Yesterday, Feb. 21st, ISSCC 2012 started in San Francisco. In the morning there were the plenary sessions. They did not had any specific imaging content or imaging information. In the afternoon during the so-called medical session, a couple of imaging papers were presented. Here follows a quick report about three of them.
H-S. Kim et al. (KAIST and SAIT) described an X-ray photon counting sensor built-up around a HgI2 photoconductor and a CMOS read out circuit. The interesting part of the paper was the discrimination in energy level of the incoming X-rays. In the presented solution, 3 different energy levels could be detected. The discrimination itself was done in the analog domain by using appropriate thresholding of the peak signal generated by the incoming X-ray photon. So it is really an X-ray photon counter and based on the peak signal that is detected by the CMOS circuitry, the energy of the X-ray can be classified.
J. Choi et al. (University of Michigan) presented a relative small image sensor that can work in 4 different modes. In a so-called monitoring mode, the sensor works at 0.8 V in a low power mode. In the case the sensor (autonomously) detects that it has sufficient energy, it can work at 1.8 V supply and run in a high gain mode (amplification of the signal by a factor 8), a normal mode and a high dynamic range mode (double exposure, both at half the resolution). The beauty of the design is the fact that the switching between these various mode basically requires a different set-up of the pixel and/or column-level ADC. This is done by a specific pixel design, such that the pixel circuitry can be used a regular source follower, or they form part of the ADC circuitry. The basic application for this sensor can be found in wireless sensor networks.
M-T. Chung et al. (Nat. Tsing Hua Univeristy, Hsinchu) presented an ultra-low power sensor, consuming 4.95 uW at a power supply voltage of 0.5 V. Pixel number 64 x 40 and 11.8 fps. The sensor converts the incoming information in a pulse-width modulated output signal. This is realized by an in-pixel comparator based on 5 transistors. Nice work to see a device operating at 0.5 V. The author claimed a dynamic range of 82 dB.
The afternoon session started at 1:30pm, and I entered the room around 1:20pm. At that time all speakers were already sitting on the front rows. The first view of these front rows scared me a bit : all black haired young guys. For the old grey man, it was a confrontation with the fact that the new generation is ready to take over, and they mainly come from the Far East. Nevertheless WELCOME guys, and make sure you have a lot of fun in solid-state imaging !
[If particular papers are not mentioned in my report, that only means that I did not attend the paper presentation. Not finding a paper review in my blog does NOT mean that the paper was of low quality !]
Albert, 21-02-2012.