A multi-exposure, high resolution camera for the production of a resolving power test target, with extended range

Since 1888, a series of mutually perpendicular lines have been used as a test object for evaluation of optics, systems, products, etc. The availability of such test objects has traditionally been in the frequency range of about one cycle per millimeter to a couple hundred cycles per millimeter. These have been available from a few manufacturers, none of which offers the extended range of .25 cycles per millimeter to greater than one thousand cycles per millimeter proposed in this project. The usefulness of such an extended range serves to make it an all-purpose test target for measurement of enlarging, contact and reduction systems. Since the test object is on film, it can be used with ease in each of these systems. The actual test object range obtained was from .25 cycles per millimeter to greater than one thousand cycles per millimeter. The camera attained this by a simple but effective three station, multi-exposure method. The advantage of such an exposure method is that optimum independent line width control can be used at each exposure step. Breaking the total frequency range into three groups eases exposure and optical restrictions but does produce mechanical registration problems. It is obvious that with a reasonable budget a sturdier, higher precision and more reproducible instrument could be built such that this extended range resolving power test target could be produced on a production basis