KR20130116548A - Optical system for see-through type head mounted display - Google Patents

Abstract

PURPOSE: An optical system for a see-through type head mounted display is provided to implement a high definition image; to transmit a part of the light of a lens and a mirror; and to reflect the remaining light, thereby enabling a user to view the image and an external object. CONSTITUTION: An optical system for a see-through type head mounted display includes a display element (110), a condensing lens (130), a polarizer (140), a semi-transparent mirror (150), a phase delay plate (160), and a total reflection curved surface mirror (170). The display element emits the light of an image. The polarizer selectively transmits the light which is emitted and positioned at the front of the display element to line polarized light and increases a light quantity. The semi-transparent mirror transmits a part of the line polarized light and reflects the remaining line polarized light. The total reflection curved surface mirror reflects total light transmitted by the semi-transparent mirror. When the light reflected from the front of total reflection curved surface mirror is the line polarized light, the phase delay plate converts the same into circular polarized light. When the light reflected from the front of total reflection curved surface mirror is the circular polarized light, the phase delay plate converts the same into the line polarized light.

Description

Optical System For See-Through Type Head Mounted Display

The present invention relates to an optical system for a transmissive head mounted display, and more particularly, to an optical system for a transmissive head mounted display, and more particularly to an image device, an illumination system, a plurality of lenses, and a 3D stereo mirror (StereoScope). Full HD can be realized vividly, and the see-through type head can see both the image and the external object by transmitting part of the light and reflecting part of the light. An optical system for a mount display.

In general, the optical system for a head mounted display (HMD, which is referred to as below) is used to precisely construct a large virtual screen at a long distance by using a precise optical device to generate an image light generated at a position very close to the eye. It is an image display device that allows a user to view an enlarged virtual image by forming a focus. The optical system for HMD was originally used for military use, but due to the rapid progress of high performance and miniaturization of computer system, and the rapid development of display devices, the concept of wearable computer was presented, and thus the monitor worn on the body As a wearable monitor, the necessity and possibility of the optical system for HMD were studied.

The optical system for HMD is a binocular binocular that forms each independent optical path in both eyes in two display elements, and a single plate binocular that forms a symmetric optical path in both eyes using one display element. The display device is divided into a single plate monocular type that provides a light path to only one eye of both eyes.

In the case of using a conventional two-sided binocular, there is a problem in that the cost of the product is increased because the two expensive display elements must be used.

In addition, the existing HMD optical system was mostly a see-closed type, which is blocked by the wearer's vision around 25 mm from the pupil, so that the user can see the image in a blackout state, and thus eyes fatigue during long time wearing There was a problem that causes a variety of side effects, such as a surge in the human body.

The present invention has been made to solve the above-described problems, the object of the present invention can vividly implement a three-dimensional high-definition (Full HD) by using an image device, an illumination system, a plurality of lenses and a 3D stereoscope (Virtual scope) Rather, it provides an optical system for a see-through type head mounted display in which a lens and a mirror transmit part of light and reflect part of it to see both an image and an external object.

In addition, another object of the present invention is a single plate binocular head capable of securing an equivalent wide field of view (FOV) and sufficient EYE RELIEF provided by a double plate binocular optical system. The present invention provides a mount display optical system.

According to an aspect of the present invention, there is provided an optical system for a transmissive head mounted display comprising: a display element for emitting light constituting an image; A polarizer positioned in front of the display element to selectively transmit the emitted light to the linearly-planned light to increase the amount of light; A half mirror positioned in front of the light propagation direction of the polarizer to transmit a portion of the linearly-viewed light and reflect a portion thereof; A total reflection curved mirror positioned in front of the light propagation direction of the transflective mirror to reflect all of the transmitted light; And a phase delay plate positioned in front of the total reflection curved mirror to convert circularly polarized light into circularly polarized light or to convert linearly polarized light into totally polarized light.

In addition, the phase delay plate is preferably a λ / 4 phase delay plate (QWP: Quater Wavelength Plate).

The optical system for a transmissive head mounted display may further include a condensor lens positioned in front of the light traveling direction of the display element to collect the emitted light.

In addition, the condensing lens is preferably composed of a combination of lenses selected from at least one spherical lens or at least one aspherical lens.

In addition, the total reflection curved mirror is preferably composed of a spherical mirror or an aspheric mirror.

The optical system for a transmissive head mounted display may further include adjusting means for adjusting a distance between both eyes.

The optical system for a transmissive head mounted display may further include stop means for stopping the image output of the display element when the external object is to be viewed.

The display device may be a reflective liquid crystal on silicon (LCoS), a digital light processing device (DLP), a micro LCD device with a light source, or a micro OLED device that emits light. Do.

According to the present invention, the optical system for a transmissive head mounted display can not only vividly realize full HD with high definition (Full HD) by using an image device, an illumination system, a plurality of lenses, and a 3D stereoscope, but also a lens and a mirror. Part of the light is transmitted and part is reflected to realize the see-through type that can see both the image and the external object.

According to the present invention, it is possible to make the product high resolution and light weight, and to realize an ideal image for the human eye.

1 is a view showing an optical system for a transmissive head mounted display according to an embodiment of the present invention.
2 is a block diagram of an optical system for a transmissive head mounted display according to an embodiment of the present invention.
3 is a graph showing a resolution characteristic of an optical system for a transmissive head mounted display according to an embodiment of the present invention.
4 is a graph illustrating distortion characteristics of an optical system for a transmissive head mounted display according to an embodiment of the present invention.
5 is a graph showing astigmatic field characteristics of the optical system for a transmissive head mounted display according to an embodiment of the present invention.
6 is a graph illustrating Ray Aberration characteristics of the optical system for a transmissive head mounted display according to an embodiment of the present invention.
7 is a block diagram of an optical system for a transmissive head mounted display according to another embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: FIG. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise.

In addition, the term "unit" described in the specification means a unit for processing at least one function or operation, which may be implemented in hardware or software or a combination of hardware and software.

Throughout the specification, when a part is "connected" to another part, this includes not only a case where the part is directly connected, but also a case where another system is connected in the middle.

The HMD optical system is a device mounted on the head and used to provide an image to a user's eyes, and is used in various fields for displaying an image including virtual reality. The optical system for the HMD is generally formed in the shape of goggles or a frame of large glasses.

In the present invention, it is designed as a structure capable of more complex functions in a see-through type that can minimize the effect on the human eye. The optical system for HMD should be designed to meet the weight, miniaturization, and high resolution, and in order to satisfy these requirements, the design should be ideally close to the model of the human eye. In other words, satisfactory results such as chromatic aberration (Relative Field), spatial frequency resolution (MTF), and distortion aberration (Distortion) can be combined with the human eye to deliver the optimal image.

In addition, according to the explosive use of the current smartphone, it will be spotlighted as a convergence device with the smartphone, and will be presented as a new concept of augmented reality (VR).

Hereinafter, an optical system for a transmissive head mounted display according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view showing an optical system for a transmissive head mounted display according to an embodiment of the present invention.

As shown in (a) of FIG. 1, the transmission-type HMD optical system 100 includes a case main body in which optical systems such as a mirror and a lens are disposed, and a case leg formed integrally with the case main body to be mounted on the head. do.

As shown in FIG. 1B, the optical system for transmission HMD 100 may further include adjusting means 180 for adjusting the distance between both eyes 20. That is, since the distance between the eyes 20 for each person is different, the means for controlling the same makes the ergonomic optical system more convenient to use. In addition, the transmission-type HMD optical system 100 may further include a stop means 190 for stopping the image output of the display element 110 when the user wants to see the external object. When the user uses the transmission-type HMD optical system 100 and wants to see the outside as necessary, the stop means 190 stops the emission of the image and makes the outside visible.

2 is a block diagram of an optical system for a transmissive head mounted display according to an embodiment of the present invention.

Referring to FIG. 2, an optical system 100 for a transmissive HMD according to an embodiment of the present invention includes a display element 110, a condenser lens 130, a polarizer 140, and a half mirror. , 150), a phase retardation plate 160 and a total reflection curved mirror 170.

The display element 110 serves to emit light constituting the image. The display device 110 may be a reflective liquid crystal on silicon (LCoS), a digital light processing device (DLP), a micro LCD device with a light source, or a micro OLED device that emits light. Is preferably less than or equal to 1 inch. Meanwhile, the micro-reflective silicon liquid crystal display device, the digital light source display device, and the micro LCD device do not emit light by themselves, so the light source must be coupled from the outside. That is, a transmissive micro LCD panel using a backlight or a reflective micro LCD panel using a front light is possible. Since the micro OLED panel is self-luminous, a separate light source is not required, and the transmissive head mounted display optical system 100 can be configured more simply and compactly.

The condenser lens 130 is positioned in front of the light traveling direction of the display element 115 to collect the emitted light. The condenser lens 135 is a lens for obtaining a high illuminance by collecting light beams (bundles) emitted in a solid angle from a light source (light gland) in a smaller solid angle and obtaining a high illuminance. . Therefore, the aperture is larger than the focal length. The condenser lens 130 is preferably composed of a combination of lenses selected from at least one spherical lens or at least one aspherical lens.

Polarizer (140) is a condenser lens (Condensor lens, 130) is located in the front is an optical element that serves to increase the amount of light by selectively transmitting the focused light to the linearly flattened light. In general, the polarizer 140 is divided into a device that transmits only light having a desired polarization state and separates the light into two linearly polarized light. The polarizer 140 is preferably a wire-grid type polarizer. The wire grid polarizer may be a product of Moxtek. By using the wire grid polarizer, the transmissive head mounted display optical system 100 can be configured 3-4 times brighter than the conventional one. This configuration is also advantageous for securing the maximum field angle (FIELD OF VIEW, FOV) (50deg or more).

In addition, the wire lattice polarizer eliminates the problem of skew angle generated in the polarization beam splitter (PBS), thereby obtaining a very high contrast. Although the wire lattice polarizer has been conventionally used for radio waves, infrared detection, and the like, it can be used in the transmission type HMD optical system 100 that can be used in a short visible light region.

The transflective mirror 150 is positioned in front of the light traveling direction of the condenser lens 130 to transmit part of the collected light and reflect part of it. The transflective mirror 150 may also use a polarization beam splitter (PBS) depending on the type of display element 110. The transflective mirror 150 preferably sees through 50% of incident light.

(m은 정수)가 되도록 만든 광학소자이다. 90°의 위상 변화는 선편광을 원편광(또는 타원편광)으로, 원편광(또는 타원편광)을 선편광으로 만들 수 있지만, 선편광 방향이 두 주축 중 하나에 평행하면 어떤 종류의 위상 지연판(160)에서도 영향을 받지 않는다.The phase delay plate 160 converts the reflected linearly polarized light into circularly polarized light or changes the incident circularly polarized light into linearly polarized light. The phase retardation plate 160 is preferably a λ / 4 phase retardation plate (QWP). The λ / 4 phase retardation plate uses the birefringence phenomenon to determine the relative phase difference between normal and abnormal light.

(m is an integer). A phase change of 90 ° can make linearly polarized light (or elliptical) and linearly polarized light (or elliptical), but if the direction of linear polarization is parallel to one of the two major axes, then some kind of phase retardation plate 160 Is not affected.

, 결정의 광축 방향과 수직한 편광에 대한 굴절률이

이면 위상차는 다음과 같이 구할 수 있다.When the light is incident by using anisotropy of the material, the phase difference may be obtained by using different refractive indices in the x-axis direction and the y-axis direction of the phase retardation plate 160. The phase retardation plate 160 has a thickness t, a wavelength λ, and a refractive index with respect to polarization parallel to the optical axis direction of the crystal.

, The refractive index for the polarization perpendicular to the optical axis direction of the crystal

The phase difference can be obtained as follows.

(m은 정수)

(m is an integer)

가 될 때 그 위상 지연판(160)을 λ/4 위상 지연판이라 한다.here

When the phase delay plate 160 is referred to as λ / 4 phase delay plate.

The total reflection curved mirror 170 is positioned in front of the light propagation direction of the transflective mirror 150 to reflect all of the transmitted light. The total reflection curved mirror 170 is preferably composed of a spherical mirror or an aspheric mirror. The total reflection curved mirror 170 is preferably 100% of the incident light is reflected.

The operating principle of the optical system for transmission HMD 100 according to the embodiment of the present invention is as follows.

First, the light constituting the image emitted from the display element 110 is collected by the optimized condensing lens 130 and proceeds upward. The light constituting the image traveling in the upward direction is changed to single polarized light through the polarizer 145. The polarized light is transmitted through the transflective mirror 155, and then goes straight and passes through the phase retardation plate 165 located in the forward direction, preferably λ / 4 phase retardation plate, to be changed into linearly or circularly-viewed light. Proceeding to the curved mirror 175. The light constituting the image reflected back from the total reflection curved mirror 175 returns to the half mirror 155 and is refracted by the window 10 to proceed to form an image in the human eye 20.

3 is a graph showing a resolution characteristic of an optical system for a transmissive head mounted display according to an embodiment of the present invention. The resolution is more specifically called Modulation Transfer Field (MTF), which is the ability of the human eye to accept the decomposition of light. Contrast is more than 60% close to the eye and 0% at the edge of the field of view (FOV). In general, the resolution of a human eye with a visual acuity of 1.0 is about 1.0acrminute. Therefore, it is possible to distinguish a target composed of black and white bars corresponding to approximately 6.88 lp / mm at the specified distance of 250 mm.

At focus, the spatial frequency resolution (MTF) is about 20% at around 100 lp / mm.

4 is a graph illustrating distortion characteristics of an optical system for a transmissive head mounted display according to an embodiment of the present invention. It shows the distortion aberration of the optimized optical system when the diameter of the exit pupil (image in the open space of the aperture) is 8 mm.

Distortion aberration is a type of lens aberration, which is a phenomenon in which the magnification varies depending on a distance from a point on a photograph with respect to a given screen distance. As shown in FIG. 4, when the incident angles of light to the human eye are 2.85 °, 5.68 °, 8.49 °, and 11.25 °, it can be seen that they are designed within 1.5%.

5 is a graph showing astigmatic field characteristics of the optical system for a transmissive head mounted display according to an embodiment of the present invention. The astigmatism of the optimized optical system is shown when the diameter of the exit pupil is 8 mm.

Astigmatism refers to a phenomenon in which an image of an object distant from the main axis becomes a ring or radial blur without being a perfect point. As shown in FIG. 5, when the incident angles of light to the human eye are 2.85 °, 5.68 °, 8.49 °, and 11.25 °, it can be seen that the astigmatism is designed to be within 0.05 mm to be generally stable.

6 is a graph illustrating Ray Aberration characteristics of the optical system for a transmissive head mounted display according to an embodiment of the present invention. The light aberration of the optimized optical system is shown when the diameter of the exit pupil is 8 mm.

Light aberration refers to a phenomenon in which the refractive index is different according to the wavelength, that is, the aberration caused by dispersion, and when the image of the object is formed through the lens, the refractive index is changed according to the color emitted from the object, and thus the position and magnification of the image are different.

As shown in FIG. 6, it can be seen that the light aberration is designed to be within 9 μm and is generally stable. In addition, it can be seen that the light aberration according to the four wavelengths is also stable because there is no big difference.

7 is a block diagram of an optical system for a transmissive head mounted display according to another embodiment of the present invention.

Referring to FIG. 7, an optical system 100 for a transmissive HMD includes a display element 115, a polarizer 145, a half mirror 155, a phase retardation plate 165, and a total reflection curved mirror. mirror, 175). That is, the condensing lens 130 is removed from the optical system 100 for transmission type HMD described with reference to FIG. 2. Descriptions of the same or similar components as those described above may be referred to the corresponding parts, and thus description thereof is omitted here.

The operating principle of the transmission-type HMD optical system 100 according to another embodiment of the present invention is different in the following points.

First, the light constituting the image emitted from the display element 110 is changed to single polarized light through the polarizer 140. The polarized light is transmitted through the semi-transmissive mirror 150, and then goes straight to pass through the phase retardation plate 160 located in the forward direction, preferably, the λ / 4 phase retardation plate, to be changed into linearly or circularly-viewed light. Proceeds to the curved mirror 170. The polarized light is totally reflected back from the total reflection curved mirror 170 is returned to the half mirror (150) to be refracted by the window 10 to proceed to form an image in the human eye (20).

It is to be understood that the foregoing description of the disclosure is for the purpose of illustration and that those skilled in the art will readily appreciate that other embodiments may be readily devised without departing from the spirit or essential characteristics of the disclosure will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

It is to be understood that the scope of the present invention is defined by the appended claims rather than the foregoing description and that all changes or modifications derived from the meaning and scope of the claims and equivalents thereof are included in the scope of the present invention .

100: optical system for transmission type HMD 110, 115: display element
130: condenser lens 140, 145: polarizer
150, 155: transflective mirror 160, 165: phase delay plate
170, 175: total reflection curved mirror 180: adjustment means
190: stop means

Claims (8)

In an optical system for a transmissive head mounted display,
A display device that emits light constituting an image;
A polarizer positioned in front of the display element to selectively transmit the emitted light to the linearly-planned light to increase the amount of light;
A half mirror positioned in front of the light propagation direction of the polarizer to transmit a portion of the linearly-viewed light and reflect a portion thereof;
A total reflection curved mirror positioned in front of the light propagation direction of the transflective mirror to reflect all of the transmitted light; And
Transmissive head-mounted display comprising a phase delay plate located in front of the total reflection curved mirror to convert the totally reflected light to linearly polarized light, or to convert the totally reflected light into circularly polarized light; Optical system. The method of claim 1,
And the phase retardation plate is a λ / 4 phase retardation plate (QWP: Quater Wavelength Plate). The method of claim 1,
And a condenser lens positioned in front of the light traveling direction of the display element to collect the emitted light. The method of claim 3, wherein the condensing lens
An optical system for a transmissive head mounted display, characterized in that it consists of a combination of lenses selected from at least one spherical lens or at least one aspherical lens. The method of claim 1, wherein the total reflection curved mirror is
Optical system for a transmissive head-mounted display, characterized in that consisting of a spherical mirror or an aspheric mirror. The method of claim 1,
Adjusting means for adjusting the distance between both pupils; Transmissive head-mounted display optical system further comprising. The method of claim 1,
And a stop means for stopping image output of the display element. The method of claim 1, wherein the display element
Transmissive head mounted display, characterized in that it is a reflective liquid crystal on silicon (LCoS), digital light processing (DLP), a micro LCD device with a light source or a self-emitting micro OLED device Optical system.

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