Zoran Ninkov

SUBPIXEL SENSITIVITY MAP FOR A CHARGE-COUPLED DEVICE SENSOR

The sensitivity across a solid state detector array varies as a result of differences in transmission, diffusion and scattering properties over the sensor. This variation will occur over a range of scale lengths and its knowledge is of importance for improved device design and in a variety of applications, for example, event centroiding in photon counting systems. A measurement of the sensitivity variation on a subpixel scale for a two-phase front-illuminated CCD is reported. The measurement is made using a scanning reflection microscope. A variation in sensitivity between the phases within a pixel is clearly observed, as well as varia- tions on a much smaller spatial scale.

Characterization of a digital micromirror device for use as an optical mask in imaging and spectroscopy

The digital micromirror device (DMD) is a micro-optical- electro-mechanical structure consisting of an array of 16 micrometers X 16 micrometers square mirrors positioned on a 17 micrometers pitch. Each individual mirror can be tilted +/- 10 degrees relative to the DMD substrate; the tilt is along the diagonal direction of the micromirror. The device was invented and manufactured by Texas Instruments (TI), Inc. TI packages the DMD as an OEM product for use in projection displays. We are investigating the use of the DMD as a spatial light modulator for precision imaging and spectroscopy applications. This includes optical characterization of the device, as well as systems engineering to operate the device. Some of the performance metrics to be considered are the diffraction efficiency, optical-switching contrast, background scattering properties, mirror crosstalk, and the modulation transfer function.

The Vulcan Photometer: A Dedicated Photometer for Extrasolar Planet Searches

A small CCD photometer dedicated to the detection of extrasolar planets has been developed and put into operation at Mount Hamilton, California. It simultaneously monitors 6000 stars brighter than 13th magnitude in its 49 deg 2 field of view. Observations are conducted all night every clear night of the year. A single field is monitored at a cadence of eight images per hour for a period of about 3 months. When the data are folded for the purpose of discovering low-amplitude transits, transit amplitudes of 1% are readily detected. This precision is sufficient to find Jovian-size planets orbiting solar-like stars, which have signal amplitudes from 1% to 2% depending on the inflation of the planets atmosphere and the size of the star. An investigation of possible noise sources indicates that neither star field crowding, scintillation noise, nor photon shot noise are the major noise sources for stars brighter than visual magnitude 11.6. Over one hundred variable stars have been found in each star field. About 50 of these stars are eclipsing binary stars, several with transit amplitudes of only a few percent. Three stars that showed only primary transits were examined with high-precision spectroscopy. Two were found to be nearly identical stars in binary pairs orbiting at double the photometric period. Spectroscopic observations showed the third star to be a high mass ratio single-lined binary. On 1999 November 22 the transit of a planet orbiting HD 209458 was observed and the predicted amplitude and immersion times were confirmed. These observations show that the photometer and the data reduction and analysis algorithms have the necessary precision to find companions with the expected area ratio for Jovian-size planets orbiting solar-like stars.

Interpixel capacitance in nondestructive focal plane arrays

Inter-pixel capacitive coupling can exist in a non-destructive detector array if the detector nodes change voltage as they integrate charge and the design of the device allows for an electric field to exist between adjacent collection nodes. Small amounts of inter-pixel capacitance can cause large errors in the measurement of poissonian noise versus signal, and all subsequently derived measurements such as nodal capacitance and quantum efficiency. Crosstalk and MTF can also be significantly influenced by interpixel capacitance. Two 1k by 1k Raytheon SB226-based hybridized silicon PIN arrays were tested for nodal capacitance and MTF. Initial results indicated unexpected and unexplainably large nodal capacitance, poor MTF, and odd edge spread. It was hypothesized that inter-pixel capacitive coupling was responsible for these discrepancies. A stochastic method of measuring the coupling using 2D autocorrelation and Fourier Transform techniques was devised and implemented. Autocorrelation of the shot noise in the images revealed a correlation consistent with 3.2% interpixel capacitive coupling. When the effects of the measured interpixel capacitance were taken into account, the initially measured nodal capacitance of 56 fF was found to be 31% higher than the corrected nodal capacitance measurement of 43 fF. Large discrepancies between the theoretical and observed edge spread response were also greatly reduced. A simulation of the electric field in the PIN detector intrinsic region predicted an interpixel coupling very close to the observed coupling. Interpixel capacitance was also observed in a 2k by 2k Raytheon SB304-based InSb detector array, but was not strongly evident in a bare Raytheon SB226 multiplexer.

Speckle observations of binary stars with the WIYN Telescope. II. Relative astrometry measures during 1998-2000

Five hundred twelve relative astrometry measures are presented for 253 double stars, including 53 double stars discovered by Hipparcos. In 15 cases, relative astrometry is reported for the first time for newly confirmed pairs. In addition, 20 high-quality nondetections of companions are reported for stars suspected of being nonsingle by Hipparcos. Observations were taken using a fast-readout CCD camera system at the WIYN 3.5 m telescope at Kitt Peak, Arizona. In comparing these measures with ephemeris predictions for binary stars with very well known orbits, we find that the measurement precision is better than 3 mas in separation and 1° in position angle per individual observation. Measurement precision and detection capabilities are fully discussed, and confirmed orbital motion is reported in four cases of the Hipparcos double star discoveries.

Imaging of laser--plasma x-ray emission with charge-injection devices

This work details the method of obtaining time-integrated images of laser–plasma x-ray emission using charge-injection devices (CIDs), as has been demonstrated on the University of Rochester’s 60-beam UV OMEGA laser facility [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. The CID has an architecture similar to a charge-coupled device. The differences make them more resistant to radiation damage and, therefore, more appropriate for some application in laser–plasma x-ray imaging. CID-recorded images have been obtained with x-ray pinhole cameras, x-ray microscopes, x-ray spectrometers, and monochromatic x-ray imaging systems. Simultaneous images obtained on these systems with calibrated x-ray film have enabled determination of the absolute detection efficiency of the CIDs in the energy range from 2 to 8 keV.

Speckle Observations of Binary Stars with the WIYN Telescope. I. Measures During 1997

Two hundred seventy-seven position angle and separation measures of 154 double stars are presented. Three of the systems were previously unknown to be double, and 16 other systems were discovered earlier this decade by the Hipparcos satellite. Measures are derived from speckle observations taken with the Wisconsin-Indiana-Yale-NOAO (WIYN) 3.5 m telescope located at Kitt Peak, Arizona. Speckle images were obtained using two different imaging detectors, namely, a multianode microchannel array (MAMA) detector and a fast-readout CCD. A measurement precision study was performed on a sample of binaries with extremely well known orbits by comparing the measures obtained here to the ephemeris predictions. For the CCD, the root mean square (rms) deviation of residuals was found to be 3.5 milliarcseconds (mas) in separation and 12 in position angle, while the residuals of the MAMA data varied depending on the magnification used and seeing conditions but can be comparable or superior to the CCD values. In addition, the two cameras were compared in terms of the detection limit in total magnitude and magnitude difference of the systems under study. The MAMA system has the ability to detect some systems with magnitude differences larger than 3.5, although reliable astrometry could not be obtained on these objects. Reliable astrometry was obtained on a system of magnitude difference of 5.3 with the CCD system.

Subpixel sensitivity maps for a back-illuminated charge-coupled device and the effects of nonuniform response on measurement accuracy

A measurement program designed to investigate the varia- tions in sensitivity of focal plane arrays on a subpixel scale has produced such information for a front-illuminated CCD device, results for which have been previously presented. New measurements have been made to provide information on sensitivity variations within a single pixel for a back-illuminated CCD. The measurements were made using a stable broadband light source and two high-precision translation stages. The pixel scans were obtained using four different spectral filters (three broadband and one narrowband). These results are compared to the pixel response functions of the front-illuminated CCD. These experimen- tally measured pixel response functions were used to determine their effect on photometric and astrometric measurements. The uncertainty introduced into such measurements, especially when using under- sampled CCD data, is significant. It was also found that the form of the subpixel response is dependent on the wavelength of illuminating light. Therefore, the position of the optical center of weight of a pixel varies with wavelength.

SpecTIR hyperspectral airborne Rochester experiment data collection campaign

A multi-modal (hyperspectral, LiDAR, and multi-spectral) imaging data collection campaign was conducted at the Rochester Institute of Technology (RIT) in conjunction with SpecTIR, LLC, in the Rochester, New York, area July 26-29, 2010. The campaign was titled the SpecTIR Hyperspectral Airborne Rochester Experiment (SHARE) and collected data in support of nine simultaneous unique experiments, several of which leveraged data from multiple modalities. Airborne imagery was collected over the city of Rochester with hyperspectral, multispectral, and Light Detection and Ranging (LiDAR) sensors. Sites for data collection included the Genesee River, sections of downtown Rochester, and the RIT campus. Experiments included sub-pixel target detection, water quality monitoring, thermal vehicle tracking and wetlands health assessment. An extensive ground truthing effort was accomplished in addition to the airborne imagery collected. The ultimate goal of this comprehensive data collection campaign was to provide a community sharable resource that would support additional experiments. This paper details the experiments conducted and the corresponding data that were collected in conjunction with this campaign.

CCD SPECKLE OBSERVATIONS OF BINARY STARS FROM THE SOUTHERN HEMISPHERE.

Two hundred seventy-two magnitude diUerence measures of 135 double star systems are presented. The results are derived from speckle observations using the Bessel V and R passbands and a fast readout CCD camera. Observations were taken at two 60 cm telescopes, namely the Helen Sawyer Hogg Telescope, formerly at Las Campanas, Chile, and the Lowell-Tololo Telescope at the Cerro Tololo InterAmerican Observatory, Chile. The data analysis method is presented and, in comparing the results to those of Hipparcos as well as to recent results using adaptive optics, we —nd very good agreement. Overall, the measurement precision appears to be dependent on seeing and other factors but is generally in the range of 0.10¨0.15 mag for single observations under favorable observing conditions. In four cases, multiple observations in both V and R allowed for the derivation of component V [R colors with uncertainties of 0.11 mag or less. Spectral types are assigned and preliminary eUective temperatures are estimated in these cases.