produce a high resolution image of the reticle 18 on the substrate 20 the projected image of the reticle 18 can be enlarged or reduced as required the projection lens 16 can include reflective or diffractive elements as well as refractive elements or combinations of such elements such as in catadioptric optics the reticle 18 also referred to as a u201c mask u201d includes one or more patterns intended for projection onto the substrate 20 and can be sized within or beyond the field captured by the projector lens 16 reticles with larger patterns can be relatively translated with respect to the projection lenses to expose different parts of the reticle patterns in succession the photosensitive substrate 20 generally takes the form of a flat plate such as a semiconductor wafer or glass panel treated with a photoresist to react to exposures of light often the entire substrate 20 cannot be imaged at once so the horizontal x y axis translational stage 22 on a base 30 provides for translating the substrate 20 through a range of positions for collectively illuminating a desired working area of the substrate 20 the projection lens 16 is supported on the vertical z axis translational stage 26 above the.