CRT film scanner with compensation for local brightness variations of scanning beam

A flying spot film scanner apparatus for producing colour television signals from photographic film, comprising:

• cathode ray tube means for producing a flying spot scanning beam of nominally constant intensity;
• first means for focussing said beam onto an image plane wherein a film is located in use of said apparatus;
• second means for sensing light modulated by the film to produce a plurality of television colour component signals corresponding to differently coloured components of the film;
• a plurality of colour channels for processing respective ones of the colour component signals;
• third means responsive to variations in the overall intensity of the scanning beam prior to modulation by the film to generate a further signal which varies with variations in the overall intensity of the beam;
• and
• fourth means responsive to the further signal to apply different individual corrections to the plurality of colour component signals whereby to compensate at least in part for differential intensity variations across the colour spectrum of the scanning beam, the fourth means comprising means for generating individual correction signals as different proportions of the further signal and means for applying said individual corrections signals to respective ones of the colour channels.