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.

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.

Abstract: Such vertical deflection polarity switching circuit for CRT projector can be provided that enables external, one-shot operational switching of the vertical deflection polarity. To switch a CRT projector from a hanging type to a floor type, the switching circuit receives a vertical deflection polarity switching signal from an external device, so that an input sawtooth waveform polarity switching circuit will switch the polarity of a V. SAW signal. At the same time as the polarity of the input sawtooth waveform is switched, power-supply switching circuits switch the driving power-supply voltage of a vertical deflection-use output amplifier. Thus, the polarity of voltage waveforms applied to a vertical deflection yoke is inverted. Also, the polarity of vertical deflection and that of vertical-system data of correction waveforms for use in each of output circuits for horizontal deflection convergence focus are switched.