Frame Transfer CCDs Research Articles

高帧频低拖尾帧转移CCD驱动技术

高帧频低拖尾帧转移CCD驱动技术

高帧频低拖尾帧转移CCD驱动技术

高帧频低拖尾帧转移CCD驱动技术

MAIA, a three-channel imager for asteroseismology: instrument design

MAIA, an acronym for Mercator Advanced Imager for Asteroseismology, is a three-channel instrument that targets fast-cadence three-colour photometry, installed at the 1.2-m Mercator telescope at the Roque de los Muchachos at La Palma (Canary Islands, Spain). This instrument observes a 9.4x14.1arcmin2 Field-of-View simultaneously in three wavelength bands on three large frame-transfer CCDs. These detectors were developed for ESA's cancelled Eddington space mission and were offered on permanent loan to the Institute of Astronomy (KU Leuven, Belgium). MAIA uses its own ugr photometric system that is a crude approximation of the SDSS system. The instrument is designed to perform multi-colour observations for asteroseismology, with specific emphasis on subdwarf and white dwarf single and binary stars. We describe the design of the instrument, discuss key components, and report on its performance and first results.

Design of a very high frame rate camera based on an asynchronous CCD driving method

A very high frame rate camera is designed based on an innovative CCD driving method. The CCD driving method is mainly implemented on frame transfer CCDs. Asynchronous drive timing sequences are applied in the image and storage section of the CCDs. Several rows of the charge in the image section are binned onto the same row in the storage section, and there are the same number of images to be stored in the storage section before they are read out. Based on the new driving method, the frame transfer CCDs can work at a very high frame rate in acquiring burst images though the reading speed remains at a lower level. A very high frame rate camera is designed in this paper. The innovative CCD driving method is mainly of concern. An e2v's CCD60 is adopted in the camera system, whose full size resolution is 128×128, and the up most frame rate is 1000 Hz in the conventional CCD driving method. By using the presented method, the CCD60 based imager is capable of operating at up to 40000 frames per second (fps) at a recognizable resolution of 128×32. Comparing cameras using traditional binning and region of interest technologies, the frame rate is normally less than 5000 fps while the resolution is only 32×32 left.

On the use of electron-multiplying CCDs for astronomical spectroscopy

Conventional CCD detectors have two major disadvantages: they are slow to read out and they suffer from read noise. These problems combine to make high-speed spectroscopy of faint targets the most demanding of astronomical observations. It is possible to overcome these weaknesses by using electron-multiplying CCDs (EMCCDs). EMCCDs are conventional frame-transfer CCDs, but with an extended serial register containing high-voltage electrodes. An avalanche of secondary electrons is produced as the photon-generated electrons are clocked through this register, resulting in signal amplification that renders the read noise negligible. Using a combination of laboratory measurements with the QUCAM2 EMCCD camera and Monte Carlo modelling, we show that it is possible to significantly increase the signal-to-noise ratio of an observation by using an EMCCD, but only if it is optimised and utilised correctly. We also show that even greater gains are possible through the use of photon counting. We present a recipe for astronomers to follow when setting up a typical EMCCD observation which ensures that maximum signal-to-noise ratio is obtained. We also discuss the benefits that EMCCDs would bring if used with the next generation of extremely large telescopes. Although we mainly consider the spectroscopic use of EMCCDs, our conclusions are equally applicable to imaging.

Frame transfer CCDs for digital still cameras: concept, design, and evaluation

Digital still cameras are becoming a widely used alternative for conventional silver-halide cameras. This paper presents first the concept of frame-transfer CCD imagers designed for consumer digital cameras. Next, the different modes of operation are explained in detail and compared with alternative approaches. Finally, extensive evaluation results on four different imagers using this new concept are presented. It will be demonstrated that the flexible modes of operation, the high dynamic range, and excellent optical properties of FT-CCDs make them very suited for this type of electronic imaging.

A Multiformat HDTV Camera Head

This paper describes the development of a compact and configurable HDTV camera system for various studio and in-field applications, including flexible dockable configurations. A novel way to capture native 1080P, 1080I, and 720P at 16:9 aspect ratio and a CinemaScope aspect ratio in 1080P of 2.37:1 is presented. The architecture of the multiformat HDTV camera head is based on a newly designed frame transfer CCD imager, which enables the availability of the HD-SDI (SMPTE 292M) output at the camera head itself. It utilizes three frame transfer CCDs (2/3 in.) with 9.2 Mpixels each (including overscan). Using a 12-phase system, all the vertical resolutions of the SMPTE 274M and SMPTE 296M standards are possible. These pixels are prearranged into image cells at the CCD by Dynamic Pixel Management software. The image diagonal (11 mm) is independent of spatial resolution and therefore the same for all scanning formats.

DIRECT IMAGING OF FAINT STELLAR COMPANIONS

ABSTRACT The ability of directly detect close, faint companions to bright stars, depends on image sharpness to a high power (6 to 8 in the case of a planet). We present the first observations with a cornographic mode of the high-resolution camera on the CFH 3.6-m telescope. About 98% of the light of the guide star fell through a 5 arcsec hole and the wings of the image were well-represented by a Moffat profile. Chopping in angle did not reduce glare in the wings as much as we expected because of eccentricity of the star in the aperture, residual asymmetry in the point spread function, and weak radial patterns (in addition to those from the spider). Combing an angular chop with the image of another star to give an instrumental psf, was more successful. We discuss the recognition and photometry of a faint star in the field of sigma Dra. Snapshots of Procyon yielded a separation of 5.2 arcsec, mv = 11.3, B-V = +0.26, and B-I = +0.62 for its white dwarf companion. The detection limits close to sigma Dra, tau Cet and epsilon Eri, are still some 5 magnitudes too bright for the detection of giant planets. Nonetheless, we remain optimistic that, with improving centering, the introduction of frame transfer CCDs, longer exposure times in the 15 percentile seeing at CFHT, and the use of other stars to define the telescope psf and fixed speckle background, it may be possible to realize these limits. Alt-azimuth telescopes present a special challenge!.

TV Rate Readout Unit for Two-dimensional CCDs

AbstractA simple circuit has been designed for reading out at TV rate the two-dimensional CCD on the Automated Patrol Telescope. Because it is controlled by a programmable Cathode Ray Tube Controller integrated circuit it is very flexible and applicable to frame transfer CCDs having a wide range of formats.