Improving the sensitivity of silicon-based CMOS and CCD in the deep-UV is an area of ongoing interest. Lumogen has been used for this purpose for many years but has several known issues including limitations to its use in both vacuum and radiation harsh environments. Quantum Dots (QD) offers a more robust alternative to Lumogen. The fluorescence wavelength of QDs is tunable and can be fabricated to match the peak sensor quantum efficiency. Aerosol jet printing (AJP) is being used for the deposition of QDs on a variety of substrates and on commercially available sensor arrays. While the films deposited onto various substrates have a surface morphology characterized by aggregate formations, the insight obtained will lead to much more uniform layers in the near future. Organic residues common to this process, that compromise the UV performance, have been minimized.
Charge Injection Device technology has been widely used in radiation applications. Although the technology has excelled in ground applications that have been predominantly for radiation effects using gamma radiation, a Thermo Scientific CID8725D radiation hardened camera with CID imager has now been tested for effects due to proton and heavy ion irradiation to investigate viability for use in space applications.
A technique has been developed for coating commercial off the shelf (COTS) detector arrays with a thin, uniform layer
of quantum dots. The quantum deposition is accomplished using an Optomec Aerosol Jet rapid prototyping system.
When illuminated by UV andvacuumUV (VUV) the quantum dots will fluoresce and those emitted photons will be
detected by the underlying detector array. The size of the quantum dots used determines the fluorescence wavelength and
that would be matched to the peak sensitivity of the underlying detector array. The devices have been tested at the NIST
synchrotron facility in Gaithersburg and have shown sensitivity down to 150nm. Performance at wavelengths below
150nm is limited by absorption by solvent residues from deposition process.
The attributes of the scientific-grade 4k linear CID51 sensor are presented. The CID51 sensor is fabricated
using 0.18 μm technology. The 0.18 μm design rules permit proximity-coupling of the two photogates within the pixel
required for non-destructive readout of the charge. The 14 μm by 50 μm pixels are arranged on two evenly staggered
2080-pixel rows. The result is a randomly addressable 4160 pixel array with an effective pitch of 7 microns and an
effective height of 100 microns. The sensor incorporates parallel pixel processing with on-chip correlated double
sampling. The critical unique feature of the CID51 is the 32 analog row storage registers (RSR) per pixel. These RSRs
allow for the time resolved sampling of the 4160 pixel spectrum and can be randomly read out at rates as high as 8 MHz.
The signal storage of up to 32 samples per pixel is non-destructive allowing for the integration of spectroscopic events
with unprecedented microsecond time resolution. Alternatively, because pixels can be randomly accessed for readout or
reset, intensely illuminated pixels can be quantitatively sampled and rapidly cleared of photon-generated charge, while
weakly illuminated pixels are simultaneously allowed to integrate. Thus, the effective integration time can be varied
from pixel to pixel based upon the observed photon flux vastly expanding dynamic range. Full spectrum acquisition
provides all of the spectral content, including background continuum information for accurate photometry and spectrum
to spectrum calibration. The CID51 device is suited for scientific applications demanding high dynamic range and/or
time resolved capabilities.
The revolutionary charge-coupled device (CCD) was first described by George Smith and Willard Boyle of Bell
Laboratories in 1969. Hubert Burke and Gerald Michon of General Electric (GE) followed with the invention of the
charge-injection device (CID) in 1973. In the 1970s and 1980s, CID-based cameras were widely used in machine vision
applications. By the 1990s, as CMOS sensors were gaining popularity, CIDs were adapted for applications demanding
high dynamic range and superior antiblooming performance. CID-based cameras have found their niche in applications
requiring extreme radiation tolerance and the high dynamic range scientific imaging. CID imagers have progressed from
passive pixel designs using proprietary silicon processes to active pixel devices using conventional CMOS processing.
Scientific cameras utilizing active pixel CID sensors have achieved a factor of 7 improvement in read noise (30 electrons
(rms) versus 225 electrons (rms)) at vastly increased pixel frequencies (2.1 MHz versus 50 kHz) when compared to
passive pixel devices. Radiation-hardened video cameras employing active pixel CIDs is the enabling technology in the
world's only solid-state radiation-hardened color camera, which is tolerant to total ionizing radiation doses of more than
5 Mega-rad. Performance-based CID imaging concentrates on leveraging the advantages that CIDs provide for
The charge injection device, CID25, is presented. The CID25 is a color video imager. The imager is compliant with the NTSC interlaced TV standard. It has 484 by 710 displayable pixels and is capable of producing 30 frames-per-second color video. The CID25 is equipped with the preamplifier-per-pixel technology combined with parallel row processing to achieve high conversion gain and low noise bandwidth. The on-chip correlated double sampling circuitry serves to reduce the low frequency noise components. The CID25 is operated by a camera system consisting of two parts, the head assembly and the camera control unit (CCU). The head assembly and the CCU can be separated by up to 150 meter long cable. The CID25 imager and the head portion of the camera are radiation hardened. They can produce color video with insignificant SNR degradation out to at least 2.85 Mrad of total dose of Co<sup>60</sup> γ-radiation. This represents the first in industry radiation hardened color video system, based on a semiconductor photo-detector that has an adequate sensitivity for room light operation.
A scientific camera system having high dynamic range designed and manufactured by Thermo Electron for scientific and medical applications is presented. The newly developed CID820 image sensor with preamplifier-per-pixel technology is employed in this camera system. The 4 Mega-pixel imaging sensor has a raw dynamic range of 82dB. Each high-transparent pixel is based on a preamplifier-per-pixel architecture and contains two photogates for non-destructive readout of the photon-generated charge (NDRO). Readout is achieved via parallel row processing with on-chip correlated double sampling (CDS). The imager is capable of true random pixel access with a maximum operating speed of 4MHz. The camera controller consists of a custom camera signal processor (CSP) with an integrated 16-bit A/D converter and a PowerPC-based CPU running a Linux embedded operating system. The imager is cooled to -40C via three-stage cooler to minimize dark current. The camera housing is sealed and is designed to maintain the CID820 imager in the evacuated chamber for at least 5 years. Thermo Electron has also developed custom software and firmware to drive the SpectraCAM SPM camera. Included in this firmware package is the new Extreme DR<sup>TM</sup> algorithm that is designed to extend the effective dynamic range of the camera by several orders of magnitude up to 32-bit dynamic range. The RACID Exposure graphical user interface image analysis software runs on a standard PC that is connected to the camera via Gigabit Ethernet.