CN220773343U

CN220773343U - Polarization folding short-focus eyepiece and light and thin near-to-eye display equipment

Info

Publication number: CN220773343U
Application number: CN202322510789.2U
Authority: CN
Inventors: 孙佳平; 侯起超; 汪冬华
Original assignee: Dejia Intelligent Photoelectric Zhenjiang Co ltd
Current assignee: Dejia Intelligent Photoelectric Zhenjiang Co ltd
Priority date: 2023-09-15
Filing date: 2023-09-15
Publication date: 2024-04-12
Anticipated expiration: 2033-09-15

Abstract

The utility model discloses a polarization folding short-focus eyepiece and a light and thin near-to-eye display device, which comprises a first lens, a second lens, an absorption type polaroid, a first quarter wave plate, a light splitting film, a second quarter wave plate and a reflective polaroid, wherein the first lens, the second lens, the absorption type polaroid, the first quarter wave plate, the light splitting film, the second quarter wave plate and the reflective type polaroid are coaxially arranged along the optical axis direction from an exit pupil side to a display image source side; the polarization transmission directions of the absorption type polaroid and the reflection type polaroid are orthogonal; the first linear polarized light transmitted through the reflective polarizer is folded between the reflective polarizer and the light splitting film, is partially converted into second linear polarized light, and then is transmitted through the absorption polarizer, the second lens and the first lens to be emitted to the exit pupil position; the first lens is a convex lens, the second lens is a concave lens, the focal length range of the first lens is 50 mm-100 mm, the focal length range of the second lens is-150 mm-350 mm, and the aperture ratio of the first lens to the second lens is 0.35-0.6. The polarization folding short-focus eyepiece can be well adapted to a display image source with the angle between 6cm and 10 cm.

Description

Polarization folding short-focus eyepiece and light and thin near-to-eye display equipment

Technical Field

The utility model relates to a polarization folding short-focus eyepiece, and simultaneously relates to a light and thin near-to-eye display device comprising the polarization folding short-focus eyepiece, belonging to the field of head-mounted display devices.

Background

Virtual Reality (VR) technology is a brand new practical technology developed in the 20 th century. The virtual reality technology comprises a computer, electronic information and simulation technology, and the basic implementation mode is that the computer simulates a virtual environment so as to bring the sense of environmental immersion. The display of virtual reality technology needs to be achieved by means of VR near-eye display devices.

In the mainstream VR optical scheme at present, the aspheric direct-transmission optical system has the problems of heavy volume, uneven image surface illuminance, pupil swimming (pupil swimming) and the like under the design requirements of a large field of view and a large exit pupil diameter; the fresnel lens can reduce the thickness and weight of the lens to some extent, but the overall length of the optical system is not reduced, and there is significant "ringing" and the imaging quality is poor.

At present, the polarization folding short-focus eyepiece based on the polarization technology can better meet the requirements. However, current polarization folding short focus eyepieces are developed primarily based on small screens below 1inch in size, and do not fit well into large screens beyond 1inch in size, especially screens beyond 2 inches in screen size, such as into cell phone screens. Also, in the prior art, in order to realize large-size imaging, when a small-size screen is used, a large incident angle of the principal ray at the edge of the screen is required to be adapted to the eyepiece system, resulting in poor luminance uniformity.

Disclosure of Invention

In view of the above problems, the present utility model proposes a polarization folding short-focus eyepiece suitable for a large screen, and at the same time provides a light and thin near-to-eye display device using the polarization folding short-focus eyepiece.

In order to solve the technical problems, the utility model adopts the following technical scheme:

a polarization fold short Jiao Mujing suitable for use in a display image source having a diagonal dimension between 6cm and 10 cm; comprising the following optical devices coaxially arranged in the optical axis direction from the exit pupil side to the image source side: the optical element comprises a first lens, a second lens, an absorption type polarizer, a first quarter-wave plate, a light splitting film, a second quarter-wave plate and a reflective polarizer;

wherein the reflective polarizer is used for transmitting the first linear polarized light and reflecting the second linear polarized light, and the absorption type polarizer is used for absorbing the first linear polarized light and transmitting the second linear polarized light; the polarization directions of the first linear polarized light and the second linear polarized light are orthogonal; the polarization transmission directions of the absorption type polaroid and the reflection type polaroid are orthogonal;

the first linearly polarized light transmitted by the reflective polarizing plate is folded between the reflective polarizing plate and the light splitting film, the polarization state is changed, and part of light changed into second linearly polarized light is refracted through the second lens and the first lens after being transmitted by the absorption polarizing plate and then is emitted to the exit pupil position;

the first lens close to the exit pupil side is a convex lens, the second lens far away from the exit pupil side is a concave lens, the surface of the second lens facing the image source side is a concave surface, the focal length range of the first lens is 50 mm-100 mm, the focal length range of the second lens is-150 mm-350 mm, and the ratio of the light transmission caliber of the first lens to that of the second lens is 0.35-0.6.

Optionally, the absorption polarizer is disposed on a surface of the second lens near the display image source, and the first quarter-wave plate and the light splitting film are disposed close to the absorption polarizer.

Optionally, the reflective polarizer is disposed adjacent to the display image source, and the second quarter wave plate is disposed adjacent to the reflective polarizer.

Optionally, another polarizer is disposed between the reflective polarizer and the display image source to reduce ghost images and flare.

Optionally, the incidence angle of the principal ray of the display image source is within the range of-10 degrees to 10 degrees.

Optionally, the second lens is concave with a radius of curvature greater than 300mm on the side close to the screen.

Optionally, at least one of the surface patterns of the first lens and the second lens is aspheric.

Optionally, the first lens has a center thickness of 2mm to 10mm, an edge thickness of 2mm to 4mm, the second lens has a center thickness of 2mm to 4mm, an edge thickness of 2mm to 8mm, and a distance between the first lens and the second lens is 0 to 3mm.

Optionally, the polarization folding short focal eyepiece has an F number of 5< F <10,

the total optical length of the polarization folding short-focus eyepiece is TTL, and the TTL is less than or equal to 25mm and less than or equal to 40mm;

the optical path folding eyepiece meets at least two of the following conditions: the angle of view is greater than 80 degrees, the diameter of the exit pupil is 5 mm-10 mm, and the distance of the exit pupil is 15 mm-20 mm.

A lightweight, thin, near-to-eye display device having a polarization folded short-focus eyepiece, further comprising a display element for displaying an image and providing light of a first polarization to one side of the polarization folded short-focus eyepiece; the controller controls the display of the image on the display element according to the received image signal; the position between the display element and the second lens is adjustable, and the distance L between the surface of the second lens facing the display element and the screen light-emitting surface of the display element on the optical axis is adjusted within 10-25mm, so that the 0D-5D range visibility adjustment of the polarization folding short Jiao Mujing to a visual observer is realized.

Optionally, the display element is a micro liquid crystal display device capable of emitting light of a first polarization; or the display element is a micro display device which does not emit polarized light, and the surface of the display device facing to one side of the polarization folding short-focus eyepiece is provided with a polarizing layer which is arranged separately or integrally formed with the display element.

The polarization folding short-focus eyepiece provided by the utility model has the advantages of large exit pupil diameter, large field angle, high imaging brightness uniformity, compact and light and thin structure, suitability for large screens with the diagonal size of 2-6 inches, and low requirement on the residual internal stress of the lens on the processing and manufacturing difficulty. The system is light and miniaturized, and simultaneously has the requirements of large view field and large exit pupil range, and can realize low-cost and mass production through an injection molding process, thereby particularly meeting the requirements of near-to-eye display equipment.

Drawings

FIG. 1 is a longitudinal cross-sectional block diagram of a polarization folded short-focus eyepiece;

fig. 2 is a schematic diagram of the polarization principle of a polarization folded short-focus eyepiece.

Detailed Description

The technical scheme of the utility model is further described in detail below with reference to the attached drawings and specific embodiments.

The utility model provides a polarization folding short-focus eyepiece, which comprises two lenses, an absorptive polarizing film, a first quarter wave plate, a light splitting film, a second quarter wave plate and a reflective polarizing film which are coaxially arranged along the main axis direction from an exit pupil side to an image source side. The two lenses are coaxially arranged along the optical axis direction, the lens close to one visual side is a first lens, and the other lens is a second lens. The second lens is provided with a composite film of a first quarter wave plate and an absorption type polaroid at the side close to the display screen, wherein a light splitting film (preferably a semi-reflective semi-transparent optical film) is attached at the side close to the display screen of the quarter wave plate. A composite film formed by a second quarter wave plate and a reflective polarizer is closely adhered to the position close to the display screen, and the reflective polarizer is positioned between the second quarter wave plate and the display screen. In order to reduce stray light of the optical system, an antireflection film may be attached to a side of the second quarter wave plate, which is close to the second lens, by bonding or other means. The first lens is a convex lens, and an antireflection film can be plated for imaging quality. The second lens is a concave lens, and a surface of the second lens facing the screen is a concave surface.

In the polarization folding short-focus eyepiece, the reflective polarizer is used for transmitting the first linear polarized light and reflecting the second linear polarized light, and the polarization directions of the first linear polarized light and the second linear polarized light are orthogonal; the absorption type polaroid is used for absorbing the first linear polarized light through the second linear polarized light; the polarization transmission directions of the absorption type polarizer and the reflection type polarizer are orthogonal. The first linearly polarized light transmitted from the reflective polarizing plate is folded between the reflective polarizing plate and the light splitting film and changes in polarization state, and a part of light changed into the second linearly polarized light is refracted through the second lens and the first lens after being transmitted from the absorption polarizing plate and then is emitted to the exit pupil position.

The utility model also provides near-eye display equipment comprising the optical path folding ocular. In the near-eye display device, a display element and a controller are provided in addition to the optical lens, the polarizing film, and the quarter-wave plate film. The display element is used for displaying images and emitting polarized light with a preset polarization state (namely, first polarized light) to one side of the lens; the controller controls the display of the image on the display element according to the received image signal. The position between the display element and the optical lens is adjustable, and on the optical axis, the distance L between the last optical surface of the second lens (i.e. the surface of the second lens facing the screen) and the light-emitting surface of the screen is adjusted within 10-25mm, so as to realize that the eyepiece can achieve a corresponding vision adaptation range of 0D to-5D for a visual observer using the eyepiece. As an example, the display element may be a micro liquid crystal display device that can emit polarized light. Alternatively, the display element is a micro display device that does not emit polarized light, and the surface of the display element on the side of the optical path folding eyepiece has a polarizing layer that is provided separately or integrally with the display element.

The surface parameters of each lens in the polarization folding short-focus eyepiece and the polarization principle of the near-eye display device comprising the polarization folding short-focus eyepiece are described below with reference to specific embodiments and drawings.

In the following description, a three-dimensional rectangular coordinate system is established with the direction of the visual axis (i.e., the optical axis of the optical path folding eyepiece) as the Z direction, the direction perpendicular to the visual axis as the Y direction, and the direction perpendicular to the Y-Z plane as the X direction.

Fig. 1 is a longitudinal section view of an optical system in a near-eye display device according to the present utility model, including: an LCD display 101, an input polarizing reflective composite sheet 102, an output polarizing composite sheet 103, and an optical lens group 104, arranged in that order from the display to the human eye 105.

The LCD display 101 is used for emitting P-type linear polarized image light, the diagonal size of the LCD display 101 is between 6cm and 10cm, and the incidence angle of the principal ray of the near-eye display device is within the range of-10 degrees to 10 degrees. Because of the large size of the LCD display 101, the chief ray incidence angle of the display screen can be adapted to the visual optical system even if controlled in a small range, achieving a large-sized display effect, and thus improving the display uniformity of the entire system. The display 101 is connected to a controller (not shown) that controls the display of images on the display based on the received image signals. The axial position of the display can be adjusted to vary the distance between the LCD display 101 and the optical lens assembly 104 to achieve 0 to-5D visibility adjustment.

The input polarizing reflective composite plate 102 is attached to the LCD display 101 near the human eye side, and can change the linear polarized light emitted from the display into circular polarized light.

The output polarization compound plate 103 is attached to the concave surface of the second lens, which is close to the display screen side, and can change the emergent circularly polarized light meeting the rotation direction requirement into linearly polarized light to enter the optical lens group and finally enter human eyes.

The optical lens assembly 104 is composed of a convex lens and a concave lens. In order to adapt to a large-size screen with a size of more than 2 inches, for example, a display image source with a diagonal size of between 6cm and 10cm is adapted, so that the focal length range of the first lens is 50mm to 100mm, the focal length range of the second lens is-150 mm to-350 mm, and the ratio of the light transmission apertures of the first lens and the second lens is 0.35 to 0.6.

The thickness of the center of the first lens is 2-10 mm, the thickness of the edge is 2-4 mm, and the surface close to the second lens is a convex surface. The thickness of the center of the second lens is 2 mm-4 mm, and the thickness of the edge is 2 mm-8 mm. The second lens is a concave surface with a curvature radius larger than 300mm on the side close to the screen. The distance between the first lens and the second lens is 0-3 mm.

The F number of the polarization folding short-focus eyepiece meets 5< F <10, and the total optical length is TTL (transistor-transistor logic) which is 25mm and 40mm. The polarization folding eyepiece satisfies at least two of the following conditions: the angle of view is greater than 80 degrees, the diameter of the exit pupil is 5 mm-10 mm, and the distance of the exit pupil is 15 mm-20 mm.

Specifically, the LCD display 101 has a square effective display area, and may be replaced with an OLED display, an LCoS display, or the like.

The input polarizing and reflecting composite sheet 102 includes, but is not limited to, a reflective polarizer 1021 near the screen side and a quarter wave plate 1022 near the second lens side, so long as it can change the image light emitted by the display into circularly polarized light and achieve a certain light energy utilization rate, and an antireflection film may be attached to one side of the quarter wave plate to improve the optical performance. The LCD display 101 is combined with an input polarizing reflective composite 102 for emitting polarized light having a predetermined polarization state to one side of an optical lens group 104.

The output polarization composite plate 103 includes an absorption type polarization plate 1031 near the second lens, a quarter wave plate 1032 near the display screen side, and a light-splitting film, preferably a transflective film having a transmission ratio of 1:1, but a light-splitting film having other transmission ratios may be used.

The optical lens group 104 includes a first lens 1041 near the eye side and a second lens 1042 near the display. Along the optical axis direction, four optical surfaces of the optical lens group 104 are defined as S11, S12, S21, S22 from the human eye side to the display screen side, respectively. Preferably, the surface S11 of the first lens 1041 facing the exit pupil side is provided as a spherical surface, which is easy to process and keep clean, and the surface types of the S12 surface of the first lens 1041 and the two surfaces of the second lens 1042 are aspherical surfaces for correcting aberrations, improving the image display effect.

The surface of the output polarization composite sheet, which is close to the display screen side, is attached with an optical film with a preset inverse transmittance ratio, so that a part of circularly polarized light emitted from the input polarization reflection composite sheet 102 can be transmitted to the output polarization composite film 103, and at the same time, part of light is reflected back to the input polarization reflection composite film 102 and changes the rotation direction, and part of light passes through the light splitting film again after being reflected by the input polarization reflection composite sheet 102, then passes through the optical lens group 104 and finally enters the human eye 105.

The various surface shape parameters of the polarization folded short focal eyepiece in this embodiment are described below. The first lens 1041 is a convex lens, the second lens 1042 is a concave lens, and the sum of the center thicknesses D (i.e., the thicknesses on the optical axis) of the two lenses is equal to 9.6mm. The two lenses are made of optical plastic with good uniformity, and can be produced in a large scale with ultra-thin, low cost by injection molding.

Table 1 shows the design parameters of the various optical surfaces in the polarization folded short focal eyepiece

Surface of the body	Type(s)	Radius of curvature	Thickness of (L)	Refractive index	Abbe number
						Exit pupil	Spherical surface	Infinite number of cases	18.5
S11	Spherical surface	270	7.2	1.6857	57.07
						S12	Aspherical surface	-42.97	0.2
S21	Aspherical surface	-240	2.2	1.544	56
						S22	Aspherical surface	300	20.5

Table 2 aspheric coefficients of three aspheric surfaces

Surface coefficient	S12	S21	S22
				Conic constant(K)	0	0	0
A4	3.58E-06	4.09E-06	-2.58E-6
				A6	2.67-08	-4.65E-09	5.86E-9
A8	-9.31E-11	0	-2.87E-12
				A10	9.25E-14	0	-3.99E-15
A12	0	0	6.48E-18
				A14	0	0	-2.78E-21
A16	0	0	-5.43E-25
				A18	0	0	7.40E-28
A20	0	0	-1.55E-31

Wherein, the equation of the aspheric surface is:where c is the inverse of the radius of curvature, r is the radial distance of a point on the surface, k is the conic constant, and Ai is the higher-order term coefficient.

The parameters of the optical system finally realized by the embodiment are as follows: the exit pupil diameter is 8mm, the exit pupil distance is 18.5mm, the F number is 7.75, the field angle is 80 degrees, the total optical length TTL=31 mm, the image plane height, namely the display source height is 71.2mm, and the maximum incidence angle of the principal ray is 5.3 degrees. Structurally, the ratio of the light transmission aperture of the first lens to that of the second lens is 0.527, wherein the focal length of the first lens is 55.8mm, and the focal length of the second lens is-327 mm.

Fig. 2 is a schematic diagram of the polarization principle of the optical path of the near-eye display device according to the present utility model. LCD display 201 emits image light 207 that impinges on reflective polarizer 202 of the input polarizing reflective composite; the light rays become linearly polarized P-rays 208 after passing through the reflective polarizer 202 in the input reflective polarizing composite; the linearly polarized P light 208 then passes through the quarter wave plate 203 of the input polarizing reflective composite, and the polarization state of the linearly polarized light is converted into right-handed circularly polarized light 209; the right-handed circularly polarized light 209 is folded and transmitted toward the display screen side after being reflected by the light-splitting film 204, while the rotation direction of the polarization is changed, from right-handed to left-handed circularly polarized light 210, and after passing through the quarter wave plate 203, the left-handed circularly polarized light is converted to linearly polarized S light 211 perpendicular to the light transmission plane; at this time, the polarization direction of the linear polarized S light 211 is perpendicular to the light passing direction of the reflective polarizer 202, and the linear polarized S light 211 is reflected when transmitted to the reflective polarizer 202, and the transmission direction is changed again, so as to become linear polarized S light 212 transmitted to the human eye side from the display screen; the linearly polarized S light 212 changes back to the left circularly polarized light 213 again after passing through the quarter wave plate 203; when the left circularly polarized light 213 reaches the light splitting film 204 again, the light enters the optical lens group in a transmission way, and the polarization characteristic of the light is unchanged, so that the light is left circularly polarized light 214; after the left circularly polarized light 214 passes through the quarter wave plate 205 of the output polarizing composite, the left circularly polarized light becomes linearly polarized S light 215 perpendicular to the light transmission plane; the light passing axis direction of the absorptive polarizer 206 of the output polarizing composite is identical to the polarization direction of the linear polarized S light 215, and the linear polarized S light 215 becomes linear polarized S light 216 after passing through the polarizer 206, passes through the optical lens group, and finally enters the human eye.

The foregoing description is only of the preferred embodiments of the present disclosure, and is not intended to limit the scope of the present disclosure. The present disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the disclosure to those skilled in the art. In addition, the features of the embodiments may be combined in other ways than the embodiments described above, and the combined technical solutions still fall within the scope of the application.

Claims

1. A polarization fold short Jiao Mujing suitable for use in a display image source having a diagonal dimension between 6cm and 10 cm; characterized by comprising the following optical devices coaxially arranged in the optical axis direction from the exit pupil side to the image source side: the optical element comprises a first lens, a second lens, an absorption type polarizer, a first quarter-wave plate, a light splitting film, a second quarter-wave plate and a reflective polarizer;

the first lens close to the exit pupil side is a convex lens, the second lens far away from the exit pupil side is a concave lens, the surface of the second lens facing the image source side is a concave surface, the focal length range of the first lens is 50 mm-100 mm, the focal length range of the second lens is-150 mm-350 mm, the distance between the surface of the first lens facing the exit pupil side on the optical axis and the light exit surface of the screen is 10 mm-25 mm, and the ratio of the light transmission caliber of the first lens to that of the second lens is 0.35-0.6.

2. The polarization folded short focus eyepiece of claim 1 wherein:

the absorption type polaroid is arranged on the surface of the second lens, which is close to the display image source side, and the first quarter wave plate and the light splitting film are closely attached to the absorption type polaroid.

3. The polarization folded short focus eyepiece of claim 2 wherein:

the reflective polarizer is disposed adjacent to the display image source, and the second quarter wave plate is disposed adjacent to the reflective polarizer.

4. The polarization folded short focus eyepiece of claim 1 wherein:

another polarizer is arranged between the reflective polarizer and the display image source.

5. The polarization folded short focus eyepiece of claim 1 wherein:

the incidence angle of the principal ray of the display image source is within the range of-10 degrees to 10 degrees.

6. The polarization folded short focus eyepiece of claim 1 wherein:

the side, close to the screen, of the second lens is a concave surface with a curvature radius larger than 300 mm.

7. The polarization folded short focus eyepiece of claim 1 wherein:

at least one aspheric surface is arranged in the surface types of the first lens and the second lens.

8. The polarization folded short focus eyepiece of claim 1 wherein:

the center thickness of the first lens is 2 mm-10 mm, the edge thickness of the first lens is 2 mm-4 mm, the center thickness of the second lens is 2 mm-4 mm, the edge thickness of the second lens is 2 mm-8 mm, and the distance between the first lens and the second lens is 0-3 mm.

9. The polarization folded short focus eyepiece of claim 1 wherein:

the F number of the polarization folding short-focus eyepiece meets 5< F <10,

the polarization folding short-focus eyepiece meets at least two of the following conditions: the angle of view is greater than 80 degrees, the diameter of the exit pupil is 5 mm-10 mm, and the distance of the exit pupil is 15 mm-20 mm.

10. A slim and lightweight near-eye display apparatus comprising a display element for displaying an image and emitting a first polarized light to one side of the polarization folded short-focus eyepiece, a controller, and the polarization folded short-focus eyepiece of claim 1; the controller controls the display of the image on the display element according to the received image signal; the distance L between the surface of the second lens facing the display element and the screen light-emitting surface of the display element on the optical axis is adjusted within 10-25mm, so that 0D-5D range visibility adjustment of the polarization folding short Jiao Mujing to a visual observer is realized.