Interpretation of the principle of rear projection

[Office Partner Information Center] Pursuing efficient, convenient and mobile office is a beautiful goal that modern office people hope, and modern office equipment is a powerful guarantee to achieve this goal. With the rapid development of multimedia technology and digital technology, and daily Office applications, efficient, convenient, and mobile office goals are also becoming a reality. As an important part of digital office equipment, projectors are becoming more intelligent, multi-functional and personalized. However, the projectors that are often mentioned on the market and discussed by our average users are all front projectors, and the rear projectors are rarely noticed compared to the front projectors. To this end, this article here is a brief introduction to the rear projection projection technology, hoping to help everyone better understand the rear projector.

In fact, the rear-projection is relative to the positive vote, so as long as everyone is clear about the concept of positive investment, the concept of rear-projection is naturally clear. Generally speaking, the projector's front projection is that the viewer and the projector are located on the same side of the projection screen, and after the projection illumination emitted from the projector is output to the projection screen, the viewer can see the projection through the light reflected from the projection screen. The result is that the rear projection is the viewer and the projector are located on both sides of the projection screen, the projector is installed at the bottom of the fuselage, and the light projected from the projector is illuminated to the translucent rear projection screen. Part of the light is transmitted through, 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 screen and a reflection system, and a structure is the simplest rear projection system that outputs information from a computer or other input to a projector. The 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 so on.

Like the classification of the front projector, depending on the projection technology, the rear projector can also be divided into DLP (Digital Light Processor) rear projection, CRT (Cathode Ray Tube) rear projection, LCD () rear projection and LCOS (reflective liquid crystal). There are several types of rear projection, etc. The functions and applications of different types of rear projectors may also be different.

DLP (Digital Light Processor) rear-projection technology is relatively powerful, which enables images to be sharper as the window is refreshed. It enhances the black-and-white contrast, draws the boundary lines, and separates the individual colors. The defects in the erase are erased, and finally the display effect is clearer, richer in layers, and uniform in the picture.

Moreover, the brightness of the projector of DLP technology increases with the increase of the resolution of the input image, so that the user can enjoy the bright projection brought by DLP technology in day or night. effect. In addition, DLP rear projection technology also has the remarkable features of more stable projection performance and sharper projection color. Moreover, DLP technology can be more easily miniaturized than CRT and LCD, and the cost is lower, so the development prospect of this rear projection technology is quite good.

CRT (cathode ray tube) rear projection technology has appeared relatively early, and this technology has gradually matured after years of development. The back projector displayed by 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 rear projector is cost-effective. In the current rear projection market is in a dominant position. However, the rear-projection product of this technology also has its fatal flaw, that is, after the projector is used for a long time, the brightness and sharpness of the projection will gradually decrease, because it is illuminated by the phosphor, which easily aging the picture tube; The rear projectors are generally bulky, and many CRT rear projectors weigh more than 50 pounds.

LCD rear projection technology utilizes the very mature liquid crystal photoelectric effect to achieve efficient projection work. This technology changes the transmittance or reflectivity of the liquid crystal cell by the arrangement of liquid crystal molecules under the electric field, thus affecting it. The optical properties produce images with different gray levels and colors; therefore, the rear projector designed by this technology has good color reproduction, brightness and contrast are better than CRT rear projection; since the LCD rear projection is illuminated by the bulb Therefore, it is easy to increase the brightness, as long as the power of the bulb is increased. With the continuous improvement of the technology, the life of the bulb has been greatly improved, and it is close to the life of the ordinary television.

In addition, the LCD rear projector also has many features such as high projection resolution, low price, uniform picture, rich image color and good picture layering; however, the rear projector also has its own shortcomings, which requires good heat dissipation conditions, booting Both warm-up and cooling after shutdown require time to wait, rather than being able to follow the CRT rear projection.

LCOS (Reflective Liquid Crystal) rear projection technology is a new type of reflective micro LCD projection technology, which is a long transistor on a germanium wafer, which is driven by a semiconductor process and then ground on a transistor by a grinding technique. Aluminum is plated as a mirror, and then the liquid crystal photoelectric effect is used to achieve projection.

LCOS rear projection uses reflective projection, so that the projection light utilization efficiency can reach more than 40%, and its biggest advantage is the advantages of high brightness, high resolution and low power consumption. At present, products based on LCOS technology have not yet formed mass production, and only a few manufacturers (such as LG, etc.) have launched several products.

Since LCOS rear projection technology is directly related to image tube (CRT) projection technology, high temperature polycrystalline liquid crystal transparent projection technology, and DMD digital optical processing reflective technology, and these three technologies have matured, LCOS technology will become a projection. The new mainstream of display technology.

Used in conjunction with the rear projector, the rear projection screen is now available on the market with a transparent rear projection screen using holographic technology. This rear projection screen has the characteristics of a holographic image, showing only images from a certain angle of the back projection. While ignoring light from other angles.

Moreover, this transparent rear projection screen has a very bright and clear display effect, even in a place where the ambient light is very bright, and also has a transparent feature, so that the viewer can see through the objects behind the screen, which is suitable for the window presentation of the store. Point of sale promotion, as well as use at airports and other public places.

However, since this technology has just been applied and has not been widely spread and promoted in a wide range, the price of this product is still relatively expensive; so far, only projection screen manufacturers DNP, Da-Lite, etc. have begun to produce this product.

Although the rear projector is a bit strange to our average user, its use is almost the same as that of the front projector. As long as you select and install the rear projection screen according to the type of projector, the user can follow the normal operation. The method is used for rear projection without the need to optically adjust the system, and the entire procedure is as simple as using a normal projector.

Since the rear projection is to make the projector work in the cabinet, the image projected onto the screen is not affected by the ambient light, so the image can be displayed perfectly in a brighter environment. In addition, if you find that the projection space is limited when the rear projector or the screen is installed, you can also use the rear projection screen special mirror system, that is, use the mirror to fold the projection beam once or twice. The specified projection distance is reached in a space where the projection distance is insufficient to ensure the screen size.