Apparatus and method for focus control
CA 2192140 C · Owner: Ceshkovsky, Ludwig · Inventors: Ceshkovsky, Ludwig
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
Control apparatus and method are disclosed for shifting focus on a multilayered optical medium using closed loop servo operation. The outputs of an astigmatic optical pickup are independently modified by a control signal generator according to a predetermined time varying pattern to produce a deceptive error signal that changes the apparent focal offset seen by a servo circuit. While in closed loop mode the servo tracks the shifting apparent focal plane from a first information layer of the medium toward a second information layer. Thereafter the control signals are removed and the servo locks focus on the second information region.
Read the whole patent
Listed from its CIPO record in Patent Yard's archive of Canadian patents past their term. Its claims, description and drawings are in the CIPO record and on Google Patents, and the Claude kit works from them.
Why it's free to use
- Filed December 5, 1996 and granted February 12, 2002. A Canadian patent filed from October 1, 1989 lasts 20 years from filing, so its term ended December 5, 2016.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by December 5, 2018.
- We check Canadian rights only. A patent in its family in another country could still be in force: check its family on Google Patents.
Timeline
Timeline From CIPO dates
Sources & verification
Official CIPO records
Everything on this page comes from the CIPO record linked above. Contains information licensed under the Open Government Licence – Canada.