Linear image

Splinter hemorrhage Linear image under the nail beds caused by local hemorrhage as a result of hand trauma or endocarditis. 

In linear imaging theory, it is assumed that the object is a weak scatterer, so that the quadratic term in equation 5 is small and can be neglected... 

In linear imaging, these two effects can be mathematically described by damping functions, E, applied to the CTF (for details see William and Carter 1996, Spence 1988). Their combined effects are shown in Figure 2 as the envelope function to the CTF. The partial temporal coherence places a limit on the information that can be transferred in a microscope, a value called the information limit. Traditionally, the information limit is defined as the... 

The reconstruction of the exit wave occurs in four steps. It starts with an alignment step where the images of the focal-series are aligned with respect to each other. In the second step, an analytical inversion of the linear imaging problem is achieved by using the paraboloid method (PAM) to generate a first approximation to the exit wave function. This approximated exit wave function is then refined in the third step by a maximum likelihood (MAE) approach that accounts for the non-linear image contributions. Finally, the exit wave is corrected for residual aberrations of the microscope. 

Figure 7. The linear image contributions of a focal-series are located on the surface of two paraboloids obtained by 3D Fourier transformation of the focal series. The two paraboloids correspond to the electron wave function and its complex conjugate.

The result of the PAM reconstruction is, in general, only an approximation of the exit wave function. Some non-linear terms may be present exactly on the paraboloid surfaces, and, thus result in artifacts for the PAM reconstruction. However, the PAM result is a good approximation to the exit wave function, which, in the present implementation, is used as a starting point for a maximum likelihood (MAL) reconstruction that takes the non-linear image contributions fully into account (Coene et al. 1996, Thust etal. 1996a). 

Figure 3.6 Schematicofa double-focusing sector field mass spectrograph with Mattauch-Herzog geometry with a linear imaging curve (double focusing for ions of all masses simultaneously) modified field combination with 70°. In the mass spectrograph, photographic ion detection or focal plane array detectors are used for quasi-simultaneous detection of separated ion beams. (H. Kienitz (ed.), Massen-spektrometrie (1968), Verlag Chemie, Weinheim. Reproduced by permission of Wiley-VCH)...

Fluorescence and Phosphorescence. Fluorescence spectra using the diode array linear imaging apparatus were obtained for GAV in benzene and in isopropanol at ambient temperatures. The fluorescence and absorption spectra are characterized by absorption (abs) =280 nm and 230 nm, and a A (emission) = 368 nm in... 

Figure 1. The diode array linear imaging of the phosphorescence of GAV in benzene at 77 K, produced by a single laser pulse of S ns width.

Fast chiral separations were carried out in a quartz chip using a linear imaging UV detector. Figure 6.11 shows the chiral separation of a tocainide derivative (an antiarrhythmic drug). UV imaging with a diode-array detector located along the 25-mm-long separation channel reveals the separation between the two enantiomers. Another chiral separation of pseudoephedrine was achieved in 13 s. The... 

T. L. Koch, J. H. De Loo, M. H. Kalisher and J. D. Phillips, "Monolithic n-Channel HgCdTe Linear Imaging Arrays , IEEE Trans. Electron Devices, ED-32 (8), 1592-1598, August 1985. 

An a-Si H photosensor array has been successively applied to a long linear image sensor and high-performance area image sensor. A photodiode in which a-Si H is sandwiched between ITO and metal electrodes is used because of its short photoresponse time. In this structure, blocking contacts at both electrodes are necessary to prevent carrier injection from the electrodes. 

Thin-film technology is useful in fabricating these devices. CdS-CdSe photoconductive sensors (Boronkay et al., 1978 Komiya et al., 1981) and As-Se-Te photodiodes (Tsukada et al., 1977) were applied to the long linear-image sensor. As-Se-Te photodiodes (Tsukada et al., 1979) and ZnSe - ZnCdTe photodiodes (Terui et al., 1980) were used in the area image sensor. However, there are some problems with these sensors long photoresponse time for the CdS-CdSe sensor, thermal instability, and low yield for the As-Se-Te sensor, and a high-temperature process for the ZnSe-ZnCdTe sensor. 

A contact linear image sensor can make the equipment compact, because it does not require a high-magnification lens system. The sensor unit consists of an illuminator, a compact optical guide, and the long linear photosensor array, which is, for example, 210 mm long for the iso-A4... 

Fig. 1. Exploded view of contact linear image sensor. [From S. Kaneko et al.. Amorphous Si H contact linear image sensor with SijN4 blocking layer. Technical Digest—International Electron Device Meeting. Copyright 1982 IEEE.].

Hamano et al. (1982) have fabricated an a-Si H photodiode array linear image sensor. The sensor structure is shown in Fig. 5. The sensor is constructed by first forming individual electrodes on a glass or a ceramic substrate. Then l-/mi-thick undoped a-Si H is produced at 230°C by glow-discharge decomposition of silane and finally 1500-A-thick ITO common electrode, which also acts as an antireflection coating, is deposited by dc sputtering. 

The spectral response of the photosensor is shown in Fig. 9. The collection efficiency is nearly equal to unity throughout the visible region. Figure 9 also shows the emission intensity of the yellow-gree n LED used in the contact linear-image sensor. The photosensor has high sensitivity for this illuminator. 

Fig. 9. Spectral response for a-Si H photodiode using Si3N4 and p-a-Si H blocking layers (solid curve). The emission intensity spectrum of the yellow-green LED is also shown (dotted curve). The applied voltage for the photodiode is 5 V. [From S. Kaneko el at., Amorphous Si H contact linear image sensor with Si3N4 blocking laye r. Technical Digest—International Electron Device Meeting. Copyright 1982 IEEE.]...

However, this charge pulse contains switching noise caused by the MOS-FETs. Since the linear image sensor have many Si ICs, this switching noise fluctuates because of nonuniformity in MOSFET characteristics. Therefore an efficient noise reduction technique is required for this sensor (Ozawa et al., 1982 Kaneko et al., 1982), as in the case of Si monolithic MOS image sensors (Ashikawa et al., 1973 Aoki et al., 1980). 

Fig. 11. Schematic representation for a-Si H linear image sensor using photodiode array. V and C, represent an a-Si H photodiode.

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