John F Mader

US Patent:

43553508, Oct 19, 1982

Filed:

Sep 2, 1980

Appl. No.:

6/183105

Inventors:

John J. Mader - Tewksbury MA

Assignee:

Polaroid Corporation - Cambridge MA

International Classification:

F21V 700

US Classification:

362347

Abstract:

A reflector having a cross-sectional shape in the form of a 7th order polynomial which, when used with an artificial source of illumination of predetermined geometry, projects a beam of illumination having uniform intensity within a given solid angle. The polynomial shape is especially selected to provide a reflected, defocused source image, whose size increases with increasing angular divergence of light rays within the beam to compensate for natural losses in illumination which would otherwise occur as a function of angular divergence of light rays from the source when used without the reflector.

US Patent:

44247273, Jan 10, 1984

Filed:

Sep 15, 1980

Appl. No.:

6/187311

Inventors:

John J. Mader - Tewksbury MA

Assignee:

Polaroid Corporation - Cambridge MA

International Classification:

B21K 520
B21D 3710

US Classification:

76107R

Abstract:

A method for making a metal stamping die suitable for use in forming sheet metal reflectors for photographic use. The structure of the metal stamping die is made in the manner of the method to compensate for spring-back characteristics of a material used to form a reflector by first constructing a test die which has a predetermined shape related to the desired reflector shape. A comparison is then made between a test workpiece made with the test die and the desired reflector shape to determine the die shape that produces a corresponding portion of the reflector shape. Finally, another die is constructed by shaping it in accordance with the comparison to obtain a final die shape that will acceptably produce the desired reflector shape.

US Patent:

48169390, Mar 28, 1989

Filed:

Aug 21, 1986

Appl. No.:

6/898527

Inventors:

Vernon E. Ford - So. Hanover MA
Jeremy K. Jones - Marblehead MA
John J. Mader - Tewksbury MA
William T. Plummer - Concord MA

Assignee:

Polaroid Corporation - Cambridge MA

International Classification:

G11B 5596

US Classification:

360 7703

Abstract:

Magnetic recording media, and magnetic recording systems using such media, are disclosed which incorporate a light-transmitting optical grating at least substantially coextensive with the magnetic recording area. A second light-transmitting optical grating is associated with the magnetic transducer or read/write head. A moire pattern is produced by light transmitted through both optical gratings, and changes in the moire pattern resulting from changes in the alignment of the optical gratings resulting from movement of the read/write head relative to the media are utilized to provide servo information to keep the magnetic transducer aligned with the magnetic track. Higher magnetic recording capacities may be obtained using such media and systems, since none of the magnetic recording area is used for servo information.