Video projectors are a useful way to create an image large enough for a classroom full of students to see or to recreate the theatrical moviegoing experience at home. There are several major types of video projectors, each with its own way of producing an image. But all projectors share some of the same basic methods and components.
The image engine is at the heart of every video projector. It produces an image within the projector for display on a screen across the room. The image engine can use one of several different technologies, including LCD (liquid crystal display), DLP (digital light processing) or CRT (cathode ray tube). LCD projectors use liquid crystals arranged as individual pixels to recreate color based on an electronic signal. DLP technology relies on microscopic mirrors to produce an image, while CRT is the older vacuum tube technology that was once the standard for televisions and computer monitors.
A video projector's optics perform the task of transferring the image from the internal image engine onto a screen for viewing. The optics consist of a series of mirrors and prisms, which reflect and split the light into its component colors. An intense lightbulb shines on the completed image via another mirror, and the light then passes through the projector's lens. The lens contains several pieces of curved glass, known as elements. The lens elements bend the light to magnify the image and to control focus.
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A video projector's mainboard is a computer board with chips and electronics for controlling the internal processes. The mainboard regulates fans that cool the bulb, drives the image engine and allows users to control the projector's settings via external controls.
Projectors need a power supply to regulate the current traveling to the mainboard and bulb. Projectors with motorized lenses also use the power supply to drive electric motors that manipulate the lens. A projector's power supply may be contained internally, or take the form of a power adapter that allows for the design of smaller, lighter portable projector models.
Case and Controls
Projectors use plastic or metal cases to protect the delicate internal mechanisms. The case provides a place to mount the electronics and also houses the fans to regulate cooling. Cases must contain vents for cool air intake and hot air venting. Projectors may also contain case-mounter control knobs or switches for varying the image brightness and contrast or moving the lens to control focus and image size. Some projectors also include an infrared sensor for receiving signals from a remote control.