Reflective spatial light modulator display with stacked light guides and method

A display comprising:

• a. a reflective spatial light modulator comprising a reflective surface;
• b. a lightguide having opposing faces with a thickness not greater than about 0.5 millimeters therebetween wherein light propagates by total internal reflection between the opposing faces, the lightguide comprising:
• i). a core layer;
• ii). a cladding layer having a first side optically coupled to the core layer and an opposing second side;
• iii). a light redirecting optical element optically coupled to the second side of the cladding layer;
• iv). an array of coupling lightguides continuous with a lightguide region of the lightguide, each coupling lightguide of the array of coupling lightguides terminates in a bounding edge, and each coupling lightguide is folded in a fold region such that the bounding edges of the array of coupling lightguides are stacked;
• and
• v). a light emitting region comprising a plurality of light extraction features arranged in a pattern that varies spatially in the light emitting region, each of the plurality of light extraction features to frustrate totally internally reflected light propagating within the core layer such that light exits the core layer in the light emitting region into the cladding layer with an angular full-width at half-maximum intensity in an output plane in the cladding layer,
• wherein the lightguide has an average thickness in the light emitting region, the light emitting region has a largest dimension in a plane of the light emitting region, and the largest dimension of the light emitting region divided by the average thickness of the lightguide in the light emitting region is greater than 100;
• and
• c. a light source disposed to emit light into the stacked bounding edges, the light propagating within the array of coupling lightguides to the lightguide region, with light from each coupling lightguide combining and totally internally reflecting within the lightguide region,
• wherein the light redirecting optical element redirects frustrated totally internally reflected light toward the reflective spatial light modulator such that the frustrated totally internally reflected light after redirection has an angle of peak luminous intensity within an angular range from 0 to 30 degrees from a direction perpendicular to the reflective surface of the reflective spatial light modulator.

A method of producing a display, the method comprising:

• a. forming a lightguide from a film having opposing faces with a thickness not greater than about 0.5 millimeters therebetween, the lightguide having an array of coupling lightguides continuous with a lightguide region of the lightguide, each coupling lightguide of the array of coupling lightguides terminating at a bounding edge;
• b. folding each coupling lightguide in a fold region such that the bounding edges of the array of coupling lightguides are stacked;
• c. positioning at least one light source to emit light into the stacked bounding edges, the light propagating within the array of coupling lightguides to the lightguide region of the lightguide, with light from each coupling lightguide combining and totally internally reflecting within the lightguide region;
• d. optically coupling a first side of a cladding region to the lightguide;
• e. optically coupling a light redirecting element to a second side of the cladding region opposite the first side;
• f. forming a plurality of light extraction features in a pattern that varies spatially in a light emitting region of the lightguide, the plurality of light extraction features to frustrate totally internally reflected light within the lightguide region such that frustrated totally internally reflected light exits the lightguide in the light emitting region into the cladding region with an angular full-width at half-maximum intensity in an output plane in the cladding region such that the light redirecting optical element redirects the frustrated totally internally reflected light exiting the lightguide toward the reflective spatial light modulator, the frustrated totally internally reflected light after redirection has a an angle of peak luminous intensity within an angular range from 0 to 30 degrees from a direction perpendicular to the reflective surface of the reflective spatial light modulator;
• and
• g. optically coupling a reflective spatial light modulator to the lightguide.