Patent ID: 11960683
Assignee: 3M INNOVATIVE PROPERTIES COMPANY
Field: Optics (Instruments)
Classification: CPC G | IPC F  G

Claim 16:
17. A display system for sensing a finger of a user applied to the display system, the display system comprising:
a display panel configured to generate an image for viewing by the user;
a sensor for sensing the finger of the user disposed proximate the display panel;
a sensing light source configured to emit a first light having a first wavelength W1 toward the finger of the user, the sensor configured to receive and detect at least a portion of the first light reflected by the finger; and
a reflective polarizer disposed between the display panel and the sensor and comprising a plurality of polymeric layers numbering at least 50 in total, such that for a substantially normally incident light, an optical transmittance of the reflective polarizer versus wavelength for a first polarization state comprises a band edge, wherein:
a best linear fit to the band edge correlating the optical transmittance to the wavelength at least across a wavelength range where the optical transmittance along the band edge increases from about 10% to at least about 70% has a slope of greater than about 2.5%/nm; and
for a first wavelength range extending from a smaller wavelength L1 to a greater wavelength L2 and comprising W1, 30 nm≤L2−L1≤50 nm, L1 greater than and within about 20 nm of a wavelength L3 corresponding to an optical transmittance of about 50% along the band edge, the optical transmittance has an average of greater than about 75%,
wherein the reflective polarizer further comprises:
a first outer layer co-extruded with the plurality of polymeric layers;
a plurality of first particles having an average size of from about 7 to about 9 microns and partially protruding from a first major surface of the first outer layer to form a first structured major surface; and
a first optically diffusive layer conformably disposed on the first structured major surface so that opposing first and second major surfaces of the first optically diffusive layer substantially conform to the first structured major surface, the first optically diffusive layer comprising a plurality of nanoparticles dispersed therein, the nanoparticles defining a plurality of voids therebetween.