A method is provided of producing a multiple focus stack image of a target. The stack image has a plurality of images of the target, each image having a corresponding focal range or position. The method utilizes relative scanning movement between the target and an array of light detectors, the array being used to repeatedly receive image information as scan lines from the target during the scan. During the scan the relative focus between the target and the array is modified between the focal range or position of the respective images so as to obtain the images in the stack. Each image is thereby formed from the image information obtained at the respective focal range or position during the scan. Apparatus for performing the method is likewise provided.