Electronic blackboard which detects an abnormal operating condition by reading a non-image section of a writing surface at power-up
US4760465A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 27, 1985 |
| Grant date | Jul 26, 1988 |
| Priority date | — |
| Expiry date | Nov 27, 2005 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N1/113
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An electronic blackboard includes a writing sheet which extends between a pair of rollers, partly wound therearound, a CCD image sensor for scanning the surface of the writing sheet which is illuminated by a lamp, and a control system including a central processing unit (CPU) for controlling its overall operation. Upon power up, the writing sheet is set in its initial position and the CCD image sensor scans along a non-image line outside of a writing surface of the writing sheet. The presence or absence of any abnormality condition is determined depending on the number of black level data found in the image data read by the CCD image sensor. That is, if the non-image line is defined in a white background area, the image data read by the CCD image sensor with the writing sheet set in its initial position should not include any black level image data other than those produced by noise. Thus, if the number of black level image data is found to be significant, there must be some abnormal condition. The writing sheet is divided into a plurality of pages which can be selectively positioned at a writing position in accordance with a detection hole associated with each page.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.