CN114706223A

CN114706223A - Lens group, optical module and head-mounted display device

Info

Publication number: CN114706223A
Application number: CN202210402766.7A
Authority: CN
Inventors: 郭恒琳; 鲁公涛
Original assignee: Qingdao Virtual Reality Research Institute Co ltd
Current assignee: Qingdao Virtual Reality Research Institute Co ltd
Priority date: 2022-04-15
Filing date: 2022-04-15
Publication date: 2022-07-05
Anticipated expiration: 2042-04-15
Also published as: CN114706223B

Abstract

The invention relates to the technical field of near-to-eye display, in particular to a lens group, an optical module and head-mounted display equipment. The lens group comprises at least two lenses, the at least two lenses comprise a first lens and a second lens, the first lens is a positive focal power lens, the second lens is a negative focal power lens, the lens group is a long-distance type lens group scheme, the size of a product is favorably reduced, the structure of the lens group is simple, and the lens group satisfies the relationship: 16mm < effl <39.4mm, 0.65< TL/D <2.8, wherein effl is an effective focal length value of the lens group; TL is the total length of the optical system of the lens group; d is the diameter of the largest lens in the two lenses, and the lens group meeting the conditions has the characteristic of small size, so that a single-purpose VR system is conveniently manufactured.

Description

Lens group, optical module and head-mounted display device

Technical Field

The invention relates to the technical field of near-to-eye display, in particular to a lens group, an optical module and head-mounted display equipment.

Background

With the development of computer technology, various wearable device products have come to the fore, and glasses such as AR (Augmented Reality), VR (Virtual Reality), MR (Mediated Reality), XR (medicated Reality) and the like are getting more and more attention. Wherein the monocular VR system can regard as pseudo-AR to use, has better application flexibility, and current monocular VR system size is great, for convenient dress and adaptation user's demand, and the monocular VR system needs to satisfy the performance that the size is little, and optical property is good.

The above is only for the purpose of assisting understanding of the technical solutions of the present application, and does not represent an admission that the above is prior art.

Disclosure of Invention

The invention mainly aims to provide a lens group, and aims to provide a lens group which is simple in structure, easy to manufacture and low in cost.

In order to achieve the above object, the present invention provides a lens group, which includes at least two lenses, where the at least two lenses include a first lens and a second lens, the first lens is a positive power lens, the second lens is a negative power lens, and the lens group satisfies the following relationship: 16mm < effl <39.4mm, 0.65< TL/D < 2.8;

wherein effl is an effective focal length value of the lens group; TL is the total optical system length of the lens group; d is the diameter of the largest lens in the lens group.

Optionally, if the effective focal length of the first lens is defined as f1, and the effective focal length of the second lens is defined as f2, then: 12mm < f1<32.3mm, -20mm < f2< -29 mm.

Optionally, a third lens is further disposed on a side of the second lens facing away from the first lens, where the third lens is a positive power lens, and an effective focal length f3 of the third lens is defined, then: 100< f3<200 mm.

Optionally, if the abbe number of the material of the first lens is defined as V1, the abbe number of the material of the second lens is defined as V2, and the abbe number of the material of the third lens is defined as V3, the following conditions are satisfied: v2 < V3, and V2 < V1.

Optionally, the first lens has a larger optic diameter than the second lens.

Optionally, the lens group has an entrance pupil diameter D1, satisfying the relationship: d1 is more than or equal to 2mm and less than or equal to 6 mm.

Optionally, the eyerelief of the lens group is D2, and the relation of 16mm < D2 ≦ 40mm is satisfied.

Optionally, the diagonal field of view of the lens group is FOV, satisfying the relation 14 ° < FOV <38 °.

The application still provides an optical module, optical module includes the display screen the battery of lens, the display screen transmission is used for the formation of image demonstration light extremely the battery of lens, the display screen is located the second lens deviates from one side of first lens.

The application also provides a head-mounted display device, the head-mounted display device include the casing with the optical module, the optical module is located the casing.

The technical scheme of the invention relates to a lens group, which comprises at least two lenses, wherein the at least two lenses comprise a first lens and a second lens, the first lens is a positive focal power lens, the second lens is a negative focal power lens, the lens group adopted by the invention is a long-distance type lens group, and the focal power distribution follows a positive-negative distribution mode, so that the imaging optical path is shortened, and the size of the whole lens group is reduced. The lens group satisfies the relationship: 16mm < effl <39.4mm, 0.65< TL/D < 2.8; wherein effl is an effective focal length value of the lens group; TL is the total length of the optical system of the lens group; d is the diameter of the largest lens in the lens group, and the lens group meeting the conditions is favorable for realizing a small-angle diagonal view field, is favorable for forming a smaller volume by the lens group, and is also favorable for realizing a small-size entrance pupil diameter which can improve the imaging definition of the lens group. That is, the lens group satisfying the above conditions has a small size and a clear image. And lens group simple structure conveniently makes, helps reduce cost, so, satisfies the demand that the user low-cost purchased, improves its extensive suitability.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.

FIG. 1 is a schematic view of a lens assembly according to the present invention;

FIG. 2 is a schematic diagram of an optical path of the lens assembly of FIG. 1;

FIG. 3 is a schematic view of another lens assembly of the present invention;

FIG. 4 is a schematic diagram of an optical path of the lens assembly of FIG. 3;

FIG. 5 is a two-dimensional schematic diagram of a light-emitting solid angle of a conventional self-luminous display panel;

FIG. 6 is a graph of a modulation transfer function according to a first embodiment of the present invention;

fig. 7 is a modulation transfer function graph according to a second embodiment of the present invention.

The reference numbers indicate:

reference numerals	Name (R)	Reference numerals	Name (R)
				100	Optical module	2	Second lens
10	Display screen	21	Third surface
				001	Luminous display screen	23	The fourth surface
002	Central axis	3	Third lens
				1	First lens	31	Fifth surface
11	First surface	33	The sixth surface
				13	Second surface

The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that all the directional indicators (such as up, down, left, right, front, and rear … …) in the embodiment of the present invention are only used to explain the relative position relationship between the components, the movement situation, etc. in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indicator is changed accordingly.

In the present invention, unless otherwise expressly stated or limited, the terms "connected," "secured," and the like are to be construed broadly, and for example, "secured" may be a fixed connection, a removable connection, or an integral part; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be interconnected within two elements or in a relationship where two elements interact with each other unless otherwise specifically limited. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In addition, the descriptions related to "first", "second", etc. in the present invention are only for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, the expression "and/or" as used throughout is meant to encompass three juxtaposed aspects, exemplified by "A and/or B", including either the A aspect, or the B aspect, or aspects in which both A and B are satisfied. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.

In recent years, applications of Augmented Reality (AR) technology and Virtual Reality (VR) technology to intelligent wearable electronic devices are rapidly developed, living habits of people are greatly changed, and cost performance of the intelligent wearable electronic devices becomes a relatively concerned object in order to adapt to applications of the AR technology and the VR technology in life. The core component for enhancing the display technology and the virtual display technology is a display optical system, the quality of the display effect of the display optical system directly determines the quality of the intelligent wearable electronic equipment, and meanwhile, the price cost is considered, so that the display optical system is simple in structure, easy to manufacture and low in cost, and is the design purpose of research designers.

Especially, the monocular VR system with small volume can be used as a pseudo AR, has wide application, is commonly used in information prompt occasions such as monocular head-wearing industrial operation occasions, has strong adaptability, is divided into an imaging light source and an imaging light path, and has the structural design requirements of being as simple as possible and convenient to manufacture in order to meet the low-cost purchase requirements of users and improve the wide applicability.

For this purpose, as shown in fig. 1 and fig. 2, the present invention provides a lens group, the lens group includes at least two lenses, the at least two lenses includes a first lens 1 and a second lens 2, the first lens 1 is a positive power lens, the second lens 2 is a negative power lens, the lens group adopted in the present application is a distance type lens group, the power distribution should follow a positive-negative distribution manner, so that the imaging optical path is shortened, and the size of the whole lens group is reduced. The lens group satisfies the relationship: 16mm < effl <39.4mm, 0.65< TL/D < 2.8; wherein effl is an effective focal length value of the lens group; TL is the total length of the optical system of the lens group; d is the diameter of the largest lens in the lens group, and the lens group meeting the conditions is favorable for realizing a small-angle diagonal view field, is favorable for forming a smaller volume by the lens group, and is also favorable for realizing a small-size entrance pupil diameter which can improve the imaging definition of the lens group. That is, the lens group satisfying the above conditions has a small size and a clear image. And lens group simple structure conveniently makes, helps reduce cost, so, satisfies the demand that the user low-cost bought, improves its extensive suitability.

Further, if the effective focal length of the first lens 1 is defined as f1 and the effective focal length of the second lens 2 is defined as f2, the following conditions are satisfied: 12mm < f1<32.3mm, -20mm < f2< -29 mm. The lens group satisfying the above effective focal length contributes to the design of a small-sized lens group.

Further, as shown in fig. 3 and 4, a third lens 3 is further disposed on a side of the second lens 2 facing away from the first lens 1, and the third lens 3 is a positive power lens. The third lens 3 improves the resolution of the lens group, the first lens 1 has positive focal power, the second lens 2 has negative focal power, the third lens 3 has positive focal power, and the combination of the positive focal power and the negative focal power improves the resolution. And, defining the third lens 3 to have a fifth surface 31 facing the second lens 2 and a sixth surface 33 facing away from the second lens 2, where the sixth surface 33 is a concave surface and the fifth surface 31 is a convex surface, reduces the tolerance sensitivity of the lens. The greater probability of tolerance sensitivity is related to greater curvature, which is more sensitive. The generally less curved concave or flat surfaces help to reduce sensitivity, i.e., the sixth surface 33 may also be flat, reducing tolerance sensitivity. Defining the effective focal length f3 of the third lens 3, then: 100mm < f3<200 mm. The lens group satisfying the above effective focal length contributes to the design of a small-sized lens group.

Further, when the abbe number of the material of the first lens 1 is defined as V1, the abbe number of the material of the second lens 2 is defined as V2, and the abbe number of the material of the third lens 3 is defined as V3, the following conditions are satisfied: v2 < V3, and V2 < V1. The first lens 1, the second lens 2 and the third lens 3 are made of the lens materials, the abbe number of the first lens is required to follow a large-small-large material distribution mode, so that the chromatic aberration of the light path is corrected, and the chromatic aberration is eliminated, so that when the lens group is applied to a display screen 10 for imaging, light rays emitted by the display screen 10 in a full wave band have a good imaging effect.

It is understood that the first lens 1, the second lens 2, and the third lens 3 are aspheric lenses; the aspheric lens eliminates phase difference and improves imaging quality.

It is understood that the first lens element 1, the second lens element 2 and the third lens element 3 are made of plastic material. The plastic material is light and difficult damaged, alleviates the weight of battery of lens, conveniently dresses.

Further, as shown in fig. 1, the first lens 1 has a larger lens diameter than the second lens 2. Since the light is emitted from the second lens 2 to the first lens 1 and the light is diverged from the second lens 2 to the first lens 1, the lens diameter of the first lens 1 is larger than that of the second lens 2.

Further, the entrance pupil diameter of the lens group is D1, satisfying the relationship: d1 is more than or equal to 2mm and less than or equal to 6 mm. D1 can be 2mm, 3mm, 4mm, 5mm, 6mm, the smaller the entrance pupil diameter, the sharper the image seen by the human eye.

Furthermore, the eyerelief of the lens group is D2, and the relation that D2 is more than 16mm and less than or equal to 40mm is satisfied. Eyerelief in this range is advantageous for designing a small-sized lens group. D2 is the eye distance Eyerelief of the optical module, D2 may be 16mm, 18mm, 20mm, 25mm, 28mm, 30mm, 35mm, 38mm, 40mm, for example, if the size of the entrance pupil diameter D1 is not changed from the diagonal FOV of the lens set, the larger the Eyerelief of the optical module is, the smaller the lens diameter of the first lens 1 is required, which facilitates the design of a small-sized optical module.

Further, the diagonal field of view of the lens group is FOV, satisfying the relation 14 ° < FOV <38 °. The diagonal field of view is similar to a rectangle, the diagonal field of view has a long side and a short side, and the diagonal field of view is the field of view with the length of the diagonal.

The application still provides an optical module 100, its characterized in that, optical module 100 includes display screen 10 and battery of lens, and the light that display screen 10 transmission is used for the formation of image to show to the battery of lens, and one side that second lens 3 deviates from first lens 2 is located to display screen 10. Since the lens group adopts all technical solutions of all the above embodiments, at least all the beneficial effects brought by the technical solutions of the above embodiments are achieved, and no further description is given here.

It can be understood that the optical module 100 includes a display 10 and a lens assembly, the display 10 is a self-luminous light source, the display 10 emits light for image display, and the display 10 is a self-luminous light source, so the display 10 can be as close to the lens assembly as possible to reduce the overall volume of the optical system. Moreover, the lens group adopted in the present application is a long-distance type lens group, and the power distribution should follow a positive-negative distribution mode, so that the imaging optical path is shortened, which is helpful for reducing the size of the whole optical module 100. The lens group comprises a first lens 1 and a second lens 2, the second lens 2 is arranged in the light emitting direction of the display screen 10, the second lens 2 is provided with a fourth surface 23 facing the display screen 10 and a third surface 21 back to the display screen 10, at least one of the fourth surface 23 and the third surface 21 is a concave surface, the first lens 1 is arranged on one side of the second lens 2 departing from the display screen 10, the first lens 1 is provided with a second surface 13 facing the second lens 2 and a first surface 11 back to the second lens 2, the second surface 13 is a convex surface, and the first surface 11 is a convex surface, so that the optical power distribution follows a positive-negative distribution mode.

In an embodiment, the eye distance Eyerelief of the optical module 100 is D2, which satisfies the relationship of 16mm < D2 ≤ 40mm, the diagonal field of view of the lens group satisfies the relationship of 14 ° < FOV <38 °, and the diagonal field of view is within this range, which helps the optical module 100 form a smaller volume, the beam diameter D1 of the incident beam of the lens group entering the imaging area, D1 is the entrance pupil diameter of the optical module, which satisfies the relationship of 2mm ≤ D1 ≤ 6 mm. The relationship satisfied by the entrance pupil diameter D1 improves the imaging clarity of the optical module 100, and the entrance pupil diameter within this range is favorable for optimally setting the maximum diameter of the lens. The entrance pupil diameter of the optical module 100, the Eyerelief of the optical module, and the diagonal field of view of the lens group are matched to form an optical module with small size and clear imaging.

Further, D2 is eye distance Eyerelief of the optical module, D2 may be 16mm, 18mm, 20mm, 25mm, 28mm, 30mm, 35mm, 38mm, 40mm, for example, if the size of the entrance pupil diameter D1 is unchanged from the diagonal field of view FOV of the lens group, the larger Eyerelief of the optical module is, the smaller lens diameter of the first lens 1 is required, which facilitates designing the small-sized optical module 100.

The diagonal field of view of the lens group is such that the FOV satisfies the relation 14 ° < FOV <38 °, wherein the diagonal field of view is like a rectangle with long sides having short sides and diagonal with the diagonal being the field of view of the length of the diagonal.

D1 is the entrance pupil diameter of the optical module, satisfies the relation 2 mm-D1-6 mm, D1 can be 2mm, 3mm, 4mm, 5mm, 6mm, the smaller the entrance pupil diameter, the clearer the image seen by human eyes.

Moreover, the optical module 100 only needs two lenses and one display screen 10, has a simple structure, is convenient to manufacture, and is beneficial to reducing the cost, so that the requirement of low-cost purchase of a user is met, and the wide applicability of the optical module is improved. The entrance pupil diameter, the Eyerelief of the optical module 100, and the diagonal field of view of the lens group are associated with each other when the small size is satisfied, for example, if the entrance pupil diameter size and the diagonal field of view of the lens group are not changed, the larger the Eyerelief of the optical module 100 is, the smaller the required lens diameter of the first lens 1 will be, for example, the Eyerelief may be D2>30mm, which is beneficial to reducing the lens diameter of the first lens 1, and in order to comprehensively consider the small size and the imaging quality of the optical module 100, the above parameters are used to optimize the performance of the optical module 100.

As shown in fig. 1 and fig. 3, the total optical length of the optical module 100 is defined as TL, the first lens 1 is the largest lens, the diameter of the first lens 1 is defined as D, and the total optical length and the diameter of the first lens 1 satisfy: TL/D is more than 0.65 and less than 2.8 mm. The diagonal field of view of the lens group and the Eyerelief of the optical module are satisfied by designing the total optical length and the lens diameter of the first lens 1 within the above range, FOV <38 ° is 14 ° < 16mm < D2 ≦ 40mm, and thus, the small size of the optical module 100 is achieved.

Defining the total effective focal length of the lens group as effl, it is satisfied that 16mm < effl <39.4 mm. The total effective focal length is within this range, facilitating the design of small-sized optical module 100. It can be understood that the effective focal length is equal to the half-image height of the display screen/tan diagonal half-field, when designing the optical module, the size of the selected diagonal field FOV and the display screen is fixed, the effective focal length can be calculated, the lens is designed according to the effective focal length and the given required entrance pupil diameter, and the lens diameter size is equal to (eye distance, eyepupil) × tan (FOV) + entrance pupil diameter.

Defining the TV distortion of the lens group as TVD, satisfying the condition that TVD < 1%. That is, the distortion of the TV is less than 1% by the arrangement of the lens group, and the distortion is the aberration with different magnifications at different parts of the object when the object is imaged by the image display structure, and the distortion will cause the similarity of the object image to be deteriorated, but does not affect the definition of the image. The TV distortion is less than 1%, the distortion is small, and the TV meets the design regulation.

As shown in fig. 3 and 4, the lens assembly further includes a third lens 3, the third lens 3 is disposed on a side of the second lens 2 facing the display screen 10, the third lens 3 has a sixth surface 33 facing the display screen 10 and a fifth surface 31 facing away from the display screen 10, and at least one of the sixth surface 33 and the fifth surface 31 is a convex surface. The third lens 3 improves the resolution of the optical module 100, the second lens 2 has negative focal power, the third lens 3 has positive focal power, and the combination of the positive focal power and the negative focal power improves the resolution. Moreover, the sixth surface 33 is a concave surface, and the fifth surface 31 is a convex surface, so that tolerance sensitivity of the lens is reduced. The greater probability of tolerance sensitivity is related to greater curvature, which is more sensitive. The generally less curved concave or flat surfaces help to reduce sensitivity, i.e., the sixth surface 33 may also be flat, reducing tolerance sensitivity.

Defining the abbe number of the material of the first lens 1 as V1, the abbe number of the material of the second lens 2 as V2, and the abbe number of the material of the third lens 3 as V3, then the following conditions are satisfied: v2 < V3, and V2 < V1. The abbe numbers of the first lens 1, the second lens 2 and the third lens 3 are required to follow a large-small-large material distribution mode to correct chromatic aberration of a light path and eliminate chromatic aberration, so that light rays emitted by the display screen 10 in a full-wave band all have a good imaging effect.

The second lens 2, the first lens 1 and the third lens 3 are aspheric lenses; the aspheric lens eliminates phase difference and improves imaging quality.

The second lens element 2, the first lens element 1 and the third lens element 3 are made of plastic material. The plastic material is light and not easy to be damaged, reduces the weight of the optical module 100, and is convenient to wear.

And, defining the effective focal length of the first lens 1 as f1, the effective focal length of the second lens 2 as f2, and the effective focal length of the third lens 3 as f3, then: 12mm < f1<32.3mm, -20mm < f2< -29mm, 100mm < f3<200 mm; the three lenses satisfying the above effective focal lengths contribute to the design of a small-sized optical module.

The light emitted by the display screen 10 for imaging display is defined as visible light, and the wavelength range of the visible light is 400nm-700 nm. Since the optical module 100 of the present application eliminates chromatic aberration, it is suitable for the display screen 10 emitting color light, and the imaging effect is improved.

Further, a first embodiment of the present invention is shown in table one, which is the performance and parameters of the optical module of the first embodiment. The second surface 13 and the first surface 11 of the first lens 1 are convex surfaces, the fourth surface 23 and the third surface 21 of the second lens 2 are concave surfaces, the sixth surface 33 of the third lens 3 is concave surface, and the fifth surface 31 is convex surface; the effective focal length of the first lens 1 is f 1-19.12 mm, the effective focal length of the second lens 2 is f 2-26.223 mm, and the effective focal length of the third lens 3 is f 3-169.445 mm; the total effective focal length of the lens group is effl ═ 29.43 mm; the total optical length of the optical module is TL which is 33.5 mm; the entrance pupil diameter of the optical module is D1-5 mm; the included angle between the central axis of the light angle of the display screen 10 and the principal ray is less than 2 degrees, the size of the used display 10 is 10.85mm 6.16mm, and the wavelength of the light emitted by the display 10 is that the MTF of the full wave short full field of view of the visible light is more than 0.4@45 lp/mm.

Watch 1

Performance of	Parameter(s)
		Diameter of entrance pupil	5mm
EFFL	29.4mm
		Size of display screen	10.85mm*6.16mm
Luminous wavelength of display screen	Visible light full wave band
		Distortion of TV	<1％
Full field MTF	＞0.4@45lp/mm
		Angle of distant heart	<2°
Number of lenses	3P

As shown in fig. 5, it is difficult for the current Display optical system to satisfy the requirements of small size, high Light efficiency, and uniform screen brightness, and referring to fig. 5, most of the Display screens 10 adopted by the current Display optical system are self-luminous Display screens 001, such as Liquid Crystal Displays (LCDs), Organic Light-emitting diodes (OLEDs), and the central axis 002 of the Light-emitting solid angle a of the self-luminous Display screen 001 is perpendicular to the surface of the self-luminous Display screen 001, and the Light-emitting intensity is different from each other in different Light-emitting angles, that is, the Light-emitting intensity is smaller as the distance from the central axis 002 is larger. In this application, the central axis of the light-emitting angle of the display screen 10 and the included angle between the chief rays are smaller than 2 °, so that the light-emitting intensity of the optical module 100 is ensured to be better, and the brightness of the picture is uniform.

As shown in fig. 6, it is a modulation Transfer Function graph of the present embodiment, i.e. MTF modulation Transfer Function graph, where the MTF graph is used to refer to the relationship between modulation degree and per millimeter line logarithm in an image, and is used to evaluate the detail reduction capability of a scene; the MTF value of each field is higher than 0.4, so that the image definition of the system imaged under each field is better.

Specifically, the parameters of the three lenses are shown in table two below, for example.

Watch two

Further, as shown in table three, the second embodiment of the invention is the performance and parameters of the optical module of the embodiment. The second surface 13 and the first surface 11 of the first lens 1 are convex surfaces, the fourth surface 23 and the third surface 21 of the second lens 2 are concave surfaces, the sixth surface 33 of the third lens 3 is concave surface, and the fifth surface 31 is convex surface; the effective focal length f1 of the first lens 1 is 20.3mm, the effective focal length f2 of the second lens 2 is-29.3 mm, and the effective focal length f3 of the third lens 3 is 199.7 mm; the total effective focal length of the lens group is effl ═ 18.92 mm; the total optical length of the optical module is TL which is 29.71 mm; the entrance pupil diameter of the optical module is D1-4 mm; the angle between the central axis of the light angle of the display screen 10 and the chief ray is less than 2 deg.. The display 10 used has dimensions of 7.68mm 4.32mm and the wavelength of light emitted by the display 10 is such that the visible full-wave short full-field MTF > 0.3@45 lp/mm.

Watch III

As shown in fig. 7, it is a modulation Transfer Function graph of the present embodiment, i.e. MTF modulation Transfer Function graph, where the MTF graph is used to refer to the relationship between the modulation degree and the logarithm of each millimeter line in an image, and is used to evaluate the detail reduction capability of a scene; the MTF value of each field is higher than 0.3, so that the image definition of the system imaged under each field is better.

Specifically, the parameters of the three lenses are shown in table four below, for example.

Watch four

The application also provides a head-mounted display device, which comprises a shell and an optical module 100, wherein the optical module 100 is arranged on the shell. Optical module 100 sets up in the shell, and the shell can effectual protection optical module 100, avoids reducing the dust and falls into optical module 100, can also reduce moisture infiltration and avoid optical module 100 malfunctioning in to optical module 100. Since the optical module 100 adopts all technical solutions of all the above embodiments, at least all the beneficial effects brought by the technical solutions of the above embodiments are achieved, and are not described in detail herein.

The above is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent structural changes made by using the contents of the specification and the drawings, or any other related technical fields directly/indirectly using the inventive concept are included in the scope of the present invention.

Claims

1. A lens group comprising at least two lenses including a first lens and a second lens, the first lens being a positive power lens and the second lens being a negative power lens, the lens group satisfying the relationship: 16mm < effl <39.4mm, 0.65< TL/D < 2.8;

2. The lens assembly of claim 1, wherein defining the effective focal length of the first lens as f1 and the effective focal length of the second lens as f2 satisfies: 12mm < f1<32.3mm, -20mm < f2< -29 mm.

3. The lens group of claim 2, wherein a third lens is further disposed on a side of the second lens facing away from the first lens, the third lens is a positive power lens, and an effective focal length f3 of the third lens is defined such that: 100mm < f3<200 mm.

4. The lens group of claim 3, wherein the abbe number of the material defining the first lens is V1, the abbe number of the material defining the second lens is V2, and the abbe number of the material defining the third lens is V3, then: v2 < V3, and V2 < V1.

5. A lens stack according to claim 3, characterised in that the first lens has a larger optic diameter than the second lens.

6. A lens stack according to any one of claims 1 to 5, characterized in that the lens stack has an entrance pupil diameter D1, satisfying the relation: d1 is more than or equal to 2mm and less than or equal to 6 mm.

7. A lens stack as claimed in any one of claims 1 to 5, characterized in that the eyerelief of the lens stack is D2, satisfying the relation 16mm < D2 ≦ 40 mm.

8. A lens stack according to any one of claims 1 to 5, characterized in that the diagonal field of view of the lens stack is FOV, satisfying the relation 14 ° < FOV <38 °.

9. An optical module, comprising a display screen and the lens assembly of any one of claims 1 to 8, wherein the display screen emits light for image display to the lens assembly, and the display screen is disposed on a side of the second lens facing away from the first lens.

10. A head-mounted display device, comprising a housing and the optical module of claim 9, wherein the optical module is disposed on the housing.