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An example of the Landolt C eye chart (also known as the Japanese eye chart). Numerous types of eye charts exist and are used in various situations. For example, the Snellen chart is designed for use at 6 meters or 20 feet, and is thus appropriate for testing distance vision, while the ETDRS chart is designed for use at 4 meters. [16]
Optical mark recognition (OMR) is the scanning of paper to detect the presence or absence of a mark in a predetermined position. [4] Optical mark recognition has evolved from several other technologies. In the early 19th century and 20th century patents were given for machines that would aid the blind. [2]
The Norden Electronic Vote Tallying System was the first to be deployed, but it required the use of special ink to mark the ballot. The Votronic, from 1965, was the first optical mark vote tabulator able to sense marks made with a graphite pencil. [1] The oldest optical-scan voting systems scan ballots using optical mark recognition scanners ...
Some clinics do not have 6-metre eye lanes available, and either a half-size chart subtending the same angles at 3 metres (9.8 ft), or a reversed chart projected and viewed by a mirror is used to achieve the correct sized letters. In the most familiar acuity test, a Snellen chart is placed at a standard distance: 6 metres.
A fiducial marker or fiducial is an object placed in the field of view of an image for use as a point of reference or a measure. It may be either something placed into or on the imaging subject, or a mark or set of marks in the reticle of an optical instrument.
••E Chart-do-; for those who can not read ••Landolt's broken ring chart-do-; for those who can not read ••Toys pr picture chart-do-; for children •Near vision-do-; to determine visual acuity of near vision ••Jager's chart-do- ••Printer's types of N series-do- ••Snellen's near chart (1/17th reduction of distant chart)
Amsler grid, Chart 1 There are 7 types of Amsler grid charts. All charts measure 10 cm × 10 cm (3.9 in × 3.9 in), which when viewed at a distance of 33 cm (13 in) from the eye can be used to measure defects in the central 20 degrees of the visual field .
This comparison of optical character recognition software includes: OCR engines, that do the actual character identification; Layout analysis software, that divide scanned documents into zones suitable for OCR; Graphical interfaces to one or more OCR engines