Imagers at ISSCC (2)

 

Due to business reasons I had to skip the ISSCC on Tuesday.  But I am very delighted that Dan McGrath wrote a short note about the imaging papers presented during my absence.  A big “thank you Dan !”.

So, here is the report written by Dan :

Three comments related to imaging for Tuesday ISSCC.

 

(1) Paper from C. Veerappan (cooperation between Delft University of Technology, STMicroelectronics, University of Edinburgh, Fandatione Bruno Kessler and EPFL) an described a 160×128 image sensor based on a SPAD pixel with in pixel circuitry to allow time-to-digital conversion. Fluorescent tags were differentiated by characterizing their time dependent decay through imaging multiple frames, in the process removing factors that limited the precision. The target application is fluorescent imaging (FLIM) to facilitate looking not just at the surface, but also into processes happening below the surface of biological samples (e.g., pollen grain). 10-bits were achieved by a combination of a ring oscillator and a thermometer code converter and alternative readout and evaluation modes were enabled by the circuitry. The price paid for this circuitry was a 2% fill factor and the need  to work to compensate for this thru the design of microlenses. The time jitter limitations were stated to result from the characteristics of the photodiode, not the circuitry.

 

(2) Paper by B. Richter (Fraunhofer Institute for Photonic Microsystems) described a VGA OLED display built on a transparent substrate with each pixel consisting of a small photodiode surrounded by an display element. The target application is a heads-up display where the user interface is managed by having the integrated image array track eye motion. The value of such a system is that it can be used when hand motion is not available, such in driving a car in hazardous conditions or in surgery. The application requires sophisticated optics based on the use of visible light for the display function and infrared light for the eye tracking, with beam splitting to allow the heads up function and with optics that differentiates between the wavelengths to provide the proper focal length for each function. This is similar to a Samsung paper presented several years ago at ISSCC, but where the imaging was used for a touch screen so that there was not the problem of the optical design.

 

(3) The evening session discussing the promise of the smart grid providing an information and control portal into the home for the homeowner and the utility appeared only to mention imaging once and then as aside in the form of a mention of security cameras. The bulk of the sensing and information gathering was non-imaging sensing of electrical loads and voltages and of motion sensors. Imaging appears to be something you carry with you, but not something that works humbly in the home.

 

Albert (& Dan), 23-02-2011 

  

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