The research described in this dissertation is the first evaluation of two-dimensional charge coupled devices (CCDs) for low light level analytical spectroscopy. The electro-optical properties of several unique two-dimensional CCDs are evaluated, including quantum efficiency, detector read noise, linearity, dynamic range, dark current, and blooming. Theoretical models describing the sensitivity and dynamic range of CCDs on a single detector element basis are developed. Based on this model and the characteristics of a CCD detector system built for this research, it is shown that a single detector element of a CCD has comparable or superior sensitivity than the most sensitive single channel detectors. The results of the CCD detector system applied to fluorescence, emission, absorption, and time and spatially resolved spectroscopies are presented. The charge binning readout mode, which combines charge packets from several detector elements into a single charge packet, is critically evaluated for increasing the sensitivity and dynamic range of spectroscopic measurements. Equations describing the sensitivity and dynamic range enhancement achieved through charge binning are derived and experimentally verified in atomic emission and molecular fluorescence spectroscopies. The results of operating the CCD in two specialized readout modes developed in this research termed high-speed framing and spectral framing are presented. High speed framing allows the CCD to rapidly acquire two-dimensional images with high sensitivity. The spectral framing readout mode enables the CCD to record time-resolved spectra at a rate of approximately one spectra every two microseconds with great sensitivity. The design and evaluation of a CCD based molecular fluorescence spectrograph using a mercury pen lamp excitation source is described. The limit of detection for anthracene is 1 x 10 ⁻¹²M and is superior to the results obtained by fluorometers employing laser sources and photomultiplier detection. The design and evaluation of a spatially resolving spectrograph for absorbance spectroscopy of optically dense films is presented. The measurement of the absorption spectra of spatially heterogeneous metal-phthalocyanine thin-film electrodes with peak absorbances greater than five absorbance units is described.

This dissertation deals with the measurement of Modulation Transfer Function (MTF) and spatial noise in infrared CCD's. A new method for the measurement of MTF is presented, which uses the phenomenon of laser speckle. The instrument constructed has the advantages that it does not require components of high optical or mechanical quality, and it does not require precise alignment. There is only one moving part in the system. The results of this method are compared with results obtained from an interferometric technique and from an impulse response technique, and found to be in close agreement. The characterization of spatially-dependent noise is pursued via the formalism of Detective Quantum Efficiency and also via a two dimensional generalization of the classical representation for information capacity. Suggestions for improving the performance of the array as a signal processor are drawn from these considerations. Test results are presented for a 64 by 32 element infrared CCD of Schottky barrier construction.

No description available.

Thesis (M.S.)--Ohio University, August, 1981. / Title from PDF t.p.

Thesis (M.S.)--Ohio University, August, 1988. / Title from PDF t.p.

No description available.

No description available.

In the past decade, charge-coupled devices (CCDs) have rapidly become the astronomical imaging detector of choice for the visible and near-IR spectral regions. There are, however, several problems which have greatly reduced the availability of sufficient quality CCDs to the astronomical community. These include the low blue and ultraviolet quantum efficiency of thick devices, the lack of properly thinned devices, warped imaging surfaces, interference fringing, and the small size of the detectors themselves compared to telescope focal planes. This dissertation presents methods which can be used to optimize CCDs obtained from various manufacturers for astronomical observations. A new thinning technique which produces an optically flat surface across an entire CCD is demonstrated. A mounting technique which maintains a flat and stable imaging surface for thinned devices by bonding the CCD backside against a transparent glass support substrate is also demonstrated. Bump bonding of CCDs onto a silicon support before thinning is discussed as a future mounting/thinning technique. The design of antireflection coatings for the near-UV through near-IR spectral regions is explained and demonstrated on silicon diodes, allowing quantum efficiencies as high as 90% to be obtained. The reduction of interference fringing amplitudes by as much as 70% in the red and near-IR with AR coatings is also discussed. And finally, the design of CCD focal plane mosaics using the optimization techniques presented is discussed.

Speckle noise is an integral part of any laser projection display because it is the nature of laser (coherent) illumination to form interference patterns with high visibility. The granularity of the image due to the speckle formed on the viewer's retina degrades the image quality, thus stimulating the need for speckle reduction techniques applied to laser displays. An instrument to measure image plane speckle contrast was built based on a linear CCD detector array interfaced to an LSI-11 microcomputer. Speckle reduction techniques were then evaluated by comparing the contrast obtained with each method. The effect of the spatial frequency response (MTF) on the measured contrast was studied, along with the statistical significance of the measurement which is limited by the finite sample space of 1024 detector pixels per CCD frame. The lowering of the contrast due to the array MTF can be minimized by working at extremely high F numbers (> 100). The sample space can be widened by taking more than one frame of data and treating all the frames as a single data set. Techniques to reduce speckle noise in laser displays fall into two broad categories: reducing the coherence of light forming the speckle, and incoherently adding multiple uncorrelated (or partially correlated) speckle patterns. The first technique (effective only for monochromatic displays) was implemented by coating a screen with various dyes, phosphors, or fluorescent paints. Using the 514 nm line from an Argon laser, the contrast can be reduced by almost 30% by spraying a thin layer of fluorescent paint on the screen. More speckle reduction can be achieved with an accompanying loss in image brightness. The second technique involved creating a multiplicity of partially correlated speckle patterns that appear from the same position on the screen over the integration period of the eye. The different speckle patterns are produced by changing the angle of illumination while keeping a portion of the laser spot focused on the same point on the screen. The scan angle method (applicable to multi-color displays), can be implemented by properly synchronizing an acousto-optic modulator with the scan optics, and imaging the modulator on the screen. Using a beaded screen and a reasonable laser dither of 10 millirads, the contrast can be reduced by half.

Correlated double sampling (CDS) is a widely used signal processing technique for removal of the Nyquist (reset) noise which is associated with charge sensing circuits employed in a solid state imager. In this thesis work, the power spectral density at the output of a correlated double sampling circuit with first-order low-pass filtered white noise at the input is calculated. A circuit constructed with discrete elements is made to simulate the output stage of a charge-coupled device (CCD). A low-pass filtered wide-band noise from a noise generator is added to the reset reference level when the output signal from this simulator is sampled by the correlated double sampling technique. The experiment measurements show that only about 10% of the noise power measured by simple sampling is obtained when CDS is employed. An autoregressive (AR) model is assumed to fit the sampled data and a recursive algorithm, based on least-squares solutions for the AR parameters using forward and backward linear prediction, is adopted for spectrum estimation. Some conclusions on choosing the bandwidth of the low pass filter for optimum operation is also included.