Time-Resolved Solid-State Array Imaging Systems: Developments And Applications

Abstract

Several optical, single transient data imaging systems have been developed at the Lawrence Livermore National Laboratory for providing time-, space-, and intensity information of pulsed radiation sources. The basic components of these systems are fast-gated cameras, large-bandwidth transmission lines, large memories, and image processors. Gated MCPI are used with solid-state, one- or two-dimensional array cameras to record individual frames of an optical pulse. The MCP intensifiers are designed to provide large gain (> 10 6 electrons), fast optical shutter (≤1 nsec), low shading (≤10%), high spatial resolution (10 1p/mm at 50% CTF), and high sensitivity in the near UV (420 nm). Several methods are currently investigated to (1) produce faster optical gates without significant irising or reduction in resolution, and (2) to improve spatial resolution. Both photodiode arrays and charge-coupled devices (CCD) are used for the imagers in the solid-state cameras. These cameras are designed to achieve a large dynamic range (500:1), low saturation fluence (≤1.5 erg/cm2 at 420 nm), and small frame time (≤2.5 msec). Several commercially available imaging arrays containing 1035 x 1320, 512 x 512, 488 x 380, 128 x 128, 100 x 100 pixels each, with pixel diode sizes of ≤15μm, are examined for blooming, cross-talk, blemishes, and uniformity. Current investigations are concentrating on large segmented (512 x 512) photodiode arrays with CCD readout. All cameras are designed for fiber-optic or lens coupling. Maximum dynamic range and maximum signal-to-noise is achieved by using 8-, 10-, or 12-bit A/D converters. Large bandwidth fiber-optic transmission lines (720 Mbit/sec) and large memories are used for arrays with > 105 pixels, 10-bit A/D converters and short frame times. A technique known as data compression is applied to take advantage of a 10-bit system using an 8-bit data acquisition arrangement. The advent of large array cameras requires modifications in calibration procedure, data acquisition, and image processing. Gated optical imaging systems are used as a diagnostics on electron beams and plasma-, x-ray-, gamma-ray-, and neutron-sources too provide a snapshot of each event with high spatial resolution.