Optical systems

An optical assembly comprising:

• an integral lens assembly comprising one or more lenses bonded to each other and comprising spaced apart major first and second lens surfaces;
• and
• first and second optical films bonded to the respective major first and second lens surfaces, each of the first and second optical films comprising a plurality of polymeric layers numbering at least 10 in total, each of the polymeric layers having an average thickness of less than about 500 nm, such that for a substantially normally incident light and a visible wavelength range extending from about 420 nm to about 680 nm:
• the plurality of polymeric layers in the first optical film has an average optical transmittance of greater than about 70% for a first polarization state and an average optical reflectance of greater than about 70% for an orthogonal second polarization state in the visible wavelength range;
• and
• the plurality of polymeric layers in the second optical film has an average optical transmittance of greater than about 70% for at least one of the first and second polarization states in the visible wavelength range,
• wherein the first and second optical films have respective average thicknesses T1 and T2, respective elastic stiffnesses Q1 and Q2 in a same first direction, respective thermal strains E1 and E2 in a same second direction, and respective coefficients of thermal expansion A1 and A2 in a same third direction, the third direction being within 20 degrees of the first direction, wherein:
• products Q1×T1×E1 and Q2×T2×E2 are within 20% of each other, and/or
• products Q1×T1×A1 and Q2×T2×A2 are within 20% of each other.