Optical device for augmented reality having ghost image prevention function

An optical device for augmented reality having a ghost image prevention function, the optical device comprising:

• an image output unit configured to output virtual image light;
• an optical means configured such that the virtual image light output from the image output unit propagates through an inside thereof and real object image light is transmitted therethrough toward a pupil of an eye of a user;
• a first optical element disposed inside the optical means, and configured to transfer the virtual image light, output and transferred from the image output unit, to a plurality of second optical elements;
• and
• the plurality of second optical elements disposed inside the optical means, and configured to provide a virtual image to the user by transferring the virtual image light, transferred from the first optical element, toward the pupil of the eye of the user;
• wherein the optical means has a first surface through which the virtual image light and the real object image light are output toward the pupil of the user, a second surface which is opposite to the first surface and on which the real object image light is incident, and a third surface on which the virtual image light output from the image output unit is incident;
• wherein the third surface is formed to have an inclination angle θin with respect to a normal line in a forward direction from the pupil;
• wherein the third surface is disposed to face a surface of the image output unit;
• and
• wherein the image output unit is spaced apart from the third surface so that a distance Lg between the image output unit and the third surface satisfies the following equation:
• L
• g
• ≥
• L
• d
• 2
• ⁢
• 1
• -
• n
• 2
• ⁢
• sin
• 2
• ⁢
• θ
• i
• ⁢
• n
• n
• 2
• ⁢
• sin
• 2
• ⁢
• θ
• i
• ⁢
• n
• where Ld is a length of the image output unit, θin is an inclination angle between the third surface of the optical means and the normal line in the forward direction from the pupil, and n is a refractive index of the optical means.