Abstract: Optical scanning apparatus of the invention has a scanning range with a large depth of field through the use of a plurality of light sources, which are disposed in a cluster and directed at the bar code to be read thereby increasing the amount of light at the focal plane. This increases the depth of field in which the scanner is effective. A rectangular aperture stop with a length several times the width controls the F/# and allows an increased amount of light to reach the photodetector. A rectangular receiving slit provides an elliptical field of view of the photodetector with the long axis aligned with the bars of the code to be read, so that the scanner is able to "see" a major portion of the bar or space instead of a small area which may contain printing errors. Thus the intensity of illumination on the object being scanned is maximized, while the depth of the field, and the signal to noise ratio of the receiving system is also maximized so as to enable the resolution of fine, dense, bar codes.

Abstract: A laser scanner wherein an elliptical laser light beam is directed to the target (a bar code symbol) so as to increase the signal to noise ratio of the laser light received by the photodetector. The use of laser light in the shape of an ellipse, instead of the prior spherical shaped laser light, where the long axis of the elliptical laser light is aligned with the bars of the code being read reduces the distortion of the optical signals received by the photodetector. Thus the signal to noise ratio is maximized so as to enable the resolution of fine, dense bar codes.

Abstract: A system for optically scanning objects, particularly bar codes over a large depth of field, uses a incandescent light source to illuminate the bar code and scans the field using a rotating polygon having mirrors with different curvature on different facets thereof which provides scanning in different focal planes in the field while temporally multiplexing these planes. The optical, electronic and mechanical components are modularly packaged on a printed circuit board adapted to be contained in a housing which may be held near and pointed at the code when it is desired to read the code.