KR20080082068A - Optical system of head mounted display - Google Patents

Abstract

An optical system of a head mounted display is provided to minimize optical aberration such as chromatic and spherical aberration by installing a display element, a hybrid lens, and an eyepiece. An optical system of a head mounted display includes a display unit(30), a hybrid lens(31), and an eyepiece(32). The hybrid lens disposed along the axis of image beams generated from the display unit guides the image beams to the eyepiece by refracting the image beams from the display unit. The eyepiece provided in front of the hybrid lens focuses the image beams from the hybrid lens to eyes of users. The eyepiece includes a glass lens with rotationally symmetric spherical input and output surfaces, and a plastic portion with a rotationally symmetric non-spherical surface in contact with the glass lens. Input and output surfaces of the eyepiece are implemented with a rotationally symmetric spherical surface.

Description

OPTICAL SYSTEM OF HEAD MOUNTED DISPLAY}

1 is a configuration diagram schematically showing an example of a conventional optical system for a head mounted display,

2 is a schematic view showing another example of a conventional optical system for a head mounted display,

3 is a plan view schematically showing a first embodiment of an optical system for a head mounted display according to the present invention;

4 is a cross-sectional view showing an embodiment in which a 45 degree reflector is further installed in front of the eyepiece according to the present invention;

5 is a schematic view showing the form of a hybrid lens according to the first embodiment of the present invention,

6 is a plan view schematically showing a second embodiment of an optical system of a headmount display according to the present invention;

7 is a schematic diagram showing the form of a hybrid lens according to a second embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

30 display element 31 hybrid lens

311 glass entrance surface 312 glass exit surface

313: plastic coating exit surface 32: eyepiece

The present invention relates to an optical system for a head mounted display (HMD), and more particularly, it is possible to simultaneously correct spherical aberration and chromatic aberration, thereby minimizing optical aberration, and reducing the number of lenses to reduce manufacturing costs. An optical system of a lighter, more compact and lightweight headmount display.

In general, the head mounted display device focuses the image light generated by the ultra-small display device of 1 inch or less by forming a virtual large screen at a distance using a transmission optical system or a reflection optical system using light refraction. It is an image display device that allows a user to view an enlarged virtual image.

In such an optical system of the head mounted display, since the display element is located at the ultra-short distance of the eye and needs to magnify the image at a high magnification, a high performance optical system is required, and a plurality of glass lenses having a large refractive index are required. When two or more glass lenses are used in order to obtain high magnification at a short distance, chromatic aberration inevitably occurs due to the difference in wavelength of light passing through the lens. In order to compensate for the difference in wavelength of light by appropriately using a mixture of high and low refractive glass materials, a method having at least one aspherical curved surface having two or more spherical curvatures is used. .

FIG. 1 shows an example of an optical system of a head mounted display using a high refractive glass lens and a low refractive glass lens called a Ploessl Eyepiece according to the prior art.

The pleated eyepiece shown in FIG. 1 includes a display element 2 for providing an image, a first optical member D1 composed of a combination of a high refractive glass lens 5 and a low refractive glass lens 6, and The second optical member D2 is formed of a combination of the refractive glass lens 7 and the high refractive glass lens 8, and the image light generated by the display element 2 by the above configuration is 2 After being incident through the high refractive glass lens 8 of the optical member D2 and exiting through the low refractive glass lens 7, the low refractive glass lens 6 of the first optical member D1 is again present. When the light is incident through the high refractive glass lens 5 and is emitted through the high refractive glass lens 5, the image is formed at the position of the eyeball 1 of the user, and the user can secure the viewing angle 3 and view the enlarged image of the display element 2. .

However, the optical system method of the head mounted display which uses the high refractive glass lens and the low refractive glass lens of the prior art having the above-described structure is combined with the high refractive glass lens and the low refractive lens even though the optical lens system is composed of one optical member. As the low refractive glass lenses must be separately processed, manufacturing costs increase, and there is a technical difficulty to accurately match the optical axis when combining the high refractive glass lens and the low refractive glass lens, and the number of optical elements necessary for the correction of chromatic aberration is necessary. Since it is difficult to reduce the volume and weight will have to be large, there was a problem that can give a great inconvenience to the user.

In view of the problems of the conventional optical system for a head mounted display, an optical system of a head mounted display employing a free curved prism as shown in FIG. 2 as an optical member has been proposed. 11) and an optical system comprising a rotationally asymmetric free-curve prism lens 12 having all of an entrance face 121, a first reflection face 122, a second reflection face 123, and an exit face 122. The image light generated by the display element 11 by the above configuration is incident on the free-curved prism through the incident surface 121, and then reaches the first reflective surface 122 at an angle smaller than a critical angle. Totally reflected at the first reflective surface 122 and reflected from the second reflective surface 123 which is again coated with a reflective coating and then shares a surface with the first reflective surface 122. The prism lens exits through the exit surface 122 and is imaged on both eyes 13 of the user.

However, the optical system using the free-form prism lens of the prior art having the above-described configuration enables the construction of a simple light path due to the characteristics of the free-curved prism lens that can adjust the light direction within a certain range, thereby greatly reducing the thickness of the HMD. Although it is possible to have a wide field of view (FOV) and to secure a wide field of view (FOV), in order to reduce distortion due to eccentric error, at least one free surface of rotation asymmetry is provided in the prism lens. Compared with this, the processing of the optical parts is very difficult, which may cause the product cost to rise, and since two of the three surfaces of the free-curved prism lens are reflective surfaces, the direction of the image light even when the contact angles of the three surfaces are slightly distorted during processing. Can have a big impact on the quality of the product or mold Density is required, but all three surfaces are curved, making reference points very difficult. In addition, the first reflective surface, which is a free surface of rotational asymmetry, has different curvature changes with respect to the X, Y, and Z axes, so it is very difficult to find the intersection of the rotational asymmetry and other surfaces during machining, and it is difficult to manufacture properly according to the design. Unlike the rotationally symmetrical surface, which can be inspected with only the curvature data of one line passing through the center point, the entire surface must be scanned and finely divided by all the coordinates. It is difficult to identify and calibrate the product, and there is a risk of going through a lot of cost and trial and error until the production of the product.

Accordingly, the present invention has been made to solve the conventional problems as described above, the object is to adopt a hybrid lens to correct spherical aberration and chromatic aberration at the same time, while minimizing optical aberration, easy processing and performance inspection The objective is to provide an optical system for a head mounted display with minimal product development costs.

In addition, another object of the present invention is to reduce the number of lenses by applying a hybrid lens to the optical system of the head mounted display to significantly reduce the manufacturing cost and to provide a more compact and lightweight head mounted display.

In order to achieve the above object, an optical system of a head mounted display according to the invention comprises: a display element; A hybrid lens disposed at a predetermined distance along an optical axis of the image light generated by the display element and refracting the image light projected by the display element to guide the adjacent eyepiece 32 to be installed; And an eyepiece disposed in front of the hybrid lens and focusing the image light emitted from the hybrid lens on an eyeball of the user, wherein the hybrid lens has an incident surface on which the image light is incident and an exit surface on which the image light is emitted. All of them are made of a glass lens consisting of a spherical surface of rotation symmetry, and a plastic molded part having a shape of a rotationally symmetric aspheric surface attached to one surface of the glass lens and in contact with the outside air, and the entrance and exit surfaces of the eyepiece Are all characterized by consisting of a rotationally symmetrical spherical surface.

It is preferable to further arrange a planar reflective surface 33 having a 45 ° inclination on the optical path between the display element 30 and the hybrid lens 31.

Another aspect of an optical system of a head mounted display according to the invention for achieving the above object is a display element; A spherical lens disposed to be spaced apart a predetermined distance along an optical axis of the image light generated by the display element, the spherical lens refracting the image light projected by the display element to be guided to the adjacent hybrid eyepiece 32; And a hybrid eyepiece disposed in front of the spherical lens and focusing the image light emitted from the spherical lens on the eyeball of the user. The incident surface and the exit surface of the spherical lens are both spherical surfaces of rotational symmetry. The hybrid eyepiece includes a glass lens having both an incident surface into which image light is incident and an exit surface from which image light is emitted, and a surface attached to one surface of the glass lens to be in contact with outside air. It is characterized by consisting of a plastic molded part having a symmetric aspherical surface.

It is preferable to further arrange a planar reflective surface 33 having a 45 ° inclination on the optical path between the display element 30 and the spherical lens 31.

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

3 is a diagram schematically showing an embodiment of the configuration and arrangement of the head mounted display optical system according to the present invention.

As shown in FIG. 3, the optical system of the head mounted display according to the present invention includes a display element 30, a hybrid lens 31, and an eyepiece 32, which are image display devices for emitting image light.

The hybrid lens 31 is arranged to be spaced apart a predetermined distance along the optical axis of the image light generated by the display element, to be guided to the eyepiece 32 is installed by refracting the image light projected from the display element, It consists of a spherical glass lens and a plastic molded part attached to one surface of the glass lens.

The glass lens has both an incident surface into which image light is incident and an exit surface from which image light is emitted, and a spherical surface having rotational symmetry. It is molded on one surface of the glass lens to have an aspherical surface.

Therefore, in the hybrid lens including the glass lens and the plastic molding as described above, the color separation phenomenon caused by the difference in the wavelength of each component of the light within the glass lens due to the high refractive image light passing through the glass lens is generated in the plastic molding portion. Chromatic aberration is compensated for by using the property of relative negative power, and as shown in the lens of FIG. 1, a large number of optical elements such as a high refractive glass lens and a low refractive glass lens are not required to correct the chromatic aberration. It is remarkably reduced, and in view of the processing surface, both the glass lens consisting of the rotationally symmetrical spherical surface and the plastic molding part having the rotationally symmetric aspherical surface can be easily processed or molded, so that the hybrid lens as a whole can be easily processed. In the same lens as in FIG. Likewise, when the high refractive glass lens and the low refractive glass lens are combined, the optical axis does not need to be exactly matched. Also, as in the prism lens as shown in FIG. have.

The hybrid lens 31 has at least one of the entrance and exit surfaces of the image light projected by the display element formed of a plastic surface. As a specific example, as shown in FIG. Position the glass lens on the incident surface, position the plastic molding on the exit surface, or position the plastic molding on the incident surface of the image light generated by the display element as shown in FIG. May be positioned so that it is located toward the exit surface.

The eyepiece 32 is intended to form an image light transmitted through the hybrid lens 31 to the eyeball of the user, so that both the incident surface and the exit surface of the image light can be made as a spherical surface is very easy to process. Done.

According to the optical system of the head mounted display according to the present invention having the above configuration, the image light generated from the display element 30 representing the image is highly refracted through the incident surface 311 of the glass sphere of the hybrid lens 31. After entering the plastic molding part through the exit surface 312 of the spherical surface of the glass lens, and after being subjected to various aberration compensation processes, the eyepiece 32 is led through the exit surface 313 by the eyepiece 32. It is effectively imaged on the eyes of the user, the volume and weight is significantly reduced compared to the conventional optical system of the head mounted display as shown in FIG. 1, and the processing is very much compared to the optical system of the head mounted display as shown in FIGS. It becomes easy.

FIG. 5 is a configuration in which a flat reflective surface 33 having a 45 ° inclination is further disposed on an optical path between the display element 30 and the hybrid lens 31, and the 45 ° reflector 33 is disposed on the display element 30. ) And the optical path between the hybrid lens 31 can reduce the volume of the overall optical system while reducing the length of the optical path between the display element 30 and the hybrid lens 31 before the placement of the reflector. Since the system can be the same as the system, the optical system can be made more compact.

Figure 6 is a schematic representation of yet another embodiment of a headmount display optical system in accordance with the present invention.

As shown in FIG. 6, the optical system of the head mounted display according to the embodiment includes a display element 60, a spherical lens 61, and a hybrid eyepiece 62.

As compared with the optical system of the head mounted display shown in FIG. 3, the optical system of the head mounted display as shown in FIG. 6 forms an eyepiece contacting the eyeball of the user with a hybrid lens, and the lens located on the display element side. There is a difference in that they are simply placed as spherical lenses.

In the optical system of the head mounted display having the above-described configuration, the image light generated by the display element 30 representing the image passes through the spherical lens 61 and is guided to the hybrid eyepiece 62, and then the hybrid eyepiece 62. When the light enters through the plastic aspherical surface 621, the glass sphere of the hybrid eyepiece 62 passes through the spherical lens 61 and undergoes a compensation process for various aberrations. Passing through the surface 622 and the exit surface 623 is effectively imaged on the user's eye.

In the hybrid eyepiece 31, at least one of an entrance surface and an exit surface of the image light projected from the display element through the spherical lens is formed of a plastic surface, and as a specific example, in FIG. As shown, the plastic molding is positioned on the incident surface of the image light emitted from the spherical lens, and the glass lens is positioned on the emission surface side, or the incident surface of the image light emitted from the spherical lens as shown in FIG. The glass lens may be positioned at the position, and the plastic molding may be disposed at the exit surface side.

Embodiments according to the above description can be variously changed and modified without departing from the spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the examples, but should be defined by the claims.

The optical system of the head mounted display according to the present invention has an optical aberration such as spherical aberration and chromatic aberration by the configuration of the display element 30, the hybrid lens 31 and the eyepiece 32, which are image display devices that emit image light. It is easy to process and minimizes the volume and weight.

Claims (4)

Display elements; A hybrid lens disposed to be spaced apart a predetermined distance along an optical axis of the image light generated by the display element, and to refract the image light projected by the display element to guide the adjacent eyepiece; And An eyepiece disposed in front of the hybrid lens and focusing the image light emitted from the hybrid lens on an eye of a user; The hybrid lens includes a glass lens having both an incident surface into which image light is incident and an exit surface from which image light is emitted, and a surface that is attached to one surface of the glass lens and is in contact with external air. It is made of a plastic molding having a shape, And an entrance surface and an exit surface of the eyepiece are both rotationally symmetrical spherical surfaces. The optical system of claim 1, further comprising a planar reflecting surface having an inclination of 45 DEG on an optical path between the display element and the hybrid lens. Display elements; A spherical lens disposed at a predetermined distance apart from the optical axis of the image light generated by the display element and refracting the image light projected by the display element to be guided to a hybrid eyepiece installed adjacent thereto; And And a hybrid eyepiece disposed in front of the spherical lens and focusing the image light emitted from the spherical lens on the eyeball of the user. Both the entrance surface and the exit surface of the spherical lens is made of a spherical surface of rotation symmetry, The hybrid eyepiece includes a glass lens having both an incident surface into which image light is incident and an exit surface from which image light is emitted, and a surface that is attached to one surface of the glass lens and in contact with outside air. An optical system for a head mounted display, characterized in that it consists of a plastic molded part having an aspherical surface. The optical system of claim 1, further comprising a planar reflecting surface having a 45 degree inclination on an optical path between the display element and the spherical lens.

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