The Hinman Collator, an early optical collator, was an opto-mechanical device for comparing pairs of documents for differences in the text. Documents that appeared similar were said to “collate”. The collator resulted in rapid advances in the study of literary works.
Invented by Charlton Hinman in the late 1940s, the device used lights and mirrors to superimpose images of the two documents so that differences in text alignment or wording stood out. This resulted in huge improvements in speed and efficiency compared to the traditional cross-referencing of texts by eye.
http://en.wikipedia.org/wiki/Hinman_Collator
http://etext.virginia.edu/bsuva/sb/images/public/sb53pl03.jpg
http://linguafranca.mirror.theinfo.org/9706/fieldnotes.html
http://etext.virginia.edu/bsuva/sb/images/public/sb53pl07.jpg
A blink comparator was a viewing apparatus used by astronomers to find differences between two photographs of the night sky shot using optical telescopes such as astrographs. It permitted rapidly switching from viewing one photograph to viewing the other, "blinking" back and forth between the two taken of the same area of the sky at different times. This allowed the user to more easily spot objects in the night sky that changed position. It was also sometimes known as a blink microscope.
http://en.wikipedia.org/wiki/Blink_comparator
