Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Pulse-width modulation wikipedia , lookup
Stray voltage wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Buck converter wikipedia , lookup
Voltage optimisation wikipedia , lookup
Alternating current wikipedia , lookup
Video camera tube wikipedia , lookup
Mains electricity wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Image Sensor Technologies Chris Soltesz SSE Deluxe Sony Electronics, Inc. BPSD Image Sensor Technologies An introductory guide to CCD and CMOS imagers Image Sensors An image sensor is an electronic device that converts a image (light) to an electric signal. They’re used in digital cameras and other imaging devices. Imagers are typically an array of charge-coupled devices (CCD) or CMOS sensors such as active-pixel sensors (APS). Color Principles Electromagnetic Spectrum Spectral Characteristics Color Primaries Color Primaries R Y M WHITE G C B BLUE 1 0 1 0 1 0 1 0 RED 1 1 0 0 1 1 0 0 GREEN 1 1 1 1 0 0 0 0 Dichroic Prism Blue Imager Green Imager White Light Red Imager Additive Color Image Sensor Technologies Image Sensor Technologies What is the difference between CCD & CMOS imagers? a) b) c) d) Generate and Collect Charge Measure Charge and turn into voltage or current Output signal is in the Thethe difference strategies and mechanisms Transfer Mechanism developed to carry out those functions. Mechanism Differences CCD Image Sensor Charge Transfer Vertical and Horizontal CCD Light-to-charge Conversion Capacitance Equation Q V or C = Capacitance Q = Charge V = Voltage Amplifier behind Horizontal CCD Charge Accumulation Photo Sensor (Light-sensitive Region) of a Pixel C Charge-to-voltage Conversion /Amplification Q C V Charge-to-voltage Conversion /Amplification Amplifier within Pixel Voltage Transfer Signal Wire (Micro Wire) CMOS Image Sensor CCD Image Sensor Pixel (a) Light Photo Sensor (b) (Light-sensitive Region) Charge (Electrons) Vertical CCD (c) Output Amplifier (x) Horizontal CCD (d) CMOS Image Sensor Pixel Amplifier Photo Sensor (b) (a) (y) (Light-sensitive Region) Light Signal ON ON Charge O N Pixel-select Switch (e) Pixel Row (j) Column Signal Wire (Micro Wire) (f) Column-select Switch (g) Column Circuit (h) Row Signal Wire (i) (Micro Wire) ON Output Basic Mechanism of CCD Image Sensors CCD Image Sensor Pixel (a) Light Photo Sensor (b) (Light-sensitive Region) Charge (Electrons) Vertical CCD (c) Output Amplifier (x) Horizontal CCD (d) Charge Transfer- Photo Sensor to Vertical CCD Light Charge (Electrons) Photo Sensor Gate Opens Gate Charge (Electrons) Vertical CCD Charge Transfer The transfer of charge in a CCD is similar to a bucket-brigade moving water CCD Charge CCD CCD CCD Amplifier of CCD Image Sensor Voltage Generated on Surface of FD Horizontal CCD Output Output Gate Amplifier Micro Wire Charge Floating Diffusion (FD) Gate Gate Gate Basic Mechanism of CMOS Image Sensors CMOS Image Sensor Photodiode Active-Pixel Architecture (APS) Actual Photodiode Active-Pixel Architecture CMOS Image Sensor CMOS Image Sensor Pixel Amplifier Photo Sensor (b) (a) (y) (Light-sensitive Region) Light Signal ON ON Charge O N Pixel-select Switch (e) Pixel Row (j) Column Signal Wire (Micro Wire) (f) Column-select Switch (g) Column Circuit (h) Row Signal Wire (i) (Micro Wire) ON Outpu t Voltage Detection Fig. A When Charge is NOT Accumulated in Photo Sensor Surface Voltage to Amplifier Fig. B When Charge is Accumulated in Photo Sensor Surface Voltage to Amplifier Surface Voltage Surface Voltage 0V Voltage Voltage 0V Light High Photo Sensor High Charge Photo Sensor Voltage Detection Fig. C When Charge is NOT Accumulated in Photo Sensor Surface Voltage from Photo Sensor Amplified Voltage Fig. D When Charge is Accumulated in Photo Sensor Amplified Voltage Surface Voltage from Photo Sensor 0V 0V V2 Current Signal Voltage V1 V1 High Gate Gate Lifts High APS Block Diagram CCD & APS Performance Improvements CCD Image Sensor with 2-channel Horizontal CCDs Photo Sensor (Light-sensitive Area) Light Pixel Charge (Electrons) Vertical CCD Output Amplifier 1 Channel 1 Horizontal CCD 1 Channel 2 Horizontal CCD 2 Amplifier 2 CMOS Image Sensor with 3-channel Outputs Pixel Photo Sensor (Light-sensitive Region) Amplifier Light Signal ON ON Charge ON Pixel-select Switch Column-select Switch Output Channel 1 Channel 2 Channel 3 ON Column Circuit Column Signal Wire (Micro Wire) ON ON Row Signal Wire (Micro Wire) Technologies Used to Improve Performance of Image Sensors Buried-type Photo Sensor Conventional Photo Sensor Free Electron HAL Free Electron Signal Charge Signal Charge HAD-type CMOS Image Sensor Gate Gate Gate Signal Wire Poly-Si Gate Drain Drain P+ P+ (HAL) Source P+ N N N P+ N N SiO2 N P-type Si (Substrate) Photo Sensor Readout Gate FD Reset Gate Floating Diffusion (FD) FD Reset Drain Pixel-select Switch Amplifier Micro Condensing Lens Micro Condensing Lens On-chip Micro-lens CCD Sensor Structure Hyper HAD CCD Power HAD CCD Power HAD EX Imager Performance Improvement With New CCD construction On-Chip-Micro lens On-Chip-Micro lens Internal Lens Photo-Shielding film Photo-Shielding film Poly Si Poly Si Sensor V-register Sensor Fig.-1 Power HAD CCD Sensor Construction V-register Fig.-2 New CCD Sensor Construction Improvement of Smear with thinner insulation membrane Power HAD CCD camera : Power HAD EX CCD camera -125dB (Typical) : -140dB (Typical) Thinner Insulation Film Pros and Cons of Image Sensors Pros & Cons of Imagers Feature Comparison Feature CCD CMOS Signal out of pixel Electron packet Voltage Signal out of chip Voltage (analog) Bits (digital) Signal out of camera Bits (digital) Bits (digital) Fill factor High Moderate Amplifier mismatch N/A Moderate System Noise Low Moderate System Complexity High Low Sensor Complexity Low High Camera components Sensor + multiple support chips + lens Sensor + lens possible, but additional support chips common Relative R&D cost Lower Higher Relative system cost Depends on Application Depends on Application Pros & Cons of Imagers Performance Comparison Performance CCD CMOS Responsivity Moderate Slightly better Dynamic Range High Moderate Uniformity High Low to Moderate Uniform Shuttering Fast, common Poor Uniformity High Low to Moderate Speed Moderate to High Higher Windowing Limited Extensive Antiblooming High to none High Biasing and Clocking Multiple, higher voltage Single, low-voltage Pros & Cons of Imagers Winding Path of CMOS Development's Initial Prediction for CMOS Twist Outcome Equivalence to CCD in imaging performance Required much greater process adaptation and deeper submicron lithography than initially thought High performance available in CMOS, but with higher development cost than CCD On-chip circuit integration Longer development cycles, increased cost, tradeoffs with noise, flexibility during operation Greater integration in CMOS, but companion chips still required for both CMOS and CCD Reduced power consumption Steady improvement in CCDs Advantage for CMOS, but margin diminished Reduced imaging subsystem size Optics, companion chips and packaging are often the dominant factors in imaging subsystem size CCDs and CMOS comparable Economies of scale from using mainstream logic and memory foundries Extensive process development and optimization required CMOS imagers use legacy production lines with highly adapted processes akin to CCD fabrication Image Distortion with CMOS Camera CMOS Camera