63fb46d6_bster_US___Patent_applications__Description
[Patent application number] 20080218801 [Published] 09-11-2008 [Description] 
SYSTEMS AND METHODS FOR CONVERTING COLOR IMAGE DATA TO MONOCHROME OUTPUT - When converting color input from a color scanner or the like to monochrome output, the measured luminance values are reduced, to help avoid the loss of text or other image portions in the monochrome output. The luminance reduction may be performed based on chrominance values.
Xing Li, Webster US - Patent applications