Optical scanner arrays

Arrayed microlenses are widely used in a variety of applications that involve miniaturized optical components.172 For example, they can be found at the heart of optical communication systems, facsimile machines, laser printers, and many other kinds of digital information storage or processing devices. In all these applications, the arrayed microlenses simply serve as diode laser correctors, fiber-optic couplers or connectors, and optical scanners. In a set of recent publications, Whitesides and coworkers have also demonstrated that arrayed microlenses could be used as a new platform for photolithography, through which submicrometer-sized structures could be conveniently fabricated as patterned arrays by reducing mm to cm scale features on a photomask.157... 

Research on large area electronic arrays of a-Si H devices started a few years later after the first field effect transistors were reported (Snell et al. 1981). These devices take advantage of the capability to deposit and process a-Si H over large areas. Applications include liquid crystal displays, optical scanners and radiation imagers. Present devices contain up to 10 individual elements and are presently used in handheld televisions and FAX machines. 

Polymer photodetectors, on the other hand, are rapidly becoming feasible for commercial applications. Recently a full-color optical scanner was made from an array of 102 polymer photodiodes [315]. Poly(3-octyl thiophene), P30T, was chosen as the polymer for the scanner because its band gap is 1.9 eV (650 nm), which allows it to absorb light at all wavelengths in the visible spectrum. Red, green, or blue filters were placed in front of the photodiodes to make them sensitive to a particular color. This prototype scanner demonstrates the feasibility of making large two-dimensional full-color detector arrays on a wide variety of surfaces. 

Photodiode arrays are used not only in spectroscopic instruments but also in optical scanners and bar-code readers. 

Unhke visual evaluation of a chromatograms before derivatization, which can only give quahtative or semiquantitative results, direct optical evaluation using instruments enables quantitative results to be obtained. For this, a traditional TLC scanner, diode-array scanner or video equipment, either alone or in combination with a flat-bed scanner, is used. Quantitative evaluation with these instruments is described in more detail in Sections 1.2-1 A. However, the limits of this book would be exceeded if we gave a detailed description of all the commercially available equipment that can be used to quantify substances on TLC plates. Training in the use of TLC scanners can be obtained in company seminars (e.g. CAMAG) and detailed instructions are provided by the manufacturer when the equipment is purchased. 

Series/Parallel Scan with time delay and integration remains the principal approach to advanced thermal imaging systems. However, for applications where only a small number of resolution elements are needed, two-dimensional staring detector arrays with CCD or CID readout are being considered [8.106]. This does away with the scanner and a focal optics used with conventional systems. However, to compensate for nonuniformities, both dc offset and gain correction must be made on a pixel by pixel basis. Detector responsivity and readout nonlinearities will increase the number of computations needed for sufficient correction and only experience with the stability of different types of arrays will determine how often the correction algorithms must be calibrated [8.107,108]. 

Optical spectroscopy requires either spectrophotometers, to measure absorbance, fluorimeters, to measure fluorescence, or microscopes, which can measure fluorescence or absorbance of single cells or small groups of cells. Fluorimeters and spectrophotometers usually require solutions or suspensions of material in conventional cuvettes microscopes provide two-dimensional images from smears, slices or siufaces. Other devices that record signals resolved in two-dimensions include gel scanners and microplate readers. Essentially these devices sample the object in an organized manner (detectors can be set up to record absorbance or fluorescence) and information is stored in an electronic array that maps precisely the physical layout of the original object. 

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