Image scanner apparatus of the drum type having an efficient line-of-light illumination system

Claim 1

Image scanning apparatus for converting an image recorded on a photographic film to an electrical signal modulated in accordance with such image, said apparatus comprising: (a) a drum rotatable about an axis and having an aperture arranged for movement along a surface of revolution of said drum; (b) a mechanism adapted to clamp an image-bearing film to said drum with the film image aligned with the aperture for rotation therewith substantially in a surface of revolution of said drum; (c) a source of diffuse light disposed between the axis of rotation of said drum and its surface of revolution, said diffuse light source defining an elongate light-emitting slot of width, w, located a distance, d, from the surface of revolution of said drum for forming a relatively narrow line of diffuse illumination extending from one side to the opposing side of the aperture orthogonal to the direction of rotation of said drum, to project the narrow line of diffuse illumination directly onto the image-bearing film orthogonal to the direction at which the film is movably carried on the surface of revolution of said drum, the distance d being approximately one-half the width w so that light emitted through the slot impinges on the film plane over a wide range of incident angles to reduce the influence of scratches and dust on the film image; (d) a stepper motor for rotating said drum in a stepwise manner about its axis of rotation, to move the image-bearing portion of the film orthogonally through the line of diffuse illumination in a series of discrete steps each of which corresponds substantially to the width of the relatively narrow line diffuse illumination at the surface of revolution of said drum; (e) a linear array of a given number of light-responsive elements disposed external to the surface of revolution of said drum; and (f) focusable lens apparatus, interposed between the surface of revolution of said drum and said linear array, selectively positionable as a function of the size of the film image, to focus the portion of the line of diffuse light that is modulated in accordance with the film image illuminated onto said given number of light responsive elements of said linear array, thereby providing variable magnification of said image sensor to adjust the resolution of the film image scanned in a direction corresponding to the orientation of the line of diffuse illumination.540