Printer and method of forming multiple image pixel sizes on photosensitive media

Printer apparatus and method of forming multiple image pixel sizes on photosensitive media. The printer comprises a light source (170) for projecting a light beam (180) onto the photosensitive media (30) to form the image pixel on the photosensitive media. An aperture system (200) is interposed between the light source and the photosensitive media for adjustably sizing the light beam, the aperture system having an adjustable aperture plate (230) for receiving the light beam therethrough. The aperture system is adjustable for variably masking a predetermined portion of the light beam, so that the image pixel obtains a predetermined size as the predetermined portion of the light beam is masked. The aperture system includes a guide member (210) having parallel spaced-apart grooves (220) therein. The aperture plate, which slidably engages the grooves, has a first aperture (240) of a first size and a second aperture (250) of a second size spaced-apart from the first aperture. The aperture plate is slidable in the grooves from a first position thereof for allowing the light beam to be received through the first aperture, so as to expose a first image pixel size (260a) on the photosensitive media. The aperture plate is also slidable to a second position thereof for allowing the light beam to be received through the second aperture, so as to expose a second image pixel size (260b) on the photosensitive media. A transport mechanism (80, 100, 110, 130) transports the light source and aperture system relative to the photosensitive media. Actuators (270a/b) engage the aperture system due to excess travel of the transport mechanism beyond the side edges of the media. When this occurs, the actuators actuate the aperture system, so that the desired aperture is selected.