CROSS-REFERENCE TO RELATED APPLICATION

Pursuant to 35 U.S.C. § 119(a), this application claims the benefit of the earlier filing date and the right of priority to Korean Patent Application No. 10-2021-0005319, filed on Jan. 14, 2021, the entirety of which is incorporated by reference herein.

BACKGROUND

1. Technical Field

The present disclosure relates to a glasses-type device, and more particularly, to a glasses-type device capable of providing virtual reality (VR), augmented reality (AR), and mixed reality (MR) images.

2. Description of the Related Art

As the information age is developing rapidly, an importance of a display device that implements a realistic screen is being emphasized, and a wearable glasses-type device, such as a head mounted display (HMD) or smart glasses, is one example of the display device.

A head mounted display is mainly implemented as a safety glasses or a helmet-type device configured to view a screen in front of the eyes, and is developed to realize a sense of virtual reality. In addition, a wearable glasses-type device generally uses a method for projecting an image on a small display, such as a liquid crystal installed at a position close to both eyes. And, by an optical system using refraction of light, a focus can be formed to display image light generated from a micro-display element as a virtual image on a glass of the glasses-type device.

Since such a glasses-type device implements a screen in a see-through form through a virtual image formed on the glass, the glasses-type device can display not only virtual reality (VR) but also augmented reality (AR) or mixed reality (MR) images.

Meanwhile, a display optical system of atypical glasses-type device uses light having an extremely short wavelength, such as laser, as an image source to implement a virtual image, and has a configuration to reflect a laser image on a glass of the glasses-type device by using a micro electro mechanical system (MEMS) mirror scanner. Here, a problem of diffraction aberration due to off-axis does not occur, but since laser light is reflected on human eyes, an eye-safety problem, in which vulnerable human tissues such as eyes can be damaged, is emerging. In addition, as the MEMS mirror scanner is used, the optical system has a complicated structure and a size of the optical system is increased, and thus, it is difficult to make the glasses-type device compact.

Meanwhile, in order for a user to view a virtual image formed in the glasses-type device, the virtual image should be formed on an area corresponding to a user's eye movement. As such, a user can view an entire virtual image when the virtual image is formed within an area where the user can view the entire virtual image while moving his or her eyes, that is, an eye movement box (EMB).

However, there is a big difference in a horizontal distance between centers of pupils of both eyes (or interpupillary distance, hereinafter IPD) by individuals or race, sex or age. For example, a child and an adult have large differences in their head sizes, and such differences causes a big difference in IPD. In addition, due to a characteristic of the glasses-type device in which a body portion provided with an optical system is formed in a leg portion that is connected to a glass, such a difference in IPD changes an incident angle of light incident on the glass so that a position of a virtual image formed on the glass is changed. In addition, when the virtual image display position is changed due to the difference in IPD, it may cause a problem in which a user is disturbed from viewing a part of the virtual image.

For example, when a virtual image is formed at a point other than a center of the EMB due to the difference in IPD, a part of the virtual image can be formed outside of the EMB. In this situation, it is difficult for the user to view the part of the virtual image formed outside of the EMB, and accordingly, the user cannot view the entire virtual image.

SUMMARY

An aspect of the present disclosure is to obviate the above-mentioned problem and other drawbacks, namely, to provide a wearable glasses-type device capable of generating a virtual image without directly reflecting laser light into a user's eyes.

Another aspect of the present disclosure is to provide a glasses-type device having a more compact size by generating a virtual image by reflecting an image generated from an image source on a glass without a micro electro mechanical system (MEMS) mirror scanner.

In addition, still another aspect of the present disclosure is to provide a glasses-type device capable of solving a problem, in which a user cannot view a part of a virtual image due to a difference in interpupillary distance (IPD), by allowing the virtual image to be formed in an eye movement box (EMB) regardless of the difference in IPD.

To achieve these and other advantages and in accordance with the purpose of this specification, as embodied and broadly described herein, there is provided a glasses-type device, including a display unit to emit image light serving as an image source of a virtual image; a diffraction element that reflects and diffracts the image light at a predetermined angle; and a first holographic optical element (HOE) provided on at least a portion of a glass of the glasses-type device, and configured to cancel dispersion of the image light that is reflected and diffracted by the diffraction element, and reflect the light in which dispersion is canceled to display a virtual image corresponding to the image light.

To achieve these and other advantages and in accordance with the purpose of this specification, as embodied and broadly described herein, there is provided a glasses-type device, including a display unit to emit image light serving as an image source of a virtual image, a diffraction element that reflects and diffracts the image light at a predetermined angle, and a first holographic optical element (HOE) provided on at least a portion of a glass of the glasses-type device, and configured to negatively disperse positively dispersed light that is diffracted by the diffraction element to cancel the positive dispersion of the light and reflect the light in which dispersion is canceled to display a virtual image corresponding to the image light.

In one embodiment, the diffraction element includes a second holographic optical element that transmits light when the light is incident at an angle within a predetermined incident angle range, and reflects light when the light is incident at an angle within a predetermined reflection angle range, and a first reflection element arranged such that a reflective surface of the first reflection element faces the second holographic optical element at a predetermined angle.

In one embodiment, the display unit is disposed to face the second holographic optical element at an angle within the incident angle range, so that image light incident on the second holographic optical element transmits through the second holographic optical element, and the first reflection element is configured such that a second surface different from a first surface of the second holographic optical element to which the image light is incident is disposed to face the reflective surface at an angle within the predetermined reflection angle range, so that light transmitted through the second holographic optical element is reflected on the second surface of the second holographic optical element at an angle within the reflection angle range.

In one embodiment, the reflective surface of the first reflection element and the second surface of the second holographic optical element are disposed to face each other, so that a first light path in which light transmitted through the second holographic optical element is led to the reflective surface of the first reflection element and a light path in which light reflected from the reflective surface of the first reflection element is led to the second surface of the second holographic optical element overlap each other.

In one embodiment, the first reflection element is a full reflection mirror reflecting all incident light of all wavelengths.

In one embodiment, the first reflection element is a half reflection mirror in which reflection of light is partially limited so that a transmission ratio and a reflection ratio of incident light having an unspecified wavelength have a predetermined ratio within a predetermined range.

In one embodiment, the display unit includes an optical module including at least one light source that emits image light, and a lens unit including at least one lens for magnifying the light emitted from the at least one light source and converting the light into parallel light.

In one embodiment, the at least one light source is a self-luminous light source or an illumination type light source including at least one of a micro light emitting diode (LED), a micro organic LED (OLED), a liquid crystal on silicon (LCoS), or a digital micromirror device (DMD) with LED or SLD.

In one embodiment, the first reflection element is a holographic optical element arranged such that the light transmitted through the second holographic optical element is incident at an angle within the predetermined reflection angle range.

In one embodiment, the glasses-type device further includes a tilting portion configured to rotate the first reflection element by a predetermined angle to change an angle at which the reflective surface faces the second holographic optical element.

In one embodiment, a position of the virtual image formed on a glass is moved in a direction towards a glabella of a user when the first reflection element is rotated to increase an incident angle of light incident on the second surface of the second holographic optical element, and is moved in a direction towards a temple of the user when the first reflection element is rotated to decrease the incident angle of light incident on the second surface of the second holographic optical element.

In one embodiment, the tilting portion further includes an actuator to provide a rotational force for rotating the first reflection element by a predetermined angle, and the glasses-type device further includes a sensor unit to measure a distance between centers of pupils of both eyes, and a controller to determine a rotation angle of the first reflection element at an angle corresponding to the distance measured by the sensor unit to control the actuator to rotate the first reflection element according to the determined rotation angle.

In one embodiment, the sensor unit is at least one camera provided in a glass frame supporting glasses corresponding to both eyes of a user, and the controller calculates a distance between centers of pupils of both eyes based on positions of the pupils of both eyes of the user obtained by the camera.

In one embodiment, the sensor unit includes at least one sensor to measure an angle between a body portion of the glasses-type device provided with the display unit and a glass frame supporting glasses corresponding to both eyes of a user, and the controller estimates a distance between centers of pupils of the both eyes based on the measured angle between the body portion and the glass frame.

In one embodiment, the glasses-type device further includes a tilting portion to rotate the display unit by a predetermined angle to change an angle at which the display unit faces the diffraction element.

In one embodiment, a position of the virtual image formed on a glass is moved in a direction towards a glabella of a user when an angle at which the display unit faces the diffraction element is changed to increase incident angle of light incident on the diffraction element, and is moved in a direction towards a temple of the user when the angle at which the display unit faces the diffraction element is changed to decrease incident angle of light incident on the diffraction element.

To achieve these and other advantages and in accordance with the purpose of this specification, as embodied and broadly described herein, there is provided a method for providing a virtual image of a glasses-type device, the method including steps of emitting image light serving as an image source of the virtual image from at least one light source, magnifying and converting the image light emitted from the light source into parallel light by at least one lens, reflecting and diffracting the image light at a predetermined angle by a diffraction element, and negatively dispersing positively dispersed light that is diffracted by the diffraction element, so as to cancel the positive dispersion of the light by a first holographic optical element provided on at least a portion of a glass of the glasses-type device, and reflecting the light in which dispersion is canceled to display the virtual image corresponding to the image light on the at least a portion of the glass.

In one embodiment, the diffraction element includes a second holographic optical element that transmits light when the light is incident at an angle within a predetermined incident angle range, and reflects light when the light is incident at an angle within a predetermined reflection angle range, and a first reflection element arranged such that a reflective surface of the first reflection element faces the second holographic optical element at a predetermined angle.

In one embodiment, the step of reflecting and diffracting the image light by the diffraction element includes steps of transmitting the parallel light incident at an angle within the incident angle range through the second holographic optical element, reflecting the light transmitted through the second holographic optical element on the first reflection element at an angle within the reflection angle range, and reflecting the light reflected from the first reflection element towards the first holographic optical element by the second holographic optical element, and wherein the reflected light is reflected and diffracted by the second holographic optical element so as to be positively dispersed.

In one embodiment, the step of reflecting and diffracting the image light by the diffraction element further includes rotating a direction in which the at least one light source or the diffraction element is facing by a predetermined angle, and wherein a position of the virtual image formed on the glass is changed as the direction in which the at least one light source or the diffraction element is facing is changed.

Hereinafter, effects of a glasses-type device and a method for providing virtual images of the glasses-type device according to the present disclosure will be described.

According to at least one of embodiments of the present disclosure, the present disclosure can generate a virtual image by using a light source having a longer wavelength than that of a typical laser light source and cancel negative dispersion phenomenon caused by long wavelength light by using a holographic element to thereby generate a virtual image on a glass without having to use a short wavelength laser light. Accordingly, the present disclosure has an effect of solving an eye-safety problem due to a short wavelength laser light and an effect of providing a more compact glasses-type device by reducing a size of an optical system, as a micro electro mechanical system (MEMS) mirror scanner to reflect short wavelength laser light is not provided.

In addition, according to at least one of the embodiments of the present disclosure, the present disclosure has an effect of allowing a user to view an entire virtual image regardless of differences in IPD by adjusting a reflection angle of a mirror that reflects light transmitted through a holographic element so that a virtual image formed on a glass is always formed within an eye movement box (EMB).

