METHOD AND APPARATUS FOR STEPPED IMAGING IN READING DATA

A method and apparatus for reading data in a data field on a data surface of a storage medium in which the data surface may be nonplanar and depthwise regions of the data field are brought one-by-one into the region of focus of a CCD area array. A set of partial images are formed which are then merged together into a composite image of the data field to be read. The storage medium is disposed on a vacuum chuck. Imaging optics, such as a single lens, zoom lens or lenticular array images regions of the data surface which are within a region of focusing onto the CCD area array. A piezoelectric device or a linear variable differential transformer serve as a Z-axis focussing element which responds to oscillator or electrical control signals to change the relative distance between the CCD area array and a reference plane of the data surface. The partial images formed are either merged in semiconductor memory by a processor or are merged automatically by the CCD area array.