JP3112538B2 - Optical three-dimensional shape measuring method and measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical three-dimensional shape measuring method and a measuring device for irradiating an object with a light beam and measuring the shape of the object based on a spot light image from the object.

[0002]

2. Description of the Related Art As shown in FIG. 10, for example, a conventional optical three-dimensional shape measuring apparatus receives a spot light source 1 such as a He-Ne laser and a spot light image formed by light emitted from the spot light source 1. And an optical sensor 2 such as a CCD line sensor. In addition, this measuring device includes
A mirror 4 for scanning the surface of the DUT 3 with laser light and a mirror drive motor (not shown) are attached.
An optical sensor 2 converts a spot light image of the laser beam irradiated on the surface to an optical sensor 2
A lens system 5 for imaging is provided on the upper side. And
The laser light is scanned by the mirror 4, polar coordinates of the surface of the object 3 are obtained from the position of the spot light image of the optical sensor 2 and the angle of the mirror 4, and the coordinates are converted into orthogonal coordinates to measure irregularities on the surface. I have.

Further, as disclosed in Japanese Patent Application Laid-Open No. 223809/1990, a slit light irradiating means for irradiating a slit light to an object to be measured, and an imaging device for imaging the slit light irradiated to the object to be measured are disclosed. Is proposed in which image data obtained by the slit light is taken in while rotating around the object to be measured, and the three-dimensional shape of the object to be measured is calculated based on the data.

[0004]

The former of the above-mentioned prior arts includes a shift of the optical axis of the laser beam, a shift of the mounting surface and the rotation axis of the mirror 4, a rotation angle error, a mounting error of the device, and an optical path due to the protective glass. It includes errors such as differences, and these errors must be corrected in order to accurately measure the surface of the device under test. Moreover, to correct these errors by adding a correction term to the theoretical calculation formula, the calculation formula becomes complicated,
There is a problem that it takes a long time to calculate, and it is necessary to assemble the apparatus so as to minimize errors in assembling the components of the apparatus. In addition, the calculation formula taking into account each error has many parameters of the error, the formula becomes complicated, the calculation time is not practical, and a correction correspondence table of the correction amount for each error may be created. There is a problem that a large storage capacity is required.

In the latter case of the above-mentioned prior art, a two-dimensional image pickup device for picking up the slit light is required, the program for processing the picked-up data and the amount of information are large, and the structure of the whole system is also complicated. And expensive.
There is a problem that the calculation processing time is long.

The present invention has been made in view of the above-mentioned problems of the prior art, and makes it possible to easily mount an optical member or other device members, correct an installation error, and perform accurate measurement. It is an object of the present invention to provide an optical three-dimensional shape measuring method and a measuring device that require a small storage capacity and can perform quick calculations.

[0007]

According to the present invention, a spot light emitted from a spot light source is scanned on a surface of an object to be measured by a mirror, and the spot light on the surface of the object is detected by an optical sensor . Optical tertiary measurement of surface profile
Original shape measurement method, reference measurement object with known measurement dimensions
The surface of the object with a spotlight using a polygon mirror
The spot light image from the reference measurement object is
The surface of the object to be measured is detected by optical sensors
Predetermined correction for the correction term in the surface shape calculation formula for calculating the shape
And the correction calculation value of each term in the above surface shape calculation formula is given.
Calculates the pixel on the optical sensor by the spot light
The light receiving position data obtained from the spot light image
Based on the known surface data of the reference sample,
The optical sensor for the spot light image derived from the shape calculation formula
The difference between the above light receiving position data and
Calculate for the mirror surface and repeat this to find the difference
Perform a loop process to find the correction calculation value to be small,
Each of the above corrections corresponding to each parameter in the surface shape calculation formula
The calculated value is used as a shape calculation table for the above polygon mirror.
It is created and stored for each mirror surface, and the unknown
At the time of measurement, the correction calculation value based on the shape calculation table
This is an optical three-dimensional shape measurement method for calculating the surface shape of an unknown DUT by entering the surface shape calculation formula . The above loop
The processing is performed on the spot light image obtained by scanning the reference measurement object.
Receiving position data on the optical sensor and knowing the reference measurement object
Spot light derived from theoretical formula based on surface data
The difference between the image and the light receiving position data on the light sensor is
Calculated for all mirror surfaces of the
Calculate the correction value that minimizes the sum on all mirror surfaces.
It is a loop processing.

The shape calculation table corrects a scalar amount of surface position data of the object with respect to light receiving position data of the optical sensor and a vector amount of surface position data of the object with respect to a rotation angle of the polygon mirror. Is created based on the corrected calculation value with
The theoretical light receiving position data of the reference object is calculated based on the correction calculation value, and the sum of absolute values of the differences between the light receiving position data obtained by the measurement and the theoretical light receiving position data is minimized. A correction calculation value is created for each mirror surface of the polygon mirror as a shape calculation table corresponding to the light receiving position data value and the rotation angle of the polygon mirror, and stored. The sum of the absolute values of the differences calculated on the basis is within a predetermined range
This is an optical three-dimensional shape measurement method for creating the shape calculation table as described above .

Further, according to the present invention, a spot light is formed on an object to be measured.
It has a lens system for irradiating
Polygon mirror and mirror for scanning pot light over the object to be measured
-Provide an optical scanning device consisting of a drive motor and
Spot light image from the surface of the DUT by the reflected spot light
Sensor in which a number of pixels that receive light are arranged in a line
The reference measurement object whose measurement dimensions are known by the spot light
Scan the surface of the spot light image from the reference measurement object
Detected by an optical sensor and measured by measuring the spot light image
The light receiving position data on the optical sensor and the known
On the spot light image theoretically obtained based on the surface data
The difference between the light receiving position data on the light recording sensor and the polygon
Light receiving position data calculating means for calculating each surface of the mirror
And appropriate corrections to the correction terms in the surface shape calculation formula for the DUT
Calculate the correction calculation value of each term in the surface shape calculation formula by giving the amount
Correction calculation value calculating means, and each of the
The correction calculation value calculating means corresponds to the parameter value.
Correction calculation that minimizes the above difference from the obtained correction calculation value
A loop operation processing means for obtaining a value;
The calculated correction value corresponding to the specified parameter
The shape calculation table created and stored for each mirror surface of the Gon mirror
And an optical three-dimensional shape measuring device provided with a cable.

[0010] Further , the above-mentioned loop operation means is provided for each parameter.
Obtained by the above-mentioned correction calculation value calculating means corresponding to the value of the
Of the reference measurement object by the spot light
The light receiving position data on the optical sensor and the
Theoretically based on the known surface data of the reference
Light receiving position data on the optical sensor of the spot light image
Correction to minimize the sum of all mirror surfaces of the absolute value of the difference
Optical three-dimensional which is a loop operation processing means for calculating the calculated value
It is a shape measuring device.

Further, the laser light source is provided on the spot-like light source, a plurality of the optical sensor at a predetermined position with respect to the optical axis to the object to be measured from the laser light source of the spotlight,
Each of the optical sensors is irradiated with the incident light of the spot light image so that the light receiving area of each of the optical sensors is located on the image plane of the spot light image at each position on the surface of the object to be measured scanned by the laser light. It is attached at a predetermined angle to the axis, and the shape calculation table is provided for each of the optical sensors. Further, the optical scanning device has an encoder for detecting a rotation angle of the polygon mirror, and an encoder correction means for correcting the data of the polygon mirror rotation angle by the encoder is provided to minimize the sum of the absolute values of the differences. Correction
The shape calculation table created based on the output values
First shape calculation that stores correction calculation values for placement data
Common to the table and each surface of the polygon mirror
Stores the correction value used for the mirror surface angle used
And a second shape calculation table.

[0012]

The optical three-dimensional shape measuring method and the measuring device according to the present invention receive a spot light illuminated on an object to be measured by an optical sensor from the light receiving position on the optical sensor to the object to be measured by the principle of triangulation. Is calculated, and the three-dimensional shape of the surface of the measured object is calculated from the calculated distance. At this time, a difference between the theoretical value and the measured value of the light receiving position data is calculated for each surface of the polygon mirror, and an optimum correction term, for example, a correction term that minimizes the sum of absolute values of the difference is calculated. In addition to the surface shape calculation formula, a correction calculation value of each term of the surface shape calculation formula in consideration of the correction term is created and stored as a shape calculation table corresponding to each value of a specific parameter, and a numerical value based on the shape calculation table is used. The calculation of the surface shape of an unknown object is performed based on the above, so that the calculation speed is increased and the storage capacity for processing is reduced.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. The optical three-dimensional shape measuring apparatus of this embodiment is, as shown in FIGS. 1 to 3, arranged symmetrically with the spot light source 10 of the He-Ne laser and the optical axis of the light emitted from the spot light source 10. A pair of optical sensors 12 and 14
The measuring head 16 is provided. Optical sensors 12, 14
Is, for example, a CCD line sensor using an element of about 1000 pixels. In the measuring head 16, there is further provided a polygon mirror 20 for scanning the surface of the object 18 such as a cylinder head of the engine with a laser beam. The polygon mirror 20 has a mirror for rotating the polygon mirror 20 at a predetermined rotation speed. A drive motor 22 and a rotary encoder 24 for detecting a rotation angle of the polygon mirror 20 are attached.
Further, a lens system 2 for forming a spot light image of the laser beam irradiated on the surface of the object 18 on the optical sensors 12 and 14.
6 and 28 are provided in the measuring head 16.

The optical sensors 12 and 14 include lens systems 26 and 2
8, the optical sensor 12, the optical sensor 12, the image forming surface of the spot light at each position on the surface of the DUT 18 scanned by the laser light.
It is attached at an angle of about 42 to 43 degrees with respect to the optical axis of the incident light of the spotlight so that almost all 14 light receiving areas are located. On the surface of the measuring head 16 facing the object to be measured, a protective glass 25 for protecting the internal optical system is provided.

As shown in FIG. 2, the control device of this embodiment includes a sensor driving device 30 for driving the optical sensors 12 and 14.
And the output values of the optical sensors 12 and 14 are input and the optical sensor 1
And an imaging position extracting device 32 for extracting the center value of the spot light image on each of the light receiving positions 2 and 14 as light receiving position data. A CPU 38 that controls the sensor driving device 30 and receives the output of the imaging position extracting device 32 and the like is provided via an A / D converter (not shown) and other interface circuits. Also, the CPU 38 controls a mirror driving motor 22 and a head moving motor 34 that moves the measuring head 16, and a data processing CPU 38 that takes in data from the linear encoder 36 and data from the rotary encoder 24 that detects the position of the measuring head 16. Have. The CPU 38 further includes an RA for storing data during measurement.
M40, a hard disk 42 storing various calculation programs and a shape calculation table are connected. In addition, the CPU 44 for controlling volume calculation and peripheral devices, etc.
The CPU 44 is connected to an external storage device 46 such as a hard disk or a floppy disk and a CRT.
And an output device 48 such as a printer.

Next, a measuring method using the optical three-dimensional shape measuring apparatus of this embodiment will be described. First, the measurement principle used in this embodiment will be described with reference to FIG. This is based on the principle of the so-called triangulation method, in which a predetermined position of a reference plane of an object to be measured is set to O, and a lens system 2 is set.
The intersection of the principal plane H of 6 with the reflected light optical axis is K, the intersection of the same with the laser emission light optical axis is E, and the image forming position of the spot light at the O point on the optical sensor 12 is P. Further, the surface position of the object to be measured when the surface position of the object to be measured is closer to the optical sensor 12 by the distance λ is O1, and the image forming position on the optical sensor 12 after this movement is P1. And between OK is a
0, b0 between PK, c0 between EO, a, P1 between O1K
Let b be K, e0 be EK, and d0 be EP. Also,
Assuming that the focal length of the lens system 26 is f, the inclination of the optical sensor 12 with respect to the incident optical axis is Ω, and ∠OKO1 = α, the following equation is derived from the geometrical and optical laws.

C0 = b0 / cosθ0 (1), b0 = fa0 / (a0−f) (2) e0 = c0sinθ0 = a0tanθ0 (3) d0 = (e0²+ B0²)^1/2  = [(A0tanθ0)²+ {Fa0 / (a0-f)}²]^1/2 ... (4) Ω = cos^-1Since (b0 / d0) (5), Ω is represented by a0 from equations (2) and (4). Then, assuming that the measurement position of the DUT approaches by λ, a = λe0²+ (C0-λ)²-2e0 (c0-λ) cos (90 ° -θ0)｝^1/2 (6) b = fa / (af) (7) cosα = (a²+ A0²−λ²) / (2aa0) (8), the amount of movement of the imaging position with respect to the movement of the measurement position λ 位置
Is ξ = (b²+ B0²-2bb0cosα)^1/2 ... (9). Therefore, from equations (1), (2), (3), (6), (7), and (8),
(9) is represented by λ, a0, f, θ0, and ξ = Functio
n (λ, a0, f, θ0). Where a0, f,
θ0 is a fixed value, and only λ is a variable. Therefore,
λ is used to determine the movement amount ξ of the spot light on the optical sensor 12.
Can be calculated.

Based on the above measurement principle, the measurement principle when the polygon mirror 20 of this embodiment is used will be described with reference to FIG. Here, the output value based on the spot light image received by the optical sensors 12 and 14 is determined by the imaging position extracting device 32.
, The central light receiving position is extracted, and the optical sensor 1
CPU3 uses the light receiving positions on the light receiving positions 2 and 14 as light receiving position data.
8, the CPU 38 calculates the front position of the measured object in the CPU 38 using a predetermined surface shape calculation formula. However, at this time, when calculating the surface shape of the object to be measured from the light receiving position data, an assembling error of the optical system, an assembling error of the polygon mirror, a displacement of each mirror surface, a protective glass 25 in the middle of the optical path of the laser beam. If the calculation is directly performed by a theoretical surface shape calculation formula that does not consider an error due to an error factor such as a shift of an optical axis due to the above, accurate shape measurement cannot be performed.

First, as shown in FIG. 6, the surface position vector R (φ, ξ) of the device under test 18 is represented by a vector equation, R (φ, ξ) = P (φ) + λ ′ (ξ) Ls ( φ) ... (10) Here, in FIG. 6, the laser beam reflection position of the polygon mirror 20 is assumed to be A, and further, an arbitrary point B on the extension line thereof is considered, and the deviation AB of the optical path of the protective glass 25 and the optical path length difference are ignored. A point C where = AC is set on the optical path of the reflected laser light, and this point C is set as a reference point of the laser light irradiation position of the DUT 18. And B
The vector between C is S (φ), the unit vector which is the normal vector of the mirror surface of the polygon mirror 20 and indicates the rotation angle ω is N (ω), and the vector from the origin O ′ of the mirror coordinate system to the point B is R0. Let T be the vector from the origin O of the measurement coordinate system to the origin O 'of the mirror coordinate system. Further, P (φ) is a vector from the measurement coordinate system O of the reference point C of the irradiation position of the laser light deflected by the polygon mirror 20, L0 is a unit vector indicating the incident laser light, and Ls (φ) is the polygon mirror 20. Λ ′ (示 す) is a unit vector indicating the direction of the laser beam deflected by the equation, and a scalar quantity indicating the surface position of the DUT 18 derived from the inverse function of the above equation (9). further,
φ is the mirror angle of each mirror of the polygon mirror 20 at the time of laser reflection, and corresponds to the rotation angle ω of the polygon mirror 20. When the number of mirror surfaces is 12, φ = 2 (ω− (7/4))
π). ξ is the light receiving position data extracted from the optical sensors 12 and 14 and entered into the above equation (9). Further, P (φ) and Ls (φ) in Expression (10) are represented by the following vector expressions as shown in FIG. Ls (φ) = 2 | −L0 | cosτN (ω) + L0, and | −L0 | cosτ is represented by the inner product of the unit vectors L0, N (ω), so that Ls (φ) = 2 (−L0, N (ω)) N (ω) + L0 (11) Further, from FIG. 6, the vector P (φ) is P (φ) = T + R0 + S (φ). Since ΔABC is an isosceles triangle, BC = 2DB = 2
(DE + BE) and the center O ′ of the polygon mirror 20
Using the vertical distance h from the mirror surface to the mirror surface, DE = h,
Since BE is represented by the inner product of R0 and -N (ω), the vector S (φ) becomes S (φ) = 2 ｛h− (R0, N (ω))｝ N (ω), and P (φ ) = T + R0 + 2 ｛h- (R0, N (ω))｝ N (ω) (12) Therefore, the vector equation (10) is expressed as follows: R (φ, ξ) = T + R0 + 2 ｛h− (R0, N (ω))｝ N (ω) + λ ′ (ξ) ｛2 (−L0, N (ω)) N (ω) + L0｝ (13) Here, when the number of mirror surfaces is 12, as described above, when ω is represented by φ, ω = 7 / 4π + φ / 2, and
Since the values other than N (ω) and λ ′ (ξ) are constant vectors or constants, the surface position of the DUT 18 can be specified from ω and ξ.

However, even if the surface position of the DUT 18 is directly calculated from the above ξ according to the equation (13), errors are introduced into each vector and λ 'due to various error factors as described above, and the accurate shape is obtained. Is not calculated, and a correction term is required in equation (13). Therefore, in this embodiment, a correction calculation value in which a correction term is taken into consideration in advance in the calculation value of each term of the above equation (13) is obtained, and the correction calculation value for each value in the measurement range of the parameters ξ and φ is calculated. A shape calculation table is created and stored. The creation of the shape calculation table will be described below with reference to the flowchart of FIG.

First, components such as the optical sensors 12 and 14, the polygon mirror 20, and the lens systems 26 and 28 are assembled to the measuring head 16. Then, as shown in FIG. 7, the surface of the reference measurement object 50 whose shape and dimensions are known is scanned, and light receiving position data ξ (measured value) at each surface position is obtained. Also, from the dimensions of the known reference measurement object 50, ξ (theoretical value) that is obtained from a theoretical calculation formula based on the equation (13) that does not consider the above-described error is obtained, and the ξ (measured value) and ξ ( The absolute value of the difference from the theoretical value), here the square of the difference, is calculated for all the mirror surfaces of the polygon mirror 20 with respect to all the reference surfaces of the reference measurement object 50, and the sum thereof is obtained. That is, the sum of the squares of the difference χ
² is represented as χ ² = Σ (ξ (theoretical value) −ξ (measured value)) ² (14). Then, a correction is applied to the equation for obtaining the above ξ (theoretical value), that is, the parameter values of the terms of the equations (9) and (13) so as to minimize the χ2 by the least square method. This correction occurs at the time of assembling and adjusting the factor of the difference of ξ (measured value) from ξ (theoretical value). (1) Deviation due to position, thickness, refractive index of protective glass 25, (2) Laser (3) deviation of the laser beam deflected by the polygon mirror 20 with respect to a predetermined reference angle, that is, deviation of the offset value of the rotary encoder, (4) laser between the mirror surfaces of the polygon mirror 20 (5) deviation of the optical system parameters (a, b, Ω); and (6) deviation of the mirror coordinate system of the polygon mirror from the measurement coordinate system. This is to correct the deviation. In this embodiment, the amount of correction of these deviations is considered as a correction term to be added to the above equation (13).
The correction calculation value calculated in consideration of this correction term is sequentially substituted for each term of Expression (13) into an expression for calculating ξ (theoretical value) of Expression (14), and a loop operation process is performed to minimize χ2. Do,
Each correction calculation value for minimizing χ2 is stored.

[0022] chi ² When the above correction calculation value is obtained that minimizes, among the shift of the above (3), the value of the correction term for shift in (4), for each mirror surface of the polygon mirror 20, It is stored as a correction data table. For other deviations, the correction calculation value of λ ′ (ξ) with respect to the light receiving position data ξ in Expression (10) is stored as a shape calculation table (ξ) within the measurement range. The λ ′ shape calculation table (λ ′) stores the correction calculation value of λ ′ corresponding to the optical sensor in units of 100 pixels, and calculates the value of λ ′ between 100 pixels by interpolation using a calculation formula. . Further, with respect to the parameter φ, which is the deflection angle of the laser beam, the correction calculation value is stored as a calculation table (φ) within each measurement range of φ. Here, since the deflection angle φ is calculated from the rotation angle ω of the polygon mirror 20, in this embodiment, the measurement range for one scan is set from −30 degrees to +30 degrees.
The corresponding correction calculation value is stored as a shape calculation table (φ) by setting φ at every 5 degrees. Then, within the range of 5 degrees, a corresponding correction calculation value is output by interpolation using a calculation formula. Therefore, for example, when the detection is performed at 240 points, the scanning angle is divided into 240 from the scanning angle of −30 degrees to +30 degrees, and the measured value is calculated by the correction calculation value or the interpolation calculation based on the shape calculation table (φ) in increments of 5 degrees. Is calculated. The φ shape calculation table is shared for each mirror surface of the polygon mirror. Therefore, errors that occur for each mirror surface such as errors due to deflection of each mirror surface of the polygon mirror 20 are corrected for ξ and φ so that the overall error is minimum and within a certain range through all mirror surfaces. Is performed within a predetermined range of each parameter.

[0023] After this addition, the chi ^2, it is determined whether or not within the predetermined range, if is within a predetermined range,
It can be said that measurement data can also be obtained with desired accuracy. Further, it can be said that if the chi ² exceeds a predetermined range, poor assembling accuracy of the optical system or the like can not be completely corrected computationally a mounting error or the like of the components, it is necessary to re-adjust.

When the creation of the shape calculation table is completed as described above, the measurement calculation of the object to be measured is performed based on the table. The scanning of the surface of the DUT 18 by the laser light is performed by one scan of the DUT 18 by one mirror surface of the polygon mirror 20, and the one scan causes the optical sensors 12 and 14 to have a predetermined trigger timing, for example. The position data of 240 points is taken in. The captured data is temporarily stored in the RAM 40. Then, the measuring head 16
Is moved intermittently or by a small distance at a low speed by the head moving motor 34, scans the object 18 on the mirror surface next to the polygon mirror 20, and outputs the surface position data on the object 18 as described above. And store it. After the acquisition and storage of the surface position data for a predetermined range or the entirety of the DUT 18, the above-described processing for calculating the three-dimensional coordinates is performed. By the above scanning and processing, the surface shape of the object to be measured is calculated, and from this surface shape, for example, in the case of the cylinder head of the above embodiment, the volume of the cylinder head is calculated.

As shown in FIG. 8, the cylinder head volume is calculated by integrating the cross-sectional area of the concave portion on the surface of the cylinder head with reference to the machined predetermined pickup surface 54 of the workpiece 18 as the cylinder head. And calculate its volume. The pickup surface 54 is provided around each cylinder. At that time, at the time of measurement in a state where the plug and the valve are not attached, a volume when the plug and the valve are attached is obtained by calculation assuming a virtual plug and valve. Also,
X of the reference plane of the object to be measured is based on the reference shape of the surface of the object to be measured.
The position and rotation in the YZ axis directions are detected.

When the volume is to be obtained in a state where the surface of the cylinder head is unprocessed, as shown in FIG. 9, a reference object 56 is attached to the surface of the cylinder block, and a reference measurement section 58 on the surface is irradiated with a laser beam. Scan, check the position,
The cylinder head volume is calculated using a fixed position from a predetermined surface of the reference measurement object 56 as a virtual reference surface for volume calculation. Further, based on the surface shape of the reference measurement unit 58, the position and rotation of the reference surface of the measured object in the XYZ-axis directions are detected.

As described above, according to the optical three-dimensional shape measuring method and measuring apparatus of this embodiment, the surface shape of the object to be measured can be quickly measured without contact. In particular,
A correction calculation value in consideration of a predetermined correction amount is set in advance so as to minimize an error of the light receiving position data of the optical sensor with respect to a mounting error of the measuring device, and stored as a shape calculation table. Complicated calculations are not required, and an optimal correction can be performed with a small amount of data while comprehensively considering all errors. In addition, accurate shape measurement can be performed with a relatively simple calculation program, and the storage capacity for the shape calculation table includes correction data corresponding to each pixel of the optical sensors 12 and 14 and mirror data of a predetermined number of measurement points. Only the angle correction data may be used, and relatively few correction data may be used. Also, since the volume calculation of the cylinder head is performed based on the reference surface around the cylinder or the reference measurement object attached to the object to be measured, it can be quickly and accurately obtained.

It should be noted that the optical three-dimensional shape measuring method and measuring apparatus of the present invention are not limited to the above embodiment.
The absolute value of the difference between the light receiving position data on the actual measurement on the optical sensor and the light receiving position data on the optical sensor of the spot light image derived from the theoretical formula based on the known surface data of the reference measurement object In addition to calculating the correction calculation value that minimizes the sum of all mirror surfaces, the relationship between the theoretical light receiving position data and the measured light receiving position data may be represented by a predetermined correction coefficient, The created shape calculation table may be any table as long as a desired correction term appropriately set is taken into consideration. The loop processing may be any method other than the method using the least squares method, as long as it is a loop operation method for appropriately obtaining a desired value. Further, as the optical sensor, a photoelectric conversion element such as another semiconductor line sensor or a two-dimensional image optical sensor may be used in addition to the CCD line sensor, or a single optical sensor may be used.

[0029]

According to the optical three-dimensional shape measuring method and measuring apparatus of the present invention, the difference between the theoretical value of the light receiving position data obtained from the optical sensor and the actual measured value is calculated for each mirror surface of the polygon mirror. A correction calculation value that comprehensively considers the error of the device, for example, a correction calculation value that minimizes the sum of the absolute values of the differences is obtained, and a correction term is added to the surface shape calculation formula, and the value of each parameter is added. Since the shape calculation table based on the correction calculation values is created in correspondence with the correction values, all the errors are comprehensively canceled and the corrected measurement values are obtained in the surface shape calculation, and the calculation is based on the numerical values of the data table. It can be performed with a simple calculation formula, and can be processed at extremely high speed. In particular, an optical system using a polygon mirror has many errors related to the polygon mirror,
An error can be reliably removed by this shape calculation table. Also, when determining the volume of the unevenness of the measured object,
Since the volume is calculated based on the reference surface of the surface of the measured object, the volume can be easily and quickly calculated.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a main part of an optical three-dimensional shape measuring apparatus according to one embodiment of the present invention.

FIG. 2 is a block diagram of a control device of the optical three-dimensional shape measuring apparatus according to the embodiment.

FIG. 3 is a perspective view showing a use state of the optical three-dimensional shape measuring apparatus of the embodiment.

FIG. 4 is an explanatory diagram showing a measurement principle of the optical three-dimensional shape measuring apparatus of the embodiment.

FIG. 5 is a flowchart illustrating a correction method of the optical three-dimensional shape measuring apparatus according to the embodiment.

FIG. 6 is an explanatory diagram showing a measurement principle of the optical three-dimensional shape measuring apparatus of the embodiment.

FIG. 7 is a front view of a reference object of the optical three-dimensional shape measuring apparatus according to the embodiment.

FIG. 8 is a plan view of an object to be measured by the optical three-dimensional shape measuring apparatus according to the embodiment.

FIG. 9 is a perspective view showing a state where a reference measurement object for volume calculation of the optical three-dimensional shape measuring apparatus of this embodiment is attached to an object to be measured.

FIG. 10 is a perspective view showing a main part of a conventional optical three-dimensional shape measuring apparatus.

[Explanation of symbols]

 Reference Signs List 10 spot light source 12, 14 optical sensor 16 measuring head 18 DUT 20 polygon mirror 24 rotary encoder 25 protective glass 26, 28 lens system 30 sensor driving device 34 head moving motor 36 linear encoder 38, 44 CPU 42 hard disk 46 external storage apparatus

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-269206 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 11/00-11/30

Claims (7)

(57) [Claims] 1. An optical system for scanning a spot light emitted from a spot light source on a surface of an object to be measured by a mirror and detecting the spot light on the surface of the object to be measured by an optical sensor to measure the surface shape of the object to be measured. In the three-dimensional shape measurement method, the surface of a reference measurement object having a known measurement dimension is scanned with a spot light using a polygon mirror, and a spot light image from the reference measurement object is converted into light in which a number of pixels are arranged in a line. Surface shape calculation that detects with the sensor and calculates the surface shape of the measured object
The above-described surface shape calculation is performed by giving a predetermined correction amount to the correction term in the equation.
The correction calculation value of each term in the equation is calculated, and the
Obtained by the spot light image on the pixel of the light sensor .
A light receiving position data, the difference between the light receiving position data on the optical sensor of the spot light image derived from the surface shape calculation formula based on a known surface data of the reference measurement object, each of the polygon mirror Calculate for the mirror surface,
This is repeated to perform a loop process for obtaining a correction calculation value that minimizes the difference, and that each correction calculation value corresponding to each parameter in the surface shape calculation formula is used as a shape calculation table for each mirror surface of the polygon mirror. And store this, and when calculating the unknown object to be measured, enter the correction calculation value by the shape calculation table in the surface shape calculation formula.
An optical three-dimensional shape measuring method, wherein a surface shape of an unknown object is calculated. 2. The loop processing according to claim 1, wherein the spot light is derived from a theoretical formula based on light receiving position data of the spot light image obtained by scanning the reference measurement object on the optical sensor and known surface data of the reference measurement object. This is a loop process in which the difference between the image and the light receiving position data on the optical sensor is calculated for all the mirror surfaces of the polygon mirror, and a correction calculation value for minimizing the sum of the absolute values of the differences on all the mirror surfaces is obtained. The optical three-dimensional shape measuring method according to claim 1, wherein: 3. The shape calculation table corrects a scalar amount of surface position data of the object with respect to light receiving position data of the optical sensor and a vector amount of surface position data of the object with respect to a rotation angle of the polygon mirror. Is created based on the corrected calculated value, and the theoretical light receiving position data of the reference object is calculated based on the corrected calculated value, and the light receiving position data obtained by the measurement and the theoretical light receiving position are calculated. The correction calculation value for minimizing the sum of the absolute values of the differences from the data is created for each mirror surface of the polygon mirror as a shape calculation table corresponding to the light receiving position data value and the rotation angle of the polygon mirror. The shape calculation table is stored such that the sum of the absolute values of the differences calculated based on the shape calculation table is within a predetermined range. The optical three-dimensional shape measuring method according to claim 1, wherein the optical three-dimensional shape measuring method is performed. 4. An optical scanning device having a lens system for irradiating spot light onto an object to be measured and a spot light source, and comprising a polygon mirror for scanning the spot light on the object to be measured and a mirror driving motor. A large number of light receiving devices that receive a spot light image from the surface of the object to be measured by the scanned spot light.
An optical sensor in which pixels are arranged in a line is provided, a spot light scans the surface of a reference measurement object whose measurement dimensions are known, and a spot light image from the reference measurement object is detected by the optical sensor. The difference between the light receiving position data on the light sensor based on the image measurement and the light receiving position data on the light sensor of the spot light image that is theoretically obtained based on the known surface data of the reference measurement object, Light receiving position data calculating means for calculating each surface, and a correction calculation value for calculating a correction calculation value for each item in the surface shape calculation formula by giving an appropriate correction amount to a correction term in the surface shape calculation formula for the device under test arithmetic means, and loop processing means for obtaining the correction calculation value which minimizes the difference from the corrected calculated value obtained by the parameter values to correspond the corrected calculated value calculating means in the surface shape calculation formula This by correction calculation values obtained
Each of the polygon mirror so as to correspond to a particular parameter
An optical three-dimensional shape measuring apparatus, comprising: a shape calculation table created and stored for each mirror surface . 5. The optical sensor according to claim 1, wherein the loop calculation means includes a correction calculation value obtained by the correction calculation value calculation means corresponding to each parameter value, the light sensor being based on an actual measurement of a reference object by the spot light. Minimize the sum of all mirror surfaces of the absolute value of the difference between the light receiving position data on the optical sensor and the light receiving position data on the optical sensor of the spot light image theoretically obtained based on the known surface data of the reference measurement object. 5. The optical three-dimensional shape measuring apparatus according to claim 4, wherein said optical three-dimensional shape measuring device is a loop operation processing means for obtaining each correction calculation value. 6. A laser light source is provided for the spot light source, and a plurality of the optical sensors are provided at predetermined positions with respect to an optical axis from the laser light source of the spot light to an object to be measured, and are scanned by the laser light. the imaging plane of the spot light image at each position of the surface of the object, as the light receiving area of each light sensor is positioned a predetermined angle the respective optical sensors to the incident light optical axis of the spot light image 6. The optical three-dimensional shape measuring apparatus according to claim 4, wherein the shape calculating table is provided for each of the optical sensors . 7. The optical scanning device has an encoder for detecting a rotation angle of a polygon mirror, and an encoder correcting means for correcting data of the rotation angle of the polygon mirror by the encoder, and calculates a sum of absolute values of the difference. The shape calculation table created based on the correction calculation value to be minimized is
A first shape calculation table storing correction calculation values for the light receiving position data, and a second shape calculation table storing correction calculation values for angles of the mirror surfaces that are used in common for each surface of the polygon mirror. The optical three-dimensional shape measuring apparatus according to claim 5, wherein: