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Lens Magnification Measuring System

IP.com Disclosure Number: IPCOM000075592D
Original Publication Date: 1971-Oct-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Heiling, GM: AUTHOR [+2]

Abstract

The system includes two Ronchi gratings 10 and 11 positioned on opposite sides of a lens 12, the magnification of which is to be measured, a light source 13 for supplying light to the grating 10 and a light receiving device 14 at the side of the grating 11 opposite that facing lens 12.

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Lens Magnification Measuring System

The system includes two Ronchi gratings 10 and 11 positioned on opposite sides of a lens 12, the magnification of which is to be measured, a light source 13 for supplying light to the grating 10 and a light receiving device 14 at the side of the grating 11 opposite that facing lens 12.

The Ronchi grating 10 having alternate, equally spaced opaque and transparent areas, is illuminated by light source 13 having the required spectral properties. Grating 10 is placed in the object plane of lens 12, under test, and grating 11 is placed in the image plane of the lens. The line spacing on grating 11 is equal to the line spacing of grating 10, multiplied by the intended magnification of lens 12. Gratings 10 and 11 are aligned approximately parallel and have their opaque lines extending in the same direction.

The combined pattern of the image of grating 10 overlaying grating 11 is used by the light-responsive device 14 which may be the unaided eye, a scanning photodetector, the eye aided by intermediate optics and/or a spectrum converter. In all cases, the number of fringes or dark and light areas per unit length are counted. The error that results in one complete cycle (dark and light bands) is given by the following equation:. Delta = M/2/F over R-MF where: Delta = magnification error M = lens magnification F = center-to-center spacing of the object plane grating R = dimension over which the fringes can be counted.

The minimum F dimen...