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Performance of a novel wafer scale CMOS active pixel sensor for bio-medical imaging.
M Esposito1, T Anaxagoras, A C Konstantinidis
1Centre for Vision, Speech and Signal Processing, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford GU2 7XH, UK. School of Computer Science, University of Lincoln, Lincoln, LN6 7TS, UK.
Physics in Medicine and Biology
|June 10, 2014
Summary
Wafer scale CMOS active pixel sensors (APSs) offer a promising alternative for biomedical imaging. This study analyzes spatial non-uniformity in stitched APSs, achieving high uniformity and improved detection quantum efficiency (DQE) for advanced medical applications.
Area of Science:
- Medical Imaging Technology
- Sensor Physics
- Semiconductor Device Engineering
Background:
- CMOS active pixel sensors (APSs) are emerging as a viable alternative to traditional flat panel imagers (FPIs) in biomedical applications.
- Wafer-scale CMOS APSs, manufactured using reticle stitching, present challenges in response uniformity due to manufacturing variations.
- Spatial non-uniformity and regional variations are significant hurdles for the clinical adoption of large-area sensors.
Purpose of the Study:
- To investigate and quantify spatial non-uniformity in wafer-scale stitched CMOS APS.
- To develop a model for analyzing pixel-level electro-optical performance and identify sources of variation.
- To evaluate the image quality and detection capabilities of the developed APS in a mammography application.
Main Methods:
- A per-pixel analysis of electro-optical performance was conducted on a wafer-scale stitched CMOS APS.
- A signal generation model was developed to account for noise and gain variations across the sensor.
- Readout noise and conversion gain were evaluated at pixel, stitching block, and regional levels.
- Image quality metrics, including Contrast-to-Noise Ratio (CNR), and theoretical Detection Quantum Efficiency (DQE) were assessed.
Main Results:
- A novel per-pixel analysis revealed readout noise and conversion gain variations with a coefficient of variation as low as 1.9%.
- The mammography application demonstrated high uniformity in CNR, comparable to existing clinical detectors.
- Theoretical DQE evaluation indicated a higher performance for the CMOS APS compared to FPIs at zero-frequency.
Conclusions:
- The developed wafer-scale CMOS APS exhibits high uniformity and improved performance characteristics for biomedical imaging.
- The per-pixel analysis effectively addresses inhomogeneity issues inherent in stitched sensor manufacturing.
- The DynAMITe large-area CMOS APS presents a favorable trade-off between imaging area and performance uniformity, suitable for diverse medical applications.
