XYZ coordinates measuring system

• US 4,961,155 A
• Filed: 09/19/1988
• Issued: 10/02/1990
• Est. Priority Date: 09/19/1987
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation)
• Original Assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation)
• Inventors: Higuchi, Kazunori, Yamamoto, Shin, Ozeki, Osamu
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Mattson, Brian M.
• Application Number:
  US07/246,131
• Time in Patent Office: 743 Days
• Field of Search: 364/559, 364/571.07, 364/474.36, 364/474.37, 356/363, 356/375, 73/865.8, 340/686
• US Class Current: 702/152
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates
• CPC Class Codes: G06T 2207/30164 Workpiece; Machine component
• CPC Class Codes: G06T 7/70 Determining position or orientation of objects or cameras camera calibration G06T7/80

Abstract

An XYZ coordinates measuring system has a slit light source for projecting a slit light beam onto the surface of a work to be measured with a predetermined angle. Furthermore a television camera takes a light line formed on the surface of the work by the slit light beam to generate an output video signal. A coordinate measuring circuit has a look-up table for previously storing the interrelationship between the horizontal and vertical imaging positions of the light line and the XYZ coordinates on the surface of the actual work. The coordinate measuring circuit is adapted to process the video signal to detect the horizontal and vertical imaging positions Ks and Ls of the light line and to output the XYZ coordinates on the surface of the work from the look-up table, depending on the detected horizontal and vertical imaging positions Ks and Ls, the XYZ coordinates on the surface of the work can thus be real-time measured along the light line.

Claims

1. An XYZ coordinates measuring system comprising:

a slit light source means for projecting a slit light beam onto a surface of a work to be measured with a predetermined angle;

television camera means for taking a light line formed on the surface of the work by said slit light beam to generate an output video signal; and

coordinate measuring circuit means for processing said video signal and for detecting horizontal and vertical imaging positions Ks and Ls of said light line, said coordinate measuring circuit means including look-up table means for previously storing an interrelationship between horizontal and vertical imaging positions of said light line and XYZ coordinates thereof on said surface of the work, thereby outputting XYZ coordinates on the surface of the work from the look-up table means, based on detected values of the horizontal and vertical imaging positions Ks and Ls,

whereby the XYZ coordinates on the surface of the work are real-time measured along the light line.

2. The XYZ coordinates measuring system as defined in claim 1 wherein said slit light source means includes a slit light source for projecting slit light beams onto the surface of the work with a predetermined angle and wherein said television camera means includes a television camera for taking a light line formed on the surface of the work by said slit light beam to generate an output video signal in synchronism with a horizontal scan and wherein said coordinate measuring circuit means comprises a threshold setting circuit for setting a threshold used to detect the light line from the video signal, a light line detecting circuit for generating at its output light line detection signals during a period for which the video signal is higher than said threshold, a horizontal address generating circuit for generating a horizontal address representative of a position of a horizontal picture element in an imaging device of said television camera, a horizontal imaging position detecting circuit for adding addresses at positive and negative edges to form and generate a horizontal imaging position value during a period for which light line detection signals are being output from said light line detecting circuit, a vertical imaging position detecting circuit for counting horizontal synchronous signals from the television camera to detect a vertical imaging position, a look-up table for previously storing the interrelationship between the horizontal and vertical imaging positions and the XYZ coordinates on the surface of the actual work, said look-up table generating at its output the XYZ coordinates on the surface of the work, based on the horizontal and vertical imaging positions detected, and a memory for storing the XYZ coordinates from said look-up table, whereby the XYZ coordinates on the surface of the work are real-time measured along the light line.

3. The XYZ coordinates measuring system as defined in claim 2 wherein said coordinate measuring circuit means includes a light line assigning circuit for selecting any one of two light line detection signals from said light line detecting circuit within a horizontal scan period when two light lines exist on one horizontal scanning line, the selected light line detection signal being then supplied to said horizontal imaging position detecting circuit.

4. The XYZ coordinates measuring system as defined in claim 2 wherein said slit light source projects at least two non-parallel slit light beams onto the surface of the work with predetermined angles and wherein there is provided a slit light selecting circuit for selecting and projecting any one of said at least two slit light beams onto the surface of the work and wherein said look-up table means includes a plurality of look-up tables corresponding in number to said slit light beams, one of said look-up tables corresponding to a selected slit light beam being selected whereby the corresponding XYZ coordinates are output on the surface of the work.

5. The XYZ coordinates measuring system as defined in claim 2 wherein said coordinate measuring circuit means comprises a light line width detecting circuit for counting clock signals from the television camera means to detect a light line width for each horizontal scan period during a period for which the light line is being detected, a maximum light line value detecting circuit for detecting a maximum value in the detected light line for each horizontal scan, a control circuit for controlling intensity of the slit light into a proper level, depending on at least one of a width and a maximum value in the light line detected for each horizontal scan.

6. The XYZ coordinates measuring system as defined in claim 2 wherein said slit light source means comprises a cross-shaped slit light source for projecting first and second slit light beams onto the work, said first and second slit light beams perpendicularly intersecting each other on a Z-axis in an orthogonal XYZ coordinate system, the first slit light beam being parallel to an XZ plane while the second slit light beam being parallel to a YZ plane, and a slit light switching circuit for performing the alternate projection of the first and second slit light beams from said cross-shaped slit light beams from said cross-shaped slit light source and wherein said television camera means includes first and second television cameras for taking light lines formed on the work by said slit light beams, the first television camera extends the vertical axis of its imaging device substantially parallel to an X-axis while the second television camera being positioned to extend the vertical axis of its imaging device substantially parallel to a Y-axis, and a television camera switching circuit for selecting the output signal of said first television camera on projection of the first slit light beams or the output signal of the second television camera on projection of the second slit light beam and wherein said coordinate measuring circuit processes the output of said television camera switching circuit to output an XZ coordinate when the first slit light beam is projected and a YZ coordinate when the second slit light beam is projected.

7. The XYZ coordinates measuring system as defined in claim 1 wherein said slit light source means includes a slit light source for projecting a slit light beam onto the surface of the work with a predetermined angle and wherein said television camera means includes a television camera for taking a light line formed on the surface of the work by said slit light beam and wherein said coordinate measuring circuit comprising an A/D converter for converting a video signal from the television camera into a digital video signal Vi in synchronism with a horizontal scan, a threshold setting circuit for setting a threshold used to detect the light line from the video signal, a light line detecting circuit for generating at its output light line detection signals during a period for which the digital video signal Vi is higher than said threshold, a horizontal address generating circuit for generating horizontal addresses representative of a position of a horizontal picture element in an imaging device of said television camera, an adder/accumulator for accumulating video signals Vi from the A/D converter during a period for which light line detection signals are being output from said light line detecting circuit, a multiplier/accumulator for accumulating a product Vi X Ki of each video signal Vi from the A/D converter and each of said horizontal addresses Ki from said horizontal address generating circuit for a period for which light line detection signals are being output from said light line detecting circuit, a horizontal imaging position detecting circuit for dividing an output Σ

Vi of said adder/accumulator to form a calculated valve Ks representative of a horizontal imaging position, a vertical imaging position detecting circuit for counting horizontal synchronous signals from the television camera to detect a vertical imaging position Ls, a look-up table for previously storing the interrelationship between the horizontal and vertical imaging positions and the XYZ coordinates on the surface of the actual work, said look-up table generating at its output the XYZ coordinates on the surface of the work, depending on the horizontal and vertical imaging positions Ks and Ls detected, and a memory for storing the XYZ coordinates from said look-up table.

8. The XYZ coordinates measuring system as defined in claim 7 wherein said coordinate measuring circuit includes a light line assigning circuit for selecting any one of two light line detection signals from said light line detecting circuit when two light lines exist on one horizontal scanning line, the selected light line detection signal being applied to said adder/accumulator and multiplier/accumulator.

9. The XYZ coordinates measuring system as defined in claim 7 wherein said coordinate measuring circuit comprises a dual-line memory for alternately storing video signals Vi for the respective horizontal scanning lines from the A/D converter, said dual-line memory providing a video signal stored in an immediately preceding horizontal scan period to said light line detecting circuit, adder/accumulator and multiplier/accumulator, a proportional threshold setting circuit for detecting a maximum value in a video signal Vi for each horizontal scan in the television camera, the maximum value being multiplied by a preset proportional coefficient to obtain a result with the result being then output as a proportional threshold, and a threshold selecting circuit for generating a proportional threshold to said light line detecting circuit when a threshold set by said proportional threshold setting circuit is higher than a usual threshold set by said threshold setting circuit and for supplying said usual threshold to said light line detecting circuit when said proportional threshold is lower than said usual threshold.

10. The XYZ coordinates measuring system as defined in claim 7 wherein said coordinate measuring circuit comprises a maximum Σ

Vi value storing circuit for storing the maximum value of Σ

Vi from said adder/accumulator and simultaneously generating a maximum value detection signal, when at least two light lines exist on one horizontal scanning line, and a Σ

ViKi storing circuit for storing the output Σ

Vi×

Ki of said multiplier/accumulator in synchronism with the maximum value detection signal from said maximum Σ

Vi value storing circuit.

11. The XYZ coordinates measuring system as defined in claim 10 wherein said coordinate measuring circuit comprises:

a light line width detecting circuit for counting clock signals from the television camera to detect a width of a light line for a period from which the light line is being detected for each horizontal scan;

a temporal storage circuit for temporally storing the light line width from said light line width detecting circuit depending on a maximum value detection signal from said maximum Vi value storing circuit;

a maximum light line value detecting circuit for detecting the maximum value of the detected light line for each horizontal scan;

a temporal storage circuit for temporally storing the maximum light line value from said maximum light line value detecting circuit depending on the maximum value detection signal from said maximum Σ

Vi value storing circuit; and

a control circuit for controlling an intensity of the slit light beam into a proper level depending on at least one of the width and maximum value detected for that light line for each horizontal scan.

12. The XYZ coordinates measuring system as defined in claim 7 wherein said slit light source means projects at least two non-parallel slit light beams onto the surface of the work with predetermined angles and wherein there is provided a slit light selecting circuit for selecting any one of said at least two slit light beams, the selected slit light beam being projected onto the surface of the work and wherein said look-up table means includes a plurality of look-up tables corresponding in number to said slit light beams, one of the look-up tables corresponding to the selected slit light beam outputting corresponding XYZ coordinates on the surface of the work.

13. The XYZ coordinates measuring system as defined in claim 7 wherein said slit light source means comprises a cross-shaped slit light source for projecting first and second slit light beams onto the work, said first and second slit light beams perpendicularly intersecting each other on a Z-axis in an orthogonal XYZ coordinate system, said first slit light beam being parallel to an XZ plane while said second slit light beam being parallel to an XZ plane, and a slit light switching circuit for performing the alternate projection of said first and second slit light beams from said cross-shaped slit light source and wherein said television camera means includes first and second television cameras for taking the light lines formed on the work by said slit light beams, said first television camera being located to extend a vertical axis of its imaging device substantially parallel to the X-axis while said second television camera extending the vertical axis of its imaging device substantially parallel to the Y-axis, and a television camera switching circuit for selecting the output signal of said first television camera when the slit light beam is projected onto the work or the output signal of said second television camera when the second slit light beam is projected onto the work and wherein said coordinate measuring circuit processes the output of said television camera switching circuit to output an XZ coordinate when the first slit light beam is projected and a YZ coordinate when the second slit light beam is projected.

14. The XYZ coordinates measuring system as defined in claim 13 wherein said coordinate measuring circuit comprises:

an A/D converter for converting a video signal from said television camera switching circuit into a digital video signal Vi in synchronism with a horizontal scan;

a threshold setting circuit for setting a threshold level used to detect the light line from the video signal;

a light line detecting circuit for outputting light line detection signals during a period for which the digital video signal Vi is higher than the threshold level;

a horizontal address generating circuit for generating a horizontal address Ki representative of a position of a horizontal picture element in the imaging device of the television camera;

an adder/accumulator for accumulating video signals Vi from the A/D converter during a period for which light line detection signals are being output from the light line detecting circuit;

a multiplier/accumulator for accumulating a product Vi×

Ki of each video signal Vi from said A/D converter and each horizontal address Ki from said horizontal address generating circuit for a period for which light line detection signals are being output from the light line detecting circuit;

a horizontal imaging position detecting circuit for dividing the output Σ

Vi×

Ki of said multiplier/accumulator by the output Σ

Vi of said adder/accumulator with the resulting value Ks being then output from said horizontal imaging position detecting circuit as a horizontal imaging position;

a vertical imaging position detecting circuit for counting horizontal synchronous signals from the television camera to detect a vertical imaging position Ls;

an XZ look-up table for previously storing the interrelationship between the values Ks, Ls and the X- and Z-axis coordinates such that when the first slit light beam is projected onto the work and if the horizontal and vertical imaging positions Ks and Ls are input into said XZ look-up table, actual X- and Z-axis coordinates on the surface of the work are output from said XZ look-up table;

a YZ look-up table for previously storing the interrelationship between the values Ks, Ls and the Y- and Z-axis coordinates such that when the second slit light beam is projected onto the work and if the horizontal and vertical imaging positions Ks and Ls are input into said YZ look-up table, actual Y- and Z-axis coordinates on the surface of the work are output from said YZ look-up table;

a coordinate table switching circuit for supplying the outputs Ks and Ls to the XZ look-up table on projection of the first slit light beam and for applying the outputs Ks and Ls to the YZ look-up table on projection of the second slit light beam; and

a memory for storing the outputs of said look-up tables.

15. The XYZ coordinates measuring system as defined in claim 14 wherein said coordinate measuring circuit includes a light line assigning circuit for selecting any one of two light line detection signals from said light line detecting circuit when two light lines exist on one horizontal scanning line, the selected light line detection signal being supplied to said adder/accumulator and multiplier/accumulator.

16. The XYZ coordinates measuring system as defined in claim 14 wherein said coordinate measuring circuit comprises a dual-line memory for alternately storing video signals Vi for the respective horizontal scanning lines from the A/D converter, said dual-line memory providing a video signal stored in an immediately preceding horizontal scan period to said light line detecting circuit, adder/accumulator and multiplier/accumulator, a proportional threshold setting circuit for detecting the maximum value in a video signal Vi for each horizontal scan in the television camera, the maximum value being multiplied by a preset proportional coefficient with the result being then output as a proportional threshold, and a threshold selecting circuit for generating a proportional threshold to said light line detecting circuit when a threshold set by said proportional threshold setting circuit is higher than a usual threshold set by said threshold setting circuit and for supplying said usual threshold to said light line detecting circuit when said proportional threshold is lower than said usual threshold.

17. The XYZ coordinates measuring system as defined in claim 14 wherein said coordinate measuring circuit comprises a maximum Σ

Vi value storing circuit for storing the maximum value of Σ

Vi from said adder/accumulator and simultaneously generating a maximum value detection signal, when at least two light lines exist on one horizontal scanning line, and a Σ

ViKi storing circuit for storing the output Σ

Vi×

Ki of said multiplier/accumulator in synchronism with the maximum value detection signal from said maximum Σ

Vi value storing circuit.

18. The XYZ coordinates measuring system as defined in claim 17 wherein said coordinate measuring circuit comprises:

a light line width detecting circuit for counting clock signals from the television camera to detect the width of a light line for a period for which the light line is being detected for each horizontal scan;

a temporal storage circuit for temporally storing the light line width from said light line width detecting circuit depending on the maximum value detection signal from said maximum Vi value storing circuit;

a maximum light line value detecting circuit for detecting the maximum value of the detected light line for each horizontal scan;

a temporal storage circuit for temporally storing the maximum light line value from said maximum light line value detecting circuit depending on the maximum value detection signal from said maximum Σ

Vi value storing circuit; and

a control circuit for controlling the intensity of the slit light beam into a predetermined level depending on at least one of the width and maximum value detected for that light line for each horizontal scan.

19. The XYZ coordinates measuring system as defined in claim 1 wherein said slit light source means comprises a cross-shaped slit light source for projecting first and second slit light beams onto the work, said first and second slit light beams perpendicularly intersecting each other on a Z-axis in an orthogonal XYZ coordinate system, said first slit light beam being parallel to the XZ plane while said second slit light beam being parallel to the YZ plane, and a slit light switching circuit for performing the alternate projection of said first and second slit light beams from said cross-shaped slit light source and wherein said television camera means includes first and second television cameras for taking the light lines formed on the work by said slit light beams, said first television camera extending the vertical axis of its imaging device substantially parallel to the X-axis while said second television camera being positioned to extend the vertical axis of its imaging device substantially parallel to the Y-axis, and a television camera switching circuit for selecting the output signal of said first television camera when the slit light beam is projected onto the work or the output signal of said second television camera when the second slit light beam is projected onto the work and wherein said coordinate measuring circuit processes the output of said television camera switching circuit to output an XZ coordinate when the first slit light beam is projected and a YZ coordinate when the second slit light beam is projected.

20. An XYZ coordinates measuring system comprising:

a slit light source means including a slit light source for projecting a slit light beam onto a surface of a work to be measured with a predetermined angle;

television camera means for taking a light line formed on the surface of the work by said slit light beam to generate an output video signal; and

coordinate measuring circuit means including;

a light line detecting circuit for outputting light line detection signals based on said video signal,

a horizontal imaging position detecting circuit for adding addresses at the positive and negative edges to generate a horizontal imaging position Ks during a period for which light line detection signals are being output from said light line detecting surface,

a vertical imaging position detecting circuit for detecting a vertical imaging position Ls based on said video signal, and

look-up table means for previously storing an interrelationhsip between horizontal and vertical imaging positions of said light line and XYZ coordinates thereof on said surface of the work, thereby outputting XYZ coordinates on the surface of the work from said look-up table means, based on detected values of the horizontal and vertical imaging positions Ks and Ls,

whereby the XYZ coordinates on the surface of the work are real-time measured along the light line.