Thomas E. McDonald

Range-gated imaging experiments using gated intensifiers

A variety of range gated imaging experiments using high- speed gated/shuttered proximity focused microchannel plate image intensifiers (MCPII) are reported. Range gated imaging experiments were conducted in water for detection of submerged mines in controlled turbidity tank test and in sea water for the Naval Coastal Sea Command/U.S. Marine Corps. Field experiments have been conducted consisting of kilometer range imaging of resolution targets and military vehicles in atmosphere at Eglin Air Force Base for the U.S. Air Force, and similar imaging experiments, but in smoke environment, at Redstone Arsenal for the U.S. Army Aviation and Missile Command. Wavelength of the illumination laser was 532 nm with pulse widths ranging from 6 to 12 ns and comparable gate widths. These tests have shown depth resolution in the tens of centimeters range from time phasing reflected LADAR images with MCPII shutter opening.

Flat panel display technology for high-performance radiographic imaging

The high fidelity display of digital medical radiographs requires devices with high detail (3000 X 3500 arrays, 120 micrometers pixels), high brightness (2000 cd/m2), and high dynamic range (400). Medical radiographic film meets these requirements when transilluminated with bright illuminators. Currently available electronic displays using CRT technology are not able to provide the needed fidelity. New flat panel emissive display technologies offer potential solutions, particularly plasma displays and vacuum microelectronic displays. The NCAICM at Sandia National Laboratories is focusing particular attention on emissive display technologies. Commercial flat panel, color systems with improved fidelity are now becoming available. Static, monochrome designs using vacuum microelectronic technology offer the potential to provide a high fidelity display for medical radiography which meets these requirements.

Intensified/shuttered cooled CCD camera for dynamic proton radiography

An intensified/shuttered cooled PC-based CCD camera system was designed and successfully fielded on proton radiography experiments at the Los Alamos National Laboratory ALNSCE facility using 800-MeV protons. The four camera detector system used front-illuminated full-frame CCD arrays fiber optically coupled to either 25-mm diameter planar diode or microchannel plate image intensifiers which provided optical shuttering for time resolved imaging of shock propagation in high explosives. The intensifiers also provided wavelength shifting and optical gain. Typical sequences consisting of four images corresponding to consecutive exposures of about 500 ns duration for 40-ns proton burst images separated by approximately 1 microsecond were taken during the radiography experiments. Camera design goals and measured performance characteristics including resolution, dynamic range, responsivity, system detection quantum efficiency, and signal-to-noise will be discussed.

Range-gated LADAR coherent imaging using parametric up-conversion of IR and NIR light for imaging with a visible-range fast-shuttered intensified digital CCD camera

Research is presented on infrared (IR) and near infrared (NIR) sensitive sensor technologies for use in a high speed shuttered/intensified digital video camera for range-gated imaging at eye-safe wavelengths in the region of 1.5 microns. The study is based upon nonlinear crystals used for second harmonic generation (SHG) in optical parametric oscillators (OPOs) for conversion of NIR and IR laser light to visible range light for detection with generic S-20 photocathodes. The intensifiers are stripline geometry 18-mm diameter microchannel plate intensifiers (MCPIIs), designed by Los Alamos National Laboratory and manufactured by Philips Photonics. The MCPIIs are designed for fast optical shuttering with exposures and resolution for the wavelength conversion process are reported. Experimental set-ups for the wavelength shifting and the optical configurations for producing and transporting laser reflectance images are discussed.

Compact short-pulse laser for near-field range-gated imaging

This paper describes a compact laser, which produces high power, wide-angle emission for a near-field, range-gated, imaging system. The optical pulses are produced by a 100 element laser diode array (LDA) which is pulsed with a GaAs, photoconductive semiconductor switch (PCSS). The LDA generates 100 ps long, gain-switched, optical pulses at 904 nm when it is driven with 3 ns, 400 A, electrical pulses from a high gain PCSS. Gain switching is facilitated with this many lasers by using a low impedance circuit to drive an array of lasers, which are connected electrically in series. The total optical energy produced per pulse is 100 microjoules corresponding to a total peak power of 100 kW. The entire laser system, including prime power (a nine volt battery), pulse charging, PCSS, and LDA, is the size of a small, hand-held flashlight, System lifetime, which is presently limited by the high gain PCSS, is an active area of research and development. Present limitations and potential improvements will be discussed. The complete range-gated imaging system is based on complementary technologies: high speed optical gating with intensified charge coupled devices (ICCD) developed at Los Alamos National Laboratory and high gain, PCSS-driven LDAs developed at Sandia National Laboratories. The system is designed for use in highly scattering media such as turbid water or extremely dense fog or smoke. The short optical pulses from the laser and high speed gating of the ICCD are synchronized to eliminate the back-scattered light from outside the depth of the field of view (FOV) which may be as short as a few centimeters. A high speed photodiode can be used to trigger the intensifier gate and set the range-gated FOV precisely on the target. The ICCD and other aspects of the imaging system are discussed in a separate paper.

High-frame-rate digital radiographic videography

High speed x-ray imaging can be an important tool for observing internal processes in a wide range of applications. In this paper we describe preliminary implementation of a system having the eventual goal of observing the internal dynamics of bone and joint reactions during loading. Two Los Alamos National Laboratory (LANL) gated and image intensified camera systems were used to record images from an x-ray image convertor tube to demonstrate the potential of high frame-rate digital radiographic videography in the analysis of bone and joint dynamics of the human body. Preliminary experiments were done at LANL to test the systems. Initial high frame-rate imaging (from 500 to 1000 frames/s) of a swinging pendulum mounted to the face of an X-ray image convertor tube demonstrated high contrast response and baseline sensitivity. The systems were then evaluated at the Motion Analysis Laboratory of Henry Ford Health Systems Bone and Joint Center. Imaging of a 9 inch acrylic disk with embedded lead markers rotating at approximately 1000 RPM, demonstrated the system response to a high velocity/high contrast target. By gating the P-20 phosphor image from the X-ray image convertor with a second image intensifier (II) and using a 100 microsecond wide optical gate through the second II, enough prompt light decay from the x-ray image convertor phosphor had taken place to achieve reduction of most of the motion blurring. Measurement of the marker velocity was made by using video frames acquired at 500 frames/s. The data obtained from both experiments successfully demonstrated the feasibility of the technique. Several key areas for improvement are discussed along with salient test results and experiment details.

CCD operation using the High Speed Imager Test Station

The use of a high-speed (up to 100 MHz) programmable pattern generator and special clock driver/translator circuits for clocking solid-state multiple output imagers is discussed. A specific example of clocking a developmental 256 X 512 two-port CCD is illustrated. Reference to a prior report of clocking an eight-port CCD is included. Future use in clocking a CID imager is discussed.

High-speed optical shutter coupled to fast-readout CCD camera

A high frame rate optically shuttered CCD camera for radiometric imaging of transient optical phenomena has been designed and several prototypes fabricated, which are now in evaluation phase. the camera design incorporates stripline geometry image intensifiers for ultra fast image shutters capable of 200ps exposures. The intensifiers are fiber optically coupled to a multiport CCD capable of 75 MHz pixel clocking to achieve 4KHz frame rate for 512 X 512 pixels from simultaneous readout of 16 individual segments of the CCD array. The intensifier, Philips XX1412MH/E03 is generically a Generation II proximity-focused micro channel plate intensifier (MCPII) redesigned for high speed gating by Los Alamos National Laboratory and manufactured by Philips Components. The CCD is a Reticon HSO512 split storage with bi-direcitonal vertical readout architecture. The camera main frame is designed utilizing a multilayer motherboard for transporting CCD video signals and clocks via imbedded stripline buses designed for 100MHz operation. The MCPII gate duration and gain variables are controlled and measured in real time and up-dated for data logging each frame, with 10-bit resolution, selectable either locally or by computer. The camera provides both analog and 10-bit digital video. The cameras architecture, salient design characteristics, and current test data depicting resolution, dynamic range, shutter sequences, and image reconstruction will be presented and discussed.

Continuous-recording camera system for high-frame-rate high-resolution applications

The Los Alamos National Laboratory in support of Department of Energy and Department of Defense projects is developing a continuous recording, intensified, CCD camera system having a high-frame rate and fast shutter capability. The camera frame rates can range from 1 to approximately 3500 frames per second with sub-nanosecond shuttering capability. Camera shuttering (or gating) is provided by a microchannel plate image intensifier employing a Los Alamos designed stripline geometry that incorporates impedance matching to reduce pulse reflections and dispersion. The CCD pixel array size is 512 X 512, which provides good-resolution over a relatively wide field of view. Video data readout from the CCD is through 16 parallel ports with a pixel rate of up to 75 Mpixels/s per port. Camera outputs include 16 ports of both analog video and digital video provided by 10-bit onboard digitizers. A computer controlled frame grabber is being fabricated which will record data from the digital outputs and store the data in a local memory for transfer into a non-volatile storage medium such as a removable disk drive. Salient characteristics and performance data of a prototype camera are presented and range gated imaging applications are discussed.

High-frame-rate CCD cameras with fast optical shutters for military and medical imaging applications

Los Alamos National Laboratory (LANL) has designed and prototyped high-frame rate intensified/shuttered Charge-Coupled-Device (CCD) cameras capable of operating at Kilohertz frame rates (non-interfaced mode) with optical shutters capable of acquiring nanosecond-to- microsecond exposures each frame. These cameras utilize an Interline Transfer CCD, Loral Fairchild CCD-222 with 244 (vertical) X 380 (horizontal) pixels operated at pixel rates approaching 100 Mhz. Initial prototype designs demonstrated single-port serial readout rates exceeding 2.97 Kilohertz with greater than 5 lp/mm spatial resolution at shutter speeds as short as 5 ns. Readout was achieved by using a truncated format of 128 X 128 pixels by partial masking of the CCD and then subclocking the array at approximately 65 Mhz pixel rate. Shuttering was accomplished with a proximity focused microchannel plate (MCP) image intensifier (MCPII) that incorporated a high strip current MCP (28 uA/sq.cm) and a LANL design modification for high-speed stripline gating geometry to provide both fast shuttering and high repetition rate capabilities. Later camera designs use a close-packed quadrupole head geometry fabricated using an array of four separate CCDs (pseudo 4-port device). This design provides four video outputs with optional parallel or time-phased sequential readout modes. Parallel readout exploits the full potential of both the CCD and MCPII with reduced performance whereas sequential readout permits 4X slower operation with improved performance by multiplexing, but requires individual shuttering of each CCD. The quad head format was designed with flexibility for coupling to various image intensifier configurations, including individual intensifiers for each CCD imager, a single intensifier with fiber optic or lens/prism coupled fanout of the input image to be shared by the four CCD imagers or a large diameter phosphor screen of a gateable framing type intensifier for time sequential relaying of a complete new input image to each CCD imager. Camera designs and their potential use in ongoing military and medical time-resolved imaging applications are discussed.