Optical module and wearable device

Abstract

This application provides an optical module and a wearable device. The optical module includes an imaging lens group, and a beam splitter, a phase retarder, and a polarization reflector disposed within the imaging lens group. The phase retarder is located between the beam splitter and the polarization reflector. The optical module also includes a display screen disposed on one side of the imaging lens group and on the same optical axis as the imaging lens group. The display screen is configured to move relative to the imaging lens group along the optical axis to adjust the back cutoff of the optical module. The optical module satisfies the condition that the absolute distance |D(x)| of the display screen moving along the optical axis is proportional to the spatial position x of the eye box. The optical module provided in this application can achieve high-definition imaging across the entire eye box range with a large field of view.

Description

Technical Field

[0001] This application relates to the field of optical imaging technology, and more specifically, to an optical module and a wearable device. Background Technology

[0002] Virtual reality devices utilize the imaging characteristics of optical modules to magnify images at short distances, enabling users to experience an immersive visual experience. Differences in head circumference and interpupillary distance among users will affect the actual display effect of the optical modules.

[0003] In existing virtual reality optical solutions, to ensure the image quality at the eyepiece edges meets design requirements, the image quality at the eyepiece center and edges is balanced. This involves appropriately lowering the MTF (Mean Transmission Frequency) at the eyepiece center to improve the MTF at the edges. However, this inevitably results in fluctuations in the overall eyepiece MTF curve relative to the field of view. This issue stems from defocusing caused by trying to maintain good image quality at the edges. Current virtual reality devices are designed with fixed screens, and defocusing occurs when trying to achieve good image quality across different eyepiece positions, thus limiting improvements in image quality. Summary of the Invention

[0004] The purpose of this application is to provide a new technical solution for an optical module and wearable device, which can achieve high-definition imaging across the entire eye box range with a wide field of view.

[0005] In a first aspect, this application provides an optical module. The optical module includes an imaging lens group, and a beam splitter, a phase retarder, and a polarization reflection element disposed within the imaging lens group; wherein the phase retarder is located between the beam splitter and the polarization reflection element;

[0006] The optical module also includes a display screen, which is located on one side of the imaging lens group and on the same optical axis as the imaging lens group. The display screen is configured to be movable relative to the imaging lens group along the optical axis to adjust the back cutoff of the optical module.

[0007] The optical module satisfies the following condition: the absolute distance |D(x)| that the display screen moves along the optical axis is proportional to the spatial position x of the eye box.

[0008] Optionally, the moving distance D(x) of the display screen along the optical axis and the spatial position x of the eye box satisfy a downward-opening parabolic relationship: x 2 = -2*p*(D(x)-d);

[0009] Where x∈R, D(x)≤d, d is the distance from the display screen to the imaging lens group corresponding to the center position of the eye box, d>0, p is the distance from the focus of the parabola to the directrix of the parabola, p>0, the coordinates of the focus are (0, dp / 2), and the equation of the directrix is ​​y=p / 2+d.

[0010] Optionally, the distance D(x) that the display screen moves along the optical axis and the spatial position x of the eye box satisfy the following functional equation:

[0011] D(x) = p1*x 6 +p2*x 5 +p3*x 4 +p4*x 3 +p5*x 2 +p6*x+p7;

[0012] Among them, -1.3e -07 <p1<-1.0e -05 -1.2e -06 <p2<-1.0e -04 -1.1e -05 <p3<-1.0e -03 -1.3e -05 <p4<-1.0e -02 -1.2e -05 <p5<-1.0e -02 -1.1e -05 <p6<-1.0, 1.5<p7<50;

[0013] x represents the radial distance from any position of the eye box to the center of the eye box, x = 0 represents the center position of the eye box, x < 0 represents the spatial position of the eye box along the negative direction with the center of the eye box as the reference point, x > 0 represents the spatial position of the eye box along the positive direction with the center of the eye box as the reference point, and p7 is the distance from the side of the imaging lens group closest to the display screen to the display screen.

[0014] Optionally, the functional equation satisfying the movement distance D(x) of the display screen along the optical axis and the spatial position x of the eye box, for the imaging lens group formed by any surface-shaped lens, satisfies: Data fitting R 2 ≥0.95.

[0015] Optionally, the optical module further includes an eye-tracking component, which is disposed close to the imaging lens group;

[0016] The eye-tracking component is used to acquire the wearer's eye position information in order to control and adjust the distance between the display screen and the imaging lens group.

[0017] Optionally, the display screen is used to emit circularly polarized light to the imaging lens group, and the side of the display screen closest to the imaging lens group is the light-emitting side, which is provided with a screen protection device.

[0018] Optionally, the imaging lens group includes at least one lens, and the surface type of the lens includes a plane, a spherical surface, an aspherical surface, a Fresnel surface, or a freeform surface.

[0019] Optionally, the imaging lens group includes a first lens and a second lens, wherein the second lens is located between the first lens and the display screen;

[0020] The beam splitter is located on either side of the second lens, and the phase delayer and the polarization reflection element are located on either side of the first lens.

[0021] Optionally, the beam-splitting element is disposed on the surface of the second lens near the display screen;

[0022] The optical module also includes a polarization element. The phase delayer, the polarization reflection element, and the polarization element are stacked in sequence to form a composite element. The composite element is located on the surface of the first lens away from the display screen.

[0023] Optionally, the fast axis direction of the beam splitter forms a 45-degree angle with the transmission direction of the polarization reflection element.

[0024] Optionally, the polarization direction of the polarization element is the same as the polarization transmission direction of the polarization reflection element.

[0025] Optionally, the optical module satisfies the following condition: the total system length TL of the optical module is approximately equal to the aperture D of the largest lens in the imaging module. max The ratio 0.4 < TL / D max <0.9.

[0026] Optionally, the effective focal length EFFL of the optical module is: 13mm < EFFL < 33mm.

[0027] Secondly, this application provides a wearable device. The wearable device includes:

[0028] Casing; and

[0029] The optical module as described in the first aspect is disposed in the housing.

[0030] The beneficial effects of this application are as follows:

[0031] According to the embodiments of this application, an optical module is provided. By designing a display screen with adjustable back focal length, the design freedom of the optical module can be increased. By reasonably adjusting the distance between the display screen and the imaging lens group in the optical module, the back focal length compensation effect can be achieved for the optical imaging quality at different eye box positions. This is beneficial for the design of optical modules under a large field of view full eye box, and can further improve the imaging quality, enabling high-definition imaging within the entire eye box range under a large field of view.

[0032] Other features and advantages of this specification will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0033] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of this specification and, together with their description, serve to explain the principles of this specification.

[0034] Figure 1 This is a schematic diagram of the structure of the optical module provided in the embodiments of this application;

[0035] Figure 2 The graph shows the variation of MTF (Mean Transformation) with the field of view at different positions of the optical module's eye box.

[0036] Figure 3 This is a defocus image of the edge eyebox of the optical module;

[0037] Figure 4 Schematic diagram of the principal ray from the on-axis / off-axis object point in the central field of view;

[0038] Figure 5 This is a schematic diagram of the optical module structure corresponding to the center position of the eye box in Embodiment 1 of this application (back cutoff: 2.833mm);

[0039] Figure 6 This is a schematic diagram of the optical module structure at the 8mm position of the eye box edge in Embodiment 1 of this application (back cutoff: 2.497mm);

[0040] Figure 7 The MTF value at the center of the eye box in Embodiment 1 of this application;

[0041] Figure 8 The MTF value of the eye box edge 8mm in Embodiment 1 of this application;

[0042] Figure 9 This is the defocus curve of the eye box center in Embodiment 1 of this application;

[0043] Figure 10 This is the defocus curve at the edge of the eye box in Embodiment 1 of this application;

[0044] Figure 11This is a schematic diagram of the optical module structure corresponding to the center position of the eye box in Embodiment 2 of this application (back cutoff: 3.358mm);

[0045] Figure 12 This is a schematic diagram of the optical module structure at the 7mm position of the eye box edge in Embodiment 2 of this application (back cutoff: 3.314mm);

[0046] Figure 13 The MTF value at the center of the eye box in Embodiment 2 of this application;

[0047] Figure 14 The MTF value of the eye box edge 7mm in Embodiment 2 of this application;

[0048] Figure 15 This is the defocus curve of the eye box center in Embodiment 2 of this application;

[0049] Figure 16 This is the defocus curve at the edge of the eye box in Embodiment 2 of this application.

[0050] Explanation of reference numerals in the attached figures:

[0051] 1. First lens; 2. Second lens; 3. Display screen; 4. Screen protector; 5. Beam splitter; 6. Phase delayer; 7. Polarization reflector; 8. Polarization element; 9. Eye-tracking assembly; 10. Overlay element; 01. Human eye. Detailed Implementation

[0052] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0053] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the scope of this application and its application or use.

[0054] Technologies and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such technologies and equipment should be considered part of the specification.

[0055] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0056] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0057] According to one aspect of the embodiments of this application, an optical module is provided, which is suitable for application in a head-mounted display (HMD), such as a VR head-mounted display or an AR head-mounted display. The aforementioned VR head-mounted display may include, for example, VR glasses or VR helmets, and the aforementioned AR head-mounted display may include, for example, AR glasses and AR helmets using a freeform prism scheme or a Birdbath scheme. The embodiments of this application do not impose specific limitations in this regard.

[0058] The optical module provided in this application embodiment is referred to [reference needed]. Figure 1 The optical module includes an imaging lens group, and a beam splitter 5, a phase retarder 6, and a polarization reflection element 7 disposed within the imaging lens group; wherein the phase retarder 6 is located between the beam splitter 5 and the polarization reflection element 7.

[0059] The optical module also includes a display screen 3, which is located on one side of the imaging lens group and on the same optical axis as the imaging lens group. The display screen 3 is configured to be movable relative to the imaging lens group along the optical axis to adjust the back cutoff of the optical module.

[0060] The optical module satisfies:

[0061] The absolute distance |D(x)| that the display screen 3 moves along the optical axis is proportional to the spatial position x of the eye box.

[0062] In the above embodiments of this application, defocus correction is achieved across the entire eyepiece range by adjusting the position of the display screen 3, ensuring optimal imaging quality for the corresponding optical structure across the entire field of view of the eyepiece. In other words, the optical solution provided in this application achieves defocus correction by fixing the lenses in the imaging lens group and moving the display screen 3.

[0063] In the optical solution provided in this application embodiment, the method of fixing the display screen 3 and moving the lens is not adopted. This is mainly because moving the lens requires strict control of the distance between the human eye 01 and the front end of the imaging lens group, i.e., the interpupillary distance. Therefore, the optical module must have two or more lenses. One lens needs to be fixed at the end of the imaging lens group closest to the human eye 01 to ensure that the maximum field of view remains unchanged, while the other lens is designed to be movable. However, this limits the number of lenses that can be set, reducing the flexibility of the optical module design.

[0064] In the design of existing virtual reality optical solutions, to ensure that the imaging quality at the edge of the eyebox meets design requirements, the imaging quality at the center and edge of the eyebox is balanced. This involves appropriately reducing the MTF at the center of the eyebox to improve the MTF at the edge. However, the overall eyebox MTF curve with respect to the field of view will inevitably exhibit fluctuations; that is, the first derivative of the MTF curve from the center field of view to the edge field of view will have different signs. Figure 2 As shown, this problem stems from defocusing caused by trying to maintain the MTF (Mean Transformation Fibre) at the edge of the eyepiece. Figure 3 As shown. Specifically, defocus refers to the image plane not being on the ideal image plane, and the defocus amount is the distance between the ideal image plane and the actual image plane. In the design of virtual reality optical solutions, a reverse design approach is usually adopted, that is, the image plane is the light-emitting surface of the display screen 3 (capable of emitting imaging light). Therefore, adjusting the distance between the light-emitting surface of the display screen 3 and the imaging lens group can eliminate the image quality impact caused by the defocus of the optical module.

[0065] From a geometric optics perspective, when there is a misalignment between the eye's visual axis and the optical axis of the optical module, the optical path difference of the principal ray from the on-axis / off-axis object point passing through the optical element will decrease. To obtain good image quality, the total optical path difference Δ... 总 =0 requires an increase in the optical path difference of the principal ray from the on-axis / off-axis object point outside the optical element, based on Figure 4 The model shown can be derived to show that the optical path difference Δ = L between the principal rays of the object point on / off-axis in the central field of view. 轴外 -L 轴上 There exists a functional relationship Δ=d*tan(θ / 2), where d is the entrance pupil diameter of the optical module near the display screen. Therefore, an increase in the optical path difference requires a decrease in the distance (air gap) between the imaging lens group and the display screen 3. In other words, as the center of the eyepiece moves away from the display screen 3, the display screen 3 should move closer to the imaging lens group. This ensures good image quality while considering different eyepiece positions, avoiding defocus issues that hinder image quality improvement.

[0066] According to the conservation of optical extension, for the same optical module, the aperture angle is inversely proportional to the cross-sectional area. Therefore, in the case of large eyeboxes and large field of view, improving the resolution of the optical module requires the optical module to have higher aberration correction capabilities. This requires the optical module to have stricter processing tolerances, which will also affect the production yield and place high demands on optical design.

[0067] In the optical module provided in this application embodiment, in order to correct defocus within the full eye box, the absolute distance that the display screen 3 moves along the optical axis is proportional to the spatial position of the eye box. According to the above optical path difference Δ=d*tan(θ / 2), it can be seen that increasing the optical path difference requires a decrease in the distance (air gap) between the imaging lens group and the display screen. That is, the position of the display screen corresponding to the central eye box position is the maximum distance position from the display screen 3 to the imaging lens group within the full eye box.

[0068] The optical module proposed in this application, by designing a display screen 3 with an adjustable back focal length, can increase the design freedom of the optical module. By reasonably adjusting the distance between the display screen 3 and the imaging lens group in the optical module, it has a back focal compensation effect on the optical imaging quality at different eye box positions, which is beneficial to the design of optical modules under a large field of view full eye box, and can further improve the imaging quality, and can achieve high-definition imaging within the entire eye box range under a large field of view.

[0069] The optical solution proposed in this application innovatively addresses the problem of defocus at different eyebox positions in the optical module design. This optical module design has the performance advantages of a large eyebox, a wide field of view, and high resolution.

[0070] In some examples of this application, the moving distance D(x) of the display screen 3 along the optical axis and the spatial position x of the eye box satisfy a downward-opening parabolic relationship: x 2 =-2*p*(D(x)-d); where x∈R, D(x)≤d, d is the distance from the display screen to the imaging lens group corresponding to the center position of the eye box, d>0, p is the distance from the focus of the parabola to the directrix of the parabola, p>0, the coordinates of the focus are (0, dp / 2), and the equation of the directrix is ​​y=p / 2+d.

[0071] In other words, in the optical solution of this application, when the display screen 3 moves, the spatial position x of the eye box should be taken into account.

[0072] Specifically, the moving distance D(x) of the display screen 3 along the optical axis and the spatial position x of the eye box satisfy a downward-opening parabolic relationship. Thus, whether the display screen 3 moves upward or downward, the closer the center of the eye box is to the display screen 3, the closer the display screen 3 should be to the imaging lens group. This eliminates the effect of defocus, resulting in an optical module with the advantages of a large eye box, a wide field of view, and high resolution.

[0073] Furthermore, the distance D(x) that the display screen moves along the optical axis and the spatial position x of the eye box satisfy the following functional equation:

[0074] D(x) = p1*x 6 +p2*x5 +p3*x 4 +p4*x 3 +p5*x 2 +p6*x+p7;

[0075] Among them, -1.3e -07 <p1<-1.0e -05 -1.2e -06 <p2<-1.0e -04 -1.1e -05 <p3<-1.0e -03 -1.3e -05 <p4<-1.0e -02 -1.2e -05 <p5<-1.0e -02 -1.1e -05 <p6<-1.0, 1.5<p7<50; x represents the radial distance from any position of the eye box to the center of the eye box, x=0 represents the center position of the eye box, x<0 represents the spatial position of the eye box along the negative direction with the center of the eye box as the reference point, x>0 represents the spatial position of the eye box along the positive direction with the center of the eye box as the reference point, and p7 is the distance from the side of the imaging lens group closest to the display screen to the display screen.

[0076] Based on the fact that the moving distance D(x) of the display screen 3 along the optical axis and the spatial position x of the eye box satisfy a parabolic relationship with the opening downwards, the above-mentioned functional equation was obtained by fitting multiple light irradiations, thereby further defining the movement rules of the display screen 3.

[0077] Where x represents the radial distance from any position on the eye box to the center of the eye box.

[0078] It should be noted that the moving distance D(x) of the display screen 3 along the optical axis and the spatial position x of the eye box satisfy a parabolic relationship with the opening downwards, and the moving distance D(x) of the display screen along the optical axis and the spatial position x of the eye box satisfy the following functional equations are applicable to optical design architectures that are rotationally symmetric or non-rotationally symmetric.

[0079] In the optical module provided in this application embodiment, there are various ways to control the movement rules of the display screen 3, which can be flexibly selected as needed.

[0080] The functional equation satisfied by the moving distance D(x) of the display screen 3 along the optical axis and the spatial position x of the eye box, for the imaging lens group formed by any surface-shaped lens, satisfies: Data fitting R 2 ≥0.95.

[0081] Based on the functional equation fitted between the moving distance D(x) of the display screen 3 along the optical axis and the spatial position x of the eye box, here R 2 It is a parameter that characterizes the degree of fit. In this application, the fitting parameter can reach 0.95 or even higher.

[0082] It should be noted that any optical design that can be fitted with the above-mentioned functional equation within the above-mentioned range and has a fitting accuracy of 0.95 or higher is considered to be within the protection scope of this application.

[0083] See some examples in this application. Figure 1 The optical module also includes an eye-tracking component 9, which is positioned close to the imaging lens group. The eye-tracking component 9 is used to acquire the wearer's eye position information to control and adjust the distance between the display screen 3 and the imaging lens group.

[0084] To achieve a virtual reality optical module design that enables high-definition imaging across the entire eyebox with a wide field of view, the optical solution of this application also provides a large eyebox virtual reality optical design scheme based on eye tracking.

[0085] Specifically, the optical module proposed in this application embodiment can capture the user's eye position information through the eye tracking component 9, and then adjust the spatial position of the display screen 3 in the optical module through the processor based on the acquired eye position information, thereby achieving high-definition imaging within a large eye box range in VR product design.

[0086] Optionally, the eye-tracking component 9 may include an infrared light source and an infrared camera device opposite to the human eye 01.

[0087] In addition, the eye-tracking component 9 should be positioned as close as possible to the human eye 01 to improve the accuracy of eye tracking.

[0088] See some examples in this application. Figure 1 The display screen 3 is used to emit circularly polarized light to the imaging lens group. The side of the display screen 3 closest to the imaging lens group is the light-emitting side, and a screen protection device 4 is provided on the light-emitting side.

[0089] The display screen 3 is, for example, a miniature display screen. The display screen 3 can be controlled by a driving device (such as a motor) to move linearly along the optical axis to move closer to or further away from the imaging lens group.

[0090] Optionally, the display screen 3 can be any screen, such as a MicroOLED screen or an LCD screen, where the light-emitting surface can be made into a rotationally symmetrical structure.

[0091] The screen protection device 4 is, for example, a glass protective plate, which can be adhered and fixed to the light-emitting surface of the display screen 3 to protect the display screen 3.

[0092] It should be noted that, see Figure 1 The light emitted by the display screen 3 should be circularly polarized light, which can directly enter the imaging lens group on the left. After post-processing by the imaging lens group, a clear picture can be presented in the human eye 01.

[0093] When the display screen 3 emits linearly polarized light, the imaging light can be converted from linearly polarized light to circularly polarized light by a phase delayer and polarization reflection element before entering the imaging lens group.

[0094] Optionally, the imaging lens group includes at least one lens, and the surface type of the lens includes a plane, a spherical surface, an aspherical surface, a Fresnel surface, or a freeform surface.

[0095] In the optical module provided in this application embodiment, the number of lenses can be set to one, two, or more than three. A larger number of lenses is beneficial for improving image quality, but it increases the weight, size, and production cost of the optical module. Typically, in VR devices based on folded optical paths, 1 to 3 optical lenses are used.

[0096] The lens surface can be planar, spherical, aspherical, Fresnel, freeform, or other surface types. Specifically, planar, spherical, aspherical, and Fresnel surfaces form a rotationally symmetric optical architecture, while freeform surfaces form a non-rotationally symmetric optical architecture. The optical module provided in this application does not have requirements on the lens surface type, allowing for a high degree of design freedom.

[0097] In one example, see Figure 1 The imaging lens group includes a first lens 1 and a second lens 2, with the second lens 2 located between the first lens 1 and the display screen 3; the beam splitter 5 is disposed on either side of the second lens 2, and the phase delayer 6 and the polarization reflection element 7 are disposed on either side of the first lens 1.

[0098] Optionally, the beam splitter 5 is disposed on the surface of the second lens 2 near the display screen 3; the optical module also includes a polarization element 8, and the phase delayer 6, the polarization reflection element 7 and the polarization element 8 are stacked in sequence to form a superimposed element 10, which is disposed on the surface of the first lens 1 away from the display screen 3.

[0099] In the optical module of this application embodiment, the number of lenses includes, but is not limited to, the two mentioned above, and the number of lenses can be flexibly adjusted according to specific needs. While increasing the number of lenses can improve the imaging quality of the optical module, it also affects the size of the optical module along the optical axis (lateral direction), resulting in a larger volume and increased weight of the optical module.

[0100] The beam splitter 5 is, for example, a semi-transparent and semi-reflective device, which allows a portion of the light to pass through while the other portion is reflected.

[0101] Optionally, the reflectivity of the beam-splitting element is, for example, 47% to 53%.

[0102] The phase delayer 6 is, for example, a quarter-wave plate. Of course, the phase delayer 6 can also be configured as other phase delay plates, such as a half-wave plate, as needed.

[0103] The phase delayer 6 can be used to change the polarization state of light. For example, it can be used to convert linearly polarized light into circularly polarized light, or circularly polarized light into linearly polarized light.

[0104] The polarization reflecting element 7 is a polarization reflector that reflects horizontally linearly polarized light and transmits vertically linearly polarized light, or a polarization reflector that reflects linearly polarized light at any other specific angle and transmits linearly polarized light perpendicular to that angle. In the embodiments of this application, the phase delayer 6 and the polarization reflecting element 7 work together to resolve and transmit light.

[0105] The polarization element 8 is configured to reduce stray light caused by the polarization reflectivity of the polarization reflector not being 100%.

[0106] It should be noted that the arrangement of the beam splitter 5, the phase delayer 6 and the polarization reflection element 7 within the lens group is relatively flexible. They can be arranged as needed, for example, between the first lens 1 and the second lens 2 mentioned above. However, it is necessary to ensure that the phase delayer 6 is located between the beam splitter 5 and the polarization reflection element 7.

[0107] The fast axis direction of the beam splitter 5 forms a 45-degree angle with the transmission direction of the polarization reflection element 7.

[0108] The polarization direction of the polarization element 8 is the same as the polarization transmission direction of the polarization reflection element 7.

[0109] In the example of this application, the design structure of compensating for defocus at different eye box positions by adjusting the position of the display screen 3 can be applied to a virtual reality pancake optical module. The pancake optical path design can reduce the overall optical length of the optical module, which is beneficial for reducing the size of the optical module.

[0110] Of course, the optical solutions of this application embodiment can also be used in virtual reality Fresnel optical modules and other application types of optical modules with large eyeboxes and large field of view, and there are no limitations on this.

[0111] The optical module satisfies the following condition: the total system length TL of the optical module is equal to the aperture D of the largest lens in the imaging module. max The ratio 0.4 < TL / D max <0.9.

[0112] The effective focal length EFFL of the optical module is 13mm < EFFL < 33mm.

[0113] The optical module provided in this application embodiment is small in size and light in weight, and can produce clear images under a wide field of view full-eye box.

[0114] It should be noted that the field of view of the optical module can reach 110 degrees or even greater. Within this large field of view, clear imaging can be achieved across the entire eyebox.

[0115] See Figure 1 This is a schematic diagram of the structure of an optical module provided in a specific example of this application. Specifically, the optical module mainly consists of a first lens 1, a second lens 2, a display screen 3, a screen protector 4, a beam splitter 5, a phase delayer 6, a polarization reflection element 7, a polarization element 8, and an eye-tracking component 9. The phase delayer 6, the polarization reflection element 7, and the polarization element 8 form a superimposed element 10, which is disposed on the surface of the first lens 1 away from the display screen 3. The beam splitter 5 is disposed on the surface of the second lens 2 close to the display screen 3. The screen protector 4 is attached to the display screen 3. When using the optical module, the first lens 1 is close to the human eye 01. The display screen 3 is a miniature display screen, and its distance from the second lens 2 can be dynamically adjusted in the optical axis direction.

[0116] In the superimposed element 10, the phase delayer 6 can be a quarter-wave plate or other element that can convert the phase of light. The polarization reflection element 7 can reflect linearly polarized light in the horizontal / vertical direction and transmit linearly polarized light in the vertical / horizontal direction. The polarization direction of the polarization element 8 is the same as the polarization transmission direction of the polarization reflection element 7. The polarization element 8 in the superimposed element 10 is used to reduce stray light caused by the polarization reflectivity of the polarization reflector not being 100%. The eye-tracking component 9 is used to detect the spatial position information of the wearer's eyeballs. After feeding it back to the computing center, clear imaging at different eye positions is achieved by adjusting the distance between the display screen 3 and the screen protection device 4 and the second lens 2.

[0117] After the eye-tracking component 9 adjusts the spatial position of the display screen 3, left-hand circularly polarized light is emitted from the display screen 3. After passing through the screen protection device 4, the beam splitter 5, the second lens 2, the first lens 1, and the phase delayer 6 in the superimposed element 10, it is converted into horizontal / vertical linearly polarized light. After passing through the vertical / horizontal polarization reflection element 7 in the superimposed element 10, it is reflected and then converted into left-hand circularly polarized light after passing through the phase delayer 6 again. After being reflected by the first lens 1, the second lens 2, and the beam splitter 6, it is converted into right-hand circularly polarized light. After passing through the second lens 2, the first lens 1, and the superimposed element 10 again, it is imaged in the human eye 01.

[0118] In the optical module of the above example, an optical module with a large eye box and a large field of view can be designed based on a two-piece folded optical path VR thin and light optical solution. The position of the display screen 3 can be flexibly adjusted by monitoring the wearer's eye position through eye tracking. This effectively solves the design difficulty of defocusing at different eye box positions caused by the need to balance the imaging quality of the large eye box under a large field of view in the optical design of the virtual reality folded optical path architecture. This can greatly improve the optical performance of the entire eye box.

[0119] The optical module provided in this application will be described in detail below through two embodiments.

[0120] Example 1

[0121] See Figure 5 and Figure 6As shown, the optical module includes a first lens 1, a second lens 2, and a display screen 3 arranged sequentially along the same optical axis. The first lens 1 and the second lens 2 are aspherical lenses. The surface 1R1 of the first lens 1 near the human eye 01 is a plane, and the surface 1R2 of the first lens 1 away from the human eye 01 is a convex aspherical surface. The surface 2R1 of the second lens 2 near the human eye 01 is a convex aspherical surface, and the surface 2R2 of the second lens 2 away from the human eye 01 is also a convex aspherical surface.

[0122] The beam splitter 5 is disposed on the surface 2R2 of the second lens 2. The phase retarder 6, the polarization reflection element 7, and the polarization reflection element 8 form a superimposed element 10 and are disposed on the surface 1R1 of the first lens 1. The fast axis direction of the beam splitter 5 forms a 45° angle with the transmission direction of the polarization reflection element 7. The polarization direction of the polarization element 8 is the same as the polarization transmission direction of the polarization reflection element 7.

[0123] The display screen 3 is configured to move relative to the second lens 2 along the optical axis to approach or move away from the second lens 2; the display screen 3 is a 2.5-inch screen, a fast LCD, with a pixel size of 24.0μm, an effective light-emitting area of ​​43.2mm × 43.2mm, an optical module field of view of 110 degrees, and an optical module eye box of 4±6mm, totaling 16mm; the optical module satisfies the following: the total system length TL of the optical module is greater than or equal to the aperture D of the largest lens in the imaging module. max The ratio 0.5 < TL / D max <0.9; The effective focal length EFFL of the optical module is: 13.5mm < EFFL < 26.5mm;

[0124] See Figure 5 A schematic diagram of the optical module structure corresponding to the center position of the eye box is shown, with a back cutoff of 2.833 mm; see also Figure 6 A schematic diagram of the optical module structure is shown at a position 8mm from the edge of the eye box, with a back cutoff of 2.497mm.

[0125] The optical module also includes an eye-tracking component 9, which is used to acquire the wearer's eye position information to control and adjust the distance between the display screen 3 and the second lens 2.

[0126] The specific parameters of the optical module provided in Example 1 are shown in Table 1:

[0127] Table 1

[0128]

[0129] See Figure 7 and Figure 8 : Figure 7 The MTF values ​​at the center of the eyelid are shown; the MTF values ​​are relatively high, all greater than 0.8. (See also...) Figure 8 The MTF value at the edge of the eye box is shown, and the MTF value can reach above 0.5. This shows that the optical module proposed in Embodiment 1 has a good MTF curve under the requirements of large eye box and large field of view, and the MTF value at the edge of the eye box does not hit the bottom. The optical module provided in this embodiment is suitable for the wearing needs of more people.

[0130] Figure 9 The defocus curve at the center of the eye box is shown. Figure 9 With the above Figure 7 Correspondingly, Figure 9 The vertical line in the middle indicates the position of display screen 3. Display screen 3 can achieve a very good imaging effect when it is in this position. Figure 10 The defocus curve at the edge of the eye box is shown. Figure 10 and Figure 8 Correspondingly, Figure 10 The vertical line in the middle indicates the position of the display screen. Figure 10 The image shows that the center position of the eye box has shifted, and a good defocusing effect is achieved by moving the display screen 3 at a position 8mm from the edge of the eye box. It can be seen that the MTF value decreases outside the vertical line in the middle.

[0131] Example 2

[0132] See Figure 11 and Figure 12 As shown, the optical module includes a first lens 1, a second lens 2, and a display screen 3 arranged sequentially along the same optical axis. The first lens 1 and the second lens 2 are aspherical lenses. Specifically, the surface 1R1 of the first lens 1 near the human eye 01 is a concave aspherical surface, and the surface 1R2 of the first lens 1 away from the human eye 01 is a convex aspherical surface. The surface 2R1 of the second lens 2 near the human eye 01 is a plane, and the surface 2R2 of the second lens 2 away from the human eye 01 is also a convex aspherical surface.

[0133] The beam splitter 5 is disposed on the surface 2R2 of the second lens 2. The phase retarder 6, the polarization reflection element 7, and the polarization reflection element 8 form a superimposed element 10 and are disposed on the surface 1R1 of the first lens 1. The fast axis direction of the beam splitter 5 forms a 45° angle with the transmission direction of the polarization reflection element 7. The polarization direction of the polarization element 8 is the same as the polarization transmission direction of the polarization reflection element 7.

[0134] The display screen 3 is configured to move relative to the second lens 2 along the optical axis to approach or move away from the second lens 2; the display screen 3 is a 2.5-inch screen, a fast LCD, with a pixel size of 24.0μm, an effective light-emitting area of ​​43.2mm × 43.2mm, an optical module field of view of 110 degrees, and an optical module eye box of 4±5mm, totaling 14mm; the optical module satisfies the following: the total system length TL of the optical module is greater than or equal to the aperture D of the largest lens in the imaging module. max The ratio 0.4 < TL / D max <0.8; The effective focal length EFFL of the optical module is: 24.5mm < EFFL < 32.5mm;

[0135] See Figure 5 A schematic diagram of the optical module structure corresponding to the center position of the eye box is shown, with a back cutoff of 3.358 mm; see also Figure 6 A schematic diagram of the optical module structure at a position 8mm from the edge of the eye box is shown, with a back cutoff of 3.314mm.

[0136] The optical module also includes an eye-tracking component 9, which is used to acquire the wearer's eye position information to control and adjust the distance between the display screen 3 and the second lens 2.

[0137] The specific parameters of the optical module provided in Example 2 are shown in Table 3:

[0138] Table 2

[0139]

[0140] See Figure 13 and Figure 14 : Figure 14 The MTF values ​​at the center of the eyelid are shown; the MTF values ​​are relatively high, all greater than 0.8. (See also...) Figure 15 The MTF value at the edge of the eye box is shown, and the MTF value can reach above 0.4. This shows that the optical module proposed in Embodiment 1 has a good MTF curve under the requirements of large eye box and large field of view. The MTF value at the edge of the eye box does not hit the bottom. The optical module provided in this embodiment is suitable for the wearing needs of more people.

[0141] Figure 15 The defocus curve at the center of the eye box is shown. Figure 15 With the above Figure 13 Correspondingly, Figure 13 The vertical line in the middle indicates the position of display screen 3. Display screen 3 can achieve a very good imaging effect when it is in this position. Figure 16 The defocus curve at the edge of the eye box is shown. Figure 16 and Figure 14Correspondingly, Figure 16 The vertical line in the middle indicates the position of the display screen. Figure 16 The image shows that the center position of the eye box has shifted, and a good defocusing effect is achieved by moving the display screen 3 at a position 7mm from the edge of the eye box. It can be seen that the MTF value decreases outside the vertical line in the middle.

[0142] According to another aspect of the embodiments of this application, a wearable device is also provided, the wearable device including a housing and an optical module as described above, the optical module being disposed in the housing.

[0143] The wearable device is, for example, a VR headset, including VR glasses or a VR helmet, etc., and this application embodiment does not impose specific limitations on it.

[0144] For example, the housing is a lens frame, and the lens frame is provided with two lens frames; the optical module is provided with two, and the two optical modules are disposed in the two lens frames.

[0145] The specific implementation of the head-mounted display device in this application can refer to the above-described embodiments of the optical module. Therefore, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be described in detail here.

[0146] The above embodiments mainly describe the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. For the sake of brevity, they will not be elaborated here.

[0147] While specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of this application. The scope of this application is defined by the appended claims.

Claims

1. An optical module characterized by comprising: The optical module comprises an imaging lens group, a light splitting element (5), a phase retarder (6) and a polarization reflection element (7) arranged in the imaging lens group; wherein the phase retarder (6) is located between the light splitting element (5) and the polarization reflection element (7); The optical module further comprises a display screen (3) arranged on one side of the imaging lens group and located on the same optical axis as the imaging lens group, and the display screen (3) is configured to be movable along the optical axis direction relative to the imaging lens group to adjust the back focal length of the optical module. The optical module satisfies: the moving distance of the display screen (3) along the optical axis direction D x and the radial distance from any position of the eyebox to the center of the eyebox x x 2 =-2 p D x d ;​​​​​​ wherein, x ∈ R , D ( x )≤ d , d is the distance from the display screen (3) to the imaging lens group corresponding to the center position of the eyebox, d >0, p is the distance from the focus of the parabola to the directrix of the parabola, p >0, the coordinates of the focus are (0, d-p / 2), and the equation of the directrix is y = p / 2+ d ; The distance the display screen (3) moves along the optical axis D ( x The spatial position of the eye box x Satisfying the following functional equation: D ( x )= p 1* x 6 + p 2* x 5 + p 3* x 4 + p 4* x 3 + p 5* x 2 + p 6* x + p 7; wherein -1.3e -07 < p 1 < -1.0e -05 , -1.2e -06 < p 2 < -1.0e -04 , -1.1e -05 < p 3 < -1.0e -03 , -1.3e -05 < p 4 < -1.0e -02 , -1.2e -05 < p 5 < -1.0e -02 , -1.1e -05 < p 6 < -1.0, 1.5 < p 7 < 50; x r = 0 characterizes the radial distance of an arbitrary position of the eyebox to the center of the eyebox, x = 0 characterizes the position of the center of the eyebox, x < 0 characterizes the spatial position of the eyebox in the negative direction with the center of the eyebox as reference point, x > 0 characterizes the spatial position of the eyebox in the positive direction with the center of the eyebox as reference point, p 7 is the distance of the imaging lens group to the display screen (3) on the side of the display screen (3).

2. The optical module according to claim 1, wherein The moving distance of the display screen (3) in the direction of the optical axis D x The radial distance from any position of the eyebox to the center of the eyebox x The function equation satisfied by the imaging optical system formed by the any surface type lens satisfies: R 2 ≥ 0.95, R 2 is a parameter representing the fitting degree.​ 3. The optical module according to claim 1, wherein The optical module further comprises an eye tracking assembly (9) arranged close to the imaging lens group. The eye tracking assembly (9) is used to acquire the eye position information of the wearer to control the distance between the display screen (3) and the imaging lens group.

4. The optical module according to claim 1, wherein The display screen (3) is used to emit circularly polarized light to the imaging lens group, and the side close to the imaging lens group of the display screen (3) is the light emitting side, and the light emitting side is provided with a screen protection device (4).

5. The optical module according to claim 1, wherein The imaging lens group comprises at least one lens, and the surface type of the lens comprises a plane, a spherical surface, an aspherical surface, a Fresnel surface or a free-form surface.

6. The optical module according to claim 1, wherein The imaging lens group comprises a first lens (1) and a second lens (2), and the second lens (2) is located between the first lens (1) and the display screen (3). The light splitting element (5) is arranged on either side of the second lens (2), and the phase retarder (6) and the polarization reflection element (7) are arranged on either side of the first lens (1).

7. The optical module according to claim 6, wherein The light splitting element (5) is arranged on the surface of the second lens (2) close to the display screen (3). The optical module further comprises a polarization element (8), and the phase retarder (6), the polarization reflection element (7) and the polarization element (8) are sequentially stacked to form a superposition element (10), and the superposition element (10) is arranged on the surface of the first lens (1) away from the display screen (3).

8. The optical module according to claim 6, wherein The fast axis direction of the light splitting element (5) forms an angle of 45 degrees with the transmission direction of the polarization reflection element (7).

9. The optical module according to claim 6 or 7, wherein The polarization direction of the polarization element (8) is the same as the polarization transmission direction of the polarization reflection element (7).

10. The optical module of claim 1, wherein The optical module satisfies: a system total length of the optical module TL The ratio of the system total length of the optical module to the aperture of the largest lens in the imaging lens group D max 0.4 < the ratio of the system total length of the optical module to the aperture of the largest lens in the imaging lens group < 0.9 TL / D max 0.4 < the ratio of the system total length of the optical module to the aperture of the largest lens in the imaging lens group < 0.9 11. The optical module of claim 1, wherein The effective focal length of the optical module EFFL For: 13mm < EFFL <33mm.

12. A wearable device, comprising: Comprise: a housing; and The optical module according to any one of claims 1-11 is arranged in the housing. ​

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