POSITION MEASUREMENT APPARATUS AND POSITION MEASURING METHOD

• US 20110007155A1
• Filed: 06/11/2010
• Published: 01/13/2011
• Est. Priority Date: 07/07/2009
• Status: Active Grant

• Current Assignee: SMC Kabushiki Kaisha
• Original Assignee: SMC Kabushiki Kaisha
• Inventors: Aki, Tomohiko
• Granted Patent: US 9,115,983 B2
• Time in Patent Office: Days
• US Class Current: 348/142
• CPC Class Codes: G01B 11/02 for measuring length, width or thickness G01B11/08 takes precedence

Abstract

In a position measurement apparatus and a positioning measuring method, an image capturing element having an imaging region of a dimension smaller than that of a workpiece is moved relatively over a surface of the workpiece while an image on the surface of the workpiece is captured. In addition, a pattern on the surface of the workpiece is extracted from an image (I(t)) inside the imaging region, and a displacement amount of the pattern occurring in the image (I(t+1)) inside the imaging region is detected. A position on the surface of the workpiece is measured based on the detected displacement amount and the dimension.

Claims

1. A position measurement apparatus in which an image capturing element having an imaging region of a dimension smaller than that of a measurement object is moved relatively over a surface of the measurement object while an image on the surface of the measurement object is captured to obtain an image inside the imaging region, and a position on the surface of the measurement object is measured using the obtained image inside the imaging region, comprising:

an extracting unit for extracting a pattern on the surface of the measurement object from the image inside the imaging region at a predetermined point in time;

a detector for detecting a displacement amount of the pattern extracted by the extracting unit occurring in the image inside the imaging region at a point in time after the predetermined point in time; and

a measurement unit for measuring the position on the surface of the measurement object based on the dimension and the displacement amount detected by the detector.

2. The position measurement apparatus according to claim 1, further comprising:

a storage unit for storing position information concerning the pattern extracted by the extracting unit,

wherein the measurement unit measures the position on the surface of the measurement object based on the displacement amount, the dimension, and the position information stored by the storage unit.

3. The position measurement apparatus according to claim 1, wherein the extracting unit extracts a renewed pattern, which differs from the extracted pattern, from the image inside the imaging region in which the extracted pattern exists.

4. The position measurement apparatus according to claim 3, further comprising a determining unit for carrying out a determination as to whether or not the pattern extracted by the extracting unit exists in the image inside the imaging region at present time,

wherein, when it is determined by the determining unit that the pattern does not exist in the image inside the imaging region at the present time, the extracting unit extracts the renewed pattern from the image inside the imaging region at the present time.

5. The position measurement apparatus according to claim 2, wherein:

the storage unit stores a template of the pattern; and

the detector calculates the displacement amount of the pattern based on region-based matching using the template stored by the storage unit.

6. A position measuring method in which an image capturing element having an imaging region of a dimension smaller than that of a measurement object is moved relatively over a surface of the measurement object while an image on the surface of the measurement object is captured to obtain an image inside the imaging region, and a position on the surface of the measurement object is measured using the obtained image inside the imaging region, the method comprising the steps of:

extracting a pattern on the surface of the measurement object from the image inside the imaging region at a predetermined point in time;

detecting a displacement amount of the pattern extracted by an extracting unit occurring in the image inside the imaging region at a point in time after the predetermined point in time; and

measuring the position on the surface of the measurement object based on the dimension and the displacement amount detected by a detector.

7. The position measuring method according to claim 6, wherein the extracting step further comprises extracting a renewed pattern, which differs from the extracted pattern, from the image inside the imaging region in which the pattern exists.

8. The position measuring method according to claim 6, wherein, after the detecting step is performed, further comprising a determining step for determining by a determining unit whether or not the pattern extracted by the extracting unit exists in the image inside the imaging region at present time.

9. The position measuring method according to claim 6, wherein, after the extracting step is performed, further comprising a storing step for storing by a storage unit position information concerning the pattern extracted by the extracting unit.