Digital Photofinishing Systems Using Digital Light Processing

摘要

Digital Light Processing~(TM) Systems have been developed at Texas Instruments for display and printing applications. Both utilize a digital silicon spatial light modulator (SLM) called DMD. The DMD array is a three dimensional, micro-electromechanical system (MEMS) that is a very fast, efficient modulator of broad-band light. The DMD is a reflective SLM, and thus well suited for the exposure of silver halide (AgX) film and color negative print paper, because it can modulate sources that are well matched to the photographic media. DLP~(TM) exposure subsystems are therefore possible candidates for digital minilabs, inline index printing, and high speed maxilab printing systems. The precise digital control of exposure at high bit-depths, the uniform panchromatic response, and the very high reliability of the DMD lend distinct advantages to the emerging digital photofinishing industry. Ease of calibration and alignment, along with exposure constancy over time, are essential to the new digital products. This paper discusses the requirements for DLP~(TM) exposure systems for minilab applications. The DMD device, optics. control electronics, and the concept behind the exposing process are described. Details of image quality resulting from inherently square, non-overlapping DMD pixels are discussed and compared with gaussian exposure processes characteristic of laser polygon and CRT systems. The critical image quality details are discussed, and the implementation of a digital resolution translator (DRT) to eliminate banding due to paper transport motion artifacts is described. Future extensions of DLP~(TM) systems to wide formats and higher process speeds are considered. Recent announcements incorporating DLP~(TM) subsystems in minilab photofinishing products are included for reference.