Recording Electronic Lens Bench

Abstract

The measurement of lens characteristics by the method of contrast rendition of a sine wave target has been studied extensively in recent years. This method has not, however, been widely used because of the time required to measure a lens at many field angles and focal positions as well as the time required to reduce the data to suitable form. These limitations are caused by poor signal-to-noise ratio from the photoreceptor when operating at reduced lens aperture or with wavelength limiting filters. A system is described which uses sweep frequency sine wave targets with rectification and filtering of the electrical signal to reduce the required band width thereby overcoming these difficulties. Rapid scanning with oscilloscope presentation is used for preliminary adjustment of lens parameters. An X-Y recorder combines curves for a number of lens adjustments on preprinted paper for permanent records at a rate of ten seconds per curve.