Method and device for determining the focal length of a long foc

Details Method and device for determining the focal length of a long foc Method and device for determining the focal length of a long foc

1979-06-14

1981-01-20

Dixon, Harold A.

Radiant energy

Irradiation of objects or material

Irradiation of semiconductor devices

250311, 250396R, A61K 2702

Patent

active

042464870

ABSTRACT:
A method and a device used for determining the focal length of a long focal length electron optical lens particularly used with a microprojector characterized by projecting a bundle of parallel rays along the axis of the long focal length lens, said bundle of rays having a ring-shaped cross section with a radius R, providing a pinhole diaphragm having a diameter which corresponds approximately to the diameter of the circle of least confusion of the lens for a ring-shaped bundle of parallel rays, either positioning the diaphragm axially relative to the lens or holding the diaphragm fixed and changing the excitement of the lens to obtain the least influence of the diaphragm on the bundle of rays passing through the pinhole diaphragm, detecting the image of the rays passing through the diaphragm on a plane at a distance z.sub.2 from the diaphragm, measuring the radius r of the image of the ring-shaped bundle of rays on the plane and then determining the focal length f from the magnitude of R, r, z.sub.2 according to the formula f=(R/r).multidot.z.sub.2. The device includes an annular field stop for producing the bundle of rays having a ring-shaped cross section, means for positioning the field stop in that path of the rays prior to their reaching the lens, a diaphragm having an aperture of the circle of least confusion for the lenses of the ring-shaped bundle of parallel rays and means for recording the image passing through the diaphragm.

REFERENCES:
patent: 3795813 (1974-03-01), Kunath

Affiliated with

Also associated with

Rating

Method and device for determining the focal length of a long foc does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method and device for determining the focal length of a long foc, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and device for determining the focal length of a long foc will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1768691