Measurement of the resolution of a charge-injected device

The structure and operation of a Charge Injected Device (CID) camera were researched and documented. Two methods for measuring the spatial resolution and system accuracy of the CID camera as described by the spatial spectral response were investigated. The first was a point imaging system that focused a point source onto a single pixel and the second used Mach-Zehnder interferometry and fast Fourier transform-based image processing to characterize the frequency response of the CID2710 camera. The first method investigated was a point source of light focused onto a single pixel in the CID2710 array. The feasibility of this method was studied for several focal lengths ranging from 250 mm down to 4 mm. However, this optical system was practically unfeasible to set up in the laboratory. The second method that was investigated and implemented used Mach- Zehnder interferometry to form fringe patterns of various spacings in four separate directions on the CID array. The fringe patterns were digitized and the FFT of each was calculated. The side-lobe amplitudes were used to plot fringe visibility against spatial frequency to calculate the modulation transfer function of the system. The resulting modulation transfer functions were then plotted against spatial frequency for each fringe pattern direction. Lastly, the noise equivalent bandwidths were calculated to describe the modulation transfer functions. The bandwidths in the horizontal, vertical, forward diagonal, and back diagonal directions were 3 lines/mm, 8 lines/mm, 6 lines/mm, and 8 lines/mm for a 9.06 mm-by-6.63 mm 755-by-484 element array. The CID camera and recording system had a resolution capability range from 3 lines/mm up to 8 lines/mm. The maximum resolution achieved through experimentation, 8 lines/mm, was only 23.5% of the manufacturer's specification of > 34 lines/mm. The CID camera and recording system appeared extremely bandwidth limited. This bandwidth limitation is attributed to the use of lowpass filters in both the camera operation and the frame grabber.