This wheel is usually incremented in steps of 0.12 diopters, with higher powers being incremented in steps of 0.25 diopters. The inclination control is used to loosen the lensometer body from the base, this allows the operator to adjust the viewing angle of the lensometer for easier viewing. The filter control is a small knob used to apply a green filter to the lensometer lamp for a more comfortable view through the clear material while allowing this same filter to be removed for a brighter view of filtered lenses. This is done by spinning the mires inside of the lensometer body. The axis adjustment wheel allows the operator to align the primary and secondary power meridians in the lensometer. Some lensometers have this optional component which allows the operator an easier view of the axis wheel by magnifying the scale. The table often bisects a scale mounted on the lensometer body used to measure the height of the optical center. The eyeglass table is used to keep a frame-mounted and the lens aligned properly for measuring the correct axis of the lens. The circular piece on the end that swivels and has legs that touch the lens is referred to as a gimbal. The lens holder is the arm that swivels into place to hold the lens or frame Note that the lens marker pins and ink pad can be replaced and the ink pad requires occasional re-inking. The lens marker is a simple device consisting of three spring-loaded pins that dip into a water-soluble ink to mark the lens horizontally with the center pin marking the direct point being read through the lensometer. Some older model lensometers do not contain a prism compensator but do have a ledge that allows the use of auxiliary prisms usually in increments of 3, 6, and 9 prism diopters to help neutralize high amounts of the prism. Lensometers have an attached rotary prism that allows the operator to dial in 0 to 25 diopters of prism anywhere from 0 to 360 degrees. Turning the eyepiece counterclockwise to the most plus setting and then slowly turning the eyepiece clockwise towards the minus until the reticle comes into focus. The eyepiece must be adjusted to zero out the lensometer for their Rx. It measures the focal length of a lens and converts it into diopters on a circular number line called a Power Drum. It is a microscope, which is used to measure the back focal length of the lens. The lensmeter is essentially a centred telescopic optical system aligned with a standard optical lens and a rotatable target illuminated by a light source. Lensmeter, lensometer, focimeter or vertometer. Measurement of Bifocal Power by manual lensometer. ![]() Operating Instructions for Manual lensometer.
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