Patent US5315409A successfully refreshed from Google Patents.
US5315409A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of and apparatus for obtaining binary image
Assignee: Dainippon Screen Manufacturing Co Ltd
•
Filing: 1992-02-19
•
Granted: 1994-05-24
•
Expires: 2012-02-19
Abstract
Abstract A frequency distribution or histogram M (L j-1 , L j ) of differences between gradation levels (L j-1 , L j ) of adjacent pixels (P j-1 , P j ) in an image is obtained, and the number of level-changes for each tentative threshold level L j is determined as a function of the histogram of the level differencies. By using the number of level-changes, an optimum binarization threshold level is set by means of an adaptive thresholding method. Since the number of level-changes is calculated from the histogram of the level-differencies without practical binarization for each threshold level, the amount of calculations is not dependent on the number of pixels but on the number of gradation levels. The calculations for setting the threshold level for the binarization of the image are achieved at high speeds by a small-scale hardware.
Inventors
- 👤 Akira Matsumura
- 👤 Ryuji Kitakado
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 20:41
CPC Classifications
G; G06; G06T; G06T5/00; G06T5/90; G06T5/92; G06T7/00; G06T7/10; G06T7/136; G06V; G06V10/00; G06V10/20; G06V10/28; G06T2207/00; G06T2207/30; G06T2207/30108; G06T2207/30141
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
185 words
A method of obtaining a binary image from an original image in which respective density levels of pixels are represented in the form of gradation levels, comprising the steps of: (a) obtaining pairs of gradation levels representing respective pairs of adjacent pixels in said original image; (b) counting the number of said pairs of gradation levels which are equal to one another, each count produced by said counting corresponding to a unique pair of values; (c) determining a tentative threshold level; (d) obtaining the number of pairs of adjacent pixels each of which is comprised of such two gradation levels that said tentative threshold level is included in a range defined by said two gradation levels, to obtain an index value; (e) repeating the steps (c) and (d) while updating said tentative threshold value among a plurality of tentative threshold values, to obtain a plurality of index values; (f) comparing said plurality of index values with each other to determine a threshold value; and (g) comparing said respective gradation levels of pixels in said original image with said threshold value to obtain a binarized image.
Claim 2
Independent Claim
185 words
A method of obtaining a binary image from an original image in which respective density levels of pixels are represented in the form of gradation levels, comprising the steps of: (a) obtaining pairs of gradation levels representing respective pairs of adjacent pixels in said original image; (b) counting the number of said pairs of gradation levels which are equal to one another, each count produced by said counting corresponding to a unique pair of values; (c) determining a tentative threshold level; (d) obtaining the number of pairs of adjacent pixels each of which is comprised of such two gradation levels that said tentative threshold level is included in a range defined by said two gradation levels, to obtain an index value; (e) repeating the steps (c) and (d) while updating said tentative threshold value among a plurality of tentative threshold values, to obtain a plurality of index values; (f) comparing said plurality of index values with each other to determine a threshold value; and (g) comparing said respective gradation levels of pixels in said original image with said threshold value to obtain a binarized image.
Claim 3
Dependent Claim
97 words
The method of claim 1, wherein the step (d) comprises the steps of: (d-1) selecting such a first pair of gradation levels that said tentative threshold level is included in a first range defined by said first pair of gradation levels; (d-2) selecting such a second pair of gradation levels that said tentative threshold level is included in a second range defined between said second pair of gradation levels; and (d-3) summing up first and second numbers of pairs of adjacent pixels having said first and second pair of gradation levels, respectively, to obtain said index value.
Claim 4
Dependent Claim
55 words
The method of claim 2, wherein the step (b) comprises the steps of: (b-1) preparing a memory having a plurality of storage areas which are assigned to respective pairs of gradation levels; and (b-2) storing the number of said pairs of gradation levels for each pair values in a corresponding storage area of said memory.
Claim 5
Dependent Claim
29 words
The method of claim 3, wherein the step (b-2) comprises the step of: (b-2-1) obtaining a histogram of said pairs of gradation levels in said plurality of storage areas.
Claim 6
Dependent Claim
30 words
The method of claim 4, wherein the number of said plurality of tentative threshold values are substantially equal to the total number of gradation levels for representing said original image.
Claim 7
Dependent Claim
46 words
The method of claim 5, wherein the step (f) comprises the steps of: (f-1) obtaining a minimum of said plurality of index values; and (f-2) selecting one tentative threshold value corresponding to said minimum among said plurality of tentative threshold values to determine said threshold value.
Claim 8
Dependent Claim
47 words
The apparatus of claim 5, wherein the means (f) comprises: (f-1) means for obtaining a minimum of said plurality of index values; and (f-2) means for selecting one tentative threshold value corresponding to said minimum among said plurality of tentative threshold values to determine said threshold value.
Claim 9
Independent Claim
199 words
An apparatus for obtaining a binary image from an original image in which respective density levels of pixels are represented in the form of gradation levels, comprising: (a) means for obtaining pairs of gradation levels representing respective pairs of adjacent pixels in said original image; (b) means for counting the number of said pairs of gradation levels which are equal to one another, each count produced by said counting corresponding to a unique pair of values; (c) means for providing a tentative threshold level; (d) means for obtaining the number of pairs of adjacent pixels each of which is comprised of such two gradation levels that said tentative threshold level is included in a range defined by said two gradation levels, to obtain an index value; (e) means for repeating respective operations of the means (c) and (d) while updating said tentative threshold value among a plurality of tentative threshold values, to obtain a plurality of index values; (f) means for comparing said plurality of index values with each other to determine a threshold value; and (g) means for comparing said respective gradation levels of pixels in said original image with said threshold value to obtain a binarized image.
Claim 10
Independent Claim
199 words
An apparatus for obtaining a binary image from an original image in which respective density levels of pixels are represented in the form of gradation levels, comprising: (a) means for obtaining pairs of gradation levels representing respective pairs of adjacent pixels in said original image; (b) means for counting the number of said pairs of gradation levels which are equal to one another, each count produced by said counting corresponding to a unique pair of values; (c) means for providing a tentative threshold level; (d) means for obtaining the number of pairs of adjacent pixels each of which is comprised of such two gradation levels that said tentative threshold level is included in a range defined by said two gradation levels, to obtain an index value; (e) means for repeating respective operations of the means (c) and (d) while updating said tentative threshold value among a plurality of tentative threshold values, to obtain a plurality of index values; (f) means for comparing said plurality of index values with each other to determine a threshold value; and (g) means for comparing said respective gradation levels of pixels in said original image with said threshold value to obtain a binarized image.
Claim 11
Dependent Claim
100 words
The apparatus of claim 8, wherein the means (b-2) comprises: (d-1) means for selecting such a first pair of gradation levels that said tentative threshold level is included in a first range defined by said first pair of gradation levels; (d-2) means for selecting such a second pair of gradation levels that said tentative threshold level is included in a second range defined between said second pair of gradation levels; and (d-3) means for summing up first and second numbers of pairs of adjacent pixels having said first and second pair of gradation levels, respectively, to obtain said index value.
Claim 12
Dependent Claim
54 words
The apparatus of claim 9, wherein the means (b) comprises: (b-1) memory means having a plurality of storage areas which are assigned to respective pairs of gradation levels; and (b-2) means for storing the number of said pairs of gradation levels for each pair values in a corresponding storage area of said memory means.
Claim 13
Dependent Claim
28 words
The apparatus of claim 10, wherein the means (b-2) comprises: (b-2-1) means for obtaining a histogram of said pairs of gradation levels in said plurality of storage areas.
Claim 14
Dependent Claim
30 words
The apparatus of claim 11, wherein the number of said plurality of tentative threshold values are substantially equal to the total number of gradation levels for representing said original image.
Claim 15
Independent Claim
212 words
A method of inspecting a pattern on a printed circuit board, comprising the steps of: (a) photoelectrically reading an image of said pattern to obtain an original image representing said pattern, in which representative density levels of pixels are represented in the form of gradation levels; (b) obtaining pairs of gradation levels representing respective pairs of adjacent pixels in said original image; (c) counting the number of said pairs of gradation levels which are equal to one another, each count produced by said counting corresponding to a unique pair of values; (d) determining a tentative threshold level; (e) obtaining the number of pairs of adjacent pixels each of which is comprised of such two gradation levels that said tentative threshold level is included in a range defined by said two gradation levels, to obtain an index value; (f) repeating the steps (d) and (e) while updating said tentative threshold value among a plurality of tentative threshold values, to obtain a plurality of index values; (g) comparing said plurality of index values with each other to determine a threshold value; (h) comparing said respective density levels of pixels in said original image with said threshold value to obtain a binarized image; and (i) inspecting said pattern on the basis of said binary image.
Claim 16
Independent Claim
212 words
A method of inspecting a pattern on a printed circuit board, comprising the steps of: (a) photoelectrically reading an image of said pattern to obtain an original image representing said pattern, in which representative density levels of pixels are represented in the form of gradation levels; (b) obtaining pairs of gradation levels representing respective pairs of adjacent pixels in said original image; (c) counting the number of said pairs of gradation levels which are equal to one another, each count produced by said counting corresponding to a unique pair of values; (d) determining a tentative threshold level; (e) obtaining the number of pairs of adjacent pixels each of which is comprised of such two gradation levels that said tentative threshold level is included in a range defined by said two gradation levels, to obtain an index value; (f) repeating the steps (d) and (e) while updating said tentative threshold value among a plurality of tentative threshold values, to obtain a plurality of index values; (g) comparing said plurality of index values with each other to determine a threshold value; (h) comparing said respective density levels of pixels in said original image with said threshold value to obtain a binarized image; and (i) inspecting said pattern on the basis of said binary image.
Claim 17
Independent Claim
230 words
An apparatus of inspecting a pattern on a printed circuit board, comprising: (a) means for photoelectrically reading an image of said pattern to obtain an original image representing said pattern, in which respective density levels of pixels are represented in the form of gradation levels; (b) means for obtaining pairs of gradation levels representing respective pairs of adjacent pixels in said original image; (c) means for counting the number of said pairs of gradation levels which are equal to one another, each count produced by said counting corresponding to a unique pair of values; (d) means for determining a tentative threshold level; (e) means for obtaining the number of pairs of adjacent pixels each of which is comprised of such two gradation levels that said tentative threshold level is included in a range defined by said two gradation levels, to obtain an index value; (f) means for repeating respective operations of the means (d) and (e) while updating said tentative threshold value among a plurality of tentative threshold values, to obtain a plurality of index values; (g) means for comparing said plurality of index values with each other to determine a threshold value; (h) means for comparing said respective gradation levels of pixels in said original image with said threshold value to obtain a binarized image; and (g) means for inspecting said pattern on the basis of said binary image.
Claim 18
Independent Claim
230 words
An apparatus of inspecting a pattern on a printed circuit board, comprising: (a) means for photoelectrically reading an image of said pattern to obtain an original image representing said pattern, in which respective density levels of pixels are represented in the form of gradation levels; (b) means for obtaining pairs of gradation levels representing respective pairs of adjacent pixels in said original image; (c) means for counting the number of said pairs of gradation levels which are equal to one another, each count produced by said counting corresponding to a unique pair of values; (d) means for determining a tentative threshold level; (e) means for obtaining the number of pairs of adjacent pixels each of which is comprised of such two gradation levels that said tentative threshold level is included in a range defined by said two gradation levels, to obtain an index value; (f) means for repeating respective operations of the means (d) and (e) while updating said tentative threshold value among a plurality of tentative threshold values, to obtain a plurality of index values; (g) means for comparing said plurality of index values with each other to determine a threshold value; (h) means for comparing said respective gradation levels of pixels in said original image with said threshold value to obtain a binarized image; and (g) means for inspecting said pattern on the basis of said binary image.
Claim 19
Independent Claim
213 words
A method of converting an image of a drawing on which lines are drawn into a binary image, comprising the steps of: (a) photoelectrically reading an image of said drawing to obtain an original image representing said lines, in which respective density levels of pixels are represented in the form of gradation levels; (b) obtaining pairs of gradation levels representing respective pairs of adjacent pixels in said original image; (c) counting the number of said pairs of gradation levels which are equal to one another, each count produced by said counting corresponding to a unique pair of values; (d) determining a tentative threshold level; (e) obtaining the number of pairs of adjacent pixels each of which is comprised of such two gradation levels that said tentative threshold level is included in a range defined by said two gradation levels, to obtain an index value; (f) repeating the steps (d) and (e) while updating said tentative threshold value among a plurality of tentative threshold values, to obtain a plurality of index values; (g) comparing said plurality of index values with each other to determine a threshold value; (h) comparing said respective gradation levels of pixels in said original image with said threshold value to obtain a binarized image; and (g) outputting said binary image.
Claim 20
Independent Claim
213 words
A method of converting an image of a drawing on which lines are drawn into a binary image, comprising the steps of: (a) photoelectrically reading an image of said drawing to obtain an original image representing said lines, in which respective density levels of pixels are represented in the form of gradation levels; (b) obtaining pairs of gradation levels representing respective pairs of adjacent pixels in said original image; (c) counting the number of said pairs of gradation levels which are equal to one another, each count produced by said counting corresponding to a unique pair of values; (d) determining a tentative threshold level; (e) obtaining the number of pairs of adjacent pixels each of which is comprised of such two gradation levels that said tentative threshold level is included in a range defined by said two gradation levels, to obtain an index value; (f) repeating the steps (d) and (e) while updating said tentative threshold value among a plurality of tentative threshold values, to obtain a plurality of index values; (g) comparing said plurality of index values with each other to determine a threshold value; (h) comparing said respective gradation levels of pixels in said original image with said threshold value to obtain a binarized image; and (g) outputting said binary image.
Claim 21
Independent Claim
231 words
An apparatus for converting an image of a drawing on which lines are drawn into a binary image, comprising: (a) means for photoelectrically reading an image of said drawing to obtain an original image representing said lines, in which respective density levels of pixels are represented in the form of gradation levels; (b) means for obtaining pairs of gradation levels representing respective pairs of adjacent pixels in said original image; (c) means for counting the number of said pairs of gradation levels which are equal to one another, each count produced by said counting corresponding to a unique pair of values; (d) means for determining a tentative threshold level; (e) means for obtaining the number of pairs of adjacent pixels each of which is comprised of such two gradation levels that said tentative threshold level is included in a range defined by said two gradation levels, to obtain an index value; (f) means for repeating respective operations of the means (d) and (e) while updating said tentative threshold value among a plurality of tentative threshold values, to obtain a plurality of index values; (g) means for comparing said plurality of index values with each other to determine a threshold value; (h) means for comparing said respective gradation levels of pixels in said original image with said threshold value to obtain a binarized image; and (g) means for outputting said binary image.
Claim 22
Independent Claim
231 words
An apparatus for converting an image of a drawing on which lines are drawn into a binary image, comprising: (a) means for photoelectrically reading an image of said drawing to obtain an original image representing said lines, in which respective density levels of pixels are represented in the form of gradation levels; (b) means for obtaining pairs of gradation levels representing respective pairs of adjacent pixels in said original image; (c) means for counting the number of said pairs of gradation levels which are equal to one another, each count produced by said counting corresponding to a unique pair of values; (d) means for determining a tentative threshold level; (e) means for obtaining the number of pairs of adjacent pixels each of which is comprised of such two gradation levels that said tentative threshold level is included in a range defined by said two gradation levels, to obtain an index value; (f) means for repeating respective operations of the means (d) and (e) while updating said tentative threshold value among a plurality of tentative threshold values, to obtain a plurality of index values; (g) means for comparing said plurality of index values with each other to determine a threshold value; (h) means for comparing said respective gradation levels of pixels in said original image with said threshold value to obtain a binarized image; and (g) means for outputting said binary image.
References Cited (Backward Citations)
DE3210814A1
Cited
US4491962A
Cited
US4468703A
Cited
EP0266241A1
Cited
DE3838032A1
Cited
US5075872A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1997-05-23 | 1997-11-22 | 1998-05-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-05-23 | 2001-11-22 | 2002-05-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-05-23 | 2005-11-22 | 2006-05-24 | $7700.00 | Window Closed / Lapsed |