Compaq 4000N - Manual (Page 191)

Technical Reference Guide
Compaq Personal Computers
Changed - November 1996
C-17
C.3.1.1 Resolution/Shade Depth
The drive motor mechanism of the CIS supports a vertical resolution of 400 dpi. The CIS
provides a maximum horizontal resolution of 200 dpi. These factors provide true spatial
resolutions of 100 and 200 dpi. Using horizontal interpolation, pseudo 300 and 400 dpi spatial
resolutions are possible. Shade depth is determined by the number of bits used to control each
pixel. The bits per pixel (bpp) parameter can be set to one (for black and white), two, four, or
eight (for 256 shades of gray).
The selected resolution/shade depth determines the scanning time of a given sheet. Table C-3
lists the approximate scanning times for a standard 11 inch sheet using specified resolution/shade
depths based on the line integration time of 2.5 ms.
Table C–3. Scanner Performance Chart
Table C-3.
Scanner Performance Chart
X / Y DPI 1 bpp 4 bpp 8 bpp
100 / 100 100 7 sec 11 sec 14 sec
200 / 200 200 7 sec 27 sec 36 sec
200 / 300 300 (Pseudo) 12 sec 60 sec 60 sec
200 / 400 400 (Pseudo) 17 sec 62 sec 80 sec
NOTE:
Scan times measured on a Pentium/90-based system with 16 MB RAM.
C.3.1.2 Image Quality
Brightness is fully programmable and independently adjustable using either normal or intelligent
methods. The normal method slices each gray scale pixel into either black or white depending
on the threshold value selected. The intelligent method automatically adjusts the pixel to the
background for the best detail.
The grayscale transfer function can be tailored by gamma correction values that are downloaded
from the system. This function can be disabled if desired.
Compensation for the Modulation Transfer Function (MTF) of the optical system and document
motion is provided for improving image quality. The MTF parameters are /downloaded from the
host if (if enabled).
Image compression is provided through a table-driven compressor. Compression values are
loadable from the host and used by one of two types of algorithms: Huffman DPCM for 2- to 8-bit
grayscale images, and a proprietary 1-bit compression.
Scan Time for 11” Page