At NASA GSFC we are developing a high resolution solar-blind photon counting detector system for UV space based astronomy. The detector comprises a high gain MCP intensifier fiber- optically coupled to a charge injection device (CID). The detector system utilizes an FPGA based centroiding system to locate the center of photon events from the intensifier to high accuracy. The photon event addresses are passed via a PCI interface with a GPS derived time stamp inserted per frame to an integrating memory. Here we present imaging performance data which show resolution of MCP tube pore structure at an MCP pore diameter of 8 micrometer. This data validates the ICID concept for intensified photon counting readout. We also discuss correction techniques used in the removal of fixed pattern noise effects inherent in the centroiding algorithms used and present data which shows the local dynamic range of the device. Progress towards development of a true random access CID (RACID 810) is also discussed and astronomical data taken with the ICID detector system demonstrating the photon event time-tagging mode of the system is also presented.
A new type of sensor has been developed for applications in high radiation environments such as space. In this paper we present the pixel structure, fabrication cycle and measured performance of a family of active pixel charge injection devices designed in PMOS and respectively CMOS technology. A simple 8 by 8 prototype was developed in 1996. This was followed by a 40 by 54 array having 90 micrometers pixel size. This device has address decoders integrated on chip and, a transfer gate included in each pixel in order to eliminate feed-through noise. These circuits were fabricated at RIT using a 6 micrometers PMOS double polysilicon technology. A third 128 by 128 array having 41 micrometers pixel size has been designed and manufactured at a commercial foundry using 2 micrometers CMOS technology. The on-chip decoders allow resetting of selective regions of the chip.
A large format CID imager module capitalizes on CID large well capacity and radiation resistance to image dental x- rays. The model, which consists of the imager, conversion phosphor and ancillary electronics, is encapsulated in a 40 X 28 X 5 mm<SUP>3</SUP> robust package that is lightproof, moisture-proof and meets FDA and RFI/EMI standards. Data exposure and readout is simple. The imager normally exists in an active reset mode until x-ray application automatically places the imager into a charge integration mode. Readout begins immediately upon completion of the x- ray exposure or manual application of an external trigger source. The imager returns to the reset mode once the data read out is complete. Pixels are arranged in an SVGA compatible 800<SUB>H</SUB> X 600<SUB>V</SUB> format. Each pixel is square and 38.5 microns/side. The imager is coated using a propriety phosphor deposition process that result in a limiting resolution of 9 LP/mm from an x-ray illumination source. Better than 2,000:1 dynamic range and shot-noise limited operation is achieved. Direct x-ray detection and attendant noise is minimized via the phosphor and epitaxial layer that lies beneath the pixel array. The imager/module architecture and electro-optical performance are described in detail here in.
Nine imagers that exploit distinctive CID properties and incorporate on-chip amplifier configurations (including preamplifier/pixel) were developed for use in automation, nuclear and scientific applications. TV compatible (11 mm) formats of 768<SUB>H</SUB> X 575<SUB>V</SUB> (European) and 755<SUB>H</SUB> X 484<SUB>V</SUB> (domestic-RS170) were fabricated for radiation- hardened product cameras. Operating CIDs provided excellent signal-to-noise at radiation levels of 10<SUP>6</SUP> rads/hr, and accumulated dose beyond 10<SUP>6</SUP> rads in silicon (<SUP>60</SUP>Co source). Large format imagers featuring random pixel and subarray addressability, were created for spectroscopy and other scientific applications. They possess a 27 X 27 micrometers <SUP>2</SUP> pixel in 1024<SUB>H</SUB> X 1024<SUB>V</SUB>, 1024<SUB>H</SUB> X 256<SUB>V</SUB>, and 512<SUB>H</SUB> X 512<SUB>V</SUB> formats. Pixels and subarrays (even overlapping subarrays) can be read out destructively or non-destructively. The above features can be combined with 2D on- CID pixel binning because CID binning preserves the spatial fidelity of the pixel charge. Two 1024 linear-type imagers were fabricated with a preamplifier-per-pixel structure and a 27 X 150 micrometers <SUP>2</SUP> large capacity photo-site. One device features on-chip large signal differencing capability between successive exposures. Two 512<SUB>H</SUB> X 512<SUB>V</SUB> (20 X 20 micrometers <SUP>2</SUP> pixel) format imagers were created for UV photon-counting applications. The imagers provide high local count rates through video-rate random subarray addressability and subarray charge injection.
A new family of binary format CMOS CID imagers was designed to meet the random pixel addressing and on-chip signal manipulation requirements of may scientific applications. Key features include true random pixel and programmable subarray addressing, non-destructive readout and charge injection (clearing) that eliminate the need to read out superfluous pixels. And, programmable horizontal/vertical binning provides improved signal/noise and permits spatial signal consolidation even when reading out overlapping subarrays. The imagers incorporate on-chip preamplifiers for low noise readout. Inherent CID pixel characteristics such as non-destructive, non-blooming read-out that permit adaptive exposure control and linear dynamic range extension are maintained. Formats include 1024<SUP>2</SUP>, 512<SUP>2</SUP>, and 1024 X 256. All incorporate 27.0 micron contiguous square pixels with in excess of 10<SUP>6</SUP> electron well capacity. Serial horizontal and vertical input ports are provided to accept the coordinates of the pixel or subarray to be readout. Rapid subarray readout is facilitated via a single pixel advance clock that is used in conjunction with each random access decoder. A description of the architecture, imager operation and application will be presented.
A photon-counting intensified charge injection device (CID) detector is currently in development at the Laboratory for Astronomy and Solar Physics at the Goddard Space Flight Center. Analogous microchannel-plate-intensified CCD detectors have achieved impressive spatial resolution performance in photon-counting operation. Such detectors suffer, however, from a severe limitation on local dynamic range; local event rates must be kept low in order to minimize event overlap at the frame rates achievable for reading out a full CCD. By utilizing a random access CID for the readout stage, we plan to avoid this severe local count rate limitation by virtue of the addressable (rather than serial) readout capability of such a device. Different portions of the detector field can be framed at different rates, as appropriate to the brightness distribution of the scene, maximizing the local count rate limit for a given pixel read rate and event processing capability. A high spatial resolution, high count rate photon counting detector of this type is of interest in a number of applications in space and ground- based astronomy. In this report, we present: (1) the advantages and applications of this kind of detector, (2) remarks on the suitability of different CID architectures, (3) our system design concept, and (4) the status and plans for our fabrication and testing efforts.
Charge Injection Device (CID) array detectors are well suited for the direct imaging with x- ray and particle beams. In common with CCD detectors, CID arrays have been shown to have good spatial resolution and broad spectral response in the visible range. In addition, CID imagers offer unique architectural features which may be particularly applicable to x-ray and particle beams, including exceptionally large pixel charge capacity, non-destructive pixel readout, and random pixel addressibility. These can dramatically extend the dynamic range, eliminate blooming effects, allow monitoring and dynamic adaptation of application exposure in real-time, improve signal-to-noise by repeated readout and permit the readout of small pixel sub-arrays at exceptionally fast rates. In addition CIDs possess extremely good radiation tolerance. Preliminary results of x-ray measurements with CIDs are presented along with a discussion of potential applications utilizing their unique features.
Arrays of silicon sensors arranged in a CCD focal plane architecture have become the detector of choice for astronomical imaging in the 300 nm to 1 micron region. However other focal plane architectures offer attractive additional features such as allowing for random access to, and readout of, any subarray on the chip, and the nondestructive interrogation of the signal level of any pixel. A 512 x 512 pixel array utilizing a Charge Injection architecture that offers such advantages has been tested at liquid nitrogen temperature as to its suitability for use in astronomy. Laboratory tests show that using nondestructive readouts results in a (root)N (where N is the number of readouts) improvements in the noise figure (approximately 20 electrons rms noise after 100 reads). Initial images with a CID-38 of a number of astronomical objects are also presented.
A new European-format CID imager with improved radiation tolerance was developed to meet the operational requirements of the burgeoning international nuclear power generation and waste management markets. Incorporating an inherently radiation tolerant CID architecture fabricated using a new improved radiation resistant process, the imager is designed to survive total dose radiation of more than 10<SUP>6</SUP> rads (gamma-Sl) in environments greater than 10<SUP>5</SUP> rads/hr (gamma-Sl). The imager format is 786 pixels/row by 612 rows mapped into an 11 MM diagonal optical format. The device incorporates an 11.5 micron<SUP>2</SUP> pixel structure that can be read out either in an interlaced CCIR TV compatible or progressive 25 Hz mode. Additionally, the imager incorporates a deep depletion high resistivity structure that makes it suitable for sensing x ray, nuclear as well as E-beam forms of radiation. The CID device design and tooling was completed during 1993. Sample devices were fabricated and tested during late 1993 and early 1994. Preliminary test results together with further imager and camera development plans are included herein.
New low-noise CID imagers are being created to meet the demanding requirements of scientific instrumentation, high-speed tracking and nuclear inspection applications. The imagers incorporate new process technology and/or new low-noise architectures to exploit inherent unique CID features including random pixel addressability, true non-destructive pixel readout (NDRO), two-dimensional windowing (sub-array readout), and exceptional resistance to the effects of ionizing radiation. These CID features enable the user to monitor and dynamically adapt application exposure levels in real-time, reduce noise, and read out small sub-arrays of pixels at exceptionally fast rates. Due to their radiation tolerance characteristics, the devices can operate in harsh radiation environments and actually image (detect) the incoming radiation. Device formats and performance features are summarized.
The performance of a large format (512 X 512, 20.3 mm diagonal) Charge Injection Device (CID) imager which was fabricated for use in spectroscopy, microscopy and other scientific instrumentation applications is reported herein. The device incorporates a large (28 X 28 micron) pixel size and on-chip signal amplification to achieve large full well capacity, low noise and wide dynamic range. As do other CIDs', the device also features a broad spectral response, virtually no blooming, true Non-Destructive Signal Read-Out (NDRO), video skimming and individual pixel address capability. Together, these unique CID features provide the capability to extend the imager dynamic range, achieve real-time signal monitoring and read-out for adaptive exposure control, and achieve lower noise through NDRO signal averaging.
SICam is a low noise microprocessor-based digital instrumentation camera developed to meet the versatile performance requirements of many scientific and automated vision applications. SICam's unique features allow dynamic control and monitoring in imaging applications including analytical measurement, low light imaging, and spectroscopy. Camera performance is optimized around a new large format, low noise, 512 X 512 CID image sensor incorporating square 28 micrometers X 28 micrometers pixels. The LN<SUB>2</SUB> cooled camera outputs 14-bit digital pixel data which can be extracted randomly and non-destructively from individual pixels, multiple sub-arrays, or from the entire imager. CID's have the unique capability to skim accumulated pixel charge and/or non-destructively read pixel information, enabling the system user to monitor events and dynamically adapt application exposure in real- time for the entire array or individual pixels. Non-destructive readout is also used to extend linear dynamic range. The system operates from PC/AT-compatible platforms.
A high-speed 512 X 512 charge injection device with selectable one to four video ports has been developed, fabricated, and tested beyond the designed speed of operation. The imager has four independently controllable video ports allowing for all possible combinations. This is accomplished by having each port hard wired to one out of every four rows sequentially. Each port is selected via a multiplexer in the sequence desired. The horizontal scanner was designed to operate up to 30 MHz. The device was tested at the wafer level to 42 Mhz element rate per port. This element rate allows a maximum of 168 MHz element rate with four ports operating in parallel.
CIDTEC has developed a PC-based instrumentation camera incorporating a preamplifier per row CID imager and a microprocessor/LCA camera controller. The camera takes advantage of CID X-Y addressability to randomly read individual pixels and potentially overlapping pixel subsets in true nondestructive (NDRO) as well as destructive readout modes. Using an oxy- nitride fabricated CID and the NDRO readout technique, pixel full well and noise levels of approximately 1*106 and 40 electrons, respectively, were measured. Data taken from test structures indicates noise levels (which appear to be 1/f limited) can be reduced by a factor of two by eliminating the nitride under the preamplifier gate. Due to software programmability, versatile readout capabilities, wide dynamic range, and extended UV/IR capability, this camera appears to be ideally suited for use in spectroscopy and other scientific applications.