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Time of Flight Cameras - Refael Whyte
This document discusses time-of-flight cameras and range imaging. It explains that time-of-flight cameras work by illuminating a scene with amplitude modulated light and measuring the phase difference between the transmitted and reflected light, which encodes distance information. It describes the correlation process used to measure distance at each pixel and discusses sources of error such as multipath interference and temperature drift. Real data examples from a 120x160 sensor are shown. Applications discussed include uses in the Kinect, 3D scanning, and potential future uses in mobile phones.
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Similar to Time of Flight Cameras - Refael Whyte
Time of Flight Cameras - Refael Whyte
- 1. MIT Media Lab CameraCulture Introduction to Time-of-Flight Range Imaging Refael Whyte
- 2. MIT Media Lab CameraCulture Why Depth? • Color photos have limited depth information
- 3. MIT Media Lab CameraCulture Time-of-Flight Cameras 18 October 2013 © THE UNIVERSITY OF WAIKATO • TE WHARE WANANGA O WAIKATO 3
- 4. MIT Media Lab CameraCulture Measuring Distance • Illuminate scene with amplitude modulated light. • Phase difference between transmitted and reflected light encodes distance. • Transmitted and returning light is correlated to measure distance. 18 October 2013 © THE UNIVERSITY OF WAIKATO • TE WHARE WANANGA O WAIKATO 4
- 5. MIT Media Lab CameraCulture Measuring Distance • Returning light is correlated with reference waveform. • Reference waveform is phase shifted • Measured points fit a sine wave. 5
- 6. MIT Media Lab CameraCulture Correlation Function
- 7. MIT Media Lab CameraCulture Measuring Distance
- 8. MIT Media Lab CameraCulture Real Data • Measured correlation waveform of one pixel • Compute phase and amplitude from FFT.
- 9. MIT Media Lab CameraCulture Camera Data • Phase and amplitude images, 120x160 sensor.
- 10. MIT Media Lab CameraCulture Measurement Errors
- 11. MIT Media Lab CameraCulture Multipath • Multiple propagation paths. • In scene paths and lens flare effects. • Still an unsolved problem. Use low reflective material around objects of interest to mitigate 18/10/2013 © THE UNIVERSITY OF WAIKATO • TE WHARE WANANGA O WAIKATO 11
- 12. MIT Media Lab CameraCulture Multipath • The measured pixels value is the sum of both components on the complex plane. • Reflect table tops and floors can see reflection in the amplitude image.
- 13. MIT Media Lab CameraCulture Other Sources • Temperature drift. • Jitter. Jitter in the modulation signal limits precision. • Photon shot noise in pixel structure. Is assumed to be an independent guassian noise source. • Readout noise. Noise added by ADC and readout process. • Harmonic aliasing impacts accuracy.
- 14. MIT Media Lab CameraCulture Time-of-Flight at MIT • Access to commercial Time of flight cameras and custom built ones • Commercial ones from: Softkinetic, PMD and Mesa Imaging
- 15. MIT Media Lab CameraCulture Coke Bottle Light Sweep • Visualization of light in a coke bottle http://www.youtube.com/watch?v=fSqFWcb4rE • Light sweep with ToF Camera https://sites.google.com/site/tofvid/ • Similar results 1000x reduction in cost of hardware.
- 16. MIT Media Lab CameraCulture Time of Flight Applications • Next generation Kinect for Xbox One. http://www.youtube.com/watch?v=Hi5kMNfgDS 4 • Object Scanning http://www.youtube.com/watch?v=IXr9zqz6Bjc • Hand tracking http://www.youtube.com/watch?v=Qj4ymzTNw Dw • Other http://www.youtube.com/watch?v=eAlSfEqBBhM
- 17. MIT Media Lab CameraCulture Other Applications • • • • Manufacturing Automation Robotic navigation. Rumoured to being developed for phones so the sky is the limit.
Editor's Notes
- #3 Currentcolor imaging technology only provides clues about the depth in the scene. Only social cues like the size of objects and shadows.
- #4 Time of flight cameras measure the depth for each pixel. This is an example figure from a time of flight camera. Each pixel is located in X,Y,Z in space. Person infront of the scene.
- #5 Phase translates to distance. Measure phase because measuring direct time of flight is hard.
- #6 Really say that four frames are required. Say something about motion.
- #10 Talk about the noise. The black table cloth returns less light therefore is more noisy.
- #11 Say the modulation frequency is the length of the pulse. The shorter the pulse the more precision the measurements however phase wrapping.
- #12 Add comments about mixed pixels.
- #15 Talk about how we are exploring other areas for ToF. Medical imaging.