Showing papers on "High dynamic range published in 1986"
01 Feb 1986
TL;DR: In this paper, an interferometric radio-frequency spectrum analyser based on two surface-acoustic-wave (SAW) Bragg cells illuminated by a semiconductor laser is reported.
Abstract: The development and characterisation of an interferometric radio-frequency spectrum analyser based on two surface-acoustic-wave (SAW) Bragg cells illuminated by a semiconductor laser are reported. The local oscillator reference waveform is generated by a repetitive 31 bit pseudorandom noise sequence driven at 250 Mbit/s, biphase modulated onto a suitable carrier. Spectrum-analyser measurements demonstrate a channelisation accuracy of 8 MHz and a two-signal resolution of approximately 16 MHz. For a collimated laser power of 11 mW, a dynamic range of 53 dB has been achieved for signal pulses with 100 ns duration.
5 citations
TL;DR: In this article, a variable parameter mode of digital image acquisition was developed for secondary ion image depth profiling (IDP), which substantially extended the dynamic range of the IDP technique by automatically optimizing the detector gain and acquisition time for each individual image.
Abstract: A variable parameter mode of digital image acquisition was developed for secondary ion image depth profiling (IDP). The new method substantially extends the dynamic range of the IDP technique by automatically optimizing the detector gain and acquisition time for each individual image. Postacquisition processing of IDP’s allows generation of local area depth profiles (LADP’s) from areas ranging in size from 1 μm2 to the entire image field. Detection limits of LADP’s using the entire image field are within a factor of 2–3 of those obtained using conventional pulse‐counting electron multiplier detection. The lowest detectable signal is limited by camera noise to approximately ten secondary ions per second. A LADP from a 1 μm2 area with a dynamic range of four orders of magnitude was achieved using the variable parameter mode.
3 citations
01 Oct 1986
TL;DR: In this article, the state of AO Bragg cell technology is discussed and the very important area of device modelling is reviewed and it is shown that certain acoustic modes may be preferred for high dynamic range applications.
Abstract: In this paper the state of AO Bragg cell technology is discussed and the very important area of device modelling is reviewed. It is shown that certain acoustic modes may be preferred for high dynamic range applications. The design and analysis of phased array transducers is also discussed and the mathematical formalism is generalized. Some experimental results using RF sputtered ZnO film transducers are presented.
1 citations
TL;DR: In this article, the design, operation, and performance of an imaging photon counting system (designated Foton), with a 500 × 488 pixel format and 33 ms time resolution, are described.
Abstract: The design, operation, and performance of an imaging photon-counting system (designated Foton), with a 500 x 488 pixel format and 33 ms time resolution, are described. The system's detector is a two-stage microchannel intensifier fiber-optically coupled to a CCD camera operating at standard video rate. With an extended red S-20 photocathode the detector is sensitive from 2000 A to 9000 A, with a peak quantum efficiency of 15 percent at 5000 A. As all photon events are permanently recorded, it is possible to produce sequences of short-exposure images, so that periodic or rapidly varying phenomena may be studied. The principal advantages of the system, which can be used for spatially resolved spectroscopy and narrow-band imaging at a wide range of signal-to-noise levels, as well as for speckle observations, are its small size and weight, large image format, and high dynamic range. Block diagrams are included.
1 citations
TL;DR: In this article, a Cinecharge-coupled device (CCD) was used for increasing the spatial resolution of the 1-and 2-m telescopes of the Pic-du-Midi observatory.
Abstract: Publisher Summary This chapter describes a new camera especially designed for the 1- and 2-m telescopes of the Pic-du-Midi observatory. This camera is used for increasing the spatial resolution on long equivalent exposures and for multiaperture photometric experiments. In astronomy, for long exposures, the images are blurred by tracking defects of the telescope and by image motion due to atmospheric wavefront tilt. Without employing speckle techniques, it is, however, possible to freeze the quality of images by using a detector allowing short and consecutive exposures. By addition of selected images after a recentering procedure, an equivalent long exposure can be obtained with the selected quality. Such a technique may be employed in photography where the addition of several plates increases the signal-to-signal ratio. Using a “Cine-charge-coupled device (CCD)” mode is a better solution retaining the advantage of CCD properties: linearity, stability of geometry and noise statistics, good sensitivity, and high dynamic range. The possibilities of a “Cine-CCD” mode have been investigated through observational tests on the telescope. It is possible to substantially increase the resolution and obtain good photometric results on objects whose brightness corresponds to some tenths of the readout noise per pixel, with a bare CCD.