COMPUTER ENHANCEMENT OF EVIDENCE THROUGH BACKGROUND-NOISE SUPPRESSION

The use of computers to enhance evidence began more than twenty years ago [1] and first came to the authors' attention in 1977 [2,3], althou gh significant success was achieved through image processing as early as 1974. Today, affordable software packages containing many programs are available. These programs may occasionally be used to advantage on weak or obstructed evidence [4,5]. Various terms have been used to de scribe these procedures, including ''computer enhancement'' and ''imag e processing.'' An accurate description of these procedures as used by the authors would be ''the optimization of signal to noise ratio.'' T his signal optimization is achieved largely as a result of two factors . First, the digitization of the image affords the operator far greate r control over each component of the image than is possible with a pho tographic (analogue) image. Second, the computer has the ability to di scriminate between 256 separate values of gray, from black (0) to whit e (255), in contrast to approximately 32 separate values perceived by the human eye. Programs of immediate utility, comprising but a small p art of the software package, will be described and illustrated.