Position measurement system

• US 20070133006A1
• Filed: 06/12/2006
• Published: 06/14/2007
• Est. Priority Date: 12/13/2005
• Status: Active Grant

• Current Assignee: Fuji Xerox Company Limited (Xerox Holdings Corp.)
• Original Assignee: Fuji Xerox Company Limited (Xerox Holdings Corp.)
• Inventors: Yamaguchi, Yoshinori, Saguchi, Yasuyuki, Seko, Yasuji
• Granted Patent: US 7,583,388 B2
• Time in Patent Office: Days
• US Class Current: 356/498
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates

Abstract

A position measurement system for measuring positional coordinates of a point under measurement includes a first noise removal unit, a parameter determination unit and a second noise removal unit. The first noise removal unit removes noise from the measured positional coordinates to acquire first positional coordinate values The parameter determination unit determines a noise removal parameter on a basis of the first positional coordinate values. The second noise removal unit again removes noise from the first positional coordinate values with using the noise removal parameter, to acquire second positional coordinate values.

Claims

1. A position measurement system for measuring positional coordinates of a point under measurement, the system comprising:

a first noise removal unit that removes noise from the measured positional coordinates to acquire first positional coordinate values;

a parameter determination unit that determines a noise removal parameter on a basis of the first positional coordinate values; and

a second noise removal unit that again removes noise from the first positional coordinate values with using the noise removal parameter, to acquire second positional coordinate values.

2. The system according to claim 1, wherein:

when an amount of change obtained by comparing the first positional coordinate values with previous first positional coordinate values is smaller than a reference value, the parameter determination unit sets the noise removal parameter so as to have a broader variation range where noise is to be eliminated than a previous noise removal parameter, and

when the amount of change is greater than the reference value, the noise parameter determination unit sets the noise removal parameter so as to have a narrower variation range where noise is to be eliminated than the previous noise removal parameter.

3. The system according to claim 1, wherein:

each of the first noise removal unit and the second noise removal unit includes a Kalman filter, and

the noise removal parameter includes system noise and observation noise.

4. The system according to claim 3, wherein:

when the amount of changes obtained by comparing the first positional coordinate values with the previous first positional coordinate values is smaller than the reference value, the noise parameter determination unit sets the system noise so as to be smaller than a previous system noise and sets the observation noise so as to be larger than a previous observation noise, and

when the amount of changes is greater than the reference value, the noise parameter determination unit sets the system noise so as to be larger than the previous system noise and sets the observation noise so as to be smaller than the previous observation noise.

5. The system according to claim 1, further comprising:

an indicator that indicates a position, wherein;

the point under measurement is the position indicated by the indicator.

6. The system according to claim 5, further comprising:

a display connected to a computer, wherein;

the position indicated by the indicator is displayed as a cursor on the display.

7. The system according to claim 6, wherein the noise removal parameter is set so as to restrain vibration of the cursor accompanied by vibration of the indicator.

8. A position measurement system comprising:

an indicator that projects light of a concentric interference pattern;

a detector that detects the light of the interference pattern projected by the indicator; and

a computing device that determines positional coordinates of a center of light of an interference pattern projected onto a target object on a basis of a signal obtained from the detector, the computing device removing noise from the determined positional coordinates to compute first positional coordinate values, the computing device again removing noise from the first positional coordinate values using a noise removal parameter determined on a basis of the first positional coordinate values to compute second positional coordinate values, the computing device determining an indicated position of the indicator on a basis of the second positional coordinate values.

9. The system according to claim 8, wherein:

a Kalman filter is used for computing the first positional coordinate values and the second positional coordinate values, and

the noise removal parameter of the second noise removal unit includes system noise and observation noise.

10. The system according to claim 8, further comprising:

a display connected to the computing device, wherein the indicated position of the indicator is displayed as a cursor on the display.

11. The system according to claim 10, wherein:

when an amount of changes obtained by comparing the first positional coordinate values with previous first positional coordinate values is smaller than a reference value, the cursor is fixed; and

when the amount of changes is greater than the reference value, the cursor is moved to the second positional coordinate values.

12. A position measurement method for measuring positional coordinates of a point under measurement, the method comprising:

removing noise from the measured positional coordinates to compute first positional coordinate values;

again removing noise from the first positional coordinate values using a noise removal parameter determined on a basis of the first positional coordinate values, to compute second positional coordinate values; and

determining positional coordinates of the point under measurement on a basis of the second positional coordinate values.

13. The method according to claim 12, wherein:

when an amount of change obtained by comparing the first positional coordinate values with previous first positional coordinate values is smaller than a reference value, the noise removal parameter is set so as to have a broad variation range where noise is to be eliminated, and

when the amount of change is greater than the reference value, the noise removal parameter is set so as to have a narrow variation range where noise is to be eliminated.