SEMINAR ON DIGITAL LIGHT PROCESSING

1. SEMINAR ON DIGITAL LIGHT PROCESSING PRESENTED BY SAI NATH

2. INTRODUCTION • Trademark owned by Texas Instruments, representing a technology used in video projectors. • Developed in 1987 by Dr. Larry Hornbeck of Texas Instruments. • DLP is also one of the leading technologies used in digital cinema projection. • It is named for its ability to process light digitally with the aid of an optical semiconductor called a Digital micromirror Device an micro electro mechanical systems (MEMS) device. • The DMD microchip is a fast, reflective digital light switch. • When combined with image processing, memory, alight source, and optics the DLP system is capable of projecting large, bright, high contrast colour images .

3. WHAT IS DLP TECHNOLOGY ? • DLP devices come in either one or three-chip models. • One-chip DLP systems use a projection lamp to pass white light through a color wheel that sends red-green-blue colors to the DMD chip in a sequential order to create an image on screen. • Three-chip DLP systems use a projection lamp to send white light through a prism, which creates separate red, green, and blue light beams. Each beam is sent to their respective red, green and blue DMD chip to process the image for display on screen. • One-chip models are said to produce a display of over 16-million colors. Three-chip models can produce a display of over 35-trillion colors.

4. COMPONENTS OF DLP • A DLP based projector system has the following components: • DMD Chip (Digital Micromirror Device) • A light source • A color filter system • A cooling system • Illumination and projection optics

5. THE DMD CHIP • Image is created by microscopically small mirrors laid out in a matrix on a semiconductor chip, known as a Digital micromirror Device(DMD). • Matrix of micromirrors1024 X768 for example. • Size of the mirrors: 16 X 16 um • Each mirror represents one or more pixels in the projected image.

6. THE DMD ARCHITECTURE

7. THE DMD CHIP • To move the mirrors, the state is first loaded into an SRAM cell located beneath each pixel. • Once all the SRAM cells have been loaded, the bias voltage is removed, allowing the charges from the SRAM cell to prevail, moving the mirror. • When the bias is restored, the mirror is once again held in position, and the next required movement can be loaded into the memory cell. • The bias system is used to reduces the voltage levels required to address the pixels such that they can be driven directly from the SRAM cell.

8. THE DMD CHIP • When the mirror rotates to its on state (+10 degrees), light from a projection source is directed into the pupil of a projection lens and the pixel appears bright on a projection screen. • When the mirror rotates to its off state (-10 degrees), light is directed out of the pupil of the projection lens and the pixel appears dark. Thus, the optical switching function is simply the rapid directing of light into or out of the pupil of the projection lens.

9. HOW DLP SYSTEM WORKS? • Depending on the application, a DLP system will accept either a digital or an analogue signal. • Any interlaced video signal is converted into an entire picture frame video signal through interpolative processing. • From here, the signal goes through DLP video processing and becomes progressive red, green and blue (RGB) data. • The progressive RGB data is then formatted into entire binary bit planes of data. • Once the video or graphic signal is in a digital format, it is sent to the DMD. Each pixel of information is mapped directly to its own mirror in a 1:1 ratio, giving exact, digital control.

10. HOW DLP SYSTEM WORKS ?

11. THE ADDRESS SEQUECE • The DMD accepts electrical words representing gray levels of brightness at its input and outputs optical words. The light modulation or switching technique is called binary pulse width modulation. An 8-bit word is input to each digital light switch of the DMD yielding a potential of 28 or 256 gray levels. • The address sequence to be performed once each bit time can be summarized as follows:

12. GRAYSCALE AND COLOUR OPERATION • Grayscale is achieved by binary pulse width modulation of the incident light. • Color is achieved by using color filters, either stationary or rotating, in combination with one, two, or three DMD chips. • The DMD light switch is able to turn light on and off rapidly by the beam-steering action of the mirror. • The optical switching time for the DMD light switch is ~2 us. • The technique for producing the sensation of grayscale to the observer's eye is called binary pulse width modulation. • The DMD accepts electrical words representing gray levels of brightness at its input and outputs optical words, which are interpreted by the eye of the observer as analog brightness levels.

13. The details of the binary pulse width modulation (PWM) technique are illustrated in Figure. • For simplicity, the PWM technique is illustrated for a 4-bit word (2 4 or 16 gray levels). • Each bit in the word represents time duration for light to be on or off (1 or 0). • The time durations have relative values of Here ‘1’ being LSB and ‘8’ being MSB

14. The video field time is divided into four time durations of 1/15, 2/15, 4/15, and 8/15 of the video field time. • The possible gray levels produced by all combinations of bits in the 4-bit word are 24 or 16 equally spaced gray levels (0, 1/15, 2/15 . . . 15/15). • Current DLP systems are either 24-bit color (8 bits or 256 gray levels per primary color) or 30-bit color (10 bits or 1024 gray levels per primary color).

15. ELECTRONIC OPERATION • The DMD pixel is inherently digital because of the way it is electronically driven. • Multiple data inputs and demultiplexers (1:16) are provided to match the frequency capability of the on-chip CMOS with the required video data rates. • During each bit time, while the mirrors of the array are modulating light, the underlying memory array is refreshed or updated for the next bit time. • Once the memory array has been updated, all the mirrors in the array are released simultaneously and allowed to move to their new address states.

16. LIGHT SOURCE • In DLP projectors high-power LEDs or LASERs are used as a source of illumination. LED-BASED DLPs: • Advantages of LED illumination include instant-on operation and improved color, with increased color saturation. • Ordinary LED technology does not produce the intensity and high lumen output characteristics required to replace arc lamps. The special patented LEDs used in all of the Samsung DLP TVs are PhlatLight LEDs, designed and manufactured by US based Luminus Devices. A single RGB PhlatLight LED chipset illuminates these projection TVs. LASER-BASED DLPs: • The first commercially-available LASER-based DLP HDTV was the Mitsubishi L65-A90 LASERVUE in 2008, which also eliminated the use of a color wheel. Three separate color LASERs illuminate the DMD in these projection TVs, producing a richer, more vibrant color palette than other methods.

17. SINGLE CHIP PROJECTORS • White light is focused down onto a spinning color wheel system. • The wheel spins illuminating the DMD sequentially with RGB light. • At the same time RGB video signal is being sent to the DMD mirror-pixels. • The mirrors are turned on depending on how much of each color is needed. • The eye integrates the sequential images and a full color image is seen.

18. THREE CHIP PROJECTORS • A prism splits light from the lamp, and each primary color of light is then routed to its own DLP chip, then recombined and routed out through the lens. • Found in higher-end home theatre projectors, large venue projectors.

19. THREE CHIP PROJECTORS • For proper operation of the DMD light switch, this light must be directed at 20 degrees relative to the normal of the DMD chip . • To accomplish this in a method that eliminates mechanical interference between the illuminating and projecting optics, a total internal reflection (TIR) prism is interposed between the projection lens and the DMD color-splitting/-combining prisms. • The color-splitting/-combining prisms use dichroic interference filters deposited on their surfaces to split the light by reflection and transmission into red, green, and blue components.

20. THREE CHIP PROJECTORS

21. ADVANTAGE OF DLP • Brighter: DLP projectors are among the brightest available because DLP technology brings more light from lamp to screen, resulting in more effective presentations—even when ambient light is difficult to control. • Sharper: DLP projection’s unique reflective technology comes closest to producing the exact mirror image of an incoming video or graphic signal, resulting in projection that’s seamless at any resolution. • Versatile: DLP technology allows projectors to be small and light, often weighing as little as 1 kg—making them versatile enough for use in conference rooms, living rooms and classrooms. • More reliable: Display systems using DLP technology are able to recreate their incoming source material with each projection, ensuring a full-impact projection experience that will not fade over time. DISADVANTAGE OF DLP

22. FUTURE USE OF DLP • High definition image creation • 3-D visual displays • Holographic storage • Microscopes • Medical Imaging THESE TECHNOLOGIES ARE IN THE DEVELOPMENTAL STATE…..