Contents- Acknowledgement

1. Introduction

2. LCOS micro device

3. LCOS display circuit

4. Types of LCOS televisions

5. Comparision between display technologies

6. LCOS TV –power consumption comparison table

7. Advantages

8. Disadvantages

9. Applications

10. Conclusion

11. References

INTRODUCTION- Liquid crystal on silicon (LCOS) is a "micro-projection" or "micro-display" technology typically applied in projection televisions. It is a reflective technology similar to DLP projectors; however, it uses liquid crystals instead of individual mirrors. In LCoS, liquid crystals are applied directly to the surface of a silicon chipcoated with an aluminized layer, with some type of passivationlayer, which is highly reflective.

LCoS technology can typically produce higher resolution and higher contrast images than standard liquid crystal display and plasma display technologies, which makes it less expensiveto implement in such devices as televisions.

There are two broad categories of LCoS displays: three-panel and single-panel. In three-panel designs, there is one display chip per color, and the images are combined optically. In single-panel designs, one display chip shows the red, green, and blue components in succession with the observer's eyes relied upon to combine the color stream.

Liquid Crystal on Silicon in general is a sophisticated mix of optical and electrical technologies on one chip. The top layer of the chip is liquid crystal material, the bottom layer is an integrated circuit that drives the liquid crystal, and the surface between the layers is highly reflective. The circuit determines how much light passes through the liquid crystal layer, and the reflected light creates an image on a projection screen.

LCOS chips with both 720p and 1080p resolution have been developed for HDTVs. Nearly all LCOS chips in mass production have been used in three-chip systems, with one LCOS chip each for red, green and blue light. Sony’s SXRD and JVC’s HD-ILA

TVs create images this way. While three-chip systems can produce very good HDTV picture.

LCOS MICRO DEVICE-Instead of using liquid crystal between two polarized panels like an LCD, an LCoS micro device has a liquid crystal layer between one transparent thin-film transistor (TFT) and one silicon semiconductor. The semiconductor has a reflective, pixilated surface. The lamp shines light through a polarizing filter and onto the device, and the liquid crystals act like gates or valves, controlling the amount of light that reaches the reflective surface. The more voltage a particular pixel's crystal receives the more light crystal allows to pass. It takes several layers of different materials to do this.

1. Printed circuit board (PCB): carries instructions and electricity from the television to the device.

2. Silicon (a chip or sensor): controls the liquid crystal, generally with one transistor per pixel using data from the television's pixel drivers

3. Reflective coating: reflects light to create a picture

4. Liquid crystal: controls the amount of light that reaches and leaves the reflective coating

5. Alignment layer: keeps the liquid crystals properly aligned so they can direct the light accurately

6. Transparent electrode: completes the circuit with the silicon and the liquid crystal

7. Glass cover: Protects and seals the system LCOS DISPLAY CIRCUIT- It takes several steps to create a picture in anLCoS television. The process includes a high-intensity lamp, aseries of mirrors and micro devices arranged into a cube, a prism and a projection lens. From beginning to end, here's what happens:

1. The lamp creates a beam of white light.

2. The beam passes through a condenser lens that focuses and directs the light. It also passes through a filter that only allows visible light, which helps protect the other components.

3. The white light is separated into red, green and blue lightin one of two ways:

a. The beam passes through a polarizing beam splitter (PBS), which divides the light into three beams, and those beams passthrough filters that add red, green and blue.

b. The beam passes through a series of dichroic mirrors that reflect some wavelengths while allowing the rest of the light to pass through. For example, the dichroic mirror can separatered light from the white light, leaving blue and green, and a second mirror can separate the green light, leaving only blue.

4. The newly created beams of colored light simultaneously come into contact with one of three LCoS micro devices - one each for red, green and blue. We'll look at exactly what happens in the devices in the next section.

5. The reflected light from the micro devices passes through aprism that combines the light.

6. Prism directs the light - which now creates a full-color image - into a projection lens, which magnifies the image and displays it on the screen.

TYPES OF LCOS TELEVISIONS-LCOS provides two types of projection televisions

1. Rear projection TVs2. Front projection TVs

Rear projection TVs (RPTV) has the LCOS projector inside the body of it. The light from the projector is successively reflected from the two mirrors at different positions & oriented at different angles and goes to the screen.

LCOS RPTV’s are available in the market with 720p & 1080p resolution. So it has totally more than 2 million pixels, hence creating higher quality images.

Front projection TVs (FPTV) has a projector in front of the display screen, so the light is directly focused on the screen.

The size of FPTVs is only limited by the brightness; rather than this RPTV’s size depends on their resolution.

The RPTV’s are very lighter in weight as the recent SONY SXRD has only a weight of 200lbs.

COMPARISION BETWEEN DISPLAY TECHNOLOGIES- The existing digital TV technologies have PDP, TFT, DLP, LCOS. Each one have various properties.

“WIDESCREEN” which is a American professional magazine released the technical evaluation report in every performance comparison with CRT, PDP, TFT, DLP,LCOS. Report shows that LCOS leads other technology, and was classified as the best.

The comparison has been done on the basis of performance and

characteristics. ON THE BASIS OF PERFORMANCE

ON THE BASIS OF CHARACTERISTICS

LCOS TV-Power consumption comparision table

LCOS TV in the performance of energy saving is the best. Powerconsumption in LCOS is only 50% that of LCD & 75% that of PDP.

So, it is the most power efficient display technology. ADVANTAGES- There are many advantages of LCOS display technology-

1-Low cost

2- High efficiency

3- Brighter images

4- High resolution

5- Low power consumption

6- Easy to maintenance

7- Fast response time DISADVANTAGES-

Although it has many more advantages, it has few disadvantages also-

1- It is costlier for a common (middle class) people to buy.

2- The three LCOS chips are difficult to align precisely and the miss alignment can cause visible convergence errors between red green and blue particularly along the sides and corners of the screen.

APPLICATIONS- While currently SAMSUNG, PANASONIC, JVC, SONY,RCA are remain in the market. PHILIPS, TOSHIBA and HITACHI areplanning to drop LCOS RPTV’s in the market.

As we know that LCOS front projectors have already a good place in the market; some LCOS RPTV’s are also launched in last few years such as

SONY- SXRD (silicon x-tal reflective display)

Model KDS-Z70XBRS

JVC’S D-ILA (digital direct drive light amplifier)

CONCLUSION- LCOS TV’s are not so cheaper that a common man can afford this; but they are not so expensive as like other display television. In fact it is cheaper in newest display technologies. Its realistic display, high brightness, high resolution like features are making revolution in display technologies.

REFERENCES-

WIKIPEDIA

WWW.SLIDEWORLD.COM

LIQUID CRYSTAL ON SILICON DISPLAYTECHNOLOGY

A SEMINAR REPORT Submitted by GAURAV RAI

in partial fulfillment for the awardof the degree of Bachelor in ELECTRONICS & COMMUNICATION ENGINEERING

COLLEGE OFENGINEERING

INSTITUTE OF ENGINEERING & MANAGEMENT,

MATHURA APRIL 2011 Submitted to Mr. VIKASSHARMA