Point-spread-function PSF

The performance of an optical imaging system is quantified by a point-spread function (PSF) or a transfer function. In astronomy we image spatially incoherent objects, so it is the intensity point-spread function that is used. The image is given by a convolution of the object 0, r]) with the PSF... 

For a well-controlled 3D exposure, it is necessary to control the light intensity distribution at the focus, which is described by the point-spread function (PSF). Even for tight, aberration-free focusing, the axial spreading of PSF is larger than the lateral spreading [40] ... 

The point spread function (PSF) resulting imder these circiunstances was derived in using scalar Debye theory [43] ... 

A small dot sample of DPPH was measured first to obtain the point spread function (PSF) or a system function. The blurred image of an actual sample is deconvoluted with PSF to obtain a better resolution depending on the S/N ratio.1 Although it took hours to get an image with a good resolution with cw-ESR, measurements are automatically made with a computer-controlled X-Y-Z stage. 

A large potential source of systematic uncertainty is due to the finite image resolution. The measured image can be described as the convolution of the true sharp image with the imaging system point spread function, PSF. The PSF is reasonably approximated by a Gaussian,... 

Point spread function (PSF) If a tiny population of 100 nm fluorescent beads sandwiched between a coverslip and a microscope slide are examined at high resolution (i.e. at 100x objective magnification, 1.4 NA. and in a correctly matched refractive index of oil), it can actually show a tiny set of rings in the horizontal (XY) view (also called an airy disk (see Fig. below). This airy disk cannot be avoided due to diffraction and the wave nature of light. If a specimen is optically sectioned and projected in a vertical (XZ) view (see Fig. xx), a set of concentric rings will flare from the center. When a three-dimensional image of this specimen is collected, a complete point spread function is said to be recorded for each bead. The (PSF)... 

For this test, the target was scanned by the read-out beam in 256 x 256 steps. The full width of the point-spread function (PSF) is 3 pixels, corresponding to 43 TV-line pairs . At FWHM, the width is 1.5 pixels, or 85 TV-line pairs . Thus the 256 pixels in both directions are not at all independent. This result clearly shows the degradation of the imaging performances of a Vidicon system by the scintillation screen. 

At the most basic level, the data can be visualized (rendered) as an image volume viewed at varying angles and manually compressed or stretched to fit. Alternatively, a more mathematical approach can be taken if the optical aberrations can be measured. In 3D fluorescence microscopy, this measurement is known as the point spread function (psf), and a process of deconvolution can be used to correct any aberrations with a known psf. Once corrected, the data can be rendered for viewing and measurement with confidence. 

The spatial response characteristics are normally characterized by the point spread function (PSF) - the detector s signal following a delta function stimulus. Ideally the point spread is also a delta function. Experimentally this is seldom the case as detector characteristics generally give the signal a Gaussian spread. It is often the point spread function that is the main cause of the limited resolution in powder diffraction experiments. 

The spatial resolution of a PET scanner is determined by the FWHM of point-spread-functions (PSF) obtained from measurement of activity distribution from a point source. The spatial resolution can be transverse radial, transverse tangential, and axial, and these values are given in Table 6.1 for scanners from different manufacturers. 

Figure 6.5. Point spread functions (PSF) at 0 and 10 cm from the FOV. The transverse resolution (FWHM) is best at the center and worsens radially across the FOV. (Reprinted with the permission of The Cleveland Clinic Center for Medical Art Photography 2009. All Rights Reserved)...

Figure 4.34 Fluorescence spectroscopy of single biomolecules (A) Localization of a macromolecule labeled with a single fluorophore F with nanometer accuracy. The point-spread-function (PSF) can be...

For non-uniform sampling the FT of sampling schedule (sometimes referred to as Point Spread Function, PSF) is not a simple train of delta pulses, but becomes a more complex function (see Sect. 4 and Fig. 6). This, in general, leads to three conclusions ... 

The extension of the PCFOV may be limited by the presence of a passive collimator in front of the detector. For large area hard X-ray detectors the coUimator is also the most practical shielding device for cosmic diffuse background (CDB). The impact of the collimator on instrument sensitivity and on the point-spread function (PSF) wiU be discussed in 3. 

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