Differential phase-contrast

Tdrdk P, Sheppard C J R and LaczikZ 1996 Dark field and differential phase contrast imaging modes in confocal microscopy using a half aperture stop Optik 103 101-6... 

Fig. 11.5 Differential phase contrast detection of patterned protein in a 10 mm by 30 mm region, (a) Protein height signal showing ridges of protein in a checker board pattern, (b) Side band demodulated signal image in which the carrier frequency of the ridges is removed to show only the protein envelope. Reprinted from Ref. 21. with permission. 2008 Optical Society of America...

See, C. W. Iravani, M. V. Wickramasinghe, H. K., Scanning differential phase contrast optical microscope application to surface studies, Appl. Opt. 1985, 24, 2373 2379... 

Routh, H. F., Pusateri, T. L and Nikoonahad, M. (1989). Differential phase contrast acoustic microscopy. IEEE 1989 Ultrasonics Symposium, pp. 817-20. IEEE, New York. [69]... 

The sample is then raster scanned through the focus spot, and the transmission in each image pixel is recorded. Among the variety of soft X-ray detectors are proportional counters and phosphors with photomultipliers. A recent development is a silicon detector with a segmented chip (Feser et al., 2003) allowing for dark and bright field as well as differential phase contrast imaging. 

Differential Phase-Contrast Microscope with a Split Detector... 

FIG. 16.5 Optical system for readout of 3D memory. For nondestructive readout, a near-IR, differential phase-contrast microscope is used. 

As described in Section 16.4.5, the detection of refractive-index change between two isomers in a photochromic material is the most promising technique for nondestructive readout.It is necessary to develop a readout system that is sensitive to refractive-index distribution. For this purpose, several methods, such as phase-contrast microscope, differential phase-contrast microscope, and reflection confocal microscope configurations have been proposed. 

An alternative readout system is a scanning differential phase-contrast microscope with a split detector as shown in Figure 16.5. The optical configuration is compact and easy to align. The memory medium, in which the data bits have been recorded, is located at the focus of an objective lens. The band limit of the optical transfer function (OTF) is the same as that of a conventional microscope with incoherent illumination. The resolution, especially the axial resolution of the phase-contrast microscope, is similar to that obtained by Zemike s phase-contrast microscope. The contrast of the image is much improved compared to that of Zernike s phase-contrast microscope, however, because the nondiffracted components are completely eliminated by the subtraction of signals between two detectors. The readout system is therefore sensitive to small phase changes. 

Toriumi, A., Herrmann, J.M., and Kawata, S., Nondestructive readout of a three-dimensional photochromic optical memory with a near-infrared differential phase-contrast microscope, Opt. Lett., 22, 555-557, 1997. 

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