Automatic focusing system

In a pattern recognition system, means for scanning a field, an optical instrument to facilitate scanning of said field, said field having a plurality of classes of patterns therein, said means for scanning traversing said field in a first direction in a fast scan and in a second direction in a slow scan, means responsive to said scanning means for generating signals corresponding to the colors of said field at the positions scanned, detection means responsive to said signal for detecting when said means for scanning has reached the location of a pattern from one of said classes of patterns, said scanning means traversing said second direction at a first speed until said means responsive to said signals detects said pattern from one of said classes of patterns, and control means responsive to said detection for backing up said scanning means in said second direction and causing said scanning means to traverse said pattern at a second speed slower than said first speed and focus means responsive to said scanning means during said scan at said slower speed to move the position of focus of said optical instrument to its optimum focus position.

A white blood cell classification system for detecting and classifying white blood cells in a peripheral blood smear, said system including means for scanning fields in the blood smear, a microscope for directing said scanning means at said fields, means responsive to said scanning means for generating a signal corresponding to the color of said field at the position scanned, color processing means responsive to said signal for providing a signal representative of the relative darkness of said area scanned, and detection means responsive to said signal, said detection means including a mask which is normally enabled by the nucleus of all the white cells, but which is not enabled by a platelet or foreign material in the blood smear and focus means responsive to said detection means for moving the position of focus of said microscope to optimum focus position after each white cell is detected.