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Yoked prism can move the image away from primary gaze without the need for a constant head tilt or turn. Prism correction is measured in prism dioptres. A prescription that specifies prism correction will also specify the "base". The base is the thickest part of the lens and is opposite from the apex.
Prism (optics) An optical prism is a transparent optical element with flat, polished surfaces that are designed to refract light. At least one surface must be angled — elements with two parallel surfaces are not prisms. The most familiar type of optical prism is the triangular prism, which has a triangular base and rectangular sides.
Prism spectrometer. A prism spectrometer is an optical spectrometer which uses a dispersive prism as its dispersive element. The prism refracts light into its different colors ( wavelengths ). The dispersion occurs because the angle of refraction is dependent on the refractive index of the prism's material, which in turn is slightly dependent ...
The aim of an accurate intraocular lens power calculation is to provide an intraocular lens (IOL) that fits the specific needs and desires of the individual patient. The development of better instrumentation for measuring the eye 's axial length (AL) and the use of more precise mathematical formulas to perform the appropriate calculations have ...
measuring strabismus. The prism cover test ( PCT) is an objective measurement and the gold standard in measuring strabismus, i.e. ocular misalignment, or a deviation of the eye. [1] It is used by ophthalmologists and orthoptists in order to measure the vertical and horizontal deviation and includes both manifest and latent components. [1]
Nicol prism. A Nicol prism is a type of polarizer. It is an optical device made from calcite crystal used to convert ordinary light into plane polarized light. It is made in such a way that it eliminates one of the rays by total internal reflection, i.e. the ordinary ray is eliminated and only the extraordinary ray is transmitted through the ...
A dispersion relation relates the wavelength or wavenumber of a wave to its frequency. Given the dispersion relation, one can calculate the frequency-dependent phase velocity and group velocity of each sinusoidal component of a wave in the medium, as a function of frequency. In addition to the geometry-dependent and material-dependent ...
Wedge prism. The wedge prism is a prism with a shallow angle between its input and output surfaces. This angle is usually 3 degrees or less. Refraction at the surfaces causes the prism to deflect light by a fixed angle. When viewing a scene through such a prism, objects will appear to be offset by an amount that varies with their distance from ...
Basal area is the cross-sectional area of trees at breast height (1.3m or 4.5 ft above ground). It is a common way to describe stand density. In forest management, basal area usually refers to merchantable timber and is given on a per hectare or per acre basis.
The linear map h → J(x) ⋅ h is known as the derivative or the differential of f at x . When m = n, the Jacobian matrix is square, so its determinant is a well-defined function of x, known as the Jacobian determinant of f. It carries important information about the local behavior of f.