Optical system and display device

Abstract

The invention provides an optical system and a display device. The optical system comprises a lens structure, a transflective film and a reflective polarizing film, the transflective film and the reflective polarizing film are arranged on the lens structure, image light transmitted by the transflective film is configured to be folded back between the transflective film and the reflective polarizing film and is emitted from the reflective polarizing film, and the lens structure comprises at least one lens. The optical system further comprises a calibration lens located on the side, away from the reflective polarizing film, of the transflective film, and the optical axis of the lens structure does not pass through the calibration lens. The focal length of one of the lens structure and the calibration lens is a positive value, the focal length of the other one is a negative value, and the calibration lens comprises at least one free-form surface, so that the degree of freedom of optical system design is improved, non-centrality caused by the lens structure is effectively corrected, aberration generated by an off-axis optical system is corrected, and the imaging quality is improved; the camera calibration process is simplified, and the sight tracking and iris recognition precision is improved.

Description

Technical Field

[0001] This disclosure relates to an optical system and a display device. Background Technology

[0002] Currently, near-eye display devices, such as virtual reality (VR) or augmented reality (AR) displays, use lenses to magnify the images displayed on the screen, giving users a sense of immersion. Near-eye display devices also incorporate eye-tracking (ET) devices, such as sensors, to capture user eye information and calculate the user's gaze. Summary of the Invention

[0003] This disclosure provides an optical system and a display device.

[0004] The optical system provided in this disclosure includes: a lens structure and a transmissive reflective film and a reflective polarizing film disposed on the lens structure. Image light transmitted through the transmissive reflective film is configured to be reflected back between the transmissive reflective film and the reflective polarizing film, and exits from the reflective polarizing film. The lens structure includes at least one lens. The optical system also includes a calibration lens located on the side of the transmissive reflective film away from the reflective polarizing film. The optical axis of the lens structure does not pass through the calibration lens. One of the lens structure and the calibration lens has a positive focal length, and the other has a negative focal length. The calibration lens includes at least one freeform surface.

[0005] For example, according to an embodiment of this disclosure, the focal length of the lens structure is negative, and the focal length of the calibration lens is positive.

[0006] For example, according to an embodiment of this disclosure, the maximum radius of curvature of the freeform surface is less than the minimum radius of curvature of the surface of the lens structure closest to the calibration lens.

[0007] For example, according to an embodiment of this disclosure, the focal length of the freeform surface in a first direction perpendicular to the optical axis of the lens structure and the focal length of the freeform surface in a second direction perpendicular to the optical axis are both positive and negative, the first direction is perpendicular to the second direction, and the first direction is configured to be perpendicular to the line connecting the two eyeballs.

[0008] For example, according to an embodiment of this disclosure, the angle between the optical axis of the freeform surface and the optical axis of the lens structure is 15 to 45 degrees.

[0009] For example, according to an embodiment of this disclosure, at least the surface of the calibration lens closest to the lens structure is a freeform surface.

[0010] For example, according to an embodiment of this disclosure, the optical system further includes a camera and a light source, the camera being located on the side of the transflective coating away from the reflective polarizing coating. The optical axis of the lens structure does not pass through the camera and the light source, and the camera is configured to acquire an eye image; the camera includes a camera lens, the angle between the optical axis of the camera lens and the optical axis of the lens structure being 15 to 45 degrees.

[0011] For example, according to an embodiment of this disclosure, the light source is located on the side of the transflective film away from the reflective polarizing film; the calibration lens is located between the camera and at least one of the light source and the lens structure.

[0012] For example, according to an embodiment of this disclosure, a calibration lens is disposed between the camera and the lens structure, and the calibration lens is configured such that light emitted from the light source converges at the optical center of the camera after passing through the lens structure and the calibration lens.

[0013] For example, according to an embodiment of this disclosure, the calibration lens is a structure within the camera.

[0014] For example, according to an embodiment of this disclosure, the optical axis of at least one surface of the calibration lens, other than the freeform surface, coincides with the optical axis of the camera lens.

[0015] For example, according to an embodiment of this disclosure, the surface of the calibration lens closest to the lens structure is a freeform surface, and an aspherical surface is provided on the side of the freeform surface away from the lens structure, and the optical axis of the aspherical surface coincides with the optical axis of the camera lens.

[0016] For example, according to an embodiment of this disclosure, a calibration lens is disposed between the light source and the lens structure.

[0017] For example, according to an embodiment of this disclosure, the optical system further includes a phase retardation film and a linear polarization film located on the lens structure, wherein the phase retardation film is located on the side of the transmissive polarization film facing the reflective polarization film, and the linear polarization film is located on the side of the reflective polarization film away from the transmissive polarization film.

[0018] Another embodiment of this disclosure provides a display device including a display screen and any of the above-described optical systems. The display screen is located on the side of the transflective film away from the lens structure.

[0019] For example, according to an embodiment of this disclosure, the image light incident on the transflective film from the display screen does not pass through the calibration lens. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of this disclosure and are not intended to limit this disclosure.

[0021] Figure 1A This is a schematic diagram of a partial cross-sectional structure of an optical system.

[0022] Figure 1B for Figure 1A The image sharpness modulation transfer function curve of light within the eyebox region shown is displayed in the camera.

[0023] Figure 1C for Figure 1A The distortion diagram of the optical system shown.

[0024] Figure 2 This is a partial cross-sectional structural diagram of an optical system provided according to an embodiment of the present disclosure.

[0025] Figure 3 This is a schematic diagram of an optical system provided according to an example embodiment of the present disclosure.

[0026] Figure 4A for Figure 3 The image sharpness modulation transfer function curve of light within the eyebox region shown is displayed in the camera.

[0027] Figure 4B for Figure 3 The distortion diagram of the optical system shown.

[0028] Figure 5 This is a partial structural schematic diagram of a display device provided according to another embodiment of the present disclosure.

[0029] Figure 6 This is a partial structural schematic diagram of an optical system provided according to another example of an embodiment of the present disclosure.

[0030] Figure 7 and Figure 8 This is a partial structural diagram of an optical system in different examples of embodiments of the present disclosure. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. Based on the described embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0032] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as “comprising” or “including” mean that an element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0033] Unless otherwise specified in the following embodiments of this disclosure, the quantity of a component is implied to mean that the component may be one or more, or can be understood as at least one. "At least one" means one or more, and "more" means at least two.

[0034] Near-eye display devices, such as virtual reality display devices, use ultra-short focal length folded optical paths (Pancake), which helps to greatly reduce the distance between the near-eye display device and the eyeball, thus making the near-eye display device lighter and thinner.

[0035] Near-eye display devices can employ gaze-tracking technology, such as 2D or 3D gaze-tracking. For example, 2D tracking technology, represented by the pupil-corneal reflection method, uses a vector formed by the pupil center and the corneal bright spot to represent the gaze direction. 3D tracking technology uses dual or multiple cameras to obtain the coordinates of various reference points in 3D space for gaze tracking. Using the pupil-corneal reflection method requires the camera to accurately capture and reflect the eye's position and movement information to ensure high system accuracy and reliability.

[0036] Generally, two important prerequisites for ensuring the accuracy of pupil-corneal resolution methods include camera model and camera calibration. If the camera model is accurate enough, the resolution results can match the actual situation. Camera calibration ensures that the camera can correctly map three-dimensional points from the real world onto a two-dimensional image, eliminating lens distortion and other errors, thereby improving the system's accuracy and reliability. Through precise camera calibration, the system can more accurately calculate and track the user's gaze direction.

[0037] Figure 1A This is a schematic diagram of a partial cross-sectional structure of an optical system. (Example) Figure 1AAs shown, the optical system includes a pancake lens 01, a camera 02, and a light source 03. The pancake lens 01 includes at least one lens and multiple optical films, such as a transflective film, a reflective polarizing film, a phase retardation film, and a linear polarizing film (not shown). The transflective film is located between the reflective polarizing film and the camera 02. The phase retardation film is located on the side of the transflective film away from the camera 02. The linear polarizing film is located on the side of the reflective polarizing film away from the transflective film. The light transmitted through the transflective film is configured to be folded back between the transflective film and the reflective polarizing film to achieve optical path folding. Finally, the light exits to the eyeball through the reflective polarizing film and the linear polarizing film 800.

[0038] like Figure 1A As shown, light emitted by light source 03 shines on the eye, and camera 02 captures the light reflected by the eye to achieve eye tracking.

[0039] Figure 1A The eye box area 04 is schematically shown. When there is no pancake lens 01 between the eye and the camera 02, the camera 02 satisfies the pinhole model. The light in the eye box area 04 can converge at the optical center of the camera 02, thereby forming a clear image.

[0040] Figure 1B for Figure 1A The image sharpness modulation transfer function (MTF) curve of light within the eyebox region shown is displayed in the camera. Figure 1B The diagram shows the modulation transfer function (MTF) values ​​of the optical system at different spatial frequencies for the meridians 021-026 (shown as solid lines in the diagram) under different fields of view, and the modulation transfer function values, such as MTF values, for the sagittal lines 011-016 (shown as dashed lines in the diagram) under different fields of view at different spatial frequencies. Figure 1B As shown, when the cutoff frequency is 81 line pairs / mm (lp / mm), the modulation transfer function value under the edge field of view is no greater than 0.2, and the modulation transfer function value under the center field of view is no greater than 0.6.

[0041] Figure 1C for Figure 1A The diagram shows the distortion of the optical system. Distortion is a parameter in an optical system and a significant factor limiting the accuracy of optical measurements. It represents the degree of distortion in the image formed by the optical system relative to the object itself. Figure 1C It shows Figure 1A The degree of distortion in the optical system is shown; for example, the distortion produced by the optical system is abrupt. For instance, the image produced by the optical system exhibits barrel distortion, and the distortion is significant, requiring distortion correction.

[0042] During the research, the inventors of this application discovered that: Figure 1AAs shown, after the pancake lens 01 is set in the near-eye display device, the camera 02 is placed off-axis relative to the pancake lens 01. If the camera 02 is located at the edge of the module lens barrel, the camera 02 will be affected by the refractive properties of the pancake lens 01 during the process of receiving light. For example, the backward extension line 05 of the light from the eye box area 04 captured by the camera 02 after passing through the pancake lens 01 cannot converge to a point, which will cause many problems.

[0043] For example, aberrations in the light incident on the camera reduce sharpness, leading to decreased iris texture, pupil edge sharpness, and spot sharpness, thus affecting the difficulty and accuracy of the algorithm task. For example, the camera's optical center is not fixed; images at different depths at the eye box position exhibit different distortions. Compared to pinhole imaging, camera calibration requires collecting data from more different poses, and there are significant errors in the surrounding area. For example, although the camera's physical model can solve some calibration problems, non-centrality still affects the stability of gaze estimation and entrance pupil position (EPP) accuracy estimation tasks; the algorithm still relies on the pinhole model assumption in practical applications. The traditional imaging model is described as a pinhole camera model where light passes through a small hole to form an image. That is, ideally, all light rays converge at a single point, the camera's optical center. The aforementioned non-centrality refers to the light rays not converging at the camera's optical center. Therefore, light incident on the camera, after refraction through the pancake lens, affects the accuracy of camera calibration, ET and EPP positions, and iris recognition.

[0044] The off-axis optical system consisting of a pancake lens and camera is a non-rotationally symmetric structure, making it difficult to correct asymmetric aberrations. Traditional spherical and aspherical surfaces are rotationally symmetric, limiting their ability to correct asymmetric aberrations. Therefore, spherical and aspherical surfaces are used in... Figure 1A In the off-axis optical system shown, the performance of the optical system is still limited.

[0045] This disclosure provides an optical system and a display device. The optical system includes a lens structure and a transflective coating and a reflective polarizing coating disposed on the lens structure. Image light transmitted through the transflective coating is configured to be reflected back between the transflective coating and the reflective polarizing coating and exit from the reflective polarizing coating. The lens structure includes at least one lens. The optical system also includes a calibration lens located on the side of the transflective coating away from the reflective polarizing coating. The optical axis of the lens structure does not pass through the calibration lens. One of the lens structure and the calibration lens has a positive focal length, and the other has a negative focal length. The calibration lens includes at least one freeform surface.

[0046] The optical system provided in this disclosure, by setting a calibration lens with a freeform surface and setting the focal length of the calibration lens and the lens structure, introduces a freeform surface with complex and variable surface shape into the optical system, which increases the degree of freedom in the design of the optical system, effectively corrects the non-centrality caused by the lens structure, and corrects the aberrations generated by the off-axis optical system, thereby improving the imaging quality, simplifying the camera calibration process, and improving the accuracy of eye tracking and iris recognition.

[0047] The optical system and display device provided in the embodiments of this disclosure are described below with reference to the accompanying drawings.

[0048] Figure 2 This is a partial cross-sectional structural diagram of an optical system provided according to an embodiment of the present disclosure.

[0049] like Figure 2 As shown, the optical system includes a lens structure 100 and a transflective coating 200 and a reflective polarizing coating 300 disposed on the lens structure 100. Image light transmitted through the transflective coating 200 is configured to be reflected back between the transflective coating 200 and the reflective polarizing coating 300, and exits from the reflective polarizing coating 300. The lens structure 100 includes at least one lens. For example, the transflective coating 200 is located on the light-incident side of the optical system, and the reflective polarizing coating 300 is located on the light-outceasing side of the optical system.

[0050] Figure 2 The lens structure 100 is schematically illustrated, comprising a lens with a transflective coating 200 and a reflective polarizing coating 300 located on different surfaces of the lens. For example, the transflective coating 200 may be deposited on one surface of the lens, and the reflective polarizing coating 300 may be adhered to another surface of the lens or to another optical film on that surface using optical adhesive. However, the lens structure 100 may also include multiple lenses, with the transflective coating 200 and the reflective polarizing coating 300 located on two different surfaces of the same lens, or on the surfaces of different lenses. For example, the surfaces of the lenses in the lens structure 100 may be spherical or aspherical.

[0051] For example, such as Figure 2 As shown, the transflective membrane 200 is configured to transmit part of the light and reflect another part of the light. For example, the transflective membrane 200 may include at least one film layer, such as each film layer having a thickness of 10-200 nanometers. For example, the transflective membrane 200 may have a transmittance of 50% and a reflectance of 50%. For example, the transflective membrane 200 may have a transmittance of 60% and a reflectance of 40%. For example, the transflective membrane 200 may have a transmittance of 65% and a reflectance of 35%. The embodiments disclosed herein are not limited thereto; the transmittance and reflectance of the transflective membrane 200 may be set according to product requirements.

[0052] For example, such as Figure 2As shown, the reflective polarizing film 300 is configured to reflect linearly polarized light with one characteristic and transmit linearly polarized light with another characteristic. For example, the reflective polarizing film 300 functions as follows: within the plane of the film layer, there exists a transmission axis direction in which the transmittance of the polarization component of incident light parallel to this transmission axis direction (e.g., s-polarized light) is greater than the transmittance of the polarization component perpendicular to this transmission axis direction (e.g., p-polarized light), and the reflectance of the polarization component parallel to this transmission axis direction (e.g., s-polarized light) is less than the reflectance of the polarization component perpendicular to this transmission axis direction (e.g., p-polarized light). For example, the reflective polarizing film 300 can also be called a polarizing beam splitter. For example, the transmittance of polarized light parallel to the transmission axis direction of the reflective polarizing film 300 is not less than 85%, and is not less than 90%, and is not less than 95%, and is not less than 98%; the reflectance of polarized light perpendicular to the transmission axis direction of the reflective polarizing film 300 is not less than 85%, and is not less than 90%, and is not less than 95%, and is not less than 98%.

[0053] In some examples, such as Figure 2 As shown, the optical system also includes a phase retardation film 700 and a linear polarization film 800 located on the lens structure 100. The phase retardation film 700 is located on the side of the transmissive film 200 facing the reflective polarization film 300, and the linear polarization film 800 is located on the side of the reflective polarization film 300 away from the transmissive film 200.

[0054] For example, such as Figure 2 As shown, when the lens structure 100 includes a lens, the transflective coating 200 is located on the first surface of the lens; the phase retardation coating 700 is located on the second surface of the lens, such as the phase retardation coating 700 being bonded to the second surface of the lens by optical adhesive; the reflective polarizing coating 300 is located on the side of the phase retardation coating 700 away from the second surface, such as the reflective polarizing coating 300 being bonded to the surface of the phase retardation coating 700 away from the lens by optical adhesive; and the linear polarizing coating 800 is bonded to the surface of the reflective polarizing coating 300 away from the phase retardation coating 700 by optical adhesive.

[0055] For example, such as Figure 2 As shown, the phase retardation film 700 is configured to allow transmitted light to switch between circular and linear polarization states. For example, the phase retardation film 700 can be a quarter-wave plate. For example, the angle between the slow axis of the phase retardation film 700 and the transmission axis of the reflective polarizing film 300 is 45 degrees.

[0056] The embodiments disclosed herein are not limited thereto. The phase retardation film may be located on the side of the reflective polarizing film away from the transmissive polarizing film, and the material of the phase retardation film may include a liquid crystal polymer.

[0057] For example, such as Figure 2As shown, the transmission axis of the linear polarizing film 800 coincides with the transmission axis of the reflective polarizing film 300. The linear polarizing film 800 can be used to further filter other stray light, allowing only polarized light (such as s-polarized light) that passes through the linear polarizing film 800 to enter the eyeball.

[0058] For example, such as Figure 2 As shown, the transflective film 200 and the reflective polarizing film 300 serve as two reflective surfaces, providing an ultra-short focal length folded optical path (Pancake). The arrangement of the transflective film 200 and the reflective polarizing film 300 enables the folding of light, so that the focal length of the original light-transmitting structure is folded due to the addition of, for example, two reflections caused by the arrangement of the reflective polarizing film 300 and the transflective film 200. This greatly compresses the space required between the eyeball and the optical system, thereby making the optical system smaller and thinner.

[0059] like Figure 2 As shown, the optical system also includes a calibration lens 400, located on the side of the transflective film 200 away from the reflective polarizing film 300, and the optical axis OA1 of the lens structure 100 does not pass through the calibration lens 400.

[0060] like Figure 2 As shown, one of the lens structure 100 and the calibration lens 400 has a positive focal length, and the other has a negative focal length, and the calibration lens 400 includes at least one freeform surface.

[0061] Compared to introducing aspherical or spherical surfaces into an optical system, this disclosure introduces freeform surfaces with complex and variable surface types into the optical system, increasing the degree of freedom in optical system design. At the same time, by setting the focal lengths of the calibration lens and lens structure to be positive and negative complementary, the non-centrality caused by the lens structure and the aberrations generated by the off-axis optical system are effectively corrected, improving image quality, simplifying the camera calibration process, and improving the accuracy of eye tracking and iris recognition.

[0062] When the above lens structure includes a single lens, the focal length of the lens structure is the focal length of that single lens, such as if the lens is a positive or negative lens; when the above lens structure includes multiple lenses, the focal length of the lens structure is the focal length of the multiple lenses as a whole structure, such as if the whole structure is equivalent to a positive or negative lens.

[0063] When the aforementioned calibration lens includes a single lens, the focal length of the calibration lens is the focal length of that single lens, such as if the lens is a negative lens or a positive lens; when the aforementioned calibration lens includes multiple lenses, the focal length of the calibration lens is the focal length of the multiple lenses as a calibration structure, such as if the calibration structure is equivalent to a negative lens or a positive lens.

[0064] In some examples, such as Figure 2As shown, the angle between the optical axis OA2 of the freeform surface and the optical axis OA1 of the lens structure 100 is 15 to 45 degrees. The freeform surface can be an off-axis structure relative to the lens structure 100.

[0065] For example, such as Figure 2 As shown, the angle between the optical axis OA2 of the freeform surface and the optical axis OA1 of the lens structure 100 is 18 to 42 degrees. For example, the angle between the optical axis OA2 of the freeform surface and the optical axis OA1 of the lens structure 100 is 20 to 30 degrees. For example, the angle between the optical axis OA2 of the freeform surface and the optical axis OA1 of the lens structure 100 is 25 to 35 degrees. In this embodiment, the angle between the optical axis OA2 of the freeform surface and the optical axis OA1 of the lens structure 100 will not be listed individually; the angle between the optical axis OA2 of the freeform surface and the optical axis OA1 of the lens structure 100 can be any angle between 15 and 45 degrees. The angle between the optical axis OA2 of the freeform surface and the optical axis OA1 of the lens structure 100 is related to the position of the camera 500 (described later), and the angle between the optical axis of the freeform surface and the optical axis of the lens structure 100 can be adjusted according to the relative positional relationship between the camera 500 and the lens structure 100.

[0066] For example, such as Figure 2 As shown, the eye box region 901 can be an area with a certain size in the X direction, Y direction, and Z direction perpendicular to both directions. For example, the size in the X, Y, and Z directions can all be 25 mm. The camera 500 is used to capture light within this eye box region. The Z direction mentioned above is the direction perpendicular to the paper surface.

[0067] In some examples, such as Figure 2 As shown, the focal length of lens structure 100 is negative, and the focal length of calibration lens 400 is positive. For example, lens structure 100 can be equivalent to a negative lens, and calibration lens 400 can be equivalent to a positive lens.

[0068] Lens structure 100 has a diverging effect on light, while calibration lens 400 has a converging effect on light. As a compensation lens for lens structure 100, calibration lens 400 can converge the diverged light by lens structure 100 to a certain extent, which is beneficial for correcting the non-centrality caused by lens structure 100.

[0069] In some examples, such as Figure 2As shown, the maximum radius of curvature of the freeform surface in the compensation lens is smaller than the minimum radius of curvature of the surface closest to the calibration lens 400 in the lens structure 100. The smaller the radius of curvature of the freeform surface, the better the optimization effect of non-centrality. For example, the surface closest to the calibration lens 400 in the lens structure 100 can be aspherical or spherical. When the surface is aspherical, the largest value among the multiple radii of curvature included in the freeform surface is smaller than the smallest value among the multiple radii of curvature included in the aspherical surface; when the surface is spherical, the largest value among the multiple radii of curvature included in the freeform surface is smaller than the radius of curvature of the sphere.

[0070] In some examples, such as Figure 2 As shown, the focal length of the freeform surface in a first direction (e.g., the Y direction) parallel to the optical axis of the lens structure 100 and the focal length of the freeform surface in a second direction perpendicular to the optical axis (e.g., the direction perpendicular to the paper) are both positive and negative. The first and second directions are perpendicular, and the first direction is configured to be perpendicular to the line connecting the two eyeballs. When the user uses this optical system, the line connecting the two eyeballs is parallel to the second direction. The direction perpendicular to the paper refers to the direction perpendicular to the XY plane, such as the direction pointing inwards into the paper. By setting the focal length in the Y direction on the axis to a positive value, it is beneficial to gather more light from within the eyebox. The X direction remains on the optical axis, and to achieve the same eyebox range, a negative focal length also improves the sharpness in the X direction.

[0071] For example, such as Figure 2 As shown, the focal length of the freeform surface perpendicular to the paper plane plays a converging role. The focal length of the freeform surface perpendicular to the paper plane is larger than the focal length in the Y direction, which is beneficial for converging light rays from different directions.

[0072] In some examples, such as Figure 2 As shown, the focal length of lens structure 100 is f1, and the focal length of calibration lens 400 is f2. f1 and f2 are strongly correlated.

[0073] Compared to Figure 1AAs shown, a pancake lens 01 is placed between the eye and the camera 02, which causes the backward extension line 05 of the light rays captured by the camera 02 after passing through the pancake lens 01 to not converge to a single point. The optical system provided in this disclosure adjusts the deflection direction of the light rays emitted from the lens structure 100 to other structures, such as the camera 500, by setting a calibration lens 400, so that the backward extension line 902 of the light rays captured by the camera 500 after passing through the lens structure 100 and the calibration lens 400 can converge to a single point. As a compensation lens for the lens structure 100, the calibration lens 400, by setting the focal length of the lens structure 100 and the calibration lens 400, can make the overall structure of the calibration lens 400 combined with the lens structure 100 approximate a flat plate structure. This reduces the degree of refraction of light reflected from the eye to the camera 500, so that the light passing through the eye box area 901 is in the eye box area of ​​the pinhole camera 500 and can converge to a point, so that the camera 500 meets the pinhole model. This is beneficial to improving the accuracy of the camera 500 calibration process and the process of capturing the position of the eye box area. Moreover, the light in the eye box area can form a clear image on the sensor of the camera 500.

[0074] In some examples, such as Figure 2 As shown, at least the surface of the calibration lens 400 closest to the lens structure 100 is a freeform surface. By designing the surface of the calibration lens 400 closest to the lens structure 100 as a freeform surface, it is beneficial to simplify the compensation matching between the freeform surface and the lens structure 100, and to specifically compensate for the aberrations generated by the lens structure 100.

[0075] For example, such as Figure 2 As shown, the surface of the lens structure 100 closest to the calibration lens 400 is a first convex surface convex towards the calibration lens 400, and the surface of the calibration lens 400 closest to the lens structure 100 is a second convex surface convex towards the lens structure 100. For example, when both the lens structure 100 and the calibration lens 400 include only one lens, the greater the curvature of the first convex surface, the greater the curvature of the second convex surface.

[0076] Figure 3 This is a schematic diagram of an optical system provided according to an example embodiment of the present disclosure.

[0077] In some examples, such as Figure 3As shown, the optical system also includes a camera 500 and a light source 600. The camera 500 is located on the side of the transmissive coating 200 away from the reflective polarizing coating 300. The optical axis of the lens structure 100 does not pass through the camera 500 and the light source 600. The camera 500 is configured to acquire images of the eye, such as tracking the eyeball. The camera 500 includes a camera lens 510, and the angle between the optical axis of the camera lens 510 and the optical axis of the lens structure 100 is 15 to 45 degrees. For example, the camera lens 510 is tilted relative to the lens structure 100 to collect light from the eye box area. By adjusting the angle between the camera lens 510 and the optical axis of the light-transmitting structure, the camera 500 can collect light from the eye box area without affecting the imaging of the lens structure 100.

[0078] For example, such as Figure 3 As shown, the camera 500 and the light source 600 are placed off-axis relative to the lens structure 100, so that the camera 500, the lens structure 100 and the light source 600 form an off-axis system.

[0079] For example, such as Figure 3 As shown, the angle between the optical axis of the camera lens 510 and the optical axis of the lens structure 100 can be 20 to 30 degrees. For example, the angle between the optical axis of the camera lens 510 and the optical axis of the lens structure 100 can be 25 to 35 degrees. In this embodiment, the angle between the optical axis of the camera lens 510 and the optical axis of the lens structure 100 will not be listed one by one, and the angle between the optical axis of the camera lens 510 and the optical axis of the lens structure 100 can be any angle between 15 and 45 degrees.

[0080] For example, such as Figure 3 As shown, camera 500 can be a webcam, such as a color webcam or an infrared webcam. For example, light source 600 can be a light-emitting diode (LED). For example, light source 600 can be an infrared light source 600.

[0081] For example, there can be multiple cameras 500 to capture light reflected from the eyeball from different angles. For example, the camera 500 also includes a sensor 520 located on the side of the camera lens 510 away from the calibration lens 400, and the light refracted and converged by the camera lens 510 is imaged on the surface of the sensor 520.

[0082] In some examples, such as Figure 3 As shown, the light source 600 is located on the side of the transflective coating 200 away from the reflective polarizing coating 300, and the calibration lens 400 is located between the camera 500 and at least one of the light source 600 and the lens structure 100. This embodiment is described with the light source located on the side of the transflective coating away from the reflective polarizing coating as an example, but it is not limited to this; the light source may also be located on the side of the reflective polarizing coating away from the transflective coating.

[0083] In some examples, such as Figure 3 As shown, a calibration lens 400 is disposed between the camera 500 and the lens structure 100. The calibration lens 400 is configured such that light emitted from the light source 600 converges at the optical center of the camera 500 after passing through the lens structure 100 and the calibration lens 400. For example, the optical center of the camera 500 refers to the geometric center of the camera lens 510.

[0084] Light emitted from the light source does not refract as it passes through the lens structure and the optical coating layer on it. For example, light emitted from the light source is transmitted through the lens structure and then enters the eyeball. The light reflected by the eyeball passes through the lens structure and the calibration lens and is then received by the camera.

[0085] In the optical system provided in this disclosure, by setting a calibration lens, light can be focused to the optical center of the camera to realize a pinhole imaging model, which is beneficial to the camera calibration process. Moreover, the light from the eye box area can form a clear image on the camera sensor. For example, the position of the virtual image of the camera through the lens structure remains unchanged when viewed from different angles.

[0086] By setting a calibration lens with a free-form surface, the performance of a camera that matches the lens structure can be significantly improved, such as increasing the accuracy of line-of-sight estimation, entrance pupil position (EPP) accuracy, iris recognition accuracy, enhancing the accuracy of pupil-corneal resolution methods, and reducing calibration difficulty.

[0087] In some examples, such as Figure 3 As shown, the optical axis of at least one surface of the calibration lens 400, excluding the freeform surface, coincides with the optical axis of the camera lens 510. For example, the surface of the calibration lens 400 near the camera 500 is an aspherical surface, and the optical axis of the aspherical surface coincides with the optical axis of the camera lens 510 to facilitate the matching of the calibration lens 400 and the camera lens 510 and the installation of the calibration lens 400. For example, the freeform surface, relative to the aspherical surface and the optical axis of the camera lens 510, can be an off-axis structure to facilitate optical compensation of the camera 500 when it is in an off-axis state.

[0088] In some examples, such as Figure 3 As shown, the surface of the calibration lens 400 closest to the lens structure 100 is a freeform surface, and an aspherical surface is provided on the side of the freeform surface away from the lens structure 100. The optical axis of the aspherical surface coincides with the optical axis of the camera lens 510. For example, there is one calibration lens 400, with the surface of the calibration lens 400 closest to the lens structure 100 being a freeform surface and the surface of the calibration lens 400 away from the lens structure 100 being an aspherical surface.

[0089] By setting the surface of the calibration lens closest to the lens structure as a freeform surface to correct the non-centrality and aberration problems caused by the lens structure, while setting the surface of the calibration lens furthest from the lens structure as an aspherical surface, it is beneficial to reduce the manufacturing difficulty of the calibration lens and facilitate the matching of the calibration lens with the camera in terms of physical structure.

[0090] For example, the surface of the calibration lens 400 away from the lens structure 100 can be an even-order aspherical surface. For example, the calibration lens 400 can be mounted on the camera 500. For example, both the calibration lens 400 and the camera lens 510 can be circular lenses, and the ratio of their diameters is 0.9 to 1.1.

[0091] Of course, the embodiments disclosed herein are not limited to this. The surface of the calibration lens away from the lens structure can also be a spherical or freeform surface, which can be set according to product requirements.

[0092] For example, such as Figure 3 As shown, there is at least one camera 500, and the number of calibration lenses 400 is not less than the number of cameras 500, such that at least one calibration lens 400 is provided between each camera 500 and the lens structure 100. For example, there are two cameras 500, and one calibration lens 400 is provided between each camera 500 and the lens structure 100.

[0093] For example, the lens structure 100 can be an axisymmetric structure. When different cameras 500 are symmetrically distributed with respect to the optical axis of the lens structure 100, the freeform surfaces in different calibration lenses 400 are also symmetrically distributed with respect to the optical axis. For example, if different cameras 500 are not symmetrically distributed with respect to the optical axis of the lens structure 100, the parameter characteristics of the freeform surfaces in the calibration lens 400 are set according to the relative positional relationship between the cameras 500 and the lens structure 100.

[0094] Figure 4A for Figure 3 The image sharpness modulation transfer function (MTF) curve of light within the eyebox region shown is displayed in the camera. Figure 4A The diagram shows the modulation transfer function (MTF) values ​​of the optical system at different spatial frequencies for meridians 121-126 (shown as solid lines in the figure) under different fields of view, and the modulation transfer function values, such as MTF values, for the sagitta lines 111-116 (shown as dashed lines in the figure) under different fields of view at different spatial frequencies. Figure 4A As shown, at a cutoff frequency of 81 line pairs / mm (lp / mm), the modulation transfer function (MJF) value at the edge field of view is not less than 0.6, and the MJF value at the center field of view is not less than 0.8. Compared to Figure 1AThe modulation transfer function of the optical system shown in this disclosure is larger, resulting in higher resolution.

[0095] Figure 4B for Figure 3 The distortion diagram of the optical system shown. Figure 4B It shows Figure 3 The degree of distortion of the optical system shown, for example, compared to Figure 1A The optical system shown produces abrupt distortion, while the optical system provided in this embodiment produces smooth distortion without abrupt changes.

[0096] Figure 5 This is a partial structural schematic diagram of a display device provided according to another embodiment of the present disclosure.

[0097] like Figure 5 As shown, the display device includes a display screen 10 and the aforementioned optical system, with the display screen 10 located on the side of the transflective film 200 away from the lens structure 100.

[0098] For example, such as Figure 5 As shown, the display screen 10 is located on the light-incident side of the optical system. The image light emitted from the display screen 10 is reflected between the transflective film 200 and the reflective polarizing film 300, and then transmitted to the eyeball 904 through the reflective polarizing film 300. For example, the eyeball 904 is located in the eye box area.

[0099] In some examples, such as Figure 5 As shown, the image light 903 incident on the display screen 10 onto the transflective film 200 does not pass through the calibration lens 400.

[0100] By setting a certain distance between the calibration lens and the reflective film, and between the calibration lens and the camera, and by ensuring that the calibration lens is not located in the optical path from the image light of the display screen to the lens structure, it is possible to effectively correct the non-centrality and aberration problems caused by the lens structure to the camera while avoiding the calibration lens affecting the image of the lens structure to the user. This improves the optical performance of the camera, enhances the accuracy of the pupil-cornea solution method, simplifies the camera calibration process, and improves the accuracy of eye tracking and iris recognition.

[0101] For example, such as Figure 5 As shown, the display surface of the display screen 10 is located on the focal plane of the light-incident side of the optical system.

[0102] For example, such as Figure 5 As shown, the display screen 10 can be any type of display screen, such as a liquid crystal display screen, an inorganic light-emitting diode display screen, a quantum dot display screen, a projector (such as an LCOS micro projector), etc.

[0103] For example, the display device can be a virtual reality (VR) display device. For instance, a virtual reality display device can be a display device employing an ultra-short-throw folded optical path.

[0104] For example, the display device can be a near-eye display device, such as a wearable VR helmet, VR glasses, helmet display device (HMD), head-up display device (HUD), etc., and the embodiments disclosed herein are not limited thereto.

[0105] Figure 6 This is a partial structural schematic diagram of an optical system provided according to another example of an embodiment of the present disclosure. Figure 6 The optical system shown is Figure 3 The difference in the optical system shown is that the calibration lens 400 is located inside the camera 500, as if the calibration lens 400 is a structure inside the camera 500.

[0106] For example, such as Figure 6 As shown, the calibration lens 400 is located between the camera lens 510 and the lens structure 100.

[0107] The optical system provided in this example enables the integrated design of the camera 500 by incorporating the calibration lens 400 inside the camera 500, which helps to reduce the size of the optical system.

[0108] For example, such as Figure 6 As shown, the optical axis of at least one other surface outside the freeform surface in the calibration lens 400 coincides with the optical axis of the camera lens 510.

[0109] Figure 6 The lens structure 100 and the optical film layer disposed on the lens structure 100 in the optical system shown are Figure 3 The lens structure 100 and the optical film layer disposed on the lens structure 100 in the optical structure shown have the same characteristics, which will not be described again here.

[0110] Figure 6 The light source 600, the camera lens 510 in the camera 500, and the sensor shown can be connected to... Figure 3 The light source 600, the camera lens 510 in the camera 500, and the sensor shown have the same characteristics, which will not be described again here.

[0111] Figure 6 The optical system shown can be applied to Figure 5 The display device shown.

[0112] Figure 7 and Figure 8 This is a partial structural diagram of an optical system in different examples of embodiments of the present disclosure. Figure 7 and Figure 8The optical system shown is Figure 3 The difference in the optical system is that the position of the calibration lens 400 is different.

[0113] In some examples, such as Figure 7 As shown, a calibration lens 400 is disposed between the light source 600 and the lens structure 100. For example, the principal ray of the light source 600 is off-center from the center of the calibration lens 400 by less than 3 mm. For example, the optical axis of the calibration lens 400 can pass through the center of the light source.

[0114] Compared to optical systems that do not have a calibration lens between the light source and the lens structure, such as Figure 1A In the optical system shown, the backward extensions of light rays incident on the eyeball through the lens structure do not converge to a single point. Figure 7 In the optical system shown, by setting a calibration lens 400 between the light source 600 and the lens structure 100, it is beneficial to adjust the backward extension lines to converge to a point, so as to adjust the light emitted from the light source 600 to better illuminate the eye box area and improve the accuracy of the light reflected from the eyeball to the camera 500.

[0115] For example, such as Figure 7 As shown, the position of the light source 600 is relatively fixed when viewed from different angles, such as the backward extensions of light rays from different angles intersecting at the same point.

[0116] For example, such as Figure 7 As shown, there are multiple light sources 600, and at least one calibration lens 400 is disposed between each light source 600 and the lens structure 100. For example, one calibration lens 400 is disposed between each light source 600 and the lens structure 100. For example, when different light sources 600 are symmetrically distributed with respect to the optical axis of the lens structure 100, the freeform surfaces in the calibration lens 400 are also symmetrically distributed with respect to the optical axis. For example, when different light sources 600 are not symmetrically distributed with respect to the optical axis of the lens structure 100, the parametric characteristics of the freeform surfaces in the calibration lens 400 are set according to the relative positional relationship between the camera 500 and the lens structure 100.

[0117] For example, Figure 7 The focal length of the calibration lens 400 and lens structure 100 shown is either positive or negative.

[0118] For example, such as Figure 7As shown, the surface of the calibration lens 400 facing the lens structure 100 can be a freeform surface, and the surface of the calibration lens 400 facing the light source 600 can be an aspherical surface. This helps to reduce the manufacturing difficulty of the calibration lens 400 and facilitates the physical matching between the calibration lens 400 and the light source 600. Of course, the embodiments disclosed herein are not limited to this; the surface of the calibration lens 400 away from the lens structure 100 can also be a spherical or freeform surface, which can be set according to product requirements.

[0119] For example, such as Figure 7 As shown, the surface of the lens structure 100 closest to the calibration lens 400 is a first convex surface convex towards the calibration lens 400, and the surface of the calibration lens 400 closest to the lens structure 100 is a third convex surface convex towards the lens structure 100. For example, when both the lens structure 100 and the calibration lens 400 include only one lens, the greater the curvature of the first convex surface, the greater the curvature of the third convex surface.

[0120] Figure 7 The lens structure 100 and the optical film layer disposed on the lens structure 100 in the optical system shown are Figure 3 The lens structure 100 and the optical film layer disposed on the lens structure 100 in the optical structure shown have the same characteristics, which will not be described again here.

[0121] Figure 7 The light source 600, the camera lens 510 in the camera 500, and the sensor shown can be connected to... Figure 3 The light source 600, the camera lens 510 in the camera 500, and the sensor shown have the same characteristics, which will not be described again here.

[0122] Figure 7 The optical system shown can be applied to Figure 5 The display device shown. Image light incident on the transflective film 200 does not pass through the calibration lens 400 between the light source 600 and the light-transmitting structure.

[0123] Figure 8 The optical system shown is Figure 7 The difference in the optical system shown is that a calibration lens 400 is provided between the camera 500 and the lens structure 100. Figure 8 The calibration lens 400 between the light source 600 and the lens structure 100 shown can be... Figure 7 The calibration lens 400 between the light source 600 and the lens structure 100 has the same characteristics, which will not be described again here. Figure 8 The calibration lens 400 between the camera 500 and the lens structure 100 shown can be... Figure 3 The calibration lens 400 between the camera 500 and the lens structure 100 shown has the same characteristics, which will not be described again here.

[0124] By placing calibration lenses between the light source and the lens structure, as well as between the camera and the lens structure, it is beneficial to improve the adjustment of light received and reflected in the eye box area, thereby improving camera calibration and image quality.

[0125] Figure 8 The lens structure 100 and the optical film layer disposed on the lens structure 100 in the optical system shown are Figure 3 The lens structure 100 and the optical film layer disposed on the lens structure 100 in the optical structure shown have the same characteristics, which will not be described again here.

[0126] Figure 8 The light source 600, the camera lens 510 in the camera 500, and the sensor shown can be connected to... Figure 3 The light source 600, the camera lens 510 in the camera 500, and the sensor shown have the same characteristics, which will not be described again here.

[0127] Figure 8 The optical system shown can be applied to Figure 5 The display device shown.

[0128] The following points need to be explained:

[0129] (1) The accompanying drawings of the embodiments of this disclosure only involve the structures involved in the embodiments of this disclosure, and other structures can be referred to the general design.

[0130] (2) Where there is no conflict, features of the same embodiment and different embodiments of this disclosure may be combined with each other.

[0131] The above description is merely an exemplary embodiment of this disclosure and is not intended to limit the scope of protection of this disclosure, which is determined by the appended claims.

Claims

1. An optical system, comprising: The lens structure includes a transmissive reflective film and a reflective polarizing film disposed on the lens structure. Image light transmitted through the transmissive reflective film is configured to be reflected back between the transmissive reflective film and the reflective polarizing film, and exits from the reflective polarizing film. The lens structure includes at least one lens. The optical system further includes a calibration lens located on the side of the transflective film away from the reflective polarizing film, and the optical axis of the lens structure does not pass through the calibration lens; The lens structure and the calibration lens have a positive focal length and a negative focal length, and the calibration lens includes at least one freeform surface.

2. The optical system according to claim 1, wherein, The focal length of the lens structure is negative, while the focal length of the calibration lens is positive.

3. The optical system according to claim 1, wherein, The maximum radius of curvature of the freeform surface is less than the minimum radius of curvature of the surface closest to the calibration lens in the lens structure.

4. The optical system according to claim 1, wherein, The focal length of the freeform surface in a first direction perpendicular to the optical axis of the lens structure and the focal length of the freeform surface in a second direction perpendicular to the optical axis are both positive and negative. The first direction is perpendicular to the second direction and is configured to be perpendicular to the line connecting the two eyeballs.

5. The optical system according to claim 1, wherein, The angle between the optical axis of the freeform surface and the optical axis of the lens structure is 15 to 45 degrees.

6. The optical system according to claim 1, wherein, At least the surface closest to the lens structure in the calibration lens is a freeform surface.

7. The optical system according to any one of claims 1-6, further comprising: A camera and a light source, wherein the camera is located on the side of the transflective coating away from the reflective polarizing coating. Wherein, the optical axis of the lens structure does not pass through the camera and the light source, and the camera is configured to acquire an eye image; The camera includes a camera lens, and the angle between the optical axis of the camera lens and the optical axis of the lens structure is 15 to 45 degrees.

8. The optical system according to claim 7, wherein, The light source is located on the side of the transmissive film away from the reflective polarizing film; The calibration lens is located between the camera and at least one of the light source and the lens structure.

9. The optical system according to claim 8, wherein, The calibration lens is disposed between the camera and the lens structure. The calibration lens is configured such that the light emitted by the light source converges at the optical center of the camera after passing through the lens structure and the calibration lens.

10. The optical system according to claim 7, wherein, The calibration lens is a structure inside the camera.

11. The optical system according to claim 7, wherein, The optical axis of at least one surface of the calibration lens, excluding the freeform surface, coincides with the optical axis of the camera lens.

12. The optical system according to claim 11, wherein, The surface closest to the lens structure in the calibration lens is a freeform surface, and an aspherical surface is provided on the side of the freeform surface away from the lens structure. The optical axis of the aspherical surface coincides with the optical axis of the camera lens.

13. The optical system according to claim 8, wherein, The calibration lens is disposed between the light source and the lens structure.

14. The optical system according to any one of claims 1-6, further comprising: A phase retardation film and a linear polarization film are located on the lens structure, wherein the phase retardation film is located on the side of the transmissive polarization film facing the reflective polarization film, and the linear polarization film is located on the side of the reflective polarization film away from the transmissive polarization film.

15. A display device comprising a display screen and an optical system according to any one of claims 1-14, wherein, The display screen is located on the side of the reflective film away from the lens structure.

16. The display device according to claim 15, wherein, The image light incident on the transflective film from the display screen does not pass through the calibration lens.

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