Display device
A display device includes a light guide plate; an input grating on a first surface of the light guide plate and configured to generate a diffracted transmission beam; an output grating on the first surface of the light guide plate and spaced apart from the input grating, wherein the output grating is configured to generate a first output beam emitted from the light guide plate; and an optical efficiency enhancement layer on a second surface of the light guide plate and overlapping at least one of the input grating and the output grating in a traveling direction of the input beam, the second surface being opposite to the first surface.
1. A display device comprising:
a light guide plate;
an input grating on a first surface of the light guide plate, the input grating being configured to diffract an input beam incident on the first surface at an angle equal to or greater than a critical angle of the light guide plate to generate a diffracted transmission beam propagating within the light guide plate through total internal reflection;
an output grating on the first surface of the light guide plate and spaced apart from the input grating, wherein the output grating is configured to generate a first output beam passing through the output grating and emitted from the light guide plate by diffracting the diffracted transmission beam; and
an optical efficiency enhancement layer on a second surface of the light guide plate and overlapping the output grating in a traveling direction of the input beam, the second surface being opposite to the first surface,
wherein the optical efficiency enhancement layer comprises a polarization reflection plate and a narrowband reflection plate directly on the polarization reflection plate,
wherein the traveling direction of the input beam is substantially perpendicular to a first direction,
wherein a width of the optical efficiency enhancement layer in the first direction is greater than a width of the output grating in the first direction,
wherein the width of the output grating in the first direction is within the width of the optical efficiency enhancement layer in the first direction, and
wherein the width of the optical efficiency enhancement layer in the first direction is less than a width of the light guide plate in the first direction.
2. The display device of claim 1 , wherein a reflectance of the optical efficiency enhancement layer with respect to the input beam is 50% or more.
3. The display device of claim 1 , wherein a reflection bandwidth of the narrowband reflection plate is 40 nm or less.
4. The display device of claim 1 , wherein the optical efficiency enhancement layer comprises:
a first narrowband reflection plate configured to reflect a blue visible beam;
a second narrowband reflection plate configured to reflect a green visible beam; and
a third narrowband reflection plate configured to reflect a red visible beam.
5. The display device of claim 1 , wherein the input grating is configured to transmit a portion of the input beam passing through the input grating and traveling in substantially a same direction as the traveling direction of the input beam within the light guide plate, and
wherein the optical efficiency enhancement layer is configured to reflect the transmitted portion of the input beam.
6. The display device of claim 1 , wherein the output grating is further configured to diffract and reflect a portion of the diffracted transmission beam toward the optical efficiency enhancement layer, and
wherein the optical efficiency enhancement layer is configured to reflect the portion of the diffracted transmission beam back toward the output grating.
7. A display device configured to output a first output beam and a second output beam based on an input beam, the display device comprising:
a light guide plate;
an input grating on a first surface of the light guide plate;
an output grating on the first surface of the light guide plate and spaced apart from the input grating; and
an optical efficiency enhancement layer arranged on a second surface of the light guide plate, the optical efficiency enhancement layer having a reflectance of 50% or more with respect to the input beam,
wherein the first output beam is based on a diffracted transmission beam which is a first portion of the input beam diffracted by the input grating while passing through the input grating,
wherein the second output beam is based on a transmitted input beam which is a second portion of the input beam passing through the input grating and reflected by the optical efficiency enhancement layer,
wherein the first output beam is a portion of the diffracted transmission beam diffracted by the output grating,
wherein the second output beam is based on a first diffracted reflection beam which is a portion of the transmitted input beam that is diffracted and reflected by the input grating after being reflected by the optical efficiency enhancement layer,
wherein a traveling direction of the input beam is substantially perpendicular to a first direction,
wherein a width of the optical efficiency enhancement layer in the first direction is greater than a width of the output grating in the first direction,
wherein the width of the output grating in the first direction is within the width of the optical efficiency enhancement layer in the first direction,
wherein the optical efficiency enhancement layer entirely covers the second surface of the light guide plate, and
wherein the optical efficiency enhancement layer comprises a polarization reflection plate and a narrowband reflection plate directly on the polarization reflection plate.
8. The display device of claim 7 , wherein the second output beam is a portion of the first diffracted reflection beam diffracted by the output grating while passing through the output grating.
9. The display device of claim 7 , wherein the second output beam is based on a second diffracted reflection beam which is a portion of the transmitted input beam diffracted and reflected by the output grating.
10. The display device of claim 9 , wherein the second output beam is a portion of the second diffracted reflection beam passing through the output grating.
11. A display device comprising:
a first display device corresponding to a first input beam, a second display device corresponding to a second input beam, and a third display device corresponding to a third input beam,
wherein the first display device comprises:
a first light guide plate;
a first input grating on a first upper surface of the first light guide plate;
a first output grating on the first upper surface of the first light guide plate and spaced apart from the first input grating; and
a first optical efficiency enhancement layer on a first lower surface of the first light guide plate and being farther from a user's eye than the first upper surface, the first optical efficiency enhancement layer having a reflectance of 50% or more with respect to a first wavelength band of the first input beam, the first lower surface being opposite to the first upper surface,
wherein the second display device comprises:
a second light guide plate;
a second input grating on a second upper surface of the second light guide plate;
a second output grating on the second upper surface of the second light guide plate and spaced apart from the second input grating; and
a second optical efficiency enhancement layer on a second lower surface of the second light guide plate, the second optical efficiency enhancement layer having a reflectance of 50% or more with respect to a second wavelength band of the second input beam, the second lower surface being opposite to the second upper surface,
wherein the third display device comprises:
a third light guide plate;
a third input grating on a third upper surface of the third light guide plate;
a third output grating on the third upper surface of the third light guide plate and spaced apart from the third input grating; and
a third optical efficiency enhancement layer on a third lower surface of the third light guide plate, the third optical efficiency enhancement layer having a reflectance of 50% or more with respect to a third wavelength band of the third input beam, the third lower surface being opposite to the third upper surface,
wherein the first input beam comprises a blue visible beam,
wherein the second input beam comprises a green visible beam,
wherein the third input beam comprises a red visible beam,
wherein at least one of the first optical efficiency enhancement layer, the second optical efficiency enhancement layer, and the third optical efficiency enhancement layer comprises a polarization reflection plate and a narrowband reflection plate directly on the polarization reflection plate,
wherein a traveling direction of the first input beam is substantially perpendicular to a first direction,
wherein a width of the first optical efficiency enhancement layer in the first direction is greater than a width of the first output grating in the first direction,
wherein the width of the first output grating in the first direction is within the width of the first optical efficiency enhancement layer in the first direction, and
wherein the width of the first optical efficiency enhancement layer in the first direction is less than a width of the first light guide plate in the first direction.
12. The display device of claim 11 , wherein the first optical efficiency enhancement layer is transparent to each of the second and third input beams,
wherein the second optical efficiency enhancement layer is transparent to each of the first and third input beams, and
wherein the third optical efficiency enhancement layer is transparent to each of the first and second input beams.