Optical head device
CA 2043387 C · Owner: Yoshida, Yoshio · Inventors: Yoshida, Yoshio; Miyake, Takahiro; Kurata, Yukio
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
An optical head device having an optical system provided with at least a light source, a shaping prism an, diffracting element and a photodetector. The light source emits light whose intensity distribution has an elliptic shape in its cross section orthogonal to the optical axis. The shaping prism directs the light to a recording medium after shaping the intensity distribution thereof into a circular shape. The diffracting element has diffracting regions formed by at least one division line substantially parallel to a reference direction. The light reflected from the recording medium forms an elliptic bright portion on the diffracting element. The photodetector is divided by a plurality of …
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 May 28, 1991 and granted March 19, 1996. A Canadian patent filed from October 1, 1989 lasts 20 years from filing, so its term ended May 28, 2011.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by May 28, 2013.
- 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.