US3637294A
Expired / Lapsed
US
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Interference filter with alternately designed pairs of dielectric layers
Assignee: AT&T Inc
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Filing: 1969-12-19
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Granted: 1972-01-25
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Expires: 1989-12-19
Abstract
Abstract This filter comprises a plurality of superimposed layers in which layers of a first material having a first index of refraction alternate with layers of a second material having a second index of refraction, thereby defining a plurality of highindex-low-index pairs of layers, and at least some high-indexlow-index pairs of layers having a first optical thickness alternate with at least some high-index-low-index pairs of layers having a second optical thickness. Also described is an optimized design derived from this filter. Such filters can be formed by deposition of the layers on a substrate by calculating in advance the slope of the reflectance versus thickness curve that should be observed when each layer has its desired thickness and then, when forming the layers, by terminating the deposition of each layer when the slope of the reflectance versus thickness curve for the layer being deposited equals the calculated slope.
Inventors
- 👤 John W Berthold
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 05:45
CPC Classifications
G; G02; G02B; G02B5/00; G02B5/20; G02B5/28; G02B5/285
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
113 words
An optical filter comprising a plurality of superimposed layers in which layers of a first material having a first index of refraction alternate with layers of a second material having a second index of refraction, thereby defining a plurality of highindex- low-index pairs of layers, characterized in that at least some high-index- low-index pairs of layers in which each layer has a first optical thickness alternate with at least some highindex- low-index pairs of layers in which each layer has a second optical thickness to form a filter in which the pattern of layer thickness is AABB . . . AABB where A represents one optical thickness and B the other optical thickness.
Claim 2
Dependent Claim
113 words
An optical filter comprising a plurality of superimposed layers in which layers of a first material having a first index of refraction alternate with layers of a second material having a second index of refraction, thereby defining a plurality of highindex- low-index pairs of layers, characterized in that at least some high-index- low-index pairs of layers in which each layer has a first optical thickness alternate with at least some highindex- low-index pairs of layers in which each layer has a second optical thickness to form a filter in which the pattern of layer thickness is AABB . . . AABB where A represents one optical thickness and B the other optical thickness.
Claim 3
Dependent Claim
45 words
The filter of claim 1 further characterized in that at least some high-index- low-index pairs of layers in which each layer has a third optical thickness alternate with at least some high-index- low-index pairs of layers in which each layer has a fourth optical thickness.
Claim 4
Dependent Claim
45 words
The filter of claim 2 further characterized in that at least some high-index- low-index pairs of layers in which each layer has a fifth optical thickness alternate with at least some high-index- low-index pairs of layers in which each layer has a sixth optical thickness.
Claim 5
Dependent Claim
78 words
The filter of claim 3 in which the ratio of the first optical thickness to the second optical thickness is 41/49, the ratio of the first optical thickness to the third optical thickness is 41/55, the ratio of the first optical thickness to the fourth optical thickness is 41/70, the ratio of the first optical thickness to the fifth optical thickness is 41/78, and the ratio of the first optical thickness to the sixth optical thickness is 41/89.
Claim 6
Dependent Claim
122 words
The filter of claim 1 wherein the relative optical thicknesses of the layers are as follows: Relative Relative Layer Optical Layer Optical No. Thickness No. Thickness substrate 1 0.63 25 0.55 2 0.41 26 0.70 3 0.41 27 0.70 4 0.49 28 0.55 5 0.49 29 0.55 6 0.41 30 0.70 7 0.41 31 0.70 8 0.49 32 0.55 9 0.49 33 0.55 10 0.41 34 0.89 11 0.41 35 0.89 12 0.49 36 0.78 13 0.49 37 0.78 14 0.41 38 0.89 15 0.41 39 0.89 16 0.49 40 0.78 17 0.49 41 0.78 18 0.41 42 0.89 19 0.41 43 0.89 20 0.55 44 0.78 21 0.55 45 0.78 22 0.70 46 0.89 23 0.70 47 0.89 24 0.55 air
Claim 7
Dependent Claim
136 words
The filter of claim 5 wherein the quarterwave optical thickness of each layer, said quarterwave optical thickness being four times actual optical thickness, is as follows: 1/4 -Wave 1/4 -Wave Optical Optical Layer Thickness Layer Thickness No. (microns) No. (microns) substrate 1 0.63 25 0.60 2 0.45 26 0.70 3 0.45 27 0.70 4 0.47 28 0.55 5 0.47 29 0.55 6 0.41 30 0.73 7 0.41 31 0.68 8 0.49 32 0.53 9 0.49 33 0.51 10 0.41 34 0.89 11 0.41 35 0.89 12 0.49 36 0.82 13 0.49 37 0.78 14 0.47 38 0.89 15 0.47 39 0.89 16 0.49 40 0.78 17 0.49 41 0.82 18 0.47 42 0.89 19 0.47 43 0.84 20 0.51 44 0.78 21 0.51 45 0.78 22 0.60 46 0.89 23 0.53 47 0.84 24 0.60 air
Claim 8
Independent Claim
210 words
A method of desigNing an optical filter that substantially has a desired reflectance and comprises a plurality of superimposed layers in which layers of a first material having a first index of refraction alternate with layers of a second material having a second index of refraction, thereby defining a plurality of high-index- low-index pairs of layers, comprising the steps of: forming an initial design in which is specified the relative optical thickness of each of several layers of the optical coating, and varying the relative optical thickness of layers of the initial design to alter the reflectance of the coating toward the reflectance that is desired, characterized in that the step of forming the initial design comprises the step of forming a design in which the relative optical thickness of the layers in at least some high-index-low-index pairs of layers are the same and at least some high-index- low-index pairs of layers in which each layer has a first relative optical thickness alternate with at least some high-index- low-index pairs of layers in which each layer has a second relative optical thickness so that the pattern of layer thicknesses in the design is AABB . . . AABB where A represents one optical thickness and B the other optical thickness.
Claim 9
Independent Claim
210 words
A method of desigNing an optical filter that substantially has a desired reflectance and comprises a plurality of superimposed layers in which layers of a first material having a first index of refraction alternate with layers of a second material having a second index of refraction, thereby defining a plurality of high-index- low-index pairs of layers, comprising the steps of: forming an initial design in which is specified the relative optical thickness of each of several layers of the optical coating, and varying the relative optical thickness of layers of the initial design to alter the reflectance of the coating toward the reflectance that is desired, characterized in that the step of forming the initial design comprises the step of forming a design in which the relative optical thickness of the layers in at least some high-index-low-index pairs of layers are the same and at least some high-index- low-index pairs of layers in which each layer has a first relative optical thickness alternate with at least some high-index- low-index pairs of layers in which each layer has a second relative optical thickness so that the pattern of layer thicknesses in the design is AABB . . . AABB where A represents one optical thickness and B the other optical thickness.
Claim 10
Dependent Claim
158 words
The method of claim 7 further characterized in that the step of forming the initial design comprises the step of forming a design in which the relative optical thicknesses of the layers in at least some high-index- low-index pairs of layers are the same, at least some high-index- low-index pairs of layers in which each layer has a first relative optical thickness alternate with at least some high-index- low-index pairs of layers in which each layer has a second relative optical thickness, at least some high-index- low-index pairs of layers in which each layer has a third relative optical thickness alternate with at least some high-index- low-index pairs of layers in which each layer has a fourth relative optical thickness, and at least some high-index-low-index pairs of layers in which each layer has a fifth relative optical thickness alternate with at least some high-index- low-index pairs of layers in which each layer has a sixth relative optical thickness.
Claim 11
Dependent Claim
84 words
The method of claim 8 further characterized in that in the initial design the ratio of the first optical thickness to the second optical thickness is 41/49, the ratio of the first optical thickness to the third optical thickness is 41/55, the ratio of the first optical thickness to the fourth optical thickness is 41/70, the ratio of the first optical thickness to the fifth optical thickness is 41/78, and the ratio of the first optical thickness to the sixth optical thickness is 41/89.
Claim 12
Independent Claim
121 words
The method of forming an optical filter on a substrate comprising the steps of: calculating in advance of the formation of the optical coating a slope of a plot of reflectance versus layer thickness that should be observed when each layer to be formed has various incremental optical thicknesses, comparing during the fabrication of the filter the slope of a reflectance versus optical thickness plot that is observed with the slope of reflectance versus layer thickness that has been calculated, and terminating formation of a layer when the slope of the reflectance versus thickness plot that is observed becomes substantially the same as the slope that was calculated in advance for the particular optical thickness that is desired for the layer.
Claim 13
Independent Claim
121 words
The method of forming an optical filter on a substrate comprising the steps of: calculating in advance of the formation of the optical coating a slope of a plot of reflectance versus layer thickness that should be observed when each layer to be formed has various incremental optical thicknesses, comparing during the fabrication of the filter the slope of a reflectance versus optical thickness plot that is observed with the slope of reflectance versus layer thickness that has been calculated, and terminating formation of a layer when the slope of the reflectance versus thickness plot that is observed becomes substantially the same as the slope that was calculated in advance for the particular optical thickness that is desired for the layer.
References Cited (Backward Citations)
FR1028899A
Cited
US2624238A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-01-24 | 1975-07-26 | 1976-01-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-01-24 | 1979-07-26 | 1980-01-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-01-24 | 1983-07-26 | 1984-01-25 | $7700.00 | Window Closed / Lapsed |