Abstract: A technique for producing pixel patterns at different selected wavelengths. A diode laser is repeatedly pulsed and has its temperature changed from pulse to pulse, which causes the output wavelength to change. This allows pixel patterns to be interlaced by the use of dispersive elements such as prisms in the optical train. A temperature shift of about 15.degree. C. provides a wavelength shift of about 30 angstroms, which is usable. A temperature shift of 20.degree. C.-30.degree. C. or more is preferable. The temperature shifts may be accomplished by supplying specific currents below threshold and above threshold. For two-wavelength operation, the laser is driven at a first bias current below threshold for a first non-illumination interval, at a first pulse current above threshold for a first illumination interval, at a second bias current below threshold for a second non-illumination interval, and a second pulse current above threshold for a second illumination interval.

Abstract: Weighted and unweighted convolution filtering processes are provided for decoding bitmap image space representations of self-clocking glyph shape codes and for tracking the number and locations of the ambiquities or "errors" that are encountered during the decoding. This error detection may be linked to or compared against the error statistics from an alternative decoding process, such as the binary image processing techniques that are described herein to increase the reliability of the decoding that is obtained.

Abstract: A variable wavelength discrete optical image bar sequentially generates a plurality of independent pixel patterns at different center wavelengths and a prism disperses those pixel patterns in accordance with their respective wavelengths. Lateral dispersion increases the spatial addressing capacity of the image bar.In line printers and the like where a recording medium is exposed to successive pixel patterns as it is advancing in a cross-line direction with respect to a linear image bar, the wavelength dependent dispersion of the prism system may be employed to partially or completely compensate for such cross-line motion. This cross-line dispersion may be used independently to cause the image bar to overwrite successive pixel patterns, or it may be combined with the lateral dispersion of the pixel patterns to increase the spatial addressing capacity of the image bar.

Abstract: A discrete image bar having defective pixel generators redundantly addresses all pixel positions within an address space to produce an essentially defect free image. To that end, the footprint of the pixel generators of the image bar is shifted back and forth across an integer number of pixel positions widthwise of the address space as a function of time, and the input data for the image bar is synchronously countershifted in the opposite direction across an equal number of pixel generators, thereby sequentially bringing at least two different pixel generators into imaging alignment with each pixel position, without materially affecting the address space alignment of the input data.

Abstract: An optical image bar utilizing polarized light and a coherent spatial light modulator, includes birefrigent spatial or angular shearing means for uniformly dividing the spatially modulated radiation of a coherent image bar into a pair of laterally offset, redundantly modulated, orthogonally polarized optical field distributions. Imaging optics, which include any spatial filtering and/or polarization filtering elements needed for converting those field distributions into correspondingly modulated spatial intensity distributions, bring the filtered field distributions to focus on an output image plane, thereby producing redundantly modulated, laterally offset, intensity profiles on the output image plane which spatially sum with each other on an intensity basis.

Abstract: An optical image bar having a spatial light modulator includes means for decomposing the spatially modulated output radiation of the modulator into a plurality of mutually orthogonal, laterally offset, redundantly modulated, optical field distributions for producing an essentially null-free image, without significantly affecting the resolution of the image bar.

Abstract: An acousto-optic deflector that utilizes second order diffraction in a birefringent crystal provides doubled resolution while maintaining high diffraction efficiency. For the second order birefringent deflector employing a paratellurite crystal, 1200 spot resolution was achieved with a 24 MHz bandwidth and 25 .mu. sec access time. This maximum number of spots is twice that obtainable in a conventional first order acousto-optic deflector.