The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 02, 1986
Filed:
Jun. 15, 1984
Masanori Oguino, Yokohama, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
In a video projection apparatus including a projection lens, a cathode-ray tube and a projection screen, a layer of a medium whose refractive index n.sub.p decreases with a temperature rise is disposed between the projection lens and the faceplate of the cathode-ray tube, and the thickness l.sub.p of the medium layer is selected to substantially satisfy the following equation thereby compensating the temperature-dependent variation of the focal length of the principal lens: ##EQU1## where .DELTA.T is a temperature variation; .DELTA.n.sub.p is a variation of the refractive index n.sub.p due to the temperature variation .DELTA.T; f is the focal length of the projection lens; K is a constant representing the proportion of the power of plastic lenses to the total power when the projection lens is of a hybrid type; .DELTA.f is a variation of the focal length f due to the temperature variation .DELTA.T; and M is the magnification of projected images.