Imagers at ISSCC (4)

 

Prof. Etoh of Kinki University presented a new member of its high-speed camera family : “A 16Mfps 165 kpixel Backside-Illuminated CCD”.  This device captures the information at 16 Mfps and stores them on-chip.  The on-chip analog memory can hold 100+ images.  During the presentation very nice demo videos were shown.

This new device is a back-side illuminated one, because with 16 Mfps the sensitivity is becoming an issue.  To actually shield the on-chip analog memories from incoming back-side light, a new architecture of multiple n- and p-wells is developed on more or less thick epi-layers (top n-epi of 9 mm, bottom p-epi of 23 mm).

Personally I know prof. Etoh very well because in my Philips career I worked together with him.  What I admire so much about this person is the fact that he is a civil engineer specialized in water engineering !  He has no electrical engineering background, but he designs very advanced image sensors.  This is a great example of “thinking out of the box”.  On the other hand he shows that our analogy of potential wells with buckets on one hand, and the electrons in the wells with water in the buckets on the other hand helped him to develop very advanced imaging structures.

Next in line was Y. Yamashita (Canon) with “A 300mm Wafer Size CMOS Image Sensor with In-Pixel Voltage Gain Amplifier and Column-Level Differential Read-out Circuitry”.  Apparently this was the ISSCC of the world records : after a world record in speed, this must be a world record in size !  The imager has a size of over 20 cm by 20 cm !  Number of pixels is relatively low (1280 x 1248), so the pixels are very large, 160 mm x 160 mm, as a consequence, they can easily contain some extra electronics.  On the other hand, the bus capacitances of such a large imager are huge, so extra buffer electronics are a must in every pixel.  The application for this huge imager are night vision and astronomy.  Of both, examples and videos were shown.  Very impressive of course.

Because of the large pixel and the extra amplification in every pixel, the sensitivity is huge, namely 25 Melectrons/lux.s, as well as the conversion gain, being 318 mV/electron.  Noise level is reported to be 13 electrons rms with a maximum power consumption of 3.2 W.  The spec indicates that the maximum frame rate is 100 fr/s, but it is not mentioned whether the noise and power figure were measured at this maximum frame rate.

R. Walker (University of Edinburgh) reported about his PhD project : “A 128 x 96 Pixel Event-Driven Phase-Domain D?-Based Fully Digital 3D Camera in 0.13 mm CMOS Imaging Technology”.  This work was done in collaboration with ST, and is the very first fully integrated 3D camera on a single chip.  The generation of the depth map is fully integrated on the chip itself !

The pixels of this chip are based on SPADs.  But to avoid the enormous amount of data that can be generated by a SPAD, every pixel includes next to the SPAD an all-digital phase-domain delta-sigma implementation with 6 bit counters for partial in-pixel decimation.  The pixels are pretty large, 44.65 mm pixel pitch, and in combination with the 0.13 mm technology, some extra electronics can be afforded in every pixel.  A remarkable low power consumption was reported, only 40 mW.  Unfortunately I cannot post the presentation slides (because I do not have them) and I am not allowed to post them (because of the copyrights), but the presenter did a great job in explaining the working principle of the chip by means of a great set of slides.

MORE TO COME !

Albert, 25-02-2011.

4 Responses to “Imagers at ISSCC (4)”

  1. albert says:

    Thanks, I made changes accordingly.

  2. DP says:

    Thank you for your summary and analysis of the ISSCC papers.

    A couple corrections to units on the write up on the Canon paper:
    * the pixel pitch is 160 um, not mm
    * the CG is 318 uV/e, not mV/e

    Also, I don’t yet see the update to give Richard Walker credit on the paper from Edinburgh.

    Thanks,
    DP

  3. albert says:

    I thought I corrected it …. so I did it again.
    Concerning the micros and the millis, on my machine it is OK, but you are not the first one who complaines about the micros.
    I have no idea what the problem is and how to solve this.

  4. The mu’s are still broken.

    To enter a mu in WordPress there is an “Insert Symbol” button (labelled with a Capital Omega) in the WYSIWYG mode of the built-in mini-editor. WordPress files use 16-bit character encoding (“Unicode”) instead of traditional 8-bit (ASCII). That means there is a special code for all major symbols. Copying in a ? (mu) may also do the trick. I can help (E-mail or phone).

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