Reflective polarizer and optical system
An optical system ( 200 ) includes an emissive display ( 220 ) and a reflective polarizer ( 100 ) disposed on the display ( 220 ). The display ( 220 ) includes a blue pixel ( 222 b ) emitting light having a peak at a wavelength λ b . For substantially normally incident light: for the wavelength λ b , the reflective polarizer ( 100 ) reflects at least 30% of the incident light having a first polarization state (b) and transmits at least 75% of the incident light having an orthogonal second polarization state(a); and for at least one wavelength λ 1 greater than λ b , λ 1 -λ b ≤50 nm, the reflective polarizer ( 100 ) transmits at least 75% of the incident light for each of the first and second polarization states. For the wavelength λ b , the reflective polarizer ( 100 ) has a maximum optical transmittance T max for light incident at a first incident angle, and an optical transmittance T max /2 for light incident at a second incident angle greater than the first incident angle by less than about 50 degrees.
1. An optical system comprising:
an emissive display configured to emit an image and comprising a blue pixel configured to emit a blue light, the emitted blue light having a blue peak at a blue wavelength Ab;
a linear absorbing polarizer layer disposed on the display; and
a reflective polarizer disposed between the linear absorbing polarizer layer and the display and configured to receive the image emitted by the display, for substantially normally incident light: for the blue wavelength Ab, the reflective polarizer reflects at least 30% of the incident light having a first polarization state and transmits at least 75% of the incident light having an orthogonal second polarization state; and
for at least one wavelength Ai greater than Ab, Ai-Ab<50 nm, the reflective polarizer transmits at least 75% of the incident light for each of the first and second polarization states; and for the blue wavelength Ab, the reflective polarizer has a maximum optical transmittance T max for light incident at a first incident angle, and an optical transmittance T max /2 for light incident at a second incident angle greater than the first incident angle by less than about 50 degrees.
2. The optical system of claim 1 , wherein the emissive display is configured to emit an image in a visible wavelength range extending at least from about 420 nm to about 650 nm, wherein for the substantially normally incident light and for the first polarization state, an optical transmittance of the reflective polarizer comprises a band edge at least a portion of which is disposed in the visible wavelength range, such that a best linear fit to the band edge correlating the optical transmittance to wavelength at least across a wavelength range where the optical transmittance increases from about 20% of a maximum transmittance of the reflective polarizer in the visible wavelength range to about 70% of the maximum transmittance of the reflective polarizer in the visible wavelength range has a slope that is greater than about 7%/nm.
3. The optical system of claim 1 , wherein the first incident angle is about zero.
4. The optical system of claim 1 , wherein for a substantially normally incident light having a red wavelengths Ar, the reflective polarizer transmits at least 40% of the incident light for each of the first and second polarization states; and for a light having a red wavelength Ar and incident at an incident angle greater than about 20 degrees, the reflective polarizer reflects at least 50% of light having the first polarization state and transmits at least 50% of light having the second polarization state.