Optical system and wearable display apparatus having the same

A method of guiding light in an optical system that includes a first waveguide, a first transmissive reflective layer formed to cover a top surface of the first waveguide, a second waveguide, a second transmissive reflective layer formed to cover a top surface of the second waveguide, a third waveguide, an in-coupler, and an out-coupler, the method of guiding the light comprising:

• transmitting the light through the in-coupler, thereby causing the light to be incident on the first transmissive reflective layer;
• reflecting, by the first transmissive reflective layer, a first portion of the light incident on the first transmissive reflective layer to be incident on the first waveguide,
• transmitting, through the first transmissive reflective layer, a second portion of the light incident on the first transmissive reflective layer to the second transmissive reflective layer via the second waveguide;
• causing the first portion of the light incident on the first waveguide to be totally internally reflected within the first waveguide and thereby incident on the first transmissive reflective layer;
• reflecting, by the second transmissive reflective layer, a first sub-portion of the second portion of the light incident on the second transmissive reflective layer to be incident on the first transmissive reflective layer,
• transmitting, through the second transmissive reflective layer, a second sub-portion of the second portion of the light incident on the second transmissive reflective layer to the third waveguide;
• causing the second sub-portion of the second portion of the light incident on the third waveguide to be totally internally reflected within the third waveguide and thereby incident on the second transmissive reflective layer;
• causing the light, including the first portion and the second portion of the light, traveling through the first waveguide, the second waveguide, and the third waveguide to be refracted by the out-coupler and thereby be emitted from the optical system,
• wherein the first transmissive reflective layer covers an entirety of the top surface of the first waveguide, and the second transmissive reflective layer covers less than an entirety of the top surface of the second waveguide,
• wherein an entirety of the in-coupler is overlapped by the first transmissive reflective layer and the second transmissive reflective layer,
• wherein an entirety of the out-coupler is overlapped by the first transmissive reflective layer, without being overlapped by the second transmissive reflective layer, and
• wherein the out-coupler is spaced apart from the in-coupler by more than a size of the in-coupler, and the light incident on the in-coupler moves to the first transmissive reflective layer.

A wearable display apparatus comprising:

• a projecting part configured to emit light forming an image;
• and
• an optical system configured to guide the light emitted from the projecting part,
• wherein the optical system comprises:
• a first waveguide configured to guide the light;
• a first transmissive reflective layer provided on a top surface of the first waveguide and configured to reflect a first portion of the light incident thereon and to transmit a second portion of the light incident thereon, the first transmissive reflective layer formed to cover the top surface of the first waveguide;
• a second waveguide provided on a top surface of the first transmissive reflective layer and configured to guide the second portion of the light;
• a second transmissive reflective layer provided on a top surface of the second waveguide and configured to reflect a first sub-portion of the second portion of the light incident thereon, toward the first transmissive reflective layer, and to transmit a second sub-portion of the second portion of the light incident thereon, the second transmissive reflective layer formed to cover the top surface of the second waveguide;
• a third waveguide provided on a top surface of the second transmissive reflective layer and configured to guide the second sub-portion of the second portion of the light;
• an in-coupler provided on the first waveguide and configured to guide the light emitted from the projecting part into the first waveguide;
• and
• an out-coupler provided on one of the first waveguide and the third waveguide and configured to emit the light incident thereon to an outside,
• wherein the first transmissive reflective layer covers an entirety of the top surface of the first waveguide, and the second transmissive reflective layer covers less than an entirety of the top surface of the second waveguide,
• wherein an entirety of the in-coupler is overlapped by the first transmissive reflective layer and the second transmissive reflective layer,
• wherein an entirety of the out-coupler is overlapped by the first transmissive reflective layer, without being overlapped by the second transmissive reflective layer, and
• wherein the out-coupler is spaced apart from the in-coupler by more than a size of the in-coupler, and the light incident on the in-coupler moves to the first transmissive reflective layer.