格子縞を用いる場合、格子縞の空間周期が短くなるほど、撮像面上の受光輝度振幅が小さくなる。撮像面上の受光輝度振幅が小さくなると、受光輝度の変化を捉えにくくなり、位相φの算出が困難となる。そこで、本発明は、光学系の周波数透過特性による受光輝度振幅の低下を抑制することの可能な、形状測定装置を提供することを目的とする。   By the way, a light projecting / receiving optical system that projects a lattice fringe on a surface to be measured and picks up an image thereof has a frequency transmission characteristic (MTF, Modulation Transfer Function) indicating a light transmission characteristic corresponding to the spatial period of the lattice fringe. . Due to the frequency transmission characteristics, the shorter the spatial period of the lattice fringes, the lower the transparency. Then, as illustrated in FIG. 19, when a plurality of lattice fringes having different spatial periods are used, the light reception luminance amplitude on the imaging surface becomes smaller as the spatial period of the lattice fringes becomes shorter. If the light reception luminance amplitude on the imaging surface becomes small, it becomes difficult to detect a change in the light reception luminance, and it becomes difficult to calculate the phase φ. Accordingly, an object of the present invention is to provide a shape measuring apparatus capable of suppressing a decrease in received light amplitude due to frequency transmission characteristics of an optical system.

本発明は、形状測定装置に関する。当該形状測定装置は、第1空間周期及び第1投影輝度振幅を有する第1格子縞画像を、被測定面に投影する、第1投影手段と、第2空間周期及び第2投影輝度振幅を有する第2格子縞画像を、被測定面に投影する、第2投影手段と、被測定面に投影された格子縞画像の位相を変化させることが可能な、位相変位手段と、被測定面に投影された格子縞画像を撮像することが可能な、撮像手段と、前記位相の変化に対応する、前記撮像手段の受光輝度の変化に基づいて、被測定面の形状を算出する、演算部と、を備える。前記第1空間周期は、前記第2空間周期よりも短く、前記第1投影輝度振幅は、前記第2投影輝度振幅より大きい。   The present invention relates to a shape measuring apparatus. The shape measuring apparatus projects a first checkered image having a first spatial period and a first projected luminance amplitude onto a surface to be measured, a first projecting means, a second spatial period and a second projected luminance amplitude. (2) Second projection means for projecting a lattice pattern image onto the surface to be measured; phase displacement means capable of changing the phase of the lattice pattern image projected onto the surface to be measured; and grid pattern projected onto the surface to be measured An imaging unit capable of capturing an image; and an arithmetic unit that calculates a shape of a surface to be measured based on a change in received light luminance of the imaging unit corresponding to the change in phase. The first spatial period is shorter than the second spatial period, and the first projection luminance amplitude is larger than the second projection luminance amplitude.

また、上記発明において、被測定面に投影された前記第1格子縞画像を撮像するときの、前記撮像手段の撮像面上の受光輝度振幅が、被測定面に投影された前記第2格子縞画像を撮像するときの、前記撮像面上の受光輝度振幅と略等しくなるように、前記第1投影輝度振幅及び第2投影輝度振幅を制御することが好適である。   In the above invention, when the first checkered image projected on the surface to be measured is picked up, the light reception luminance amplitude on the image pickup surface of the imaging means is the second checkered image projected on the surface to be measured. It is preferable to control the first projection luminance amplitude and the second projection luminance amplitude so as to be substantially equal to the light reception luminance amplitude on the imaging surface when imaging.

また、上記発明において、被測定面に投影された前記第1格子縞画像を撮像するときの、前記撮像手段の撮像面上の受光輝度振幅と、被測定面に投影された前記第2格子縞画像を撮像するときの、前記撮像面上の受光輝度振幅が、輝度飽和レベル未満となるように、前記第1投影輝度振幅と前記第2投影輝度振幅を制御することが好適である。   In the above invention, when the first checkered image projected on the surface to be measured is picked up, the received light intensity on the image pickup surface of the imaging means and the second checkered image projected on the surface to be measured are It is preferable to control the first projection luminance amplitude and the second projection luminance amplitude so that the received light luminance amplitude on the imaging surface when imaging is less than the luminance saturation level.

また、上記発明において、前記第1投影輝度振幅と前記第2投影輝度振幅の比を保ったまま、前記第1投影輝度振幅と前記第2投影輝度振幅を制御することが好適である。   In the above invention, it is preferable to control the first projection luminance amplitude and the second projection luminance amplitude while maintaining a ratio between the first projection luminance amplitude and the second projection luminance amplitude.

また、上記発明において、前記演算部は、前記撮像手段の撮像面のうち、受光輝度が所定範囲内に収まる領域に基づいて、被測定面の形状を算出し、前記第1投影輝度振幅及び第2投影輝度振幅を変更させることで、前記受光輝度が前記所定範囲内に収まる領域を変更させることが好適である。   In the above invention, the calculation unit calculates the shape of the surface to be measured based on a region of the imaging surface of the imaging unit in which the received light luminance falls within a predetermined range, and calculates the first projection luminance amplitude and the first 2 It is preferable to change the region where the received light luminance falls within the predetermined range by changing the projection luminance amplitude.

また、本発明に係る形状測定装置は、第1空間周期を有する第1格子縞画像を、被測定面に投影する、第1投影手段と、第2空間周期を有する第2格子縞画像を、被測定面に投影する、第2投影手段と、被測定面に投影された格子縞画像の位相を変化させることが可能な、位相変位手段と、被測定面に投影された格子縞画像を撮像することが可能な、撮像手段と、被測定面に投影された前記第1格子縞画像を前記撮像手段に撮像させる際に、露光時間を第1露光時間に制御する、第1露光調整手段と、被測定面に投影された前記第2格子縞画像を前記撮像手段に撮像させる際に、露光時間を第2露光時間に制御する、第1露光調整手段と、前記位相の変化に対応する、前記撮像手段の受光輝度の変化に基づいて、被測定面の形状を算出する、演算部と、を備える。前記第1空間周期は、前記第2空間周期よりも短く、前記第1露光時間は、前記第2露光時間よりも長い。   In addition, the shape measuring apparatus according to the present invention projects a first checkered image having a first spatial period onto a surface to be measured, first projecting means, and a second checkered image having a second spatial period to be measured. The second projection means that projects onto the surface, the phase displacement means that can change the phase of the lattice pattern image projected onto the surface to be measured, and the image of the lattice pattern projected onto the surface to be measured can be captured The imaging means, the first exposure adjustment means for controlling the exposure time to the first exposure time when the imaging means images the first lattice fringe image projected on the measurement surface, and the measurement surface. A first exposure adjusting unit that controls an exposure time to a second exposure time when the imaged unit captures the projected second checkered image; and a light receiving luminance of the imaging unit corresponding to the phase change Calculate the shape of the surface to be measured based on the change in It includes a calculation unit. The first spatial period is shorter than the second spatial period, and the first exposure time is longer than the second exposure time.

また、上記発明において、被測定面に投影された前記第1格子縞画像を撮像するときの、前記撮像手段の撮像面上の第1受光輝度振幅が、被測定面に投影された前記第2格子縞画像を撮像するときの、前記撮像面上の第2受光輝度振幅と略等しくなるように、前記第1露光時間及び第2露光時間を制御することが好適である。   In the above invention, when the first checkered image projected on the surface to be measured is picked up, the first light-receiving luminance amplitude on the image pickup surface of the imaging means is the second checkered pattern projected on the surface to be measured. It is preferable to control the first exposure time and the second exposure time so as to be approximately equal to the second light receiving luminance amplitude on the imaging surface when an image is captured.

また、上記発明において、被測定面に投影された前記第1格子縞画像を撮像するときの、前記撮像手段の撮像面上の第1受光輝度振幅と、被測定面に投影された前記第2格子縞画像を撮像するときの、前記撮像面上の第2受光輝度振幅が、輝度飽和レベル未満となるように、前記第1露光時間及び第2露光時間を制御することが好適である。   In the above invention, when the first checkered image projected on the surface to be measured is picked up, the first light reception luminance amplitude on the image pickup surface of the imaging means and the second checkered pattern projected on the surface to be measured. It is preferable to control the first exposure time and the second exposure time so that the second light reception luminance amplitude on the imaging surface when an image is captured is less than the luminance saturation level.

また、上記発明において、前記演算部は、前記撮像手段の撮像面のうち、受光輝度が所定範囲内に収まる領域に基づいて、被測定面の形状を算出し、前記第1露光時間及び第2露光時間を変更させることで、前記受光輝度が前記所定範囲内に収まる領域を変更させることが好適である。   Further, in the above invention, the calculation unit calculates a shape of the measurement target surface based on a region of the imaging surface of the imaging unit where the received light luminance falls within a predetermined range, and the first exposure time and the second exposure time are calculated. It is preferable to change an area in which the received light luminance falls within the predetermined range by changing an exposure time.

また、本発明に係る形状測定装置は、第1空間周期を有する第1格子縞画像を、被測定面に投影する、第1投影手段と、第2空間周期を有する第2格子縞画像を、被測定面に投影する、第2投影手段と、被測定面に投影された格子縞画像の位相を変化させることが可能な、位相変位手段と、被測定面に投影された格子縞画像を撮像することが可能な、撮像手段と、被測定面に投影された前記第1格子縞画像を前記撮像手段に撮像させる際に、前記撮像手段の撮像面上の受光輝度振幅を第1増幅率で増幅させる第1増幅手段と、被測定面に投影された前記第2格子縞画像を前記撮像手段に撮像させる際に、前記撮像手段の撮像面上の受光輝度振幅を第2増幅率で増幅させる第2増幅手段と、前記位相の変化に対応する、前記撮像手段の増幅後の受光輝度の変化に基づいて、被測定面の形状を算出する、演算部と、を備える。前記第1空間周期は、前記第2空間周期よりも短く、前記第1増幅率は、前記第2増幅率よりも大きい。   In addition, the shape measuring apparatus according to the present invention projects a first checkered image having a first spatial period onto a surface to be measured, first projecting means, and a second checkered image having a second spatial period to be measured. The second projection means that projects onto the surface, the phase displacement means that can change the phase of the lattice pattern image projected onto the surface to be measured, and the image of the lattice pattern projected onto the surface to be measured can be captured The first amplification for amplifying the received light amplitude on the imaging surface of the imaging means by a first amplification factor when the imaging means and the first lattice fringe image projected on the measurement surface are imaged by the imaging means. And a second amplifying unit that amplifies the light reception luminance amplitude on the imaging surface of the imaging unit by a second amplification factor when the imaging unit images the second lattice pattern image projected on the surface to be measured; Corresponding to the phase change, after amplification of the imaging means Based on the change in light intensity, and calculates the shape of the surface to be measured, it comprises a calculation unit, a. The first spatial period is shorter than the second spatial period, and the first amplification factor is greater than the second amplification factor.

また、本発明に係る形状測定装置は、第1空間周期を有する第1格子縞画像を、被測定面に投影する、第1投影手段と、第2空間周期を有する第2格子縞画像を、被測定面に投影する、第2投影手段と、被測定面に投影された格子縞画像の位相を変化させることが可能な、位相変位手段と、被測定面に投影された格子縞画像を撮像することが可能な、撮像手段と、前記位相の変化に対応する、前記撮像手段の受光輝度の変化に基づいて、被測定面の形状を算出する、演算部と、を備える。前記第1空間周期は、前記第2空間周期よりも短く、被測定面に投影された前記第1格子縞画像を撮像するときの、前記撮像手段の撮像面上の受光輝度振幅は、被測定面に投影された前記第2格子縞画像を撮像するときの、前記撮像面上の受光輝度振幅と略等しい。   In addition, the shape measuring apparatus according to the present invention projects a first checkered image having a first spatial period onto a surface to be measured, first projecting means, and a second checkered image having a second spatial period to be measured. The second projection means that projects onto the surface, the phase displacement means that can change the phase of the lattice pattern image projected onto the surface to be measured, and the image of the lattice pattern projected onto the surface to be measured can be captured An imaging unit, and a calculation unit that calculates a shape of the surface to be measured based on a change in received light luminance of the imaging unit corresponding to the change in phase. The first spatial period is shorter than the second spatial period, and when the first checkered image projected on the surface to be measured is captured, the light reception luminance amplitude on the imaging surface of the imaging unit is the surface to be measured Is substantially equal to the light reception luminance amplitude on the imaging surface when the second grid pattern image projected onto the image is captured.

本発明によれば、光学系の周波数透過特性による、受光輝度振幅の低下を抑制することが可能となる。   According to the present invention, it is possible to suppress a decrease in received light luminance amplitude due to frequency transmission characteristics of an optical system.

本発明の実施の形態における形状測定装置の構成を示すブロック図である。It is a block diagram which shows the structure of the shape measuring apparatus in embodiment of this invention. 位相シフト法を用いた形状測定の原理を説明する斜視図である。It is a perspective view explaining the principle of the shape measurement using a phase shift method. 位相シフト法を用いた形状測定の原理を説明する図である。It is a figure explaining the principle of the shape measurement using a phase shift method. 絶対位相の求め方を説明する図である。It is a figure explaining how to obtain | require an absolute phase. 絶対位相の求め方を説明する図である。It is a figure explaining how to obtain | require an absolute phase. 投影輝度成分のキャリブレーションについて説明する図である。It is a figure explaining the calibration of a projection luminance component. 投影輝度成分のキャリブレーションについて説明する図である。It is a figure explaining the calibration of a projection luminance component. 関数y(i,j)=f(φ(i,j))を求めるためのキャリブレーションについて説明する図である。It is a figure explaining the calibration for calculating | requiring a function y (i, j) = f ((phi) (i, j)). 関数x(i,j)=f(y(i,j))及び関数z(i,j)=f(y(i,j))を求めるためのキャリブレーションについて説明する図である。It is a figure explaining the calibration for calculating | requiring the function x (i, j) = f (y (i, j)) and the function z (i, j) = f (y (i, j)). 本発明の実施の形態における形状測定装置の別例の構成を示すブロック図である。It is a block diagram which shows the structure of another example of the shape measuring apparatus in embodiment of this invention. 本発明の実施の形態における形状測定装置の別例の構成を示すブロック図である。It is a block diagram which shows the structure of another example of the shape measuring apparatus in embodiment of this invention. 本発明の実施の形態における形状測定装置による計測例を説明する図である。It is a figure explaining the example of a measurement by the shape measuring apparatus in embodiment of this invention. 本発明の実施の形態における形状測定装置による計測例を説明する図である。It is a figure explaining the example of a measurement by the shape measuring apparatus in embodiment of this invention. 本発明の実施の形態における形状測定装置の別例による計測例を説明する図である。It is a figure explaining the example of a measurement by another example of the shape measuring device in an embodiment of the invention. 本発明の実施の形態における形状測定装置の別例による計測例を説明する図である。It is a figure explaining the example of a measurement by another example of the shape measuring device in an embodiment of the invention. 本発明の実施の形態における形状測定装置の別例による計測例を説明する図である。It is a figure explaining the example of a measurement by another example of the shape measuring device in an embodiment of the invention. 本発明の実施の形態における形状測定装置の別例による計測例を説明する図である。It is a figure explaining the example of a measurement by another example of the shape measuring device in an embodiment of the invention. 本発明の実施の形態における形状測定装置の別例による計測例を説明する図である。It is a figure explaining the example of a measurement by another example of the shape measuring device in an embodiment of the invention. 投受光光学系の周波数透過特性を説明する図である。It is a figure explaining the frequency transmission characteristic of a light projection / reception optical system.

図1に、本実施の形態に係る形状測定装置10を例示する。形状測定装置10は、光源12、入力信号調整手段14、位相変位手段16、撮像手段26、及び演算部20を含んで構成される。なお、以下の説明では、測定対象物50の、奥行き方向(距離方向)をy軸、幅方向をx軸、高さ方向をz軸とする。また、光源12側の格子縞における平面座標を、u軸、v軸で表す。また、撮像手段26の撮像面18の座標を、i軸、j軸で表す。   FIG. 1 illustrates a shape measuring apparatus 10 according to the present embodiment. The shape measuring apparatus 10 includes a light source 12, an input signal adjustment unit 14, a phase displacement unit 16, an imaging unit 26, and a calculation unit 20. In the following description, the depth direction (distance direction) of the measurement object 50 is the y axis, the width direction is the x axis, and the height direction is the z axis. Further, the plane coordinates in the lattice pattern on the light source 12 side are represented by the u axis and the v axis. Also, the coordinates of the imaging surface 18 of the imaging means 26 are represented by the i axis and the j axis.

光源12は、測定対象物50の被測定面22に格子縞像を投影する。光源12によって投影される格子縞は、それぞれの格子縞の有する空間的な周期(空間周期)が異なるものであってよく、光源12は、これら空間周期の異なる複数の格子縞を交互に被測定面22に投影するものであってよい。ここで、光源12は、液晶素子やDMD(Digital Mirror Device)を用いて格子縞の画像を投影するプロジェクタであってよい。また、光源12は、ハロゲンランプ等の照明部材であってよく、当該照明部材と被測定面22との間の光路上に、ガラス板等に格子パターンを描いた実格子を配置してもよい。   The light source 12 projects a lattice fringe image on the measurement target surface 22 of the measurement object 50. The lattice fringes projected by the light source 12 may have different spatial periods (spatial periods) of the respective lattice fringes, and the light source 12 alternately places a plurality of lattice fringes having different spatial periods on the measurement surface 22. It may be a projection. Here, the light source 12 may be a projector that projects an image of a checkered pattern using a liquid crystal element or a DMD (Digital Mirror Device). Further, the light source 12 may be an illumination member such as a halogen lamp, and an actual lattice having a lattice pattern drawn on a glass plate or the like may be disposed on the optical path between the illumination member and the surface to be measured 22. .

光源12としてプロジェクタを用いる場合、格子縞の画像を作成する格子縞作成手段23を備えてよい。格子縞作成手段23は、プロジェクタに入力信号を送信する、コンピュータ等の演算装置24に組み込まれていてよい。   When a projector is used as the light source 12, a checker pattern creating unit 23 that creates a checkered image may be provided. The checkerboard creating means 23 may be incorporated in an arithmetic device 24 such as a computer that transmits an input signal to the projector.

また、格子縞の画像であっても、実格子であっても、被測定面22に投影される格子縞は、いずれの空間周期であっても、正弦状の強度分布をもつパターンが被測定面22に投影されるような格子パターンであることが好適である。例えば、cos波状の透過率分布を備えた格子縞であってよい。   Further, regardless of whether the image is a lattice fringe image or a real lattice, the lattice fringe projected on the measured surface 22 has a pattern having a sinusoidal intensity distribution regardless of the spatial period. It is preferable that the lattice pattern is projected onto the screen. For example, it may be a lattice pattern having a cos wave-like transmittance distribution.

入力信号調整手段14は、光源12への入力信号を調整する調整手段である。入力信号調整手段14は、演算装置24に組み込まれていてよい。入力信号調整手段14は、相対的に空間周期の短い格子縞を被測定面22に投影するときの、光源12への入力信号の輝度成分が、相対的に空間周期の長い格子縞を被測定面22に投影するときの輝度成分よりも大きくなるように、前記入力信号を調整する。光源12がプロジェクタである場合には、プロジェクタに送信される格子縞画像の空間周期に応じた輝度成分を含んだ入力信号を、格子縞画像データの送信と併せて光源12に送信してもよい。ここで、入力信号の輝度成分とは、光源12の投影輝度振幅であってよい。投影輝度振幅の調整は、光源12の輝度を増減させることで行ってもよく、また、光源12の単位時間当たりの照射時間を増減させることで行ってもよい。また、実格子を用いる場合には、入力信号調整手段14は、実格子の交換時に、交換された実格子の空間周期に応じた輝度成分となる様に、光源12への入力信号を調整するようにしてもよい。   The input signal adjusting unit 14 is an adjusting unit that adjusts an input signal to the light source 12. The input signal adjustment unit 14 may be incorporated in the arithmetic device 24. When the input signal adjusting means 14 projects a lattice fringe having a relatively short spatial period onto the surface to be measured 22, the luminance component of the input signal to the light source 12 has a relatively long spatial period. The input signal is adjusted so as to be larger than the luminance component at the time of projection. When the light source 12 is a projector, an input signal including a luminance component corresponding to the spatial period of the checkered image transmitted to the projector may be transmitted to the light source 12 together with the transmission of the checkered image data. Here, the luminance component of the input signal may be a projection luminance amplitude of the light source 12. The adjustment of the projection luminance amplitude may be performed by increasing or decreasing the luminance of the light source 12, or may be performed by increasing or decreasing the irradiation time per unit time of the light source 12. In the case of using a real grid, the input signal adjusting unit 14 adjusts the input signal to the light source 12 so that the luminance component according to the spatial period of the replaced real grid is obtained when the real grid is replaced. You may do it.

光源12、入力信号調整手段14と、格子縞作成手段23または実格子を、まとめて、投影手段として捉えてもよい。この投影手段は、異なる空間周波数及び投影輝度振幅をそれぞれ有する、複数の格子縞画像を、選択的に被測定面22に投影するものであってよい。また、格子縞画像別に、独立して投影手段を設けてもよい。また、後述するように、投影手段が、所定の空間周期を有する第1の格子縞像と、第1の格子縞像よりも空間周期の長い第2の格子縞像とを、選択的に被測定面22に投影する場合は、第1の格子縞を被測定面22に投影するときの輝度成分は、第2の格子縞を被測定面22に投影するときの輝度成分より大きいものとすることができる。   The light source 12, the input signal adjustment unit 14, the lattice fringe creation unit 23, or the actual lattice may be collectively regarded as a projection unit. This projection means may selectively project a plurality of checkered images having different spatial frequencies and projection luminance amplitudes onto the surface to be measured 22. In addition, a projection unit may be provided independently for each checkered image. Further, as will be described later, the projection unit selectively selects the first checkered image having a predetermined spatial period and the second checkered image having a spatial period longer than that of the first checkered pattern 22 to be measured 22. , The luminance component when the first lattice fringe is projected onto the surface to be measured 22 can be greater than the luminance component when the second lattice fringe is projected onto the surface to be measured 22.

位相変位手段16は、被測定面22に投影された格子縞像の位相を変化させる。格子縞像をプロジェクタにより投影する場合、位相変位手段16は、演算装置24に組み込まれていてよく、位相を変化させた格子縞像をプロジェクタに送信するようにしてよい。また、格子縞が実格子である場合、位相変位手段16は、実格子を移動させるステージ手段であってよい。   The phase displacement unit 16 changes the phase of the lattice fringe image projected on the measurement surface 22. In the case of projecting a lattice fringe image with a projector, the phase displacement unit 16 may be incorporated in the arithmetic unit 24, and the lattice fringe image with the phase changed may be transmitted to the projector. Further, when the lattice fringes are real lattices, the phase displacement means 16 may be stage means for moving the real lattice.

撮像手段26は、被測定面22に投影された格子縞像を撮像する。撮像手段26は、CCDカメラまたはCMOSカメラであってよい。また、撮像手段26は、撮像面18を備えていてよい。撮像面18には、撮像素子が行方向及び列方向に(2次元的に)複数配列されていてよい。   The imaging unit 26 captures a lattice fringe image projected on the measurement surface 22. The imaging means 26 may be a CCD camera or a CMOS camera. Further, the imaging means 26 may include an imaging surface 18. On the imaging surface 18, a plurality of imaging elements may be arranged (two-dimensionally) in the row direction and the column direction.

演算部20は、撮像手段26が受光した受光輝度に基づいて、被測定面22の形状を算出する。具体的には、演算部20は、空間周期の異なる格子縞の、それぞれの位相の変化に対応する、撮像手段26の受光輝度のそれぞれの変化に基づいて、被測定面22の形状を算出する。演算部20は、演算装置24に組み込まれていてよい。また、演算部20は、相対位相算出手段28、絶対位相算出手段30、位相−y座標算出手段32、及びy座標−xz座標算出手段34をサブシステムとして備えていてよい。これらの作用については後述する。   The computing unit 20 calculates the shape of the surface to be measured 22 based on the light reception luminance received by the imaging unit 26. Specifically, the calculation unit 20 calculates the shape of the measurement target surface 22 based on each change in received light luminance of the imaging unit 26 corresponding to each change in phase of lattice fringes having different spatial periods. The calculation unit 20 may be incorporated in the calculation device 24. The computing unit 20 may include a relative phase calculation unit 28, an absolute phase calculation unit 30, a phase-y coordinate calculation unit 32, and a y coordinate-xz coordinate calculation unit 34 as subsystems. These actions will be described later.

次に、位相シフト法を用いた形状測定の原理について説明する。図2に示すように、光源12は、被測定面22に向かって、格子縞36の像を投影する。このとき、光源12側の格子縞36について、格子縞36上の任意の座標(u,v)の透過率Pk(u,v)は下記数式1のように表すことができる。 Next, the principle of shape measurement using the phase shift method will be described. As shown in FIG. 2, the light source 12 projects an image of the checkered pattern 36 toward the measurement surface 22. At this time, the transmittance P k (u, v) at an arbitrary coordinate (u, v) on the lattice fringe 36 with respect to the lattice fringe 36 on the light source 12 side can be expressed as Equation 1 below.

ここで、Aはオフセット、Bは格子縞36の投影振幅である。また、λは格子縞36の空間周期である。また、kは任意の実数であり、格子縞36の変位を表す値である。例えば、初期位相(k=0)から格子縞36の位相をπ/2ずらす時には、k=1である。   Here, A is the offset, and B is the projection amplitude of the lattice fringes 36. Also, λ is the spatial period of the lattice fringes 36. Further, k is an arbitrary real number and is a value representing the displacement of the checkered pattern 36. For example, when the phase of the grating pattern 36 is shifted by π / 2 from the initial phase (k = 0), k = 1.

数式1により、撮像面18上の任意の座標(i,j)の撮像素子が受光する、被測定面22からの反射光の輝度Ik(i,j)は、下記(数式2)のように表すことができる。 The luminance I k (i, j) of the reflected light from the surface to be measured 22 received by the imaging device at an arbitrary coordinate (i, j) on the imaging surface 18 according to Equation 1 is as shown in the following (Equation 2). Can be expressed as

ここで、A(i,j)、B(i,j)は、外乱光や被測定物の反射率で決まる値である
。φ(i,j)は、座標(i,j)における反射光の位相を表している。
Here, A (i, j) and B (i, j) are values determined by ambient light and the reflectance of the object to be measured. φ (i, j) represents the phase of the reflected light at the coordinates (i, j).

数式1におけるkを1、2及び3とすると、図3に示すように、格子縞36の位相は、初期位相(k=0)から、順次、π/2、π、及び3/2πずつずれる。このとき、初期位相を含めた、座標(i,j)の撮像素子の輝度I0(i,j)、I1(i,j)、I2(i,j)、I3(i,j)を用いると、数式2から、下記数式3を導くことができる。 Assuming that k in Equation 1 is 1, 2, and 3, as shown in FIG. 3, the phase of the lattice fringes 36 is sequentially shifted by π / 2, π, and 3 / 2π from the initial phase (k = 0). At this time, the luminances I 0 (i, j), I 1 (i, j), I 2 (i, j), I 3 (i, j) of the image sensor at the coordinates (i, j) including the initial phase are included. ) Can be derived from Equation 2 below.

数式3から位相φ(i,j)を求めることができる。ここで、座標(i,j)の撮像素子が受光した反射光の、被測定面22における反射点(測定点)と、任意の基準面との距離yと、数式3で求めた位相φ(i,j)とは、一対一に対応することが知られている。つまり、y(i,j)=f(φ(i,j))である。したがって、予め基準面yと位相φとの関係を、標準試料等によって求めておいて、関数y(i,j)=f(φ(i,j))を取得するとともに、この関数と、数式3で求めた位相φ(i,j)に応じて、測定点の距離y(i,j)を求めることができる。   From Equation 3, the phase φ (i, j) can be obtained. Here, the distance y between the reflection point (measurement point) on the measured surface 22 of the reflected light received by the imaging device at coordinates (i, j) and an arbitrary reference surface, and the phase φ ( i, j) are known to correspond one-to-one. That is, y (i, j) = f (φ (i, j)). Therefore, the relationship between the reference plane y and the phase φ is obtained in advance using a standard sample or the like, and the function y (i, j) = f (φ (i, j)) is obtained. According to the phase φ (i, j) obtained in step 3, the distance y (i, j) of the measurement point can be obtained.

なお、図4に示すように、座標(i,j)の撮像素子からの視線上の位相φ(i,j)は、距離yが大きく変化すると、2πを超えて繰り返し変化する。例えば、y方向の測定領域内で、位相が2nπ変化する場合、y座標の候補はn個存在することになる。図4では、y方向の測定領域内で、位相φを持つy座標の候補が5つ生じた様子が例示されている。   As shown in FIG. 4, the phase φ (i, j) on the line of sight from the image sensor at the coordinates (i, j) repeatedly changes beyond 2π when the distance y changes greatly. For example, if the phase changes by 2nπ in the measurement region in the y direction, there are n y coordinate candidates. FIG. 4 illustrates a state where five y-coordinate candidates having the phase φ are generated in the measurement region in the y direction.

y座標の候補を絞り込むために、空間周期の異なる格子縞36を用いてよい。まず、図5に示すように、相対的に空間周期の長い(空間周波数の低い)、格子縞36A(粗い格子縞)を用いて位相φa’(i,j)を求める。ここで、y方向の測定領域内で、一つの位相のみが算出されるように、言い換えると、y方向の測定領域内で、位相の取り得る範囲が0から2πとなるような空間周期の、格子縞36Aを用いることが好適である。このとき、y方向の測定領域内で、一つの位相φa’(i,j)に対応する、一つのy座標ya’(i,j)を得ることができる。 In order to narrow down y-coordinate candidates, lattice fringes 36 having different spatial periods may be used. First, as shown in FIG. 5, the phase φ a ′ (i, j) is obtained using a lattice fringe 36A (coarse lattice fringe) having a relatively long spatial period (low spatial frequency). Here, so that only one phase is calculated in the measurement region in the y direction, in other words, in the measurement region in the y direction, the spatial period is such that the possible range of the phase is 0 to 2π. It is preferable to use the lattice stripe 36A. At this time, in the y direction of the measurement region, one phase φ a '(i, j) corresponds to one of the y-coordinate y a' (i, j) can be obtained.

次に、粗い格子縞36Aより空間周期の短い細格子縞36Bを用いて、位相φb’(i,j)を求める。このとき、y方向の測定領域内で、位相φb’(i,j)に対応する、複数のy座標候補値ybk’(i,j)を得ることができる。さらに、複数の候補値ybk’(i,j)のうち、粗い格子縞36Aを用いて算出したy座標ya’(i,j)に最も近いy座標yb’(i,j)を抽出する。例えば、ya’(i,j)との差εbが最も小さいものを算出することで、y座標yb’(i,j)を抽出してよい。 Next, the phase φ b ′ (i, j) is obtained using the fine lattice fringes 36B having a shorter spatial period than the coarse lattice fringes 36A. At this time, a plurality of y coordinate candidate values y bk ′ (i, j) corresponding to the phase φ b ′ (i, j) can be obtained within the measurement region in the y direction. Further, the y-coordinate y b ′ (i, j) closest to the y-coordinate y a ′ (i, j) calculated using the coarse grid pattern 36A is extracted from the plurality of candidate values y bk ′ (i, j). To do. For example, the y coordinate y b ′ (i, j) may be extracted by calculating the one having the smallest difference ε b from y a ′ (i, j).

次に、格子縞36Bより空間周期の短い微細格子縞36Cを用いて、位相φc’(i,j)を求める。このとき、y方向の測定領域内で、位相φc’(i,j)に対応する、複数のy座標候補値yck’(i,j)を得ることができる。さらに、複数の候補値yck’(i,j)のうち、細格子縞36Bを用いて算出したy座標yb’(i,j)に最も近いy座標yc’(i,j)を抽出する。抽出されたyc’(i,j)を、測定点のy座標とする(yc’(i,j)=y(i,j))。例えば、yb’(i,j)との差εcが最も小さいものを算出することで、y座標yc’(i,j)を抽出してよい。 Next, the phase φ c ′ (i, j) is obtained using the fine lattice fringe 36C having a shorter spatial period than the lattice fringe 36B. At this time, a plurality of y coordinate candidate values y ck ′ (i, j) corresponding to the phase φ c ′ (i, j) can be obtained within the measurement region in the y direction. Further, the y coordinate y c ′ (i, j) closest to the y coordinate y b ′ (i, j) calculated using the fine grid stripe 36B is extracted from the plurality of candidate values y ck ′ (i, j). To do. The extracted y c ′ (i, j) is set as the y coordinate of the measurement point (y c ′ (i, j) = y (i, j)). For example, 'by calculating what (i, j) the difference epsilon c is the smallest and, y-coordinate y c' y b (i, j) may be extracted.

さらに、求めたy座標y(i,j)から、x座標x(i,j)及びz座標z(i,j)を求めてもよい。撮像手段26の開口角が絞り込まれている等の理由により、撮像素子に入射する反射光の入射角は、予め決められている。したがって、撮像素子に入射する反射光の光路上のy座標を特定すれば、当該y座標に対応するx座標及びz座標も求めることができる。例えば、予め、y座標とこれに対応するx座標及びz座標を、標準試料等によって求めておいてよい。また、y座標とx座標及びz座標との関係を表す関数x(i,j)=f(y(i,j))及びz(i,j)=f(y(i,j))を求めてもよい。これらの関数と、上記にて抽出したy座標y(i,j)から、測定点のx座標x(i,j)及びz座標z(i,j)を抽出することができる。   Further, the x coordinate x (i, j) and the z coordinate z (i, j) may be obtained from the obtained y coordinate y (i, j). For reasons such as the aperture angle of the image pickup means 26 being narrowed, the incident angle of the reflected light incident on the image pickup device is predetermined. Therefore, if the y coordinate on the optical path of the reflected light incident on the image sensor is specified, the x coordinate and the z coordinate corresponding to the y coordinate can also be obtained. For example, the y coordinate and the corresponding x coordinate and z coordinate may be obtained in advance using a standard sample or the like. Further, the functions x (i, j) = f (y (i, j)) and z (i, j) = f (y (i, j)) representing the relationship between the y coordinate, the x coordinate, and the z coordinate are expressed. You may ask for it. From these functions and the y-coordinate y (i, j) extracted above, the x-coordinate x (i, j) and z-coordinate z (i, j) of the measurement point can be extracted.

次に、上記の原理に基づいた、形状測定の流れについて説明する。形状測定は、(1)キャリブレーション工程、及び(2)実測工程、の2種類の工程に分けることができる。   Next, the flow of shape measurement based on the above principle will be described. The shape measurement can be divided into two types of processes: (1) calibration process and (2) actual measurement process.

まず、被測定面を測定する前段階の、(1)キャリブレーション工程について説明する。キャリブレーション工程は、(1−1)投影輝度成分のキャリブレーション、(1−2)関数y(i,j)=f(φ(i,j))を求めるためのキャリブレーション、及び(1−3)関数x(i,j)=f(y(i,j))及びz(i,j)=f(y(i,j))を求めるためのキャリブレーション、の3つを含んでよい。   First, the (1) calibration process in the previous stage of measuring the surface to be measured will be described. The calibration process includes (1-1) calibration of the projection luminance component, (1-2) calibration for obtaining the function y (i, j) = f (φ (i, j)), and (1- 3) The function x (i, j) = f (y (i, j)) and the calibration for obtaining z (i, j) = f (y (i, j)) may be included. .

(1−1)投影輝度成分のキャリブレーション
空間周期の異なる格子縞36A〜36Cを用いるに当たり、光源12の輝度成分(投影輝度成分)を調整する。図6に示すように、光源12、撮像手段26、及び演算装置24等からなる投受光光学系が有する、周波数透過特性(MTF)により、格子縞36の空間周期に応じて、撮像手段26の撮像面18上の輝度振幅(受光輝度振幅)が変化する。具体的には、図6上段に例示するように、格子縞36の空間周期が短くなるほど、撮像面18における受光輝度振幅は減少する。撮像面18における受光輝度振幅の減少を抑制するために、被測定面22の測定に先駆けて、光源12の投影輝度成分を、格子縞の空間周期に応じて予め調整する。
(1-1) Calibration of Projected Luminance Component In using the lattice fringes 36A to 36C having different spatial periods, the luminance component (projected luminance component) of the light source 12 is adjusted. As shown in FIG. 6, imaging by the imaging unit 26 is performed according to the spatial period of the lattice fringe 36 by the frequency transmission characteristic (MTF) of the light projecting / receiving optical system including the light source 12, the imaging unit 26, the arithmetic unit 24, and the like. The luminance amplitude (light reception luminance amplitude) on the surface 18 changes. Specifically, as illustrated in the upper part of FIG. 6, the light reception luminance amplitude on the imaging surface 18 decreases as the spatial period of the lattice pattern 36 becomes shorter. In order to suppress a decrease in the light reception luminance amplitude on the imaging surface 18, the projection luminance component of the light source 12 is adjusted in advance according to the spatial period of the lattice fringes prior to the measurement of the measurement surface 22.

まず、光源12から、空間周期の異なる格子縞を、交互に、セラミック板等の標準板に投影する。平板に投影され、位相を変化させた格子縞像を、撮像手段26にて撮像する。撮像面18上の受光輝度振幅と、撮像した格子縞の空間周期との関係を、実測により求める。   First, from the light source 12, lattice fringes having different spatial periods are alternately projected onto a standard plate such as a ceramic plate. A lattice fringe image projected on a flat plate and whose phase is changed is picked up by the image pickup means 26. The relationship between the light reception luminance amplitude on the imaging surface 18 and the spatial period of the imaged lattice fringes is obtained by actual measurement.

粗い格子縞36Aの空間周期をλL、細格子縞36Bの空間周期をλM、微細格子縞36Cの空間周期をλHとすると、実測により求めた関係から、格子縞36の空間周期をλL、λM、及びλHにそれぞれ対応する、受光輝度振幅RL、RM、及びRHがそれぞれ得られる。ここで、図6上段に示すように、受光輝度振幅RL、RM、RHはいずれも相対値であって、いずれも1以下の値とする。 Assuming that the spatial period of the coarse grating fringe 36A is λ L , the spatial period of the fine grating fringe 36B is λ M , and the spatial period of the fine grating fringe 36C is λ H , the spatial period of the grating fringe 36 is λ L , λ M , And λ H , respectively, the received light intensity amplitudes R L , R M , and R H are obtained. Here, as shown in the upper part of FIG. 6, the received light luminance amplitudes R L , R M , and R H are all relative values, and are all set to 1 or less.

空間周期λL、λM、及びλHと、受光輝度振幅RL、RM、及びRHの関係から、入力信号調整手段14は、各格子縞36A〜36Cに対応する光源12の投影輝度成分を調整する。ここで、光源12の投影輝度を調整する際に、光源の輝度を増幅させ過ぎて、撮像素子の輝度飽和レベルを超えないことが好適である。 From the relationship between the spatial periods λ L , λ M , and λ H and the received light luminance amplitudes R L , R M , and R H , the input signal adjusting unit 14 uses the projection luminance component of the light source 12 corresponding to each of the lattice fringes 36A to 36C. Adjust. Here, when adjusting the projection brightness of the light source 12, it is preferable that the brightness of the light source is excessively amplified and does not exceed the brightness saturation level of the image sensor.

さらに、格子縞36A〜36Cのそれぞれの像を撮像した際に、それぞれの受光輝度振幅が、輝度レベルを飽和しない範囲内で最大のものであれば、いずれの格子縞36A〜36Cにおいても、感度の良好な測定を行うことができる。このことから、格子縞36A〜36Cごとの受光輝度振幅が同一となるように、かつ、飽和レベルを越えない範囲での最大値となるように、光源12の投影輝度成分を調整することが好適である。   Furthermore, when each image of the lattice fringes 36A to 36C is picked up, the sensitivity is good in any of the lattice fringes 36A to 36C as long as the light reception luminance amplitude is maximum within a range in which the luminance level is not saturated. Measurements can be made. Therefore, it is preferable to adjust the projection luminance component of the light source 12 so that the light reception luminance amplitude for each of the lattice fringes 36A to 36C is the same and the maximum value within a range not exceeding the saturation level. is there.

まず、受光輝度を輝度飽和レベル以下に抑えるために、撮像面18上の受光輝度振幅が最大となる状態を設定して、光源12の投影輝度を調整する。例えば、標準板を、y方向の測定領域内で最も撮像手段26側に近接して配置するとともに、標準板から鏡面反射した反射光を撮像面18に受光させる。   First, in order to suppress the light reception luminance to a luminance saturation level or less, a state in which the light reception luminance amplitude on the imaging surface 18 is maximized is set, and the projection luminance of the light source 12 is adjusted. For example, the standard plate is disposed closest to the imaging means 26 side in the measurement region in the y direction, and the reflected light that is specularly reflected from the standard plate is received by the imaging surface 18.

入力信号調整手段14は、まず、空間周期λL、λM、及びλHと、受光輝度振幅RL、RM、及びRHの関係から、格子縞像を投影する際の振幅設定値(投影輝度振幅)STを定める。具体的には、図6下段に示すように、空間周期λLの投影輝度振幅STLをRH、空間周期λMの投影輝度振幅STMをRH/RM、空間周期λHの投影輝度振幅STHを1とする。このとき、各周期の格子縞像を被測定面に投影したときの、撮像面18上の受光輝度振幅を、図7上段に例示する。いずれの空間周期についても、受光輝度振幅が等しくRHになっている。 First, the input signal adjusting unit 14 determines the amplitude setting value (projection) when projecting the lattice fringe image from the relationship between the spatial periods λ L , λ M , and λ H and the received light luminance amplitudes R L , R M , and R H. Luminance amplitude) ST is determined. Specifically, as shown in the lower part of FIG. 6, projecting the projection luminance amplitude ST L of spatial period lambda L R H, the projection luminance amplitude ST M of spatial period lambda M of R H / R M, spatial period lambda H and 1 luminance amplitude ST H. At this time, the light reception luminance amplitude on the imaging surface 18 when the lattice fringe image of each period is projected on the surface to be measured is illustrated in the upper part of FIG. In any spatial period, the received light amplitude is equal to RH .

さらに入力信号調整手段14は、受光輝度が、飽和レベルを超えない範囲での最大値となるように、投影輝度振幅を増幅させる。具体的には、図7下段に示すように、それぞれの投影輝度振幅STL、STM、STHに、係数A(>1)を掛ける。係数Aの設定に当たっては、撮像素子の輝度レベルが飽和しない様に、実測等で調整することが好適である。係数Aを掛けた投影輝度振幅STL’=A・STL、STM’=A・STM、及びSTH’=A・STHは、それぞれ演算装置24の図示しない記憶部に記憶される。 Further, the input signal adjusting unit 14 amplifies the projection luminance amplitude so that the received light luminance becomes a maximum value within a range not exceeding the saturation level. Specifically, as shown in the lower part of FIG. 7, the projection luminance amplitudes ST L , ST M , and ST H are multiplied by a coefficient A (> 1). In setting the coefficient A, it is preferable to adjust by actual measurement or the like so that the luminance level of the image sensor is not saturated. The projection luminance amplitudes ST L ′ = A · ST L , ST M ′ = A · ST M , and ST H ′ = A · ST H multiplied by the coefficient A are respectively stored in a storage unit (not shown) of the arithmetic unit 24. .

(1−2)関数y(i,j)=f(φ(i,j))を求めるためのキャリブレーション
次に、y座標y(i,j)と、φ(i,j)の関係を求める。図8に示すように、セラミック平板等の標準板40を、yステージ42に配置する。yステージ42は、標準板40を、y軸上に移動させることが可能となっている。yステージ42により、標準板40を、y方向の測定領域の全域、または任意の範囲に亘って移動させる。y座標が変更するごとに、光源12から標準板40に格子縞像を投影する。この投影の際に、格子縞の位相を変化させる。さらに、投影された格子縞像を撮像手段26に撮像させる。格子縞像の位相の変化に伴う撮像面18上の受光輝度の変化に基づいて、位相φを求める。このときの標準板のy座標は、yステージ42の位置設定値等により既知であるので、位相φと座標yを関連づける。この関連付けを、撮像面18の全座標(全撮像素子)または任意の座標に対して行う。さらに、この、位相φと座標yの関連付けを、y方向の測定領域の全域、または任意の範囲に亘って行う。得られた位相φと座標yの対応関係を、関数y(i,j)=f(φ(i,j))に近似して、演算装置24の図示しない記憶部に記憶させてもよい。また、この関数yは、格子縞36A〜36Cごとに算出してもよく、各格子縞に対応した、関数ya(i,j)=fa(φ(i,j))、yb(i,j)=fb(φ(i,j))、及びyc(i,j)=fc(φ(i,j))を算出して記憶部に記憶させてもよい。または、これらの関数における、位相φと座標yの関係を、ルックアップテーブル等の形式で記憶部に記憶させてもよい。
(1-2) Calibration for obtaining function y (i, j) = f (φ (i, j)) Next, the relationship between the y coordinate y (i, j) and φ (i, j) Ask. As shown in FIG. 8, a standard plate 40 such as a ceramic flat plate is disposed on the y stage 42. The y stage 42 can move the standard plate 40 on the y axis. The standard plate 40 is moved by the y stage 42 over the entire measurement area in the y direction or an arbitrary range. Each time the y coordinate changes, a grid pattern is projected from the light source 12 onto the standard plate 40. During this projection, the phase of the lattice pattern is changed. Furthermore, the imaged means 26 is made to image the projected lattice pattern image. The phase φ is obtained based on the change in the light receiving luminance on the imaging surface 18 accompanying the change in the phase of the lattice fringe image. Since the y coordinate of the standard plate at this time is known from the position setting value of the y stage 42, the phase φ and the coordinate y are associated with each other. This association is performed with respect to all coordinates (all imaging elements) on the imaging surface 18 or arbitrary coordinates. Further, the correlation between the phase φ and the coordinate y is performed over the entire measurement area in the y direction or over an arbitrary range. The obtained correspondence relationship between the phase φ and the coordinate y may be approximated to the function y (i, j) = f (φ (i, j)) and stored in a storage unit (not shown) of the arithmetic unit 24. The function y may be calculated for each lattice stripes 36 a - 36 c, corresponding to each lattice stripes, function y a (i, j) = f a (φ (i, j)), y b (i, j) = f b (φ ( i, j)), and y c (i, j) = f c (φ (i, j)) may be calculated and stored in the storage unit. Alternatively, the relationship between the phase φ and the coordinate y in these functions may be stored in the storage unit in the form of a lookup table or the like.

(1−3)関数x(i,j)=f(y(i,j))及びz(i,j)=f(y(i,j))を求めるためのキャリブレーション
図9に示すように、yステージ42にグリッド格子44を配置する。グリッド格子44は、各グリッドのx,z座標が既知の実格子であってよい。グリッド格子44を所定のy座標y0に位置させたときの、グリッド格子44の像を撮像手段26で撮像する。このとき、撮像面18上の座標(i,j)に対応する、グリッド格子44上の測定点のx,z座標は、周辺のグリッドの既知のx,z座標から線形補間等により求めることができる。したがって、撮像面18上の座標(i,j)に対応する、被測定面の測定点のy座標がy0であるときの、x,z座標が求められる。この演算を、撮像面18上の全座標(全撮像素子)または任意の座標に対して行う。さらに、撮像面18上の座標(i,j)及びy座標と、x座標及びz座標との関連付けを、y方向の測定領域の全域、または任意の範囲に亘って行う。得られた座標(i,j)及びy座標と、x座標及びz座標との対応関係を、関数x(i,j)=f(y(i,j))及びz(i,j)=f(y(i,j))に近似して、演算装置24の図示しない記憶部に記憶させてもよい。または、関数x(i,j)=f(y(i,j))及びz(i,j)=f(y(i,j))における、座標(i,j)及びy座標と、x座標及びz座標との対応関係を、ルックアップテーブル等の形式で記憶させてもよい。
(1-3) Calibration for obtaining functions x (i, j) = f (y (i, j)) and z (i, j) = f (y (i, j)) As shown in FIG. In addition, the grid grating 44 is arranged on the y stage 42. The grid lattice 44 may be a real lattice whose x and z coordinates of each grid are known. An image of the grid grating 44 when the grid grating 44 is positioned at a predetermined y coordinate y 0 is picked up by the image pickup means 26. At this time, the x and z coordinates of the measurement points on the grid grating 44 corresponding to the coordinates (i, j) on the imaging surface 18 can be obtained from the known x and z coordinates of the surrounding grid by linear interpolation or the like. it can. Therefore, the x and z coordinates when the y coordinate of the measurement point on the measurement surface corresponding to the coordinate (i, j) on the imaging surface 18 is y 0 are obtained. This calculation is performed on all coordinates (all image sensors) on the imaging surface 18 or arbitrary coordinates. Further, the coordinates (i, j) and y coordinate on the imaging surface 18 are associated with the x coordinate and z coordinate over the entire measurement area in the y direction or over an arbitrary range. The correspondence between the obtained coordinates (i, j) and y coordinates and the x and z coordinates is expressed as follows: functions x (i, j) = f (y (i, j)) and z (i, j) = It may be approximated to f (y (i, j)) and stored in a storage unit (not shown) of the arithmetic unit 24. Alternatively, the coordinates (i, j) and y coordinates in the function x (i, j) = f (y (i, j)) and z (i, j) = f (y (i, j)) and x The correspondence relationship with the coordinate and the z coordinate may be stored in a format such as a lookup table.

(2)実測工程
図1に示すように、測定対象物50を光源12の光路上に配置する(S10)。次に、格子縞作成手段23が、粗い格子縞36Aの画像データを光源12に送信する(S12)。このとき、入力信号調整手段14は、粗い格子縞36Aに対応した投影輝度振幅A・STLに適合した輝度成分の入力信号を、光源12に送信する(S14)。光源12は、投影輝度振幅A・STLの粗い格子縞36Aの像を、測定対象物50の被測定面22に投影する(S16)。
(2) Actual measurement process As shown in FIG. 1, the measuring object 50 is arrange | positioned on the optical path of the light source 12 (S10). Next, the grid pattern creating means 23 transmits image data of the coarse grid pattern 36A to the light source 12 (S12). At this time, the input signal adjusting means 14 transmits an input signal of a luminance component suitable for the projection luminance amplitude A · ST L corresponding to the coarse lattice pattern 36A to the light source 12 (S14). The light source 12 projects an image of the coarse grid pattern 36A having a projection luminance amplitude A · ST L onto the measurement target surface 22 of the measurement object 50 (S16).

位相変位手段16は、被測定面22に投影された粗い格子縞36Aの像の位相を変化させる(S18)。例えば、π/2、π、3π/2の順に位相を変化させる。撮像手段26は、被測定面22に投影された、変位する粗い格子縞36Aの像を撮像する(S20)。相対位相算出手段28は、撮像手段26が撮像した粗い格子縞36Aの画像に基づいて、位相φa’(i,j)を求める(S22)。位相φa’(i,j)の算出は、撮像面18の全座標(全撮像素子)、または任意の座標に対して行う。 The phase displacing means 16 changes the phase of the image of the coarse grating fringe 36A projected on the measurement surface 22 (S18). For example, the phase is changed in the order of π / 2, π, 3π / 2. The image pickup means 26 picks up an image of the displaced coarse lattice fringes 36A projected on the measurement surface 22 (S20). The relative phase calculation unit 28 obtains the phase φ a ′ (i, j) based on the image of the coarse lattice pattern 36A captured by the imaging unit 26 (S22). The calculation of the phase φ a ′ (i, j) is performed for all coordinates (all imaging elements) on the imaging surface 18 or arbitrary coordinates.

次に、格子縞作成手段23は、細格子縞36Bの画像データを光源12に送信する(S24)。このとき、入力信号調整手段14は、細格子縞36Bに対応した投影輝度振幅A・STMに適合した輝度成分の入力信号を、光源12に送信する(S26)。光源12は、投影輝度振幅A・STMの細格子縞36Bの像を、測定対象物50の被測定面22に投影する(S28)。以降は、上記ステップ(S18)、(S20)及び(S22)と同様の処理を行って、細格子縞36Bの画像に基づいて、相対位相φbk’(i,j)を求める。 Next, the grid pattern creating means 23 transmits the image data of the fine grid pattern 36B to the light source 12 (S24). At this time, the input signal adjusting means 14 transmits an input signal of a luminance component suitable for the projection luminance amplitude A · ST M corresponding to the fine grid stripes 36B to the light source 12 (S26). The light source 12 projects an image of the fine grid stripes 36B having the projection luminance amplitude A · ST M onto the measurement target surface 22 of the measurement object 50 (S28). Thereafter, the same processing as in steps (S18), (S20), and (S22) is performed, and the relative phase φ bk ′ (i, j) is obtained based on the image of the fine lattice stripes 36B.

次に、格子縞作成手段23は、微細格子縞36Cの画像データを光源12に送信する(S30)。このとき、入力信号調整手段14は、微細格子縞36Cに対応した投影輝度振幅A・STHに適合した輝度成分の入力信号を、光源12に送信する(S32)。光源12は、投影輝度振幅A・STHの微細格子縞36Cの像を、測定対象物50の被測定面22に投影する(S34)。以降は、上記ステップ(S18)、(S20)及び(S22)と同様の処理を行って、微細格子縞36Cの画像に基づいて、相対位相φck’(i,j)を求める。 Next, the grid pattern creating means 23 transmits the image data of the fine grid pattern 36C to the light source 12 (S30). At this time, the input signal adjusting unit 14 transmits an input signal of a luminance component suitable for the projection luminance amplitude A · ST H corresponding to the fine grid stripes 36C to the light source 12 (S32). The light source 12 projects an image of the fine grid pattern 36C having the projection luminance amplitude A · ST H onto the measurement target surface 22 of the measurement object 50 (S34). Thereafter, the same processing as in steps (S18), (S20), and (S22) is performed, and the relative phase φ ck ′ (i, j) is obtained based on the image of the fine lattice fringes 36C.

次に、絶対位相算出手段30は、位相φa’(i,j)、相対位相φbk’(i,j)、及び相対位相φck’(i,j)を用いて、絶対位相φ(i,j)の絞込みを行う(S36)。また、これと並行して、位相−y座標算出手段32は、上記(1−2)にて求めた関係から、絶対位相φ(i,j)に対応するy座標を導き出す(S38)。 Next, the absolute phase calculation means 30 uses the phase φ a ′ (i, j), the relative phase φ bk ′ (i, j), and the relative phase φ ck ′ (i, j) to calculate the absolute phase φ ( (i, j) is narrowed down (S36). In parallel with this, the phase-y coordinate calculation means 32 derives the y coordinate corresponding to the absolute phase φ (i, j) from the relationship obtained in (1-2) (S38).

具体的には、位相φa’(i,j)と関数ya(i,j)=fa(φ(i,j))から、y座標ya’(i,j)を算出する。次に、相対位相φbk’(i,j)と関数yb(i,j)=fb(φ(i,j))から、y座標候補ybk’(i,j)を得る。さらに、ybk’(i,j)のうち、最もya’(i,j)に近いものをyb’(i,j)として抽出する。次に、相対位相φck’(i,j)と関数yc(i,j)=fc(φ(i,j))から、y座標候補yck’(i,j)を得る。yck’(i,j)のうち、最もyb’(i,j)に近いものを、測定点のy座標とする(yc’(i,j)=y(i,j))。また、yc’(i,j)に対応する位相φc’(i,j)を絶対位相φ(i,j)とする。 Specifically, the phase φ a '(i, j) as a function y a (i, j) = f a (φ (i, j)) from, y-coordinate y a' is calculated (i, j) a. Next, a y-coordinate candidate y bk ′ (i, j) is obtained from the relative phase φ bk ′ (i, j) and the function y b (i, j) = f b (φ (i, j)). Further, y bk '(i, j ) among the most y a' extracts (i, j) to be close to y b '(i, j) as a. Next, to obtain the relative phase φ ck '(i, j) as a function y c (i, j) = f c (φ (i, j)) from, y coordinate candidate y ck' a (i, j). Among y ck ′ (i, j), the one closest to y b ′ (i, j) is set as the y coordinate of the measurement point (y c ′ (i, j) = y (i, j)). Further, the phase φ c ′ (i, j) corresponding to y c ′ (i, j) is defined as the absolute phase φ (i, j).

次に、y座標−xz座標算出手段34は、上記(1−3)にて求めた関係から、y(i,j)に対応するx(i,j)及びz(i,j)を導き出す(S40)。すべての、または任意の撮像面18上の座標(撮像素子)について、対応する被測定面上の測定点のx,y,z座標が求められると、演算部20は、これらの座標を繋げて被測定面の三次元形状を作成する(S42)。   Next, the y coordinate-xz coordinate calculation means 34 derives x (i, j) and z (i, j) corresponding to y (i, j) from the relationship obtained in (1-3) above. (S40). When the x, y, and z coordinates of the measurement points on the corresponding measurement target surface are obtained for all or arbitrary coordinates (imaging element) on the imaging surface 18, the calculation unit 20 connects these coordinates. A three-dimensional shape of the surface to be measured is created (S42).

なお、被測定面が光沢面である場合などに、撮像面18上の一部の受光輝度が飽和レベルを超過する場合がある。他方、撮像面18上の一部の受光輝度が、位相φを求めるには過小である場合がある。この様な場合には、飽和レベルを超過した領域や受光輝度が過小な領域を除外して、位相φを求めるようにしてもよい。言い換えると、撮像面18のうち、受光輝度が所定の許容範囲内に収まる領域に基づいて、被測定面22の形状を算出するようにしてもよい。   Note that, for example, when the surface to be measured is a glossy surface, a part of the received light luminance on the imaging surface 18 may exceed the saturation level. On the other hand, a part of the received light luminance on the imaging surface 18 may be too small to obtain the phase φ. In such a case, the phase φ may be obtained by excluding a region where the saturation level is exceeded or a region where the received light luminance is too small. In other words, the shape of the surface to be measured 22 may be calculated based on a region of the imaging surface 18 in which the received light luminance falls within a predetermined allowable range.

さらに、当該領域における被測定面22の形状算出が完了した後に、撮像面18の、受光輝度が許容範囲内に収まる領域を変更させてもよい。例えば、光源12の投影輝度振幅を変更させることで、受光輝度が許容範囲内に収まる領域を変更させてもよい。   Furthermore, after the calculation of the shape of the measurement target surface 22 in the region is completed, the region of the imaging surface 18 in which the received light luminance falls within the allowable range may be changed. For example, the region where the received light luminance falls within the allowable range may be changed by changing the projection luminance amplitude of the light source 12.

また、投影輝度振幅を変更させる際には、空間周期の異なる格子縞画像のそれぞれの投影輝度振幅の比を保ったまま、それぞれの投影輝度振幅を変更させることが好適である。こうすることにより、受光輝度振幅を、それぞれの格子縞画像間で同一にすることが可能となる。例えば、(1−1)投影輝度成分のキャリブレーションにて設定した、投影輝度振幅STL’=A・STL、STM’=A・STM、及びSTH’=A・STHの係数Aを調整することで、それぞれの投影輝度振幅を変更させてもよい。 Further, when changing the projection luminance amplitude, it is preferable to change each projection luminance amplitude while maintaining the ratio of the projection luminance amplitudes of the lattice fringe images having different spatial periods. By doing so, it is possible to make the light reception luminance amplitude the same between the respective checkered images. For example, (1-1) coefficients of projection luminance amplitudes ST L ′ = A · ST L , ST M ′ = A · ST M , and ST H ′ = A · ST H set in the calibration of the projection luminance component By adjusting A, each projection luminance amplitude may be changed.

なお、上記の実施形態においては、投受光光学系のMTFによる受光輝度振幅の低下を、(1−1)投影輝度成分のキャリブレーションのように、入力信号調整手段14によって補償していたが、この形態に限られない。例えば、図10に例示するように、撮像手段26または演算装置24に、撮像面18に対する露光時間を定める、露光調整手段52を設けてもよい。露光調整手段52は、撮像手段26のシャッタースピードを調整する機能を備えていてよい。   In the above embodiment, the decrease in the light reception luminance amplitude due to the MTF of the light projecting / receiving optical system is compensated by the input signal adjusting means 14 as in (1-1) calibration of the projection luminance component. It is not restricted to this form. For example, as illustrated in FIG. 10, an exposure adjustment unit 52 that determines an exposure time for the imaging surface 18 may be provided in the imaging unit 26 or the arithmetic unit 24. The exposure adjustment unit 52 may have a function of adjusting the shutter speed of the imaging unit 26.

露光調整手段52は、相対的に空間周期の短い格子縞36を被測定面22に投影したときの、撮像面18に対する露光時間が、相対的に空間周期の長い格子縞36を被測定面22に投影したときの、撮像面18に対する露光時間よりも長くなるように、撮像面18への露光時間を定めることが好適である。言い換えると、所定の空間周期の第1の格子縞像と、第1の格子縞像よりも空間周期の長い第2の格子縞像とを、被測定面22に選択的に投影する場合には、第1の格子縞像を被測定面22に投影するときの露光時間を、第2の格子縞像を被測定面22に投影するときの露光時間よりも長く設定してよい。このような構成を備えることで、投受光光学系のMTFによる受光輝度振幅の低下を補償することができる。   The exposure adjusting unit 52 projects the lattice fringe 36 having a relatively long spatial period on the surface to be measured 22 when the lattice fringe 36 having a relatively short spatial cycle is projected on the surface to be measured 22. It is preferable to determine the exposure time for the imaging surface 18 so as to be longer than the exposure time for the imaging surface 18 at that time. In other words, when the first lattice fringe image having a predetermined spatial period and the second lattice fringe image having a spatial period longer than the first lattice fringe image are selectively projected on the measurement target surface 22, The exposure time when projecting the lattice fringe image onto the surface to be measured 22 may be set longer than the exposure time when projecting the second lattice fringe image onto the surface to be measured 22. With such a configuration, it is possible to compensate for a decrease in received light amplitude due to the MTF of the light projecting / receiving optical system.

ここで、上述したように、撮像面18上の一部の受光輝度が飽和レベルを超過する場合や、撮像面18上の一部の受光輝度が、位相φを求めるには過小である場合がある。この様な場合には、撮像面18のうち、受光輝度が所定の許容範囲内に収まる領域に基づいて、被測定面22の形状を算出するようにしてもよい。さらに、撮像面18に対する露光時間を変更させることで、撮像面18の、受光輝度が許容範囲内に収まる領域を変更させてもよい。また、空間周期の異なる格子縞画像のそれぞれの投影輝度振幅の比を保ったまま、それぞれの投影輝度振幅を変更させる制御を行った上で、露光時間の変更を行ってもよい。このようにすることで、露光時間の変更のみ、または、投影輝度振幅の変更のみを行う場合に比べて、受光輝度の飽和レベルの超過をより効果的に防止することが可能となる。   Here, as described above, there is a case where a part of the light receiving luminance on the imaging surface 18 exceeds the saturation level, or a part of the light receiving luminance on the imaging surface 18 is too small to obtain the phase φ. is there. In such a case, the shape of the surface to be measured 22 may be calculated based on a region of the imaging surface 18 in which the received light luminance falls within a predetermined allowable range. Further, by changing the exposure time with respect to the imaging surface 18, the region of the imaging surface 18 in which the received light luminance falls within the allowable range may be changed. In addition, the exposure time may be changed after performing control to change each projection luminance amplitude while maintaining the ratio of the projection luminance amplitudes of the lattice fringe images having different spatial periods. By doing so, it is possible to more effectively prevent the saturation level of the received light luminance from being exceeded as compared with the case where only the exposure time is changed or only the projection luminance amplitude is changed.

また、輝度成分のキャリブレーションや、露光時間の調整に代えて、図11に例示するように、撮像面18上の受光輝度振幅を増幅させる増幅手段54を備えてよい。増幅手段54は、相対的に空間周期の短い格子縞36を被測定面22に投影したときの、撮像面18上の受光輝度振幅の増幅率が、相対的に空間周期の長い格子縞36を被測定面22に投影したときの、撮像面18上の受光輝度振幅の増幅率よりも大きくなるように、増幅率を定めることが好適である。なお、入力信号調整手段14、露光調整手段52、増幅手段54を適宜組み合わせて使用してもよい。言い換えると、所定の空間周期の第1の格子縞像と、第1の格子縞像よりも空間周期の長い第2の格子縞像とを、被測定面22に選択的に投影する場合には、第1の格子縞像を被測定面22に投影するときの増幅率を、第2の格子縞像を被測定面22に投影するときの増幅率よりも大きくなるように設定してよい。   Further, in place of the calibration of the luminance component and the adjustment of the exposure time, an amplification means 54 for amplifying the received light luminance amplitude on the imaging surface 18 may be provided as illustrated in FIG. The amplifying unit 54 measures the lattice fringe 36 whose amplification factor of the received light intensity on the imaging surface 18 has a relatively long spatial period when the lattice fringe 36 having a relatively short spatial period is projected onto the surface to be measured 22. It is preferable that the amplification factor is determined so as to be larger than the amplification factor of the light reception luminance amplitude on the imaging surface 18 when projected onto the surface 22. The input signal adjusting unit 14, the exposure adjusting unit 52, and the amplifying unit 54 may be used in appropriate combination. In other words, when the first lattice fringe image having a predetermined spatial period and the second lattice fringe image having a spatial period longer than the first lattice fringe image are selectively projected on the measurement target surface 22, The amplification factor when projecting the lattice fringe image onto the surface to be measured 22 may be set to be larger than the amplification factor when projecting the second lattice fringe image onto the surface to be measured 22.

<具体例1>
次に、上述のキャリブレーション及び測定原理を用いた三次元形状測定の具体例について説明する。なお、本具体例では、光源12として、格子縞の画像を投影可能なプロジェクタを使用した。プロジェクタの設定可能な輝度範囲は8bit(0〜255)であった。
<Specific example 1>
Next, a specific example of three-dimensional shape measurement using the above-described calibration and measurement principle will be described. In this specific example, a projector capable of projecting a checkerboard image is used as the light source 12. The settable brightness range of the projector was 8 bits (0 to 255).

まず、3つの異なる周期のcos波形の格子縞36A〜36Cを用いて、形状計測を行った。格子縞36A〜36Cの周期はそれぞれ、λH=1.1mm、λM=5.5mm、λL=44mmであった。 First, shape measurement was performed using lattice fringes 36A to 36C having three different cosine waveforms. The periods of the lattice fringes 36A to 36C were λ H = 1.1 mm, λ M = 5.5 mm, and λ L = 44 mm, respectively.

上記格子縞36A〜36Cに対して、上記(1−1)投影輝度成分のキャリブレーションを実施した。まず、形状既知のセラミック平板を光源12の光路上に置く。格子縞作成手段23は、光源12からcos波の濃淡を持つ格子縞36A〜36Cを順に投影する。ここで、光源12の投影輝度振幅について、オフセットを125、振幅を95に設定した。   The calibration of the (1-1) projection luminance component was performed on the lattice fringes 36A to 36C. First, a ceramic flat plate having a known shape is placed on the optical path of the light source 12. The lattice fringe creating means 23 sequentially projects the lattice fringes 36A to 36C having the density of the cosine wave from the light source 12. Here, regarding the projection luminance amplitude of the light source 12, the offset was set to 125 and the amplitude was set to 95.

次に、セラミック平板に順に投影された格子縞36A〜36Cの画像を、撮像手段26で撮像する。次に、格子縞36A〜36Cの各周期で得られたcos波画像から格子縞36A〜36Cごとの受光輝度振幅を求めた。   Next, images of the lattice fringes 36 </ b> A to 36 </ b> C projected in order on the ceramic flat plate are picked up by the image pickup means 26. Next, the light reception luminance amplitude for each of the lattice fringes 36A to 36C was obtained from the cosine wave image obtained at each period of the lattice fringes 36A to 36C.

図12に、格子縞36A〜36Cの空間周期λと受光輝度振幅Rの関係を示す。この図から、RL=1、RM=0.84、RH=0.35が得られる。これらの値から、STL=RH=0.35、STM=RH/RM=0.42、STH=1が得られる。これらの値と、計測範囲の最近点で撮像素子の輝度レベルが飽和しないという二つの条件から、光源12の投影輝度設定値を定めた。まず、全ての空間周期のオフセットについて、8bit(0〜255)の輝度のうち、125とした。さらに、λHの振幅を115、λMの振幅を48、λLの振幅を40とした。上述したように、MTF特性を考慮しない時の格子縞36A〜36Cの振幅は全て95であったので、λHの振幅(115)を大きくできた。これらの値を基に、周期λH、λM、λLの格子縞の位相が各々π/2異なる計12種類(=3周期×4位相)のcos波形格子縞を作成して、これらの像を撮像した。 FIG. 12 shows the relationship between the spatial period λ of the lattice fringes 36A to 36C and the light reception luminance amplitude R. From this figure, R L = 1, R M = 0.84, and R H = 0.35 are obtained. From these values, ST L = R H = 0.35, ST M = R H / R M = 0.42, and ST H = 1 are obtained. The projection brightness setting value of the light source 12 was determined from these values and the two conditions that the brightness level of the image sensor does not saturate at the closest point of the measurement range. First, with respect to all spatial period offsets, 125 out of the luminance of 8 bits (0 to 255) was set. Furthermore, the amplitude of λ H is 115, the amplitude of λ M is 48, and the amplitude of λ L is 40. As described above, since the amplitudes of the lattice fringes 36A to 36C when the MTF characteristics are not considered are all 95, the amplitude (115) of λ H can be increased. Based on these values, a total of 12 types (= 3 periods × 4 phases) of cosine waveform lattice fringes having phases of λ H , λ M , and λ L , each having a phase difference of π / 2, are created. I took an image.

セラミック平板を精密ステージに載せてy方向に移動させ、その位置を計測した結果を図13に示す。図13では、位相φから求めたy座標と、実際の精密ステージ上のy座標との差が、ステージ位置ごとに示されている。白抜き丸プロット(○)は、格子縞ごとに投影輝度振幅を変更させたときの計測結果である。また、塗りつぶし丸プロット(●)は、すべての格子縞に対して一定の投影輝度振幅を設定したときの計測結果である。この図に示されているように、投影輝度振幅を格子縞ごとに調整することで、計算上のy座標と実際のy座標との誤差が小さくなった。   FIG. 13 shows the result of measuring the position of the ceramic flat plate placed on the precision stage and moving in the y direction. In FIG. 13, the difference between the y coordinate obtained from the phase φ and the actual y coordinate on the precision stage is shown for each stage position. A white circle plot (◯) is a measurement result when the projection luminance amplitude is changed for each checkered pattern. Also, a filled circle plot (●) is a measurement result when a constant projection luminance amplitude is set for all the lattice fringes. As shown in this figure, the error between the calculated y coordinate and the actual y coordinate is reduced by adjusting the projection luminance amplitude for each lattice pattern.

<具体例2>
次に、光沢面からなる被測定面22が鏡面反射している場合の計測例について説明する。本具体例も、光源12として、輝度範囲が8bit(0〜255)のプロジェクタを使用した。また、本具体例では、撮像面18への露光時間を調整する露光調整手段52を備えている。具体的には、露光調整手段52は、撮像手段26のシャッタースピードを調整するシャッター速度変更手段である。
<Specific example 2>
Next, a measurement example in the case where the measured surface 22 made of a glossy surface is specularly reflected will be described. Also in this specific example, a projector having a luminance range of 8 bits (0 to 255) was used as the light source 12. In this specific example, an exposure adjusting means 52 for adjusting the exposure time for the imaging surface 18 is provided. Specifically, the exposure adjustment unit 52 is a shutter speed changing unit that adjusts the shutter speed of the imaging unit 26.

図10に示すように、光源12の光路上に、光沢度標準板からなる測定対象物50を置く。このとき、光源12の光軸に対する被測定面22の傾きθが15°となるように、測定対象物50を設置した。   As shown in FIG. 10, a measurement object 50 made of a gloss standard plate is placed on the optical path of the light source 12. At this time, the measurement object 50 was installed so that the inclination θ of the measured surface 22 with respect to the optical axis of the light source 12 was 15 °.

本具体例でも、3つの異なる周期λH=1.1mm、λM=5.5mm、λL=44mmのcos波形格子縞36A〜36Cを用いた。測定対象物50として用いた光沢度標準板は、60°光沢度が1〜93%で異なる9枚(G1〜G9)を用いた。この光沢度標準板は、例えば、アイキ社製のものであってよい。また、光沢度は、コニカミノルタ社製の光沢計GM−268Plusで計測した。各標準板の光沢度を図14に示す。 Also in this specific example, cos waveform lattice fringes 36A to 36C having three different periods λ H = 1.1 mm, λ M = 5.5 mm, and λ L = 44 mm were used. Nine sheets (G1 to G9) having 60 ° glossiness of 1 to 93% and different glossiness standard plates used as the measurement object 50 were used. This gloss standard plate may be, for example, manufactured by Aiki. The glossiness was measured with a gloss meter GM-268Plus manufactured by Konica Minolta. The glossiness of each standard plate is shown in FIG.

まず、格子縞36A〜36Cの振幅減衰量を計測した。光沢度標準板の傾きθについて、θ=0°として、光源12の光路上(正面)に置き、光源12からcos波の濃淡を持つ周期を変えた格子縞36A〜36Cを順に光沢度標準板に投影し、この投映像を撮像手段26で撮像した。格子縞36A〜36Cの各周期で得られたcos波画像から、格子縞36A〜36Cの周期と振幅との関係を求めた。この測定は、9枚の光沢板(G1〜G9)に対して行った。この測定結果をもとに、図15に示すような、周期と振幅の関係を得た。なお、振幅は、9枚の光沢板の測定から得られた振幅の平均値を用いている。図15の結果は、具体例1における、図12の結果と特性が異なっているが、表面反射特性の違いによるものと考えられる。なお、光沢度標準板が小さく、周期λ=30mmまでの格子縞までしか投影できなかったため、λLの振幅値は外挿した。 First, the amplitude attenuation amount of the lattice fringes 36A to 36C was measured. With respect to the inclination θ of the glossiness standard plate, θ = 0 ° is set on the optical path (front side) of the light source 12, and the lattice fringes 36 </ b> A to 36 </ b> C from the light source 12 with different cosine wave shades are changed to the glossiness standard plate in order. The projected image was captured by the imaging means 26. From the cosine wave image obtained at each period of the lattice fringes 36A to 36C, the relationship between the period and the amplitude of the lattice fringes 36A to 36C was obtained. This measurement was performed on nine glossy plates (G1 to G9). Based on this measurement result, the relationship between the period and the amplitude as shown in FIG. 15 was obtained. In addition, the average value of the amplitude obtained from the measurement of nine glossy plates is used for the amplitude. The result of FIG. 15 is different from the result of FIG. 12 in the specific example 1, but is considered to be due to the difference in the surface reflection characteristics. In addition, since the glossiness standard plate was small and could project only up to the lattice fringes with a period λ = 30 mm, the amplitude value of λ L was extrapolated.

図15から、RL=1.02、RM=0.78、RH=0.7を得た。さらに、これらの値から、STL=0.69、STM=0.88、STH=1が得られた。これらの値と計測範囲の最近点で撮像素子の輝度レベルが飽和しないという条件から、光源12の輝度設定値を設定した。具体的には、全ての周期のオフセットを125とし、λHの振幅を115、λMの振幅を100、λLの振幅を78とした。MTF特性を考慮しない時の格子縞36A〜36Cの振幅は95であったので、λHの振幅を大きくできた。 From FIG. 15, R L = 1.02, R M = 0.78, and R H = 0.7 were obtained. Further, from these values, ST L = 0.69, ST M = 0.88, and ST H = 1 were obtained. The brightness setting value of the light source 12 was set on the condition that the brightness level of the image sensor does not saturate at these values and the closest point of the measurement range. Specifically, the offset of all periods was 125, the amplitude of λ H was 115, the amplitude of λ M was 100, and the amplitude of λ L was 78. Since the amplitude of the lattice fringes 36A to 36C when the MTF characteristics were not taken into account was 95, the amplitude of λ H could be increased.

格子縞作成手段23は、これらの値を基に、周期λH、λM、λLの格子縞の位相が各々π/2異なる計12種類のcos波形格子縞を作成する。ここで、光沢度標準板の格子縞画像を図16及び図17に示す。括弧内の秒数はシャッター速度を表している。図16、17に示されているように、光沢度が高いほど、格子縞画像がスポット状になる。このスポット部を計測領域として、その3次元座標を求めた。 Based on these values, the lattice fringe creating means 23 creates a total of 12 types of cos waveform lattice fringes having phases of λ H , λ M , and λ L each having a phase difference of π / 2. Here, the checkered image of the glossiness standard plate is shown in FIGS. The number of seconds in parentheses represents the shutter speed. As shown in FIGS. 16 and 17, the higher the glossiness is, the more the lattice pattern image is spotted. Using this spot portion as a measurement region, the three-dimensional coordinates were obtained.

また、光沢度標準板の撮像時に、撮像素子の輝度飽和を抑制するために、露光調整手段52で、シャッター速度を1/15秒から1/80000秒まで約10倍ごとに変化させて格子縞を撮像した。   Further, in order to suppress the luminance saturation of the image pickup device during the image pickup of the glossiness standard plate, the exposure adjustment means 52 changes the shutter speed every 10 times from 1/15 seconds to 1/80000 seconds so that the lattice fringes are generated. I took an image.

まず、シャッター速度を1/15秒に設定する。そして、粗い格子縞36A、細格子縞36B、微細格子縞36Cの順に投影して、具体例1と同様に光沢度標準板の3次元座標を求めた。このとき、計測領域内で輝度飽和した撮像素子がある場合には、シャッター速度を早くして再度撮像した。例えば、1/15秒で飽和した場合は、シャッター速度を1/120秒にして再度撮像した。この速度でも飽和する撮像素子がある場合は、さらにシャッター速度を1/1000秒に上げて撮像した。このように飽和する撮像素子が無くなるまで、シャッター速度を上げて計測を行った。   First, the shutter speed is set to 1/15 seconds. Then, the coarse lattice fringes 36A, the fine lattice fringes 36B, and the fine lattice fringes 36C are projected in this order, and the three-dimensional coordinates of the glossiness standard plate are obtained in the same manner as in the first specific example. At this time, if there is an image sensor whose luminance is saturated in the measurement area, the image is taken again at a higher shutter speed. For example, when the image is saturated at 1/15 seconds, the image is taken again at a shutter speed of 1/120 seconds. If there is an image sensor that saturates even at this speed, the image was taken with the shutter speed increased to 1/1000 second. The measurement was performed at an increased shutter speed until no image sensor was saturated.

このようにして得られた3次元座標計測値から、光沢度標準板の3次元平面を最小自乗法で求めた。さらに、実際の3次元平面の座標と計測した座標との差を位置ばらつきとして求めた。その結果を図18に示す。白抜き菱形プロット(◇)は、格子縞ごとに投影輝度振幅及びシャッタースピードを変更させたときの計測結果である。また、塗りつぶし菱形プロット(◆)は、すべての格子縞に対して一定の投影輝度振幅を設定したときの計測結果である。投影輝度振幅値を変えて投影することにより、投影輝度振幅値を同一にして投影した場合より、標準板G1〜G8で位置ばらつきが0.3〜3.8μm小さくなった。また、投影輝度振幅値を同一にした場合に、光沢標準板G9は誤計測となったが、投影輝度振幅値及びシャッタースピードを変えて投影することにより、計測が可能となった。   From the three-dimensional coordinate measurement values obtained in this way, the three-dimensional plane of the glossiness standard plate was obtained by the method of least squares. Further, the difference between the coordinates of the actual three-dimensional plane and the measured coordinates was obtained as the position variation. The result is shown in FIG. A white diamond plot (◇) is a measurement result when the projection luminance amplitude and the shutter speed are changed for each checkered pattern. Further, the filled diamond plot (♦) is a measurement result when a certain projection luminance amplitude is set for all the lattice fringes. By projecting while changing the projection luminance amplitude value, the position variations of the standard plates G1 to G8 are smaller by 0.3 to 3.8 μm than when the projection luminance amplitude value is the same. In addition, when the projection luminance amplitude values were the same, the glossy standard plate G9 was erroneously measured, but measurement was possible by changing the projection luminance amplitude value and the shutter speed and projecting.

10 形状測定装置、12 光源、14 入力信号調整手段、16 位相変位手段、18 撮像面、20 演算部、22 被測定面、23 格子縞作成手段、24 演算装置、26 撮像手段、28 相対位相算出手段、30 絶対位相算出手段、32 位相−y座標算出手段、34 y座標−xz座標算出手段、36 格子縞、40 標準板、42 yステージ、44 グリッド格子、50 測定対象物、52 露光調整手段、54 増幅手段。   DESCRIPTION OF SYMBOLS 10 Shape measuring device, 12 Light source, 14 Input signal adjustment means, 16 Phase displacement means, 18 Imaging surface, 20 Computation part, 22 Surface to be measured, 23 Plaid preparation means, 24 Arithmetic device, 26 Imaging means, 28 Relative phase calculation means , 30 absolute phase calculation means, 32 phase-y coordinate calculation means, 34 y coordinate-xz coordinate calculation means, 36 grid stripes, 40 standard plate, 42 y stage, 44 grid grating, 50 measurement object, 52 exposure adjustment means, 54 Amplification means.

Claims (11)

第1空間周期及び第1投影輝度振幅を有する第1格子縞画像を、被測定面に投影する、第1投影手段と、
第2空間周期及び第2投影輝度振幅を有する第2格子縞画像を、被測定面に投影する、第2投影手段と、
被測定面に投影された格子縞画像の位相を変化させることが可能な、位相変位手段と、
被測定面に投影された格子縞画像を撮像することが可能な、撮像手段と、
前記位相の変化に対応する、前記撮像手段の受光輝度の変化に基づいて、被測定面の形状を算出する、演算部と、
を備え、
前記第1空間周期は、前記第2空間周期よりも短く、
前記第1投影輝度振幅は、前記第2投影輝度振幅より大きい、
形状測定装置。
First projection means for projecting a first checkered image having a first spatial period and a first projected luminance amplitude onto a surface to be measured;
Second projecting means for projecting a second checkered image having a second spatial period and a second projected luminance amplitude onto a surface to be measured;
A phase displacement means capable of changing the phase of the lattice fringe image projected on the measurement surface;
An imaging means capable of imaging a checkerboard image projected on the measurement surface;
A calculation unit that calculates a shape of a surface to be measured based on a change in light receiving luminance of the imaging unit corresponding to a change in the phase;
With
The first spatial period is shorter than the second spatial period;
The first projection luminance amplitude is greater than the second projection luminance amplitude;
Shape measuring device.
請求項1記載の形状測定装置であって、
被測定面に投影された前記第1格子縞画像を撮像するときの、前記撮像手段の撮像面上の受光輝度振幅が、被測定面に投影された前記第2格子縞画像を撮像するときの、前記撮像面上の受光輝度振幅と略等しくなるように、前記第1投影輝度振幅及び第2投影輝度振幅を制御することが可能な、形状測定装置。
The shape measuring device according to claim 1,
When the first checkered image projected on the surface to be measured is picked up, the received light amplitude on the image pickup surface of the image pickup means picks up the second checkered image projected on the surface to be measured. A shape measuring apparatus capable of controlling the first projection luminance amplitude and the second projection luminance amplitude so as to be substantially equal to a light reception luminance amplitude on an imaging surface.
請求項1または2に記載の形状測定装置であって、
被測定面に投影された前記第1格子縞画像を撮像するときの、前記撮像手段の撮像面上の受光輝度振幅と、被測定面に投影された前記第2格子縞画像を撮像するときの、前記撮像面上の受光輝度振幅が、輝度飽和レベル未満となるように、前記第1投影輝度振幅と前記第2投影輝度振幅を制御することが可能な、形状測定装置。
The shape measuring device according to claim 1 or 2,
When imaging the first checkered image projected on the surface to be measured, the light reception luminance amplitude on the image pickup surface of the imaging means, and when capturing the second checkered image projected on the surface to be measured, A shape measuring apparatus capable of controlling the first projection luminance amplitude and the second projection luminance amplitude so that a light reception luminance amplitude on an imaging surface is less than a luminance saturation level.
請求項2または3に記載の形状測定装置であって、
前記第1投影輝度振幅と前記第2投影輝度振幅の比を保ったまま、前記第1投影輝度振幅と前記第2投影輝度振幅を制御することが可能な、形状測定装置。
The shape measuring device according to claim 2 or 3,
A shape measuring apparatus capable of controlling the first projection luminance amplitude and the second projection luminance amplitude while maintaining a ratio between the first projection luminance amplitude and the second projection luminance amplitude.
請求項1から4のいずれかに記載の形状測定装置であって、
前記演算部は、前記撮像手段の撮像面のうち、受光輝度が所定範囲内に収まる領域に基づいて、被測定面の形状を算出し、
前記第1投影輝度振幅及び第2投影輝度振幅を変更させることで、前記受光輝度が前記所定範囲内に収まる領域を変更させる、形状測定装置。
The shape measuring apparatus according to any one of claims 1 to 4,
The calculation unit calculates a shape of the surface to be measured based on an area of the imaging surface of the imaging unit where the received light luminance falls within a predetermined range,
A shape measuring apparatus that changes a region in which the received light luminance falls within the predetermined range by changing the first projection luminance amplitude and the second projection luminance amplitude.
第1空間周期を有する第1格子縞画像を、被測定面に投影する、第1投影手段と、
第2空間周期を有する第2格子縞画像を、被測定面に投影する、第2投影手段と、
被測定面に投影された格子縞画像の位相を変化させることが可能な、位相変位手段と、
被測定面に投影された格子縞画像を撮像することが可能な、撮像手段と、
被測定面に投影された前記第1格子縞画像を前記撮像手段に撮像させる際に、露光時間を第1露光時間に制御する、第1露光調整手段と、
被測定面に投影された前記第2格子縞画像を前記撮像手段に撮像させる際に、露光時間を第2露光時間に制御する、第1露光調整手段と、
前記位相の変化に対応する、前記撮像手段の受光輝度の変化に基づいて、被測定面の形状を算出する、演算部と、
を備え、
前記第1空間周期は、前記第2空間周期よりも短く、
前記第1露光時間は、前記第2露光時間よりも長い、
形状測定装置。
First projecting means for projecting a first checkered image having a first spatial period onto a surface to be measured;
A second projection means for projecting a second checkered image having a second spatial period onto the surface to be measured;
A phase displacement means capable of changing the phase of the lattice fringe image projected on the measurement surface;
An imaging means capable of imaging a checkerboard image projected on the measurement surface;
A first exposure adjusting means for controlling an exposure time to a first exposure time when the imaging means picks up the first checkered image projected on the measurement surface;
A first exposure adjusting means for controlling an exposure time to a second exposure time when the imaging means picks up the second checkered image projected on the measurement surface;
A calculation unit that calculates a shape of a surface to be measured based on a change in light receiving luminance of the imaging unit corresponding to a change in the phase;
With
The first spatial period is shorter than the second spatial period;
The first exposure time is longer than the second exposure time;
Shape measuring device.
請求項6記載の形状測定装置であって、
被測定面に投影された前記第1格子縞画像を撮像するときの、前記撮像手段の撮像面上の第1受光輝度振幅が、被測定面に投影された前記第2格子縞画像を撮像するときの、前記撮像面上の第2受光輝度振幅と略等しくなるように、前記第1露光時間及び第2露光時間を制御することが可能な、形状測定装置。
The shape measuring device according to claim 6,
When imaging the first checkered image projected on the surface to be measured, the first light reception luminance amplitude on the image pickup surface of the imaging means when capturing the second checkered image projected on the surface to be measured The shape measuring apparatus capable of controlling the first exposure time and the second exposure time so as to be substantially equal to the second light receiving luminance amplitude on the imaging surface.
請求項6または7に記載の形状測定装置であって、
被測定面に投影された前記第1格子縞画像を撮像するときの、前記撮像手段の撮像面上の第1受光輝度振幅と、被測定面に投影された前記第2格子縞画像を撮像するときの、前記撮像面上の第2受光輝度振幅が、輝度飽和レベル未満となるように、前記第1露光時間及び第2露光時間を制御することが可能な、形状測定装置。
The shape measuring device according to claim 6 or 7,
When imaging the first checkered image projected on the measurement surface, the first received light amplitude on the imaging surface of the imaging means and when capturing the second checkered image projected on the measurement surface. The shape measuring apparatus capable of controlling the first exposure time and the second exposure time so that the second light reception luminance amplitude on the imaging surface is less than the luminance saturation level.
請求項6から8のいずれかに記載の形状測定装置であって、
前記演算部は、前記撮像手段の撮像面のうち、受光輝度が所定範囲内に収まる領域に基づいて、被測定面の形状を算出し、
前記第1露光時間及び第2露光時間を変更させることで、前記受光輝度が前記所定範囲内に収まる領域を変更させる、形状測定装置。
The shape measuring device according to any one of claims 6 to 8,
The calculation unit calculates a shape of the surface to be measured based on an area of the imaging surface of the imaging unit where the received light luminance falls within a predetermined range,
A shape measuring apparatus that changes a region in which the received light luminance falls within the predetermined range by changing the first exposure time and the second exposure time.
第1空間周期を有する第1格子縞画像を、被測定面に投影する、第1投影手段と、
第2空間周期を有する第2格子縞画像を、被測定面に投影する、第2投影手段と、
被測定面に投影された格子縞画像の位相を変化させることが可能な、位相変位手段と、
被測定面に投影された格子縞画像を撮像することが可能な、撮像手段と、
被測定面に投影された前記第1格子縞画像を前記撮像手段に撮像させる際に、前記撮像手段の撮像面上の受光輝度振幅を第1増幅率で増幅させる第1増幅手段と、
被測定面に投影された前記第2格子縞画像を前記撮像手段に撮像させる際に、前記撮像手段の撮像面上の受光輝度振幅を第2増幅率で増幅させる第2増幅手段と、
前記位相の変化に対応する、前記撮像手段の増幅後の受光輝度の変化に基づいて、被測定面の形状を算出する、演算部と、
を備え、
前記第1空間周期は、前記第2空間周期よりも短く、
前記第1増幅率は、前記第2増幅率よりも大きい、
形状測定装置。
First projecting means for projecting a first checkered image having a first spatial period onto a surface to be measured;
A second projection means for projecting a second checkered image having a second spatial period onto the surface to be measured;
A phase displacement means capable of changing the phase of the lattice fringe image projected on the measurement surface;
An imaging means capable of imaging a checkerboard image projected on the measurement surface;
A first amplifying unit that amplifies the light reception luminance amplitude on the imaging surface of the imaging unit by a first amplification factor when the imaging unit images the first checkered image projected on the surface to be measured;
A second amplifying means for amplifying the light reception luminance amplitude on the imaging surface of the imaging means by a second amplification factor when the imaging means images the second checkered image projected on the surface to be measured;
A calculation unit that calculates a shape of the surface to be measured based on a change in received light luminance after amplification of the imaging unit corresponding to the change in the phase;
With
The first spatial period is shorter than the second spatial period;
The first amplification factor is greater than the second amplification factor;
Shape measuring device.
第1空間周期を有する第1格子縞画像を、被測定面に投影する、第1投影手段と、
第2空間周期を有する第2格子縞画像を、被測定面に投影する、第2投影手段と、
被測定面に投影された格子縞画像の位相を変化させることが可能な、位相変位手段と、
被測定面に投影された格子縞画像を撮像することが可能な、撮像手段と、
前記位相の変化に対応する、前記撮像手段の受光輝度の変化に基づいて、被測定面の形状を算出する、演算部と、
を備え、
前記第1空間周期は、前記第2空間周期よりも短く、
被測定面に投影された前記第1格子縞画像を撮像するときの、前記撮像手段の撮像面上の受光輝度振幅は、被測定面に投影された前記第2格子縞画像を撮像するときの、前記撮像面上の受光輝度振幅と略等しい、形状測定装置。
First projecting means for projecting a first checkered image having a first spatial period onto a surface to be measured;
A second projection means for projecting a second checkered image having a second spatial period onto the surface to be measured;
A phase displacement means capable of changing the phase of the lattice fringe image projected on the measurement surface;
An imaging means capable of imaging a checkerboard image projected on the measurement surface;
A calculation unit that calculates a shape of a surface to be measured based on a change in light receiving luminance of the imaging unit corresponding to a change in the phase;
With
The first spatial period is shorter than the second spatial period;
The light receiving luminance amplitude on the imaging surface of the imaging means when imaging the first checkered image projected on the measurement surface is the same as that when the second checkered image projected on the measurement surface is imaged. A shape measuring device that is substantially equal to the amplitude of received light on the imaging surface.
JP2012165607A 2012-07-26 2012-07-26 Shape measuring device Expired - Fee Related JP6019886B2 (en)

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JPWO2019177066A1 (en) * 2018-03-16 2021-01-14 日本電気株式会社 3D shape measuring device, 3D shape measuring method and program
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CN113959364A (en) * 2021-10-22 2022-01-21 华中科技大学 Three-frequency phase unwrapping method and measuring device
CN113959364B (en) * 2021-10-22 2022-08-16 华中科技大学 Three-frequency phase unwrapping method and measuring device

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