Laser projectors
Encyclopedia
A laser projector is a collection of laser
s, mirror
s, a galvanometer
scanners and other optical components housed in an enclosure. A laser projector can contain one laser light source for single color projection or possibly three sources for RGB
(red, green, and blue) full color projection.
Laser Diodes
Solid State
signal. They are driven by amplifier
s that are not too dissimilar to audio
power amplifiers, that in the case of closed loop devices have the ability to take a feedback signal from the scanner to make an accurate, quick and repeatable placement of the mirror position.
(DAC) is needed to convert the digital control signal from the computer into analog signals that control the scanners in the laser projector. Typically, 2 channels are used for x-y position control and 3 channels are used for controlling the RGB values of an RGB projector. In the case of a single color projector, the intensity channel is used instead of the RGB channels. Most commercially available projectors and DACs are compatible with the ILDA standard that specifies the channels and pinout for the 25-pin D-SUB input connector on the projector.
(DMX) input. DMX was originally designed to control theatrical lighting, but has spread to laser projectors over the years.
DMX allows the user to control the inbuilt patterns of the projector. A few of these features are Size, pattern, colour and rotation. However, DMX Does Not let you design and display your own graphics/animations, it is simply just a way of controlling the patterns included in your laser projector. A Digital to Analog Converter (DAC) is required for custom graphics/animations.
Dichroic
A dichroic mirror is a mirror with different reflection or transmission properties at two different wavelengths. Typical dichroic mirrors used in laser projectors pass red light and reflect green and blue, or pass green light and reflect red and blue. Dichroic mirrors are required for combining laser beams of different colors, e.g. to combine the red, green and blue beams into a single white-light beam. The individual red, blue and green lasers are then controlled in brightness (modulated) to produce any desired color in the final beam. A typical analog-modulated RGB projector has 256 brightness levels for each laser. This gives (256 x 256 x 256) 16,777,216 different available colors (the same as a modern computer monitor).
is used to control the intensity of the output beam. This signal is usually a voltage in the range of 0 V to 5 V. With an RGB laser and analog modulation you have, with an 8 bit system, 16.7 million colours at your disposal.
.
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
s, mirror
Mirror
A mirror is an object that reflects light or sound in a way that preserves much of its original quality prior to its contact with the mirror. Some mirrors also filter out some wavelengths, while preserving other wavelengths in the reflection...
s, a galvanometer
Galvanometer
A galvanometer is a type of ammeter: an instrument for detecting and measuring electric current. It is an analog electromechanical transducer that produces a rotary deflection of some type of pointer in response to electric current flowing through its coil in a magnetic field. .Galvanometers were...
scanners and other optical components housed in an enclosure. A laser projector can contain one laser light source for single color projection or possibly three sources for RGB
RGB color model
The RGB color model is an additive color model in which red, green, and blue light is added together in various ways to reproduce a broad array of colors...
(red, green, and blue) full color projection.
Laser DiodesDiodeIn electronics, a diode is a type of two-terminal electronic component with a nonlinear current–voltage characteristic. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material connected to two electrical terminals...
(Direct Injection)
- Red: 635 nmWavelengthIn physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
, 642 nm, 650 nm, 660 nm - Blue: 445 nm
- Violet: 405 nm
Solid StateSolid-state laserA solid-state laser is a laser that uses a gain medium that is a solid, rather than a liquid such as in dye lasers or a gas as in gas lasers. Semiconductor-based lasers are also in the solid state, but are generally considered as a separate class from solid-state lasers .-Solid-state...
DPSS (Diode-Pumped, Frequency-Doubled)
- Red: 671 nm
- Green: 532 nm
- Blue: 473 nm, 457 nm
Gas lasers
- Red: HeNe (Helium-Neon) @ 632.8 nm, Krypton @ 647.1 nm
- Green: ArgonArgonArgon is a chemical element represented by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table . Argon is the third most common gas in the Earth's atmosphere, at 0.93%, making it more common than carbon dioxide...
@ 514.5 nm - Blue: Argon @ 488nm or 457.9 nm
- Multi-colour (whitelight): Mixed gas Argon/KryptonKryptonKrypton is a chemical element with the symbol Kr and atomic number 36. It is a member of Group 18 and Period 4 elements. A colorless, odorless, tasteless noble gas, krypton occurs in trace amounts in the atmosphere, is isolated by fractionally distilling liquified air, and is often used with other...
647.1 nm, 514.5 nm, 488 nm, 476.5 nm, 457.9 nm
Galvanometer scanners
Galvanometers, sometimes referred to as "scanners" or "Galvos", are electromagnetic devices that move mirrors which reflect the laser beam and essentially create the patterns, text or animations. The mirror is mounted on the end of a rotary shaft that is deflected when power is applied to the device. Galvos are typically identified by their speed of operation measured in Kpps (kilo points per second). 8k, 12k, 20k, 30k, 35k, 50k, 60k are all speeds that are generally available. The faster the galvos, the smoother and more flicker-free the projected image is. Each galvo moves the beam in one plane, either X axis ot Y axis. Placing the galvos close together at 90 degrees to each other allows full movement of the laser beam within a defined square area. The most useful specifications of a galvo pair for laser show use are the speed at which the galvo can draw points and the angle at which this speed is achieved. Galvos come in two main groups, open loop and closed loop (most prevalent) defining the presence of a feedbackFeedback
Feedback describes the situation when output from an event or phenomenon in the past will influence an occurrence or occurrences of the same Feedback describes the situation when output from (or information about the result of) an event or phenomenon in the past will influence an occurrence or...
signal. They are driven by amplifier
Amplifier
Generally, an amplifier or simply amp, is a device for increasing the power of a signal.In popular use, the term usually describes an electronic amplifier, in which the input "signal" is usually a voltage or a current. In audio applications, amplifiers drive the loudspeakers used in PA systems to...
s that are not too dissimilar to audio
Sound recording and reproduction
Sound recording and reproduction is an electrical or mechanical inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording technology are analog recording and digital recording...
power amplifiers, that in the case of closed loop devices have the ability to take a feedback signal from the scanner to make an accurate, quick and repeatable placement of the mirror position.
Controller (DAC)
In the case of using a computer to control a laser projector, a Digital-to-analog converterDigital-to-analog converter
In electronics, a digital-to-analog converter is a device that converts a digital code to an analog signal . An analog-to-digital converter performs the reverse operation...
(DAC) is needed to convert the digital control signal from the computer into analog signals that control the scanners in the laser projector. Typically, 2 channels are used for x-y position control and 3 channels are used for controlling the RGB values of an RGB projector. In the case of a single color projector, the intensity channel is used instead of the RGB channels. Most commercially available projectors and DACs are compatible with the ILDA standard that specifies the channels and pinout for the 25-pin D-SUB input connector on the projector.
DMX
Many laser projectors and galvanometer sets include Digital MultiplexingMultiplexing
The multiplexed signal is transmitted over a communication channel, which may be a physical transmission medium. The multiplexing divides the capacity of the low-level communication channel into several higher-level logical channels, one for each message signal or data stream to be transferred...
(DMX) input. DMX was originally designed to control theatrical lighting, but has spread to laser projectors over the years.
DMX allows the user to control the inbuilt patterns of the projector. A few of these features are Size, pattern, colour and rotation. However, DMX Does Not let you design and display your own graphics/animations, it is simply just a way of controlling the patterns included in your laser projector. A Digital to Analog Converter (DAC) is required for custom graphics/animations.
DichroicDichroismDichroism has two related but distinct meanings in optics. A dichroic material is either one which causes visible light to be split up into distinct beams of different wavelengths , or one in which light rays having different polarizations are absorbed by different amounts.The original meaning of...
Mirrors
A dichroic mirror is a mirror with different reflection or transmission properties at two different wavelengths. Typical dichroic mirrors used in laser projectors pass red light and reflect green and blue, or pass green light and reflect red and blue. Dichroic mirrors are required for combining laser beams of different colors, e.g. to combine the red, green and blue beams into a single white-light beam. The individual red, blue and green lasers are then controlled in brightness (modulated) to produce any desired color in the final beam. A typical analog-modulated RGB projector has 256 brightness levels for each laser. This gives (256 x 256 x 256) 16,777,216 different available colors (the same as a modern computer monitor).Blanking
Blanking is a state in which the laser beam is turned OFF while the mirrors are changing position during the creation of animations or text. Blanking is an ultra fast operation happening typically hundreds of times per second. New technology solid state lasers use direct electronic control of the laser source to provide the blanking. With gas lasers such as argon or krypton, this was not possible and the blanking would be carried out by use of a third galvanometer that would mechanically interrupt the beam. As new technology was developed, a Poly-Chromatic Acousto-Optic Modulator, or PCAOM was used, that allowed high-speed electronic blanking, intensity control and color selection of a multi-color laser beam.Modulation
Most DPSS lasers used in laser projectors support modulation. Modulation has to do with blanking but is a slightly broader term. A DPSS laser will support either 'analog modulation' , 'TTL modulation' or both. Modulation is usually specified in terms of kHz. 2 kHz can be considered low and 30 kHz can be considered high. Manufacturers do not specify an exact relationship between this number and the behavior of the laser.Analog modulation
An analog signalAnalog signal
An analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...
is used to control the intensity of the output beam. This signal is usually a voltage in the range of 0 V to 5 V. With an RGB laser and analog modulation you have, with an 8 bit system, 16.7 million colours at your disposal.
TTL Modulation
TTL modulation indicates that the laser does not support analog modulation of the output but only ON / OFF control. See blanking. With an RGB laser and TTL blanking you have seven colours at your disposal. Red, Green, Blue, Cyan, Magenta, Yellow, White.ILDA
The International Laser Display Association. A trade association dedicated to promoting the use of laser displays.Scan Angle
This term defines the optical angle that can be achieved by a set of scanners normally at a given rate of points per second. The wider the angle the larger the area covered by the scan will be but the more difficult it will be for the scanner to accurately track due to physical limitations of the mechanical nature of a scanner. As an example a 20 degree angle will provide a 3.5 metre scanned area at a distance of 10 metres from scanner to screen. Scan angles can be easily calculated using standard trigonometryTrigonometry
Trigonometry is a branch of mathematics that studies triangles and the relationships between their sides and the angles between these sides. Trigonometry defines the trigonometric functions, which describe those relationships and have applicability to cyclical phenomena, such as waves...
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