OMR Scanners: Reflective Technology Makes the Difference
Ellizabeth Greenfield · T.H.E. Journal Technological Horizons in Education · 1991
OMR Scanners: Reflective Technology Makes the Difference Optical readers are experiencing a renaissance in both technology and application, or as one company explains, the technology evolutionary rather than revolutionary. This evolution refers to breakthroughs in OMR that make readers more efficient and less expensive. * The Basics OMR scanners were originally developed in the 1950s, with more desktop-sized models becoming available roughly 20 years later. The original technology, called mark sensing, used a series of miniature sensing brushes to detect traces of graphite particles on a document as it passed through the machine. Now fiber optics similar to those used to read bar code symbols are employed. One way to measure OMR efficiency is by the number of forms processed per hour. The presence of a is detected by measuring the amount of light reflected from the surface of a form as it passes under a read head. The forms must be custom-designed, however any type of paper can be used since the is a surface entity; the thickness, color, weight and chemistry of the paper do not affect the reader's ability to determine if a is present. The reading device contains an infrared light source and two sets of optical fibers. Light from one set is reflected off the form and picked up by the second set. In a stand-alone, grading environment, the presence of a in a particular position on the form is recorded and compared against a previously-scanned master. The reader usually acknowledges noncorresponding, incorrect marks by printing a on the form's border. Another use of OMR devices involves a computer and OMR software that recognizes the absence or presence of a in a particular position and translates that data into a computer file. * Common Ground Most optical readers have automatic feed hoppers that hold a certain amount of forms and do not require that an operator be present. Desktop models weigh between 30 and 40 pounds, interface to a computer via an RS232C serial port, and include a mark-density adjustment control. One common way to measure the efficiency of an optical reader is by the number of forms it processes per hour. Two figures are often mentioned: the transport speed and the read speed. The transport speed refers to the maximum number of forms that can be fed through the machine per hour, while read speeds are the actual number of forms. The latter varies, as it is a function of the baud rate, number of timing marks and efficiency of the application program used. New capabilities include being able to read ink marks on forms in addition to lead-generated marks, and to read two sides of a form simultaneously. All OMR scanners mentioned here offer the option of an ink-recognition head and a dual-read head. * The Reader With Memory The Model 8400 Optical Mark Reader from Scantron Corp. transports either 3,000 single-sided or double-sided forms per hour. The unit features a 500-sheet automatic document feeder and a 100-level darkness and discrimination technique that ignores poor erasures and smudges. A built-in forms translator converts data into ASCII text records compatible with dBASE, Lotus 1-2-3, SPSS and Paradox applications programs. It weighs in at 40 pounds and the maximum form length accepted is 14 inches. The 8400 is capable of reading lead pencil and ink marks, as well as bar codes. Descriptions are needed when more than one type of form will be used during one scanning period. Either SCANFORM or SCANBOOK utility programs, which generate form-translation commands from user-defined form descriptions, is included with the reader. These descriptions are needed when more than one type of form will be used during one scanning period. Up to 99 descriptions, and therefore different form types, can be stored in the 8400's 128K memory. …