Minnesota Mining and Manufacturing Company

Richard Owen

Charles C Lee

Bruce H Koehler

Lyle A Bleeker

An exposure control apparatus for a microfilm printer includes an area (planar) light source, photo detector, and digital control circuits. An averaged density reading over at least the central five to twenty percent of the area of the microfilm frame is measured. This density reading is then used to control the intensity of the exposure lamp via a digital control circuit. The spatial relationships between the elements of the light source, the microfilm frame being read, and the photodetector are optimally arranged to provide an even illumination of the portion of the microfilm frame being measured without interfering with the film exposure process and without creating undue space demands. The microfilm density measurement provided by the apparatus is used to automatically control the intensity of the exposure lamp used in the exposure of a light sensitive medium in the development of prints from the microfilm. The exposure lamp light intensity that corresponds to the threshold level of the light sensitive medium (the minimum light exposure level that will form an image with no film in the exposure station) is established as the zero density threshold intensity. A threshold offset that corresponds to the measured density of a microfilm frame to be printed is added to the zero density threshold intensity to establish a desired exposure lamp intensity for exposing the microfilm frame for printing.

Automatic exposure control apparatus for a microfilm printer

The printer disclosed converts electronic information into human readable information by an imaging device comprising a laser diode which is a source of coherent monochromatic radiation requiring very low power to expose a sensitized sheet. The radiation from the laser diode may scan a focal plane on which the radiation is focused by an objective lens and compounded curved mirror such as a parabolic mirror. The medium for the image is a zinc oxide sensitized sheet.

Laser diode printer

A unitary optical element as provided together with a tubular light source and housing therearound to form an integrated optical assembly suitable for illuminating a line of a graphic original traversed across one surface of the assembly, such that an image of the illuminated line is formed on a photoreceptive surface traversed across another surface of the assembly. The optical element includes a linear array of optical fibers for conveying light reflected from the original onto the receptor surface, which fibers are optically coupled and integrally bonded to a light collection member such that light from the tubular source is directed onto the collection member and over into the sides of the fibers to emerge through the fiber end, thus directly illuminating a line on the original.

Growing community of inventors

Minneapolis, MN, United States of America

Richard Owen