Optical processing method and apparatus for carrying out the same

Abstract

An optical processing apparatus for processing optically a workpiece (7) by using a light beam (B). The apparatus is capable of automatically adjusting a imaging magnification to a predetermined value and at the same time maintaining constant a imaging magnification regardless of exchange of masks (3; 100) and workpieces (7) and for ensuring an extended use life of a mask with satisfactory mask function. The apparatus includes a light source system (1) for generating a light beam (B) for illuminating a mask (3; 100) having a predetermined pattern, a imaging lens (5) for copying a pattern image of the mask (3; 100) onto a workpiece (7), a mask moving mechanism (4) for moving the mask in a direction perpendicular to an optical axis (L) of the imaging lens (5), a workpiece moving mechanism for moving the workpiece in a direction perpendicular to the optical axis (L) of the imaging lens (5), a imaging magnification changing mechanism for changing inter-mask/lens/workpiece distance between the mask, the imaging lens and the workpiece, and a central control unit (9) which is comprised of an actual imaging magnification arithmetic module (91) for determining an actual imaging magnification value (M') in terms of a ratio between the copied pattern image and a predetermined pattern, a magnification decision module (92) for making decision whether or not a difference between the actual imaging magnification value and a desired imaging magnification value is smaller than a permissible value, an optical-axis displacement control module (93) responsive to indication that the difference exceeds a permissible value (.delta.) to thereby arithmetically determine on the basis of the actual and desired imaging magnification values the inter-mask/lens/workpiece distance at which the actual imaging magnification value (M') becomes equal to the desired imaging magnification value (M) for controlling thereby the imaging magnification changing mechanism so that the inter-mask/lens/workpiece distance coincides with the arithmetically determined distance, and a displacement control module for controlling the mask moving mechanism and the workpiece moving mechanism.