Optical filter with color enhancement
An eyewear lens is described that provides polarization filtering and spectral filtering using polarization interference. The lens produces enhanced saturation and colorfulness, increasing enjoyment when observing commonly encountered imagery. The lens can be configured to optimize accuracy/efficiency when performing a task involving colored imagery, and can improve performance in sports. The lens can further be helpful for color discrimination by those with certain types of color vision deficiency.
1. An optical filter, comprising:
a polarization interference filter (PIF), including at least:
an input polarizer;
one or more retarders; and
an output polarizer;
wherein the PIF has a transmission across the 400 nm to 700 nm spectrum that is substantially sinusoidal having minimums and maximums, and with a single maximum in the 555 nm to 610 nm range, a single maximum in the 400 nm to 480 nm range, and at least one minimum in the 480 nm to 515 nm range.
2. An optical filter as defined in claim 1 , wherein the optical filter provides color enhancement to a person with color vision deficiency.
3. An optical filter, comprising:
a polarization interference filter (PIF), including at least:
an input polarizer having an axis of polarization at a first angle;
an input chromatic uniaxial retarder with an optical axis that is offset by +45 degrees from the first angle, and having a first retardance value;
a pair of zero-order have-wave retarders forming an achromatic rotator, with angles of substantially +21.5 degrees and substantially −21.5 degrees therebetween;
an output chromatic uniaxial retarder with an optical axis that is offset by −45 degrees from the first angle, and having the first retardance value; and
an output polarizer having an axis of polarization at a second angle that is either parallel to or perpendicular to the first angle;
wherein the optical filter has a wide field of view with a Δxy color shift at 30 degrees off-axis of 0.05 or less.
4. An optical filter as defined in claim 3 , wherein the PIF has a transmission across the 400 nm to 700 nm spectrum that is substantially sinusoidal having minimums and maximums, and with a single maximum in the 610 nm to 680 nm range, a single maximum in the 520 nm to 555 nm range, and at least one maximum in the 455 nm to 480 nm range, and with a single minimum in the 485 nm to 515 nm range, a single minimum in the 565 nm to 590 nm range, and at least one minimum in the 400 nm to 450 nm range.
5. An optical filter, including:
an input polarizer;
one or more chromatic retarders; and
an analyzing polarizer;
wherein at least one of the polarizers has a chromatic polarizing efficiency to increase the transmission of one or more spectral bands relative to one or more other spectral bands.
6. An optical filter as defined in claim 5 , wherein the analyzing polarizer has a relatively lower polarizing efficiency in the 610 nm to 700 nm range than in the 400 nm to 610 nm range.
7. An optical filter as defined in claim 5 , wherein the polarizers have axes of polarization that are perpendicular to each other; and wherein the optical filter further includes a Polarization Control Unit (PCU), including one or more zero-order half-wave uniaxial retarders.