Inhibition of exposure in a video printer upon loss of color filter sync

Claim 1

Apparatus for producing a color photographic copy of a color video signal comprising: monochrome electronic display means for displaying an image of a video signal; an exposure station located along a first optical path from said display means at which is positioned a photographic element; video signal circuit means for providing a color video signal constituting frames of interlaced odd and even fields repeated at broadcast field frequency, wherein each field includes three concurrent color component video signals respectively representing first, second and third primary colors of a color field image; selectively actuatable gate means, electrically coupling said circuit means to said display means, for applying to said display means only one color component signal from each field of said three concurrent color component signals provided by said circuit means; a first rotatable filter having first, second and third primary color filters sequentially movable into said optical path; first means for continuously rotating said first filter; control means including a microprocessor (1) for synchronizing the continuous rotation of said first filter by said first rotating means with said field frequency of said color video signal; (2) for exposing a photographic element positioned at said exposure station by actuating said gate means in response to detection of said first primary color filter being moved into said first optical path to apply to said electronic display means a sequence of six consecutive color component video field signals constituting odd and even fields respectively of each of said first, second and third primary colors, in the color sequence of first primary color, second primary color, third primary color, first primary color, second primary color, third primary color, as respective corresponding color filters of said first filter are sequentially rotated into said optical path, such that said display means produces a sequence of six consecutive monochrome field images which are filtered by respective corresponding primary color filters to expose said element to a sequence of six color field images corresponding a full frame of a color video image; and (3) for inhibiting the exposure of said photographic element when said first filter is not rotated in synchronism with said field frequency of said video signal.