18WuD2x

498 optical character recognition • optical sound recording
optical character recognition Abbreviation, OCR.
In computer and data-processing operations, the
reading of alphabetical, numerical, and other
characters from hard copy (usually printed matter)
by photoelectric methods. It converts the
characters into digital data that can be stored in
computer memory, on disks and tapes, and
transmitted via digital communications networks.
It can also allow a computer or robot to
read signs, maps, etc.
optical communications One-way or two-way
communications via modulated visible light. It
can be conducted through optical fibers, the
atmosphere, water, or any other transparent
medium.
optical coupler A coupling device consisting essentially
of a light source (actuated by an input
signal) mounted in an opaque housing with a
light-sensitive device (that delivers the output
signal). In its simplest form, the arrangement
consists of a light-emitting diode (LED) and a
photodiode.
Input Mod. Amp. Output
optical coupler
optical detector An integrated-circuit (IC) that
provides light-to-voltage conversion. Its directcurrent
output voltage is proportional to the intensity
of light impinging on its sensor.
optical encoder An electronic device that measures
the extent to which a mechanical shaft has
rotated. It can also measure the rate of rotation
(angular speed). It consists of a light-emitting
diode (LED), a photodetector, and a disk with alternate
light and dark bands (chopping wheel). It
is commonly used in digital controls and jointed
robot arms.
optical fiber A glass or plastic medium through
which light is propagated for optical-communications
purposes. The refractive characteristics of
the fiber keep the visible light inside.
optical lever A device for amplifying the effect of a
small rotation. The rotating member carries a
small mirror that reflects a light beam over a
curved scale, the distance through which the
light spot travels on the scale being proportional
to the distance between the scale and the rotating
mirror. In this way, the deflection on the scale is
several times the length of the arc described by
the mirror, the rotation being thus amplified.
optical link See OPTICAL COUPLER.
optical mark recognition A method of data transfer
that involves the use of optical techniques.
optical maser See LASER.
Mirror
Meter
bearing
optical lever
Stationary
light source
Screen
with scale
Image
optical mode The vibration mode that produces an
oscillating dipole in a crystal lattice.
optical pattern A Christmas-tree-like pattern produced
by parallel rays of light striking a phono
disk. Also see DIFFRACTION.
optical playback See OPTICAL SOUND REPRO-
DUCER.
optical pyrometer A pyrometer for measuring the
temperature of a hot body in terms of the intensity
and color of light it emits.
optical scanner An electronic device that converts
hard-copy text and graphics into digital form
suitable for processing and storage in a computer.
There are several types; the most common
resembles a small photocopy machine and is
known as a flatbed scanner. See OPTICAL SCAN-
NING.
optical scanning An electronic process that converts
hard-copy text and graphics into digital
form suitable for processing and storage in a
computer. Text scanners work in conjunction
with specialized software. The optical scanner
and software together form the equivalent of audio
speech recognition and sound interpretation.
Usually, scanners are employed to convert
printed matter to digital data. However, scanning
technology can also be used at a distance, for example,
by a robot for the purpose of reading road
signs.
optical sound recorder A photoelectric machine
for recording sound on photographic film. Also
see OPTICAL SOUND RECORDING.
optical sound recording A system for recording
sound on photographic film, as in sound motion
pictures. The sound is picked up by a microphone
and amplified to vary the intensity of a light
source. The film passing this modulated beam becomes
exposed to a variable-width or variabledensity
track corresponding to the modulation
(see VARIABLE-DENSITY SOUND RECORD and
VARIABLE-WIDTH SOUND RECORD). When de-