Optical device for exit pupil expansion (EPE) and display apparatus including the optical device

A display apparatus comprising:

• an image generator configured to generate a virtual image;
• and
• an optical device for exit pupil expansion (EPE) configured to receive the virtual image and perform the EPE to combine the virtual image with an external real image,
• wherein the optical device comprises:
• an input part into which the virtual image is input;
• and
• an EPE part configured to receive the virtual image from the input part, perform one-dimensional (1D) EPE and two-dimensional (2D) EPE to combine the virtual image with the external real image, and output the combined image,
• wherein the EPE part comprises a 1D EPE area configured to perform the 1D EPE and a 2D EPE area configured to perform 2D EPE,
• wherein the 1D EPE area is formed in a line grating,
• wherein the line grating extends in a slope direction having a slope of 45° in a first direction, and has a first width and a first pitch in a direction perpendicular to the slope direction,
• wherein the virtual image from the input part is input into the 2D EPE area through the line grating of the 1D EPE area, and
• wherein a grating-free gap is between the 1D EPE area and the 2D EPE area, the grating-free gap having a constant width based on a surface of the 1D EPE area and a surface of the 2D EPE area being parallel to each other,
• wherein the 2D EPE area is formed in a rhombus grating,
• wherein the rhombus grating is arranged such that the virtual image output from the line grating in a second direction perpendicular to the first direction travels in both the second direction and at a first angle with respect to the second direction,
• wherein the rhombus grating has a shape in which a first line grating having a second angle in a clockwise direction with respect to the second direction and a second line grating having a second angle in a counterclockwise direction with respect to the second direction,
• wherein the second angle is less than 45°, and the first angle varies according to the second angle,
• wherein the first line grating has a second width and a second pitch in a direction perpendicular to a direction in which the first line grating extends, and
• wherein the second line grating has a third width and a third pitch in a direction perpendicular to a direction in which the second line grating extends.

A display apparatus comprising:

• an image generator configured to generate a virtual image;
• an optical device for exit pupil expansion (EPE) configured to receive the virtual image and perform the EPE to combine the virtual image with an external real image;
• and
• a body onto which the image generator and the optical device for EPE are mounted,
• wherein the optical device for EPE comprises:
• an input part into which the virtual image is input;
• and
• an EPE part configured to receive the virtual image from the input part, perform one-dimensional 1D EPE and two-dimensional (2D) EPE to combine the virtual image with the external real image, and output the combined image,
• wherein the EPE part comprises a 1D EPE area configured to perform the 1D EPE and a 2D EPE area configured to perform 2D EPE,
• wherein the 1D EPE area is formed in a line grating,
• wherein the line grating extends in a slope direction having a slope of 45° in a first direction, and has a first width and a first pitch in a direction perpendicular to the slope direction,
• wherein the virtual image from the input part is input into the 2D EPE area through the line grating of the 1D EPE area, and
• wherein a grating-free gap is between the 1D EPE area and the 2D EPE area, the grating-free gap having a constant width based on a surface of the 1D EPE area and a surface of the 2D EPE area being parallel to each other,
• wherein the 2D EPE area is formed in a rhombus grating,
• wherein the rhombus grating is arranged such that the virtual image output from the line grating in a second direction perpendicular to the first direction travels in both the second direction and at a first angle with respect to the second direction,
• wherein the rhombus grating has a shape in which a first line grating having a second angle in a clockwise direction with respect to the second direction and a second line grating having a second angle in a counterclockwise direction with respect to the second direction,
• wherein the second angle is less than 45°, and the first angle varies according to the second angle,
• wherein the first line grating has a second width and a second pitch in a direction perpendicular to a direction in which the first line grating extends, and
• wherein the second line grating has a third width and a third pitch in a direction perpendicular to a direction in which the second line grating extends.