PROJECTION SYSTEMS AND INTERFACING

• Presented by

VARUN K

varunkpa@gmail.com

PROJECTION SYSTEM

Definition:

• A Projection system is an optical device that projects an image or

moving images onto a surface or a projection screen.

First idea of projecting an image came in 1420.

The first projector called the Magic Lantern was developed in 1650

Types:

1.CRT

2.LCD

3.DLP

CRT PROJECTOR

• projector which cathode ray tube as the image generating element. Image is focused and enlarged to a screen using lens kept in front of CRT

• Usage of 3 CRT system-lenses to obtain color images.

• Specifications

A. CRT size

B. Scan rates & HDTV

C. Max.Resolution

D. Input

E. Focus

F. Peak lumens

SPECIFICATIONS

• Peak lumens: Amount of energy that coming from CRT.

Entry level projector:600-800 lumens

intermediate level projector:1000-1200 Lumens

high performance CRT:1200+ Lumens

• CRT size: Measurement is taken from corner to corner

on the front of the tube face.std size:7”,8”9”.

• Scan rate &HDTV: Ability to display HD videos depends scanning ability. Expressed in no of scanning lines.

HDTV: Requires a scanning rate of 33.75 KHz and 50Mhz BW due to line doubling feature.

SPECIFICATIONS(Cont..)HDTV:NTSC-standard contains 525 lines that makes up the TV

image.(Scanning rate 15.15 KHz).HDTV introduces additional scanning between line. -31.5Khz(520p).line triplers,Qudraplers:48k,64kHigh grade projectors(CAD):135 kHz

Max Resolution: Maximum resolution that a projector can accept-depends tube size& Quality of internal circuitry.High resolution: Individual scan lines are close enough-Over resolution –Overlapping softening. Low resolution: scan lines are visiblefixed size-Proper resolution=> 7” 480p ,8” 720p. 9” 960p

SPECIFICATIONS(Cont..)• Input: Different video standard signal that we can give

I. Composite video:

lowest quality but common.

limited to 480p

HD impossible

2. S Video:

Limited to 480p

B,W, Colors are send different medium

25% picture details more than Composite.

3. Component/YPBR

480-1080support

videos from HD cable/satliite box 720p/1080p from HD DVD

LCD PROJECTOR

• Components: LCD panels

Prism

filters to create image on screen

• The lamp gives white light that passes through a polarizing filter .Polarizer accepts light travelling in same plane. Other lights are blocked.

• Then Light passes through series of dichroic mirrors .separation of light in to RGB

• 3 colors are sent to separate LCD panel each is capable of controlling one color. From this light is combined using prism and send out to the LCD projector.

LCD

SPECIFICATIONS• Brightness: It is the quality of the state being bright.

Unit:Lumens• Contrast Ratio: Ratio of Luminance of brightest color to that

of darkest color that the system is capable of producing.• Resolution: Resolving capacity. People who needs Wild screen

usually takes 16:9 format.3 standard resolution. 1024*576,854*480,1280*720.

• Projector with resolution854*480 ,input=480p works well.Projector with resolution1024*576 ,input=480p will not works well. Projector has to distribute 480line information in 576 lines=> image become softer. So there should be compatibility

SPECIFICATIONS(CONTD…)

• Uniformity: Consistency of brightness over the entire image.

90%=>It is projecting a pure white image on the entire screen, there will be no more than 10% variation in intensity

across the entire screen. %uniformity α accuracy.

• Image size, Throw distance: Max and min size of the image that the projector is capable of projecting. The maximum and minimum distance with in which projector will focus.

• Zoom Ratio: This refers to the amount of difference between the smallest image size and the largest, without moving the projector. A typical projector has a zoom ratio of 1:1.3. This means that if the smallest image for a given screen distance is 10 feet, the largest will be 13 feet.

SPECIFICATIONS(Cont..)

• Throw Ratio: This is tied to the Zoom Ratio. It tells you the minimum and maximum distance the projector can be from a given size screen. For example, a projector with a Throw ratio of 1.7 - 2.2 can fill a 10 foot screen when placed between 17 feet and 22 feet from the screen.

• Scanning Frequency: Different computer outputs have different vertical and horizontal scanning frequencies. For example VGA (640 x 480 resolution) can be as low as 32 Hz Horizontal and 60 Hz Vertical, and SXGA can be up to 81 Hz Horizontal and 76 Hz Vertical.

SPECIFICATIONS(Cont..)

• dB Rating: This refers to the amount of fan noise the projector produces. A lower number means that the projector is quieter. Since every 3 dB is a doubling of sound, a projector with a rating of 36 dB is twice as noisy as one with a rating of 33 dB.

DLP PROJECTION SYSTEM

• Based DLP technology introduced in 1997.

• DLP technology: Introduced by Dr Hornbeck of TI

• Used in DLP front end projectors, DLP rear projection TV sets .

• DMMD: Image is created by microscopically using small mirrors in matrix on semiconductor chip called digital micrometer device

• 16um thickness-each mirror represents each pixel.

• No of mirrors corresponds to resolution.

• 2 types :Single chip DLP

Three chip DLP

DIGITAL MICROMETER DEVICE

INTRODUCTION-DMD• Optical semiconductor which is the core of the DLP

technology

• Several hundred microscopic mirrors arranged in a rectangular array, each mirror is one pixel.

• Aluminum alloy mirrors, silicon based electrostatic drives, silicon microelectronic

• 1280*1042 DMD

• Central reflective sections have 1310720 tiny mirrors, Over this glass is sealed

• Mirror size=16um.

DMD structure

• Integrated MEMS which is fabricated on cmos RAM cell.

• Mirror(Alumina)-connected to underlying yoke-yoke connected to hinges supported by post that is attached to underlying structure.(Memory cell beneath the post).

• Electrostatic field between memory cell and yoke generates electrostatic torque.

• Torque produces mirror rotation in +/-

DMD

Operation of single mirror

• The mirror is on the yoke that can rotate on two torsion hinges.

• Yoke connected to yoke addressing electrode.

• Which electrode is energized depends up on thee status of the memory cell beneath it.

• ‘1’in the cell-mirror moves +10 deg.

• ‘0’in the cell-mirror moves -10 deg.

• Each cell is made of SRAM

SRAM cell write ‘1’

SRAM

• Bit lines charged to 2.5v

• Choose w=1;

• Apply b=1 and b’=0;

• Vb=+5 and Vb’=0

• Vy rises to +5v and Vy fall to 0

• Recharged to +2.5 v

How to control mirror movement

• Wheel rotation speed:60Hz

60rev/sec 180color changes/sec

• 1/180=5.56 msec to pass light source.

• Each mirror should be capable of moving less than 5.56

• Practical:20 usec

• So for any given color mirror of any pixel can move=

5.56*0.001/2usec=278 times

• 8 bits 256 pos

How intensity is projected• Chip receives the video signal & separates to RGB.

• Each color component intensity is translated to a value between 0 & and stored mirror control byte.

• Initial reset-latch bias current is turned on

‘1’ mirror deflect towards projection lens (+10)

‘ 0’mirror deflect towards projection lens (-10)

No light, again neutral position ,Repeated for all bits

• To process single video frame each mirror will move 8 times

Brightest pixel Each at +ve angle

darkest pixel Each at -ve angle

• Remaining level combination of these orientations

• Cycle time of DMD , integration time of human eye compatibility

How intensity is projected

NEC NP-V300WG DLP

NEC NP-V300WG DLP

ADVANTAGES

• Sealed imaging chip: Most DLP projectors have sealed DLP chips that eliminate the possibility of a dust particle alighting on the imaging plane, which could create a dust spot on the projected image.

• Filter-free. DLP projectors that have sealed DLP chips can operate without air filters. Thus maintenance is reduced since there is no need to periodically clean or replace filters.

• No image persistence. If one displays a static image for an extended period of time, an LCD projector with organic LCD panels may have a tendency to retain a subtle ghost of that image even after the subject matter is switched to another image. This does not occur on a DLP projector.

VGA INTERFACE• VGA: Display hardware introduced

by IBM.Amplitude modulated computer display standard.

• A Video Graphics Array (VGA) connector is a three-row 15-pin DE-15 connector.

• DE-15 is also conventionally called RGB connector

• VGA connectors and cables carry analog component RGBHV (red, green, blue, horizontal sync, vertical sync) video signals, and VESA Display Data Channel (VESA DDC) data.

• The VGA interface is not engineered to be hot pluggable.although in practice this can be done and usually does not cause damage to the hardware or other problems.

HDMI INTERFACE• HDMI (High-Definition

Multimedia Interface)

• audio/video interface for transferring uncompressed video data and compressed or uncompressed digital audio data from an HDMI-compliant source device.

• HDMI is a digital replacement for analog video standards

• HDMI implements the EIA/CEA-861 standards, which define video formats and waveforms, transport of compressed, uncompressed, and LPCM audio, auxiliary data.

HDMI(CONTD..)

• Several versions of HDMI have been developed and deployed since initial release of the technology but all use the same cable and connector.

• newer versions have optional advanced features such as 3D, Ethernet data connection.

• The maximum pixel clock rate for HDMI 1.0 was 165 MHz, which was sufficient to allow 1080p and WUXGA (1920×1200)