Interpretation of the Principle of Rear Projection Projection

The pursuit of efficiency, convenience, and mobile office is a bright goal that modern office workers hope, and modern office equipment is a powerful guarantee for achieving this goal. With the rapid development of multimedia technology and digital technology, and the application in daily office, it is highly efficient. The goal of convenient, mobile and mobile office is also becoming a reality. As an important part of digital office equipment, projectors tend to be intelligent, multi-functional, and personalized. However, the projectors that are often mentioned in the market and discussed by our general users are all front projectors. Compared with front projectors, back projectors are rarely noticed. For this reason, this article gives a brief introduction to the rear projection technology, hoping to help everyone better understand the rear projector.

In fact, the back shot is relative to the positive vote, so as long as everyone is clear about the concept of positive vote, the concept of the rear projection will naturally be clear. In general, the front projection of the projector is that the audience and the projector are located on the same side of the large screen. If the projection light emitted from the projector is output to the large screen, the light reflected by the audience can be reflected by the large screen. Seeing the result of the projection; in contrast, the rear projection is where the viewer and the projector are located on both sides of the large projection screen. The projector is installed at the bottom of the inside of the fuselage, and the light projected from the projector is translucent. Part of the light is transmitted through the rear projection screen, and the viewer sees the projected result through the transmitted light. A single-screen single-screen projection display system consisting of a projector, a rear projection large screen, a reflection system, and a structure is the simplest rear projection system that outputs information from a computer or other input to a projector and then The rear projector is projected onto a dedicated rear projection screen. This projection scheme can be applied to many occasions such as business presentations, multimedia teaching, conference rooms and the like.

As with the classification of the front projector, depending on the projection technology, the rear projector can also be classified into DLP (digital light processor) rear projection, CRT (cathode ray tube) rear projection, LCD (liquid crystal) rear projection, and LCOS (reflection) There are several types of backlit projectors such as LCD, and different types of back projectors may have different functions and applications. The DLP (Digital Light Processor) rear projection technology is relatively powerful in that it can make the image more clear as the window is refreshed. It enhances the image by enhancing black-and-white contrast, drawing boundary lines, and separating individual colors. The deficiencies in the erased, ultimately showing a more clear, rich layers, the screen display effect. Moreover, the brightness of DLP technology projectors increases with the resolution of the input image, so that users can enjoy the bright projection brought by DLP technology during the day and night. effect. In addition, DLP rear projection technology also has the outstanding features of more stable projection performance and sharper projection colors. Moreover, DLP technology can be more compact and more cost-effective than CRTs and LCDs, so this kind of rear projection technology has a bright future.

CRT (Cathode Ray Tube) rear projection technology is relatively early, and this technology has gradually matured after years of development. The back projector designed by using this technology displays rich colors, good color reproduction, and rich geometric distortion adjustment capability. Due to the large scale of production of this technology, the CRT back projector is cost-effective. In the current rear projection market is in a dominant position. However, the technology's rear-projection product also has its fatal flaw, that is, after the projector is used for a long time, the projection brightness and sharpness will gradually decrease, because it is rely on the fluorescent powder to light, it is easy to make the kinescope aging; In addition, the technology Rear projectors are generally large in size, and many CRT rear projectors weigh more than 50 pounds. LCD (liquid crystal) rear projection technology utilizes a very mature liquid crystal photoelectric effect to achieve high-efficiency projection work. This technology changes the alignment of liquid crystal molecules under the influence of an electric field, and affects the transmittance or reflectivity of the liquid crystal cell. It affects its optical properties and produces images with different gray levels and colors; therefore, the back projector designed by this technology has good color reproduction, brightness and contrast are better than CRT rear projection; LCD display back Because the light bulb shines, it is easy to increase the brightness, as long as the power of the bulb can be increased. With the continuous improvement of technology, the lamp life has been greatly improved, and it has approached the life of ordinary TV. In addition, the LCD display back projector also has many features such as high projection resolution, low price, uniform image, rich colors, and good image quality; however, the back projector also has its own disadvantages, and it needs good heat dissipation conditions. Preheating after power-on and cooling after power off all take time to wait, and you can't go away like a CRT rear projection.

LCOS (reflective liquid crystal) rear projection technology is a new type of reflective micro LCD projection technology. It uses a long transistor on a silicon wafer. It uses a semiconductor process to fabricate a drive panel, and then polishes the surface of the transistor by grinding. It is coated with aluminum as a mirror, and then uses the reflective liquid crystal photoelectric effect to achieve projection; LCOS rear projection using reflective projection, so that the projection light utilization efficiency of up to 40%, and its greatest advantage is high brightness, high Resolution, low power consumption advantages. At present, products based on LCOS technology have not yet been mass-produced. Only a few manufacturers (such as LG and Skyworth) have introduced several products. Since LCOS rear projection technology is directly related to CRT projection technology, high-temperature polycrystalline silicon liquid crystal transmission projection technology, and DMD digital optical processing reflection technology, these three technologies have matured, and LCOS technology will become a projection. The new mainstream of display technology.

The back projector used together with the back projector is a large screen. Now on the market there is a transparent rear projection large screen using holographic technology. This large rear projection screen has the characteristics of a holographic image. Angle the image while ignoring other angles of light. Moreover, this transparent rear-projection large screen has a very bright and clear display effect, even in a place where the ambient light is bright, and also has a transparent feature, so that the viewer can see through the objects behind the large screen, suitable for the shop window Demonstration, point-of-sale promotion, and use at airports and other public places. However, as this technology has just been applied, it has not been popularized and promoted on a large scale, so the price of the product is still relatively expensive; so far, only the projection large screen manufacturers DNP, Da-Lite and other began to produce this product.

Although the rear projector is somewhat strange to our average user, its use is almost the same as that of the front projector. As long as everyone selects and installs a large rear screen according to the type of the projector, the user can follow the ordinary The method of operation for rear projection without optical adjustment of the system, the entire operation steps as simple as using a common projector. Since the rear projector projects the projector in the box, the image projected on the big screen is not affected by the ambient light, so the image can be perfectly displayed in a bright environment.

In addition, if a projector with a rear projector or a large screen is installed and the space of the projection space is found to be limited, a large-screen special reflector system for rear projection can also be used, that is, the projection beam can be folded back once or twice with a mirror. At the same time, the projected distance is displayed within the space where the projection distance is insufficient to ensure the screen size.