| 摘要 |
PURPOSE:To enable a film exposure device to be enhanced in focal point reproducibility by a method wherein a point corresponding to half the sum of parameters obtained while a reticle or the like moves in steps between a point when the parameter which denotes the size of the projected image of a focus mark is coincident with an allowable value and a following point when the parameter is set coincident again with an allowable value is determined to be a focal point. CONSTITUTION:Provided that the crosswise size of a projected image of a focus mark is represented by a parameter alpha, and a reticle or a projection lens (reticle or the like) is made to move in steps along the direction of an optical axis so as to enable the parameter alpha to be coincident with an allowable value i (step l). Then, the reticle or the like is made to move in fine steps along the direction of optical axis in a direction that the parameter alpha becomes smaller from a point where the parameter alphais coincident with the allowable value until the parameter alpha is coincident with the allowable value i again and stopped (step 2). Then, a point corresponding to half the sum of parameters a in alpha step 2 is determined to be as a focal point, and then the reticle or the like is made to move reversely to the determined focal point along the direction of optical axis. |
