survey of tof and imaging systems
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Survey of IR/TOF/3D Imaging
SystemsSystems
Manu Suryavansh
4/18/2012
Topics• History and Present –
– LIDAR
– Lock-In amplifier and pixel
– CCD
– CMOS Imagers– CMOS Imagers
– Infrared communication System – IRDA
– TOF and 3D Imaging
– SAPD
• Some major companies -
Depth/Range Sensor Applications
• 3D Imaging
• Gaming
• Auto Focus in Digital camera
• Object detection• Object detection
• Robotics
Distance/Depth Measurement
TechniquesContactless
distance measurement
Triangulation Interferometry Time of Flight
Pulse
Continuous Wave
Modulation
TOF Techniques
Depth/TOF Techniques - Triangulation
• Determine the depth of a single point in the scene.
• Used in sharp analog distance sensor (20 – 150 cm range)
Depth/TOF Techniques - Passive
Stereoscopy
• Single point depth estimation using two
cameras.
Living Images – Light Field
Camera/Plenoptic Camera
• Recently released to market by Lytro.
• It uses a microlensarray to capture 4D array to capture 4D light field.
• Depth information can also be extracted.
• Pictures can be focused after they are taken!!
Time of Flight - Wikipedia
• Applications –
– Calculate Electron mobility
– Mass spectrometry
– Near Infrared spectroscopy – property of material– Near Infrared spectroscopy – property of material
– Ultrasonic flow meter - velocity of fluids
– 3D Imaging/Depth Sensor
TOF -1
Complex and Big
Vs
Demodulating Pixel
Vs
Ref – Canesta Inc – 2004 IEEE Computer Society
Basic 3D TOF Imaging Principle
Phase Measurment
Simple Demodulating Pixel
Reference - Industrial Robot Journal
Demodulating IR Pixel
• Sending two pulses with 0 and 90 degree
phase.
• Performing DFT on the demodulated to get
phase.phase.
Noise Sources in photo detectors
CMOS Imager
CMOS Active Pixel Structure (APS)
• Color Image Sensor consists of a photo sensor and a color filter.
• There are three types of photo sensors –photodiode, bipolar phototransistor and photo FET.FET.
• There are several types of color filters like – Bayer sensor, Foveon X3 Sensor etc.
• Amplifier
• CMOS Imagers have relatively very small pixels (5um x 5um and even smaller).
SAPD – Single Photon Avalanche
Photodetector Camera
• An avalanche photodiode (APD) is a highly
sensitive semiconductor electronic device that
exploits the photoelectric effect to convert
light to electricity – Wikipedia.light to electricity – Wikipedia.
Lock-In Amplifier/System
• A lock-in amplifier system takes a periodic
reference signal and a noisy signal as input
signals to a phase sensitive detector.
• Reference Signal – r(t)=sin(2*pi*fo*t)• Reference Signal – r(t)=sin(2*pi*fo*t)
• Input Signal – i(t)=Asin(2*pi*fo*t + Q) + n(t)
• Output – P(t) = r(t)*i(t) = ½Acos(Q) - other
LOCK-In CCD/Photodiode
• The lock-in CCD is based on synchronous
photo charge detection and storage.
• Using 4 samples offset, phase and amplitude
can be determined. can be determined.
• Integration time – d1
Single Pixel TOF
Single Pixel + Demodulator
Gain ADC DFT/FFT
TOF Cont
Pixel ADC using SDM
Digital/Analog CDS can be used to cancel Ambient light/noise.
Example - A Range Image Sensor Based on 10-µm Lock-In
Pixels in 0.18µm CMOS Imaging Technology – ISSCC-2010
Ref – D. Stoppa – ISSCC-2010
Example -1, cont
Example2 – A 16x16 Pixel Distance sensor with In-Pixel circuitry
that tolerates 150klx of ambient light – JSSC-2010-Gerald Zach
• Range – 0 to 3.2m
• Standard deviation – few cm’s
• Linearity error -> +/-2cm
• Process – 0.6um BiCMOS• Process – 0.6um BiCMOS
• Pixel size – 16um x 16um
• Illumination source – 4 LED’s of 850nm
• Power Consumption – 10W
Example2- cont.
Some companies working on TOF/3D
– Canesta/Microsoft
– Primesense
– SoftKinetic
– PMDTech– PMDTech
– Mesa Imaging
PMDVision- CamBoard Nano
Infrared Remote Control Systems
Vishay/Sharp makes parts like these
Carrier Frequency – 30KHz to 56KHz
Wavelength – 940nm
Wireless Infrared Communications
IrDA supports 4Mb/s data rate.
Cmos Optical Preamplifier with ambient light cancellation- Ref – Phang and Johns – IEEE-1999
Ambient Light Cancellation - 1993
Wally did this app note almost 20 years ago!
Ultrasonic TOF Based depth sensor
• Time based as speed of sound travels much
slower.