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US 7,692,746 B2Granted
Digitally-switchable bandpass filter
AssigneeReal D
InventorGary D. Sharp
Life of this patent
Estimating the term…
Abstract
Disclosed are digitally-switchable bandpass filters combining non-tunable retarder stacks with switchable liquid crystal cells. The disclosed filter embodiments function like a filter wheel with no moving parts that may provide faster switching, better image registration, compact size, and lower electrical power consumption. These benefits are attractive in portable handheld devices, such as bio-hazard sensors or glucose monitors.
Claims35
An optical filter for filtering a beam of light passing through it, the optical filter comprising:
- a retarder stack, the retarder stack comprising at least three retarder layers wherein the retarder layers have substantially the same retardance values, and the retarder angles of the retarder layers are substantially symmetric relative to the middle of the retarder stack;
- a liquid crystal cell adjacent to the retarder stack, the liquid crystal having a voltage input and operable at least at a certain input voltage signal at its voltage input to impart no change of the state of polarization of the light beam passing through the optical filter;
- and
- first and second polarizers on opposite sides of the adjacent retarder stack and liquid crystal cell such that polarization of the beam of light remains substantially unchanged between the liquid crystal cell and the one of the first and second polarizers that is adjacent to the liquid crystal cell.
1 more element
An optical filter for filtering a beam of light passing through it, the optical filter comprising:
- a first retarder stack, the first retarder stack comprising at least three retarder layers wherein the retarder layers have substantially the same retardance values, and the retarder angles of the retarder layers are substantially symmetric relative to the middle of the retarder stack;
- a first liquid crystal cell adjacent to the first retarder stack, the first liquid crystal having a voltage input and operable at least at a certain input voltage signal at its voltage input to impart no change of the state of polarization of the beam of light passing through the optical filter;
- first and second polarizers on opposite sides of the adjacent first retarder stack and first liquid crystal cell;
- a second retarder stack;
- a second liquid crystal cell, the second liquid crystal having a voltage input and operable at least at a certain input voltage signal at its voltage input to impart no change of the state of polarization of the beam of light passing through the optical filter,
- the second retarder stack and second liquid cell positioned adjacent to each other and collectively adjacent to one of the first and second polarizers;
- and
- a third polarizer positioned such that the collectively adjacent second retarder stack and second liquid crystal cell are interposed between the third polarizer and the one of the first and second polarizers, and such that polarization of the beam of light remains substantially unchanged between the second liquid crystal cell and the third polarizer.
5 more elements
A digitally tuned optical filter having digitally tuned optical filtering characteristics, the digitally tuned optical filter comprising:
- a first retarder stack, the first retarder stack comprising at least three retarder layers wherein the retarder layers have substantially the same retardance values, and the retarder angles of the retarder layers are substantially symmetric relative to the middle of the retarder stack;
- a first liquid crystal cell adjacent to the first retarder stack, the first liquid crystal having a voltage input and operable at least at a certain input voltage signal at its voltage input to impart no change of the state of polarization of a beam of light passing through the optical filter;
- first and second polarizers on opposite sides of the adjacent first retarder stack and first liquid crystal cell;
- a second retarder stack;
- a second liquid crystal cell, the second liquid crystal having a voltage input and operable at least at a certain input voltage signal at its voltage input to impart no change of the state of polarization of the beam of light passing through the optical filter,
- the second retarder stack and second liquid cell positioned adjacent to each other and collectively adjacent to one of the first and second polarizers;
- a third polarizer positioned such that the collectively adjacent second retarder stack and second liquid crystal cell are interposed between the third polarizer and the one of the first and second polarizers, and such that polarization of the beam of light remains substantially unchanged between the second liquid crystal cell and the third polarizer;
- and
- a controller in electrical communication with the first and second liquid crystal cells, the controller operable to apply at least first and second sets of input voltage signals to the first and second liquid crystal cells to thereby tune the filtering characteristics of the optical filter.
6 more elements
A spectrometry system for measuring a signature light from a sample to be measured, the spectrometry system comprising:
- a light source;
- optical components operable to focus light from the light source onto the sample to be measured;
- a digitally tuned optical filter having digitally tuned optical filtering characteristics, comprising:
- a first retarder stack, the first retarder stack comprising at least three retarder layers wherein the retarder layers have substantially the same retardance values, and the retarder angles of the retarder layers are substantially symmetric relative to the middle of the retarder stack;
- a first liquid crystal cell adjacent to the first retarder stack, the first liquid crystal having a voltage input and operable at least at a certain input voltage signal at its voltage input to impart no change of the state of polarization of the beam of light passing through the optical filter;
- first and second polarizers on opposite sides of the adjacent first retarder stack and first liquid crystal cell;
- a second retarder stack;
- a second liquid crystal cell, the second liquid crystal having a voltage input and operable at least at a certain input voltage signal at its voltage input to impart no change of the state of polarization of the beam of light passing through the optical filter,
- the second retarder stack and second liquid cell positioned adjacent to each other and collectively adjacent to one of the first and second polarizers;
- a third polarizer positioned such that the collectively adjacent second retarder stack and second liquid crystal cell are interposed between the third polarizer and the one of the first and second polarizers, and such that polarization of the beam of light remains substantially unchanged between the second liquid crystal cell and the third polarizer;
- and
- a controller in electrical communication with the first and second liquid crystal cells, the controller operable to apply at least first and second sets of input voltage signals to the first and second liquid crystal cells to thereby tune the filtering characteristics of the optical filter;
- and
- an optical sensor positioned to receive light from the sample.
11 more elements
An optical imaging system using a digitally tuned filter comprising:
- optical components operable to focus light from a light source;
- and
- a digitally tuned optical filter having digitally tuned optical filtering characteristics, comprising:
- a first retarder stack, the first retarder stack comprising at least three retarder layers wherein the retarder layers have substantially the same retardance values, and the retarder angles of the retarder layers are substantially symmetric relative to the middle of the retarder stack;
- a first liquid crystal cell adjacent to the first retarder stack, the first liquid crystal having a voltage input and operable at least at a certain input voltage signal at its voltage input to impart no change of the state of polarization of the beam of light passing through the optical filter;
- first and second polarizers on opposite sides of the adjacent first retarder stack and first liquid crystal cell;
- a second retarder stack;
- a second liquid crystal cell, the second liquid crystal having a voltage input and operable at least at a certain input voltage signal at its voltage input to impart no change of the state of polarization of the beam of light passing through the optical filter,
- the second retarder stack and second liquid cell positioned adjacent to each other and collectively adjacent to one of the first and second polarizers;
- a third polarizer positioned such that the collectively adjacent second retarder stack and second liquid crystal cell are interposed between the third polarizer and the one of the first and second polarizers, and such that polarization of the beam of light remains substantially unchanged between the second liquid crystal cell and the third polarizer;
- and
- a controller in electrical communication with the first and second liquid crystal cells, the controller operable to apply at least first and second sets of input voltage signals to the first and second liquid crystal cells to thereby tune the filtering characteristics of the optical filter.
9 more elements
Dependencies are inferred from the claim text.