Laser Info.

General Terms

Optical Density A measure of the transmittance of light through an optical material that is based on a logarithmic scale.  Examples: O.D. 1 = 10% transmittance, O.D. 2 = 1% transmittance, O.D. 3 = 0.1% transmittance, O.D. 4 = 0.01% transmittance.

Laser Light Show Glossary

Beam Effect Using the lasers beam as a sculptural element in space (as opposed to shining it on a wall to create graphics) . A common technique is to scan the beam through theatrical smoke.  If a line is scanned you will see a plane of laser light; if a circle is scanned you see a cone.
Lumia A gauze-like effect produced by shining a laser beam through distorting material such as rippled glass.  
Scanner Any device which moves back and forth; usually refers to a galvanometer scanner. Two are needed to draw laser graphics. A mirror on each scanner moves in response to an electrical current. The scanners are arranged so the beam reflects first off one mirror, then off the other.  The first mirror moves the beam horizontally, the second moves it vertically. This arrangement means the scanners can position the beam anywhere within a square area.  By repeatedly scanning the same signal at high speeds, the illusion of a single, fixed image is created.
Scanner Amp An electronic device which conditions a signal from a computer or other source, and makes it compatible with galvanometer scanners.  Closed-loop scanner amplifiers are used with position-detecting scanners; the amplifier controls the scanner based on position feedback signals.  Open-loop scanner amplifiers are used with non-position detecting scanners.
Laser Projector Equipment which takes a laser beam and produces projected graphics or beam effects.
Vector Graphics Images created by moving from point to point —examples include handwriting and computer plotters. Most laser graphics are vector graphics. To produce a laser graphic, a computer is first used to draw a series of connect-the-dot points.  These are translated to electrical signals and are sent to the scanners. At the projection screen, the moving beam travels from point to point at high speeds, smoothing out the dots.  This creates the illusion of a fixed, non-moving image.
Blanking The technique of turning the laser beam on and off with precise control (as opposed to chopping).  For scanned graphics blanking allows images to have disconnected sections where the beam is hidden.  Blanking can be digital (on/off) or analog (continuous intensity control). Blanking can be performed with a third scanner, an acosto-optic modulator, or by electronically contolling the laser output as done with semiconductor lasers.
ILDA Speed Ratings The International Laser Display Association has developed a standard to measure the performance of scanners and scanner driver cards.  The two most common “standard” speeds for scanners is 12,000 points-per-second and 24,000 points-per-second while displaying the ILDA test pattern.  Speed standards are designed to help make artwork compatable with different scanners and scanner amps.  When displaying artwork that was designed for slower scanners on high-speed scanners, the points that make up the artwork may become apparent. To eliminate this the scanners must be tuned to a slower speed.

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