CN113219664B - Imaging optical path and head-mounted display device - Google Patents

Abstract

The invention discloses an imaging optical path and a head-mounted display device. The imaging optical path includes: an imaging lens, an imaging lens and a correction mirror group. The imaging lens is also provided with a total reflection surface, the total reflection surface is connected to the light incident surface of the imaging lens and the light exit surface of the imaging lens; Lens, the light enters through the light incident surface of the imaging lens, the incident angle of the light on the total reflection surface is greater than or equal to the critical angle of total reflection, the light is reflected to the light exit surface, and is transmitted on the light exit surface. The technical solution of the present invention can reduce the volume of the head-mounted display device directly in front of the human eyes, and is convenient for the user to wear.

Description

Imaging optical path and head-mounted display device

technical field

The invention relates to the technical field of optical display, in particular to an imaging optical path and a head-mounted display device.

Background technique

A head mounted display device is an electronic product that can provide an immersive experience. The application of head-mounted display devices has gradually expanded to medical, military, gaming and other fields. However, the current head-mounted display device is equipped with many optical devices directly in front of the user's eyes, resulting in a large volume of the head-mounted display device directly in front of the human eye, and the overall device is bloated, which is not convenient for the user to wear.

Contents of the invention

Based on this, in view of the problem that the existing head-mounted display device has more lenses directly in front of the user's eyes, resulting in a large volume of the head-mounted display device directly in front of the human eye, which is not convenient for the user to wear, it is necessary to provide a The imaging optical path and the head-mounted display device are designed to reduce the volume of the head-mounted display device directly in front of the human eye, making it easy for users to wear it.

In order to achieve the above object, the present invention proposes an imaging optical path, which includes:

An imaging lens, the imaging lens is provided with a light incident surface and a light exit surface, the light incident surface and the light exit surface are arranged at an angle, the imaging lens is also provided with a total reflection surface, and the total reflection surface is connected to the the light incident surface of the imaging lens and the light exit surface of the imaging lens; and

Correction mirror group, the correction mirror group is arranged on one side of the light incident surface of the imaging lens, the light is directed to the imaging lens through the correction mirror group, and the light enters through the light incident surface of the imaging lens , the incident angle of light on the total reflection surface is greater than or equal to the critical angle of total reflection, the light is reflected toward the light exit surface, and is transmitted through the light exit surface.

Optionally, the light-emitting surface of the imaging lens is convex, and the convex direction of the light-emitting surface of the imaging lens faces the light emitting direction of the imaging lens.

Optionally, the cut plane at the center of the light incident surface of the imaging lens is a first cut plane, the cut plane at the center of the light output surface of the imaging lens is a second cut plane, and the first cut plane and the second cut plane The direction of extension is orthogonal.

Optionally, at least one of the light incident surface of the imaging lens and the light exit surface of the imaging lens is an aspheric surface.

则满足：

Optionally, the focal power of the imaging lens is

Then satisfy:

Optionally, the correcting lens group includes a first lens, a second lens and a third lens, the first lens, the second lens and the third lens are arranged in sequence along the propagation direction of the light, and the first lens One lens is a positive lens, the second lens is a negative lens, and the third lens is a positive lens.

Optionally, the light incident surface of the first lens, the light exit surface of the first lens, the light incident surface of the second lens, the light exit surface of the second lens, the light incident surface of the third lens At least one of the surface and the light-emitting surface of the third lens is an aspheric surface.

所述第二透镜的光焦度为

所述第三透镜的光焦度为

则满足：

Optionally, the focal power of the first lens is

The focal power of the second lens is

The focal power of the third lens is

Then satisfy:

The central thickness of the imaging lens is T ₀ , the central thickness of the first lens is T ₁ , the central thickness of the second lens is T ₂ , and the central thickness of the third lens is T ₃ , then the following conditions are satisfied: 6mm< T ₀ <15mm, 1mm<T ₁ <5mm, 1mm<T ₂ <5mm, 2mm<T ₃ <5mm.

Optionally, the distance between the light incident surface of the imaging lens and the center point of the surface adjacent to the third lens is D, which satisfies: D>2mm.

In addition, in order to achieve the above object, the present invention also provides a head-mounted display device, the head-mounted display device includes a casing and an imaging optical path as described above, and the imaging optical path is arranged on the casing.

In the technical solution proposed by the present invention, the light enters through the light-incident surface of the imaging lens, the light satisfies the total reflection condition of light on the total reflection surface, the incident angle is greater than or equal to the critical angle of total reflection, and the light passes from the optically denser medium to the optically thinner medium spread. It can be seen from this that the light is totally reflected, the light is emitted through the light-emitting surface of the imaging lens, and is displayed at the position of the human eye. Since the light-incident surface and the light-exit surface are set at an angle, the direction of the light to the imaging lens can be flexibly adjusted, and other optical devices such as light sources can be installed on the side of the light-incident surface of the imaging lens, reducing the need to install directly in front of the human eye. optical instrument. Through the dispersed arrangement of optical components, the overall head-mounted display device is more concise, avoiding overall bloatedness, and is convenient for users to wear.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those skilled in the art, other drawings can also be obtained according to the structures shown in these drawings without creative effort.

Fig. 1 is the schematic structural view of an embodiment of the imaging lens in the imaging optical path of the present invention;

Fig. 2 is a structural schematic diagram of an embodiment of an imaging lens and a correction mirror group in the imaging optical path of the present invention;

Fig. 3 is a modulation transfer function diagram of an embodiment of the imaging optical path of the present invention;

Fig. 4 is a spot diagram of an embodiment of the imaging optical path of the present invention;

Fig. 5 is a field curvature and distortion diagram of an embodiment of the imaging optical path of the present invention;

Fig. 6 is a color difference diagram of an embodiment of the imaging optical path of the present invention;

Fig. 7 is a relative illuminance diagram of an embodiment of the imaging optical path of the present invention.

Explanation of reference numbers:

label name label name 10 imaging lens 220 second lens 110 Light incident surface 230 third lens 120 light emitting surface 30 the light 130 Total reflection surface 40 monitor 20 Corrective lens group 50 Protection board 210 first lens 60 human eye

The realization of the purpose of the present invention, functional characteristics and advantages will be further described in conjunction with the embodiments and with reference to the accompanying drawings.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relationship between the components in a certain posture (as shown in the accompanying drawings). Relative positional relationship, movement conditions, etc., if the specific posture changes, the directional indication will also change accordingly.

In addition, in the present invention, descriptions such as "first", "second" and so on are used for description purposes only, and should not be understood as indicating or implying their relative importance or implicitly indicating the quantity of indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of these features. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

In the present invention, unless otherwise specified and limited, the terms "connection" and "fixation" should be understood in a broad sense, for example, "fixation" can be a fixed connection, a detachable connection, or an integral body; It can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediary, and it can be an internal communication between two elements or an interaction relationship between two elements, unless otherwise clearly defined. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

In addition, the technical solutions of the various embodiments of the present invention can be combined with each other, but it must be based on the realization of those skilled in the art. When the combination of technical solutions is contradictory or cannot be realized, it should be considered as a combination of technical solutions. Does not exist, nor is it within the scope of protection required by the present invention.

In related technologies, head-mounted display devices are provided with more optical devices directly in front of the user's eyes, such as light sources and various lenses for imaging. In order to be able to accurately display images at the position of the human eye, the light must pass through a sufficiently long optical path, that is, sufficient installation space is required. As a result, the volume of the head-mounted display device directly in front of the human eye is relatively large, and the device obviously protrudes from the user's face.

In order to solve the above problems, referring to FIG. 1 and FIG. 2 , the present invention provides an imaging optical path, which includes: an imaging lens 10 and a correction lens group 20 . The imaging lens 10 is provided with a light incident surface 110 and a light exit surface 120, and the light incident surface 110 of the imaging lens 10 and the light exit surface 120 of the imaging lens 10 are arranged at an included angle. The imaging lens 10 also includes a total reflection surface 130, and the total reflection surface 130 is connected On the light incident surface 110 and the light exit surface 120 ; the angle between the light incident surface 110 of the imaging lens 10 and the light exit surface 120 of the imaging lens 10 can be an acute angle, an obtuse angle, or a mutually perpendicular relationship. The material of the imaging lens 10 can be optical plastic, which is easy to process and can be processed by injection molding. The material of the imaging lens 10 can also be optical glass, which is processed by grinding, and the optical glass has good optical properties, such as transmission and reflection.

The correcting lens group 20 is disposed on one side of the light-incident surface of the imaging lens 10 , and the light is directed to the imaging lens 10 through the correcting lens group 20 . In order to further reduce aberrations, a correcting lens group 20 is provided. The correcting lens group 20 is used to correct the focus position of the light 30 to ensure a clear image of the light 30 at the position of the human eye 60 . Reduce the occurrence of aberrations such as spherical aberration, chromatic aberration and distortion.

The light 30 enters through the light incident surface 110 of the imaging lens 10, and the light 30 enters the total reflection surface 130 through the imaging lens 10. The incident angle of the light 30 on the total reflection surface 130 is greater than or equal to the critical angle of total reflection, and the light 30 reflects to the light-emitting surface 120 of the imaging lens 10 and transmitted through the light-emitting surface 120 of the imaging lens 10 . When the light incident surface 110 of the imaging lens 10 is set at an included angle with the light exit surface of the imaging lens 10, it also satisfies that the incident angle of the light 30 total reflection surface 130 passing through the light incident surface 110 of the imaging lens 10 is greater than or equal to the total reflection surface 130. critical angle for reflection.

In addition, the imaging lens 10 in this embodiment can be used in virtual reality (VR, Virtual Reality) technology. At this time, the total reflection surface 130 can also be provided with a reflection film to improve the reflection efficiency of the light 30 .

Furthermore, the imaging lens 10 in this embodiment can also be used in Augmented Reality (AR, Augmented Reality) technology. At this time, the external light 30 can enter the interior of the head-mounted display device through the total reflection film. In order to improve the transmission of the light 30 , an anti-reflection film is provided on the total reflection surface 130 to increase the transmittance of the light 30 .

In the technical solution proposed in this embodiment, the light 30 enters through the light incident surface 110 of the imaging lens 10, the light 30 satisfies the total reflection condition of light on the total reflection surface 130, the incident angle is greater than or equal to the critical angle of total reflection, and the light 30 is formed by Optically denser media propagates to optically rarer media. It can be seen that the light 30 is totally reflected, and the light 30 is emitted through the light-emitting surface 120 of the imaging lens 10 , and is imaged at the position of the human eye 60 . Since the light incident surface 110 and the light exit surface 120 are set at an included angle, the direction in which the light 30 shoots toward the imaging lens 10 can be flexibly adjusted, and other optical devices such as light sources can be arranged on one side of the light incident surface 110 of the imaging lens 10, reducing the An optical device is arranged directly in front of the human eye 60 . Through the dispersed arrangement of optical components, the overall head-mounted display device is more concise, avoiding overall bloatedness, and is convenient for users to wear.

In the above embodiments, in order to ensure convergent imaging at the position of the human eye 60 , the light emitting surface 120 of the imaging lens 10 is a convex surface, and the convex direction of the light emitting surface 120 of the imaging lens 10 faces the light emitting direction of the imaging lens 10 . With the convex surface, when the light 30 passes through the light-emitting surface 120 of the imaging lens 10 , the light 30 is deflected toward the optical axis, and the light 30 converges at the position of the human eye 60 . Convergence on the convex surface ensures that the light 30 is focused at the position of the human eye 60 .

In the above-mentioned embodiment, the cut plane at the central position of the light incident surface 110 of the imaging lens 10 is the first cut plane, the cut plane at the central position of the light emitting surface 120 of the imaging lens 10 is the second cut plane, and the extension of the first cut plane and the second cut plane Orthogonal. In this way, the light 30 incident on the light-incident surface 110 of the imaging lens 10 is perpendicular to the extending direction of the light 30 on the light-emitting surface 120 of the imaging lens 10 . At this time, the optical device is disposed on one side of the light incident surface 110 of the imaging lens 10 , that is, the optical device is distributed on both sides of the human eye 60 . The structure of the head-mounted display device includes the position of the temples, through the two sides of the human eye 60 distributed by the optical device, the optical device can be installed on the temple position, so that not only the position directly in front of the human eye 60 can be saved, but also the Make full use of the space in the temples.

During the propagation of the light 30, the light 30 at the edge of the lens is away from the optical axis. The optical path of the light 30 is different between the position near the optical axis and the position far away from the optical axis, thus easily generating aberrations, including spherical aberration, chromatic aberration, and distortion. In order to reduce aberrations, at least one of the light incident surface of the imaging lens 10 and the light exit surface of the imaging lens 10 is an aspheric surface. Through the design of the aspheric surface, the curvature radii of the light incident surface of the imaging lens 10 and the light exit surface of the imaging lens 10 gradually change from the center position to the edge position, for example, gradually increase, or gradually decrease. By gradually changing the radius of curvature, the focus position of the light 30 located at the edge is adjusted, thereby reducing the occurrence of aberrations.

则满足：

光焦度为焦距的倒数，成像透镜10的光焦度为

在0.01至0.03之间，保证光线30经过成像透镜10完成会聚作用。In the above embodiments, in order to make the light 30 converge at the position of the human eye 60 , the imaging lens 10 is a positive lens to ensure the convergence effect of the light 30 . The focal power of the imaging lens 10 is

Then satisfy:

The focal power is the reciprocal of the focal length, and the focal power of the imaging lens 10 is

Between 0.01 and 0.03, ensure that the light 30 passes through the imaging lens 10 to complete the convergence.

In the foregoing embodiments, in order to further reduce generation of aberrations. The imaging optical path further includes a correcting lens group 20 , which is arranged on one side of the light-incident surface of the imaging lens 10 . The correcting lens group 20 is used to correct the focus position of the light 30 to ensure a clear image of the light 30 at the position of the human eye 60 . Reduce the occurrence of aberrations such as spherical aberration, chromatic aberration and distortion.

Specifically, the correcting lens group 20 includes a first lens 210, a second lens 220, and a third lens 230, and the first lens 210, the second lens 220, and the third lens 230 are arranged in sequence along the propagation direction of the light 30, and the first lens 210 is a positive lens, the second lens 220 is a negative lens, and the third lens 230 is a positive lens. Through the alternate arrangement of positive lens, negative lens and positive lens, the light 30 undergoes the process of converging, diverging and re-converging, correcting the optical path difference between the light 30 near the optical axis and the light 30 far away from the optical axis, so that the light 30 Eye 60 position focused imaging.

Further, the light incident surface of the first lens 210, the light exit surface of the first lens 210, the light incident surface of the second lens 220, the light exit surface of the second lens 220, the light incident surface of the third lens 230 and the third lens 230 At least one of the light-emitting surfaces is aspherical. Through the design of the aspheric surface, the light incident surface of the first lens 210, the light exit surface of the first lens 210, the light incident surface of the second lens 220, the light exit surface of the second lens 220, the light incident surface of the third lens 230 and the The radius of curvature of the light emitting surfaces of the three lenses 230 gradually changes from the center position to the edge position, for example, increases gradually, or decreases gradually. By gradually changing the radius of curvature, the focus position of the light 30 located at the edge is adjusted, thereby reducing the occurrence of aberrations. In this embodiment, the aspheric surface can be provided in many ways, and it can be provided only on the surface of one lens, or it can be provided on both surfaces of each lens. The greater the number of aspheric settings, the more flexible it is to adjust aberrations. Of course, the surface shape of the aspheric surface is complex, and the more complex the surface shape, the higher the processing cost. Therefore, it is possible to ensure the effect of eliminating aberrations and reduce the processing cost under the condition of setting a small number of aspheric surfaces.

第二透镜220的光焦度为

第三透镜230的光焦度为

则满足：

如此，限定了第一透镜210、第二透镜220和第三透镜230的光焦度范围，第一透镜210的光焦度

在0.05至0.10之间，第二透镜220的光焦度为

在-0.15至-0.10之间，第三透镜230的光焦度

在0.04至0.10之间，三个第一透镜210、第二透镜220和第三透镜230的光焦度在各自对应的范围内选择设置调整，从而减少像差的产生。In the above embodiment, the refractive power of the first lens 210 is

The focal power of the second lens 220 is

The focal power of the third lens 230 is

Then satisfy:

In this way, the focal power ranges of the first lens 210, the second lens 220 and the third lens 230 are defined, and the focal power of the first lens 210

Between 0.05 and 0.10, the refractive power of the second lens 220 is

Between -0.15 and -0.10, the power of the third lens 230

Between 0.04 and 0.10, the focal powers of the three first lenses 210 , the second lens 220 and the third lens 230 are selectively set and adjusted within their corresponding ranges, so as to reduce generation of aberrations.

In addition, in order to further reduce the volume, the central thickness of the imaging lens 10 is T ₀ , the central thickness of the first lens 210 is T ₁ , the central thickness of the second lens 220 is T ₂ , and the central thickness of the third lens 230 is T ₃ , Then satisfy: 6mm<T ₀ <15mm, 1mm<T ₁ <5mm, 1mm<T ₂ <5mm, 2mm<T ₃ <5mm; specifically define the center thickness of the four lenses, T ₀ , T ₁ , T ₂ and T ₃ is selected and adjusted within a corresponding range to reduce the thickness of the head-mounted display device, and at the same time help to reduce the overall volume of the head-mounted display device.

In addition, in order to improve the transmittance of light 30, on the light incident surface of the first lens 210, the light exit surface of the first lens 210, the light incident surface of the second lens 220, the light exit surface of the second lens 220, and the third lens 230 The light incident surface of the third lens 230 and the light exit surface of the third lens 230, as well as the light incident surface of the imaging lens 10 and the light exit surface of the imaging lens 10 are provided with an anti-reflection coating, and the anti-reflection coating can increase the number of light rays 30 passing through. The anti-reflection coating can be set up by sticking or coating. Paste settings, simple operation, easy to complete. The coating setting can make the film layer stronger, and the coating can improve the compactness of the film layer and increase the wear resistance of the anti-reflection film.

Furthermore, the distance between the center point of the light incident surface of the imaging lens 10 and the center point of the light exit surface of the third lens 230 is D, which satisfies: D>2mm. By limiting the distance between the light-incident surface of the imaging lens 10 and the light-emitting surface of the third lens 230, contact between the third lens 230 and the imaging lens 10 is avoided, collision friction between the two lenses is reduced, and the surfaces of the two lenses are protected. Similarly, the first lens 210 , the second lens 220 and the third lens 230 are also separated by a certain distance to protect the surfaces of the lenses.

In the above embodiment, the imaging optical path further includes the display 40 and the protective plate 50 disposed on the light emitting surface of the display 40 . The transparent protective plate 50 is arranged on the light-emitting surface of the display 40 to ensure the smooth emission of the light 30 and at the same time protect the light-emitting surface of the display 40 to prevent the light-emitting surface of the display 40 from being damaged by external forces.

In the above embodiment, the refractive index n of the first lens 210, the second lens 220, the third lens 230 and the imaging lens 10 satisfies: 1.45<n<1.60; the dispersion coefficient is v, then satisfies: 50<v <75. The refractive index is between 1.45 and 1.60, and the dispersion coefficient is between 50 and 75, which can ensure smooth imaging of the light 30 .

In an embodiment of the present application, the material of the first lens may be K26R, the material of the second lens may be EP7000, the material of the third lens may be K26R, and the material of the imaging lens may be K26R. The surface type of the aspheric surface is calculated by a formula. Specifically, the even-order aspheric surface is one of the aspheric surfaces, and the calculation surface formula of the even-order aspheric surface mainly uses the even-order aspheric surface coefficient. Specifically, the calculation formula is

Among them, z is the coordinate along the optical axis, Y is the radial coordinate, C is the curvature of each optical surface on the optical axis, k is the cone coefficient (Coin Constant), and α _i is the even-order aspheric surface of each high-order term Coefficient, 2i is the order of the aspherical coefficient (Theorder of Aspherical Coefficient), N is the number of value points. For example, α _i includes α ₁ , α ₂ and α ₃ . See Table 1 for the specific parameters of the even-order aspheric surface.

Table I

Fig. 3 is the modulation transfer function figure of imaging optical path of the present invention, namely MTF (Modulation TransferFunction) figure, MTF figure is used to refer to the relationship between the degree of modulation and the line logarithm per millimeter in the image, and is used to evaluate the ability to restore the details of the scene; Among them, the uppermost black solid line is a curve with no aberration in theory, and the closer to the black solid line, the better the imaging quality.

Fig. 4 is a spot diagram of the imaging optical path of the present invention, wherein the spot diagram refers to that after many light rays emitted by one point pass through the imaging optical path, the intersection points with the image plane are no longer concentrated at the same point due to aberration, and a spread is formed. Diffusion patterns within a certain range are used to evaluate the imaging quality of the projection optical system. The smaller the root mean square radius value and geometric radius value, the better the imaging quality. Areas 1 to 10 are arranged in order from left to right and from top to bottom. In the seventh area, it can be seen that the root mean square radius value is 6.254mm, and the geometric radius value is 18.826mm.

Fig. 5 is a field curvature and distortion diagram of the imaging optical path of the present invention, wherein the field curvature refers to the curvature of the image field, and is mainly used to indicate the degree of misalignment between the intersection point of the entire beam and the ideal image point in the imaging optical path. Distortion refers to the aberration of different parts of the object with different magnifications when the object is imaged through the imaging optical path. The distortion will cause the similarity of the object image to deteriorate, but it will not affect the clarity of the image.

Fig. 6 is a chromatic aberration diagram of the imaging optical path of the present invention, wherein, the vertical axis chromatic aberration refers to the chromatic aberration of magnification, which mainly refers to a complex-color chief ray on the object side. Because there is dispersion in the refraction system, it becomes multicolored when it exits the image side. root light.

FIG. 7 is a relative illuminance diagram of the imaging optical path of the present invention. The illuminance value measured in one viewing angle direction reflects the imaging brightness of the imaging optical path. Generally, the center brightness is high and the peripheral brightness is low.

The present invention also provides a head-mounted display device. The head-mounted display device includes a casing and an imaging optical path as described above, and the imaging optical path is arranged on the casing. The optical lens can be arranged in the casing, or the optical lens can be wrapped in a half-wrapped manner. The outer shell is used to protect the imaging optical path from damage caused by external force, and it can also play the role of dustproof and waterproof.

For the specific implementation manner of the head-mounted display device of the present invention, reference may be made to the above-mentioned embodiments of the imaging optical path, which will not be repeated here.

The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Under the inventive concept of the present invention, the equivalent structural transformation made by using the description of the present invention and the contents of the accompanying drawings, or directly/indirectly used in other All relevant technical fields are included in the patent protection scope of the present invention.

Claims (8)

1. An imaging optical path, comprising:

the imaging lens is provided with a light inlet surface and a light outlet surface, the light inlet surface and the light outlet surface form an included angle, and the imaging lens is also provided with a total reflection surface which is connected with the light inlet surface of the imaging lens and the light outlet surface of the imaging lens; and

the correcting lens group is arranged on one side of the light inlet surface of the imaging lens, light rays are emitted to the imaging lens through the correcting lens group, the light rays are emitted through the light inlet surface of the imaging lens, the incident angle of the light rays on the total reflection surface is larger than or equal to the critical angle of total reflection, and the light rays are reflected to the light outlet surface and are transmitted to the light outlet surface;

the correcting lens group comprises a first lens, a second lens and a third lens, the first lens, the second lens and the third lens are sequentially arranged along the propagation direction of light rays, the first lens is a positive lens, the second lens is a negative lens, and the third lens is a positive lens; the distance between the center point of the light incident surface of the imaging lens and the center point of the light emergent surface of the third lens is D, and the following conditions are met: d is more than 2mm; the first lens, the second lens, the third lens and the imaging lens have an abbe number v, and satisfy: v is more than 50 and less than 75.

2. The optical path as claimed in claim 1, wherein the light-emitting surface of the imaging lens is convex, and the convex direction of the light-emitting surface of the imaging lens faces the light-emitting direction of the imaging lens.

3. The imaging optical path of claim 2, wherein the tangent plane at the center of the light incident surface of the imaging lens is a first tangent plane, the tangent plane at the center of the light emergent surface of the imaging lens is a second tangent plane, and the extending directions of the first tangent plane and the second tangent plane are orthogonal.

4. The imaging optical path of claim 1, wherein at least one of the light incident surface of the imaging lens and the light emitting surface of the imaging lens is aspheric.

5. The imaging optical path of claim 1 wherein the imaging lens has an optical power of

Then:

6. the imaging optical path of claim 1, wherein at least one of the light incident surface of the first lens, the light emergent surface of the first lens, the light incident surface of the second lens, the light emergent surface of the second lens, the light incident surface of the third lens, and the light emergent surface of the third lens is aspheric.

7. The imaging optical path of claim 1, wherein the first lens has an optical power of

The second lens has an optical power of

The focal power of the third lens is

Then:

the center thickness of the imaging lens is T ₀ The center thickness of the first lens is T ₁ The center thickness of the second lens is T ₂ The center thickness of the third lens is T ₃ Then, the following are satisfied: t is more than 6mm ₀ ＜15mm，1mm＜T ₁ ＜5mm，1mm＜T ₂ ＜5mm，2mm＜T ₃ ＜5mm。

8. A head-mounted display device comprising a housing and the imaging optical path of any of claims 1 to 7, the imaging optical path being provided in the housing.

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