CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 from Korean Patent Application No. 10-2017-0173927, filed on Dec. 18, 2017, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety.

BACKGROUND

1. Field

Apparatuses and methods consistent with exemplary embodiments relate to an optical system including a waveguide capable of transmitting light and a wearable display apparatus having the same.

2. Description of the Related Art

A wearable display apparatus for providing augmented reality is generally implemented using a head mounted display (HMD) or smart glasses.

Such a wearable display apparatus typically requires an ultra-small and ultra-thin shape while having a wide angle of view and high resolution.

In a wearable display apparatus for implementing such augmented reality, a waveguide is used to guide an image output from a projecting part to a user's eye.

Also, a laser scanning projector using a laser as a light source may be used as the projecting part. The laser scanning projector projects light with a very small diameter.

The waveguide, used to guide the image from the projecting part to the user's eye, is formed so that the thickness of the waveguide is substantially equal to the diameter of the light output from the projecting part. When the diameter of the light entering the waveguide is smaller than the thickness of the waveguide, a portion of the image output from the waveguide is not visible to the user. In other words, a dark portion is present in the image output from the waveguide.

In order to solve this problem, it is possible to consider reducing the thickness of the waveguide, but the physical limitations of the waveguide must be considered.

Therefore, a separate optical system for enlarging the diameter of the light, for example, a beam expander, may be used so that the diameter of the light output from the projecting part is substantially equal to the thickness of the waveguide.

However, when the separate optical system is used in order to enlarge the diameter of the light incident on the waveguide as described above, there is a problem that the size of the wearable display apparatus becomes large, thus limiting its portability.

SUMMARY

One or more exemplary embodiments may overcome the above drawbacks and other problems associated with the conventional arrangement. One or more exemplary embodiments may provide an optical system including a waveguide capable of minimizing a dark portion of an output image regardless of a diameter of light incident on the waveguide, and a wearable display apparatus having the optical system.

In accordance with an aspect of an exemplary embodiment, an optical system may include a light source configured to output light; a first waveguide configured to guide light; a transmissive reflective layer provided on a top surface of the first waveguide and configured to reflect some light incident thereon and to transmit come light incident thereon; a second waveguide provided on a top surface of the transmissive reflective layer and configured to guide light; an in-coupler provided on the first waveguide and configured to guide light output by the light source into the first waveguide; and an out-coupler provided on one of the first waveguide and the second waveguide and configured to emit light incident thereon to an outside.

The optical system may include at least one additional waveguide and at least one additional transmissive reflective layer provided between the transmissive reflective layer and the second waveguide.

A size of the transmissive reflective layer may be different from a size of the at least one additional transmissive reflective layer.

The transmissive reflective layer may cover less than an entirety of an upper surface of the first waveguide.

The transmissive reflective layer may be provided at a position corresponding to a position of the in-coupler.

The transmissive reflective layer may cover an entirety of the upper surface of the first waveguide.

The in-coupler and the out-coupler may be both provided on the first waveguide.

The in-coupler may include an inclined surface formed at one end of the first waveguide.

The in-coupler may include a prism provided in the first waveguide.

The in-coupler and the out-coupler may include one of a diffractive optical element, a polarization selective coating, and a prism.

In accordance with an aspect of another exemplary embodiment, a method of guiding light in a waveguide including a first waveguide, a transmissive reflective layer, a second waveguide, an in-coupler, and an out-coupler, the method of guiding light may include transmitting light through the in-coupler, thereby causing the light to be incident on the transmissive reflective layer; directing some the light incident on the transmissive reflective layer to be incident on the first waveguide, directing some light incident on the transmissive reflective layer through the transmissive reflective layer to be incident on the second waveguide; causing light incident on the first waveguide to be totally internally reflected within the first waveguide and thereby incident on the transmissive reflective layer; causing light incident on the second waveguide to be totally internally reflected within the second waveguide and thereby incident on the transmissive reflective layer; and causing light traveling through the first waveguide and the second waveguide to be refracted by the out-coupler and thereby be emitted from the waveguide.

In accordance with an aspect of another exemplary embodiment, a wearable display apparatus may include a projecting part configured to output light forming an image; and an optical system configured to guide the light emitted from the projecting part, wherein the optical system may include a first waveguide configured to guide light; a transmissive reflective layer provided on a top surface of the first waveguide and configured to reflect some light incident thereon and to transmit some light incident thereon; a second waveguide provided on a top surface of the transmissive reflective layer and configured to guide light; an in-coupler provided on the first waveguide and configured to guide light emitted from the projecting part into the first waveguide; and an out-coupler provided on one of the first waveguide and the second waveguide and configured to emit light incident thereon.

The wearable display apparatus may include a head mounted display or a smart glasses.

Other objects, advantages and salient features of exemplary embodiments will become apparent from the following detailed description, taken in conjunction with the annexed drawings.

