Page 232 - Concise Encyclopedia of Robotics

Operational Amplifier
some types of robotic systems, positioning errors accumulate unless they
are corrected from time to time. Compare CLOSED-LOOP SYSTEM.
See also ERROR ACCUMULATION and SERVOMECHANISM.
OPERATIONAL AMPLIFIER
See INTEGRATED CIRCUIT.
OPTICAL CHARACTER RECOGNITION (OCR)
Computers can translate printed matter, such as the text on this page,
into digital data. The data can then be used in the same way as if someone
had typed it on a keyboard. This is done by means of optical character
recognition (OCR), a specialized form of optical scanning.
In OCR of printed matter, a thin laser beam moves across the page.
White paper reflects light; black ink does not. The laser beam moves in
the same way as the electron beam in a television camera or picture
tube. The reflected beam is modulated; that is, its intensity changes.
This modulation is translated by OCR software into digital code for use
by the computer. In this way, a computer can actually “read” a magazine
or book.
OCR is commonly used by writers, editors, and publishers to transfer
printed data to digital media such as a computer’s hard drive or CD-
ROM (compact disc, read-only memory). Advanced OCR software can
recognize mathematical symbols and other exotic notation, as well as
capital and small letters, numbers, and punctuation marks.
Smart robots can incorporate OCR technology into their vision systems,
enabling them to read labels and signs. The technology exists, for example,
to build a smart robot with OCR that can get in a car and drive it any-
where. Perhaps someday, this will be commonly done. A robot owner
might hand the robot a shopping list and say,“Please go get these things
at the supermarket,” and the robot will come back an hour later with the
requested items.
For a robot to read something at a distance, such as a road sign, the
image is observed with a video camera, rather than by reflecting a scanned
laser beam off the surface. This video image is then translated by OCR
software into digital data. See OBJECT RECOGNITION and VISION SYSTEM.
OPTICAL ENCODER
An optical encoder is an electronic device that measures the extent to which
a mechanical shaft has rotated. It can also measure the rate of rotation
(angular speed).
An optical encoder consists of a pair of light-emitting diodes (LEDs), a
photodetector, and a chopping wheel. The LEDs shine on the photodetector

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