Video projection apparatus with temperature compensation device

Details Video projection apparatus with temperature compensation device Video projection apparatus with temperature compensation device

1984-06-15

1986-09-02

Groody, James J.

Facsimile and static presentation processing

Facsimile

Recording apparatus

358233, 358 64, 350253, H04N 574

Patent

active

046099450

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.

REFERENCES:
patent: 4405949 (1983-09-01), Hockenbrock et al.
patent: 4511927 (1985-04-01), Bauer

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