CN113985612A

CN113985612A - Off-axis optical module and head-mounted display equipment

Info

Publication number: CN113985612A
Application number: CN202111389972.0A
Authority: CN
Inventors: 程德文; 王达; 王涌天
Original assignee: Beijing Ned+ Ar Display Technology Co ltd
Current assignee: Beijing Ned+ Ar Display Technology Co ltd
Priority date: 2021-11-22
Filing date: 2021-11-22
Publication date: 2022-01-28

Abstract

The invention discloses an off-axis optical module, which comprises: a first lens group for receiving image light from the microdisplay in an off-axis manner; a first lens group including a plurality of lenses, the plurality of lenses in the first lens group being coaxially disposed; the first lens group further includes a first wedge prism; the first wedge prism is arranged close to an image source relative to the plurality of lenses in the first lens group; a second lens group for receiving the image light passing through the first lens group; a second lens group including a plurality of lenses, the plurality of lenses in the second lens group being coaxially disposed; the first lens group and the second lens group are arranged in an off-axis mode, and form a group of relay optical systems; and the curved mirror forms an intermediate image surface through the image light of the first lens group and the second lens group, and then the intermediate image surface is reflected by the curved mirror and enters human eyes. The invention also provides head-mounted display equipment comprising the off-axis optical module.

Description

Off-axis optical module and head-mounted display equipment

Technical Field

The invention relates to an off-axis optical module, and also relates to a head-mounted display device comprising the off-axis optical module.

Background

The main feature of the augmented reality technology is to superimpose virtual information on a real scene to realize the augmented reality. The augmented reality technology can fuse virtual information (such as objects, pictures, videos, sounds and the like) in a real environment, enrich the real world and construct a more comprehensive and better world. With the gradual entrance of wearable equipment into the career and life of people in recent years, the development of the intelligent glasses industry in particular makes the distance between people and the augmented reality technology step by step.

Currently, the augmented reality technology has been developed greatly on a helmet image display device. Some of these products use off-axis reflectance imaging techniques. In off-axis reflective imaging techniques, off-axis aberrations are typically corrected using a plurality of lenses positioned off-axis from each other. For example, off-axis large exit pupil distance smart AR glasses disclosed in utility model patent publication No. CN206594387U, and head mounted display devices disclosed in the invention patent application publication No. CN 107290857A. However, the off-axis reflector module uses a plurality of lenses disposed off-axis from each other, which increases the difficulty in designing and manufacturing the structure portion cooperating with the optical module, and on the other hand, only partial area of the partial lenses transmits light, resulting in waste of lenses.

In addition, in the optical design scheme of the existing off-axis reflective imaging technology, the inclination angle of the used curved surface reflector is generally small and generally within 30 degrees, so that the problem that the scheme is easy to interfere with other structures in a helmet display system is caused.

Disclosure of Invention

The invention provides an off-axis optical module.

Another objective of the present invention is to provide a head-mounted display device including the off-axis optical module.

In order to achieve the technical purpose, the invention adopts the following technical scheme:

an off-axis optical module comprising:

a first lens group for receiving image light from the microdisplay in an off-axis manner; a first lens group including a plurality of lenses, the plurality of lenses in the first lens group being coaxially disposed; the first lens group further includes a first wedge prism; the first wedge prism is arranged close to an image source relative to the plurality of lenses in the first lens group;

a second lens group for receiving the image light passing through the first lens group; a second lens group including a plurality of lenses, the plurality of lenses in the second lens group being coaxially disposed;

the first lens group and the second lens group are arranged in an off-axis mode, and form a group of relay optical systems;

and the curved mirror forms an intermediate image surface through the image light of the first lens group and the second lens group, and then the intermediate image surface is reflected by the curved mirror and enters human eyes.

Preferably, the included angle between the image source and the upper surface of the first wedge-shaped prism is controlled within 15 degrees;

the included angle between two planes of the first wedge-shaped prism is within 10 degrees;

the included angle between the Z axis of the first lens group and the Z axis of the second lens group is about 5 degrees.

Preferably, the plurality of lenses in the first lens group include at least one positive-negative double cemented lens and a convex lens with two aspheric surfaces.

Preferably, the second lens group further comprises a second wedge prism; and the second wedge-shaped prism is arranged at a position close to the curved mirror relative to the plurality of lenses in the second lens group.

Wherein the second wedge prism preferably has an included angle between two planes of less than 10 degrees.

Preferably, the plurality of lenses in the second lens group include at least one convex lens with aspheric surfaces, and a meniscus lens, and the meniscus lens is curved to the curved mirror side.

Preferably, the off-axis optical module further includes a reflector disposed between the second lens group and the curved mirror, for reflecting the image light transmitted through the second lens group to the surface of the curved mirror, wherein the reflector is a plane reflector or a curved reflector.

Preferably, the surface of the curved mirror is a free-form surface; the inclination angle of the curved mirror is more than 30 degrees and less than 40 degrees.

A head-mounted display device comprises the off-axis optical module.

Preferably, the first lens group and the second lens group are disposed above the curved mirror near the top of the head.

The off-axis optical module provided by the invention realizes larger magnification by adding at least one wedge-shaped prism and two lens groups arranged off-axis on the premise of not increasing the size of a micro-display screen. The exit pupil distance of the head-mounted display device is 75mm, the exit pupil diameter can reach 16mm, the field angle can reach more than 65 degrees, the curved mirror has a larger inclination angle, and the inclination angle can be more than 30 degrees and within 40 degrees, so that large-field-angle head-mounted display matched with a helmet is realized.

Drawings

FIG. 1 is a schematic structural diagram of a head-mounted display device provided in the present invention;

FIG. 2 is a schematic structural diagram of an off-axis optical module according to a first embodiment;

FIG. 3 is a schematic diagram of the number of different optical surfaces in each lens group in the off-axis optical module shown in FIG. 2;

FIG. 4 is a schematic structural diagram of an off-axis optical module according to a second embodiment;

FIG. 5 is a schematic diagram of different numbers of optical surfaces in each lens group in the off-axis optical module shown in FIG. 4.

Detailed Description

The technical solution of the present invention is further described in detail with reference to the accompanying drawings and specific embodiments.

As shown in fig. 1, the head-mounted display device provided by the present invention includes a housing, and an off-axis optical module disposed inside the housing. The off-axis optical module is arranged at the front side of the forehead, and the micro display in the off-axis optical module is arranged above the curved mirror and close to the top of the head. Hereinafter, a three-dimensional rectangular coordinate system is established with the human eye 50 as the origin of coordinates, the visual axis direction as the Z direction, the direction perpendicular to the visual axis direction as the Y direction, and the direction perpendicular to the YZ plane to the inner side of the paper surface as the X direction.

The off-axis optical module set in the head-mounted display device comprises a first lens group 20, a second lens group 30 and a curved mirror 40 which are sequentially arranged from an image source 100 to a human eye 50, wherein the curved mirror 40 can be a spectroscope or a total reflection mirror.

The image source 100 may be a micro display device such as LCD, OLED, Lcos, etc. Preferably, when a spectroscope is present in the optical system, the energy utilization rate of the system is generally not more than 60%, so Lcos or OLED display devices capable of greatly adjusting the display brightness are selected as the image source.

The first lens group 20 and the second lens group 30 constitute a group of relay optical systems, and the focal length is adjusted by the first lens group 20 and the second lens group 30, so that the magnification of the field angle is realized, and the off-axis aberration is corrected.

The image source 100, the first lens group 20 and the second lens group 30 are arranged in an off-axis manner, each lens in the first lens group 20 is arranged in a coaxial manner, and each lens in the second lens group 30 is arranged in a coaxial manner, so that off-axis aberration is corrected, and meanwhile, the assembly difficulty of each lens in the off-axis optical module is reduced.

The first lens group 20 and/or the second lens group 30 further include a wedge prism for compensating an optical path difference of light. Alternatively, a mirror is introduced between the second lens group 30 and the curved mirror 40, and a wedge prism and a mirror are used in combination to compensate for the optical path difference of the light.

The concave surface of the curved mirror 40 is disposed facing the human eye 50, and a light splitting film having a predetermined inverse transmittance ratio is attached to one side surface of the curved mirror 40. The specific deposition process of the spectroscopic film is not limited, and may be, for example, vapor deposition, ion sputtering, or pasting. Image light emitted from the image source 100 passes through the first lens group 20 and the second lens group 30 to form an intermediate image surface, and then is irradiated onto the curved mirror 40 and reflected into the human eye 50 via the curved mirror 40. It is understood that the ambient side light can also be projected into the human eye 50 via the curved mirror 40 to realize the augmented reality display.

The surface of the curved mirror 40 may be coated with a total reflection film. When a total reflection film is attached to the surface of the curved mirror 40, a virtual reality display effect can be realized.

The following description will be made of an off-axis optical module disposed in a housing, taking an augmented reality display as an example, in conjunction with specific embodiments.

First embodiment

In a first embodiment, the off-axis optical module is configured as shown in fig. 2, and includes an image source 1, a first wedge prism 2, a first lens 3, a positive-negative cemented lens 4, a second lens 5, a third lens 6, a fourth lens 7, a fifth lens 8, a second wedge prism 9, and a curved mirror 10.

The first wedge prism 2, the first lens 3, the positive-negative double cemented lens 4, and the second lens 5 form a first lens group 20. The mechanical axes (defined as a first axis A) of the first wedge prism 2, the first lens 3, the positive-negative double cemented lens 4 and the second lens 5 are coincident and coaxially arranged.

The first lens group 20 may be a group of coaxial spherical, cylindrical, aspherical, and free-form lenses. Preferably, in order to effectively correct the chromatic aberration of the system, the first lens group 20 includes a positive-negative cemented lens. Preferably, to correct higher order aberrations, a convex lens is selected that is aspherical on both surfaces. The focal length of the first lens group 20 is about 19.5 mm.

The first wedge prism 2 is disposed close to the image source 1 with respect to the other lenses in the first lens group 20. The first wedge prism 2 functions to compensate for the optical path difference of the off-axis system. Preferably, the first wedge prism 2 is placed coaxially with the surface of the other lens in contact for easy adjustment. Preferably, the surface of the first wedge prism 2 is a plane for convenience of processing. The included angle between the two planes of the first wedge prism is less than 10 degrees.

The third lens 6, the fourth lens 7, the fifth lens 8 and the second wedge prism 9 form a second lens group 30. The mechanical axes (defined as a second axis B) of the third lens 6, the fourth lens 7, the fifth lens 8 and the second wedge prism 9 are coincident and coaxially arranged.

The second lens group 30 may be a group of coaxial spherical, cylindrical, aspherical, and free-form lenses. Preferably, in order to correct the higher-order aberration, two surfaces of one convex lens are selected to be aspheric surfaces; preferably, in order to minimize spherical aberration, one piece of the lens is selected to be a meniscus lens, curved toward the curved mirror 10, i.e., the double-sided surface of the meniscus lens is convex toward the curved mirror 10 side. The focal length of the second lens group 30 is about 49.5 mm.

Wherein the second wedge prism 9 is disposed at a position close to the curved mirror 10 with respect to the other lenses in the second lens group 30. The second wedge prism 9 has the function of compensating the optical path difference of the off-axis system. Preferably, for ease of adjustment, the second wedge prism 9 is placed coaxially with the other lens-contacting surface; preferably, the surface of the second wedge prism 9 is flat for convenience of processing. The angle between the two planar surfaces of the second wedge prism 9 is less than 10 degrees.

The curved mirror 10 may be a spherical, cylindrical, aspherical, or free-form surface mirror. Preferably, the curved mirror 10 is a free-form surface, which is effective in correcting system aberrations.

An image signal sent by an image source 1 firstly passes through a first wedge-shaped prism 2, reaches a first lens 3, passes through a positive-negative double cemented lens 4, then passes through a second lens 5, and then passes through a third lens 6, a fourth lens 7, a fifth lens 8, a second wedge-shaped prism 9, and a curved mirror 10 to reflect the image signal, and finally the image signal reaches human eyes.

The positional relationship of the parts of this embodiment is shown in fig. 2. Wherein, the included angle theta 1 between the image source 1 and the upper surface of the first prism 2 is controlled within 15 degrees. The angle θ 2 between the two lens groups along the z-axis (i.e., the angle between the first axis a and the second axis B) is about 5 °. An included angle theta 3 between a connecting line of the local coordinate origin of the curved mirror 10 and the local coordinate origin of the lower surface of the second wedge prism 9 and the z-axis of the lower surface of the second wedge prism 9 is about 10 degrees. The angle between the normal of the curved mirror 10 and the visual axis is defined as the tilt angle θ 4 of the curved mirror 10, and the tilt angle θ 4 of the curved mirror 10 is about 36 °. The included angle a1 between the two planes of the first wedge prism 2 is within 10 DEG, and the included angle a2 between the two planes of the second wedge prism 9 is within 10 deg. The height d1 of the entire optical portion is about 188 mm. The inclination angle of the curved mirror is 36 degrees, the exit pupil distance is 75mm, the diameter of the exit pupil is 16mm, and the field angle is 67 degrees.

In the above embodiment, the parameters of the lenses and prisms used are as follows. The numbering of the various optical surfaces in the lenses and prisms can be seen in fig. 3. Wherein the parameters of each optical surface are shown in table 1. In the following table, only the design parameters of the optical surfaces of the optical elements are illustrated, it being understood that the optical elements may comprise other surfaces than the optical surfaces, which are not used as optical surfaces.

Referring to the data given in the table below, the curved mirror 10 of this embodiment is given a free-form surface, and the optical surfaces of the remaining lenses are spherical or aspherical.

TABLE 1 optical surface parameters of the first example

Serial number	Surface type	Radius of curvature	Thickness of	Refractive index	Abbe number	Eccentric center
								50	Spherical surface	Infinite number of elements	75
10	XY polynomial	-93.24	-103.13			Eccentricity and bending
							192	Spherical surface	Infinite number of elements	-3.78	1.517	6.42	Basic eccentricity
191	Spherical surface	Infinite number of elements	-0.87			Basic eccentricity
							182	Spherical surface	-27.46	-4.6	1.911	35.2
181	Spherical surface	-52.8	-2.49
							172	Spherical surface	-130.60	-1.5	1.739	23.0
171	Spherical surface	-33.61	-1.16
							162	Aspherical surface	-29.69	-5.35	1.569	67.9
161	Aspherical surface	364.85	-4.88
							152	Aspherical surface	-29.42	-5.5	1.594	67.3	Basic eccentricity
151	Aspherical surface	225.51	-2.80
							143	Spherical surface	-166.17	-2.0	1.915	18.4
142	Spherical surface	-27.37	-6.15	1.871	37.7
							141	Spherical surface	Infinite number of elements	-2.0
132	Spherical surface	-47.21	-6.0	1.848	39.4
							131	Spherical surface	125.81	-0.59
122	Spherical surface	Infinite number of elements	-6.04	1.654	29.3
							121	Spherical surface	Infinite number of elements	-3.5			Basic eccentricity
1	Spherical surface	Infinite number of elements				Basic eccentricity

Second embodiment

As shown in fig. 4, the off-axis optical module includes an image source 1, a first wedge prism 2, a first lens 3, a positive-negative double cemented lens 4, a second lens 5, a third lens 6, a fourth lens 7, a fifth lens 8, a reflector 11, and a curved mirror 10.

The first lens group 20 may be a group of coaxial spherical, cylindrical, aspherical, and free-form lenses. Preferably, in order to effectively correct the chromatic aberration of the system, the first lens group 20 includes a positive-negative cemented lens. Preferably, to correct higher order aberrations, a convex lens is selected that is aspherical on both surfaces.

The first wedge prism 2 is disposed at a position close to the image source 1. The first wedge prism 2 functions to compensate for the optical path difference of the off-axis system. Preferably, the first wedge prism 2 is placed coaxially with the surface of the other lens in contact for easy adjustment. Preferably, the surface of the first wedge prism 2 is a plane for convenience of processing.

The third lens 6, the fourth lens 7 and the fifth lens 8 constitute a second lens group 30. The mechanical axes (defined as a second axis B) of the third lens 6, the fourth lens 7, and the fifth lens 8 are coincident and coaxially arranged.

The second lens group 30 may be a group of coaxial spherical, cylindrical, aspherical, and free-form lenses. Preferably, in order to correct higher order aberrations, a convex lens with aspheric surfaces on both surfaces is selected; preferably, to minimize spherical aberration, one lens is selected to be a meniscus lens.

In this embodiment, a reflecting mirror 11 is disposed between the second lens group 30 and the curved mirror 10. By providing the reflecting mirror 11, the image source 1, the first lens group 20, and the second lens group 30 can be pushed to a position farther from the top of the head, thereby adapting to the structural design of the head-mounted display device.

The reflecting mirror 11 may be a plane mirror, a spherical mirror, an aspherical mirror, or a free-form surface mirror. Preferably, in the illustrated embodiment, a plane mirror is used to change the optical path, so as to avoid interference between the optical system and other structures of the helmet, and simultaneously, the optical path difference between the optical paths with different fields of view can be changed, thereby achieving the purpose of reducing the use of one prism.

An image signal sent by an image source 1 firstly passes through a first wedge prism 2, reaches a first lens 3, passes through a positive-negative double cemented lens 4, then passes through a second lens 5, then passes through a third lens 6, a fourth lens 7 and a fifth lens 8, and reaches a reflector 11, the reflector 11 reflects the image signal to a curved mirror 10, the curved mirror 10 reflects the image signal, and finally the image signal reaches human eyes.

Wherein, the included angle theta 1 between the image source 1 and the optical axis of the upper surface of the first wedge prism 2 is within 10 degrees. The included angle theta 2 of the mechanical axes between the two lens groups is about 2 degrees. An included angle theta 3 between a connecting line of the local coordinate origin of the fifth lens 8 and the local coordinate origin of the plane reflecting mirror 11 and the z-axis of the plane reflecting mirror 11 is about 10 degrees. An angle θ 5 between a line connecting the local origin of coordinates of the plane mirror 11 and the local origin of coordinates of the curved mirror 10 and the z-axis of the plane mirror 11 is about 56 °. The inclination angle θ 4 of the curved mirror 10 is about 36 °. The included angle a1 between the two planes of the first wedge prism 2 is within 10 °. The height d1 of the entire optical portion is about 188 mm.

In the above embodiment, the parameters of the lenses and prisms used are as follows. The numbering of the various optical surfaces in the lenses and prisms can be seen in fig. 5. Wherein the parameters of each optical surface are shown in table 2. In the following table, only the design parameters of the optical surfaces of the optical elements are illustrated, it being understood that the optical elements may comprise other surfaces than the optical surfaces, which are not used as optical surfaces.

TABLE 2 optical surface parameters of the second example

Serial number	Surface type	Radius of curvature	Thickness of	Refractive index	Abbe number	Eccentric center
								50	Spherical surface	Infinite number of elements	75
10	XY polynomial	-139.21	-84.98			Eccentricity and bending
							11	Spherical surface	Infinite number of elements	30.58			Eccentricity and bending
282	Spherical surface	27.85	5	1.919	28.5	Basic eccentricity
							281	Spherical surface	51.45	5.05
272	Spherical surface	575.13	1.5	1.896	18.8
							271	Spherical surface	36.56	0.27
262	Aspherical surface	29.16	5.5	1.708	56.0
							261	Aspherical surface	486.53	3.51
252	Aspherical surface	31.49	5.5	1.671	47.2	Basic eccentricity
							251	Aspherical surface	-128.63	3.57
243	Spherical surface	86.16	1.5	1.849	19.7
							242	Spherical surface	19.91	8	1.911	35.3
241	Spherical surface	-2794.9	1.61
							232	Spherical surface	43.54	6	1.729	54.7
231	Spherical surface	-92.02	0.93
							222	Spherical surface	Infinite number of elements	4	1.517	64.2
221	Spherical surface	Infinite number of elements	3.09			Basic eccentricity
							1	Spherical surface	Infinite number of elements	0.19			Basic eccentricity

In summary, the off-axis optical module and the head-mounted display device provided by the invention realize a larger magnification by adding at least one wedge prism and two groups of off-axis lenses on the premise of not increasing the size of the microdisplay screen, the exit pupil distance of the head-mounted display device is 75mm, the exit pupil diameter can reach 16mm, and the field angle can reach more than 65 °. In addition, in the optical module, the curved mirror has a larger inclination angle which can be more than 30 degrees and less than 40 degrees, and large-field-angle head-mounted display matched with a helmet is realized. In addition, in the off-axis optical module, a plane reflector or a curved reflector can be added to change the overall structure of the optical system and play a role in making up part of optical path difference and correcting aberration. By adopting the scheme, the trend of the light path can make full use of the lens, and better imaging quality and larger field angle can be obtained.

The off-axis optical module and the head-mounted display device provided by the invention are described in detail above. It will be apparent to those skilled in the art that any obvious modifications thereof can be made without departing from the spirit of the invention, which infringes the patent right of the invention and bears the corresponding legal responsibility.

Claims

1. An off-axis optical module, comprising:

2. The off-axis optical module of claim 1 wherein:

the included angle between the image source and the upper surface of the first wedge-shaped prism is controlled within 15 degrees;

3. The off-axis optical module of claim 1 wherein:

the plurality of lenses in the first lens group at least comprise a positive-negative double cemented lens and a convex lens with two aspheric surfaces.

4. The off-axis optical module of claim 1 wherein:

the second lens group further includes a second wedge prism; and the second wedge-shaped prism is arranged at a position close to the curved mirror relative to the plurality of lenses in the second lens group.

5. The off-axis optical module of claim 1 wherein:

the included angle between two planes of the second wedge-shaped prism is within 10 degrees.

6. The off-axis optical module of claim 1 or 4, wherein:

the plurality of lenses in the second lens group at least comprise a convex lens with two aspheric surfaces and a meniscus lens, and the meniscus lens is bent to the side of the curved mirror.

7. The off-axis optical module of claim 1 wherein:

the lens system further comprises a reflecting mirror arranged between the second lens group and the curved mirror and used for reflecting the image light transmitted through the second lens group to the surface of the curved mirror, wherein the reflecting mirror is a plane reflecting mirror or a curved reflecting mirror.

8. The off-axis optical module of claim 1 wherein:

the surface of the curved mirror is a free curved surface; the inclination angle of the curved mirror is more than 30 degrees and less than 40 degrees.

9. A head-mounted display device, characterized in that: comprising an off-axis optical module according to any of claims 1 to 8.

10. The head-mounted display device of claim 9, wherein: the first lens group and the second lens group are arranged above the curved mirror and close to the top of the head.