Skip to main content Accessibility help
×
Home
  • Print publication year: 2012
  • Online publication date: December 2012

14 - CCD imaging detectors

from Part IV - From detected photons to the celestial sphere

Summary

Introduction

Charge-coupled devices (CCDs), the standard imagers at all observatories today, consist of integrated circuits made through the same process as computer memory or the chips in cell phones. Complementary metal oxide semiconductors (CMOS) are an alternative image-sensor technology with high noise immunity and low static power consumption; however, CCDs are the dominant imagers today, so we will concentrate our discussion on their use.

Silicon crystals are sensitive to light through the process by which incident photons of sufficient energy can excite electrons into the valence levels of the atom. Photons with energies less than the valence levels fail to create photoelectrons and are therefore not detected, while the higher-energy photons are absorbed near the surface of the silicon layer before creating usable photoelectrons. If one applies a voltage to the silicon in a controlled manner, these photoelectrons can be either held in place (during the integration) or moved through the silicon lattice (during readout) and collected.

What is a charge-coupled device?

When a CCD is constructed, a square grid of microscopic electrodes called gates is fabricated on the surface of a silicon wafer (see Fig. 14.1). The orthogonal axes of the grid are called columns and rows and the grid elements are the pixels, which have typical sizes of 10–20 üm. When exposed to optical light, the silicon substrate reacts to each absorbed photon by creating one photoelectron–hole pair. The gate voltages control the movement and position of these photoelectrons.

Related content

Powered by UNSILO
References
Auer, L. H. and van Altena, W. F. (1978). Digital image centering. II. AJ, 83, 640.
Bertin, E. and Arnouts, S. (1996). SExtractor: software for source extraction. A&AS, 117, 393.
Biretta, J. (2005). WFPC2 status and calibration. In The 2005 HST Calibration Workshop, ed. A. M., Koekemoer, P., Goudfrooij, and L. L., Dressel. Baltimore, MD: Space Telescope Science Institute.
Chromey, F. R. and Hasselbacker, D. A. (1996). The flat sky: calibration and background uniformity in wide field astronomical images. PASP, 108, 944.
Diego, F. (1985). Stellar image profiles from linear detectors and the throughput of astronomical instruments. PASP, 97, 1209.
Everett, M. and Howell, S. B. (2001). A technique for ultrahigh-precision CCD photometry. PASP, 113, 1428.
Gilliland, R. L., Brown, T. M., Kjeldsen, H., et al. (1993). A search for solar-like oscillations in the stars of M67 with CCD ensemble photometry on a network of 4 M telescopes. AJ, 106, 2441.
Goudfrooij, P., Bohlin, R., Máýz-Apellániz, J., and Kimble, R. (2006). Empirical corrections for charge transfer inefficiency and associated centroid shifts for STIS CCD observations. PASP, 118, 1455.
Howell, S. B. (1989). Two-dimensional aperture photometry – signal-to-noise ratio of point-source observations and optimal data-extraction techniques. PASP, 101, 616.
Howell, S. B. (1992). Astronomical CCD observing and reduction techniques. ASP Conf. Ser., 23, 345.
Howell, S. B. (2006). Handbook of CCD Astronomy, 2nd edn. Cambridge: Cambridge University Press.
Janesick, J. (2001). Scientific Charge-Coupled Devices. Bellingham, WA: SPIE Press.
King, I. (1983). Accuracy of measurement of star images on a pixel array. PASP, 95, 163.
Kozhurina-Platais, V., Goudfrooij, P. and Puzia, T. H. (2007). ACS/WFC: Differential CTE Corrections for Photometry and Astronomy from Non-Drizzled Images. Space Telescope Science Institute, Instrument Science Report ACS 2007-04d.
Lee, J.-F. and van Altena, W. F. (1983). Theoretical studies of the effects of grain noise on photographic stellar astrometry and photometry. AJ, 88, 1683.
Lindegren, L. (2010). High-accuracy positioning: astrometry. In Observing Photons in Space, ed. M. C. E., Huber, A., Pauluhn, J. L., Culhane, J. G., Timothy, K., Wilhelm, and A., Zehnder. ESA/ISSI, ISSI Scientific Reports Series, 279.
Mackay, C. (1986). Charge-coupled devices in astronomy. Ann. Rev. Astron. Astr., 24, 255.
Merline, W. and Howell, S. B. (1995). A realistic model for point-sources imaged on array detectors: the model and initial results. Exp. Ast., 6, 163.
Neeser, M. J., Sackett, P. D., De Marchi, G., and Paresce, F. (2002). Detection of a thick disk in the edge-on low surface brightness galaxy ESO 342-G017. I. VLT photometry in V and R bands. A&A, 383, 472.
Newberry, M.V. (1991). Signal-to-noise considerations for sky-subtracted CCD data. PASP, 103, 122.
Newberry, M. V. (1994). The signal-to connection. CCD Astron., 1, No. 2/Summer, 34.
Sterken, C. (2007). The future of photometric, spectrophotometric, and polarimetric standardization. ASP Conf. Series, 364.
Stetson, P. (1987). DAOPHOT – A computer program for crowded-field stellar photometry. PASP, 99, 191.
Stetson, P. (1998). On the photometric consequences of charge-transfer inefficiency in WFPC2. PASP, 110, 1448.
Zacharias, N., Urban, S. E., Zacharias, M. I., et al. (2000). The First US Naval Observatory CCD Astrograph Catalog. AJ, 120, 2131.
Zhou, X., Burstein, D., Byun, Y. I., et al. (2004). Dome-diffuser flat-fielding for Schmidt telescopes. AJ, 127, 3642.