17. Optical detectors and displays. Optical displays. FPD (Flat panel display)

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1 17. Optical detectors and displays Optical displays FPD (Flat panel display)

2 Display Resolutions High-definition television (HDTV): 720p ( progressive scan) 1080i ( split into two interlaced fields of 540 lines) 1080p ( progressive scan)

3 FPD (Flat Panel Display) FPD 이란? CRT 브라운관보다두께가얇고가벼운영상표시장치로 PDP, LCD, ELD, OLED 등으로나뉠수있다. 평판디스플레이 (FPD) LCD PDP FED OLED LCD : Liquid Crystal Display PDP : Plasma Display Panel FED : Field-Emitting Display OLED : Organic Light Emitting Display

4 LCD (Liquid Crystal Display) LC는일정온도범위에서유동성을지닌액정상태. 광학적으로복굴절성을나타내는결정임. 액체와고체의중간적인특성을가지는액정의전기ㆍ광학적성질을표시장치에응용한것. LCD는외부의빛을이용하는 Passive Type의 Display. V Applied volatage 증가

5 LCD 제품 삼성전자가국내벤처기업인소프트픽셀과투명플라스틱기판에아몰포스실리콘 (a Si) 기술을적용한세계최대투과형플렉시블 5인치, 해상도 qsvga급 (400 x 300 RGB, 100ppi) 투과형제품으로플라스틱 TFT LCD 기술구현에성공했다.( )

6 PDP (Plasma Display Panel) 기체방전을이용한표시장치. 방전이일어나면이온과전자로분리되는플라즈마상태일때나오는빛을이용. 단색표시 PDP는오렌지색을나타내는 Ne. Full color 표시 PDP는적색, 녹색, 청색을나타내는 Kr, Xe 등을이용. 장점 방전광을이용한자발광. 0.1~0.3mm의방전갭을가지므로패널형이가능. 형광체를이용한컬러발광이가능. 대화면패널제작이용이. 단점 소비전력이커서전지구동이어려움. 컬러발광효율이나쁨. 구동전압이높음. plasma PDP 발광원리

7 PDP 제품 삼성전자 102 인치 PDP TV : 가로 2m31cm, 세로 1m33cm (CES 2005)

자체발광형. ( 어두운곳이나외부의빛이들어올때도시인성이좋은특성을갖음.) 넓은시야각. ( 일반브라운관같이바로옆에서보아도화질이변하지않음.) 빠른응답속도.

8 OLED (Organic Light Emitting Diode) OLED 는유기물 ( 단분자 / 저분자또는고분자 ) 박막에양극과음극을통하여주입된전자와정공이재결합하여여기자를형성하고, 형성된여기자로부터의에너지에의해특정한파장의빛이발생하는현상을이용한자체발광형디스플레이소자. 자체발광형. ( 어두운곳이나외부의빛이들어올때도시인성이좋은특성을갖음.) 넓은시야각. ( 일반브라운관같이바로옆에서보아도화질이변하지않음.) 빠른응답속도. 텔레비전화면수준의동화상재생에도자연스러운영상을표현. (LCD 의약 1,000 배 ) 초박, 저전력. 백라이트라필요없기때문에저소비전력 ( 약 LCD 의 ½ ) 과초박형 ( 약 LCD 의 1/3 ) 이가능.

9 OLED 제품

10 FED (Field Emission Display) FED 는상하 Glass 기판사이에진공으로채워진구조. 상판 (Anode 판 ) 에는형광체가도포되어있고, 하판 (Cathode 판 ) 에는미세한마이크로이하사이즈의 Tip 들이무수히형성. 전자방출원리는뾰족한끝에전자가집중되고, 전자방출이용이한점에서피뢰침의원리와기본적으로유사. Gate와 Emitter사이에전압을인가하여전자를방출시키고, 상하양 Glass사이에강한전계를걸어주면전자는전계에의해가속되어강한운동에너지를보유. 가속된전자는 Anode 판내부의형광체를치고발광시켜빛을내게됨. CRT의우수한화질특성과 PDP의평판특성을동시에가지는 Flat Panel Display 로 저가격ㆍ고품질가능한차세대기술로평가.

11 LCD (liquid crystal display)

12 Display Modes Transmissive type TFT LCD: the light travels from the backlight through color filter and LC then appears on the panel. (high brightness but more power consumption). Reflective type TFT LCD contains a reflective mirror, utilizing the external light for image display. power saving, and light-weight (without backlight). Ideal for viewing with external light sources. Transflective type TFT LCD is a promising displaying device for both outdoor and indoor applications.

13 Driving Methods of LCD Passive Matrix: (PM-LCD) Simple matrix type was used in the first stage of LCDs. In this method, the transparent electrodes are set on X and Y axis. There is not switching device. Active Matrix: (AM-LCD) A switching device and a storage capacitor are integrated at the each cross point of the electrodes

14 TFT LCD TFT LCD (Thin Film Transistor Liquid Crystal Display) has a sandwich-like structure with liquid crystal filled between two glass plates.

15 LC (liquid crystal)

16 Twisted Nematic LC ( TN-LC ) Operation of twisted nematic Operation of twisted nematic field effect mode liquid crystal cell.

17 Super Twisted Nematic :STN 적은전압변화에큰투과율을보이는 STN가보다효율적인 display 장치라고생각한다.

18 ( 참고 )

19 ( 참고 ) TNLC as a polarization rotator (counterclockwise rotation in x-y plane)

21 Photon detection devices Photons to thermal energy (phototube) Metal-Semicon. photoconductor (Schottky-barrier photodiode)

22 5 basic steps of optical/ir photon detection 1. Get light into the detector Anti-reflection coatings 2. Charge generation Popular materials: Silicon, HgCdTe, InSb 3. Charge collection Electrical fields within the material collect photoelectrons into pixels. 4. Charge transfer If infrared, no charge transfer required. For CCD, move photoelectrons to the edge where amplifiers are located. 5. Charge amplification & digitization Amplification process is noisy. In general CCDs have lowest noise, CMOS and IR detectors have higher noise. Quantum Efficiency (#e/#p) Point Spread Function Sensitvi ity

Detector zoology 6.0 AlN III-Nitrides (c ~ 1.6 a 0 ) Direct gap Indirect gap 0.2 5.0 AlN Theory E(eV)=1.24/ λ( μm ) Bandga p (ev) 4.0 3.0 20 2.0 10 1.0 0.0 25 2.

23 Detector zoology 6.0 AlN III-Nitrides (c ~ 1.6 a 0 ) Direct gap Indirect gap AlN Theory E(eV)=1.24/ λ( μm ) Bandga p (ev) Al 2 O 3 GaN 6H-SiC ZnO InN Zincblend GaN 3C-SiC InN Theory Al 2 O 3 GaP ZnS AlP GaAs Si ZnSe CdS AlAs ZnTe CdSe AlSb InP CdTe GaSb InAs 5.0 InSb Lattice Constant (Å) Ge 1.0 Wa avelengt th ( μm )

24 2D Image Detectors X-ray Visible NIR MIR 0.1 [ m] Silicon CCD & CMOS HgCdTe InSb STJ Si:As

Image Sensor - Digital Film CCD Sensor CMOS Sensor

image sensor to record image in form of digital i

25 Image Sensor - Digital Film CCD Sensor CMOS Sensor Conventional Cameras use photographic films to record image. Digital cameras use a solidstate device called an image sensor to record image in form of digital i information. i CCD = Charge Coupled Device. CMOS = Complementary Metal Oxide Semiconductor

26 Image Sensors (2D detectors) In most of the consumer digital cameras image In most of the consumer digital cameras image sensor is much smaller than a 35 mm film.

27 Charge-coupled devices (CCD) image sensors Based on charge transfer to next pixel cell

28 CCD (Charge coupled device) Vertical charge transfer Horizontal charge transfer Output capacitor reset CCD Horizontal Shift Register Output capacitor Amp

30 CCD IMAGERS Qualities Text book performance for all parameters (QE, read noise, MTF, dark current, linearity, etc.). Deficiencies Low high-energy radiation damage tolerance. e.g. proton bulk damage and resultant CTE degradation. Significant off-chip electronic support required. Difficulty with high-speed readout (inherently a serial read out device).

31 CMOS image sensors Based on standard production process for CMOS chips, allows integration ti with other components.

32 CMOS IMAGERS Qualities Very tolerant to high-energy radiation sources (long life time). On- chip system integration (low power, low weight and compact designs). High speed / low noise operation (inherently a parallelrandom access readout device). Deficiencies Currently lacks performance in most areas compared to the CCD (charge generation, charge collection, charge transfer and charge measurement).

33 Comparison CCD/CMOS sensors CMOS: low cost CCD: medium to high end Source: B. Diericks: CMOS image sensor concepts. Photonics West 2000 Short course (Web)

Liquid Crystal Display (LCD)

Liquid Crystal Display (LCD) When coming into contact with grooved surface in a fixed direction, liquid crystal molecules line up parallelly along the grooves. When coming into contact with grooved surface