Wearable glasses-type device and method for providing virtual images of the glasses-type device

A method of controlling a glasses-type device to provide a virtual image, the method comprising:

• emitting, by at least one light source, image light serving as an image source of the virtual image;
• magnifying and converting the image light emitted from the light source into parallel light by at least one lens;
• reflecting and diffracting the parallel light at a predetermined angle by a diffraction element to generate positively dispersed light;
• and
• negatively dispersing the positively dispersed light by a first holographic optical element disposed on at least a portion of glass of the glasses-type device to generate light in which dispersion is canceled, and reflecting the light in which dispersion is canceled to an eye of a user for displaying the virtual image corresponding to the image light,
• wherein the reflecting and the diffracting include:
• transmitting the parallel light incident at an angle within an predetermined incident angle range through a second holographic optical element and onto a reflective surface of a first reflection element;
• reflecting the parallel light off of the first reflection element to output first reflected light at an angle within a predetermined reflection angle range, the first reflected light being based on the parallel light transmitted through the second holographic optical element;
• and
• reflecting, by the second holographic optical element, the first reflected light output from the first reflection element to output second reflected light towards the first holographic optical element,
• wherein the second reflected light is reflected and diffracted by the second holographic optical element to be positively dispersed.