KR100354671B1 - Optical System for Head Mount Display - Google Patents

Abstract

The present invention relates to a head mounted display system. The present invention provides a reflective liquid crystal display for displaying an image; A light source disposed on one side of the reflective liquid crystal screen so as to face the same direction as the image plane of the liquid crystal screen; An illumination dispersing unit disposed in front of the light source to disperse and refract light rays of the light source; A polarization splitter disposed to be inclined at a lower portion of the illumination scattering unit so as to separate the light rays emitted from the illumination scattering unit and reflect the light rays to the image surface of the reflective liquid crystal screen; A correction lens disposed in front of the image plane of the liquid crystal screen and refracting the image at a predetermined angle; An eyepiece disposed in front of the polarization splitter to enlarge an image of the liquid crystal screen; And a protective goggle disposed in front of the eyepiece. The present invention has the effect of enhancing the light efficiency by maximizing the light of the light emitting diode using an illumination prism, a prism sheet, a polarization splitting sheet, a polarizer, and the like, and using a light emitting diode arranged in parallel with a liquid crystal screen and a prism By illuminating the LCD screen, the height of the lighting unit and the overall height of the system can be reduced, thereby miniaturizing the device. In addition, by installing a correction lens on the screen of the liquid crystal screen to pre-refract the light rays of the image, distortion aberration is corrected, so that the configuration and thickness of the eyepiece can be simplified or the distance between the eyepiece and the liquid crystal screen can be adjusted. It has the advantage of being slim.

Description

Optical System for Head Mount Display

The present invention relates to a head mounted display configured to view a stereoscopic image through a liquid crystal screen close to two eyes, and in particular, to increase the resolution of the image while minimizing distortion caused by the movement of the eyes as well as the device. An optical system for a head mounted display that can enlarge the size of an image without making it large.

As is well known, a head mount display is a device configured to give a wearer a feeling of being in a virtual space through a built-in liquid crystal screen and various sensors for detecting a movement of a face.

The head mounted display not only provides a realistic virtual space for entertainment games, but also can be configured to arbitrarily set various virtual environments according to the operator's choice, so that various embodiments in various industries, such as architecture and interior, are preliminary. It is configured to be applied. In particular, in recent years, by combining a variety of interfaces and head-mounted display, such as a body suit that can detect the movement of the human body, a virtual reality system (VR system) has been developed and used to further improve the realism and liveliness.

On the other hand, such a head mounted display is provided with an optical system consisting of a liquid crystal screen, a lighting device and a lens. This optical system allows an image to appear on a liquid crystal screen, and can be configured in various ways depending on the arrangement of the components. As an example, generally used optical systems are schematically illustrated in FIGS. 1 and 2. Referring to this, first, in the optical system of FIG. 1, an illuminating device 2 serving as a light source of the liquid crystal screen 1 is disposed behind the liquid crystal screen 1 representing an image, and the eyepiece is located in front of the liquid crystal screen 1. (3) is arranged.

In the optical system of FIG. 2, the liquid crystal screen 1 is disposed horizontally to face downward, and the polarized beam splitter 4 is disposed at an angle of about 45 ° below the vertical direction of the liquid crystal screen 1. At the rear of the divider 4, a concave reflection mirror 5 for enlarging and reflecting the image of the liquid crystal screen 1 is arranged. The lighting device 2 is arranged behind the liquid crystal screen 1 as in FIG. 1. Here, the liquid crystal screen 1 in Figs. 1 and 2 is a transmissive liquid crystal, and is configured to display an image using the illuminating device 2 disposed behind as a light source.

However, the conventional optical system having such a configuration has the advantage that the configuration is simple and the device can be made slimmer and compact. However, as described above, an expensive transmissive liquid crystal screen 1 must be used. There was this. In addition, since the light source must be provided over the entire back surface of the transmissive liquid crystal screen 1, there was a disadvantage in that the light efficiency was lowered. In particular, the optical system of FIG. 2 has a superior effect than the optical system of FIG. 1 in using the polarization splitter 4 to increase the sharpness of the image, but the eye shape of the viewer is reflected on the concave reflection mirror 5. There seemed to be a problem.

3 shows another example of an optical system for a head mounted display. According to this, the optical system of another example arranges the liquid crystal screen 6 vertically, the eyepiece 7 is disposed in front of the liquid crystal screen 6, and between the liquid crystal screen 6 and the eyepiece 7. The polarization splitter 8 is disposed at an angle of approximately 45 ° toward the liquid crystal screen 6. Here, the liquid crystal screen 6 is a reflection type liquid crystal, and is configured to receive an image of the illumination device 9 disposed on the front side through the polarization splitter 8.

On the other hand, the optical system of Figure 3 has the advantage that the production cost is reduced and the light efficiency is improved by using a reflective liquid crystal having a low cost and a high pixel. However, there is a disadvantage that the size of the device is relatively larger than that of the optical system of FIGS. 1 and 2, such as the installation space of the lighting device 9 and the polarization splitter 8 must be secured. In particular, the eyepiece of the optical system of FIG. 3 is thickly configured to produce an effect such as viewing a 40-inch screen at a distance of 2m. The eye relief, which is a distance between the eyepiece and the pupil, is relatively high. The shortening, the size of the exit mirror placed in the pupil of the eye is small, there is a disadvantage that the image of the peripheral area is not visible even with a slight movement of the eye.

Accordingly, the present invention has been made to solve such a problem, the object of which is to minimize the distortion caused by the movement of the eyes, and to enhance the resolution of the image to provide the best image for the head-mounted display wearer To provide a system.

1 is a view schematically showing the configuration of a conventional optical system for a head mounted display,

2 and 3 schematically show another example of a conventional optical system for a head mounted display,

4 schematically shows the configuration and arrangement of an optical system for a head mounted display according to the invention,

5 shows another embodiment of an illumination dispersing part of the optical system according to the present invention;

6 shows another embodiment of a correcting lens of the optical system according to the present invention;

7 is a side cross-sectional view of a head mounted display showing that the optical system of the present invention is installed in a head mounted display.

♣ Explanation of symbols for the main parts of the drawing ♣

10: liquid crystal screen 20: lighting unit

22: light emitting diode 30: lighting dispersion unit

31: Lighting prism 32: Reflective sheet

33: first prism sheet 34: second prism sheet

35: polarizer 36: first polarization split sheet

37: second polarization split sheet 40: polarization splitter

50: eyepiece 52: convex lens

54: concave lens 60: protective glasses

70: convex correction lens 72: concave correction lens

In order to achieve the above object, the present invention provides a head mounted display for viewing a stereoscopic image, comprising: a reflective liquid crystal screen displaying an image; A light source disposed on one side of the reflective liquid crystal screen so as to face the same direction as the image plane of the liquid crystal screen; An illumination dispersing unit disposed in front of the light source to disperse and refract light rays of the light source; A polarization splitter disposed to be inclined at a lower portion of the illumination dispersing unit so as to separate light rays emitted from the illumination dispersing unit and reflect the light rays to the image surface of the reflective liquid crystal screen; A correction lens disposed in front of the image surface of the liquid crystal screen and refracting the image at a predetermined angle; An eyepiece disposed in front of the polarization splitter to enlarge an image of the liquid crystal screen; Characterized in that the protective glasses disposed in front of the eyepiece.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the optical system for head mounted display according to the present invention will now be described in detail with reference to the accompanying drawings.

4 is a view schematically showing a configuration and arrangement of an optical system for a head mounted display according to the present invention, FIG. 5 is a view showing another embodiment of an illumination dispersing unit of the optical system according to the present invention, and FIG. Fig. 2 shows another embodiment of the correction lens of the optical system according to the invention. First, as shown in Fig. 4, in the optical system for head mounted display according to the present invention, the liquid crystal screen 10 representing an image is disposed vertically. This liquid crystal screen 10 is a reflection type liquid crystal and displays an image using the illumination irradiated from the front as a light source.

In addition, an upper portion of the liquid crystal screen 10 includes an illumination unit 20 for providing a light source to the liquid crystal screen 10, and an illumination dispersion unit 30 that refracts while dispersing light rays of the illumination unit 20. In detail, the lighting unit 20 is a light emitting diode 22 and is disposed to face in the same direction as the image plane of the liquid crystal screen 10 above the liquid crystal screen 10 to provide a light source.

In addition, the illumination dispersing unit 30 is disposed in front of the light emitting diode 22 to be refracted while reaching the liquid crystal screen 10 while dispersing the light rays emitted from the light emitting diode 22, thereby the illumination prism 31 Have The illumination prism 31 serves to disperse the light rays emitted from the light emitting diodes 22, and the reflective sheet 32 is disposed on the upper surface thereof. The reflective sheet 32 reflects back the light transmitted through the illumination prism 31 without being refracted. The first prism sheet 33 and the second prism sheet 34 for condensing the light beams refracted by the illumination prism 31 and the first prism sheet 33 and the second prism are disposed under the illumination prism 31. Polarizers 35 that polarize the light re-emitted through the sheet 34 are sequentially arranged. Here, the first prism sheet 33 and the second prism sheet 34 serves to condense the light diffused from the reflective sheet 32 at an angle of about 70 ° to irradiate the liquid crystal screen 10. The polarizer 35 is slightly lower in polarization performance of the polarization splitter 40 to be described later to reduce the contrast of the image is installed in advance of the polarization splitter 40 to adjust the contrast of the light beam, the polarization splitter 40 Play a role

Meanwhile, FIG. 5 shows another embodiment of the illumination dispersing unit 30. Accordingly, it can be seen that the illumination dispersing unit 30 according to another embodiment may include the first polarization split sheet 36 and the second polarization split sheet 37 in place of the polarizer 35 described above. The first polarization splitting sheet 36 and the second polarization splitting sheet 37 adjust the contrast of the image as well as the brightness of the image at the same time as the polarizer 35 described above. . This is because the above-mentioned polarizer 35 transmits only about 40% of the light emitted again through the first prism sheet 33 and the second prism sheet 34, whereas the first polarization split sheet 36 and the second This is because the polarization split sheet 37 transmits about 60% of the light rays of the first prism sheet 33 and the second prism sheet 34. Therefore, the first polarization splitting sheet 36 and the second polarization splitting sheet 37 can be equipped with the function of adjusting the contrast, that is, the brightness of the image, together with the contrast adjustment function.

Referring again to FIG. 4, in front of the liquid crystal screen 10, a polarization splitter 40 is disposed downwardly at an approximately 45 ° angle to the liquid crystal screen 10. The polarization splitter 40 separates the linearly polarized light emitted through the polarizer 35 and reflects it to the liquid crystal screen 10. And in front of the polarization splitter 40, an eyepiece 50 for enlarging an image of the liquid crystal screen 10 is provided.

The eyepiece 50 is a composite lens in which the convex lens 52 and the concave lens 54 are bonded to each other so that chromatic aberration, which forms an image at different points according to colors, does not occur as shown in FIG. 4. The last lens of the composite lens is an aspherical surface, which improves the resolution of the image while correcting the distortion aberration as the image gets farther from the center. In particular, only the conical constant is used without using higher order aspheric coefficients to minimize the distortion aberration caused by eye movement. For reference, an aspherical surface is formed on at least one surface, and is used to achieve a necessary aberration correction state with a small number of surfaces. The eyepiece 50 includes a concave lens 54 arranged in the wearer's eyes and a convex lens 52 facing the liquid crystal screen 10 to extend the focus in the liquid crystal screen 10 direction. It is configured to sufficiently secure the installation space of the polarization splitter 40 by taking the form).

In the eyepiece 50 having such a configuration, viewing the 44-inch image with the liquid crystal screen 10 at a distance of approximately 2 m has the same effect. In particular, the eyepiece 50, which is a double compound lens, lengthens the eye relief and increases the size of the exit pupil so that the image of the periphery can be seen accurately even if the wearer moves his eyes. In addition, the eyepiece 50, which is a bi-junction lens, has almost no vignetting that the brightness of the edge of the image is lower than that of the center due to the non-axis beam passing obliquely through the lens.

The eyepiece 50 is disposed in front of the eyepiece 50, and the eyeglass 60 is a light beam reflected from an upper portion of the eyepiece 50, that is, a light emitting diode leaked from the upper lighting unit 20. The light beam of (22) is prevented from shining directly on the wearer's eyes to prevent glare. In particular, the protective glasses 60 controls the ultraviolet rays and strong visible light harmful to the eyes emitted from the liquid crystal screen 10, and by correcting the diffuse reflection allows the wearer to see a soft and clear screen, can reduce eye fatigue Play a role. The protective glasses 60 is coated with a polarizing film, a UV blocking film, a PMMA film, and the like.

Meanwhile, as shown in FIGS. 4 and 6, correction lenses 70 and 72 are disposed in front of the liquid crystal screen 10 to approach the image plane. The correction lenses 70 and 72 are refracted at a predetermined angle before the light beam of the image is incident on the eyepiece 50, so that the light of the image passing through the eyepiece 50 falls or approaches the optical axis. Failure type distortion aberration and cylindrical distortion aberration are prevented in advance. This makes it possible to further reduce the distortion aberration of the image to make the eyepiece 50 thinner, and to simplify the construction of the eyepiece 50, which is a composite lens. In addition, by refraction of the light rays of the image in advance, it is possible to narrow the gap between the eyepiece 50 and the liquid crystal screen 10 to realize a slimmer system.

Here, FIG. 4 is a view to prevent the cylindrical distortion aberration generated as the light rays of the image come closer to the optical axis by refracting the light rays of the image using the convex correction lens 70. FIG. By refracting the light rays of the image by using a), it is a view to prevent the failure-type distortion aberration that occurs when the light rays of the image fall from the optical axis. Although not shown, a cylindrical and failed distortion aberration can be prevented by using a correction lens having an aspherical surface. Meanwhile, any one of the convex correction lens 70, the concave correction lens 72 or the aspherical correction lens is appropriately selected and disposed according to the characteristics of the eyepiece 50.

On the other hand, when the light is generated in the light emitting diodes 22 in the state that the signal is applied to the liquid crystal screen 10 by this configuration, the light is refracted at right angles through the illumination prism 31 to be dispersed and polarized light splitter 40 Is investigated. In this case, the light beams passing through the illumination prism 31 and going straight are reflected by the reflecting sheet 32 and irradiated to the polarization splitter 40, and the light rays refracted at right angles by the illumination prism 31 are first prism sheets ( 33) and the second prism sheet 34 and the polarizer 35 or the first polarization splitting sheet 36 and the second polarization splitting sheet 37 while condensing the brightness and brightness is adjusted. The light beams passing through the first prism sheet 33, the second prism sheet 34, the polarizer 35, or the first polarization split sheet 36 and the second polarization split sheet 37 and the diffusion sheet 25 are again It is separated while passing through the polarization splitter 40 and reflected on the liquid crystal screen 10.

The liquid crystal screen 10 displays the image using the light beam as a light source, and the head mounted display wearer can view the image of the liquid crystal screen 10 through the eyepiece 50. At this time, the image of the liquid crystal screen 10 is greatly enlarged by viewing the 44-inch image at a distance of approximately 2 m by the eyepiece 50. In particular, the exit pupil distance is increased and the exit pupil is enlarged by the eyepiece 50, which is a bi-junction lens, so that the wearer can view the image of the liquid crystal screen 10 in a more stable state. In addition, the wearer of the head mounted display can see a sharper and clearer image such as the resolution of the image is increased and the distortion aberration is corrected by the correction lenses 70 and 72.

7 shows that the optical system of the present invention having such a configuration is provided in the head mounted display. Briefly, the housing 80 of the head mounted display is provided with a pair of barrels 82 (only one of the barrels is cut out and shown in FIG. 7). The barrel 82 is provided with the above-described optical system.

That is, the barrel 82 has a first installation space 84 having a front opening, and a second installation space 85 formed so as to open with the first installation space 84 above the first installation space 84. . A liquid crystal screen 10 for displaying an image is installed behind the first installation space 84, and a correction lens 70 is installed on the front surface of the liquid crystal screen 10. In addition, it can be seen that the eyepiece 50 for enlarging an image of the liquid crystal screen 10 is installed in front of the first installation space 84. In addition, a polarization splitter 40 is disposed at an angle of about 45 ° between the liquid crystal screen 10 and the eyepiece 50 so that the polarization splitter 40 moves downward toward the liquid crystal screen 10.

On the other hand, it can be seen that the lighting unit 20 and the lighting dispersion unit 30 are installed in the second installation space 85 of the barrel 82. That is, the light emitting diode 22 of the lighting unit 20, which is a light source of the liquid crystal screen 10, is installed to be parallel to the liquid crystal screen 10 at the rear of the second installation space 85. In the front, the illumination prism 31 of the illumination dispersion part 30 which refracts the light ray of the light emitting diode 22 at right angles is provided. The reflective sheet 24 is disposed on the top surface of the illumination prism 31, and the first prism sheet 33, the second prism sheet 34, and the polarizer 35 are sequentially installed on the bottom surface of the illumination prism 23. . Here, the first polarization split sheet 36 and the second polarization split sheet 37 may be provided in place of the polarizer 35. On the other hand, the protective lens 60 is installed in the housing 80 in front of the eyepiece 50, the printed circuit board (P) for controlling the liquid crystal screen 10 and the light emitting diode (22) on the rear surface of the barrel (82). You can see that) is installed.

As described above, the optical system of the present invention is disposed in the housing 80 of the head mounted display to provide the best image to the wearer. In particular, as can be seen in the figure, since the lighting unit 20 is disposed in parallel with the liquid crystal screen 10 and its height is configured to be low, the overall height of the head mounted display is reduced. The first polarization split sheet 36 and the second polarization split sheet (instead of the illumination prism 31, the first prism sheet 33, the second prism sheet 34, the polarizer 35, or the polarizer 35) 37) and the like, the light emitting diode 22 can be utilized to the maximum. In addition, by providing the correction lens 70 on the screen of the liquid crystal screen 10, the distortion aberration is corrected has the advantage that the system can be made slim.

As described above, the optical system for a head mounted display according to the present invention has the effect of increasing the light efficiency by utilizing the light of the light emitting diode to the maximum by using an illumination prism, a reflection sheet, a prism sheet, a polarization splitting sheet, and a polarizer.

In addition, by illuminating the liquid crystal screen using a light emitting diode and a prism arranged in parallel with the liquid crystal screen, the height of the lighting unit and the overall height of the system are reduced, thereby miniaturizing the device.

In addition, the use of the bi-junction lens having an aspherical surface, the resolution of the image is increased, the distortion aberration is corrected has the effect of providing a more sharp and clear image to the wearer.

In addition, by installing a correction lens on the screen of the liquid crystal screen and refracting the rays of the image in advance, distortion aberration is corrected to simplify the configuration and thickness of the eyepiece or to adjust the distance between the eyepiece and the liquid crystal screen. It has the advantage of being slim.

Claims (7)

In the head mounted display, A reflective liquid crystal screen for displaying an image; A light source disposed on one side of the reflective liquid crystal screen so as to face the same direction as the image plane of the liquid crystal screen; An illumination dispersing unit disposed in front of the light source to disperse and refract light rays of the light source; A polarization splitter disposed to be inclined at a lower portion of the illumination dispersing unit so as to separate light rays emitted from the illumination dispersing unit and reflect the light rays to the image surface of the reflective liquid crystal screen; A correction lens disposed in front of the image surface of the liquid crystal screen and refracting the image at a predetermined angle; An eyepiece disposed in front of the polarization splitter to enlarge an image of the liquid crystal screen; And a protective goggle disposed in front of said eyepiece. The optical system of claim 1, wherein the light source is a light emitting diode. The light emitting device of claim 1, wherein the illumination dispersing unit comprises: an illumination prism for dispersing light rays of the light source, a first prism sheet and a second prism sheet for condensing the light rays dispersed by the illumination prism, and the first prism sheet and the second prism sheet. An optical system for a head mounted display, characterized in that it comprises a polarizer for polarizing to adjust the contrast of the light re-emitted through the prism sheet. The light emitting device of claim 1, wherein the illumination dispersing unit comprises: an illumination prism for dispersing light rays of the light source, a first prism sheet and a second prism sheet for condensing the light rays dispersed by the illumination prism, and the first prism sheet and the second prism sheet. An optical system for a head mounted display, characterized in that it comprises a first polarization splitting sheet and a second polarization splitting sheet to polarize so as to adjust the brightness of the light re-emitted through the prism sheet. The optical system for a head mounted display according to claim 1, wherein the correction lens is a convex correction lens to prevent cylindrical distortion aberration. The optical system for a head mounted display according to claim 1, wherein the correcting lens is a concave correcting lens to prevent a failure type distortion aberration. 2. The optical system for a head mounted display according to claim 1, wherein the eyepiece is made by joining a concave lens and a convex lens so that chromatic aberration does not occur, and the concave lens is formed with an aspherical surface to correct distortion aberration.