Paul D. Willson

Preliminary results obtained from a novel CdZnTe pad detector and readout ASIC developed for an automatic baggage inspection system

A linear CdZnTe pad detector array with approximately 1 mm/sup 2/ pad area has been developed. The detector has a wide energy range from about 20 to 200 keV. A fast, low-noise monolithic mixed signal ASIC chip has been developed to read out these detector arrays. A prototype X-ray imaging system consisting of the CdZnTe detector array and the monolithic ASIC chip has been fabricated and tested. In this system, the detectors are abutted against each other to form an approximately 1 m long linear array. The system has been used to take preliminary scanned images of complex objects at various energies. New results obtained from this system is discussed.

Front-end Electronics for Spectroscopy Applications (FESA) IC

Non-destructive evaluation and inspection using X-rays require the detection of large photon fluxes. Typically, this requirement is met by operating the detectors in current mode, at the expense of the ability to measure the photon energy. This makes it necessary to obtain the energy information by other means, such as varying the energy of the X-ray source. We have developed an integrated circuit for the fast readout of solid-state X-ray and gamma ray detectors with multi-energy capability. The 32-channel Front-end Electronics for Spectroscopy Applications (FESA) chip is designed to handle photon rates in excess of one million photons per second per channel. In each channel, the detector pulses are shaped and amplified and then processed by a simple pulse-height analyzer that consists of five comparators each of which is connected to a dedicated counter. The 160 counters an each chip can be read out in less than 25 /spl mu/s. The FESA IC features digitally controlled gains and offsets, a calibration input and an analog test output, both of which can be connected to any channel. The five comparator threshold voltages, common to all channels, are provided externally, as is the current that controls the pulse shaping time.

VNIR hypersensor camera system

The hypersensor camera operates with a unique multispectral imaging modality developed recently at Surface Optics Corporation. The Hypersensor camera is small, low cost, rugged, and solid state, using micro-optics and an array of spectral filters, which captures a complete multispectral cube of spatial and spectral data with every focal plane exposure. The prototype VNIR Hypersensor camera captures full cubes of 588x438 (spatial pixels) x 16 (spectral bands) at frame rates up to 60 Hz. This paper discusses the optical design of the Hypersensor camera, the measured performance, and the design and operation of a custom video-rate hyperspectral processor developed for this system.

Multi-Energy, Fast Counting Hybrid CZT Pixel Detector with Dedicated Readout Integrated Circuit

A new mixed signal front-end readout electronics integrated circuit (IC) called HILDA (Hyperspectral Imaging with Large Detector Arrays) has been developed for two-dimensional CdZnTe (CZT) pixel detector arrays. The CZT array is directly bonded on top of the IC. The CZT array and the HILDA-IC have matching geometric pixel/channel structure and dimensions, a 16times16 array of 0.5 mm times 0.5 mm pitch. They are mounted together using flip-chip bump bonding. The pixel detector and readout IC are designed for high-rate photon counting independently for each channel/pixel and multiple-energy binning up to eight energy bands. Therefore, eight images can be produced that represent identical slices in time and space but different energy bands. Several HILDA CZT pixel detector hybrids have been fabricated and tested. The CZT pixel detector, the readout IC and preliminary test results are presented in this paper. The main potential applications envisioned for this chip are industrial non-destructive inspection, security applications and CT scanners.

Imaging Using Energy Discriminating Radiation Detector Array

Industrial X‐ray radiography is often done using a broad band energy source and always a broad band energy detector. There exist several major advantages in the use of narrow band sources and or detectors, one of which is the separation of scattered radiation from primary radiation. ARDEC has developed a large detector array system in which every detector element acts like a multi‐channel analyzer. A radiographic image is created from the number of photons detected in each detector element, rather than from the total energy absorbed in the elements. For high energies, 25 KeV to 4 MeV, used in radiography, energy discriminating detectors have been limited to less than 20,000 photons per second per detector element. This rate is much too slow for practical radiography. Our detector system processes over two million events per second per detector pixel, making radiographic imaging practical. This paper expounds on the advantages of the ARDEC radiographic imaging process.

Scanned x-ray images from a linear CdZnTe pad array with monolithic readout electronics

A linear CdZnTe pad detector array with approximately 1 mm2 pad area has been developed. The detector has a wide energy range from about 20 to 200 keV. To read out these detector arrays, a fast, low-noise monolithic mixed signal ASIC chip has been developed. A prototype x-ray imaging system consisting of the CdZnTe detector array and the monolithic ASIC chip has been fabricated and tested. In this system, the detectors are abutted against each other to form an approximately 1 m long linear array. The system has been used to take preliminary scanned images of complex objects at various energies. New results from this system will be presented.

Video-rate visible to LWIR hyperspectral imaging and image exploitation

Hyperspectral imaging provides the potential to extract information about objects in a scene that is unavailable to panchromatic imagers. This increased utility, however, comes at the cost of tremendously increased data. To have the broadest range of applications, extraction of the spectral information must occur in real-time. Attempting to produce and exploit complete cubes of hyperspectral imagery at video rates, however, presents unique problems, since data rates are scaled by the number of spectral planes in the cube. MIDIS (multi-band identification and discrimination imaging spectroradiometer) allows both real-time collection and processing of hyperspectral imagery over the range of 0.4 /spl mu/m to 12 /spl mu/m. We present the major design innovations associated with producing high-speed, high-sensitivity hyperspectral imagers operating in the VIS/NIR SWIR/MWIR and LWIR and of the electronics able to handle data rates up to 160 megapixels per second, continuously. Details of two realtime spectral imaging techniques used in MIDIS, dispersive and Fourier transform, are presented. Key to development of MIDIS are high-speed, high sensitivity arrays operating in the stated bands. Real-time algorithms able to exploit the spectral dimension of the imagery are also discussed. Beyond design and performance issues, the paper also discusses applications of real-time hyperspectral imaging technology, including problems such as mine detection, countering CC&D (camouflage, concealment, and deception), and counter terrorism applications.

Manufacturing and performance evaluation of a refractive real-time MWIR hyperspectral imager

Hyperspectral imaging in the 2-5 μm band has held interest for applications in detection and discrimination of targets. Real time instrumentation is particularly powerful as a tool for characterization and field measurement. A compact, real-time, refractive MWIR hyperspectral imaging instrument has been designed, and is undergoing testing. Using a combination of dispersive and corrective elements, the system has been designed for integration and preliminary test at room temperature with passive focus correction for the cryogenic elements. The F/1.75 design supports near diffraction limited performance from 2.5 μm to 5.0 μm. This paper will review the challenges in manufacturing such a system as well as the alignment and performance data.

Video rate visible to LWIR hyperspectral image generation and exploitation

Hyperspectral imaging is the latest advent in imagin technology, providing the potential to extract information about the objects in a scene that is unavailable to panchromatic imagers. This increased utility, however, comes at the cost of tremendously increased data. The ultimate utility of hyperspectral imagery is in the information that can be gleaned from the spectral dimensions, rather than in the hyperspectral imagery itself. To have the broadest range of applications, extraction of this information must occur in real-time. Attempting to produce and exploit compete cubes of hyperspectral imagery at video rates, however, presents unique problems for both the imager and the processor, since data rates are scaled by the number of spectral planes in the cube. MIDIS allows both real-time collection and processing of hyperspectral imagery over the range of 0.4 micrometers to 12 micrometers .

Performance and application of real-time hyperspectral imaging

Hyperspectral imaging is the latest advent in imaging technology, providing the potential to extract information about the objects in a scene that is unavailable to panchromatic imagers. This increased utility, however, comes at the cost of tremendously increased data. The ultimate utility of hyperspectral imagery is in the information that can be gleaned from the spectral dimension, rather than in the hyperspectral imagery itself. To have the broadest range of applications, extraction of this information must occur in real-time. Attempting to produce and exploit complete cubes of hyperspectral imagery at video rates, however, present unique problems for both the imager and the processor, since data rates are scaled by the number of spectral planes in the cube. MIDIS, the Multi-band Identification and Discrimination Imaging Spectroradiometer, allows both real-time here are the major design innovations associated with producing high-speed, high-sensitivity hyperspectral imagers operating in the SWIR and LWIR, and of the electronics capable of handling data rates up to 160 megapixels per second, continuously. Discussion of real-time algorithms capable of exploiting the spectral dimension of the imagery is also included. Beyond design and performance issues associated with producing and processing hyperspectral imagery at such high speeds, this paper also discusses applications of real-time hyperspectral imaging technology. Example imagery includes such problems as detecting counterfeit money, inspecting surfaces, and countering CCD.