Method and apparatus for placing information on a medium while compensating for deviations from a characteristic time period
US4786919A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 29, 1986 |
| Grant date | Nov 22, 1988 |
| Priority date | — |
| Expiry date | Jul 29, 2006 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N2201/04794
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A laser scanning apparatus is provided with a compensating arrangement whereby deviations of a synchronous drive are compensated for by adjusting the frequency with which the laser beam is modulated. The laser beam is directed onto a rotatable spinner which causes the laser beam to scan a synchronized moving medium in a number of sequential and parallel lines, each of which is determined during a cycle of the movement of the spinner. The spinner is driven by a synchronous motor. During each cycle, a period error is measured to determine a compensating signal which is held for the next successive cycle and is used to control the frequency of a variable oscillator which determines the clocking rate at which information is employed to modulate the laser beam. According to the method of the invention, lines of information are placed on a synchronized moving medium responsive to the aforesaid laser beam during successive cycles. The method involves modulating the laser beam in accordance with the information and at a frequency which is modified for each cycle in accordance with the deviation of the preceding cycle with respect to a characteristic normal time period.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.