Neutral density filters

Details Neutral density filters Neutral density filters

1990-01-17

1991-05-28

Moskowitz, Nelson

350313, 350316, G02B 528, B32B 1504

Patent

active

050188330

ABSTRACT:
A neutral density filter is made by providing a substrate including a volume absorber having a first density and having an uneven first attenuation characteristic, and providing for a substantially constant attenuation of light by depositing on a backside of the volume absorber a thin-film attenuator having light reflective properties attenuated by the volume attenuator, having a second density and a second attenuation characteristic substantially complementing the first attenuation characteristic to provide the neutral density filter with a substantially constant attenuation at a density substantially equal to the first and second densities. The volume absorber and thin film attenuator are positioned so that incoming light first traverses the volume absorber and then the thin-film attenuator. An antireflection coating may be deposited on a front side of the volume absorber.

REFERENCES:
patent: 3236290 (1966-02-01), Lueder
patent: 3649359 (1972-03-01), Apfel et al.
patent: 3679291 (1972-07-01), Apfel et al.
patent: 3781089 (1973-12-01), Fay et al.
patent: 3897140 (1975-07-01), Tuthill
patent: 3920533 (1975-11-01), Pompei
patent: 3936579 (1976-02-01), Ogasawara
"Thin-Film Optical Filters," H. A. MacLeod, (Macmillan Publishing Company, New York, Second Edition, 186), p. 155.
"Absolute Reference Calorimeter for Measuring High Power Laser Pulses," D. L. Franzen and L. B. Schmidt, Applied Optics, vol. 1, Dec. 1976, pp. 3115 to 3117.
"Laser Exposure Testing," Montana Laser Optics (1988).
"Thin-Film Optical Filters," H. A. Macleod, (Macmillan Publishing Company, New York, Second Edition, 186), p. 155.
"Absolute Reference Calorimeter for Measuring High Power Laser Pulses," D. L. Franzen and L. B. Schmidt, Applied Optics, vol. 15, Dec. 1976, pp. 3115 to 3117.
"Laser Exposure Testing," Montana Laser Optics (1988).

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