Patent ID: 7209224
Filing Date: 2007-04-24
Classification: G01M

Abstract:
1. A lens meter for measuring optical characteristics of a lens, the lens meter comprising: a lens rest, having an opening, on which the lens is mounted; a measurement optical system having a measurement optical axis which passes through the opening, a light source which projects a measurement light bundle along the measurement optical axis, a plurality of measurement targets arranged on the measurement optical axis, and a photo-sensor which photo-receives the measurement light bundle passed through the opening and the measurement targets; a calculation part which calculates the optical characteristics of the lens based on a change in coordinates of images of the measurement targets in a measurement state where the lens is mounted on the rest and placed on the measurement optical axis with respect to coordinates of images of the measurement targets in a reference state where the lens is not mounted on the rest and not placed on the measurement optical axis; and a memory which stores information including the coordinates of the images of the measurement targets, wherein the calculation part makes the memory to store coordinates of images of the measurement targets not detected by the photo-sensor in the reference state which are obtained at the time of assembly and adjustment of the lens meter, and based on coordinates of images of the measurement targets detected by the photo-sensor in the reference state after power application to the lens meter and before measurement of the lens and the coordinates of the images of the measurement targets stored in the memory, obtains coordinates of images of the measurement targets not detected by the photo-sensor in the reference state after the power application to the lens meter and before the measurement of the lens, and the calculation part calculates the optical characteristics of the lens based on a change in coordinates of images of the measurement targets detected by the photo-sensor in the measurement state with respect to the coordinates of the images of the measurement targets detected by the photo-sensor in the reference state before the measurement of the lens and the obtained coordinates of the images of the measurement targets not detected by the photo-sensor in the reference state before the measurement of the lens.