Active pixel sensor

Nagashima, K., Kunihiro, T., Takayanagi, L, Nakamura, J., Kosaka, K. and Yurimoto, H. (2001) Output characteristics of stacked CMOS-type active pixel sensor for charged particles. Surface and Interface Analysis, 31, 131-137. 

With the so-called active pixel sensor (APS) imaging technology this noise behavior has been significantly improved by placing the first MOSFET into the pixel. The simplest APS image sensor pixel consists of one photodiode and three MOSFETs. APS technology is very attractive for several reasons. 

Mendis, S.K., et al., CMOS Active Pixel Image Sensors for Highly Integrated Imaging Systems. IEEE Journal of Solid-State Circuits, 1997. 32 p. 187-196. 

Zamowski, J., M. Pace, and M. Joyner, 1.5 FETper pixel standard CMOS active column sensor. Proceedings of Spie - the International Society for Optical Engineering, 1999. 3649 p. 186-196. 

The detector setup consists of four 256 x 256 pixel amorphous silicon technology sensor flat panels with 0.75 x 0.75 mm pixel size, having an active area of 192 x 192 mm [5j. These sensors are radiation sensitive up to 25 MeV and therefor well suited for detecting the LINAC radiation. The four devices are mounted onto a steel Irame each having the distance of one active area size from the other. With two vertical and two horizontal movements of the frame it is possible to scan a total area of about 0.8 x 0.8 m with 1024 x 1024 pixel during four independent measurements. 

Because the spatial area with higher temperature on the catalyst surface of one of the samples of the library is very small the detection of catalytic activities through temperature measurement cannot be carried out by direct temperature measurements but only by non-contact methods such as pyrometry or IRT. The IR video camera used here measures the emission at every point of the library in parallel. The detector consists of a 256x256 pixel array of Pt-silicide-IR-sensors. Each pixel delivers a voltage-signal that depends on the infrared radiation and the sensitivity of that pixel (fixed pattern noise). 

The organic field effect transistor (OFET) acts essentially as an electronic valve by modulating the semiconductor channel conductance via the gate field. This device is essential in all electronic applications, including integrated circuits for memories and sensors and also to drive individual pixels in active matrix displays. Probably one of the most exciting applications of organic electronic circuits is in the supply chain area, where radiofrequency-powered elements (e.g. RFID tag) may replace ID barcodes for identification and be applicable as a backplane drive for displays. 

Finally, the surprising sensitivity of CSPT based sensors when compared with the performance of the most common transducers used as chemical sensors must be commented upon. For instance, with a standard CSPT set up, the minimum detectable amount of triethylamine absorbed in a layer of Zn-TPP is 33 femtomoles per pixel the correspondent value for the same sensing layer on a 20-MHz Quartz Microbalance is about 5 picomoles [45]. In this regard, a caveat is necessary to indicate that these figures are the resolution in terms of absorbed mass and not in terms of the concentration in air and that this also turns out to depend on the active sensor area. 

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