Patent ID: 12235448

BEST MODE

The present invention will become apparent by reference to the following detailed description in conjunction with the accompanying drawings. However, the present invention is not limited to such embodiments and may be realized in various forms. The embodiments to be described below are nothing but the ones provided to bring the disclosure of the present invention to perfection and assist those skilled in the art to which the present invention pertains to completely understand the scope of the present invention. The present invention is defined only by the scope of the appended claims.

The terminology used herein is for the purpose of describing embodiments only and is not intended to limit the present invention.

In the present specification, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises” and/or “comprising” of stated component, step, operation and/or element, when used herein, do not exclude the presence or addition of one or more other components, steps, operations, and/or elements.

In the present specification, the terms such as first and second may be used to describe various components, but the components are not limited by the terms. The terms are used only to distinguish one component from another component.

An embodiment of the present invention provides a head mounted display, which is worn on a head of a wearer to transfer an image, the head mounted display including: a display source disposed on a lateral side of an eye of the wearer and configured to output image display light; a first lens configured to condense the image display light; a holographic optical element (HOE) disposed in front of the eye of the wearer and configured to direct the image display light passing through the first lens toward the eye of the wearer; and a controller configured to adjust the position of at least one of the display source and the first lens.

The head mounted display according to an embodiment of the present invention can use the holographic optical element and the lens and adjust the positions of the holographic optical element and the lens, thereby securing an eye motion box having a certain level and extend a field of view in which an implemented image can be visually recognized.

FIG.1is a schematic view of a head mounted display100according to an embodiment of the present invention.

According to an embodiment of the present invention, the head mounted display100includes a display source110, a first lens120, a holographic optical element130, and a controller160. Referring toFIG.1, the head mounted display100may be mounted on the head of a wearer, image display light including image information may be output by the display source110located on the lateral side of an eye10of the wearer, and the output image display light may be directed toward the eye of the wearer by the first lens120and the holographic optical element130. The head mounted display100may form a virtual image of the image display light including the image information through the display source110, the first lens120, the holographic optical element130, and the wearer may recognize the virtual image as if the wearer sees an image through a screen at a certain distance. In addition, the controller160may adjust the position of at least one of the display source and the first lens120in order to extend the field of view of the wearer.

According to an embodiment of the present invention, the controller160may adjust the position of at least one of the display source110and the first lens120. As described above, the controller160adjusts the position of at least one of the display source110and the first lens120to adjust a distance L1(FIG.4) between the holographic optical element130and the first lens120and/or a distance L2(FIG.4) between the first lens120and the display source110, so that it is possible to maximally secure a field of view on the basis of body information that varies depending on a wearer.

According to an embodiment of the present invention, the controller160may include: a sensor unit disposed in front of the eye of the wearer and configured to acquire body information of the wearer; a control unit163configured to calculate predetermined positions of the first lens and the display source on the basis of the acquired body information; and an operation unit165disposed on the lateral side of the eye of the wearer and configured to move the positions of the first lens and the display source to the predetermined positions. As described above, by adjusting the distance L1between the holographic optical element130and the first lens120and/or the distance L2between the first lens120and the display source110, it is possible to maximally secure the field of view on the basis of body information that varies depending on a wearer.

According to an embodiment of the present invention, the sensor unit161may be disposed in front of the eye of the wearer and acquire the body information of the wearer. As described above, since the sensor unit161is disposed in the front of the eye of the wearer, it is possible to accurately and easily measure the body information of the wearer, and by acquiring the body information, it is possible to adjust the first lens and the display source according to body conditions depending on the wearer.

According to an embodiment of the present invention, the control unit163may calculate the predetermined position of the first lens and/or the display source on the basis of the acquired body information. Specifically, when the calculated result obtained by analyzing the body information acquired by the sensor unit161indicates that the field of view of the wearer is to be narrowed or widened, the control unit163may adjust the positions of the first lens and the display source to maximally secure the field of view of the wearer.

According to an embodiment of the present invention, the operation unit165may be disposed on the lateral side of the eye of the wearer and may move the position of the first lens and/or the display source to the predetermined position. Specifically, when the control unit163determines the position according to the body information of the wearer, the operation unit165may move the position of the first lens and/or the display source to adjust the distance L1between the holographic optical element130and the first lens120and/or the distance L2between the first lens120and the display source110, thereby maximally securing the field of view according to the wearer.

According to an embodiment of the present invention, the display source110may receive an electrical signal having image information and output image display light for the image information. The display source110may be a small display panel capable of displaying an image. For example, the display source110may include a liquid crystal display (LCD) panel or a display panel composed of organic light emitting diodes (OLEDs).

According to an embodiment of the present invention, the first lens120serves to condense the image display light emitted from the display source110. The display source110and the first lens120may be arranged such that the image display light emitted from the display source110is directly directed toward the first lens120.

According to an embodiment of the present invention, the holographic optical element130may direct the image display light passing through the first lens120toward the eye10of the wearer of the head mounted display100. That is, the image display light passing through the first lens120may be incident at a predetermined angle with respect to the normal line of the holographic optical element130, reflected at an angle other than a reflection angle having the same angle, and directed toward the eye of the wearer. The holographic optical element130may be a reflective holographic optical element130designed to diffract image display light incident at a certain angle in a direction designed in advance, that is, a direction in which the eye of the wearer is located.

In an embodiment of the present invention, the head mounted display100may be implemented in the form of eyeglasses. The head mounted display100according to an embodiment may further include an eyeglass lens disposed in front of the eye of the wearer, that is, a second lens150. In such a case, the display source110and the first lens120may be formed inside the eyeglass temple (not illustrated) so that the display source110and the first lens120are disposed on the lateral side of the eye10of the wearer, and one surface of the second lens150may be coated with the holographic optical element130in the form of a film. The holographic optical element130may be formed on one surface of the second lens150on the eye side of the wearer, or may be formed on the other surface of the second lens150onto which light emitted from the outside is incident. In the illustrated embodiment, the eyeglass lens, that is, the second lens has a flat shape; however, the present invention is not limited thereto and the second lens may have a curved shape or a pair of left and right second lenses (eyeglass lenses) may be formed to have optical axes, which are not parallel with each other, according to the shape of an eyeglass frame.

In the head mounted display100according to an embodiment of the present invention, the display source110and the first lens120may be formed inside the eyeglass temple (not illustrated) so that the display source110and the first lens120are disposed on the lateral side of the eye10of the wearer, and the holographic optical element130may be formed on one surface of the second lens150. In such a case, image display light emitted from the display source110may be condensed while passing through the first lens120, and the image display light passing through the first lens120may be obliquely incident onto the holographic optical element130at a predetermined angle and then diffracted and incident onto the eye10of the wearer. Accordingly, the head mounted display100in the form of eyeglasses according to an embodiment of the present invention may transfer an image including certain information to the eye10of the wearer.

In the head mounted display100according to an embodiment of the present invention, the holographic optical element130is formed on the second lens150. Therefore, the head mounted display100may be configured to allow external light, which is incident from the other surface of the second lens150and passes through the second lens150and/or the holographic optical element130, and image display light, which is emitted from the display source110formed on the eyeglass temple and is diffracted by the holographic optical element130, to be simultaneously incident onto the eye10of the wearer.

The head mounted display100according to an embodiment of the present invention may have a bilaterally symmetrical structure in order to transfer image information to both eyes of the wearer. The illustrated embodiment is configured to transfer the image display light to the right eye of the wearer; however, the present invention is not limited thereto and the head mounted display100may further include the display source, the first lens, the holographic optical element, and the controller, which are provided on the left eyeglass temple and the left eyeglass lens (second lens) so as to transfer the image display light to the left eye of the wearer. Furthermore, the head mounted display100may also be implemented in the form of goggles or a helmet as well as eyeglasses.

FIG.2is a view for explaining a field of view implemented by the head mounted display according to an embodiment of the present invention. According to an embodiment of the present invention, the display source110may be a small rectangular display panel and emit image display light including image information from each point of the rectangle. Referring toFIG.2, the image display light emitted from the display source110may form an intermediate image111for an image while passing through the first lens120. Light emitted from the intermediate image111for an image may be diffracted by the holographic optical element130and directed toward the eye10of the wearer, thereby forming a virtual image112for the intermediate image. The virtual image112formed by the holographic optical element130and the first lens120displays the image information included in the image display light emitted from the display source110to the wearer who wears the head mounted display100.

At this time, the field of view (FOV) may be represented by expressing, as an angle, the size of an area, where the virtual image formed by the image display light emitted from each point of the display source110can be observed at a time by the eyes of the wearer, and the like.

According to an embodiment of the present invention, the first lens120is disposed on an optical path of the image display light between the display source110and the holographic optical element130and forms the intermediate image111of the image display light. Therefore, such a configuration may provide the effect that looks as if the display source110emits the image display light at a position where the intermediate image111is formed, and may extend the field of view for a virtual image finally formed by the holographic optical element. More specifically, according to various embodiments, when the first lens is inserted and disposed between the display source110and the holographic optical element130, the field of view may be extended three times or more compared to a comparative example with no first lens.

FIG.3is a view for explaining an eye motion box implemented by the head mounted display according to an embodiment of the present invention. Specifically,FIG.3illustrates, using shades, optical paths, through which image display lights emitted from both ends and the center of the display source110are incident onto the eye of the wearer, and ranges in which the image display lights incident onto the eye from the respective optical paths can be incident. Referring toFIG.3, the image display light emitted from the center of the display source110may be incident onto the eye of the wearer within an incident range (illustrated in shades) parallel with the visual axis of the eye of the wearer, and the image display light emitted from both ends of the display source110may be incident within a predetermined incident range (illustrated in shades) parallel with a direction inclined left and right at a certain angle (for example, a half of the field of view) with respect to the visual axis of the eye of the wearer. In such a case, a portion where the incident ranges of the image display lights emitted from both ends and the center of the display source110overlap each other may be referred to as an eye motion box (EMB).

In the present specification, the eye motion box (EMB) may be defined as an area where an implemented image can be visually recognized. That is, only when the eye of the wearer may be disposed within the eye motion box formed by the optical system constituting the head mounted display, the wearer can correctly recognize an image to be transferred through the head mounted display. Accordingly, only when an eye motion box having a certain level or more is secured, a visual axis, which may vary depending on a distance between the head and eyes of the wearer, may be formed in the eye motion box, and only when the visual axis of the wearer is formed in the eye motion box, it is possible to implement an image to be transferred through the head mounted display.

In the head mounted display100according to an embodiment of the present invention, the first lens120is disposed between the display source110and the holographic optical element130. Therefore, the size of the eye motion box is somewhat reduced compared to when only the first lens is not provided. However, the head mounted display100can secure an eye motion box having a certain level (for example, 10 mm×10 mm) or more for providing an image and extend the field of view.

MODE FOR INVENTION

FIG.4is a view for explaining a physical structure of an optical system included in head mounted displays according to various embodiments.FIG.4illustrates that the holographic optical element130is replaced with one virtual lens131such that an optical path bent due to an optical action (for example, diffraction) of the holographic optical element130in any one ofFIG.1to FIG. is unfolded and is arranged on the same line as a straight line formed by the display source, the first lens, and the eye or visual axis of the wearer. In the illustrated structure in which the holographic optical element130is replaced with one virtual lens131, it is possible to derive appropriate focal lengths the first lens120and the holographic optical element130according to the size of the display source110and optical characteristics to be recorded on the first lens120and the holographic optical element130.

Referring to (a) and (b) ofFIG.4, assuming that the off-axis reflective structure of the holographic optical element130inFIG.1toFIG.3is unfolded and the display source110, the first lens120, and the eye10of the wearer are located on the same straight line, it is possible to derive a focal length FL2of the first lens120and optical characteristics (for example, a focal length FL1of the holographic optical element or a half R1of the size of the holographic optical element) to be recorded on the holographic optical element130.

In an embodiment of the present invention, assuming that the display source110is a rectangular display panel having a width of about 10 mm and a height of about 7 mm, the field of view (FOV) is derived by Formula 1 below.
FOV=2×tan−1R1/ERFormula 1

In Formula 1 above, FOV denotes a field of view at which a virtual image of an image can be seen at a time through the eye of a wearer, ER denotes a linear distance between the eye10and the holographic optical element130, and R1denotes a half of the size of the holographic optical element130. R1can be obtained through Formula 1 above, and twice R1is a minimum size of the holographic optical element to be recorded in order to implement the FOV.
R1=ER×tan FOV/2  Formula 2

Through Formula 2 above, it is possible to derive the minimum size (twice R1) of the holographic optical element to be recorded, through ER, which is the distance between the holographic optical element130and the eye10, and a target field of view (FOV).

Through the light illustrated in (a) ofFIG.4, Formula 3 below may be obtained.
L1/2R1=(PD−L1)/PSFormula 3

In Formula 3 above, L1denotes a distance between the first lens120and the virtual lens131, L2denotes a distance between the first lens120and the display source110, PD denotes a distance (L1+L2) between the virtual lens131and the display source110, and PS denotes a horizontal distance of the display source110.

Through Formula 3 above, the distance between the first lens120and the virtual lens131may be derived as L1=PD/{(1+PS)/2·R1}, and the distance between the first lens120and the display source110may be derived as L2=PD−L1.

Furthermore, when FL1denotes the focal length of the virtual lens131and FL2denotes the focal length of the first lens120, Formulas 4 and 5 below may be obtained by putting them into the lens formula.
1/FL1=1/L1+1/ERFormula 4
1/FL2=1/L1+1/L2  Formula 5

Through Formulas 4 and 5 above, the focal length FL1to be recorded on the holographic optical element130and the focal length FL2of the first lens120, which is additionally disposed between the display source110and the holographic optical element130in order to extend the field of view, may be derived by Formulas 6 and 7 below.
FL1=ER×L1/ER+L1  Formula 6
FL2=(L1−FL1)ER×L2/(PD−FL1)  Formula 7

In an embodiment of the present invention, referring to Table 1 below, under the condition that the linear distance ER between the eye10of the wearer and the holographic optical element130is set to 21.0 mm, the distance PD (L1+L2) between the virtual lens131and the display source110is set to 60.0 mm, the horizontal distance PS of the display source110is set to 10.0 mm, and the field of view (FOV) is set to 35.0°, the half R1of the minimum size of the holographic optical element, the distance L1between the first lens120and the virtual lens131, the distance L2between the first lens120and the display source110, the focal length FL1to be recorded on the holographic optical element130, and the focal length FL2of the first lens120, which is additionally disposed between the display source110and the holographic optical element130in order to extend the field of view, may be derived as shown in Table 1 below through Formulas 1 to 5 above. The components set to have the derived five values may be included in a head mounted display to display an image.

That is, it is possible to implement a head mounted display in which the focal length to be recorded on the holographic optical element130is about 13 mm, the focal length of the first lens120is about 11 mm, the distance L1between the first lens120and the holographic optical element130is about 35 mm, and the distance L2between the first lens120and the display source110is about 25 mm.

TABLE 1ERFDPSFOVR1L1L2FL1FL2(mm)(mm)(mm)(°)(mm)(mm)(mm)(mm)(mm)21.060.010.035.06.6234.1925.8113.0111.63

Referring toFIG.1, the head mounted display100according to an embodiment of the present invention may be implemented in the form of eyeglasses, the display source110and the first lens120may be formed inside the eyeglass temple (not illustrated) so that the display source110and the first lens120are disposed on the lateral side of the eye10of the wearer, and one surface of the eyeglass lens (second lens)150, which is disposed in front of the eye10of the wearer, may be coated with the holographic optical element130in the form of a film. The image display light from the display source110may be incident at an angle of θ with respect to the normal line of the holographic optical element130or the visual axis of the eye of the wearer, may be diffracted by the holographic optical element130, and may be incident onto the eye of the wearer in parallel with the normal line of the holographic optical element130or the visual axis of the eye of the wearer. For example, in the structure in which the display source110, the first lens120, the holographic optical element130are included in eyeglasses, θ may be about 50°. Furthermore, the lens120may have a focal length of about 10 mm and an aperture of about 10 mm. Furthermore, the holographic optical element130may have a size of about 20 mm to about 40 mm that may be formed on the second lens.FIG.5is an exemplary view for explaining the manufacturing of the holographic optical element included in the head mounted display according to an embodiment of the present invention.FIG.6is another exemplary view for explaining the manufacturing of the holographic optical element included in the head mounted display according to an embodiment of the present invention.

According to an embodiment of the present invention, the holographic optical element130may be manufactured to have diffraction efficiency in which light incident at a predetermined angle with respect to the normal line of the holographic optical element is reflected at another angle other than the reflection angle having the same angle. Specifically, the holographic optical element may be manufactured to have diffraction efficiency in which light incident at 50° with respect to the normal line is reflected at 0° with respect to the normal line.

According to an embodiment of the present invention, the holographic optical element130may be manufactured to have a minimum size derived through the above Formulas described with reference toFIG.4.

According to an embodiment of the present invention, the holographic optical element130may be manufactured such that the focal length FL1derived through the above Formula described with reference toFIG.4is recorded thereon.

According to an embodiment of the present invention, the sensor unit161may be provided outside the controller. Specifically, the sensor unit161may be located on an eyeglass frame other than an eyeglass temple. As described above, the sensor unit161is provided outside the controller, so that it is possible to simplify the structure of the head mounted display and accurately acquire the body information of the wearer.

According to an embodiment of the present invention, the sensor unit161may be provided inside the eyeglass frame. Specifically, the sensor unit161may be located inside the eyeglass frame disposed in front of the eye of the wearer and located toward the eye of the wearer. As described above, the sensor unit161is provided toward the eye of the wearer inside the eyeglass frame located in front of the eye of the wearer, so that it is possible to accurately measure and/or acquire the body information of the wearer.

According to an embodiment of the present invention, the control unit163and/or the operation unit165may be located inside the eyeglass temple. As described above, the control unit163and/or the operation unit165are/is provided inside the eyeglass temple corresponding to the lateral side of the eye of the wearer, so that it is possible to simplify the structure of the head mounted display and reduce the weight of the head mounted display.

According to an embodiment of the present invention, the body information may be one selected from the group consisting of the shape of the head of the wearer, the position of the eye of the wearer, a distance between both eyes of the wearer, and a combination thereof. Specifically, the body information acquired by the sensor unit161may be one selected from the group consisting of the shape of the head of the wearer, the position of the eye of the wearer, a distance between both eyes of the wearer, and a combination thereof, and may all be acquired when they correspond to information required to extend the field of view of the wearer. More specifically, the body information may include the size of the pupil of the wearer, a state in which the diaphragm of the wearer has been closed, a depth at which the eyeball has been depressed at a skeleton around the eye of the wearer, and the like. By adjusting the distance L1between the holographic optical element130and the first lens120and/or the distance L2between the first lens120and the display source110according to the body information, it is possible to maximally secure the field of view on the basis of the body information that varies depending on a wearer.

According to an embodiment of the present invention, the control unit163may calculate predetermined positions of the first lens and the display source so as to satisfy a target field of view of the eye of the wearer for the image. Specifically, the control unit163may calculate the predetermined positions of the first lens and the display source on the basis of the acquired body information of the wearer and the operation unit165may adjust the positions of the first lens and the display source, so that it is possible to maximally secure the field of view, on the basis of the body information that varies depending on a wearer, by adjusting the distance L1between the holographic optical element130and the first lens120and/or the distance L2between the first lens120and the display source110.

Referring toFIG.5andFIG.6, the holographic optical element130according to various embodiments may be manufactured by disposing a photosensitive material140on a transparent substrate133(for example, glass, plastic, or eyeglass lens) and recording an interference pattern on the photosensitive material by using two coherent laser beams emitted to the front and rear surfaces of the photosensitive material at a predetermined angle. As illustrated inFIG.5andFIG.6, the interference pattern may be formed in an area where the silhouette (indicated in shades) of a first laser beam and the silhouette (indicated in shades) of a second laser beam overlap each other on the photosensitive material, and the size of the holographic optical element may be determined by the overlapping area. Furthermore, when the first lens120is added as described above with reference toFIG.4, the focal length FL1to be recorded on the holographic optical element130is calculated and a vertical distance between a point where the first laser beam starts to spread and the photosensitive material140is set as the calculated focal length FL1, so that the focal length FL1may be recorded on the holographic optical element.

Referring toFIG.5, in order to manufacture a holographic optical element having a focal length calculated when the first lens120is added, a first laser emits a cone-shaped beam that starts to spread at a point spaced apart from one surface of the photosensitive material140by the focal length in a vertical direction. At this time, a second laser emits a cylindrical beam toward the other surface of the photosensitive material140. An area of the photosensitive material140, where the interference pattern is formed by the interaction of the first laser beam and the second laser beam, may be the holographic optical element, and determines the size of the holographic optical element. In such a case, the thickness and the exposure time of the photosensitive material140are recorded differently, so that a holographic optical element having maximum diffraction efficiency may be manufactured.

Referring toFIG.6, in order to manufacture a holographic optical element having a short focal length due to a short focal length calculated when the first lens120is added, it is possible to use a method in which the first laser emits a cone-shaped beam that starts to spread at a point spaced apart from one surface of the photosensitive material140by the focal length in a vertical direction, and the second laser emits a cone-shaped beam, which travels while being condensed, toward the other surface of the photosensitive material140. An area of the photosensitive material140, where the interference pattern is formed by the interaction of the first laser beam and the second laser beam, may be the holographic optical element, and determines the size of the holographic optical element. In such a case, the thickness and the exposure time of the photosensitive material140are recorded differently, so that a holographic optical element having maximum diffraction efficiency may be manufactured.

Although the present invention has been described in relation to the preferred embodiment described above, various corrections or modifications can be made without departing from the subject matter and scope of the disclosure. Therefore, the appended claims will include such corrections or modifications as long as they belong to the subject matter of the present invention.