Thursday, April 16, 2015

Self-Powered Image Sensor

EurekAlert: A research team led by Shree K. Nayar, Professor of Computer Science at Columbia University, has invented a prototype video camera, said to be the world's first fully self-powered - it can produce an image each second, indefinitely, of a well-lit indoor scene.

Self-Powered Pixel Design:
The photodiode PD is operated in photovoltaic mode with zero bias.
The voltage of the anode of PD increases to a level proportionate
to the incident lightenergy. In this case PD draws zero power to
produce a voltage proportionate to the incident light, and since it is
not biased it does not produce any dark current. An important feature
of the design is that emitter of transistor Q1 can be switched between
ground (for resetting) and a power supply (for harvesting).
Self-powered sensor assembly


  1. It should be simpler to combine a real solarcell and low power CMOS sensor. The solar cell provides energy gathering and the CMOS sensor for image capturing ...

    -yang ni

    1. Indeed for most applications it should be better. For retinal implants, in the work by Suat Ay, for example (Ay in the eye) that is not an option.
      I did suggest Shree add your work on forward biased pn jnc. pixels to his paper (which he did) because I thought that might be a good way to go about harvesting energy in a solid-state image sensor (compared to the array of discrete photodiodes). He might be contacting you.

  2. I don't see any special challenge. Probably a smaller photovoltaic cell and a small high resolution conventional image sensor will be better in all senses.

  3. Interesting work with discrete PD pixels for sure. Now, if only readout power scaled with pixel size, like harvested energy does, life would be easier. I note the paper references earlier work in the field of energy harvesting from image sensors, including work by Suat Ay and Orly Yadid-Pecht.

  4. Please correct me if I am wrong, but these are not APS pixels, and therefore their performance under weak illumination will not be comparable to normal CMOS image sensors.

    When doing a google search of the terms uspatents, image sensors, solar cell, the first result is to this patent:, which describes possibilities for solar cell functionality with APS pixels.

    1. Perhaps the team uses standard off-the-shelf PD and disposes them similar to IS.
      It is an excellent sample of prototyping and modeling for student education purposes. It can be used as a simulator for some processes in both CMOS and CCD IS.


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