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A Goniophotometer is a device used for measurement of the light emitted from an object at different angles. [1] The use of goniophotometers has been increasing in recent years with the introduction of LED -light sources, which are mostly directed light sources, where the spatial distribution of light is not homogeneous. [ 2 ]
The term goniometry derives from two Greek words, γωνία 'angle' and μέτρον 'measure'. [1] The protractor is a commonly used type in the fields of mechanics, engineering, and geometry. The first known description of a goniometer, based on the astrolabe , was by Gemma Frisius in 1538.
Goniophotometry or goniometric optical scatter measurement is the technique of measuring the angular distribution of light, possibly wavelength-dependent, scattered from a surface. Goniophotometry is used to measure intensity distributions from lamps and luminaries and to evaluate the gloss of paints and other surface finishes.
The 'gonio' part of the word refers to the device's ability to measure at different angles. Several similar devices have been built and used to capture data for similar functions. Most of these devices use a camera instead of the light intensity-measuring sensor to capture a two-dimensional sample of the target.
A positioning goniometer or goniometric stage is a device used to rotate an object precisely (within a small angular range) about a fixed axis in space. Its appearance is similar to that of a linear stage .
The Thomas test is a physical examination test, named after the Welsh orthopaedic surgeon, Hugh Owen Thomas (1834–1891), to rule out hip flexion contracture (fixed partial flexion of the hip) and psoas syndrome (injury to the psoas muscle).
Established standard objects and events are used as units, and the process of measurement gives a number relating the item under study and the referenced unit of measurement. Measuring instruments, and formal test methods which define the instrument's use, are the means by which these relations of numbers are obtained.
Hip-knee-ankle angle. On projectional radiography, the degree of varus or valgus deformity can be quantified by the hip-knee-ankle angle, [7] which is an angle between the femoral mechanical axis and the center of the ankle joint. [8] It is normally between 1.0° and 1.5° of varus in adults. [9] Normal ranges are different in children. [10]