Rear-projection television

A rear projection screen is a screen, in which the image is projected through a mirror lens onto a screen.

Technology

The technique was occasionally used in television sets to achieve low-priced larger screen sizes. It is comparable to classic video projectors, but the projector is not in this case in front of a screen, but is built into the unit. For imaging applications is either a tube, DLP or LCD projector used the wrong way radiates the image up. It is located at an angle of about 45 degrees, a trapezoidal plane mirror, which throws the light on the translucent focusing screen. An arranged behind the ground glass Fresnel lens ensures uniform brightness in the peripheral area of the display.

Benefits

Compared with the flat screens, or large-scale projections have rear projection system on key benefits:

• They are often designed almost borderless and therefore can realize almost any size of image surfaces by combining several modules.
• In many applications (eg diagrams of plant control ) the display quality and color fastness is not the main requirement. In these cases, the back-projection technique is more cost effective than comparable TFT solutions already with mid sizes
• Big events: There is no optical path by the side of the spectators who Elaborate positioning and orientation of a projector is not necessary.
• They are insensitive to continuous operation
• Even in very bright ambient light very good readability; no reflections in the image area
• Significantly lower lighting effect on the environment; TFT systems act as an additional light source in the room
• Low power consumption with respect to the display surface
• Very good contrast and excellent black levels.

Disadvantages

• Similar to the CRT goes with the size of the display area is always a certain overall depth along.
• The life of the lamp and also the projector itself is limited. While in many cases a rapid exchange is possible - yet these costs have to be considered when looking at the TCO.
• However, the image quality of modern liquid crystal display is indeed achievable, then at considerably higher cost.

Areas of application

Before the appearance of the liquid crystal display rear projection screens were playing in the consumer area only in high-quality systems for consumer electronics a significant role. In this time it was not otherwise possible to implement with the then prevailing tube devices larger screen sizes than about 85cm. After the appearance of the flat panel rear projection screens initially cost significantly less than plasma TVs of the same size, but this changed quickly. In the consumer electronics therefore rear projection systems now play a subordinate role, and have been almost completely replaced in some areas.

Rear projection systems were, and are, very common in plant control systems, control rooms, traffic control centers or major events have used and there are no alternative.

• Screen
• Projection technology