SUBMITTED BY:

KIRAN JOSHY

S7ECA

NO:44

GUIDED BY:P.M ManoshSenior Lecturer

OVERVIEW• OVERVIEW OF PORTABLE DISPLAYS

• STRUCTURE

• WHAT IS IMOD?

• HOW IT WORKS

• COLOR GENERATION

• MEMORY

• HYSTERISIS LOOP

• IMOD ADDRESSING

• ADVANTAGES

• APPLICATIONS

OVERVIEW OF PORTABLE DISPLAYS

• Emissive/Transmissive Displays

• Reflective Displays (Continuous refresh type)

• Reflective Displays (Bistable type)

• Transflective Displays

Emissive/Transmissive Displays:

• Have two transmissive substrates.

• Liquid crystal material resides in between them.

• Backlight is placed underneath one of the substrates .

• Disadvantages-Large power consumption

Continuous refreshing

• Example: LCD, OLED

Reflective Displays (Continuous refresh type):

• One reflective and the other transmissive.

• LC material resides over the top of reflective substrate.

• Since there is no backlight in reflective displays, they consume substantially less power than emissive displays.

• The majority of these types of displays must constantly be refreshed or the displayed image will be lost.

Reflective Displays (Bistable type):

• A bistable display is capable of maintaining one of two states (on or off) without any

external influence such as an electric field.

• Image can be maintained for a long time.

• Example: EPD and mirasol displays.

• No refreshing required.

• No Back light.

• Hence consume little power.

Transflective Displays

• Transflective displays utilizes the property of both transmissive and reflective displays.

• In low light situations, the device operates as a transmissive display, employing the backlight.

• In high ambient light conditions, the backlight turns off and the display functions as a reflective display.

WHAT IS AN IMOD ?

• Interferometric Modulation(IMOD) is a new display technology that produces fantastic colors by exploiting the physical effect of interference of light while using little of the limited battery power.

• Main advantages-Paper like readability

Low power consumption.

STRUCTURE.

Figure 1

HOW IT WORKS?

• When light hits the IMOD, it is reflected off,both fromthe top of the thin-film stack and off the reflective membrane.

• Out of phase.• Optical cavity .• Interference.• Have two states :

Open stateCollapsed state

Figure 2

Figure 4

COLLAPSED STATE.

• A small voltage is applied

• Electrostatic force causes the membrane to collapse.

• Height of optical cavity resultsin constructive interference at UV wavelengths.

• Element appears black.

Figure 3

Color Generation:

Figure 5

MEMORY

• Ability to keep the image for along time.• Cause of memory is the bistable behavior of

IMOD• The bistability of mirasol displays comes from the

inherent Hysteresis. • Hysteresis derives from an inherent imbalance

between the linear restorative forces of the mechanical membrane and the non-linear electrostatic force.

• Electro-mechanical structure .

• The mechanical force can be defined as:

•The electrostatic force can be defined as:

•At equilibrium the net force must be zero. Therefore

Figure 6

Linear Restoring Force Vs Non linear attractive force

Figure 7

HYSTERISIS LOOP

Figure 8

EXPLOITING HYSTERESIS .

• Hold voltage

• Short activation pulse to switch to collapsed state.

• Short release pulse to switch to open state.

Figure 9

IMOD ADDRESSING .

• Addressing is the mechanism by which pixels are turned on and off.

•There are essentially two types of addressing schemes:Direct - dedicated control line/driver for

every pixel. Multiplexed - drive a larger number of ordered pixels

via their row and column address.

For example, in a 10x10 matrix of pixels, direct addressingrequires 100 drivers; multiplexing requires only 20, one for each row and column.

Figure 10

Figure 11

ADVANTAGES:

• Speed

• Readability

• Robustness

• Low power consumption

• Industry Compatibility

• True-to-life Image quality

• Ease of Manufacture

1. SPEED

• The deformable IMOD membrane only has to move a shortdistance—a few 100 nanometers—in order to switch betweentwo colors.

• An IMOD element’s switching time is 1000 times faster than traditional displays

2. READABILITY

• Luminance- Amount of light reaching human eyeReflectivity of white sheet of paper-70 to 90%,news paper- 60%IMOD-60% reflectivity

• Contrast ratio-Ratio of displays white state reflectivity to its dark state.

Contrast too low-display will appear washed out.Contrast too high-image look sharper and improve readability.Contrast ratio of news paper is about 4:1.

•Under high ambient light conditions, LCD displays contrast decreasesand hence very difficult to view.

•For IMOD as the light level increases, displays white state reflectivity also Increases. Hence high contrast ratio of about 8:1

Figure 13

3. Robustness

•This is the main advantage-paper like readability even in high ambient light conditions consuming less power

•Due to the bistable nature.•No need of refreshment.

•No back light used.

•The biggest problem with LCD lifetime is the use of organic materials, which break down over time when exposed to high temperature and light sunlight(10-30deg).•Mirasol displays utilizing the air gap are capable of performing over an extended temperature range (-30 to 70 deg).•At the same time are impervious to high-intensity visible and UV radiation.

4.Low power consumption

Watching video LCD IMOD display50-60minutes 160-165 minutes

Figure 12

APPLICATIONS:

• Gaming devices

• MP3 players

• Laptop and desktop monitors

• Digital TV and DVD player screens

• Medical imaging

• Digital camera and camcorder screens

Announced Design Wins for mirasolDisplays

• G-CORE Mini Caddy Golf GPS 1.2" Bichrome• Inventec V112 Smartphone 1.1" Bichrome• Cal-Comp iT-810 Handset 1.2" Bichrome• Hisense C108 Handset 1.2" Bichrome• Acoustic Research ARWH1 Bluetooth® Headset 1.1”

Bichrome• Korea Telecom Freetel (KTF) ShowCare Monitoring

System 1.1" Bichrome

Inventec V112 Smartphone

Hisense C108

KTF_ShowCare

FreestyleAudioFA300_B

G-CORE_Mini-Caddy

Figure 14

CONCLUSION• IMODs are powerful photonic devices that

can be used as excellent displays for manipulation of light not only in cell phones but also in camcorders, computer monitors, wall mounted TVs, etc.

• All in all, in the coming days, IMOD displays are likely to replace other devices.

REFERENCES

• Electronics for you(Nov-2008)

• M.W. Miles, “Toward an iMoD ecosystem”

• www.wikipedia.org/wiki/Interferometric_modulator_display

• www.qualcomm.com/common/documents/white_papers/QMT_Technology_Overview_.pdf

• www.qualcomm.com/common/documents/white_papers/QMT_Operating_Principles_IMOD_Drive.pdf

THANK YOU