Three-dimensional shape measuring apparatus, program, computer-readable recording medium, and three-dimensional shape measuring method
An apparatus, method, and program for measuring the three-dimensional shape of an object by analyzing an optical pattern projected onto the object includes a line sensor and an image analysis unit. The line sensor reads the target object, onto which the optical pattern is projected. The image analysis unit analyzes the optical pattern in the image read by the line sensor based on a spatial fringe analysis method, and the image analysis unit computes the three-dimensional shape information on the target object. The phase of a pixel included in an image taken of the optical pattern is determined based on the brightness values of the pixel and at least one neighboring pixel in the image; thus the height information of the object can be determined. In addition, the height of the target object at a given position can be computed based on how much the phase of the optical pattern projected onto a certain position of the object is shifted from a reference phase.
1. A three-dimensional shape measuring apparatus comprising:
a line sensor that reads an optical pattern projected onto a target object, wherein brightness of the optical pattern is periodically changed according to position and wherein the line sensor reads the optical pattern as an image; and
an image analysis unit that computes a phase of the optical pattern in a pixel included in the image read by the line sensor based on brightness values of the pixel and at least one neighboring pixel in the image, wherein the image analysis unit computes height information on the target object based on the computed phase; and
an optical pattern projection unit that projects the optical pattern onto the target object,
wherein the optical pattern projection unit projects the optical pattern onto the target object such that a pitch of a brightness change of the optical pattern becomes smallest in a main scan direction of the line sensor.
2. A three-dimensional shape measuring apparatus according to claim 1 , wherein the image analysis unit comprises a setting unit that sets a number of neighboring pixels used in computing the phase of the optical pattern.
3. A three-dimensional shape measuring apparatus comprising:
a line sensor that reads an optical pattern projected onto a target object, wherein brightness of the optical pattern is periodically changed according to position and wherein the line sensor reads the optical pattern as an image;
an image analysis unit that:
analyzes a phase of the optical pattern in the image read by the line sensor based on a spatial fringe analysis method, and
computes height information on the target object; and
an optical pattern projection unit that projects the optical pattern onto the target object,
wherein the optical pattern projection unit projects the optical pattern onto the target object such that a pitch of a brightness change of the optical pattern becomes smallest in a main scan direction of the line sensor.
4. A three-dimensional shape measuring apparatus according to claim 3 , wherein the image analysis unit comprises a setting unit that sets a size of a filter used in the spatial fringe analysis method.
5. A three-dimensional shape measuring apparatus according to claim 1 , wherein the optical pattern projection unit projects the optical pattern onto the target object such that the optical pattern has a linear shape in which the optical pattern is focused on one axis extending in the main scan direction of the line sensor.
6. A three-dimensional shape measuring apparatus according to claim 1 , wherein the line sensor reads the target objects in two states comprising a state where the optical pattern is projected and a state where the optical pattern is not projected,
wherein the image analysis unit normalizes brightness of the image read by the line sensor in the state where the optical pattern is projected onto the target object based on brightness of the image read by the line sensor in the state where the optical pattern is not projected onto the target object, and
wherein the image analysis unit analyzes the optical pattern in the image of the normalized brightness.
7. A three-dimensional shape measuring apparatus according to claim 1 , further comprising two line sensors comprising a first line sensor and a second line sensor,
wherein the first line sensor reads the target object onto which the optical pattern is projected,
wherein the second line sensor reads the target object onto which the optical pattern is not projected,
wherein the image analysis unit normalizes brightness of the image read by the first line sensor based on brightness of the image read by the second line sensor, and
the image analysis unit analyzes the optical pattern in the image of the normalized brightness.
8. A three-dimensional shape measuring apparatus according to claim 1 , further comprising a conveyance unit that conveys at least one of the line sensor and the target object at a predetermined conveyance speed in a sub-scan direction orthogonal to a main scan direction of the line sensor,
wherein the line sensor reads the optical pattern projected onto the target object while moved in the sub-scan direction with respect to the target object,
wherein the image analysis unit computes length information on the main scan direction of the target object based on a number of pixels in the main scan direction in the image, and
wherein the image analysis unit computes length information on the sub-scan direction of the target object based on the conveyance speed.
9. A three-dimensional shape measuring method comprising:
projecting an optical pattern onto a target object;
reading the optical pattern as an image;
computing a phase of the optical pattern in a pixel included in the image read by a line sensor based on brightness values of the pixel and at least one neighboring pixel in the image, and
computing height information on the target object based on the computed phase,
wherein the optical pattern is projected onto the target object such that a pitch of a brightness change of the optical pattern becomes smallest in a main scan direction of the line sensor.
10. A program stored on computer-readable recording medium for causing a computer to function as an image analysis unit of a three-dimensional shape measuring apparatus including a line sensor that reads an optical pattern projected onto a target object, the program for causing the computer to perform:
computing a phase of the optical pattern in a pixel included in the image read by the line sensor based on brightness values of the pixel and at least one neighboring pixel in the image, and
computing height information on the target object based on the computed phase,
wherein the optical pattern is projected onto the target object such that a pitch of a brightness change of the optical pattern becomes smallest in a main scan direction of the line sensor.
11. A three-dimensional shape measuring method comprising:
an optical pattern projection process of projecting an optical pattern onto a target object, wherein brightness of the optical pattern is periodically changed according to position;
an optical pattern reading process of reading the optical pattern as an image;
an image analysis process of
computing a phase of the optical pattern in a pixel included in the image read through the optical pattern reading process based on brightness values of the pixel and at least one neighboring pixel in the image, and
computing height information on the target object based on the computed phase,
wherein the optical pattern is projected onto the target object such that a pitch of a brightness change of the optical pattern becomes smallest in a main scan direction of the line sensor.
12. A three-dimensional shape measuring method according to claim 11 , wherein the image analysis process includes a setting process of setting a number of neighboring pixels used in computing the phase of the optical pattern.
13. A three-dimensional shape measuring method comprising:
an optical pattern projection process of projecting an optical pattern onto a target object, wherein brightness of the optical pattern periodically changed according to position;
an optical pattern reading process of reading the optical pattern as an image; and
an optical pattern analysis process of computing height information on the target object by analyzing an optical pattern in the image read through the optical pattern reading process based on a spatial fringe analysis method
wherein the optical pattern is projected onto the target object such that a pitch of a brightness change of the optical pattern becomes smallest in a main scan direction of the line sensor.
14. A three-dimensional shape measuring method according to claim 13 , wherein the image analysis process includes a setting process of setting a size of a filter used in the spatial fringe analysis method.
15. A three-dimensional shape measuring method according to claim 11 , wherein, in the optical pattern projection process, a pitch of a brightness change becomes smallest in a main scan direction of the optical pattern reading process.
16. A three-dimensional shape measuring method according to claim 11 , wherein, in the optical pattern projection process, the optical pattern projected onto the target object has a linear shape in which the optical pattern is focused on one axis extending in the main scan direction of the optical pattern reading process.
17. A three-dimensional shape measuring method according to claim 11 , further comprising a reference reading process of reading the target object onto which the optical pattern is not projected, as the image,
wherein, in the optical pattern analysis process, brightness of the image read through the optical pattern reading process is normalized based on brightness of the image read through the reference reading process, and the optical pattern is analyzed in the image of the normalized brightness.
18. A three-dimensional shape measuring method according to claim 11 , wherein,
in the optical pattern reading process, the optical pattern is read as the image while moving in a sub-scan direction orthogonal to the main scan direction of the optical pattern reading process at a predetermined speed with respect to the target object, and
in the image analysis process, length information on the main scan direction of the target object is computed based on a number of pixels in the main scan direction in the image, and length information on the sub-scan direction of the target object is also computed based on the predetermined speed.