Reduced height transmissive overhead projector
CA 1330894 C · Owner: Minnesota Mining And Manufacturing Company · Inventors: Vanderwerf, Dennis F.
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
A transmissive overhead projector includes a Fresnel lens assembly which has an f-number of about 0.25 and is capable of dioptrically focusing light at an incident angle of at least 60° with respect to a perpendicular to the Fresnel lens assembly. This refractive power of the Fresnel lens assembly allows the overhead projector light source to be positioned very close to the Fresnel lens assembly and consequently allows a significant reduction in the base height of the overhead projector.
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
- Granted July 26, 1994. A Canadian patent filed before October 1, 1989 lasted 17 years from grant, so its term ended July 26, 2011.
- 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.