KR101455714B1 - Head mounted display device and method for compensating image distortion thereof - Google Patents

Abstract

A head mounted display device comprises: a display unit for displaying an image; a main lens unit for refracting in the direction of eyes of a user by enlarging the image to be displayed on the display unit; and a correction lens formed between the display unit and the main lens unit to correct the distortion of the image. Therefore, it is possible to reduce the size and weight of the HMD device and simultaneously to provide good quality image to the user by correcting the distortion of the image.

Description

TECHNICAL FIELD [0001] The present invention relates to a head-mounted display device and a method for correcting image distortion of the head-

The present invention relates to a head-mounted display apparatus and an image distortion correction method thereof, and more particularly, to a head-mounted display apparatus and an image distortion correction method for reducing image distortion due to spherical aberration of a lens.

HMD (Head Mounted Display) is rapidly emerging as a visualization device that provides virtual reality and augmented reality. Conventional HMDs have been used for military and training purposes. However, as the display technology has recently become smaller and lighter, low-priced HMDs are being commercialized. Although these low cost HMDs have been mainly used for 3D movie appreciation and the like, they have been actively researched and developed as visualization devices of virtual reality and augmented reality by doubling the technical characteristics that can provide a high degree of immersion.

The key to miniaturization and lightweighting of HMDs is how small and light can integrate internal components. Recently, with the development of small display technology with high resolution, the LCD used in the HMD has been considerably reduced in size, but the structure of the optical system is still complicated and bulky. For this reason, the wide viewing angle HMDs that provide a high degree of immersion among the HMDs to date are bulky. In order to innovatively reduce this volume, it is necessary to simplify the optical structure.

The conventional optical structure is divided into pupil forming method and no pupil forming method. The image forming system is a system in which an image is put in the optical system in the HMD and the image is put into the naked eye. At this time, the size of the image is determined by the size of the exit pupil.

On the other hand, the non-resolution method is a method in which only a convex lens having a simple structure is transmitted through the virtual image to the naked eye, and an image is formed on the retina by the refraction of the lens. This method can realize a wide viewing angle with a relatively simple structure. However, this method relies on the optics of a single lens, so the quality of the image is degraded and the image deteriorates depending on the position of the naked eye. Especially, the distortion due to the spherical aberration becomes worse as it goes closer to the outer periphery of the lens, so that the image looks distorted. In severe cases, chromatic aberration is accompanied by the degradation of image quality, which is difficult to use as an HMD.

To solve this problem, a lens with a small aberration of appropriate magnification should be used. However, even with proper lenses, the distance from the lens to the display can not be reduced, resulting in a bulky HMD. When a high magnification lens is used to reduce the distance, there is a problem that a vicious circle in which the distortion of the aberration is further increased is repeated.

Accordingly, there is a demand for an image distortion correction method capable of reducing aberration distortion while sufficiently realizing a small HMD device by sufficiently reducing the lens distance.

KR 2013-0008902 A

Accordingly, it is an object of the present invention to provide a head-mounted display device which reduces image distortion due to spherical aberration of a lens while reducing the volume of the apparatus.

Another object of the present invention is to provide a method for correcting image distortion of a head-mounted display device.

According to an aspect of the present invention, there is provided a head-mounted display device including: a display unit for displaying an image; A main lens unit for magnifying an image displayed on the display unit and refracting the image in a direction of a user's eyeball; And a correction lens unit formed between the display unit and the main lens unit for correcting distortion of the image.

In an embodiment of the present invention, the correction lens unit may be attached to the display unit.

In an embodiment of the present invention, the one surface of the correction lens unit attached to the display unit may be formed to have the same shape as the attachment surface of the display.

In an embodiment of the present invention, the correcting lens unit may include a concave lens.

In an embodiment of the present invention, the concave lens may include an aspherical lens.

In an embodiment of the present invention, the concave lens may be formed with an intermediate window.

According to an embodiment of the present invention, the correction lens unit may further include a moving unit that moves the correction lens unit in the up, down, left, and right directions with reference to the display unit, in order to move the position of the image.

In an embodiment of the present invention, the correction lens unit may further include a moving unit that moves the correction lens unit in the forward and backward directions with reference to the display unit, in order to adjust the focal length of the image.

According to another aspect of the present invention, there is provided an image distortion correction method for a head-mounted display device, ; And barrel-distorting the pincushion-distorted image by the main lens unit to refract in the eyeball direction.

According to such a head-mounted display device and its image distortion correction method, the spherical aberration of the optical system of the head-mounted display device can be remarkably reduced by using a single lens.

Therefore, it is possible to reduce the image distortion due to the spherical aberration of the lens to provide a high-quality image, and at the same time to miniaturize and lighten the head-mounted display device, thereby improving the performance of the head-mounted display device.

Further, since the IOD (Inter Ocular Distance) and the focal distance of the head-mounted display device can be finely adjusted, it is possible to provide an optimal display environment to the user.

1 is a view showing an appearance of a head-mounted display device according to the present invention.
2 is an example of an optical system structure of a head-mounted display device according to an embodiment of the present invention.
3 is an example of an optical system structure of a head-mounted display device according to another embodiment of the present invention.
4 is a conceptual view illustrating image distortion in a conventional head-mounted display device for comparison with the present invention.
5 is a conceptual view illustrating correction of image distortion in a head-mounted display device according to the present invention.

The following detailed description of the invention refers to the accompanying drawings, which illustrate, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that the various embodiments of the present invention are different, but need not be mutually exclusive. For example, certain features, structures, and characteristics described herein may be implemented in other embodiments without departing from the spirit and scope of the invention in connection with an embodiment. It is also to be understood that the position or arrangement of the individual components within each disclosed embodiment may be varied without departing from the spirit and scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is to be limited only by the appended claims, along with the full scope of equivalents to which such claims are entitled, if properly explained. In the drawings, like reference numerals refer to the same or similar functions throughout the several views.

Hereinafter, preferred embodiments of a head-mounted display device and an image distortion correction method thereof will be described in more detail with reference to the drawings.

1 is a view showing an appearance of a head-mounted display device according to the present invention. 2 is an example of an optical system structure of a head-mounted display device according to an embodiment of the present invention.

A head mounted display (hereinafter referred to as "HMD") is a next-generation image display device which is used for viewing a large-sized screen or carrying out surgery or diagnosis while carrying it on the head.

Referring to FIGS. 1 and 2, the HMD device 1 according to the present invention includes a correction lens unit 500 for correcting distortion of an image. Since the correction lens unit 500 is composed of a single lens and is formed in close contact with the display unit 100 for displaying an image, the HMD device 1 is small in volume and light in weight. However, the appearance of the HMD device 1 is merely an example, and may be provided in various forms.

The HMD device 1 can display an image input from an external video output device such as a video device, a TV, or a computer, and the user can view a large screen at a certain distance You can enjoy the same effect as watching a video.

2, the optical system 10 of the HMD device 1 includes a display unit 100, a main lens unit 300, and a correction lens unit 500. The optical system 10 is an apparatus for forming an image of an object by using a phenomenon such as optical reflection or refraction.

The display unit 100 displays an image output from a video output unit (not shown) of the HMD device 1 or displays an image output from an external video output device such as a video device, a TV, or a computer.

The display unit 100 may be a liquid crystal display (LCD), a plasma display panel (PDP), a projector display, a shutter glass system, a lenticular system, a parallax barrier system Or a three-dimensional display using an autostereography or a hologram. In addition, a light emitting diode (LED), an organic light emitting diode (OLED), a light emitting polymer (LEP), an electroluminescence element (EL element) A field emission display (FED), a polymer light emitting display (PLED), or the like may be applied.

According to an embodiment, the display unit 100 may be a transparent display. It is possible to visually check the background image in addition to the contents displayed on the display unit 100 through the transparent display. This can be utilized to use Augmented Reality or Virtual Reality technology.

The main lens unit 300 enlarges the image output from the display unit 100 and refracts the image in the eyeball direction of the user. Specifically, the main lens unit 300 serves to generate a virtual image by shortening a focal length of the HMD device 1. The main lens unit 300 is spaced apart from the display unit 100 and the correction lens unit 500 by an imaging distance.

The main lens unit 300 may include a convex lens convex toward the display unit 100. As the material of the main lens unit 300, optical glass may be used. Optical glass is largely classified into crown glass and flint glass. However, it is possible to manufacture a lens having a large aberration with a small aberration by using a material containing barium, phosphoric acid, fluorine, etc. (having a smaller resolution than that with a large refractive index).

The correction lens unit 500 is formed between the display unit 100 and the main lens unit 300 to correct distortion of the image. The correction lens unit 500 may include a concave lens concave toward the display unit 100.

The concave lens included in the correction lens unit 500 may be an aspherical lens. The aspherical surface is a curved surface which slightly deviates from the spherical surface and has a structure such that it gradually becomes flat from the central portion to the peripheral portion as in the eyes.

The correction lens unit 500 may be attached to the display unit 100 and one surface of the correction lens unit 500 attached to the display unit 100 may be attached to the mounting surface 100 of the display unit 100, As shown in FIG. Accordingly, the correction lens unit 500 can be more closely attached to the display unit 100. [

L 'is designed to be smaller than the focal length of the main lens unit 300, if the distance between the correction lens unit 500 and the main lens unit 300 is defined as' L'. When the 'L' is changed, the entire magnification is changed, and the focus of the image sensed by the naked eye may appear blurred.

That is, the 'L' should be fixed so that the image of the display unit 100 is correctly focused on the naked eye. The 'L' is determined according to the magnification of the main lens unit 300. The larger the magnification is, the smaller the distance 'L' becomes. As the 'L' is smaller, a more compact HMD device is manufactured. However, when 'L' becomes smaller, image distortion occurs due to the high magnification main lens unit 300. There is a limit to reducing the 'L' due to such distortion.

The function of the correction lens unit 500 in the HMD device 1 according to the present invention is to reduce the distortion of the image. The reason for designing that the distance between the correction lens unit 500 and the display unit 100 does not exist is that the distance between the display unit 100 and the main lens unit 300 is minimized, (1). In addition, the correction lens unit 500 can focus the distortion correction area on the outer area of the display unit 100. [

More specifically, if the correction lens unit 500 is spaced a certain distance from the display unit 100, the distortion of the image by the correction lens unit 500 affects the entire image.

In order to limit the area to be corrected through the correction lens unit 500 to the outer area of the display unit 100, the lens shape of the correction lens unit 500 should be formed of a special aspheric surface rather than a spherical surface In such a case, the design becomes complicated and the manufacturing cost can rise. Accordingly, the correcting lens unit 500 can be brought into close contact with the display unit 100 to solve the above-described problem, and the assembling structure can be simplified.

1 and 2, the HMD device 1 may move the correction lens unit 500 in the up-and-down and left-right directions (X direction, Z direction) with respect to the display unit 100, (Not shown) for moving the light source in the Y direction.

When the correction lens unit 500 is moved in the vertical and horizontal directions, the position of the image displayed on the display unit 100 can be moved. When the correction lens unit 500 is moved in the forward and backward directions, the focal length of the image displayed on the display unit 100 can be adjusted.

The movement of the correction lens unit 500 can be performed by the user or automatically. Therefore, since the IOD (Inter Ocular Distance) and the focal length of the optical system 10 can be finely adjusted, it is possible to provide an optimal display environment to the user.

3 is an example of an optical system structure of a head-mounted display device according to another embodiment of the present invention.

The optical system 30 of the HMD device 1 according to the present embodiment is substantially the same as the optical system 10 of Fig. 2 except for the shape of the correction lens unit 700. [ Therefore, the same constituent elements as those of the optical system 10 of FIG. 2 are denoted by the same reference numerals, and a repeated description thereof is omitted.

3, the correction lens unit 700 of the optical system 30 according to the present invention is formed between the display unit 100 and the main lens unit 300 to correct distortion of the image. The correction lens unit 700 may include a concave lens concave toward the display unit 100. The correction lens unit 700 may be attached to the display unit 100.

The correction lens unit 700 has an intermediate window 750 formed therein. In this case, the area corrected through the correction lens unit 700 is only the outer area of the display unit 100, and the central area of the display unit 100 does not cause any optical change. Therefore, only by changing the shape of the correction lens unit 700, a correction region of an image can be designated, and thus the design of the optical system 30 can be simplified.

4 is a conceptual view illustrating image distortion in a conventional head-mounted display device for comparison with the present invention. FIG. 5 conceptually illustrates correction of image distortion in a head-mounted display device according to the present invention.

Referring to FIG. 4, there is shown a process of generating image distortion when there is no lens for correcting image distortion. The light emitted from the display unit 200 passes through the eyepiece lens 400, which causes distortion called barrel distortion. The barrel distortion is a distortion caused by a difference between an enlargement ratio at the center of the lens and an enlargement ratio at the outside of the lens, which is generated in the convex lens. Generally, as the lens magnification increases, the barrel distortion becomes worse. In the case of the eyepiece for the HMD, this distortion occurs severely because a high magnification lens is used to achieve a short focal distance.

Referring to FIG. 5, a correction lens unit 500 including a distortion correction lens according to the present invention is inserted. The light emitted from the display unit 100 passes through the distortion correcting lens (concave lens), resulting in pincushion distortion. Pincushion distortion is a distortion of a distorted form into a central portion of the image as opposed to a barrel distortion, which occurs in a concave lens.

 The distortion is canceled as the pincushion-distorted image passes through the eyepiece (convex lens) of the main lens unit 300. When the magnifications of the two lenses are the same, the distortion is completely stretched theoretically. However, in this case, the focal length becomes very long and can not be used as an optical lens of the HMD device. In the drawing, the image passed through the eyepiece is expressed as being completely distorted, but in reality, the magnification of the distortion correcting lens is relatively small, so that some distortion is corrected. However, this slight correction alone can result in a significant performance improvement.

The reason is that when designing an eyepiece, there is no extreme case of image distortion, and there is usually a slight level of distortion near the edge of the image. In this case, when the distortion correcting lens is inserted, the distortion is remarkably reduced. The distortion correction lens also alleviates the so-called concavity problem in which the display surface is curved. In the case of using only the eyepiece lens, as shown in FIG. 4, the center portion of the display is recessed, whereas the present invention has the effect of making the image appear relatively flat by the distortion correcting lens. When these effects are displayed in a comprehensive manner, the user can see the image with the lens distortion being relaxed.

According to the HMD device and the image distortion correction method of the present embodiment, a single lens is used to reduce image distortion due to the spherical aberration of the lens, thereby providing a high-quality image. Further, at the same time, since the HMD device can be made smaller and lighter, the performance of the HMD device can be improved.

Further, since the IOD (Inter Ocular Distance) and the focal distance of the HMD device can be finely adjusted, it is possible to provide an optimal display environment to the user.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims. You will understand.

1: HMD device 10, 30: Optical system
100: display unit 300: main lens unit
500, 700: auxiliary lens unit 750: window,

Claims (9)

A display unit for displaying an image;
A main lens unit for magnifying an image displayed on the display unit and refracting the image in a direction of a user's eyeball; And
And a correction lens unit formed between the display unit and the main lens unit to correct distortion of the image,
Wherein the correction lens unit includes a concave lens having an intermediate window formed therein.
The method according to claim 1,
Wherein the correction lens unit is attached to the display unit.
3. The method of claim 2,
Wherein the one surface of the correction lens unit attached to the display unit is formed to be the same as the shape of the attachment surface of the display.
delete The method according to claim 1,
Wherein the concave lens comprises an aspherical lens.
delete The method according to claim 1,
Wherein the correction lens unit further comprises a moving unit for moving the correction lens unit in the up, down, left, and right directions with respect to the display unit to move the position of the image.
The method according to claim 1,
Wherein the correction lens unit further comprises a moving unit that moves the correction lens unit in the forward and backward directions with reference to the display unit to adjust a focal length of the image.
A step of pincushion-distorting an outer region of an image displayed on the head-mounted display device by a correction lens unit including a concave lens having an intermediate window formed therein; And
Distorting the pincushion-distorted image by barrel-distorting the pincushion-distorted image by the main lens unit, and refracting the pincushion-distorted image in the eyeball direction.

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