Edge detection bias correction value calculation method, edge detection bias correction method, and edge detection bias correcting program

Patent metadata

Field	Value
Publication number	US-2016295207-A1
Application number	US-201615085027-A
Country	US
Kind code	A1
Filing date	Mar 30, 2016
Priority date	Mar 31, 2015
Publication date	Oct 6, 2016
Grant date	—

Abstract

A distance in a scanning direction between a first set of edges which face each other and exhibit an opposite change between light and dark is measured by an image measuring machine, and a bias correction value is calculated based on a difference between a measured value and a true value. Using the bias correction value, detection point correction values, which are correction values in various directions of edge detection points detected by a scan of a measured object using the image measuring machine, are calculated; a correction amount used in correction of the edge detection points is specified based on the detection point correction value in each direction; and the edge detection points are corrected using the correction amount.

First claim

What is claimed is:

1 . An edge detection bias correction value calculation method comprising:
measuring, with an image measurer, a distance in a scanning direction between a first set of edges which face each other and exhibit an opposite change between light and dark; and calculating a bias correction value based on a difference between a measured value and a true value.

2 . The edge detection bias correction value calculation method according to claim 1 , further comprising specifying, whether the bias correction value is positive or negative, by positive and negative directions determined ahead of time for changes between light and dark at edge portions.

3 . The edge detection bias correction value calculation method according to claim 1 , further comprising providing an additional set of edges in a direction orthogonal to the first set of edges, wherein the calculating the bias correction further comprises calculating the bias correction for each direction.

4 . The edge detection bias correction value calculation method according to claim 3 , further comprising:
using a calibration chart having a checkerboard pattern in which a plurality of rectangles of two tones (light and dark) are arranged so as to alternate vertically and horizontally, which corresponds to a field-of-view of image acquisition of the image measurer, scanning each of the edge portions by the image measurer, wherein for each rectangle, the distance between edges which face each other and which are included in the rectangle are each measured in each of the mutually orthogonal directions and the bias correction value in each direction is calculated.

5 . The edge detection bias correction value calculation method according to claim 1 , further comprising performing, for each optical setting of the image measurer, the measuring and the calculating.

6 . An edge detection bias correction method which executes:
calculating a detection point correction value, in which detection point correction values in each mutually orthogonal direction of edge detection points detected by a scan of a measured object using an image measurer are calculated using bias correction values obtained ahead of time by measurement using the image measurer; specifying a correction amount of the edge detection points based on the detection point correction value in each direction; and correcting the edge detection points using the correction amount.

7 . The edge detection bias correction method according to claim 6 , wherein:
the calculating the detection point correction value, using the calibration chart having a checkerboard pattern in which a plurality of rectangles of two tones (light and dark) are arranged so as to alternate vertically and horizontally, which corresponds to the field-of-view of image acquisition of the image measurer, scans each of the edge portions with the image measurer and the distance between facing edges which are included in the rectangles is respectively measured in each of the orthogonal directions, and the bias correction value in each direction is calculated ahead of time, the pre-calculated bias correction values being stored, for each of the plurality of rectangles, in a correction value table, which is referenced and the bias correction values of the at least one rectangle proximate to the edge detection point are respectively inserted for each of the directions, such that the calculating the detection point correction value is performed in each direction of the edge detection point.

8 . The edge detection bias correction method according to claim 7 , wherein:
the correction value table is prepared for each optical setting of the image measurer, and the calculating the detection point correction value references the correction value table corresponding to the optical settings when executing the edge detection bias correction.

9 . The edge detection bias correction method according to claim 6 , wherein the specifying the correction amount, in response to a scan-direction slope when detecting the edge detection point, relative to the direction of the scan during a measurement in which the bias correction values are obtained, specifies any one of the detection point correction values for each direction as the correction amount.

10 . The edge detection bias correction method according to claim 6 , wherein the specifying the correction amount, in response to the scan-direction slope when detecting the edge detection point, relative to the direction of the scan during the measurement in which the bias correction values are obtained, specifies a value calculated by proportionally distributing the detection point correction values for each direction as the correction amount.

11 . The edge detection bias correction method according to claim 6 , wherein the correcting the edge detection points corrects the edge detection points by adding or subtracting the correction amount specified in the specifying the correction amount, to the coordinates of the edge detection point, in accordance with the scan-direction slope when detecting the edge detection point, relative to the direction of the scan during the measurement in which the bias correction values are obtained.

12 . The edge detection bias correction method according to claim 11 , wherein, in the correcting the edge detection point, in a case where the coordinates of the edge detection point are designated (X, Y), the correction amount when the direction in which there is a change from dark to light at the edge portion is defined as a positive direction is designated dL, and the slope in the scan direction relative to the X axis direction while detecting the edge detection point is designated 0 , when a direction of change between light and dark at the edge portion in the scan direction while detecting the edge detection point is a direction from dark to light, corrected coordinates (T x , T y ) are found by:
T x =X+dL ·cos θ
T y =Y+dL ·sin θ

and when the direction of the change between light and dark is from light to dark:
T x =X−dL ·cos θ

T y =Y−dL ·sin θ

13 . A non-transitory computer-readable storage medium that stores a program for executing an edge detection bias correction value calculation method, the program causing the computer to execute a process comprising:
measuring, with an image measurer, a distance in a scanning direction between a first set of edges which face each other and exhibit an opposite change between light and dark; and calculating a bias correction value based on a difference between a measured value and a true value.

14 . A non-transitory computer-readable storage medium that stores a program for executing an edge detection bias correction method, the program causing the computer to execute a process comprising:
calculating a detection point correction value, in which detection point correction values in each mutually orthogonal direction of edge detection points detected by a scan of a measured object using an image measurer are calculated using bias correction values obtained ahead of time by measurement using the image measurer; specifying a correction amount of the edge detection points based on the detection point correction value in each direction; and correcting the edge detection points using the correction amount.

Assignees

• Mitutoyo Corp

Inventors

• Yoshida Hiroyuki
• Takada Akira
• Kaieda Makoto
• Cho Gyokubu
• Komatsu Koichi
• Asano Hidemitsu
• Hanamura Takashi
• Maeda Takuho
• Tokuhara Isao

Classifications

• G01B11/022

  by means of tv-camera scanning · CPC title

• G01B11/00 Primary

  Measuring arrangements characterised by the use of optical techniques · CPC title

• G06T7/13 Primary

  Edge detection · CPC title

• H04N5/142 Primary

  Edging; Contouring · CPC title

• G06T2207/30164

  Workpiece; Machine component · CPC title