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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]
Diagram showing vectors used to define the BRDF. All vectors are unit length. points toward the light source. points toward the viewer (camera). is the surface normal.. The bidirectional reflectance distribution function (BRDF), symbol (,), is a function of four real variables that defines how light from a source is reflected off an opaque surface. It is employed in the optics of real-world ...
The decadic absorbance of a scattering sample is defined as −log 10 (R+T) or −log 10 (1−A). For a non scattering sample, R = 0, and the expression becomes −log 10 T or log( 1 / T ), which is more familiar. In a non-scattering sample, the absorbance has the property that the numerical value is proportional to sample thickness.
The overall reflection of a layer structure is the sum of an infinite number of reflections. The transfer-matrix method is based on the fact that, according to Maxwell's equations , there are simple continuity conditions for the electric field across boundaries from one medium to the next.
Gloss reflection. Gloss is an optical property which indicates how well a surface reflects light in a specular (mirror-like) direction. It is one of the important parameters that are used to describe the visual appearance of an object.
The surface has less reflective contrast and a shallow milky effect. Orange peel is caused by an uneven surface formation of large surface structures distorting the reflected light. Poor reflective contrast and shallow milky effect. Two high gloss surfaces can measure identically with a standard glossmeter but can be visually very different.
Diffuse reflection is the reflection of light or other waves or particles from a surface such that a ray incident on the surface is scattered at many angles rather than at just one angle as in the case of specular reflection.