Contrast determining apparatus and methods
US6826307B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Mar 24, 1999 |
| Grant date | Nov 30, 2004 |
| Priority date | — |
| Expiry date | Mar 24, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06T2207/30164
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
The contrast determination apparatus includes illuminating light sources (12) and an image sensor (26) i.e. a 2-D CCD for capturing a two-dimensional image of e.g. a marked wire (32) on a holder (34), the captured image being sampled over the mark and the background. The sensor includes an optical system (28,30) selected with regard to the character size of the marks so that the field of view of the sensor is sufficient to contain a complete character as well as a generous amount of background. An area of the captured image is designated in which the samples for contrast measurement are to be taken, and a processor (24) takes the pixel values from the image which are thresholded to categorise them as “black”, or “white”, thus forming a two-tone image. Aggregates or averages of the “black” and “white” pixel values are used to derive the contrast measurement according to the formula: (Imax−Imin)/Imax where Imax is the average value of the “white” pixels and Imin the average value of the “black” pixels.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.