Optics: image projectors – Lamp control
Reexamination Certificate
2007-10-02
2007-10-02
Philogene, Haissa (Department: 2821)
Optics: image projectors
Lamp control
C348S744000, C348S759000, C315S291000, C315S224000, C315S307000
Reexamination Certificate
active
11212744
ABSTRACT:
A projector according to the present invention comprises a lamp driving control circuit for driving an ultra-high pressure mercury lamp at a driving frequency which is changed within an allowable frequency range. For example, the lamp driving control circuit may randomly select a frequency within the allowable frequency range, or modulate the highest frequency within the allowable frequency range such that the frequency is reduced, to change the driving frequency. Consequently, the driving frequency for a fixed pixel panel is not in synchronization with the driving frequency for the ultra-high pressure mercury lamp, and the driving frequency for the ultra-high pressure mercury lamp is changed within the allowable frequency range, causing variations in location at which flicker occurs during projection of an image. Such flicker is less perceivable to human's eyes due to the human's visual characteristics. As a result, the projector which comprises an AC-driven light source lamp can prevent flicker (light/dark noise) and prevent a reduction in the lifetime of the lamp even when the projector is applied with a variety of video signals which include vertical synchronizing signals at different frequencies.
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NEC Viewtechnology Ltd.
Philogene Haissa
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