ANSI Z80.9-2010 pdf download Ophthalmics – Devices for Low Vision
3.15 magnifier: Lens system designed to produce an enlarged image by relative distance magnification. It may be a simple single element or compound multiple element system.
3.15.1 spectacle magnifier/spectacle microscope: Magnifier in the form of spectacles and intended to be worn as spectacles, mounted or held close to the eye. This includes power in addition to a normal near correction.
3.15.2 illuminated magnifier: Magnifier incorporating illumination.
3.16 monocular device: Optical device to be used before only one eye.
3.17 optical dimensions/optical zone of magnifier: Usable linear size of a magnifier when mounted,expressed in millimeters.
3.18 power, equivalent: Reciprocal of the equivalent focal length in air measured in meters.
3.19 reading cap: Positive lens placed in front of a telescopic objective to adapt the device for viewing a near object.
3.20 reference seeing distance (RSD): Agreed distance of 250 mm between the object side (first) nodal point of the eye and the object observed. The reference seeing distance is used, above all,as a reference parameter for calculating the magnification of optical instruments used for near vision.
3.21 relative distance magnification: Change in the size of the retinal image that is obtained by changing the viewing distance.
3.22 spatial resolution: Smallest separation between two details, expressed as a linear or angular measurement, at which a pair of points may be recognized as being separate under a given set of conditions.
3.23 stand magnifier: Magnifier in which the support is designed to position the optical system at a set or adjustable distance from the object to be viewed.
3.23.1 vertex image distance (for stand magnifiers): Distance from the magnifier surface nearest to the eye to the virtual image when the object is placed at the designated position
3.23.2 exit image vergence (for stand magnifiers): Reciprocal of the vertex image distance expressed in meters. The unit of vergence is the diopter (D).
3.24 telemicroscope/near-vision telescope: A telescope adapted for viewing near objects.