Optical characterization methods for solid-state image sensors

The accurate measurement of the optoelectronic properties of imaging sensors is of utmost importance for their appropriate use in various modern application fields, such as in metrology, quality control, environmental monitoring, medicine or for automotive applications. Key sensor parameters include spatial resolution, uniformity, sensitivity, linearity, signal to noise ratio and dynamic range. Today high-end optical systems mostly rely on charge coupled device (CCD) image sensors. Continuous progresses in CMOS submicron technology and the advent of ‘active pixel sensor’ (APS) imagers have however led to a wealth of novel line and area array imaging devices with added functionalities (eg. on-chip control and read-out electronics) or performance optimized for specific tasks (eg. a dynamic range in excess of 120 dB). The optimal use of CMOS image sensing technology nevertheless depends strongly on the absolute and accurate optoelectronic characterization of these devices. Modern measurement techniques for a reliable, traceable, precise and absolute measurement of the most relevant parameters of CCD and CMOS imaging sensors are described and discussed in the present paper, with examples based on recent state-of-the art CMOS imagers.