Method and Apparatus for Measuring Flange Back Focus and Calibrating Track Length Scales of Photographic Objective Lenses

摘要

The illuminated object is brought to focus by a microscope objective lens in a focal plane. This image acts as the object for the lens under test. The position of the focal plane is adjusted by moving the object generator/viewing stage in the form of an autocollimator with a split beam eyepiece until it is coincident with the infinity focal plane of the lens under test. When this condition has been achieved, light transmitted by the test lens will be collimated. This collimated beam is reflected by a plane mirror and re-enters the test lens to be imaged in the focal plane and provide a well-focussed image as viewed by through the eyepiece. This image is also available for analysis using photoelectric techniques.

主权项

1. A method for establishing infinity back focus of a cinematographic lens of the type having a focal point, said method comprising the steps of:
(a) focusing light from an illuminated image of an object to a focal plane and through the lens; (b) reflecting the light back through the lens and the focal plane to a position wherein the image can be observed; (c) moving the focal plane relative to the lens; (d) observing the focus of the image as the focal plane is moved relative to the lens; and (e) setting the position of the focal plane to coincide with the focal point of the lens by observing the sharpness of the image.