What is the difference between dlp and led?

DLP is the abbreviation of "Digital Light Processing", which means digital light processing. That is to say, this technology must first digitally process the image signal and then project the light. It is a technology based on the digital micromirror device - DMD (Digital Micromirror Device) developed by TI (Texas Instruments) to complete the display of visual digital information. To be more specific, DLP projection technology uses a digital micromirror chip (DMD) as the main key processing element to realize the digital optical processing process. The principle is to pass the cold light source emitted by the UHP bulb through the condensing lens, and homogenize the light through Rod. The processed light passes through a color wheel (Color Wheel) to divide the light into RGB three colors (or RGBW and other more colors). ), and then the color is projected on the DMD chip through the lens, and finally reflected through the projection lens and imaged on the projection screen.

[Edit this paragraph] Imaging principle

The light source is refracted on the DMD chip after passing through the color wheel. The DMD chip emits light to the projection screen after receiving the control signal from the control board. . The DMD chip looks like just a small mirror, enclosed in a closed space composed of metal and glass. In fact, this mirror is composed of hundreds of thousands or even millions of micromirrors. Taking the XGA resolution DMD chip as an example, there are 1024×768=786432 micromirror units in an area of ??1cm wide and 1.4cm long. Each micromirror represents a pixel, and the image is composed of these pixels. Since the pixels and chips themselves are quite small, the industry also calls these products using micro-display devices microdisplays.

[Edit this paragraph] Origin

In 1991, the 300,000-pixel LCD projector was launched. In 1996, LCD projection has rapidly developed into VGA and even SVGA data projection and home applications. It has reached the stage of cinema projection, but due to technical bottlenecks, it is difficult to break through the brightness and contrast. In this context, it is natural for DLP projection technology to enter the stage of history.

The core technology of DLP is the DMD chip, which was invented by Dr. Larry Hornback of the United States in 1977. At the beginning, it was mainly to develop the imaging mechanism of printing technology. It first used analog technology to develop micro-mechanical control. In 1981, it switched to digital control technology and officially named it Digital Micro-mirror Devices. It began to be divided into printing technology and digital imaging. Research and development in two directions. In 1991, Texas Instruments decided to separate the development of digital imaging into a business unit, and developed the first digital imaging product in 1996. In 1997, it officially terminated the research and development of printing technology and devoted all its efforts to the research and development of digital images.

[Edit this paragraph] ⒈The working process of DLP

DMD device is the basis of DLP. A DMD can be simply described as a semiconductor optical switch, with 500,000 to 1.3 million microlenses gathered together on a CMOS silicon substrate. A microlens represents a pixel, and the conversion rate is 1,000 times/second, or faster. The size of each lens is 14μm×14μm (or 16μm×16μm). In order to facilitate the adjustment of its direction and angle, there is a hinge-like rotating device below it. The rotation of the microlens is controlled by digital drive signals from CMOS RAM. When a digital signal is written to the SRAM, static electricity activates the address electrodes, lens and yoke plate (YOKE) to cause the hinge mechanism to rotate. Once the corresponding signal is received, the lens tilts 10°, thereby changing the reflection direction of the incident light. The microlens in the projected state is shown as "on" and tilted by +12° with the digital signal from the SRAM; if the microlens is in the non-projected state, it is shown as "off" and tilted by -12°. At the same time, the incident light reflected out in the "on" state projects the image onto the screen through the projection lens; while the incident light reflected on the microlens in the "off" state is absorbed by the light absorber. In short, the working principle of DMD is to use the micromirror device to reflect the required light, and at the same time absorb the unnecessary light through the light absorber to achieve image projection, and its illumination direction is controlled by the angle of the microlens with the help of electrostatic action. to achieve.

Each lens on the DMD array is electrostatically tilted into an on or off state by addressing the memory cells under each lens with a binary planar signal. The technique that determines which direction each lens tilts for how long is called pulse-width modulation (PWM). The lens can switch on and off more than 1,000 times a second, at which point DLP becomes a simple optical system. After passing through the condenser lens and color filter system, the light from the projection lamp is directly illuminated on the DMD. When the lenses are in the open position, they reflect light through the projection lens onto the screen to form a digital square pixel projection image. When the DMD base plate, projection lamp, color wheel and projection lens work together, these flipping mirrors work together to reflect the image onto a presentation wall, movie screen or television screen.

[Edit this paragraph] Advantages of DMD imaging

DMD can provide 16.7 million colors and 256 grayscale levels, ensuring that the moving images that DLP projectors can project are colorful Delicate, natural and lifelike.

DMD can have a built-in array of up to 2048×1152, and each element can produce approximately 2.3 million mirrors. This kind of DMD has the ability to make a true high-definition TV.

⑴Erase defects in the image

The extraordinary fast switching speed of DMD micromirror devices is combined with an accurate image color and grayscale reproduction technology of dual pulse width modulation , allowing the image to become clearer as the window refreshes, erasing imperfections in the image by enhancing contrast, delineating boundary lines, and isolating individual colors.

⑵Avoid the "Screen Door" Effect

In many LCD projection images, we will see that when the size of an image increases, the gaps in the LCD image will become larger. This will not happen in DLP projectors. The size and shape of the DMD mirror determines everything. 90% of the area of ??each lens dynamically reflects light to produce a projected image that appears seamless because one lens is so close to the other. DMD lenses are tiny, each side is 16 microns long, and the gap between adjacent lenses is less than 1 micron. The lenses are square, so each lens shows more than the actual image. In addition, the size and spacing remain consistent as the resolution increases, so the image always maintains high definition regardless of the resolution.

⑶Coexisting with light

Many viewers often want to maintain brightness or open the curtains when watching projections. Compared with traditional projectors, DLP projectors shine more light into the On the screen, this also depends on the technical characteristics of DLP itself. The DMD's highly reflective surface maximizes the use of the projector's light source by eliminating obstacles in the light path and reflecting more light onto the screen. DLP technology reflects the image based on the content of the image. The DLP light source has two working methods, either hitting the screen through a lens, or directly entering a light absorber. Even more advantageous is that the brightness of projectors based on DLP technology increases as the resolution increases. In the case of higher resolutions such as XGA and SXGA, DMD provides more reflective area, so that the brightness of the light can be used more effectively.

⑶ Images are more realistic and natural

DLP does more than simply project images, it also copies them. In its processing, the source image is first digitized into a grayscale image with 8 to 10 bits per color. These binary images are then fed into the DMD, where they are combined with carefully filtered colored light from the light source. These images leave the DMD and are imaged onto the screen, maintaining all the brilliance and subtlety of the source image. DLP's unique color filtering process controls the color purity of the projected image. This technology's digital control enables unlimited color reproduction and ensures a lifelike reproduction of the original image. With the emergence of other display technologies and photography technologies, DLP makes those inanimate images have realistic colors. Digital color reproduction ensures that the image resembles the real thing, without the shiny spots or washout typical of other projectors.

⑷ High reliability

DMD not only passed all standard semiconductor qualification tests, the system manufacturing is very strict and needs to go through a series of tests. All components are selected and confirmed to be reliable before they can be used. The digital electronics section drives the DMD and has a proven lifespan of over 100,000 hours in a simulated operating environment. Tests have proven that the DMD can operate trouble-free for more than 1,700 trillion cycles, which is equivalent to the actual use of the projector for more than 1995 years. Other test results show that the DMD is fault-free for more than 110,000 power cycles and 11,000 temperature cycles to ensure more than 30 years of reliable operation in demanding applications.

⑸ More convenient mobility

According to general application requirements, a single-chip DMD can achieve the unification of size, weight and brightness. Currently, most household or Commercial DLP projectors all use a single-chip structure, while more advanced three-chip structures are generally only used in digital cinemas or high-end fields. Therefore, users can get a smaller, brighter, easier to carry and enough to provide excellent image quality. System DLP technology is an all-digital infrastructure with minimal signal noise.

[Edit this paragraph] ⒊Classification of DLP systems

⑴Single-chip DLP system

In a single DMD projection system, a color wheel is needed to generate Full color projected image. The color wheel consists of a red, green and blue filter system, which rotates at a frequency of 60Hz. In this structure, DLP works in sequential color mode. The input signal is converted into RGB data, and the data is written to the SRAM of the DMD sequentially. The white light source is focused on the color wheel through the focusing lens, and the light passing through the color wheel is then imaged on the surface of the DMD. When the color wheel rotates, red, green, and blue light are sequentially emitted on the DMD.

The color wheel and video image work sequentially, so when red light hits the DMD, the lens tilts to "on" at the position and intensity where the red information should be displayed. The same goes for green and blue light and video signals. The human visual system concentrates red, green, and blue information and sees a full-color image. Through the projection lens, the image formed on the DMD surface can be projected onto a large screen.

⑵Double-chip DLP system

This system takes advantage of the lack of red light of metal halide lamps. Instead of red, green, and blue filters, the color wheel uses two auxiliary colors, magenta and yellow. The magenta segment of the color wheel allows red and blue light to pass through, while the yellow segment allows red and green light to pass through. The result is that red light passes through all the time, and blue and green light each spend essentially half the time in the magenta-yellow color wheel's alternating rotation. Once through the color wheel, the light strikes directly onto a dichroic dichroic prism system. Continuous red light is separated and directed to a DMD specifically designed to process red and red video signals. Sequential blue and green light is projected onto another DMD specifically designed to handle alternating colors. This DMD consists of green and blue. color video signal driver.

⑶Three-chip DLP system

Another method is to divide the white light into three primary colors through a prism system. This method uses three DMDs, one DMD corresponding to one primary color. The main reason for using a three-chip DLP projection system is to increase brightness. With three DMDs, light from each primary color can be projected directly and continuously onto its own DMD. The result is more light reaching the screen, giving a brighter projected image. This highly efficient three-chip projection system is used in very large screen and high-brightness applications.

⒋Potential problems of DLP

There is only one weakness of DLP projectors that people often mention, which is the "rainbow effect". The specific manifestation is that the colors are simply separated into obvious red and green. The three single colors of blue and blue look like a rainbow after the rain. This is caused by using a rotating color wheel to modulate the color of the image, and because some people's visual systems are particularly sensitive and can detect the process of converting one color to another, rather than relying on vision like most people. The persistence phenomenon mixes several solid colors into new colors. In addition to some users being able to separate colors, others may experience eye swelling and headaches due to rapid changes in color. LCD projectors and three-chip DLP projectors do not have this phenomenon. Their physical structure is formed by superimposing three fixed red, green, and blue images.

This problem has different effects on different people. Some people can see the rainbow effect, which can be so severe that the picture is almost unreadable. Some people only see traces of rainbows occasionally, but not enough to appreciate the picture. For the latter, this shortcoming of DLP has no practical impact. Even more fortunately, most people can neither see traces of rainbows nor be confused by eye swelling or headaches. Please think that if everyone can see the rainbow effect on DLP projectors, DLP projectors will lose their chance of existence.

But the rainbow effect is always a problem anyway. Texas Instruments and projector manufacturers using DLP technology are still trying to solve this problem. The color wheel of the first generation DLP projector rotated 60 times per second, which is equivalent to a frame rate of 60Hz, or 3600 revolutions per minute. In the color wheel, red, green, and blue pixels each have a segment, so each color is refreshed 60 times per second. This first generation product is called the "1X" speed.

There are still a few people who can see the rainbow effect in the first-generation product. The color wheel speed of the improved second-generation product has increased to 2X, that is, 120Hz and 7200RPM, and even fewer people can see the rainbow effect. .

Today, many DLP projectors designed specifically for the home theater market use a six-segment color wheel. Red, green, and blue appear twice in one rotation of the color wheel, and the color wheel rotates at 120Hz or 7200RPM, so In business, it is called 4X speed. As the color refresh speed continues to increase, fewer and fewer people can see the rainbow effect. But so far, Rainbow Guilt is still a problem for a small number of viewers.

4. Application of DLP technology

DLP technology is an original solution that uses optical semiconductors to produce digital multi-light display. It is an extremely reliable all-digital display technology that provides the best image effects in various products such as large-screen digital TVs, corporate/home/professional conference projectors, and digital cameras (DLP Cinema). At the same time, this solution is also a fully mature independent technology used by many electronics companies around the world. Since 1996, more than 5 million systems have been supplied to more than 75 manufacturers.

DLP technology has been widely used to meet various demands for excellent visual image quality. It is also the most versatile display technology on the market. It's the only display technology capable of supporting both the world's smallest projectors (under 2-lbs) and the largest movie screens (up to 75 feet tall). This technology enables images to achieve extremely high fidelity, giving clear, bright, and lifelike colors.

[Edit this paragraph] Technical characteristics of DLP

Technical advantages:

The advantage of DLP display panels is that they have extremely fast response time.

You can switch individual pixels on and off many times while displaying a frame. It uses a display panel to produce true-color images through field-sequential filtering. The steps are as follows: First, green light shines on the panel, and a mechanical mirror adjusts to display the image's green pixel data. The mirror then adjusts again for the red and blue pixel data of the image. (Some projectors increase the brightness of the image and achieve bright tones by using a fourth white area.) All of this happens so quickly that the human eye cannot detect it. Images of different colors that appear sequentially are reassembled in the brain to form a complete, full-color image.

For a high-quality projection system, 3 DLP display panels can be used. Each panel was individually colored red, green and blue, and the image was reassembled into a single true-color image. This technology has been used in some large-scale projection equipment in digital cinemas. DLP display panels have high resolution and are very reliable. Their contrast ratio is approximately twice that of polycrystalline LCD projectors, making them more effective in bright rooms.

Technical Disadvantages:

There are few problems with DLP itself, but they are more expensive than polysilicon panels. When you look carefully at moving dots on the screen (especially white dots on a black background), you'll notice that the image with field-by-field filtering will break down into different colors. When using a projector, the motor will make a certain amount of noise when it rotates the color wheel. A new solid-state color filter system now on the market can better solve this problem.