JP5122729B2 - 3D shape measurement method - Google Patents

Description

  The present invention relates to a three-dimensional shape measurement method for projecting a lattice image on a three-dimensional object to be measured and measuring the shape of the object to be measured from the deformed lattice image.

  Conventionally, a moire method or a heterodyne method is known in which a lattice image is projected onto a measurement object and a three-dimensional shape is measured from the lattice image deformed according to the height distribution of each part of the measurement object. In the moire method, the height distribution is obtained by generating moire fringes that give contour lines of the height distribution of the object to be measured by superimposing a reference lattice on the deformed lattice image. In the heterodyne method, the reference grating is considered as an unmodulated spatial carrier wavelength signal, the deformation grating image is regarded as a spatially phase-modulated carrier signal, and the amount of deformation is detected as the phase to detect the height distribution of the object to be measured. Looking for.

Further, in order to measure an object to be measured having a discontinuous step, a two-dimensional lattice image in which a plurality of one-dimensional lattices having different periods and directions are superimposed is measured as described in Patent Document 1 and Patent Document 2. A two-dimensional lattice image that is projected onto an object and deformed according to the three-dimensional shape of the object to be measured is picked up. A method of obtaining a measured value of is known.
Japanese Patent Laid-Open No. 10-246612 JP 2002-318109 A

  However, in such a conventional method, when the lattice image projected on the object to be measured overlaps the contour of the object to be measured, the contour is hidden in the striped pattern of the lattice image. In the case of an image, it is hidden in black stripes, and the contour shape cannot be measured accurately. For this reason, the outline of the object to be measured must be separately measured with only white light that does not project a lattice image, and the measurement is troublesome, and the image must be taken twice, which requires a long time for measurement. In order to take an image twice, there is a problem that the measurement accuracy is lowered due to camera shake or the like during that time.

  The subject of this invention is providing the three-dimensional shape measuring method which can measure a three-dimensional shape accurately in a short time.

In order to achieve this problem, the present invention takes the following method to solve the problem. That is,
In a three-dimensional shape measurement method for projecting a lattice image from a shape measurement light source onto a three-dimensional shape measurement object and obtaining a measurement value of the three-dimensional shape of the measurement object from a lattice image captured by a shape measurement image pickup device,
The lattice image is placed on a reference plane from the shape measurement light source and projected onto a reference target whose contour three-dimensional shape is known, and the reference target is projected by a contour measurement light source having a wavelength different from that of the shape measurement light source. The reference target is imaged by the shape measurement imager that irradiates and captures the lattice image by the shape measurement light source and the contour measurement imager that captures an irradiation image by the contour measurement light source, and the reference Based on the shape of the target, the three-dimensional shape of the reference target obtained from the lattice image imaged by the shape-measuring imager, and the two-dimensional contour of the reference target obtained by the contour-measuring imager, Calibrate the positional relationship between the shape measurement imager and the contour measurement imager;
Next, with the same positional relationship among the reference plane, the shape measuring image pickup device, the contour measuring image pickup device, and the shape measuring light source , the contour measuring light source is projected simultaneously with the projection from the shape measuring light source. By irradiating the object to be measured placed on the reference plane instead of the standard target, the shape measuring image sensor and the contour measuring image sensor simultaneously image the object to be measured, and the shape Based on the three-dimensional shape of the measurement object obtained from the lattice image captured by the measurement imager and the two-dimensional contour of the measurement object obtained by the contour measurement imager, the measurement object A three-dimensional shape measuring method is characterized in that a three-dimensional contour measurement value is obtained.

  The shape measurement image pickup device and the contour measurement image pickup device may have a common optical axis and may be separated into respective wavelengths by a wavelength separation prism. The shape measurement light source and the contour measurement light source may each be irradiated from a white light source through transmission filters having different wavelengths.

  According to the three-dimensional shape measurement method of the present invention, the object to be measured is simultaneously irradiated with light sources having different wavelengths, and images are taken with imagers having different wavelengths to obtain three-dimensional contours. There is an effect that can be done.

The best mode for carrying out the present invention will be described below in detail with reference to the drawings.
As shown in FIG. 1, reference numeral 1 denotes an object to be measured placed on a reference plane P. In this embodiment, as shown in FIG. 2, the object to be measured 1 is on a rectangular base 1 a and a truncated cone 1 b. The base 1a has an inclined portion 1c. Reference numeral 2 denotes a shape measurement light source. The shape measurement light source 2 includes a white light source 4, a reflecting mirror 6, and a projection lens 8, and a shape measurement transmission filter 10 between the white light source 4 and the projection lens 8. A checkerboard 12.

  The shape measurement transmission filter 10 is a filter that transmits light of a specific wavelength out of light from the white light source 4, for example, light of a wavelength such as red or blue. A striped line is formed on the checkered strip 12 by periodic repetition, and the checkered pattern is projected onto the DUT 1 by the irradiation light that has passed through the checkered plate 12.

  A contour measuring light source 14 is provided in the vicinity of the shape measuring light source 2, and the contour measuring light source 14 includes a white light source 16, a reflecting mirror 18, and a projection lens 20, and the white light source 16 and the projection lens. 20 is provided with a transmission filter 22 for contour measurement. The contour measurement transmission filter 22 is a filter that transmits light of a specific wavelength out of light from the white light source 16, for example, light of a wavelength such as green.

  The shape measurement transmission filter 10 and the contour measurement transmission filter 22 have different wavelengths of transmitted light. For example, if the shape measurement transmission filter 10 is a filter that transmits red, the contour measurement transmission filter 22 is a filter that transmits green. Further, the shape measurement light source 2 and the contour measurement light source 14 are not limited to the case where the shape measurement transmission filter 10 and the contour measurement transmission filter 22 are used to change the wavelength of light to be irradiated. The shape measuring light source 2 may irradiate visible light and the contour measuring light source 14 may irradiate infrared light, as long as the wavelengths of the light sources 2 and 14 are different.

  Reference numeral 24 denotes a camera, in which a shape measuring image pickup device 26 and a contour measuring image pickup device 28 are integrated, and the shape measuring image pickup device 26 wavelength-separates the image of the object 1 to be measured by the imaging lens 30. An image is formed on the CCD element 34 via the prism 32. The contour measuring imager 28 forms an image of the DUT 1 on the CCD element 36 via the wavelength separation prism 32 by the imaging lens 30.

  The wavelength separation prism 32 separates light having different wavelengths, and separates light having a wavelength from the shape measuring light source 2 into a CCD element 34 and separating light having a wavelength from the contour measuring light source 14 into a CCD element 36. . In the present embodiment, the shape measurement image pickup device 26 and the contour measurement image pickup device 28 are arranged such that the optical axis 33 between the DUT 1 and the wavelength separation prism 32 is common.

  The shape measurement light source 2, the contour measurement light source 14, and the camera 24 are respectively connected to the synchronization circuit 38, and the shape measurement light source 2, the contour measurement light source 14, The camera 24 is configured to be driven simultaneously. The synchronization circuit 38 is connected to the control circuit 40, and the control circuit 40 outputs a drive signal to the synchronization circuit 38, and the three-dimensional shape and contour of the DUT 1 based on the image data input from the camera 24. Calculate the shape.

Next, the three-dimensional shape measuring method will be described with reference to the flowchart shown in FIG.
First, prior to the measurement of the three-dimensional shape of the DUT 1, it is determined whether or not the calibration of the shape measuring image sensor 26 and the contour measuring image sensor 28 is performed based on a reference target (not shown) (step 100). . If calibration has already been completed, the process proceeds to the next process without performing calibration. If the calibration is not completed, a calibration process is performed (step 110).

  In the calibration process, a standard target whose contour three-dimensional shape is known is placed on the reference plane P, and the shape measuring light source 2 is driven to project a lattice image of the checkered strip 12 onto the reference target. Then, the deformed lattice image is picked up by the shape measuring image pickup device 26 and the three-dimensional shape of the reference target is measured by the control circuit 40.

  Further, the contour measuring light source 14 is driven to irradiate the reference target, the reference target is imaged by the contour measuring imager 28, and the control circuit 40 measures the two-dimensional shape of the contour of the reference target. At the time of calibration, the shape measuring light source 2 and the contour measuring light source 14 may be driven separately, and the shape measuring image pickup device 26 and the contour measuring image pickup device 28 may be separately imaged. Alternatively, the shape measurement light source 2 and the contour measurement light source 14 may be simultaneously driven, and the shape measurement image pickup device 26 and the contour measurement image pickup device 28 may simultaneously capture images.

  The pixel position on the CCD element 34 of the shape measuring image sensor 26 is obtained from the known shape dimensions of the reference target and the deformed grid image obtained from the shape measuring image sensor 26 and the two-dimensional contour image obtained from the contour measuring image sensor 28. And the correspondence between the pixel position on the CCD element 36 of the image sensor 28 for contour measurement is calibrated. As a result, if the positional relationship among the reference plane P, the shape measurement image pickup device 26, the contour measurement image pickup device 28, and the shape measurement light source 2 is fixed, there is no need to perform calibration processing from the next time. .

  After the calibration is completed, instead of the standard target, the DUT 1 is placed on the reference plane P, a drive signal is output to the synchronization circuit 38, and the shape measurement light source 2 and contour measurement are output via the synchronization circuit 38. The light source 14 and the camera 24 are driven simultaneously (step 120). Thus, in the shape measurement light source 2, the white light source 4 emits light, and the shape measurement transmission filter 10 transmits light of a predetermined wavelength, for example, only red light. Then, the light of this wavelength passes through the grating strip 12 and a grating image is projected onto the DUT 1 by the projection lens 8.

  In the contour measurement light source 14, the white light source 16 emits light, and the contour measurement transmission filter 22 transmits light of a predetermined wavelength, for example, transmits only green light. Then, the light to be measured is irradiated onto the DUT 1 by the projection lens 20.

  On the other hand, in the camera 24, a lattice image from the shape measurement light source 2 is imaged on the CCD element 34 of the shape measurement image pickup device 26 through the imaging lens 30 and the wavelength separation prism 32, and image data corresponding to the lattice image is obtained. Is input to the control circuit 40. Further, a contour image of the object to be measured by the light from the contour measurement light source 14 is imaged on the CCD element 36 of the contour measurement image sensor 28 via the imaging lens 30 and the wavelength separation prism 32, and according to the contour image. The image data is input to the control circuit 40.

  The control circuit 40 calculates the three-dimensional shape of the DUT 1 from the image data (see FIG. 5) corresponding to the lattice image (step 130). Further, the control circuit 40 calculates the contour shape of the DUT 1 from the image data (see FIG. 6) corresponding to the contour image (step 140). This contour shape is two-dimensional data. In order to obtain the contour shape as three-dimensional data, a calibration result obtained in step 110 is used to obtain a two-dimensional data based on the three-dimensional shape calculated in step 130. The contour shape measurement value is calculated as a three-dimensional contour shape measurement value (step 150).

  That is, a three-dimensional curved surface obtained from a lattice image is cut out with a two-dimensional contour line, and an intersection of the curved surface and the contour line is recognized as a three-dimensional contour line. One point on the two-dimensional contour line from the camera 24 is a line segment from the reference point of the camera 24 to the pixel, and the contour line is a surface having a continuous line segment from the camera to the pixel. The intersection of the measured three-dimensional curved surface becomes a three-dimensional contour line.

In this way, the shape measurement light source 2 and the contour measurement light source 14 emit light simultaneously, and the shape measurement image pickup device 26 and the contour measurement image pickup device 28 simultaneously capture images. Further, the shape measurement image pickup device 26 picks up a wavelength lattice image from the shape measurement light source 2, and the contour measurement image pickup device 28 picks up a wavelength irradiation image from the contour measurement light source 14. Therefore, irradiation and imaging can be performed simultaneously, measurement can be performed in a short time, and measurement can be performed accurately without causing a measurement error due to camera shake or the like.

  The present invention is not limited to such embodiments as described above, and can be implemented in various modes without departing from the gist of the present invention.

It is a schematic block diagram of the apparatus using the three-dimensional shape measuring method of this invention. It is a perspective view of the to-be-measured object as an example of this embodiment. It is a schematic circuit diagram of the apparatus using the three-dimensional shape measuring method of this embodiment. It is a flowchart which shows an example of the shape calculation process performed with the control circuit of this embodiment. It is explanatory drawing which shows the deformation | transformation lattice image of the to-be-measured object of this embodiment. It is explanatory drawing which shows the outline image of the to-be-measured object of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Object to be measured 2 ... Shape measuring light source 4, 16 ... White light source 6, 18 ... Reflector 8, 20 ... Projection lens 10 ... Shape measuring transmission filter 12 ... Plaid plate 14 ... Contour measuring light source 22 ... Contour measurement Transmission filter 24 ... Camera 26 ... Image sensor 28 for shape measurement ... Image sensor 30 for contour measurement ... Imaging lens 32 ... Wavelength separation prism 33 ... Optical axis 34, 36 ... CCD element 38 ... Synchronous circuit 40 ... Control circuit

Claims (3)

In a three-dimensional shape measurement method for projecting a lattice image from a shape measurement light source onto a three-dimensional shape measurement object and obtaining a measurement value of the three-dimensional shape of the measurement object from a lattice image captured by a shape measurement image pickup device,
The lattice image is placed on a reference plane from the shape measurement light source and projected onto a reference target whose contour three-dimensional shape is known, and the reference target is projected by a contour measurement light source having a wavelength different from that of the shape measurement light source. The reference target is imaged by the shape measurement imager that irradiates and captures the lattice image by the shape measurement light source and the contour measurement imager that captures an irradiation image by the contour measurement light source, and the reference Based on the shape of the target, the three-dimensional shape of the reference target obtained from the lattice image imaged by the shape-measuring imager, and the two-dimensional contour of the reference target obtained by the contour-measuring imager, Calibrate the positional relationship between the shape measurement imager and the contour measurement imager;
Next, with the same positional relationship among the reference plane, the shape measuring image pickup device, the contour measuring image pickup device, and the shape measuring light source , the contour measuring light source is projected simultaneously with the projection from the shape measuring light source. By irradiating the object to be measured placed on the reference plane instead of the standard target, the shape measuring image sensor and the contour measuring image sensor simultaneously image the object to be measured, and the shape Based on the three-dimensional shape of the measurement object obtained from the lattice image captured by the measurement imager and the two-dimensional contour of the measurement object obtained by the contour measurement imager, the measurement object A method for measuring a three-dimensional shape, comprising obtaining a measurement value of a three-dimensional contour. The three-dimensional shape measurement method according to claim 1, wherein the shape measurement image pickup device and the contour measurement image pickup device have a common optical axis and are separated into respective wavelengths by a wavelength separation prism. . 3. The three-dimensional shape measurement method according to claim 1, wherein the shape measurement light source and the contour measurement light source are each irradiated from a white light source through transmission filters having different wavelengths. 4.

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