Method and apparatus for suppressing stray light in particle detectors

(12) United States Patent

Johnson

US006414754B1

(io) Patent No.: US 6,414,754 Bl (45) Date of Patent: Jul. 2,2002

(54) METHOD AND APPARATUS FOR

SUPPRESSING STRAY LIGHT IN PARTICLE
DETECTORS

(75) Inventor: Joel C. Johnson, Lake Oswego, OR
(US)

(73) Assignee: Pacific Scientific Instruments

Company, Grants Pass, OR (US)

( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days.

(21) Appl. No.: 09/521,233

(22) Filed: Mar. 8, 2000

(51) Int. CI.7 G01N 21/00

(52) U.S. CI 356/338; 356/339; 250/222.2;

372/22

(58) Field of Search 356/336, 337,

356/338, 339, 340, 341, 342, 343; 250/574, 575, 423 R, 222.2; 372/22, 51, 53

(56) References Cited

U.S. PATENT DOCUMENTS

3,985,453 A * 10/1976 Nakano et al 250/574

4,162,404 A * 7/1979 Fite et al 250/423 R

5,459,569 A * 10/1995 Knollenberg et al 356/338

5.642.193 A 6/1997 Girvin et al 356/339

5.946.092 A 8/1999 DeFreez et al 356/336

5.946.093 A 8/1999 DeFreez et al 356/339

6,011,622 A * 1/2000 Fishkin et al 356/339

6.016.194 A 1/2000 Girvin et al 356/337

6,091,494 A * 7/2000 Kreikebaum 356/336

OTHER PUBLICATIONS

"Surface Scattering," vol. 1, chapter 7 "Handbook of Optics," second edition, McGraw Hill (1995), ISBN 0-07-047740-X.

"Defect Scattering," vol. 1, chapter 7, p. 7.6 (Included in

chapter 7 ibid.) "Handbook of Optics," second edition,

McGraw Hill (1995), ISBN 0-07-047740-X.

"Control of Stray Light," vol. 1, chapter 38 "Handbook of

Optics," second edition, McGraw Hill (1995), ISBN

0-07-047740-X.

"Contamination Levels," vol. 1, chapter 38, p. 38.18 (Included in chapter 38 ibid.) "Handbook of Optics," second edition, McGraw Hill (1995), ISBN 0-07-047740-X. "Thin-Film Manufacturing Considerations," vol. 1, chapter 42, p. 42.14 "Handbook of Optics," second edition, McGraw Hill (1995), ISBN 0-07-047740-X.

"Surface and Interface Imperfections," vol. 1, chapter 42, p. 42.44. "Handbook of Optics," second edition, McGraw Hill (1995), ISBN 0-07-047740-X.

"Molecular Rayleigh Scattering," vol. 1, chapter 44, p. 44.14 "Handbook of Optics," second edition, McGraw Hill (1995), ISBN 0-07-047740-X.

"Scatter," vol. 2, chapter 33, p. 33.29 "Handbook of Optics," second edition, McGraw Hill (1995), ISBN 0-07-047740-X.

Sandcolor Process Manual, 6 pages (1986?).

Schafer, F.B. et al., "Dye Lasers," pp. 6-9, Springer-Verlag

(1973).

SAF, Batch and Coil Anodizing, 2 pages, (http://www. saf.com/bachncd.html), (Jan. 1994?), printed Feb. 2, 2000. "Current Anodizing Process," 15 pages, (http:// anodizing.org/html/processes.html), (1998), Feb. 2, 2000.

* cited by examiner

Primary Examiner—Frank G. Font

Assistant Examiner—Sang H. Nguyen

(74) Attorney, Agent, or Firm—Stoel Rives LLP

A preferred OPTICAL BLACKTM ionic anodize process of the present invention applies a porous anodic oxide coating to a component part in a standard sulfuric acid anodizing bath (with or without organic additives). A modified alternating electric current is then applied to the porous oxide coating to remove excess anodizing electrolyte and to allow the coloring solution access to the pores. The oxide coating is electrolytically colored in a low pH acid bath containing a tin salt, sulfuric acid, and organic additives. Alternating current carries additional tin salt to the base of the pores where the tin salt is reduced to metallic tin or tin oxide. Others metals or metallic salts could be employed. Component parts treated by the OPTICAL BLACKTM ionic anodize process can be advantageously employed in optical systems, such as particle detectors, to reduce or eliminate stray light.

39 Claims, 3 Drawing Sheets