KR20210096824A - Head Mounted Display - Google Patents

Abstract

A head mounted display comprises an optical prism and an imaging device. The imaging device is located above the optical prism to provide an image. The optical prism is located under the imaging device and in front of an observer to enlarge an image received from the imaging device and deliver it to the observer, and has a certain thickness in the direction of the observer's front view to secure an external view without distortion.

Description

Head Mounted Display

The present invention relates to a see-through head mounted display.

A head mounted display is a device that can be worn on the head, and it provides various conveniences to users by combining it with augmented reality technology beyond a simple display function.

In addition, the head mounted display is divided into a transmissive type that allows viewing of an image and an external background at the same time, and a shielded type that allows only the image to be viewed by blocking the outside.

Figure 1a shows the patent document US 9,207,443 B2, Surface 2 is composed of a Half Mirror. This sends half of the light of the microdisplay to the observer, but the other half passes through the Surface 2. Such light becomes a ghost image or causes noise light that lowers the contrast.

FIG. 1B shows an example of a ghost image and stray light. It can be seen that there is a ghost image in which the bright sun is visible from other positions, and there is also a faint stray light around the ghost image. Since the noise light as described above harms the original image, it is necessary to remove it.

There is an imaging device that is composed of an optical prism and an imaging device and is located above the optical prism to provide an image. It is characterized in that it is an optical prism that has a certain thickness in the viewing direction and can secure an external view without distortion.

In addition, the optical prism may include: a first surface that refracts light received from the imaging device and transmits it to a second surface;

a second surface under the first surface and positioned in the observer's direction with respect to the third surface to totally reflect the light transmitted from the first surface and refract the light transmitted from the third surface;

a third surface positioned between the second surface and the fourth surface to reflect the light transmitted from the second surface back to the second surface;

a fourth surface positioned in a direction opposite to the observer with respect to the third surface and having a curvature formed so that the interval between the second surface and the second surface is constant;

a bottom surface connected to the fourth surface and located below the optical prism;

a fifth surface connecting the lower end of the second surface and the bottom surface;

is composed of

In addition, the third surface is characterized in that the S-polarized light is reflected and the P-polarized light is transmitted.

In addition, the imaging device is characterized in that it emits S-polarized light.

In addition, when the head mounted display is placed so that the center of the image is visible in front of the viewer, the thickness of the optical prism in the front of the viewer is d, the vertical length of the fifth surface is h1, When the line parallel to the observer's front view point is the fourth surface and point P, and the vertical length between point P and the end point of the floor surface is h2, the following condition is satisfied.

h2/d > 0.4

If h1 > h2, then (h1-h2)/d > 0.35

If h2 > h1, then (h2-h1)/d > 0.8

In addition, the third surface is characterized in that it is expressed by the following equation.

는 각 항의 계수를 나타낸다.where z represents the sag value,

is the coefficient of each term.

According to the present invention, it is possible to provide a high-brightness image by using polarized reflection and removing noise light by using an optical prism with an inclined bottom surface.

1A is a view showing an example of a conventional head mounted display.
1B shows an example of noise light.
2 is a view showing a light path by polarization of the head mounted display according to an embodiment of the present invention.
3 is a view showing a configuration condition of an optical prism according to an embodiment of the present invention.
4 is a diagram illustrating a path of noise light according to an embodiment of the present invention.
5 is a view showing a path through which noise light is removed according to an embodiment of the present invention.
6 is a view for explaining the configuration conditions of the head mounted display according to an embodiment of the present invention.
7 is a diagram illustrating a path of noise light according to an embodiment of the present invention.
8 is a view showing a path through which noise light is removed according to an embodiment of the present invention.
9 is a diagram illustrating a path of noise light according to an embodiment of the present invention.

Hereinafter, an embodiment of the head mounted display 10 according to the present invention will be described with reference to the accompanying drawings.

In this process, the thickness of the lines or the size of the components shown in the drawings may be exaggerated for clarity and convenience of explanation. In addition, the terms to be described later are terms defined in consideration of functions in the present invention, which may vary according to the intention or custom of the user or operator. Therefore, definitions of these terms should be made based on the content throughout this specification.

The present invention relates to a head mounted display (10),

As shown in FIG. 2 , the optical prism 200 is provided in front of the observer 500 , and the imaging device 100 is provided above the optical prism 200 . Looking at the optical path, the imaging device 100 emits the image light 300 linearly polarized with S-polarized light. When the imaging apparatus 100 emits light that is not linearly polarized, a linearly polarizing plate may be provided between the imaging apparatus 100 and the optical prism 200 . Here, the S-polarized light is parallel to the horizontal plane and perpendicular to the optical path, and the P-polarized light is perpendicular to the S-polarized light and the optical path at the same time.

The image light 300 from the imaging apparatus 100 is refracted on the first surface 210 under the imaging apparatus 100 and is located near the front view point of the observer 500 under the first surface 210. Total reflection from the second surface 220 reaches the third surface 230 . The third surface 230 is coated with a polarization reflective coating, so that the S-polarized light is reflected and the P-polarized light is transmitted. Since the image light 300 that has reached the third surface 230 has S-polarized light, it is reflected back to the first surface 210 , is refracted on the first surface 210 and transmitted to the observer 500 .

In addition, the third surface 230 is configured to be expressed by the following equation.

는 각 항의 계수를 나타내는데, 이는 제3면(230)의 중심을 직교 좌표계에 놓고 보았을 때, 비구면 형상이면서 x방향으로는 대칭이고, y 방향으로는 대칭이 아님을 의미 한다. 영상장치(100)에서 출발한 영상은 제1면(210) 내지 제3면(230)을 거치면서 관찰자(500)에게 전달되는데, 제3면(230)이 상기와 같이 구성되어야만 제1면(210), 제3면(230)의 굴절에 의한 색수차를 최소화 할 수 있고, 관찰자(500)와 영상장치(100)가 직각으로 배치되지 않음으로 인해서 발생하는 영상의 찌그러짐을 최소화 할 수 있다. where z represents the sag value,

represents the coefficient of each term, which means that when the center of the third surface 230 is placed in the Cartesian coordinate system, it has an aspherical shape and is symmetrical in the x-direction and not symmetrical in the y-direction. The image from the imaging apparatus 100 is transmitted to the viewer 500 while passing through the first surface 210 to the third surface 230, and the third surface 230 must be configured as described above. 210) and chromatic aberration due to refraction of the third surface 230 can be minimized, and image distortion caused by the observer 500 and the imaging apparatus 100 not being disposed at right angles can be minimized.

On the other hand, noise light such as ghost image and stray light is generated by total reflection or Fresnel reflection of light passing through the third surface 230 on the fourth surface 240 and the bottom surface 250 as shown in FIGS. 4 and 7 . .

Here, the ghost image refers to the light that makes the image appear double, and the stray light refers to the light that lowers the contrast of the image.

In the present invention, since the S-polarized image light 300 does not pass through the third surface 230, noise light should not be generated. Light 300 will be present

1. The imaging apparatus 100 does not have a polarization rate of 100%.

2. When the image light 300 is refracted on the first surface 210 and reflected from the second surface 220, the direction of polarization is slightly rotated.

3. The third surface 230 polarization reflection coating does not have 100% polarization reflectance for S-polarized light.

Therefore, some light passes through the third surface 230 and generates noise light.

In order to remove such noise light, the optical prism 200 is configured as follows with reference to FIGS. 3 and 6 . When the optical prism 200 is disposed so that the center of the image is visible in front of the observer 500, the thickness of the optical prism 200 at the observer's front view is d, and the vertical length of the fifth surface 260 is h1. , when a line parallel to the front view of the observer 500 passing through the lower end point of the third surface 230 is the fourth surface 240 and the point P is the fourth surface 240 and the bottom surface connected to the If the vertical length between the endpoint of 250) and the point P is h2, the following condition must be satisfied.

① h1/d > 0.35

② If h1 > h2, (h1-h2)/d > 0.3

③ If h2 > h1, (h2-h1)/d > 0.7

The above condition prevents the noise light generated by the light from the imaging device 100 passing through the third surface 230 from being directed toward the observer 500 .

Looking at the case of h1>h2 as shown in FIG. 4 , when the reproduction ① and ② are not satisfied, a part of the light emitted from the imaging device 100 passes through the third surface 230 and then passes through the fourth surface ( 240 ) is transmitted to the bottom surface 250 , and the fifth surface 260 is refracted by total reflection or Fresnel reflection from the bottom surface 250 to be seen by the observer 500 . However, when the above condition is satisfied as shown in FIG. 5 , the light passing through the fifth surface 260 is directed down the gaze of the observer 500 , and thus is invisible to the observer 500 .

Also, looking at the case where h2 > h1 as shown in FIG. 6 , if ① and ③ are not satisfied, a part of the light emitted from the imaging apparatus 100 passes through the third surface 230 and then at the bottom surface 250 . After total reflection or Fresnel reflection, total reflection or Fresnel reflection is performed on the fourth surface 240 , and reaches the viewer 500 through the fifth surface 260 . However, when the above condition is satisfied as shown in FIG. 7 , the light reflected from the fourth surface 240 is directed down the gaze of the observer 500 and is not visible to the observer 500 .

In addition, if the equations ①, ②, and ③ are not satisfied, light from the imaging apparatus 100 is reflected from the bottom surface 250 and returned to the imaging apparatus 100 as shown in FIG. 9 . The light returned to the imaging device 100 is reflected or scattered again by the imaging device 100 to be mixed with the original image light 300 . This causes the contrast to deteriorate.

Also, the bottom surface 250 may be formed not only as a straight line but also as a curved surface. This can be appropriately adjusted according to the curvature and tilt degree of the curved surfaces of the second surface 220 and the fourth surface 240 .

On the other hand, since the external light 400 has natural polarization, the external light 400 refracted on the fourth surface 240 transmits only the P-polarized light on the third surface 230 through the first surface 210 . Since it is transmitted to the observer 500 , the image light 300 and the external light 400 can be viewed at the same time.

As described above, the present invention uses an imaging device 100 that is a transmissive type capable of viewing an image and the outside at the same time and emits linearly polarized light and a third surface 230 that reflects the linearly polarized light. is removed, and the remaining noise light that has not been removed is emitted to the outside of the optical prism 200 in a direction invisible to the observer 500 so that there is no ghost image and high contrast can be achieved.

The invention is illustrated in the drawings Although it has been described with reference to the example, this is only exemplary, and those of ordinary skill in the art to which It will be appreciated that examples are possible.

Accordingly, the true technical protection scope of the present invention should be defined by the claims.

10: Head mounted display
100: video device
200: optical prism
210: first side
220: second side
230: 3rd page
240: the fourth side
250: bottom
260: 5th page
300: image light
400: external light
500: observer
● : S polarization
↕: P polarization

Claims (6)

There is an imaging device that is composed of an optical prism and an imaging device and is located above the optical prism to provide an image. Head mounted display, characterized in that it is an optical prism that has a certain thickness in the direction of the viewpoint and can secure the external view without distortion. The method of claim 1,
The optical prism may include: a first surface that refracts light received from the imaging device and transmits it to a second surface;
a second surface positioned under the first surface and positioned in the observer's direction with respect to the third surface to totally reflect the light transmitted from the first surface and refract the light transmitted from the third surface;
a third surface positioned between the second surface and the fourth surface to reflect the light transmitted from the second surface back to the second surface;
a fourth surface positioned in a direction opposite to the observer with respect to the third surface and having a curvature formed so that the interval between the second surface and the second surface is constant;
a bottom surface connected to the fourth surface and located below the optical prism;
a fifth surface connecting the second surface lower end and the bottom surface;
Head mounted display, characterized in that consisting of. The head mounted display according to claim 1, wherein the third surface reflects S-polarized light and transmits P-polarized light. The head mounted display of claim 1, wherein the imaging device emits S-polarized light. The method of claim 1,
When the head mounted display is placed so that the center of the image is visible in front of the observer, the thickness of the optical prism in the front of the observer is d, the vertical length of the fifth side is h1, and the observer passes through the lower end point of the third side. When the line parallel to the front view of the fourth surface and the point P are the vertical length between the point P and the end point of the bottom surface is h2, the head mounted display, characterized in that it satisfies the following conditions.
h2/d > 0.35
If h1 > h2, then (h1-h2)/d > 0.30
If h2 > h1, then (h2-h1)/d > 0.7 The method of claim 1
The third surface is a head mounted display, characterized in that expressed by the following equation.

where z represents the sag value,

is the coefficient of each term.

Images