Narrow bandpass filter assemblies for solar telescopes

US007397604B2

(12;

United States Patent

Hruska

(io) Patent No.: (45) Date of Patent:

US 7,397,604 B2 Jul. 8, 2008

(54) NARROW BANDPASS FILTER ASSEMBLIES FOR SOLAR TELESCOPES

(75) Inventor: Curtis Ross Hruska, 895 Colleen Dr., Windsor, CA (US) 95492

(73) Assignee: Curtis Ross Hruska, Windsor, CA (US)

( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 272 days.

(21) Appl.No.: 11/415,257

(22) Filed: Apr. 29, 2006

(65) Prior Publication Data

US 2007/0253063 Al Nov. 1, 2007

(51) Int. CI.

G02B 27/28 (2006.01)

(52) U.S. CI 359/498; 359/589; 359/260;

359/261

(58) Field of Classification Search None

See application file for complete search history.

(56) References Cited

U.S. PATENT DOCUMENTS

. 359/497

The invention relates to the combination of lower transmit tance etalons with higher transmittance filters, including use of a single circular polarizer with high efficiency and optical performance for its filtered polarization, to achieve necessary throughput of a narrow bandpass region. The lower transmittance etalons can be achieved by using lower transmittance solid-state etalon materials, or by control of the coatings on the etalon. Alternate configurations are described that reduce the optical assembly's footprint, and/or include additional filters to remove stray light. An innovative option to heat the etalon directly is disclosed to actively stabilize and maintain the etalon's bandpass.

20 Claims, 2 Drawing Sheets

OTHER PUBLICATIONS

J. A. Dobrowolski, Coatings and Filters, chapter in Handbook of
Optics, Walter Driscoll, editor, 1978, p. 8-81; pp. 8-84 to
8-85,McGraw-Hill Book Company, New York, NY.
Donald G. Carson, L. Dean Canfield, and Marshall L. Ogne, Final
Report: An Evaluation of Interference Fitlers for Hydrogen-alpha

Telescopes for the Apollo Telescope Mount, LMSC-680238, Nov. 1967, pp. 66-70, 73-76, Lockheed Missiles & Space Company. Edwin Hirsch, Photographing the Sun in H-Alpha, Astronomy magazine, Jan. 1978, pp. 37-39, AstroMedia Corp.

* cited by examiner