Illumination control circuitry for a film video player electronic strobe light

Claim 1

In a film video player having a quenchable electronic strobe light for illuminating a solid state image sensor by way of projecting a pulse of light via a photographic film onto said image sensor during the vertical retrace interval of a standard television signal, the photographic film having an average density which potentially falls within a first given range above or a second given range below the average density of a properly exposed photographic film, and photosensitive means arranged to produce a light-dependent signal corresponding to the intensity of the light pulse produced by said electronic strobe light, the improvement wherein: (a) logic switching means, operatively coupled to said electronic strobe light, for adjusting the amplitude and the duration of a flash-firing current through said electronic strobe light to adjust the intensity of the light pulse; (b) electronic computer means, responsive to an output of said image sensor, for producing an exposure level signal which is functionally related to the density of the photographic film, and which is thereby functionally related to the energy of the light pulse projected onto said image sensor during the vertical retrace interval; and (c) illumination control circuitry, operatively coupling sid electronic computer means, said photosensitive means, and said logic switching means and responsive to the exposure level signal and to the light-dependent signal, for causing said logic switching means to adjust both the amplitude and the duration of the flash-firing current through said electronic strobe light to produce a series of light pulses of substantially constant energy at the vertical retrace rate of the standard television signal, the amplitude and the duration of the current being cooperatively controlled so that, whenever the average density of the photographic film is within the first or the second given range, the duration of each light pulse is adjusted so that it (1) is greater than a minimum acceptable duration below which the energy of the light pulse cannot accurately be repeated, and (2) is less than a maximum acceptable duration which is no greater than the vertical retrace interval.