WO1988003062A1 - Method and apparatus for detecting and compensating changes in product reflectance in optical scanning detection and rejection systems - Google Patents
Method and apparatus for detecting and compensating changes in product reflectance in optical scanning detection and rejection systems Download PDFInfo
- Publication number
- WO1988003062A1 WO1988003062A1 PCT/GB1987/000766 GB8700766W WO8803062A1 WO 1988003062 A1 WO1988003062 A1 WO 1988003062A1 GB 8700766 W GB8700766 W GB 8700766W WO 8803062 A1 WO8803062 A1 WO 8803062A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- circuit
- signal
- threshold
- output
- level adjustment
- Prior art date
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
- B07C—POSTAL SORTING; SORTING INDIVIDUAL ARTICLES, OR BULK MATERIAL FIT TO BE SORTED PIECE-MEAL, e.g. BY PICKING
- B07C5/00—Sorting according to a characteristic or feature of the articles or material being sorted, e.g. by control effected by devices which detect or measure such characteristic or feature; Sorting by manually actuated devices, e.g. switches
- B07C5/34—Sorting according to other particular properties
- B07C5/342—Sorting according to other particular properties according to optical properties, e.g. colour
- B07C5/3422—Sorting according to other particular properties according to optical properties, e.g. colour using video scanning devices, e.g. TV-cameras
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
- B07C—POSTAL SORTING; SORTING INDIVIDUAL ARTICLES, OR BULK MATERIAL FIT TO BE SORTED PIECE-MEAL, e.g. BY PICKING
- B07C5/00—Sorting according to a characteristic or feature of the articles or material being sorted, e.g. by control effected by devices which detect or measure such characteristic or feature; Sorting by manually actuated devices, e.g. switches
- B07C5/34—Sorting according to other particular properties
- B07C5/342—Sorting according to other particular properties according to optical properties, e.g. colour
- B07C5/3425—Sorting according to other particular properties according to optical properties, e.g. colour of granular material, e.g. ore particles, grain
Definitions
- TITLE METHOD AND APPARATUS FOR DETECTING AND
- This invention ' relates to a method and apparatus for providing continuous, automatic background compensation for a scanning optical detection system.
- any optical detection system used to reject foreign material from a . flow of product it is essential that a visual difference exists between the normal product and the foreign material to be rejected.
- the system performance is directly related to the reject system's ability to act on this difference.
- fluctuations in illumination, product colour, dust, steam, or any other obscuring gas or material will cause the normal product signal level to alter.
- some fixed tolerance would be made above the level of these fluctuations, whereby only foreign material with a difference greater than these fluctuations would be rejected.
- An object of the present invention is to provide a method and apparatus for continuous automatic detection and compensation of changes in the level of a reflected background camera signal from a product stream, due to changes in illumination, product colour or other causes, in an optical scanning detection system.
- the video signal from camera 1 is held by the valid data strobe in sample/hold device 2 the output of the sample/hold is compared with the output of an averaging circuit (e.g. running average over a period of 1.5 minutes) 4 to produce an error signal at the output of amplifier 3- This error signal is used to modify the current value of the averaging circuit.
- an averaging circuit e.g. running average over a period of 1.5 minutes
- a signal from a manual threshold level adjustment device 7 is summed together with the output of the averaging circuit 4, in a threshold summing circuit 5.
- the resultant output is compared with the video signal in a reject pulse comparator 6. If the video signal is greater than the summed threshold signal a reject data pulse will be output from comparator 6. In this manner there is achieved:
- reject data pulse may be fed to a zone decoder logic circuit of an apparatus for providing programmable size and overlap in a detection system as described in our co-pending application no. 8625953 filed simultaneously with the present application.
Landscapes
- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Image Input (AREA)
Abstract
An apparatus for providing continuous, automatic background compensation in a scanning optical detection system includes a video camera (1), a signal sampling means (2) controlled by a valid data strobe and comparator means (6) for comparing the signals from the sampling means and the video signal reference. The system is provided with an amplifier (3), an averaging circuit (4), a threshold level adjustment circuit (7) and a threshold summing circuit (5) connected to the outputs of the averaging circuit and the threshold level adjustment circuit, wherein an error signal produced by the amplifier (3) is used to modify the current value of the averaging circuit (4) and the output from the latter is summed in the threshold summing circuit (5) with the output signal from the threshold level adjustment circuit (7). The resultant output signal from the threshold summing circuit is compared in said comparator (6) with the video signal to output a reject signal in the event that the video signal is greater than the output signal from the threshold summing circuit (5).
Description
TITLE: METHOD AND APPARATUS FOR DETECTING AND
COMPENSATING CHANGES IN PRODUCT REFLECTANCE IN OPTICAL SCANNING DETECTION AND REJECTION SYSTEMS.
This invention' relates to a method and apparatus for providing continuous, automatic background compensation for a scanning optical detection system.
It is known that certain systems use a calibration circuit to adjust their base level to that of the background in view at the time of calibration. A common problem that exists in these systems is due to variations in illumination, and changes in product colour, this reduces the system efficiency and requires constant re-calibration.
In any optical detection system used to reject foreign material from a. flow of product, it is essential that a visual difference exists between the normal product and the foreign material to be rejected. The system performance is directly related to the reject system's ability to act on this difference. In the system, fluctuations in illumination, product colour, dust, steam, or any other obscuring gas or material, will cause the normal product signal level to alter. When a fixed reject signal is compared with a camera signal, some fixed tolerance would be made above the level of these fluctuations, whereby only foreign material with a difference greater than these
fluctuations would be rejected.
An object of the present invention is to provide a method and apparatus for continuous automatic detection and compensation of changes in the level of a reflected background camera signal from a product stream, due to changes in illumination, product colour or other causes, in an optical scanning detection system.
It is a further object of this invention to provide such a method and apparatus that the background compensation signal will continually adjust the threshold level at which foreign material is rejected.
The above and other objects and advantages of the invention will be apparent from the following description, of the invention, taken in conjunction with the accompanying drawing which shows a block diagram of the signal compensating apparatus.
The video signal from camera 1 is held by the valid data strobe in sample/hold device 2 the output of the sample/hold is compared with the output of an averaging circuit (e.g. running average over a period of 1.5 minutes) 4 to produce an error signal at the output of amplifier 3- This error signal is used to modify the current value of the averaging circuit.
A signal from a manual threshold level adjustment device 7 is summed together with the output of the averaging circuit 4, in a threshold summing circuit 5. The resultant output is compared with the video signal
in a reject pulse comparator 6. If the video signal is greater than the summed threshold signal a reject data pulse will be output from comparator 6. In this manner there is achieved:
1. A method of continuous background compensation of threshold value above which foreign material is rejected.
2. A method in which no calibration is required. The reject data pulse may be fed to a zone decoder logic circuit of an apparatus for providing programmable size and overlap in a detection system as described in our co-pending application no. 8625953 filed simultaneously with the present application.
Claims
1. An apparatus for providing continuous, automatic background compensation in a scanning optical detection system which includes a video camera, a signal sampling means controlled by a valid data strobe and comparator means for comparing the signals from the sampling means and the video signal reference, characterized by an amplifier (3), an averaging circuit (4), a threshold level adjustment circuit (7) and a threshold summing circuit (5) connected to the outputs of the averaging circuit and the threshold level adjustment circuit, wherein an error signal produced by the amplifier (3) is used to modify the current - value of the averaging circuit (4) and the output from the latter is summed in the threshold summing circuit (5) with the output signal from the threshold level adjustment circuit (7), the resultant output signal from the threshold summing circuit being compared in said comparator (6) with the video signal to output a reject signal in the event that the video signal is greater than the output signal from the threshold summing circuit (5).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8625954 | 1986-10-30 | ||
| GB868625954A GB8625954D0 (en) | 1986-10-30 | 1986-10-30 | Detecting & compensating changes in product reflectance |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO1988003062A1 true WO1988003062A1 (en) | 1988-05-05 |
Family
ID=10606539
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/GB1987/000766 WO1988003062A1 (en) | 1986-10-30 | 1987-10-29 | Method and apparatus for detecting and compensating changes in product reflectance in optical scanning detection and rejection systems |
Country Status (2)
| Country | Link |
|---|---|
| GB (1) | GB8625954D0 (en) |
| WO (1) | WO1988003062A1 (en) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3782544A (en) * | 1972-08-03 | 1974-01-01 | Amf Inc | Automatic grader |
| DE2411388A1 (en) * | 1974-03-09 | 1975-09-18 | Rwk Rhein Westfael Kalkwerke | Photometrically operated lump mineral sorter - has light analysing sensor head activating sorting mechanism |
| US4454029A (en) * | 1981-05-27 | 1984-06-12 | Delta Technology Corporation | Agricultural product sorting |
-
1986
- 1986-10-30 GB GB868625954A patent/GB8625954D0/en active Pending
-
1987
- 1987-10-29 WO PCT/GB1987/000766 patent/WO1988003062A1/en unknown
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3782544A (en) * | 1972-08-03 | 1974-01-01 | Amf Inc | Automatic grader |
| DE2411388A1 (en) * | 1974-03-09 | 1975-09-18 | Rwk Rhein Westfael Kalkwerke | Photometrically operated lump mineral sorter - has light analysing sensor head activating sorting mechanism |
| US4454029A (en) * | 1981-05-27 | 1984-06-12 | Delta Technology Corporation | Agricultural product sorting |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8625954D0 (en) | 1986-12-03 |
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