With preproduction calibration this slight alteration in fundamental frequency can be detected. This technique appears to have considerable advantage over capacitance gauges and nuclear radiation gauges which are presently being used in yarn mass density measurement. Reference Jeffrey A. Hinkley, Sensors, May 1997. The basic principle involved photographing the pattern of veins on the back of the eye. However this idea has evolved into a most important and promising technique for positive inalterable means of identification.
Material is scanned and separated into red, green, and blue filtered images.
Images are stored on magnetic tape or in a digital editing system. Digital image output. The density range is over 4,000 levels. The recording speed is approximately 20 times that of a video recorder. The electron beam gun records the image directly to film thereby retaining the maximum possible quality during the transfer.