Dual-channel display optical system and AR device

Abstract

The invention discloses a dual-channel display optical system and AR equipment. The dual-channel display optical system comprises a projection module, a light-emitting element, a first lens module and a second lens module, the projection module comprises a free-form surface prism, a compensation prism and a display; the compensation prism is arranged on one side of the free-form surface prism, the first lens module is arranged at one end of the free-form surface prism, and the displayer, the light-emitting element and the second lens module are all arranged at the other end of the free-form surface prism. Compared with the prior art, the projection path of the single prism is realized, the imaging chromatic aberration is corrected, the imaging quality is improved, the complexity of a light path is effectively reduced, the size and the weight of the AR equipment are effectively reduced, and the use experience of the AR equipment is improved.

Description

Technical Field

[0001] The present invention relates to the field of projection display technology, and in particular to an optical system and AR equipment for dual-channel display. Background Art

[0002] With the rapid development of optical technology, users have higher and higher requirements for the functions, size and weight of AR devices. The reasons that affect the user experience of AR devices mainly involve the optical system in AR devices. The optical system of existing AR devices usually adopts optical display technologies such as bi rdbath, optical waveguide or free-form surface. Existing AR devices have the problems of high optical path complexity, low light energy utilization, relatively large size and weight, and relatively high assembly difficulty.

[0003] In view of this, it is necessary to provide an optical system and AR device with dual-channel display to solve the above problems. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides an optical system and an AR device with a dual-channel display, which can effectively solve the problems of relatively high optical path complexity of the AR device, high light loss rate, relatively high volume and weight of the AR device, and relatively high assembly difficulty.

[0005] To achieve the above-mentioned objectives, a first aspect of the present invention provides an optical system for dual-channel display, which includes a projection module, a light-emitting element, a first lens module and a second lens module; the projection module includes a free-form surface prism, a compensation prism and a display; the compensation prism is arranged on one side of the free-form surface prism, the first lens module is arranged at one end of the free-form surface prism, and the display, the light-emitting element and the second lens module are all arranged at the other end of the free-form surface prism.

[0006] In a preferred embodiment, the free-form surface prism includes a first curved surface, a second curved surface and a third curved surface; the first curved surface is far away from the compensation prism, the second curved surface is close to the compensation prism, a semi-transparent and semi-reflective film is attached to the second curved surface, and the third curved surface faces the display and the light-emitting element.

[0007] In a preferred embodiment, a diffraction element is attached to the first curved surface.

[0008] In a preferred embodiment, the angular resolution of the display is θ, the angular resolution of the human eye is δ, and the following condition is satisfied: δ<θ<2δ.

[0009] In a preferred embodiment, the horizontal viewing angle of the display is w, the vertical viewing angle of the display is v, and they satisfy: 20.19° <w<40.38°,15.21°<v<30.42°。

[0010] In a preferred embodiment, the first lens module includes a first lens, a first aperture, a second lens, a third lens, a protective sheet and a first image plane which are arranged in sequence.

[0011] In a preferred embodiment, the first lens, the second lens and the third lens are all plastic aspherical lenses.

[0012] In a preferred embodiment, the second lens module includes a fourth lens, a fifth lens, a sixth lens, a second aperture, a doublet lens and a second image plane which are arranged in sequence.

[0013] In a preferred embodiment, the fourth lens and the fifth lens are both negative power lenses, and the sixth lens and the doublet lens are both positive power lenses.

[0014] A second aspect of the present invention provides an AR device, comprising the optical system for dual-channel display in any one of the aforementioned items.

[0015] The beneficial effects of the present invention are as follows: a projection module composed of a single free-form surface prism and a compensation prism is further provided with a first lens module and a second lens module to assist the projection module, so that the projection path of a single prism can be realized, the light loss rate can be reduced, and chromatic aberration can be corrected, which can effectively reduce the optical path complexity of the optical system, and at the same time reduce the volume and weight of the optical path system, thereby reducing the volume and weight of the AR device, and thereby improving the user experience of the AR device. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of the structure of an optical system for dual-channel display provided by an embodiment of the present invention;

[0017] Figure 2 A schematic diagram of the structure of a projection module provided by an embodiment of the present invention;

[0018] Figure 3 The MTF curve diagram of the projection module provided by the embodiment of the present invention;

[0019] Figure 4 A comparison diagram of distortion curves of a projection module provided by an embodiment of the present invention;

[0020] Figure 5 A comparison diagram of vertical axis chromatic aberration of a free-form surface prism provided in an embodiment of the present invention;

[0021] Figure 6 A comparison diagram of the color focus shift curves of the free-form surface prism provided by the embodiment of the present invention;

[0022] Figure 7 A schematic structural diagram of a first lens module provided in an embodiment of the present invention;

[0023] Figure 8A point diagram of a first lens module provided by an embodiment of the present invention;

[0024] Fig. 9 An MTF curve diagram of the first lens module provided by an embodiment of the present invention;

[0025] Fig.10 A schematic diagram of the structure of a second lens module provided by an embodiment of the present invention;

[0026] Fig.11 A point diagram of a second lens module provided by an embodiment of the present invention;

[0027] Fig.12 This is an MTF curve diagram of the second lens module provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In the present invention, the terms "disposed", "provided with" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements or components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, "plurality" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0030] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those skilled in the art, the specific meanings of these terms in the present invention can be understood according to specific circumstances.

[0031] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0032] Please refer to Figure 1 and Figure 2 In this embodiment, the optical system of dual-channel display includes a projection module 1, a light emitting element 2, a first lens module 3 and a second lens module 4; the projection module 1 includes a free-form surface prism 11, a compensation prism 12 and a display 13.

[0033] The free-form surface prism 11 is used to project the light emitted by the display 13 onto the user's pupil, and the compensation prism 12 is used to compensate for the distortion of the light. The first lens module 3 is used to realize the iris tracking function, the second lens module 4 is used to capture the real scene, and the light-emitting element 2 is used to emit infrared rays to assist in realizing the iris tracking function. Specifically, the compensation prism 12 is arranged on one side of the free-form surface prism 11, the first lens module 3 is arranged at one end of the free-form surface prism 11, and the display 13, the light-emitting element 2 and the second lens module 4 are all arranged at the other end of the free-form surface prism 11.

[0034] Specifically, in a preferred embodiment, some parameters of some components of the optical system of dual-channel display are as follows: based on the user's eyelashes and eyelids and the situation of myopic users, and combined with the existence of a bevel in the free-form surface prism 11, the effective exit pupil distance is the distance between the bevel and the human eye, and the effective exit pupil distance needs to be at least 20mm. Preferably, the effective exit pupil distance is 23mm. In order to avoid the loss of field of view and fatigue of users when using AR devices, the exit pupil diameter of the optical system is set to 8mm. The resolution of the display 13 is 1200x900, the pixel size is 15um, the display range of the display 13 is 18.75mmx13.5mm, and the aspect ratio is 4:3.

[0035] Based on the structure of the free-form prism 11, the eye distance of the display 13 can be taken as 30 mm, the distance from its lower edge to the center of the pupil can be taken as 9.54 mm, and the distance from the corner of the human eye to the center of the pupil can be taken as 15 mm. It can be determined that the working distance of the first lens module 3 is 31.48 mm and the half field of view angle is 25.48°.

[0036] Because the iris has a high reflectivity and the pupil has a high absorption rate under the illumination of a light source in the near-infrared band, the pupil is darker and the boundary between the two is more obvious, so the recognition accuracy of the pupil center is significantly improved. The light-emitting element 2 is designed with an infrared light source with a main wavelength of 850nm, and its spectrum range is 832nm to 872nm. Since the maximum field of view of a single human eye is about 150°, the field of view of the second lens module 4 can be defined as 150°, and the working wavelength is visible light.

[0037] The following is the working principle of each part of the optical system of dual-channel display: After the user wears the AR device, the user's line of sight is locked, the light-emitting element 2 emits infrared rays, and the infrared rays are projected into the user's pupil through the free-form surface prism 11 to produce a dark pupil effect in the eye. The first lens module 3 starts and obtains the image of the human eye, and then processes the image to extract parameter information such as the center point of the human eye pupil, the center point of the iris, and the position of the left and right eye corners. Two three-dimensional vectors are formed based on the left and right eye corners, the center point of the pupil and the optical axis, and then the line of sight calibration is repeated many times to obtain multiple groups of three-dimensional vectors. In the calibration process, a mapping relationship between the 3D structure model of the human eye and the real scene information is established, and finally the line of sight mapping function can be obtained. In the subsequent use process, when the eyeball or head turns, the line of sight direction of the eye can be calculated through image processing combined with the mapping relationship to realize the line of sight tracking function.

[0038] The external environmental image information is obtained through the second lens module 4 and transmitted to the background information processing system in real time. The information processing system detects and segments the obtained environmental image, and then generates corresponding target identity information. Then, based on the information obtained by the first lens module 3, the user's line of sight focus point is determined, and then the target object is located according to the line of sight focus point, and then the target object is matched with the obtained target identity information, and then the virtual and real images are superimposed and input into the display 13 of the projection module 1. The image source on the display 13 is then projected to the user's pupil via a single free-form surface prism 11, and then the user can see the virtual feature information superimposed on the real scene, thereby realizing the function of augmented reality.

[0039] After the display 13 projects the light of the image source into the free-form surface prism 11, part of the light will enter the compensation prism 12 from the free-form surface prism 11 to compensate for the distortion of the projected light, thereby adjusting the overall distortion value of the light and optimizing the imaging quality.

[0040] It is understood that the present invention, through the projection module 1 composed of a single free-form surface prism 11 and a compensation prism 12, further adding a first lens module 3 and a second lens module 4 to assist the projection module 1, can realize the projection path of a single prism, reduce the light loss rate and correct the chromatic aberration, and can effectively reduce the optical path complexity of the optical system, while reducing the volume and weight of the optical path system, thereby reducing the volume and weight of the AR device, and thus improving the user experience of the AR device.

[0041] For further information, please refer to Figure 2In one embodiment, the free-form surface prism 11 includes a first curved surface 111, a second curved surface 112 and a third curved surface 113; the first curved surface 111 is far away from the compensation prism 12, the second curved surface 112 is close to the compensation prism 12, a semi-transparent and semi-reflective film is attached to the second curved surface 112, and the third curved surface 113 faces the display 13 and the light-emitting element 2.

[0042] Specifically, the first curved surface 111, the second curved surface 112 and the third curved surface 113 are mutually surrounded to form a free-form surface prism 11, and the free-form surface prism 11 is a wedge-shaped prism. The light emitted by the display 13 enters the free-form surface prism 11 after being refracted by the third curved surface 113, and the refracted light is projected onto the first curved surface 111 and is totally reflected on the first curved surface 111, and the light is totally reflected from the first curved surface 111 to the second curved surface 112. Since a semi-transmissive and semi-reflective film is attached to the second curved surface 112, the light is both reflected and transmitted on the second curved surface 112 after reaching the second curved surface 112. The light reflected on the second curved surface 112 passes through the first curved surface 111, leaves the free-form surface prism 11, and is projected into the pupil of the user; the light transmitted on the second curved surface 112 passes through the second curved surface 112 into the compensation prism 12, and the perspective distortion of the light caused by the semi-transparent and semi-reflective film is compensated in the compensation prism 12, thereby optimizing the overall distortion value of the light after projection.

[0043] Please refer to Figure 3 , Figure 3 (a) is the MTF curve of the projection channel composed of the free-form surface prism 11. Figure 3 From the information in (a), it can be seen that under the full range of field light, when the spatial frequency is 30lp / mm, the MTF value is better than 0.28. This figure is an MTF curve of the transmission channel formed by the compensation prism 12. From the information in the figure, it can be seen that under the full range of field light, when the spatial frequency is 30lp / mm, the MTF value is better than 0.16.

[0044] For further information, please refer to Figure 4 , Figure 4 (a) is a distortion curve diagram of the projection module 1 when the compensation prism 12 is not added. Figure 4 (b) is a distortion curve diagram of the projection module 1 after the compensation prism 12 is added. Figure 4 From the information in (a), it can be seen that when the compensation prism 12 is not added, the maximum distortion value under the full field of view is 2.79%. From the information in (b), it can be seen that after the compensation prism 12 is added, the maximum distortion value under the full field of view is 0.29%. That is, after the compensation prism 12 is added, the distortion of the projection module 1 is improved.

[0045] In a preferred embodiment, a diffraction element is attached to the first curved surface 111 .

[0046] The diffraction element is used to correct the chromatic aberration of light. The diffraction element can be a diffraction element with a binary surface phase representation or a diffraction element with an aspherical surface, which can be selected according to actual design requirements. When the diffraction element is an aspherical diffraction element, a microstructure needs to be etched on the base surface of the first curved surface 111.

[0047] Preferably, to facilitate ray tracing, the diffraction element is a diffraction element with a binary face phase characterization. Specifically, the binary face is a four-term polynomial binary face, and its related coefficients are A1=1.16, A2=-3.457E-002, A3=-9.18E-004, A4=-1.70E-005, and the diffraction order M is 1.

[0048] For details, please refer to Figure 5 , Figure 5 : is a comparison diagram of vertical axis chromatic aberration between the free-form surface prism 11 with a diffraction element attached and the free-form surface prism 11 without a diffraction element attached. Figure 5 It can be seen that in the edge field of view, the vertical axis chromatic aberration value of the free-form surface prism 11 with the diffractive element attached is 3.04um, which is relatively small, and the improvement is 92.3% compared with the free-form surface prism 11 without the diffractive element attached. In the central field of view, the vertical axis chromatic aberration value of the free-form surface prism 11 with the diffractive element attached is -13.98um, which is 1.55um higher than the free-form surface prism 11 without the diffractive element attached.

[0049] For further information, please refer to Figure 6 , Figure 6 : is a comparison diagram of the color focus shift curves of the free-form surface prism 11 with a diffraction element attached and the free-form surface prism 11 without a diffraction element attached. Figure 6 It can be seen that after the diffraction element is attached, the maximum focal shift of the free-form surface prism 11 changes from 116.417 um to 74.491 um, an increase of 36.01%.

[0050] It is understandable that, without increasing the number of prisms, attaching a diffraction element on the first curved surface 111 can effectively correct the chromatic aberration of light, reduce the system chromatic aberration of the optical system, and thus improve the imaging quality.

[0051] Furthermore, in one embodiment, the angular resolution of the display 13 is θ, the angular resolution of the human eye is δ, and they satisfy: δ<θ<2δ, the horizontal field of view angle of the display 13 is w, the vertical field of view angle of the display 13 is v, and they satisfy: 20.19° <w<40.38°,15.21°<v<30.42°。

[0052] Specifically, to make full use of the resolution of the display 13, the aspect ratio of the field of view and the image source should be consistent, and the field of view and the resolution of the display 13 need to satisfy:

[0053]

[0054] Under normal circumstances, the angular resolution δ of the human eye is generally 0.017°. Then, the horizontal field of view angle w of the display 13 and the vertical field of view angle v of the display 13 can be determined, and they satisfy: 20.19° < w < 40.38°, 15.21° < v < 30.42°. Preferably, w = 31.6° and v = 24.2°.

[0055] It can be understood that by setting the angular resolution, horizontal field of view angle and vertical field of view angle of the display 13, the clarity of the imaged picture can be ensured, the positioning can be accurate, the three-dimensional sense of the image can be enhanced, and the projection distortion can be effectively controlled within 5%, and the perspective distortion can be controlled within 3% to ensure the comfort of the user wearing.

[0056] Furthermore, please refer to Figure 7 , in this embodiment, the first lens module 3 includes a first lens 31, a first diaphragm 32, a second lens 33, a third lens 34, a protective sheet 35 and a first image plane 36 arranged in sequence. The first lens 31, the second lens 33 and the third lens 34 are all plastic aspherical lenses.

[0057] Specifically, in a preferred implementation manner, the curvature of the surface of the first lens 31 away from the first diaphragm 32 is 8.74E-001 mm, and the thickness is 5.00E-001 mm. The curvature of the surface of the first lens 31 close to the first diaphragm 32 is 3.55E+000 mm, and the thickness is 3.57E-001 mm. The curvature of the surface of the second lens 33 close to the first diaphragm 32 is -2.31E+000 mm, and the thickness is 2.29E-001 mm. The curvature of the surface of the second lens 33 away from the first diaphragm 32 is -5.46E+000 mm, and the thickness is 5.00E-002 mm. The curvature of the surface of the third lens 34 close to the first diaphragm 32 is -6.24E+000 mm, and the thickness is 4.10E-001 mm. The curvature of the surface of the third lens 34 away from the first diaphragm 32 is 4.02E+000 mm, and the thickness is 5.15E-002 mm.

[0058] Even further, please refer to Figure 8 , Figure 8 The (a) to (c) in respectively correspond to the spot diagram distribution of the first lens module 3 at working distances of 29.82 mm, 31.48 mm and 33.14 mm. From Figure 8It can be seen from the information that at the three working distances, the maximum root mean square radius of the full field of view is 1.779um, which is within the size of two pixels (2.2um), indicating that the image plane of the first lens module 3 is clear and the imaging quality is relatively good.

[0059] Please refer to Fig. 9 , Fig. 9 (a) to (c) in the figure correspond to the MTF curves of the first lens module 3 at working distances of 29.82mm, 31.48mm and 33.14mm, respectively. It is easy to understand that the closer the MTF value is to 1, the better the performance of the lens. From the information in the figure, it can be seen that at different field of view heights in the low-frequency region, the MTF values ​​along the tangent direction and the sagittal direction tend to 1, which means that the imaging quality is relatively good; with the increase of spatial frequency, at different field of view heights, the MTF values ​​along the tangent direction and the sagittal direction decrease slowly. At the 1 / 2 Nyquist frequency of 220l p / mm, the MTF values ​​of the entire field of view are all greater than 0.23, indicating that the imaging quality meets the requirements.

[0060] It can be understood that by setting the first lens 31, the second lens 33 and the third lens 34, while meeting the imaging requirements, the volume of the first lens module 3 can be effectively reduced, thereby reducing the space occupied by the first lens module 3 in the AR device, thereby reducing the volume and weight of the AR device, thereby improving the user experience.

[0061] For further information, please refer to Fig.10 In one embodiment, the second lens module 4 includes a fourth lens 41, a fifth lens 42, a sixth lens 43, a second aperture 46, a doublet lens 44 and a second image plane 45 which are arranged in sequence. The fourth lens 41 and the fifth lens 42 are both negative power lenses, and the sixth lens 43 and the doublet lens 44 are both positive power lenses.

[0062] Specifically, the fourth lens 41 is a negative power lens, and its surface is curved outward, which greatly reduces the deflection angle of light entering the second lens module 4 under a large field of view, and can effectively prevent the problem of large-angle light overflow. The fifth lens 42 is also a negative power lens, which can further incorporate large-field light. The sixth lens 43 is a positive focal lens, which can correct the incorporated light. The double-cemented lens 44 is also a positive angle lens, which can further correct aberration imaging. At the same time, the double-cemented lens 44 can achieve mutual compensation of dispersion, thereby playing a role in achromatism.

[0063] For further information, please refer to Fig.11 , Fig.11 is the distribution of the spot diagram of the second lens module 4 when the working distance is 250 mm to 50000 mm, Fig.11From the information in, we can see that at a working distance of 250mm to 50000mm, the maximum RMS radius of the full field of view is 1.891um, which is within the size of two pixels (2.2um). This shows that the image plane of the second lens module 4 is clear and the imaging quality is relatively good.

[0064] Please refer to Fig.12 , Fig.12 (a) to (d) in FIG. 4 correspond to the MTF curves of the second lens module 4 when the working distance is 250 mm, 500 mm, 1500 mm and 50000 mm respectively. Fig.12 From the information in, it can be seen that within the full working distance range, at the Nyquist frequency of 240l p / mm, the MTF values ​​of the full field of view are all greater than 0.1, and the MTF values ​​near the center field of view are all greater than 0.25, which means that the imaging quality of the second lens module 4 in the full field of view is relatively good and can meet the requirements.

[0065] It can be understood that by setting the fourth lens 41, the fifth lens 42, the sixth lens 43 and the double-cemented lens 44, the volume of the second lens module 4 can be effectively reduced while meeting the imaging requirements, thereby reducing the space occupied by the second lens module 4 in the AR device, thereby reducing the volume and weight of the AR device, thereby improving the user experience.

[0066] In summary, the present invention uses a projection module 1 composed of a single free-form surface prism 11 and a compensation prism 12, and then adds a first lens module 3 and a second lens module 4 to assist the projection module 1, so as to realize the projection path of a single prism, reduce the light loss rate and correct the chromatic aberration, and can effectively reduce the optical path complexity of the optical system, while reducing the volume and weight of the optical path system, thereby reducing the volume and weight of the AR device, and thus improving the user experience of the AR device.

[0067] The second aspect of the present invention provides an AR device, which includes the aforementioned dual-channel display optical system, which can effectively reduce the light loss rate and correct the chromatic aberration, effectively reduce the optical path complexity of the optical system, and at the same time reduce the volume and weight of the optical path system, thereby reducing the volume and weight of the AR device, thereby improving the user experience of the AR device.

[0068] The above is only a specific implementation method of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. An optical system for dual-channel display, characterized in that: It includes a projection module, a light-emitting element, a first lens module and a second lens module; the projection module includes a free-form surface prism, a compensation prism and a display; the compensation prism is arranged on one side of the free-form surface prism, the first lens module is arranged at one end of the free-form surface prism, and the display, the light-emitting element and the second lens module are all arranged at the other end of the free-form surface prism.

2. The optical system for dual-channel display according to claim 1, characterized in that: The free-form surface prism includes a first curved surface, a second curved surface and a third curved surface; the first curved surface is far away from the compensation prism, the second curved surface is close to the compensation prism, a semi-transparent and semi-reflective film is attached to the second curved surface, and the third curved surface faces the display and the light-emitting element.

3. The optical system for dual-channel display according to claim 2, characterized in that: A diffraction element is attached to the first curved surface.

4. The optical system for dual-channel display according to claim 1, characterized in that: The angular resolution of the display is θ, the angular resolution of the human eye is δ, and they satisfy: δ<θ<2δ.

5. The optical system for dual-channel display according to claim 1, characterized in that: The horizontal viewing angle of the display is w, the vertical viewing angle of the display is v, and they satisfy: 20.19° <w<40.38°,15.21°<v<30.42°。 6. The optical system for dual-channel display according to claim 1, characterized in that: The first lens module includes a first lens, a first aperture, a second lens, a third lens, a protection sheet and a first image plane which are arranged in sequence.

7. The optical system for dual-channel display according to claim 6, characterized in that: The first lens, the second lens and the third lens are all plastic aspherical lenses.

8. The dual-channel display optical system according to claim 1, characterized in that: The second lens module includes a fourth lens, a fifth lens, a sixth lens, a second aperture, a doublet lens and a second image plane which are arranged in sequence.

9. The optical system for dual-channel display according to claim 8, characterized in that: The fourth lens and the fifth lens are both negative power lenses, and the sixth lens and the doublet lens are both positive power lenses.

10. An AR device, characterized in that: An optical system comprising a dual channel display as claimed in any one of claims 1 to 9.

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