Complementary Metal Oxide Semiconductor Detector Research Articles

Comparison of a CMOS-based and a CCD-based digital x-ray imaging system: Observer studies

The purpose of this study is to compare the performance of a complementary metal–oxide–semiconductor (CMOS)-based digital x-ray imaging system with that of a charge-coupled device (CCD)-based system for small animal research. A CMOS-based digital x-ray imaging system was developed and tested. The core of this system is a detector module consisting of eight joint CMOS chips, each having a size of 512×1024 pixels with a readout unit on the side. The pixel size of the CMOS detectors is 0.048 mm. The contrast detail detectability of the CMOS-based system was studied using different phantoms, and compared with that of a CCD-based digital imaging system. The contrast detail curves of the CMOS-based image system, obtained from the observer-based studies, are highly comparable to the CCD-based imaging system, particularly at higher x-ray exposures. The images of fine structures of a mouse, acquired by the CMOS system, demonstrated the capability of the system in the studies of small animals. With integration potential, manufacturability, and low costs, the CMOS-based imaging systems could be used in animal studies and potentially become useful clinical tools for diagnosis.

Development of a lens-coupled CMOS detector for an X-ray inspection system

A digital X-ray imaging detector based on a complementary metal-oxide-semiconductor (CMOS) image sensor has been developed for X-ray non-destructive inspection applications. This is a cost-effective solution because of the availability of cheap commercial standard CMOS image sensors. The detector configuration adopts an indirect X-ray detection method by using scintillation material and lens assembly. As a feasibility test of the developed lens-coupled CMOS detector as an X-ray inspection system, we have acquired X-ray projection images under a variety of imaging conditions. The results show that the projected image is reasonably acceptable in typical non-destructive testing (NDT). However, the developed detector may not be appropriate for laminography due to a low light-collection efficiency of lens assembly. In this paper, construction of the lens-coupled CMOS detector and its specifications are described, and the experimental results are presented. Using the analysis of quantum accounting diagram, inefficiency of the lens-coupling method is discussed.

Chemical Sensing Systems Using Xerogel-Based Sensor Elements and CMOS Photodetectors

We present the first example of an integrated complementary metal-oxide-semiconductor (CMOS) photodetector coupled with a solid-state xerogel-based thin-film sensor to produce a compact chemical sensor system. We compare results using two different CMOS-based detector systems to results obtained by using a standard photomultiplier tube (PMT) or charge-coupled device (CCD) detector. Because the chemical sensor elements are governed by a Stern-Volmer relationship, the Stern-Volmer quenching constant is used as the primary comparator between the different detectors. All of the systems yielded Stern-Volmer constants from 0.042 to 0.049 O/sub 2/%/sup -1/. The results show that the CMOS detector system yields analytical data that are comparable to the CCD- and PMT-based systems. The disparity between the data obtained from each detector is primarily associated with the difference in how the signals are obtained by each detector as they presently exist. We have also observed satisfactory reversibility in the operation of the sensor system. The CMOS-based system exhibits a response time that is faster than the chemical sensor element's intrinsic response time, making the CMOS suitable for time-dependent measurements. The CMOS array detector also uses less than 0.1% the power in comparison to a standard PMT or CCD. The combined xerogel/CMOS system represents an important step toward the development of a portable, efficient sensor system.