CN117908253A - Distortion-free compact off-axis near-to-eye display optical system - Google Patents
Distortion-free compact off-axis near-to-eye display optical system Download PDFInfo
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- CN117908253A CN117908253A CN202311832146.8A CN202311832146A CN117908253A CN 117908253 A CN117908253 A CN 117908253A CN 202311832146 A CN202311832146 A CN 202311832146A CN 117908253 A CN117908253 A CN 117908253A
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- 230000003287 optical effect Effects 0.000 title claims abstract description 49
- 230000000007 visual effect Effects 0.000 claims description 2
- 238000012634 optical imaging Methods 0.000 abstract description 2
- 210000001747 pupil Anatomy 0.000 description 9
- 230000004075 alteration Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 230000003190 augmentative effect Effects 0.000 description 3
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Abstract
The invention relates to the technical field of optical imaging, in particular to a distortion-free compact off-axis near-to-eye display optical system, which comprises: the display, the first free-form surface element and the second free-form surface element, and the first sub-optical path and the second sub-optical path are formed by the first free-form surface element and the second free-form surface element; a first light inlet curved surface is arranged on one side of the top of the first free-form surface element, a light outlet curved surface is arranged below the light inlet curved surface, and a first reflecting curved surface and a second reflecting curved surface are sequentially arranged on one side of the first free-form surface element away from the first light inlet curved surface from top to bottom; a fitting curved surface matched with the second reflecting curved surface and a second light inlet curved surface far away from one side of the fitting curved surface are arranged on one side of the second free curved surface element; the display corresponds to the first light inlet curved surface. The invention has the characteristics of compact structure, small volume of optical parts and high definition.
Description
Technical Field
The invention relates to the technical field of optical imaging, in particular to a distortion-free compact off-axis near-to-eye display optical system.
Background
In recent years, with the development of virtual/augmented reality technology, related head mounted display devices have also grown endlessly. Because the head-mounted display device is worn on the head of a user, the device is required to be lightweight and compact. The augmented reality technology superimposes information of the virtual world and information of the real world together to be perceived by eyes of a user, so that a helmet display device is required to be capable of realizing a large angle of view and high definition, which puts high demands on the structure of an optical system. The existing optical modules for the augmented reality display system are mainly divided into coaxial refraction and reflection modes, holographic waveguides, geometric optical waveguides and the like. The display module based on coaxial refraction and reflection has high image definition, but is heavy, the angle of view is limited by the structure, and the light energy utilization rate is low. The optical module based on the holographic waveguide uses the principle of optical diffraction, and the structure can make the whole module light and thin, but color distortion caused by diffraction and the limitation of viewing angles caused by diffraction are problems.
Disclosure of Invention
The invention provides a distortion-free compact off-axis near-to-eye display optical system, which has the characteristics of compact structure, small volume of optical parts and high definition.
In order to achieve the above purpose, the present invention provides the following technical solutions: a distortion-free compact off-axis near-eye display optical system, comprising: the display, the first free-form surface element and the second free-form surface element, and the first sub-optical path and the second sub-optical path are formed by the first free-form surface element and the second free-form surface element; a first light inlet curved surface is arranged on one side of the top of the first free-form surface element, a light outlet curved surface is arranged below the light inlet curved surface, and a first reflecting curved surface and a second reflecting curved surface are sequentially arranged on one side of the first free-form surface element away from the first light inlet curved surface from top to bottom; a fitting curved surface matched with the second reflecting curved surface and a second light inlet curved surface far away from one side of the fitting curved surface are arranged on one side of the second free curved surface element; the display corresponds to the first light inlet curved surface.
Preferably, the first sub-optical path is: enters through the first light inlet curved surface, is reflected by the first reflecting curved surface, the light outlet curved surface and the second reflecting curved surface for three times in sequence, and is transmitted out through the light outlet curved surface again.
Preferably, the second sub-optical path is: enters through the second light inlet curved surface, and is transmitted out through the attaching curved surface, the second reflecting curved surface and the light outlet curved surface in sequence.
Preferably, the diagonal size of the display is in the range of 0.65 to 0.75 inch, the visual angle of the virtual image display light path is more than 45 degrees, and the distortion is less than 0.5%; the distance between the first reflecting curved surface and the light emergent curved surface is smaller than 11 mm.
Preferably, the second reflective curved surface is provided with a light splitting film, and the light splitting ratio is 1:1.
The invention has the beneficial effects that: the light is emitted by the light emitting surface of the display, passes through the protective glass plate covered on the display and then exits, then enters the first free-form surface element from the first light inlet curved surface, after being reflected by the first reflecting curved surface, the propagation direction is changed, the light reaches the light outlet curved surface for the first time, when the light passes through the light outlet curved surface for the first time, the light incidence angle meets the total internal reflection condition from the optically dense medium to the optically sparse medium, the total internal reflection occurs, then reaches the second reflecting curved surface, the surface is coated with the beam splitting film, the transmitted light continues to propagate forwards until the transmitted light disappears, the reflected light reaches the light outlet curved surface for the second time, at the moment, the light incidence angle does not meet the total reflection condition, the light can directly penetrate the light outlet curved surface, reaches the system exit pupil, and the image displayed on the display amplified by the optical system can be observed by human eyes; the system has compact structure, small volume of optical parts and high definition.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is an overall light path diagram of the present invention;
FIG. 2 is a schematic diagram of a virtual display light path and a perspective light path according to the present invention;
FIG. 3 is a schematic view of the overall optical path of the present invention;
FIG. 4 is a schematic view of a virtual image display light path according to the present invention;
FIG. 5 is a schematic view of the distortion of the virtual image display light path according to the present invention;
FIG. 6 is a schematic view of the surface numbering of the optical elements of the virtual image display light path of the present invention;
FIG. 7 is a schematic diagram of a perspective optical path distortion of the present invention;
Fig. 8 is a light path diagram of an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made more apparent and fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1,2 and 3, a distortion-free compact off-axis near-to-eye display optical system comprises: a display 13, a first free-form surface element 12, and a second free-form surface element 14, and a first sub-optical path and a second sub-optical path are formed by the first free-form surface element 12 and the second free-form surface element 14; a first light-entering curved surface 12d is arranged on one side of the top of the first freeform surface element 12, a light-exiting curved surface 12a is arranged below the light-entering curved surface 12d, and a first reflecting curved surface 12c and a second reflecting curved surface 12b are sequentially arranged on one side of the first freeform surface element 12 away from the first light-entering curved surface 12d from top to bottom; a fitting curved surface 14a matched with the second reflecting curved surface 12b and a second light inlet curved surface 14b far away from the fitting curved surface 14a are arranged on one side of the second free-form curved surface element 14; the display 13 corresponds to the first light-entering curved surface 12 d.
In the above arrangement, the first sub-optical path and the second sub-optical path exist in common optical components, namely, the first free-form surface element and the second free-form surface element. Wherein in the first sub-optical path, the human eye can observe an image displayed on the display enlarged by the optical system.
As shown in fig. 4, the virtual image display optical path in the present invention includes a display 13, a first free-form surface element 12, and an optical system exit pupil 11;
The light is emitted by a light emitting surface 13b of the display 13, passes through a protective glass plate covered on the display and then is emitted by 13a, then enters a first free-form surface element 12 through a first light inlet curved surface 12d, is reflected by a first reflecting curved surface 12c, changes the propagation direction and reaches a light outlet curved surface 12a for the first time, when the light passes through the light outlet curved surface 12a for the first time, the light incident angle meets the total internal reflection condition from an optically dense medium to an optically sparse medium, and is subjected to total internal reflection, then reaches a second reflecting curved surface 12b, the surface is plated with a beam splitting film, the transmitted light continues to propagate forwards until the transmitted light disappears, and the reflected light reaches the light outlet curved surface 12a for the second time, at the moment, the light incident angle does not meet the total reflection condition, the light can directly pass through the light outlet curved surface 12a and reaches a system exit pupil 11, and the image displayed on the display 13 amplified by an optical system can be observed by human eyes;
In order to achieve the purpose of light splitting, the second reflecting curved surface 12b needs to be coated with a light splitting film, and the preferred light splitting ratio is 1:1, i.e. when the light reaches the second reflective curved surface 12b, ideally 50% of the light is reflected and the remaining light is transmitted;
The diagonal size of the display 13 is 0.65-0.75 inches, and the screen ratio is 16:9, preferably, a Micro OLED display with high brightness and high resolution is adopted;
The system virtual display light path has a field angle larger than 45 degrees when observed from the system exit pupil position;
the distance from the system exit pupil 11 to the light-emitting curved surface 12a is 17 mm-20 mm when observed along the optical axis direction;
Wherein, the local coordinate system of the system exit pupil 11 is taken as a reference coordinate system, the eccentric range of the light emergent curved surface 12a of the first free curved surface element 12 along the Y direction is 2mm to 3mm, and the inclination angle range around the X axis is 0 DEG to 7 DEG; the second reflecting curved surface 12b has an eccentric range of-1 mm to 1mm in the Y-direction, an eccentric range of 22mm to 27mm in the Z-axis direction, and an inclination angle range of 20 DEG to 30 DEG around the X-axis; the first reflecting curved surface 12c has an eccentric range of 18mm to 23mm in the Y direction, an eccentric range of 23mm to 28mm in the Z axis direction, and an inclination angle range of 10 DEG to 17 DEG around the X axis; the first light-entering curved surface 12d has an eccentric range of 23mm to 27mm in the Y direction, an eccentric range of 16mm to 21mm in the Z axis direction, and an inclination angle range of-35 DEG to-25 DEG around the X axis; the surface 13a in the display 13 has an eccentric range of 23mm to 27mm in the Y-direction, an eccentric range of 16mm to 19mm in the Z-axis direction, and an inclination angle around the X-axis ranging from-33 ° to-23 °.
Wherein the system is an off-axis optical system, and in order to correct off-axis aberrations due to folding of the optical axis, certain surfaces in the element are described by free-form surfaces;
wherein, in order to achieve a high performance near-eye display system, the thickness of the system is constrained, wherein the thickness of the optical element is less than 11mm; in addition, the optical distortion of the system is required to be restrained, wherein the distortion of the virtual display light path is less than 0.5%;
the distortion of the virtual image display light path of the system is shown in figure 5; wherein, the virtual display light path uses only one optical element, which is designed by adopting low-dispersion materials for controlling the chromatic aberration of the system, and the Abbe number of the materials is at least more than 55.
The perspective light path in the present invention is shown in fig. 6. Wherein the first freeform surface element 12, the second freeform surface element 14, and the optical system exit pupil 11 are wrapped;
The light rays emitted/reflected by the object in the real scene pass through the second free-form surface element 14 and then pass through the first free-form surface element 12, finally reach the system exit pupil 11, and the human eyes can observe the real scene at the exit pupil; wherein the light rays, when passing through the first free-form surface element 12 and the second free-form surface element 14, correspond to a lens without optical power.
Wherein, since the light-emitting curved surface 12a is a free curved surface, in order to correct the off-axis aberration in the perspective direction, the second light-entering curved surface 14b of the second free curved surface element 14 is also described by a free curved surface, so as to obtain a good perspective imaging effect; wherein the conforming surface 14a and the second reflective surface 12b have the same shape, facilitating gluing the first and second freeform elements together; wherein the first free-form surface element 12 and the second free-form surface element 14 have the same optical material to ensure that the optical power in the perspective direction is uniform.
The distortion grid of the virtual image display light path is shown in fig. 7, the perspective distortion is less than 1.5%, and the distortion grid is not easily perceived by human eyes.
Embodiment one: the particular embodiments of the present invention will be described in detail with reference to the accompanying drawings, which may be embodied in many different forms and should not be construed as limited to the embodiments set forth below, but rather are provided so that the disclosure is thorough and complete, and will fully convey the concept of the invention to those skilled in the art.
The optical path of the first embodiment is shown in fig. 8. In order to correct the off-axis aberration of the system, the light-emitting curved surfaces 12a, 12b, 12c, 14b are free-form curved surfaces, and 12d is an aspheric surface.
Wherein the basic optical system parameters of the perspective light path are shown in table 1, the aspheric coefficients are shown in table 2, the free-form coefficients are shown in table 3, 12a is a multiplexing surface, and the light rays pass through the surface twice; the virtual display optical path and the perspective optical path share the light-exiting curved surface 12a.
Table 1 optical system parameters for virtual image display light path
Table 2 aspherical coefficients
TABLE 3 free form surface coefficients
Among the above surfaces, the surface constituting the aspherical surface satisfies the equation: the surface of the free-form surface is formed to satisfy the equation: /(I) C is the inverse of the radius of curvature, r is the radial distance of a point on the surface, k is the conic constant, and Ai is the higher-order term coefficient.
The basic optical system parameters of the perspective light path are shown in table 4, and the free-form surface coefficients are shown in table 5.
Table 4 optical system parameters for perspective display of optical paths
TABLE 5 free-form surface coefficient of perspective display light path
Among the above surfaces, the surface constituting the aspherical surface satisfies the equation: of the above surfaces, the surface constituted as a free-form surface satisfies the equation: /(I) C is the inverse of the radius of curvature, r is the radial distance of a point on the surface, k is the conic constant, and Ai is the higher-order term coefficient.
In this example, the display used a self-luminous display with a diagonal dimension of 0.71 inch, a system field angle of 45 °, a virtual image display optical path distortion of 0.4%, and a total thickness of the optical lens of 10.6mm.
The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any person skilled in the art will readily recognize that variations or substitutions are within the scope of the present invention. Therefore, the protection scope of the invention is subject to the protection scope of the claims.
Claims (5)
1.A distortion-free compact off-axis near-to-eye display optical system, comprising: the display, the first free-form surface element and the second free-form surface element, and the first sub-optical path and the second sub-optical path are formed by the first free-form surface element and the second free-form surface element;
A first light inlet curved surface is arranged on one side of the top of the first free-form surface element, a light outlet curved surface is arranged below the light inlet curved surface, and a first reflecting curved surface and a second reflecting curved surface are sequentially arranged on one side of the first free-form surface element away from the first light inlet curved surface from top to bottom;
a fitting curved surface matched with the second reflecting curved surface and a second light inlet curved surface far away from one side of the fitting curved surface are arranged on one side of the second free curved surface element;
The display corresponds to the first light inlet curved surface.
2. The distortion-free compact off-axis near-to-eye display optical system of claim 1, wherein the first sub-optical path is: enters through the first light inlet curved surface, is reflected by the first reflecting curved surface, the light outlet curved surface and the second reflecting curved surface for three times in sequence, and is transmitted out through the light outlet curved surface again.
3. The distortion-free compact off-axis near-to-eye display optical system of claim 1, wherein the second sub-optical path is: enters through the second light inlet curved surface, and is transmitted out through the attaching curved surface, the second reflecting curved surface and the light outlet curved surface in sequence.
4. A distortion-free compact off-axis near-eye display optical system as set forth in claim 1, wherein: the diagonal size of the display ranges from 0.65 to 0.75 inch, the visual angle of the virtual image display light path is larger than 45 degrees, and the distortion is smaller than 0.5%; the distance between the first reflecting curved surface and the light emergent curved surface is smaller than 11 mm.
5. A distortion-free compact off-axis near-eye display optical system as set forth in claim 1, wherein: the second reflecting curved surface is provided with a light splitting film, and the light splitting ratio is 1:1.
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| CN202311832146.8A CN117908253A (en) | 2023-12-28 | 2023-12-28 | Distortion-free compact off-axis near-to-eye display optical system |
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| CN202311832146.8A CN117908253A (en) | 2023-12-28 | 2023-12-28 | Distortion-free compact off-axis near-to-eye display optical system |
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001033729A (en) * | 1999-07-26 | 2001-02-09 | Olympus Optical Co Ltd | Observation optical system |
| CN101359089A (en) * | 2008-10-08 | 2009-02-04 | 北京理工大学 | Optical system of light and small-sized big angular field free curved surface prism helmet display |
| CN102402005A (en) * | 2011-12-06 | 2012-04-04 | 北京理工大学 | Bifocal-surface monocular stereo helmet-mounted display device with free-form surfaces |
| CN207081878U (en) * | 2017-05-26 | 2018-03-09 | 上海影创信息科技有限公司 | A kind of big visual field refraction-reflection type free form surface augmented reality optical system of big emergent pupil |
| CN116360106A (en) * | 2023-03-07 | 2023-06-30 | 北京耐德佳显示技术有限公司 | Free-form surface waveguide system and near-to-eye display device |
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- 2023-12-28 CN CN202311832146.8A patent/CN117908253A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001033729A (en) * | 1999-07-26 | 2001-02-09 | Olympus Optical Co Ltd | Observation optical system |
| CN101359089A (en) * | 2008-10-08 | 2009-02-04 | 北京理工大学 | Optical system of light and small-sized big angular field free curved surface prism helmet display |
| CN102402005A (en) * | 2011-12-06 | 2012-04-04 | 北京理工大学 | Bifocal-surface monocular stereo helmet-mounted display device with free-form surfaces |
| CN207081878U (en) * | 2017-05-26 | 2018-03-09 | 上海影创信息科技有限公司 | A kind of big visual field refraction-reflection type free form surface augmented reality optical system of big emergent pupil |
| CN116360106A (en) * | 2023-03-07 | 2023-06-30 | 北京耐德佳显示技术有限公司 | Free-form surface waveguide system and near-to-eye display device |
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