Integrated-sensor processors ease scanner designs
With explosive growth in demand for sheet-fed and flat-bed scanners, designers need to minimize design and development times. To do so, they will require off-the shelf processors that, when used in conjunction with CCDs, perform all of the analog processing needed to digitize images. These include analog-to-digital conversion from the output of the CCD, pixel-by-pixel gain (shading) correction, and black-level and offset compensation.
Two such devices, the LM9801 from National Semiconductor (Santa Clara, CA) and the AK8406 from AKM Semiconductor (San Jose, CA) have just been introduced to fill these requirements. National`s device operates at a 2.5-Mpixels/s conversion rate, linearizes the pixel stream in the analog domain, digitizes the signal, and generates all the necessary clock signals and control functions to drive the system`s image sensor, correction and data RAM. Steve Null, product manager at National, said, "An internal configuration register sets CCD sampling timing so that designers can adapt various sensors to their systems without sacrificing time to market."
The AKM device operates at 5 Mpixels/s and is functionally similar, according to Shin Miki, manager of sales. "National`s part and ours are perhaps the only standard products for this kind of function on the market. "
Lissy Bland, a hardware engineer with the Xerox Digital Imaging Technology Center (Palo Alto, CA) says that the National processor is being used by her company for analog-to-digital conversion and shading correction in yet-to-be announced products."There are two ways to handle processing CCD signals," she says, "with discrete components or off-the-shelf parts. In terms of price/performance, National`s device met our goals.