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Photoplethysmography of the thumb by off-axis digital holography. pulsatile waves on the back of a frog measured by off-axis holographic photoplethysmography Remote photoplethysmography can also be performed by digital holography , which is sensitive to the phase of light waves, and hence can reveal sub-micron out-of-plane motion.
The PPGV was found to be useful in detecting blood loss by observing the spectral features of the PPGV. [3] [4] [5] LF power, together with other features derived from the PPG waveform, was used to classify patients into different ranges of systemic vascular resistance, which may be used as an indicator of critical illness. [6]
Venous translucence is the process of reflective image visualization of veins by light, which reaches up to the superficial venous system. It is a non-invasive method. It is a non-invasive method. Since it is a simple, low-cost technique it can be repeated as needed, which is useful in disease-process monitoring.
Fabry–Pérot interferometer, using a pair of partially reflective, slightly wedged optical flats. The wedge angle is highly exaggerated in this illustration; only a fraction of a degree is actually necessary to avoid ghost fringes. Low-finesse versus high-finesse images correspond to mirror reflectivities of 4% (bare glass) and 95%.
Diagram of Lambertian diffuse reflection. The black arrow shows incident radiance, and the red arrows show the reflected radiant intensity in each direction. When viewed from various angles, the reflected radiant intensity and the apparent area of the surface both vary with the cosine of the viewing angle, so the reflected radiance (intensity per unit area) is the same from all viewing angles.
Spatial light modulators can be either reflective or transmissive depending on their design and purpose. [4] DMDs, short for digital micromirror devices, are spatial light modulators that specifically work with binary amplitude-only modulation. [5] [6] Each pixel on the SLM can only be in one of two states: "on" or "off". The main purpose of ...
For a dim spot to occur, the shale has to have a lower acoustic impedance than both the water sand and the oil/gas sand, which is the opposite situation required for a bright spot to occur. This is possible because compaction causes the acoustic impedances of sands and shales to increase with age and depth but it does not happen uniformly ...
Reflection high-energy electron diffraction (RHEED) is a technique used to characterize the surface of crystalline materials. RHEED systems gather information only from the surface layer of the sample, which distinguishes RHEED from other materials characterization methods that also rely on diffraction of high-energy electrons .