High speed CMOS image sensors Wim Wuyts – Sr. Staff Applications Engineer Cypress Semiconductor Corporation Belgium Vision 2006 P E R F O R M
Outline • Introduction • Architecture • Analog high speed CIS • Digital high speed CIS • 6T snapshot pixel type • Applications • Holographic data storage • Line sensors • Standard high speed products: LUPA-family • Conclusion High speed CMOS image sensors – Vision 2006 2
Why? Why high speed? High speed motion/data analysis for various application fields e.g. military ballistics High speed CMOS image sensors – Vision 2006 3
Introduction • Cypress has huge experience in high-speed CMOS Image Sensor (CIS) design • (almost) All big players works with us • Current max. pixel throughput of 13.2 Gpixels/s • Typical with multiple parallel analog output tabs • Now high-speed ADCs, LVDS output and on-chip timing sequencer available • Both array and linear sensors • Typical applications: high-speed motion analysis (crash and impact test), holographic data storage, digital film slow motion capture High speed CMOS image sensors – Vision 2006 4
Introduction • What’s high speed? • Typically > 100 MPixels/s • Requirements for high speed sensor design: • High speed read out architecture (> 50 MPixels / internal tab) • High sensitive snapshot shutter pixel with low Parasitic Light Sensitivity (PLS) • High speed ADCs • High speed interface (LVDS) High speed CMOS image sensors – Vision 2006 5
Technology: architecture • High-speed read out architecture: 60+ MPixels/s / internal analog tab • Parallel analog outputs e.g. 128*60 Mhz = 7.68 Gpixels/s throughput @ output • Windowing (ROI) to boost frame rate (both in X and Y e.g. 100*100 @ 768k fps) • Two trends: • Analog ‘naked’ image sensor: no sequencing or digital logic on-chip => requires complex camera system • System-on-a-chip approach (as much integration as possible): on-chip ADC, sequencer, interface High speed CMOS image sensors – Vision 2006 6
Technology: architecture Typical analog high speed image sensor: • 6T-pixel core (e.g. 1024 * 1024 divided in multiple sections • pixel drivers and column buffers • parallel analog output tabs (128+) • no timing sequencer on-chip (full external control on pixel array and read out timing). e.g. custom high-speed CIS architecture High speed CMOS image sensors – Vision 2006 7
Technology: architecture Typical system-on-a-chip high speed image sensor: • Timing sequencer on- board • Multiple ADCs on-chip • Single clock input • Multiple parallel digital LVDS outputs • Different read-out schemes possible to fit different needs e.g. LUPA-1300-2 architecture High speed CMOS image sensors – Vision 2006 8
Technology: 3T pixel Classic 3T-pixel with rolling shutter VDD reset row select T1 Vpd T2 T3 PD Cpd column output Ipd Volts reset GND Vout PD node time Sample & Read Out High speed CMOS image sensors – Vision 2006 9
Technology: Pixel type: 6T High speed applications requires: snapshot shutter, high sensitivity, low PLS => solution: 6T-pixel architecture Vpix Vmem Vpix Reset Sample Vpd T1 T2 Row - select Vpd A T3 T5 B Precharge T4 T6 Vpd - Vt High speed CMOS image sensors – Vision 2006 10
Rolling vs. snapshot Rolling Snapshot shutter shutter Distorted motion Freezed motion Electronic snapshot shutter required for high-speed motion analysis High speed CMOS image sensors – Vision 2006 11
Snapshot shutter x Reset frame In parallel Line number Integrate and COMMON SAMPLE&HOLD Sample frame y Flash could occur here COMMON RESET In parallel Burst readout sequential Time axis Integration time Burst Readout time High speed CMOS image sensors – Vision 2006 12
Snapshot shutter True Snapshot Shutter: Pipelined and Triggered type Triggered mode (IBIS5 alike pixel): Integration frame I+1 Integration frame I Readout frame I Readout frame I+1 Pipelined mode (6T-pixel): Integration frame I+1 Integration frame I+2 Readout frame I Readout frame I+1 High speed CMOS image sensors – Vision 2006 13
Frame rate calculation (fps) The frame rate depends on: 1. Pixel throughput in MPixels/s 2. Frame Overhead Time (FOT) � typical 10us 3. Row Overhead Time (ROT) � typical 300ns 4. Window size in X and Y → Frame period calculation: Frame period = FOT + Nr. Lines * (ROT + Nr. Pixels * clock period) Example: LUPA-300 (VGA resolution at 80MPixels/s) Frame period = 7.8 µs + (480 * (400 ns + 12.5 ns * 640) = 4.039 ms => 247.6 fps. � Frame rate increases with reduced window size in X and Y High speed CMOS image sensors – Vision 2006 14
Packaged high speed CIS Analog high speed CIS Digital high speed CIS High speed CMOS image sensors – Vision 2006 15
Applications • Examples of high speed applications: • Motion analysis: • Military ballistics and impact • Crash tests analysis • Sport analysis • Machine vision – inspection • Slow motion digital movie capture • Holographic mass data storage High speed CMOS image sensors – Vision 2006 16
Example of applications High speed motion analysis: Crash test analysis: High speed CMOS image sensors – Vision 2006 17
Application focus: Holographic data storage FEATURES • Ultrahigh storage densities: • Optical interference technique with coherent laser beams • Data storage in 3 dimensions! • Storage density > 31.5 Gbits/in2 => 200 GB on DVD disk) • Parallel access to data using data matrix and matrix reader instead of conventional photo diode • Fast data transfers upto 1 Gbps (high speed data read out with CMOS image sensor) • Durable, reliable, low cost media (polymer media) • Possible due to technology breakthrough on: SLM, CMOS image sensor technology, storage media High speed CMOS image sensors – Vision 2006 18
Application focus: Holographic data storage RECORDING DATA • A single laser beam is split into two: the signal beam that carries the data and a reference beam • The data is encoded on the signal beam with a Spatial Light Modulator (SLM) • Data is stored as a hologram that is recorded onto a light-sensitive storage medium at the point where the signal and reference beam intersect • Angle of incidence reference beam sets depth of writing High speed CMOS image sensors – Vision 2006 19
Application focus: Holographic data storage Writing data High speed CMOS image sensors – Vision 2006 20
Application focus: Holographic data storage READING DATA • A laser with the properties as the reference beam is trained on the media • By changing the angle of incidence a new page is read out • The laser projects the entire hologram, or page, onto a detector, a high speed CMOS image sensor • Spinning disk is scanned similar to CD principle High speed CMOS image sensors – Vision 2006 21
Application focus: Holographic data storage High speed CMOS image sensor Read out system Reading data High speed CMOS image sensors – Vision 2006 22
Application focus: Holographic data storage Custom high-speed sensor for holographic read out • Resolution: 1696 X * 1710 Y • Pixel size: 8 um * 8 um • Shutter type: Snapshot (6T-pixel) • Pixel rate: 13.2 GHz (using 32 LVDS outputs) • Frame rate: 485 fps • 10-bit on-chip ADC • Sensitivity: 650 V.m2 / W.s • Power dissipation: 1100 mWatt High speed CMOS image sensors – Vision 2006 23
Application focus (2): high-speed linear sensor Key features on linear high-speed CISs: • High speed pixel read out (> 200 MHz, with multiple outputs) • Very high spatial resolution • Large area imaging area (possible with stitching) • Linear pixel array with high sensitivity • Low power consumption • High on-chip integration of digital logic (lower system cost) • Typical applications: bar-code readers, dimensions measuring, position inspection devices High speed CMOS image sensors – Vision 2006 24
Application focus (2): high-speed linear sensor Custom high-speed linear sensor project: • Resolution: 8200 * 1 line sensor • Pixel size: 7 um * 7 um • Image area length: 57,4 mm • Chip size: 58.5 * 3.5 mm2 CMOS IS • Snapshot shutter • Line rate: 28.5k / s • Data rate: 240 MHz • 10-bit ADC on-chip • Sensitivity: 21 V.cm2/uJ High speed CMOS image sensors – Vision 2006 25
Standard high speed sensors Shutter Pixel Pixel Optical Frame Name Resolution type type pitch format rate 7 fps IBIS4-1300 1.3 MP Rolling 3T 7 um 2/3” 24 fps IBIS4-A-6600 6.6 MP Rolling 3T 3.5 um 1” 5 fps IBIS4-14000 13.85 MP Rolling 3T 8 um F-mount 3 fps Rolling IBIS5-B-1300 1.3 MP 4T 6.7 um 2/3” 27 fps Snapshot LUPA-300 VGA Snapshot 6T 9.9 um 1/2” 247 fps LUPA-1300 1.3 MP Snapshot 6T 14 um 1” 442 fps LUPA-4000 4 MP Snapshot 6T 12 um F-mount 15 fps STAR-250 250k Rolling 3T 25 um 1” 29 fps STAR-1000 1 MP Rolling 3T 15 um 1” 11 fps High speed CMOS image sensors – Vision 2006 26
LUPA family sensors LUPA-4000 – Traffic LUPA-300 – Fast machine monitoring and surveillance vision applications High speed CMOS image sensors – Vision 2006 27
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