JP2009186216A - Three-dimensional shape measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform accurate measurement in three-dimensional shape measurement by a light section method which utilizes a two-dimensional photoelectric conversion element. <P>SOLUTION: The three-dimensional shape measuring device includes: a light-projecting means which has a slit shape and projects a light beam to an object from a first direction in which the intensity of the light beam in the direction perpendicular to the longitudinal direction of the slit has a Gaussian distribution; a changing means for changing the relative position between the light-projecting means and the object; a first imaging means which has a two-dimensional photoelectric conversion element, with logarithmic characteristics in the photoelectric conversion of at least a part of the area and picks up an image of a light beam reflected from the object, by using the two-dimensional photoelectric conversion element from a direction different from the first direction; a detection means for detecting the position of a light beam on the object, based on the output of the first imaging means; and a computing means for computing the three-dimensional shape of the object based on detection results by the detection means at the plurality of different relative positions. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a three-dimensional shape measuring apparatus that measures a three-dimensional shape of a test object based on an output of an imaging unit.

2. Description of the Related Art Conventionally, there is known a technique that uses a two-dimensional photoelectric conversion element having a logarithmic characteristic and that is used as a so-called light-cutting type sensor that projects slit light and measures a three-dimensional shape (eg, Patent Document 1) reference). According to the three-dimensional shape measurement of the light cutting method using a two-dimensional photoelectric conversion element, it is possible to perform stable measurement even for a test object having a high contrast of reflected light.
JP 2005-508759 gazette

  However, when performing a light-cutting three-dimensional shape measurement using a two-dimensional photoelectric conversion element having logarithmic characteristics, the output is converted into linear sensitivity for waveform processing. As a result, there is a problem that the quantization error of A / D conversion at the time of conversion becomes large, particularly in a region with a large amount of light, and is not suitable for precise measurement.

  An object of the three-dimensional shape measuring apparatus of the present invention is to perform highly accurate measurement in a three-dimensional shape measurement of a light section type using a two-dimensional photoelectric conversion element.

  The three-dimensional shape measuring apparatus of the present invention projects a light beam having a slit shape and having a Gaussian distribution in the direction perpendicular to the longitudinal direction of the slit from a first direction to a test object. Projecting means, changing means for changing the relative position of the projecting means and the object to be measured, and a two-dimensional photoelectric conversion element having logarithmic characteristics for photoelectric conversion in at least a part of the area, Based on the output of the first imaging means, the first imaging means for imaging the image of the light beam reflected from the test object from the direction different from the first direction by the two-dimensional photoelectric conversion element, Detection means for detecting the position of the light beam on the test object, and calculation means for calculating the three-dimensional shape of the test object based on detection results by the detection means at a plurality of different relative positions. .

  The first imaging means includes first approximation means for approximating the output of the first imaging means to a quadratic function corresponding to the Gaussian distribution, and the detection means is based on the output approximated to the quadratic function. The position of the light beam may be detected.

  Further, the first approximating means approximates an output accompanying a change with time as a quadratic function as an output of the first imaging means, and the detecting means sets a predetermined position on the test object as the light. The time when the beam passes may be detected.

  In addition, an acquisition unit that acquires an output corresponding to the ambient light component is further provided, and the detection unit outputs the output of the first imaging unit based on the output corresponding to the ambient light component acquired by the acquisition unit. After the correction, the position of the light beam may be detected.

  In addition, a second two-dimensional photoelectric conversion element having logarithmic characteristics for photoelectric conversion in at least a part of the region is provided, and an image of the light beam reflected from the object to be examined is represented in the first direction and the first A second imaging unit that captures an image with the second two-dimensional photoelectric conversion element from a second direction different from a direction in which the imaging unit captures an image, and a second that approximates the output of the second imaging unit to a quadratic function The approximating means further includes: the detecting means based on the first direction, the second direction, and the output of the first approximating means on the light beam on the first imaging means. The position of the corresponding light beam on the second imaging unit may be detected using the output of the second approximating unit.

  In addition, the information processing apparatus further includes an acquisition unit that acquires an output corresponding to an ambient light component, and the approximation unit acquires the output of the first imaging unit and the output of the second imaging unit by the acquisition unit. After correction based on the output corresponding to the light component, each may be approximated to a quadratic function.

  According to the three-dimensional shape measuring apparatus of the present invention, high-accuracy measurement can be performed in the three-dimensional shape measurement of the light cutting method using the two-dimensional photoelectric conversion element.

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration of a three-dimensional shape measuring apparatus 1 according to the first embodiment. As shown in FIG. 1, the three-dimensional shape measuring apparatus 1 includes a light projecting unit 2, a light projecting unit driving stage 3, a test object holder 4, and an imaging unit 5, and a control unit 6 that controls each unit. Prepare.

  The light projecting unit 2 includes a laser emitting unit 7 that emits a light beam, and a cylindrical lens 8 that shapes the light beam emitted from the laser emitting unit 7 into a slit shape. The slit-shaped light beam shaped by the cylindrical lens 8 is a light beam having a Gaussian intensity distribution in a direction perpendicular to the longitudinal direction of the slit, and is projected onto the object T to be examined.

  The light projecting unit drive stage 3 is a uniaxial stage, and drives the light projecting unit 2 in a direction (in the direction of arrow A) perpendicular to the longitudinal direction of the slit described above. Further, the test object holder 4 holds the test object T on its upper surface.

  The imaging unit 5 includes a lens (not shown) and a two-dimensional photoelectric conversion element 5a, and images a reflected image of the test object T on which the light beam is projected from a direction different from the direction in which the light beam is projected. The two-dimensional photoelectric conversion element 5a is a two-dimensional photoelectric conversion element having logarithmic characteristics in at least a partial region. That is, the imaging unit 5 is a so-called logarithmic camera.

  Here, characteristics of the logarithmic camera will be described. Conventionally, in a three-dimensional shape measuring apparatus using a logarithmic camera, its output is converted into linear sensitivity by linear calculation or the like for waveform processing. As shown in FIG. 2, when the output characteristic when imaged by a normal linear camera (camera having linear characteristics) is L1, the output when imaged by a logarithmic camera has logarithmic characteristics as indicated by L2. Have. When the output shown in L2 is converted into linear sensitivity (a one-dimensional graph of output and light quantity), L3 is obtained. As a result, stepwise distortion occurs in L3 converted to linear sensitivity, particularly in a high luminance region (region D1 in FIG. 2). This distortion occurs due to quantization error of A / D conversion during linear calculation.

  FIG. 3 shows an output when an image of a certain test object is actually captured. L4 in FIG. 3 shows an output when a certain test object is imaged by a linear camera, and L5 in FIG. 3 images the same test object by a logarithmic camera, and the output is converted into linear sensitivity by linear calculation or the like. Shows the output of the case. As shown in FIG. 3, in the region D2, the slope of L5 is larger than the slope of L4. That is, when the image is captured by a logarithmic camera and the output is converted into linear sensitivity by linear calculation or the like (L5), the inclination is larger than that when the image is captured by a linear camera (L4). As a result, when the image is captured by a logarithmic camera and the output is converted into linear sensitivity by linear calculation or the like, the center of gravity is shifted to the right side, which causes a problem in precision measurement.

  Therefore, in the present embodiment, in order to deal with such a problem, a three-dimensional shape measurement is performed without converting the output into linear sensitivity while using a logarithmic camera. In order to perform three-dimensional shape measurement without converting to linear sensitivity, in the present embodiment, processing for approximating the output of the imaging unit 5 that is a logarithmic camera to a quadratic function is performed.

  As described above, the slit-shaped light beam emitted from the laser emitting unit 7 and shaped by the cylindrical lens 8 is a light beam having a Gaussian shape. FIG. 4 shows an example of a light beam profile having a Gaussian shape. This light beam has the characteristics shown in the following equation.

式１において、Ａ’およびＡは係数を示し、ｘは走査方向上の位置を示し、μは最頻値（中心）を示し、σは分散を示す。

In Equation 1, A ′ and A indicate coefficients, x indicates a position in the scanning direction, μ indicates a mode value (center), and σ indicates variance.

  In the first embodiment, the amount of light F (t) when the light beam passes through a specific pixel of the two-dimensional photoelectric conversion element 5a of the imaging unit 5 is expressed by substituting x in Expression 1 with the scanning time t. It can be expressed by a formula.

式２において、ａ’およびａは係数を示し、τは最頻値（中心）を示し、ｂは分散を示す。式２に示すように、光ビームが撮像部５の２次元光電変換素子５ａの特定の画素を通過する際の光量Ｆ（ｔ）は、走査時刻ｔの２次関数となる。したがって、ガウス形状を有する光ビームと、対数特性を有する撮像部５とを組み合わせることにより、撮像部５の出力を２次関数に近似することができる。その結果、従来のように撮像部の出力を直線感度に換算することなく３次元形状測定を行うことができる。

In Equation 2, a ′ and a indicate coefficients, τ indicates a mode value (center), and b indicates variance. As shown in Expression 2, the light amount F (t) when the light beam passes through a specific pixel of the two-dimensional photoelectric conversion element 5a of the imaging unit 5 is a quadratic function of the scanning time t. Therefore, the output of the imaging unit 5 can be approximated to a quadratic function by combining the light beam having a Gaussian shape and the imaging unit 5 having logarithmic characteristics. As a result, three-dimensional shape measurement can be performed without converting the output of the imaging unit into linear sensitivity as in the conventional case.

  FIG. 5 is a flowchart showing the operation of the control unit 6 during measurement.

  In step S1, the control unit 6 acquires an output corresponding to the ambient light component. As described above, the imaging unit 5 of the three-dimensional shape measuring apparatus 1 of the first embodiment is a so-called logarithmic camera. Therefore, the influence of ambient light during measurement around the three-dimensional shape measuring apparatus 1 is large. Therefore, it is necessary to consider this ambient light.

  In general, the ambient light component is linearly added to the output of the imaging unit 5. Therefore, in order to correct the ambient light in the image captured by the image capturing unit 5 that is a logarithmic camera, it is necessary to return to the linear image and then perform the correction. However, if such correction is performed in a high luminance region (region D1 in FIG. 2), the quantization error increases, which is not appropriate.

  Therefore, in the first embodiment, an output corresponding to the ambient light component is acquired, and the image captured by the imaging unit 5 is corrected based on the acquired information.

  There are the following two methods for acquiring the output corresponding to the ambient light component. The first is a method of generating an image by temporarily turning off the light projecting unit 2 and imaging only the ambient light component by the imaging unit 5. In this image, only an output corresponding to the ambient light component appears. When this method is used, the control unit 5 turns off the light projecting unit 2 and controls the imaging unit 5 to perform imaging in step S1. The second method is a method of obtaining an image obtained by analyzing an image captured by the imaging unit 5 during normal measurement, determining and extracting a region corresponding to the ambient light component, and integrating the region. When this method is used, the control unit 5 appropriately reads an image at the time of measurement previously captured (preferably an image close in time as much as possible) in step S1, and corresponds to the ambient light component based on the image. Get the output.

  In the case of using the first method, the imaging unit 5 is appropriately controlled and limited to the linear region or the small signal region (for example, the region of FIG. 2D3) of the two-dimensional photoelectric conversion element 5a of the imaging unit 5. By obtaining the output corresponding to the ambient light component, the quantization error can be suppressed.

  In step S2, the control unit 6 starts scanning the light beam. The control unit 6 controls the light projecting unit 2 to start projecting the light beam onto the test object T, and controls the light projecting unit driving stage 3 so that the light projecting unit 2 is indicated by an arrow A in FIG. Drive in the direction of.

  In step S <b> 3, the control unit 6 controls the imaging unit 5 to start imaging of the test object T. Note that imaging by the imaging unit 5 is repeatedly performed at predetermined time intervals. At this time, if the portion of the test object T where the light beam is projected is flat, the image of the light beam generated by imaging is a straight line. Further, if the portion of the test object T where the light beam is projected has irregularities, the image of the light beam is deformed according to the position in the depth direction.

  In step S4, the control unit 6 determines whether or not the imaging in the entire predetermined range has been completed. If the control unit 6 determines that imaging in the entire range has been completed, the process proceeds to step S5.

  In step S5, the control unit 6 calculates an output corresponding to a change with time in an arbitrary pixel of the two-dimensional photoelectric conversion element 5a. L6 in FIG. 6 indicates an output of the imaging unit 5 in a certain pixel corresponding to a change with time. As indicated by L6 in FIG. 6, the output of the imaging unit 5 has characteristics very close to L7 that is a quadratic function. The characteristic of L7 corresponds to the fact that the light intensity distribution of the light beam is Gaussian as described above.

  In step S6, the control unit 6 corrects the output calculated in step S5 based on the information acquired in step S1. For example, the control unit 6 performs correction by subtracting the output corresponding to the ambient light component acquired in step S <b> 1 from the output of the imaging unit 5. By performing the correction in this way, it is possible to correct the ambient light component without returning to the linear image once, so that it is possible to prevent the correction accuracy from being lowered.

  In step S7, the control unit 6 approximates the output corrected in step S6 to a quadratic function. Since the specific method of approximation is the same as that of the known technique, the description thereof is omitted.

  In step S8, the control unit 6 obtains the peak, the center of gravity, and the like based on the output approximated to the quadratic function in step S7, and detects the passage time of the light beam as in the known technique.

  In step S9, the control unit 6 calculates the three-dimensional shape of the test object T based on the detection result in step S8 as in the known technique.

  As described above, according to the first embodiment, the image of the light beam reflected from the test object is captured by the two-dimensional photoelectric conversion element having logarithmic characteristics, and the output is approximated to a quadratic function. Based on the approximated output, the position of the light beam on the test object is detected, and the three-dimensional shape of the test object is calculated. Therefore, high-accuracy measurement can be performed in the three-dimensional shape measurement by the light cutting method using the two-dimensional photoelectric conversion element.

  In particular, according to the first embodiment, it is possible to realize high-precision measurement even for a test object such as a metal surface where diffuse reflection is originally small and measurement is unstable due to a fine surface state. it can.

  In addition, according to the first embodiment, as an output by imaging, an output accompanying a change with time is approximated to a quadratic function, and a time at which the light beam passes through a predetermined position on the object to be detected is detected. Therefore, by approximating the change in intensity with respect to time of the output of a certain pixel on the two-dimensional photoelectric conversion element to a quadratic function, measurement with high interpolation accuracy can be realized.

  Further, according to the first embodiment, an output corresponding to the ambient light component is acquired, and the output by imaging is corrected based on the output corresponding to the ambient light component, and then approximated to a quadratic function. Therefore, it is possible to cope with the influence of ambient light that is frequently generated in the logarithmic camera.

  In the first embodiment, the example in which the light projecting unit 2 is driven to change the relative position with the test object is shown. However, the light projecting unit 2 is fixed and the test object is driven to set the relative position. It is good also as a structure to change. However, in this case, it is necessary to shift an image generated by imaging in accordance with the amount of movement of the object to be examined. For this reason, there is a possibility that a characteristic difference between pixels may occur particularly in an imaging unit having a logarithmic characteristic.

  In the first embodiment, the output of the imaging unit 5 at a certain pixel is measured based on the change in output corresponding to the change with time. However, the output of the imaging unit 5 at a certain time is determined by the pixel. A configuration may be adopted in which measurement is performed based on a change in output corresponding to a change in position.

Second Embodiment
The second embodiment of the present invention will be described below with reference to the drawings. In the second embodiment, only different parts from the first embodiment will be described.

  FIG. 7 is a diagram illustrating a configuration of the three-dimensional shape measurement apparatus 51 of the second embodiment. As shown in FIG. 7, the three-dimensional shape measurement apparatus 51 includes a light projecting unit 52, a light projecting unit driving stage 53, a test object holder 54, a first image capturing unit 55, and a second image capturing unit 60. A control unit 56 that controls each unit is provided. The light projecting unit 52, the light projecting unit driving stage 53, the test object holder 54, and the control unit 56 are the same as the light projecting unit 2, the light projecting unit driving stage 3, the test object holder 4, and the control unit of the first embodiment. 6 is provided with the same configuration as that of each unit, and the description thereof is omitted.

  Similarly to the imaging unit 5 of the first embodiment, each of the first imaging unit 55 and the second imaging unit 60 includes a lens (not shown) and two-dimensional photoelectric conversion elements (55a, 60a), and projects a light beam. A reflected image of the illuminated test object T is captured. Similar to the two-dimensional photoelectric conversion element 5a of the first embodiment, the two-dimensional photoelectric conversion element 55a and the two-dimensional photoelectric conversion element 60a are two-dimensional photoelectric conversion elements having logarithmic characteristics in at least a partial region. That is, the first imaging unit 55 and the second imaging unit 60 are so-called logarithmic cameras, like the imaging unit 5 of the first embodiment. The first imaging unit 55 and the second imaging unit 60 are arranged so as to image the test object T from different directions.

  FIG. 8 is a diagram for explaining epipolar conditions. The epipolar condition is that a certain point reflected in the reference camera (two-dimensional photoelectric conversion element 55a of the first imaging unit 55) is a certain straight line on the other camera (two-dimensional photoelectric conversion element 60a of the second imaging unit 60). It is projected onto the epipolar line.

  In FIG. 8, if the point of interest on the object T to be examined is Pt (xt, yt, zt), a certain point Pa (xa, ya) reflected in the reference camera (two-dimensional photoelectric conversion element 55a of the first imaging unit 55). ) Corresponds to the point Pb (xb, yb) on the other camera (two-dimensional photoelectric conversion element 60a of the second imaging unit 60). The base line is a straight line connecting the optical center of the reference camera (first imaging unit 55) and the optical center of the other camera (second imaging unit 60). A surface composed of a straight line passing through the optical center of the reference camera (first imaging unit 55) and the point of interest Pt (xt, yt, zt) and the base line is referred to as an epipolar surface. Furthermore, a straight line where this epipolar plane and the other camera (second imaging unit 60) intersect is called an epipolar line. In FIG. 8, a certain point Pa (xa, ya) reflected in the reference camera (the two-dimensional photoelectric conversion element 55a of the first imaging unit 55) is the other camera (the two-dimensional photoelectric conversion element 60a of the second imaging unit 60). ) Is projected onto the epipolar line (point Pb (xb, yb)). Using this condition, when the peak position in the second imaging unit 60 corresponding to the peak position obtained in the first imaging unit 55 is obtained, it can be easily obtained by searching on the epipolar line.

  In the three-dimensional shape measuring apparatus 51 having the configuration described above, the control unit 56 performs the same processing as the flowchart shown in FIG. 3 of the first embodiment.

  However, in step S3, the control unit 56 controls both the first imaging unit 55 and the second imaging unit 60 to start imaging. And the 1st imaging part 55 and the 2nd imaging part 60 image the to-be-tested object T synchronously (at the same timing).

  In step S5, the control unit 56 calculates an output corresponding to a change with time using the epipolar condition for each output of the first imaging unit 55 and the second imaging unit 60. Also in step S6, the control unit 56 corrects the ambient light component for the respective outputs of the first imaging unit 55 and the second imaging unit 60. Also in step S7, the control unit 56 approximates each output of the first imaging unit 55 and the second imaging unit 60 after correction of the ambient light component to a quadratic function.

  In step S8 and step S9, the control unit 56 calculates the three-dimensional shape of the test object T by obtaining corresponding coordinates between the first imaging unit 55 and the second imaging unit 60. Specifically, the control unit 56 specifies corresponding coordinates based on the imaging timing. One light beam is projected onto the test object T at a certain time. Therefore, the light beams imaged by the first imaging unit 55 and the second imaging unit 60 at a certain time correspond to each other and comply with the epipolar condition. When this single light beam is scanned, the timing at which the output peak passes through the point of interest on the test object T is the same in the first imaging unit 55 and the second imaging unit 60. And the corresponding coordinate of the attention point on the to-be-tested object T on an epipolar line can be calculated | required as an intersection of an epipolar line and a light beam. The control unit 56 calculates the three-dimensional shape of the test object T based on the corresponding coordinates of the attention point obtained in this way, as in the known technique.

  As described above, according to the second embodiment, the first imaging unit 55 and the second imaging unit 60 are arranged so as to image the test object T from different directions. Each accompanying output is approximated to a quadratic function, and the time at which the light beam passes through a predetermined position on the object to be detected is detected using epipolar conditions based on the output after the approximation. Therefore, by using the stereo method, in addition to the effect of the first embodiment, more accurate measurement can be realized.

  Further, in the conventional technique, the intensity of the light beam picked up by the two image pickup means is different for a test object such as a metal surface where the diffuse reflection is unstable. When the three-dimensional shape measurement was performed using the obtained image pair, the uncertainty of the slit width of the light beam appeared at the maximum. However, according to the second embodiment, a high contrast can be obtained by reducing the corresponding points of the two imaging means to the scanning timing even for a test object with unstable diffuse reflection such as a metal surface. It is possible to cope with the instability of diffuse reflection.

  In each of the above-described embodiments, the light beam projected from the light projecting units (the light projecting unit 2 and the light projecting unit 52) is an example of a single slit shape, but can be discriminated. A plurality of slit shapes may be used.

  In each of the above-described embodiments, the example in which the light projecting unit 2 is driven to change the relative position with the test object has been described. However, the light projecting unit 2 is fixed and the test object is driven to perform the relative position. It is good also as a structure which changes. However, in this case, it is necessary to shift an image generated by imaging in accordance with the amount of movement of the object to be examined. For this reason, there is a possibility that a characteristic difference between pixels may occur particularly in an imaging unit having a logarithmic characteristic.

  In each of the above embodiments, the light projecting units (the light projecting unit 2 and the light projecting unit 52) themselves are driven by the light projecting unit drive stage (the light projecting unit drive stage 3 and the light projecting unit drive stage 53). However, in an application in which the measurement range is given priority over the measurement accuracy, the projection angle of the light beam may be scanned with a polygon mirror or the like. In this case, when the light beam passes through a certain pixel, the projection angle to the object to be measured may change. For this reason, in the case of a test object in which diffused light is unstable, measurement accuracy may be reduced.

It is a figure which shows the structure of the three-dimensional shape measuring apparatus 1 of 1st Embodiment. It is a figure explaining the characteristic of a logarithmic camera. It is another figure explaining the characteristic of a logarithmic camera. It is a figure which shows the example of the profile of the light beam which has a Gaussian shape. It is a flowchart which shows the operation | movement at the time of the measurement of the control part 6 of 1st Embodiment. It is a figure explaining the output corresponding to a time-dependent change. It is a figure which shows the structure of the three-dimensional shape measuring apparatus 51 of 2nd Embodiment. It is a figure explaining epipolar conditions.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1.51 ... Three-dimensional shape measuring apparatus, 2.52 ... Projection part, 3.53 ... Projection part drive stage, 4.54 ... Test object holder, 5 ... Imaging part, 5a, 55a, 60a ... Two-dimensional Photoelectric conversion element, 6 · 56, control unit, 7 · 57, laser emitting unit, 8 · 58, cylindrical lens, 55, first imaging unit, 60, second imaging unit

Claims (6)

A light projecting means for projecting a light beam having a slit shape and having a Gaussian distribution of intensity in a direction perpendicular to the longitudinal direction of the slit from the first direction with respect to the test object;
Changing means for changing a relative position between the light projecting means and the test object;
A two-dimensional photoelectric conversion element having a logarithmic characteristic for photoelectric conversion in at least a part of the region, and the image of the light beam reflected from the test object is converted from the direction different from the first direction from the two-dimensional photoelectric conversion; First imaging means for imaging with an element;
Detecting means for detecting a position of the light beam on the object based on an output of the first imaging means;
A three-dimensional shape measuring apparatus, comprising: a calculating means for calculating a three-dimensional shape of the object to be detected based on detection results by the detecting means at a plurality of different relative positions. The three-dimensional shape measuring apparatus according to claim 1,
First approximation means for approximating the output of the first imaging means to a quadratic function corresponding to the Gaussian distribution;
The detection means detects the position of the light beam based on the output approximated to the quadratic function. In the three-dimensional shape measuring apparatus according to claim 1 or 2,
The first approximating means approximates an output accompanying a change with time to a quadratic function as an output of the first imaging means,
The detection means detects a time when the light beam passes through a predetermined position on the test object. In the three-dimensional shape measuring apparatus according to any one of claims 1 to 3,
It further comprises an acquisition means for acquiring an output corresponding to the ambient light component,
The detection means detects the position of the light beam after correcting the output of the first imaging means based on an output corresponding to the ambient light component acquired by the acquisition means. Dimensional shape measuring device. The three-dimensional shape measuring apparatus according to claim 3,
A second two-dimensional photoelectric conversion element having a logarithmic characteristic for photoelectric conversion in at least a part of the region; and an image of the light beam reflected from the object to be examined is represented in the first direction and the first imaging Second imaging means for imaging by the second two-dimensional photoelectric conversion element from a second direction different from the direction in which the means images;
Second approximation means for approximating the output of the second imaging means to a quadratic function;
The detection means is the second imaging means corresponding to the light beam on the first imaging means based on the first direction, the second direction, and the output of the first approximation means. The position of the upper light beam is detected by using the output of the second approximating means. The three-dimensional shape measuring apparatus according to claim 5,
It further comprises an acquisition means for acquiring an output corresponding to the ambient light component,
The approximating means corrects the output of the first imaging means and the output of the second imaging means based on the output corresponding to the ambient light component acquired by the acquiring means, and then converts them into quadratic functions. A three-dimensional shape measuring apparatus characterized by approximating.

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