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Since any fluorescence image is made up of a large number of such small fluorescent light sources, the image is said to be "convolved by the point spread function". The mathematically modeled PSF of a terahertz laser pulsed imaging system is shown on the right. The output of an imaging system can be described using the equation:
By detuning a laser beam to a frequency less than the resonant frequency (also known as red detuning), laser light is only absorbed if the light is frequency up-shifted by the Doppler effect, which occurs whenever the atom is moving towards the laser source. This applies a friction force to the atom whenever it moves towards a laser source.
An image is formed from the interaction of the electrons with the sample as the beam is transmitted through the specimen. The image is then magnified and focused onto an imaging device, such as a fluorescent screen, a layer of photographic film, or a detector such as a scintillator attached to a charge-coupled device or a direct electron detector.
This image shows a cross-section of the vascular tissue in a plant stem. Bright-field microscopy ( BF ) is the simplest of all the optical microscopy illumination techniques. Sample illumination is transmitted (i.e., illuminated from below and observed from above) white light , and contrast in the sample is caused by attenuation of the ...
SHG requires intense laser light passing through a material with a noncentrosymmetric molecular structure, either inherent or induced externally, for example by an electric field. [ 2 ] Second-harmonic light emerging from an SHG material is exactly half the wavelength (frequency doubled) of the light entering the material.
This term denotes images formed by combining raw measurements from multiple points around the specimen in a mathematical inversion scheme. This process is analogous to x-ray computed tomography, except that tomographic mathematical models describe light and sound propagation in tissues. Fig. 1: Operational capabilities of MSOT.
Two-photon excitation microscopy of mouse intestine.Red: actin.Green: cell nuclei.Blue: mucus of goblet cells.Obtained at 780 nm using a Ti-sapphire laser.. Two-photon excitation microscopy (TPEF or 2PEF) is a fluorescence imaging technique that is particularly well-suited to image scattering living tissue of up to about one millimeter in thickness.
Within the NIR window, scattering is the most dominant light-tissue interaction, and therefore the propagating light becomes diffused rapidly. Since scattering increases the distance travelled by photons within tissue, the probability of photon absorption also increases. Because scattering has weak dependence on wavelength, the NIR window is ...