Illustration of the standard sampling technique. The linear array records data from a portion of the image. After acquisition of an initial slice of data [panel (a)], the sample is shifted along the axis of the detector by one pixel width and a second slice is acquired [panel (b)]. The process is repeated to create an image [panel (c)].
Theoretical MTFs for our experiment using a objective, a detector with an effective pixel size of , and an imaging system composed of these two elements. The sampling frequency corresponding to an interpixel distance of (i.e., ) and the associated Nyquist frequency are labeled.
Illustration of the dithered sampling technique. After acquisition of an initial slice [panel (a)], the sample is shifted along the axis of the detector by a fraction of a pixel and a second slice is acquired [panel (b)]. The individual pixels of each slice are then interlaced to produce a composite slice that uses twice as many pixels to represent the same spatial domain in the sample image [panel (c)]. The sample is then shifted along the axis of the detector by a fraction of the pixel width and the process is repeated to create an image.
Illustration of how a given field of view is sampled with either a standard [panel (a)] or a dithered [panel (b)] scheme. In panel (a), the open circles represent sampling positions separated by a distance on the axis and on the axis. In panel (b), the closed circles represent additional sampling positions that arise in the dithering scheme in which the image is shifted by an amount in the direction and in the direction. The sampling frequency along a given axis is the inverse of the intersampling distance.
transmission based images of groups 6 and 7 of a 1951 USAF resolving power test target acquired with the detector. (a) Standard imaging technique with a sampling frequency of . (b) Dithered sampling technique with a sampling frequency of . (c) Average contrast of each horizontal target element as a function of the element line pair frequency when sampling at a frequency of 0.4 (open circles) or (closed circles). The error bars represent one standard deviation of the measurements.
(a) Visible image of a phase-separated polymer blend constructed using the fluorescence of the singlet oxygen sensitizer. (b) Standard image of the polymer blend constructed using the phosphorescence of singlet oxygen. Data were acquired with a sampling frequency of . (c) “Dithered” image of the polymer blend constructed using the phosphorescence of singlet oxygen. Data were acquired with a sampling frequency of . Both singlet oxygen images were contrast-enhanced and filtered in the frequency domain to suppress vertical lines (see Fig. 7). The acquisition time was /slice.
The singlet oxygen image of our phase-separated polymer sample acquired with the dithered sampling technique. The vertical stripes in the image are due to differences in the sensitivity of the respective detector elements. The vertical lines can be suppressed by filtering in the frequency domain [see Fig. 6(c)].
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