Application of CMOS image sensors with non-destructive readout capability have several advantages over current CCD sensors in detecting Near-Earth Objects (NEOs). They include detection of temporal changes, cosmic ray rejection, no charge blooming, expanded dynamic range, and lower dark current. Since wide field survey usually requires large mosaics, a “rolling shutter” operation simplifies the challenge of large mechanical shutters. Being able to readout parts of the field in destructive mode offers the possibility of providing guiding feedback to the telescope during exposure. We have carried out preliminary testing of a prototype CMOS camera built by Spectral Instruments Inc. on a one-meter telescope on Mt. Lemmon, Arizona as applied to rapidly moving NEOs. We have also demonstrated “post facto” guiding on a known NEO that significantly improves the signal to noise.
An experimental camera system equipped with a novel CMOS image sensor suitable for ground-based astronomy that has both destructive and non-destructive readout capability will be described and the performance characteristics including readout noise, dark current, quantum efficiency, will be given. The optimum data collection algorithms to achieve reduced effective readout noise, cosmic ray rejection, and expanded dynamic range will be described. The ability to use destructive readout in select rows to acquire data for telescope guiding while the main part of the sensor is read using non-destructive readout for main image acquisition will be discussed.
This paper covers the preliminary design of a radiation tolerant nanosecond-gated multi-frame CMOS camera system for
use in the NIF. Electrical component performance data from 14 MeV neutron and cobalt 60 radiation testing will be
The recent development of nanosecond-gated multi-frame hybrid-CMOS (hCMOS) focal plane arrays by the Ultrafast
X-ray Imaging (UXI) group at Sandia National Lab has generated a need for custom camera electronics to operate in the
pulsed radiation environment of the NIF target chamber. Design requirements and performance data for the prototype
camera system will be discussed. The design and testing approach for the radiation tolerant camera system will be
covered along with the evaluation of commercial off the shelf (COTS) electronic component such as FPGAs, voltage
regulators, ADCs, DACs, optical transceivers, and other electronic components. Performance changes from radiation
exposure on select components will be discussed. Integration considerations for x-ray imaging diagnostics on the NIF
will also be covered.
The Static X-Ray Imager (SXI) is a National Ignition Facility (NIF) diagnostic that uses a CCDcamera to record timeintegrated
X-ray images of target features such as the laser entrance hole of hohlraums. SXI has two dedicated
positioners on the NIF target chamber for viewing thetarget from above and below, and the X-ray energies of interest are
870 eV for the “soft” channel and 3 – 5 keV for the “hard” channels. The original cameras utilize a large formatbackilluminated
2048 x 2048 CCD sensor with 24 micron pixels. Since the original sensor isno longer available, an effort
was recently undertaken to build replacement cameras withsuitable new sensors. Three of the new cameras use a
commercially available front-illuminatedCCD of similar size to the original, which has adequate sensitivity for the hard
X-ray channelsbut not for the soft. For sensitivity below 1 keV, Lawrence Livermore National Laboratory (LLNL) had
additional CCDs back-thinned andconverted to back-illumination for use in the other two new cameras. In this paper we
describethe characteristics of the new cameras and present performance data (quantum efficiency, flat field, and dynamic
range) for the front- and back-illuminated cameras, with comparisons to the originalcameras.
The Observatorio Astrofísico de Javalambre (OAJ) is a new astronomical facility located at the Sierra de Javalambre (Teruel, Spain) whose primary role will be to conduct all-sky astronomical surveys. The OAJ facility will have two wide-field telescopes: the JST/T250; a 2.55-m telescope with a 3° diameter field of view (FoV), and the JAST/T80; an 0.83-m telescope with a 2° diameter FoV. First light instrumentation is being designed to exploit the survey capabilities of the OAJ telescopes. This paper describes the T80Cam, a wide-field camera that will be installed at the Cassegrain focus of the JAST/T80. It is equipped with an STA 1600 backside illuminated detector. This is a 10.5k-by-10.5k, 9μm pixel, high efficiency CCD that is read from 16 ports simultaneously, allowing read times of ~20s with a typical read noise of 6 electrons (rms). This full wafer CCD covers a large fraction of the JAST/T80’s FoV with a pixel scale of ~0.50"/pixel. T80Cam will observe in the wavelength range 330-1000nm through a set of 12 carefully optimized broad-, intermediate- and narrow-band filters. The camera is intended for surveys with the JAST/T80 telescope, starting with the planned J-PLUS (Javalambre Photometric Local Universe Survey), a multi-band photometric all-sky survey that will be completed in about 2 years and will reach AB∼ 23 mag (5σ level) with the SDSS filters.
Ludwig-Maximilians-Universit¨at M¨unchen operates an astrophysical observatory on the summit of Mt. Wendelstein1
which will be equipped with a modern 2m-class, robotic telescope.2 One Nasmyth port of the new
Fraunhofer telescope is designed to sustain the excellent (< 0.8" median) seeing of the site [1, Fig. 1] over a FOV
of 0.2 deg2 utilizing three-element transmissive field corrector optics for optical wavebands. It will be equipped
with a camera built around a customized 64 MPixel Mosaic (Spectral Instruments, 4 × (4k)2 15μm e2v CCDs).
TheWendelsteinWide Field Imager has two filter wheels with eight slots each (SDSS3 [ugriz] + eight still free)
as well as two off-axis guiding units (two FLI Microline with 2k Fairchild CCDs on differential focus stages). A
Bonn Shutter4 ensures high precision photometric exposures. An option to either insert a low dispersion grating
(for field spectroscopy) or support a wave front sensor probe allows for further expansion of the camera. EMI-safe
housing has to overcome the emission of a close by 0.5MW radio station. Special care has been taken to design
a very low ghost budget of the overall system to allow for low-surface brightness applications (e.g. weak lensing
Linear charge coupled device (CCD) array detectors designed for use in document scanning applications have been proven to be useful as array spectroscopic detectors in some instances. The principles of operation, device architecture, and general characteristics of several common low-cost linear array CCD detectors as they pertain to use as spectroscopic detectors are described. In particular, the readout noise, quantum efficiency, low light level linearity and charge transfer characteristics, and charge capacity as it affects absorbance and fluorescence spectroscopic measurements are discussed.
A thinned-CCD mosaic was fabricated from four Loral 2048 X 2048 edge-buttable CCDs. Thinning was performed on the whole wafer with subsequent dicing and handling facilitated by bonding the thinned wafer to a glass plate. Packaging of the devices involved a `flip-chip' wire-bonding technique followed by chemical dissolution of the glass support. The fabrication process was designed to minimize the gaps between devices and retain a high degree of flatness in the finished CCDs.
A transparent, semi-solid, electrolytic gate has been applied to the backside of thinned CCDs for quantum efficiency enhancement. The gate is applied by spreading a water solution of phosphoric acid and polyvinyl alcohol onto the silicon and drying it to form a thin plastic film. When a negative voltage of less than one volt with respect to substrate ground is applied to the gate, a QE pinned condition (100% internal quantum efficiency) is produced. An insulating layer is not needed with this gate (as it is with electronic conductors) since a threshold voltage of about 1.2 V is required before conduction into the silicon can occur. The mechanism of charging is believed to involve a pile-up of negative ions at the silicon-electrolyte interface which compensates for the positive oxide charge. Conduction into the silicon at low voltages is restricted by the oxidation potential of the negative ions in the electrolyte.
CCD signal processing schemes attempt to reduce the
effect of (KTC), 1/f, and broadband noise on the output signal. A number of schemes have been reported over the years. These schemes employ time delay and subtraction to eliminate KTC noise and attenuate 1/f noise. They also include a low-pass function to
reduce the effect of broadband noise. Signal processing schemes include dual-slope integration, correlated-double sampling, a variation of correlated-double sampling referred to as switchedexponential
filtering, and transversal filters. Signal processing that does not use delay and subtraction to eliminate KTC noise is also discussed. A consistent technique is used to analyze the various processing schemes. Transfer functions for signal and noise are presented
for each. Performance comparisons are given with emphasis on their applicability to relatively high speed CCD readout applications (readout rates of 1 Mpixel/s and faster).
A low cost dual speed CCD imaging system is described. System design and implementation issues are discussed. Emphasis is placed on system flexibility and interface considerations. Architectural details of the camera controller unit and signal processing circuitry and preliminary performance data are presented.
The AIS2 is a dual speed multi-port slow-scan CCD imaging system intended for use in applications which require both low speed low noise operation and higher speed setup and acquisition modes. Flexibility in CCD operation is emphasized and all CCD control voltage and timing may be reconfigured through software command. Additionally multi-port CCDs and multi-device CCD mosaics may be supported with separate clock voltage references and timing generators for each CCD or output amplifier. The system is extensible and may be tailored to the individual needs of the application. A high speed programmable timing sequencer generates the CCD clock signals with timing resolution to 25 ns. Virtually any CCD clocking signals may be generated. Timing sequences and clock references for each CCD output port in the system may be separately configured. An adaptable camera system controller accepts high level commands for system operation and image acquisition. The operational parameters and command language may be modified by the user if desired and may be retained from session to session. Reconfiguration of the system to operate a different CCD requires only replacement of one circuit card and downloading a set of modified parameters. The initial version of the system is configured to perform four port operation of a Tektronix 111024 CCD at a 100 kilohertz pixel rate and a 1 megahertz rate at 16 and 12 bit resolution respectively. 1.
Large area CCDs are not in general flat. Deviations from flatness are often greater than that allowed for the focal plane of moderately fast optical systems. We will discuss a technique of vacuum packaging that has allowed CCDs to be packaged with a flatness of better than five microns over a scale of greater than three centimeters. In principle this technique could be used to package a CCD so that the surface has a specific radius of curvature rather than a planar figure (infinite radius). 1.
CCD signal-processing schemes attempt to reduce the effect of KTC, 1/f, and broadband noise on the output
signal. A number of schemes have been reported over the years. These schemes employ time delay and
subtraction to eliminate KTC noise and attenuate 1/f noise. They also include a low-pass function to reduce
the effect of broadband noise. Signal processing schemes include dual-slope integration, double-correlated
sampling, a variation of double-correlated sampling referred to in this paper as "switched exponential filtering,"
and transverse filters.
Transfer functions for signal and noise are presented for each of these schemes. Performance comparisons
are given with emphasis on their applicability to relatively high-speed CCD readout applications (readout rates
of 1 megapixel per second and faster).
Recent technology has produced CCDs with high-output gains in terms of volts per electron. Such devices
feature very small output gate capacitance and hence, reduced KTC noise. Signal processing that does not
use delay and subtraction to eliminate KTC noise is discussed. Again, the emphasis is on applicability to
relatively high-speed readout.
The Advanced Imaging System is a slow scan, high precision CCD camera system designed specifically for low noise image acquisition and precise, highly flexible CCD testing and characterization. In addition, the system is designed to allow CCD mosaics to be supported with separate, programmable clock voltages and output amplifier operating points for each device. A high speed digital signal processor acts as the timing generator and allows all clock voltages and timing states to be adjusted through a set of downloadable parameters. Virtually any CCD can be operated with modest changes to the system hardware and software. In addition, the entire control program may be downloaded from the host computer at any time to facilitate radically different camera operation. The initial version of the camera system supports up to eight separate simultaneous readout channels with readout rates as high as 100 kHz at 16 bit precision and noise levels below 5 e- at 50 kHz. Control and data signals are connected to the host computer through a fiber optic interface for maximum distance and isolation. The system is a highly flexible CCD camera designed to operate individual CCDs and mosaics in slow scan systems where low noise is of primary importance.
A large-format CCD imager is described and tested. The CCD imager incorporates floating diffusion as well as floating gate amplifiers on a 2048 by 2048 format which was employed as the design base. The amplifiers are intended to allow repeated nondestructive read operations on individual pixels in the array. The serial register was separated into two independently clocked halves to permit simultaneous readout of all four quadrants of the imager. Extensive schematic layouts of the base model and modification are given. The results of a performance test are presented, showing good results in the cooling curve for average dark current, and for charge transfer characteristics. The amplifiers are intended to reduce net readout noise, and the simultaneous readout capability is intended to reduce total read time, although neither was fully tested. The large-format CCD imager is of interest for astronomical photography and spectroscopic applications.