Laser video projector
Encyclopedia
A laser video projector is a video projector
that modulates a laser
beam in order to project a raster
-based image. The systems work either by scanning the entire picture a dot at a time and modulating the laser directly at high frequency, much like the electron beams in a CRT
, or by optically spreading and then modulating the laser and scanning a line at a time, the line itself being modulated in much the same way as in a DLP. When well implemented this technology produces the broadest color gamut
available in practical display equipment today, because lasers produce truly monochromatic primaries.
signal is introduced to the laser beam by an acousto-optic modulator
(AOM) that uses a photorefractive
crystal to separate the beam at distinct diffraction angles. The beam must enter the crystal at the specific Bragg angle of that AOM crystal. A piezoelectric element transforms the video signal into vibrations in the crystal to create a diffraction grating
.
The first order diffraction signal is used and the other beams discarded.
-mounted mirror which provides the vertical refresh
. Another way is to optically spread the beam and modulate each entire line at once, much like in a DLP, reducing the peak power needed in the laser and keeping power consumption constant.
s, planetariums, and for flight simulators and other virtual reality applications.
Due to the special features of laser projectors, such as a high Depth of Field
, it is possible to project images or data onto any kind of projection surface, even non-flat. Typically the sharpness, color space, and contrast ratio are higher than those of other projection technologies - for example, the on–off contrast of a laser projector is typically 50,000:1 and higher, while modern DLP and LCD
projectors range from 1000:1 to 40,000:1. In comparison to conventional projectors, laser projectors provide a lower luminous flux output, but because of the extremely high contrast the brightness actually appears to be greater.
Video projector
A video projector is an image projector that receives a video signal and projects the corresponding image on a projection screen using a lens system. All video projectors use a very bright light to project the image, and most modern ones can correct any curves, blurriness, and other...
that modulates a laser
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...
beam in order to project a raster
Raster scan
A raster scan, or raster scanning, is the rectangular pattern of image capture and reconstruction in television. By analogy, the term is used for raster graphics, the pattern of image storage and transmission used in most computer bitmap image systems...
-based image. The systems work either by scanning the entire picture a dot at a time and modulating the laser directly at high frequency, much like the electron beams in a CRT
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...
, or by optically spreading and then modulating the laser and scanning a line at a time, the line itself being modulated in much the same way as in a DLP. When well implemented this technology produces the broadest color gamut
Gamut
In color reproduction, including computer graphics and photography, the gamut, or color gamut , is a certain complete subset of colors. The most common usage refers to the subset of colors which can be accurately represented in a given circumstance, such as within a given color space or by a...
available in practical display equipment today, because lasers produce truly monochromatic primaries.
Laser signal modulation
The videoVideo
Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...
signal is introduced to the laser beam by an acousto-optic modulator
Acousto-optic modulator
An acousto-optic modulator , also called a Bragg cell, uses the acousto-optic effect to diffract and shift the frequency of light using sound waves . They are used in lasers for Q-switching, telecommunications for signal modulation, and in spectroscopy for frequency control. A piezoelectric...
(AOM) that uses a photorefractive
Photorefractive effect
The photorefractive effect is a nonlinear optical effect seen in certain crystals and other materials that respond to light by altering their refractive index....
crystal to separate the beam at distinct diffraction angles. The beam must enter the crystal at the specific Bragg angle of that AOM crystal. A piezoelectric element transforms the video signal into vibrations in the crystal to create a diffraction grating
Diffraction grating
In optics, a diffraction grating is an optical component with a periodic structure, which splits and diffracts light into several beams travelling in different directions. The directions of these beams depend on the spacing of the grating and the wavelength of the light so that the grating acts as...
.
The first order diffraction signal is used and the other beams discarded.
Horizontal and vertical refresh
A rapidly rotating polygonal mirror gives the laser beam the horizontal refresh modulation. It reflects off of a curved mirror onto a galvanometerGalvanometer
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...
-mounted mirror which provides the vertical refresh
Refresh rate
The refresh rate is the number of times in a second that a display hardware draws the data...
. Another way is to optically spread the beam and modulate each entire line at once, much like in a DLP, reducing the peak power needed in the laser and keeping power consumption constant.
Applications
There are several realizations of laser projectors; one example being based on the principle of a flying light spot writing the image directly onto a screen. A laser projector of this type consists of three main components: a laser source uses the video signal to provide modulated light composed of the three sharp spectral colors (red, green, and blue) which a flexible, fiber-optic waveguide then transports to a relatively small projection head. The projection head deflects the beam according the pixel clock and emits it onto a screen at an arbitrary distance. Such laser projection techniques are used in Handheld projectorHandheld projector
A Handheld projector is an emerging technology that applies the use of an image projector in a handheld device...
s, planetariums, and for flight simulators and other virtual reality applications.
Due to the special features of laser projectors, such as a high Depth of Field
Depth of field
In optics, particularly as it relates to film and photography, depth of field is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image...
, it is possible to project images or data onto any kind of projection surface, even non-flat. Typically the sharpness, color space, and contrast ratio are higher than those of other projection technologies - for example, the on–off contrast of a laser projector is typically 50,000:1 and higher, while modern DLP and LCD
LCD projector
An LCD projector is a type of video projector for displaying video, images or computer data on a screen or other flat surface. It is a modern equivalent of the slide projector or overhead projector...
projectors range from 1000:1 to 40,000:1. In comparison to conventional projectors, laser projectors provide a lower luminous flux output, but because of the extremely high contrast the brightness actually appears to be greater.
Manufacturers of Projectors in production
- LDT Laser Display Technology GmbH - High-end laser projectors with double amount of colors and high contrast of 50.000:1 for the following applications: simulation, planetaria and virtual reality.
- Evans and Sutherland - 2000 and 8000 LumenLumen (unit)The lumen is the SI derived unit of luminous flux, a measure of the total "amount" of visible light emitted by a source. Luminous flux differs from power in that luminous flux measurements reflect the varying sensitivity of the human eye to different wavelengths of light, while radiant flux...
projectors for large screen high resolution (8K8K Video Format8K is a digital video format standard. It is used as a master format for movies shot with digital cameras, or sometimes used for high quality master transfers from analog to digital....
) applications - Microvision ShowWX - 15 LumenLumen (unit)The lumen is the SI derived unit of luminous flux, a measure of the total "amount" of visible light emitted by a source. Luminous flux differs from power in that luminous flux measurements reflect the varying sensitivity of the human eye to different wavelengths of light, while radiant flux...
Handheld mobile projector and OEMOEMOEM means the original manufacturer of a component for a product, which may be resold by another company.OEM may also refer to:-Computing:* OEM font, or OEM-US, the original character set of the IBM PC, circa 1981...
component - Light Blue Optics - 4 LumenLumen (unit)The lumen is the SI derived unit of luminous flux, a measure of the total "amount" of visible light emitted by a source. Luminous flux differs from power in that luminous flux measurements reflect the varying sensitivity of the human eye to different wavelengths of light, while radiant flux...
projector - Colorado Springs, CO office closed as of 09/01/2011
See also
- Digital projector
- LCD projectorLCD projectorAn LCD projector is a type of video projector for displaying video, images or computer data on a screen or other flat surface. It is a modern equivalent of the slide projector or overhead projector...
- Laser light show