LCD Projector Company
The most common type of projector is an LCD model, which accounts for roughly half of all projectors on the market. This technology is found in home-theater, office and portable models.
Compare a projector’s contrast-ratio specs carefully. Many manufacturers use video processing and auto-irise features to increase a projector’s contrast, which can confuse measurement results.
Liquid Crystal Display
Liquid crystal displays are flat screens that use an array of pixels to display a picture. They are very popular in laptop computers because of their high image quality and low power consumption. They can also be very thin. However, they can cause eye-strain because of the rapid flickering of the backlight. This is called pulse-width modulation (PWM) and can cause stroboscopic effects.
Typical LCDs consist of two pieces of glass with a polarizing film on the bottom and a common electrode plane made of indium-tin oxide on the top. Between them is a layer of liquid crystal molecules that are twisted with respect to each other. When light from a backlight passes through the first polarizer, it is reflected off the molecules and passed through the second polarizer at a right angle to the first. The pixels are turned on and off with a series of transistors to create an image.
The higher ambient contrast ratio of OLED makes it a lcd projector wholesale more attractive alternative to LCD. But the lower moving picture response time of LCD can still be an advantage in some applications.
Metal-Halide Lamps
Metal-halide lamps emit a broad spectrum of light and are very effective in projector lighting. They are also very energy efficient and last longer than traditional mercury vapor lights. However, they do require a large power supply and may produce a noticeable amount of heat during operation.
In a metal-halide lamp, the inner arc tube contains the electrodes that ionize mercury vapor to start the arc and the halides (typically some combination of sodium, thallium, indium, scandium, and dysprosium iodides) that control the emission spectral power distribution. A high starting voltage is required to ionize the gas and create the arc. The outer envelope is typically made of borosilicate glass to reduce UV radiation and provide a stable thermal environment during the arc lifetime.
The plastic housing, or module, is usually black and high-temperature resistant. A retaining clip or screw locks the lamp in place. There is a threaded spoke plastered into the back of the quartz globe that sticks out and is used, along with a nut, to hold the electrical wires in place.
LEDs
Compared to traditional projector bulbs, LEDs offer a longer lifespan and fewer maintenance needs. They also tend to produce better image quality and clarity. As a result, they are more popular among art displays.
LEDs operate on a principle called electroluminescence. When a voltage is applied to the chip (positive to the cathode and negative to the anode), current flows through the device and emits light. The first blue-violet LED using magnesium-doped gallium nitride was produced at Stanford University in 1972 by Herb Maruska and Wally Rhines, doctoral students in materials science and engineering.
The brightness of a projector is determined by its light engine, which comprises the LEDs, mirrors and digital micromirror device. The designers of these components work to optimise the etendue, or maximum amount of light that can be accommodated on the imager’s light-receiving surface. This is a major challenge for the manufacturers of LCDs and LED projectors, and it has contributed to the increase in lumens that we have seen in recent years. Exceptional resolution and clarity are important features of any projector for artwork, and LED technology delivers both.
LCoS Imagers
LCOS is the imager technology used by Sony’s SXRD and JVC’s Digital Direct Drive Image Light Amplifier (D-ILA) in many high-end home-theater projectors. Unlike the mirrors in DLP projectors, LCoS chips are fixed and don’t move, so they’re less likely to develop problems like ghosting.
Like DLP, each beam of red, green, and blue light passes through its own imager before being combined with a dichroic prism to form a full-color image for each frame in the video signal. White brightness (aka white light output, WLO) and color brightness are measured independently for the final image and ideally should be identical.
LCOS projectors have the highest native contrast ratio of any digital-projector technology, providing deep blacks and bright whites simultaneously. They can also improve contrast with enhancement techniques such as a dynamic iris and dynamic lamp or laser modulation. Some models use a technique called pixel-shifting, whereby the imagers are shifted back and forth diagonally by half a pixel 120 times per second to double the number of pixels projected onto the screen. This is similar to the process used in Epson’s 4K PRO-UHD and JVC’s e-Shift.
DLP Imagers
DLP uses a semiconductor chip called a Digital Micromirror Device (DMD) that is covered with hinged, microscopic mirrors, one for each pixel in the projected image. The mirrors can tilt up to 10 degrees toward or away from the light source, creating dark or bright pixels.
DMDs have a much higher brightness capability than LCD projectors, making them ideal for larger venues and immersive experiences in the rental and fixed install market. They also feature greater predictability and autofocus 4k projector reliability than other imaging technologies, as DMDs do not suffer from the organic degradation seen in LCDs.
The DMD-based projectors we sell offer true UHD (3840×2160) resolution using either TRP or XPR pixel shifting and deliver up to 75,000 lumens for impressively sharp images that will rival a movie theater experience. They use a single-chip architecture which saves money, reduces the complexity of the design and size of the projector. Light enters a reverse fisheye, passes through a spinning color wheel or a yellow phosphor-wheel to separate it into red and green, then reflects off the DMD.