Optical: systems and elements – Light interference – Produced by coating or lamina
Patent
1998-07-30
2000-02-01
Henry, Jon
Optical: systems and elements
Light interference
Produced by coating or lamina
359586, 359588, 359589, G02B 111, G02B 528
Patent
active
06021001&
ABSTRACT:
A filter (10) for selectively transmitting electromagnetic energy over a range of frequencies (28, 30, 32) adapted for use with white light (24). The filter (10) includes rugate layers (18, 20) for creating a resonant cavity that resonates at desired bandpass frequencies (28, 30, 32). An absorptive layer (12) absorbs frequencies near the bandpass frequencies (28, 30, 32) and reflects frequencies outside the bandpass frequencies (28, 30, 32). Phase matching layers (14, 16) allow the transmission of electromagnetic energy within the transmission bands (28, 30, 32) through the absorption layer 12. In an illustrative embodiment, the bandpass frequencies (28, 30, 32) comprise the three tristimulus frequencies, i.e., red (28), green (30) and blue (32) frequencies. The rugate layers (18, 20) include first (18) and second (20) rugate layers made of SiO.sub.2 and Ta.sub.2 O.sub.5, respectively. Located between the first (18) and second (20) rugate layers is the absorption layer (12) that is surrounded by the first (14) and second (16) phase matching layers. The absorption layer (12) is a silver layer that is approximately 500 angstroms thick. The first rugate layer (18) has a first index of refraction versus layer thickness profile representing a superposition of sinusoids. Each sinusoid has a frequency directly corresponding to tristimulus band frequency. The second rugate layer (20) has a second index of refraction versus layer thickness profile that is a phase-adjusted version of the first index of refraction versus layer thickness profile. Both rugate layers (18, 20) have index or refraction versus layer thickness profiles have several cycles.
REFERENCES:
patent: 5004308 (1991-04-01), Hall et al.
patent: 5056099 (1991-10-01), Bradley
Henry Jon
Lenzen, Jr. Glenn H.
Raytheon Company
Schubert William C.
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