Floating disc photoconductive film reader

DETAILED DESCRIPTION The invention includes a high speed rotating disc having one or more reader heads located on its lower face near the edge and placed above the photoconductive film such that the film moves longitudinally under the disc as it rotates.
The disc is rotated at a sufficiently high speed so that the reader head floats aerodynamically on top of the film.
The reader head may be composed of, for example, a linear array of N-sense electrodes.
The sense electrode may be the floating electrodes to a charge coupled device (CCD) produced for this purpose.
The disc rotation rate is set so that as it makes one revolution, the reader head reads an area on the film specified by n-pixel elements long and across the arc width of the film.
An arc width is read since the reader head is located on a circular path as the film passes below.
The motion of the film and the speed of the disc are adjusted so that successive read out areas are adjacent to one another and virtually no area of the film is missed by the motion of the read out head.
In the present invention, a reset strip (if needed) is placed continuously along one or both of the longitudinal edges of the photoconductive recording film, rather than across the width of the film at periodic intervals.
The voltage of each of the charge coupled device floating electrodes is thereby reset each time the floating electrode crosses over the reset strip at the edge of the film.
The speed of the disc and hence the film speed is selected so that each image pixel is read out through the charge coupled device (CCD) at a particular video frequency controlled by an external electronic video system connected to the disc read out head.
Furthermore, the rotational velocity of the disc is sufficient to form an aerodynamic boundary layer between the bottom face of the reader head and the film on which the head floats.
Typically, the disc rotates at a rate on the order of 100 to 300 revolutions per minute.
One significant advantage of the invention is that the aerodynamic boundary layer between the reader head and the film maintains a constant distance between the read out head and the film