Psc Inc.

Gregory William Forbes

Jay M Eastman

Anna M Quinn

In order to control the width of the scanning beam in the scanning direction over a significant range in front of the scanner, an optical assembly including a phase mask is utilized through which the beam passes after being configured into curved wavefronts, as by a lens which provides a focus in the vicinity of the far end of the range. The F/ number of the optical assembly is high and the cone of the beam in the scanning direction is small, for example, less than 5.degree.. The mask is preferably transparent and has a region which may be rectangular, elliptical or circular forming a step through which the center of the beam passes which imposes a phase change with respect to the phase of the wavefronts which do not propagate via the region. The phase change may be uniform or in the form of a weak quadratic phase variation in this region of the mask which changes phase and thus slightly refocuses the beam. The transmissivity of the region may also be varied and reduced with respect to the transmissivity of the mask outside of the region. The beam may be scanned via a scanning mirror or by scanning the optical assembly.

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Sydney, Australia

Gregory William Forbes