Topics: Dioptre, Focal length, Lens Pages: 3 (382 words) Published: March 5, 2013
1- Eyepiece- The part of the instrument into which the user looks 2- Chrome knurled sleeve— used to rotate the Reticle to orient prism base. 3- Prism axis scale — Used for orientation of prism axis. 4- P.C.D knob— Used to read prism amounts greater than five prism diopters. 5- Prism diopter power scale-which is a dial on the side that lets you check to see what power the lens is. 6- Len stop-Aperture against which the lens rests.

7- Cylinder axis wheel
8- Filter level-Used to engage or remove green filter.
9- Lamp access cover- Provides access to change the lensmeter bulb. 10- Locking lever — Used to elevate or depress the position of the instrument for individual’s height or posture 11- Power drum– The large wheel used to find the power of the lens. It is marked with power ranging from –20 to + 20 diopters. Black numbers represent plus power, red numbers represent minus power 12- Spectable table lever-Used to raise, or lower the level of the Spectacle Table 13- Spectable table-The resting place for the frame when neutralizing finished eyewear. 14-Ink pad-Holds the spotting ink

15- Marking device control-which is used to mark a lens with a water soluble marker. 16- Lens holder handle— Used to hold a lens in place against the aperture A lensmeter or lensometer, also known as a focimeter, is an ophthalmic instrument. A lensmeter (focimeter) is a device for measuring the power of a spectacle lens. A target (typically a crossed set is imaged through a lens of focal length f. The spectacle lens under test is placed at the rear focal point of this lens. Lightemerging from the spectacle lens enters aneyepiece with an internal reticle. The user axially shifts the target until it is simultaneously in focus with the reticle. This situation occurs when thelight emerging from the spectacle lens is collimated.

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