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
• Single point depth estimation using two
Living Images – Light Field
• Recently released to
market by Lytro.
• It uses a microlens
aarrrraayy ttoo ccaappttuurree 44DD
• 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 – pprrooppeerrttyy ooff mmaatteerriiaall
– Ultrasonic flow meter - velocity of fluids
– 3D Imaging/Depth Sensor
Complex and Big
Ref – Canesta Inc – 2004 IEEE Computer Society
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
• There are several types of color filters like – Bayer
sensor, Foveon X3 Sensor etc.
• CMOS Imagers have relatively very small pixels
(5um x 5um and even smaller).
SAPD – Single Photon Avalanche
• An avalanche photodiode (APD) is a highly
sensitive semiconductor electronic device that
exploits the photoelectric effect to convert
light to electricity –– WWiikkiippeeddiiaa..
• A lock-in amplifier system takes a periodic
reference signal and a noisy signal as input
signals to a phase sensitive detector.
• Reference Signal – rr((tt))==ssiinn((22**ppii**ffoo**tt))
• Input Signal – i(t)=Asin(2*pi*fo*t + Q) + n(t)
• Output – P(t) = r(t)*i(t) = ½Acos(Q) - other
• The lock-in CCD is based on synchronous
photo charge detection and storage.
• Using 4 samples offset, phase and amplitude
ccaann bbee ddeetteerrmmiinneedd..
• Integration time – d1
Single Pixel TOF
Single Pixel +
Gain ADC DFT/FFT