Abstract: An information compression method and apparatus for information forms in which each from is divided into raster lines. Each raster line is divided into multi-bit units. The information of each unit is compared with that of a preceding unit. Agreement and disagreement codes are stored in a unit memory. The pattern information of disagreeing units only is stored in a pattern memory. Each raster line is then compared with all preceding raster line of this and preceeding forms by means of comparing the respective locations of the unit memory and the pattern memory. When inter-raster agreement is found, the respective locations in a raster memory are given the same address used to access the unit memory and only one set of redundant raster data is stored in the unit and pattern memories.

Abstract: In the optical information recording apparatus, the form slide film having the sensor mark is two-dimensionally scanned so as to detect the drift amount in the vertical scanning direction due to the fluctuation of the optical system of the optical information recording apparatus. The scanning device scans the sensor mark within a predetermined scanning period to produce the pulse signals. The number of these pulse signals is counted and then compared with the reference number so as to produce a difference, i.e., the drift amount. The vertical scanning pitch of the scanning device is controlled based upon the drift amount.

Abstract: An optical linear encoder for converting scanning light beams incident thereupon into a series of pulsatory light comprising light transmission parts for passing through the scanning light beams and light non-transmission parts for blocking transmission of the scanning light beams. The light non-transmission parts are alternately arranged with said light transmission parts in predetermined intervals that are determined by the amount of distortion inherently occurring in an optical system through which the scanning light beams travel.