Patent ID: 11899192
Assignee: 3M INNOVATIVE PROPERTIES COMPANY
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 0:
1. An optical system for displaying an image to a viewer comprising:
a first lens comprising a birefringence of less than about 10 nm/cm and a second lens comprising a birefringence of greater than about 10 nm/cm;
a partial reflector disposed on and conforming to a curved major surface of the first lens and having an average optical reflectance of at least 30% in a predetermined wavelength range; and
a reflective polarizer disposed on and conforming to a curved major surface of the second lens;
wherein, a light ray propagating along an optical axis of the optical system, passes through the first and second lenses, the partial reflector and the reflective polarizer without being substantially refracted, and wherein for a cone of light that is incident on the optical system from an object having a spatial frequency of about 70 line pairs per millimeter and comprises a chief ray that after passing through the optical system makes an angle of about 20 degrees with the optical axis, a modulation transfer function (MTF) of the optical system is greater than about 0.2.