摘要:

AbstractThe paper investigates continuous wave techniques for imaging through scattering media. Particular attention is paid to the confocal optical detection method, and experimental results are presented that demonstrate the dependence of spatial resolution on the optical configuration over a wide range of scatterer concentrations. It is seen that as the scatterer concentration increases there is a transition region over which the spatial resolution rapidly degrades. The concentration at which this occurs can be varied by changing the detection optics. It is shown that changes in the optical configuration affect the sensitivity to different scattered components, and through this, the imaging response. This feature can be used to improve the spatial resolution even when there is no unscattered light present.

ISSN:0966-9051    

DOI:10.1002/1361-6374(199412)2:4<163::AID-BIO1>3.0.CO;2-X

出版商:IOP Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA functional image of the extensor digitorum muscle was obtained using the frequency domain spectroscopic technique with near‐infrared light. The muscle was imaged by measuring the change in phase angle of modulated waves of near‐infrared light in response to increased absorption of deoxygenated hemoglobin, which resulted from increased O2metabolism during arm exercise. The image was compiled from a raster scan of flexion and relaxation exercises at 95 separate points on the dorsal surface of the right forearm. Each point on the arm consisted of a complete experiment that included continuous frequency‐domain measurements of phase and intensity during rest, isotonic exercise, and recovery from exercise. Analysis consisted of a simple subtraction of the average phase angle baseline at rest from the average phase reading during steady‐state contraction of the extensor digitorum muscle. A difference array of data was then compiled from these 95 experiments to give a 2‐D density‐plot image. The image clearly demonstrates the extensor digitorum muscle in its oblique position within the density‐plot array. This experiment shows thein vivofunctional imaging capability of the frequency‐resolved technique and indicates that a high degree of resolutio

ISSN:0966-9051    

DOI:10.1002/1361-6374(199412)2:4<174::AID-BIO2>3.0.CO;2-Q

出版商:IOP Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractWe have developed an imaging system for high speed image acquisition in fluorescence microscopy. The use of a two‐ dimensional CCD array in a special operation mode called TDI (Time Delayed Integration) permits a significant increase in photon integration time compared to 1D scanners (higher signal‐to‐noise ratio) without compromising the total data throughput rate. Instead of a start–stop system we use continuous stage motion in the CCDs parallel shift direction. Synchronizing the parallel clock and the stage velocity guarantees a one‐to‐one relationship between a moving cell and its image onto the CCD. Compared to start‐stop system, TDI scanning offers a speed improvement, negligible blurring in the scanning direction and a complete suppression of pixel variability boosting the SNR mo

ISSN:0966-9051    

DOI:10.1002/1361-6374(199412)2:4<184::AID-BIO3>3.0.CO;2-M

出版商:IOP Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractIn the literature many autofocus algorithms have been proposed and compared (Groenet al1985, Firestoneet al1991, Yeoet al1993, Price and Gough 1994) for use in optical microscopy (bright field and fluorescence microscopy). Most of the focus criteria measure the high frequency contents of a recorded image as a measure of focus. In this paper we show that a focus criteria should measure the signal power of the middle frequency, since defocusing mainly reduces the frequencies around half the cut‐off frequency of theoptical system. The filter that provides the requiredband‐passfiltering depends strongly on the sampling density of the camera. There are two practical combinations of sampling density and one‐dimensional digital band‐pass filter:Sampling at the Nyquist frequency and the {1, 0, −1} filter;Sampling at half the Nyquist frequency and the {1, −1} filter.The latter is to be preferred due to noise considerations and the fact that it uses four times fewer sample points. Calculation speed can also be increased by further reducing the sampling density perpendicular to the filter (on chip or in software) down to 1/8 of the Nyquist frequency. We have designed a three‐phase autofocus algorithm that works well in fluorescence and bright field microscopy. The phases are:Coarse: find the region near focus (step size of typically a few microns);Fine: find a quadratic region around focus (step size around one micron);Refine: use a quadratic fit on samples around the peak to find the in‐focus position.We found that the final focus error is smaller than the mechanical reproducibility of ourz‐axis (≈50 nm) for light levels down to 400 photo‐electrons per pixel (sampling at the Nyquist frequency using a cooled CCD camera with pi

ISSN:0966-9051    

DOI:10.1002/1361-6374(199412)2:4<193::AID-BIO4>3.0.CO;2-L

出版商:IOP Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractState space search techniques like dynamic programming have been proposed for the delineation of object regions in extremely noisy two‐dimensional images. Usually, such methods are applied directly to the image or to a window within the image. The method described here starts with a region of interest enclosing the required boundary. A geometric transform is used to straighten the region of interest into a rectangular matrix. In the transform domain, merit coefficients are computed and a dynamic programming optimal path algorithm is applied to find the transformed object region boundary. Finally, the path is transformed back to the original image domain. The subject of the current paper is the extension of the two‐dimensional search method to three dimensions. Experimental results are given, as well as an example from the field of cell biol

ISSN:0966-9051    

DOI:10.1002/1361-6374(199412)2:4<204::AID-BIO5>3.0.CO;2-L

出版商:IOP Publishing Ltd    

年代:1994

数据来源: WILEY