CN111381370B

CN111381370B - Optical imaging system for detecting adaptability of cornea to AR (augmented reality) equipment

Info

Publication number: CN111381370B
Application number: CN202010341395.7A
Authority: CN
Inventors: 杨秀彬; 岳炜; 徐婷婷; 常琳; 徐超
Original assignee: Changchun Institute of Optics Fine Mechanics and Physics of CAS
Current assignee: Changchun Institute of Optics Fine Mechanics and Physics of CAS
Priority date: 2020-04-27
Filing date: 2020-04-27
Publication date: 2021-06-01
Anticipated expiration: 2040-04-27
Also published as: CN111381370A

Abstract

The utility model provides an optical imaging system who detects cornea to AR equipment suitability relates to optical imaging system design technical field, the problem that needs the optical imaging system of different human eyes to current AR equipment suitability of a detection, the system includes the first meniscus lens, first doublet of cemented lens, second doublet of cemented lens, the aperture diaphragm, third doublet of cemented lens, fourth doublet of cemented lens and second meniscus lens that set gradually along same optical axis, after the light that the human eye cornea reflected passes through the corneal contact lens deflection, through first meniscus lens correction spherical aberration, chromatic aberration is eliminated to first doublet of cemented lens and second doublet of cemented lens, aperture diaphragm beam limiting, third doublet of cemented lens and fourth doublet of cemented lens, the second meniscus lens is formation after correcting the spherical aberration. The spherical aberration, the coma aberration, the astigmatism, the field curvature, the distortion, the axial chromatic aberration and the vertical axis chromatic aberration of the invention are all very small, and the imaging quality is high; the invention can analyze the imaging cornea of different people and eliminate the existing defects of AR glasses.

Description

Optical imaging system for detecting adaptability of cornea to AR (augmented reality) equipment

Technical Field

The invention relates to the technical field of optical imaging system design, in particular to an optical imaging system for detecting adaptability of a cornea to AR equipment.

Background

The AR technology is an augmented reality technology, the real world can be fused with virtual information such as images, videos and 3D models in real time, the purpose that the virtual world is sleeved on the real world and interacts is achieved, and experience and immersion from multiple aspects such as vision, hearing and touch are enhanced in a real scene fusion mode. The AR technology has wide application prospect, and has obvious advantages in the fields of military aircraft navigation, data model visualization, biomedical research, precise instrument manufacturing, remote intelligent control, modern high-efficiency logistics and the like by virtue of the unique reality augmentation technology and the high-efficiency output characteristic.

In recent years, AR devices such as Magic Leap glasses, Google glasses, Microsoft HOLONES, Epson glasses, etc. have been introduced by many companies. After investigation and analysis, the AR equipment is not produced and applied widely in large area at present. In addition to the cost, human eyes of different corneal curvatures also have great demands on AR devices: firstly, 3D dizziness is easily generated in the imaging process of the AR equipment close to human eyes under the influence of different human eye diopters; secondly, the light leakage and low contrast phenomena can be caused when the human eyes observe through the AR equipment due to different curvatures of corneas of different human eyes; thirdly, the device has no natural human eye fuzzy focusing adjustment function and cannot adapt to binocular parallax and mobile parallax. In response to the existing problems described above, further exploration of the ability to adapt to imaging of the cornea of the human eye with different AR devices is needed.

Optical display devices are an important component of AR devices. The display is roughly classified into a retinal display, a head-mounted display and a monocular head-mounted display according to the difference between the optical display device and the display mode. The retinal display is directly imaged on the retina of a human eye; the head-mounted display images on the user screen in a manner of superimposing the enhanced information; monocular head-mounted projection uses a spectroscopic pico-projector to reflect the desired content to the front surface of the observer for projection. In any kind of AR display, human eyes act as an imaging unit in the AR display, which determines the imaging quality of the AR display, so that human eyes with good diopter and curvature adaptation can make the AR display perform better imaging function. However, according to investigation, the number of patients with eye diseases in China exceeds 7 hundred million, and how to screen out human eyes matched with the AR display from a large number of human eye systems is urgent. Therefore, an optical imaging system for detecting the adaptability of the cornea to the AR device needs to be invented to screen the matching capability of different human eyes to the existing AR device.

Disclosure of Invention

The invention provides an optical imaging system for detecting the adaptability of a cornea to an AR (augmented reality) device, aiming at solving the technical bottlenecks that the AR display device is easy to generate 3D (three-dimensional) dizziness, low resolution, low transmittance, low contrast, poor image quality and the like and needing an optical imaging system for detecting the adaptability of different human eyes to the conventional AR device.

The technical scheme adopted by the invention for solving the technical problem is as follows:

the optical imaging system comprises a first meniscus lens, a first doublet, a second doublet, an aperture diaphragm, a third doublet, a fourth doublet and a second meniscus lens which are sequentially arranged along the same optical axis, wherein light reflected by a cornea of a human eye is deflected by a corneal contact lens, and is imaged after being corrected for spherical aberration by the first meniscus lens, eliminated for chromatic aberration by the first doublet and the second doublet, limited for the aperture diaphragm, eliminated for chromatic aberration by the third doublet and the fourth doublet, and corrected for spherical aberration by the second meniscus lens.

The invention has the beneficial effects that:

the optical imaging system for detecting the adaptability of the cornea to the AR equipment has small spherical aberration, coma aberration, astigmatism, field curvature, distortion, axial chromatic aberration and vertical axis chromatic aberration, and has good image quality and resolution and high imaging quality.

The optical imaging system for detecting the adaptability of the cornea to the AR equipment can analyze the imaging cornea of different people, and eliminates the existing defects of AR glasses. By adopting the optical imaging system, a complete cornea image can be obtained. The invention solves the technical bottlenecks of poor imaging quality, 3D dizziness caused by wearing, low resolution, low transmittance and the like between human eyes and the matched AR equipment. The invention is beneficial to the selection of human eyes on the existing AR equipment, enhances the adaptability and comfort of the existing AR equipment to the real environment, and is beneficial to clearer imaging, more convenient wearing and wider applicable population.

Drawings

FIG. 1 is a schematic diagram of an optical imaging system for detecting the suitability of a cornea for an AR device according to the present invention.

FIG. 2 is a schematic diagram of an application of an optical imaging system for detecting the suitability of a cornea for an AR device according to the present invention.

FIG. 3 is a graph of the modulation transfer function of an optical imaging system for detecting the suitability of a cornea for an AR device in accordance with the present invention.

FIG. 4 is a Seidel aberration diagram of an optical imaging system for detecting the suitability of a cornea for an AR device according to the present invention.

FIG. 5 is a diagram of a standard dot array for an optical imaging system for detecting the suitability of a cornea for an AR device in accordance with the present invention.

In the figure: 1. the lens comprises a first meniscus lens, a second meniscus lens, a first doublet, a second doublet, a third doublet, a fourth doublet, a second meniscus lens, a second doublet, an aperture diaphragm, a third doublet, a fourth doublet, a second meniscus lens, a second cylinder, a third cylinder, a fourth cylinder, a second cylinder.

Detailed Description

In order that the above objects, features and advantages of the present invention can be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described herein, and therefore the scope of the present invention is not limited by the specific embodiments disclosed below.

An optical imaging system for detecting the adaptability of a cornea to an AR device, as shown in fig. 1, includes a first meniscus lens 1, a first doublet cemented lens 2, a second doublet cemented lens 3, an aperture stop 4, a third doublet cemented lens 5, a fourth doublet cemented lens 6 and a second meniscus lens 7, which are sequentially arranged along the same optical axis. The optical imaging system further comprises a Placido plate 9, wherein the Placido plate 9 is provided with a first meniscus lens 1, a first doublet cemented lens 2, a second doublet cemented lens 3, an aperture diaphragm 4, a third doublet cemented lens 5, a fourth doublet cemented lens 6 and a second meniscus lens 7 which are sequentially arranged, namely the Placido plate 9 is arranged on one side of the first meniscus lens 1, and the first doublet cemented lens 2 is arranged on the other side of the first meniscus lens 1. Placido plate 9 is made of a diffuse reflective material. The aperture of the aperture diaphragm 4 is the same as the aperture of the central hole of the Placido plate 9. The human eye 11 is aligned with the central aperture (aperture at the center of black and white concentric circular ring) of the Placido plate 9, as shown in fig. 2, the incident light is reflected by the cornea 11 of the human eye after being diffusely reflected by the Placido plate 9, the light reflected by the cornea 11 of the human eye is deflected by the corneal contact lens 12, the spherical aberration is corrected by the first meniscus lens 1, the chromatic aberration is eliminated by the first doublet 2 and the second doublet 3, the aperture stop 4 limits the beam, the chromatic aberration is eliminated by the third doublet 5 and the fourth doublet 6, and the spherical aberration is corrected by the second meniscus lens 7 to form an image on the detector. The probe employs a cmos sensor 10. The optical imaging system further comprises a cylinder 8, the first meniscus lens 1, the first doublet cemented lens 2, the second doublet cemented lens 3, the aperture diaphragm 4, the third doublet cemented lens 5, the fourth doublet cemented lens 6 and the second meniscus lens 7 are all located in the cylinder 8, and the Placido plate 9 is arranged corresponding to the cylinder 8.

The principle of the imaging system is shown in fig. 2: arc ABC is the cross section of the center of the Placido disc 9. B is a point on the Placido plate 9, A is the position of a central circular hole, C is the end point of the Placido plate 9, B can obtain a virtual image point B 'after being imaged by the cornea, after the human eye 11 is provided with a cornea shaping mirror, B can obtain another virtual image point B' after being imaged by the cornea shaping mirror and the cornea, and B 'is positioned on the right side of B'. By utilizing the geometrical optics principle, the cornea/cornea with the cornea contact lens 12 is used as a lens to form a focusing imaging optical unit (a human eye 11 is aligned with a small hole at the center of a concentric ring, the size of an aperture diaphragm 4 of an optical imaging system is the same as that of the small hole at the center), incident light is reflected by the cornea after being diffusely reflected by a black and white ring of a Placido disc 9, and is acquired and processed by a cmos sensor 10 after being subjected to imaging optimization through a first meniscus lens 1, a first doublet 2, a second doublet 3, the aperture diaphragm 4, a third doublet 5, a fourth doublet 6 and a second meniscus lens 7. If the corneal contact lens 12 is arranged, incident light is reflected diffusely by a black and white ring of the Placido plate 9, then is refracted by the corneal contact lens 12 and then is reflected by the cornea, and the light reflected by the cornea is refracted by the corneal contact lens 12 and then is incident to the first meniscus lens 1.

In order to facilitate the imaging illumination of the optical imaging system, an illuminating device is required to be added, the illuminating device adopts a visible light LED light source to illuminate human eyes 11, and the wave bands are 486nm, 587nm and 656 nm.

Because the corneal reflection has the function of reducing the field angle, the optical imaging system of the invention has a small field of view and a small relative aperture, and the basic parameters of the field of view, the relative aperture and the like are determined according to the pixel size, the object height, the image height, the object distance and the like of the cmos sensor 10.

The optical imaging system of the present invention is a paraxial imaging optical system. The transverse diameter of the adult cornea is 11.5-12mm, the vertical diameter is 10.5-11mm, and the measurement range of the cornea surface is within 10mm in order to obtain a complete cornea image. The aperture of the aperture diaphragm 4 is the same as that of the central small hole of the Placido plate 9, and the diameter value of the aperture diaphragm is 8 mm. The design process of the invention is as follows: and (3) carrying out PW method calculation according to the paraxial imaging and thin lens principle, selecting a group of initial structures with the minimum aberration, and optimizing by using zemax software. And (3) setting partial curvature as a variable, replacing the material of the glass, and setting an optimized operation number. The final optical imaging system focal length is 18.36mm, the barrel 8 barrel length is 36.49mm, and the image height is 1.24 mm.

In this embodiment, the first meniscus lens 1, the first doublet lens 2, the second doublet lens 3, the third doublet lens 5, the fourth doublet lens 6, and the second meniscus lens 7 are all glass lenses. The first meniscus lens 1 and the first meniscus lens 1 are made of LAKN12, and the first cemented doublet 2, the second cemented doublet 3, the third cemented doublet 5 and the fourth cemented doublet 6 are all composed of LAKN12-BASF5 and SSK4A-KZFS 1.

The first meniscus lens 1 can effectively correct curvature of field, correcting spherical aberration using the curvature characteristic of a thin lens. The outer surfaces (the left outer surface and the right outer surface) of the first cemented doublet 2 are plated with antireflection films in a visible light range (400-700 nm), the outer surfaces of the second cemented doublet 3, the third cemented doublet 5 and the fourth cemented doublet 6 are also plated with antireflection films in a visible light range (400-700 nm), and a broadband antireflection multilayer film, namely an antireflection film, is plated to reduce the reflection of light beams in a visible light waveband, so that the loss of light energy is reduced, and the imaging quality is clear. The secondary spectrum is reduced by means of gathering the three chromatic aberrations to one point, and the chromatic aberrations can be eliminated. The first cemented doublet 2, the second cemented doublet 3, the third cemented doublet 5 and the fourth cemented doublet 6 for achromatization are very critical parts in the imaging process of the system. If no achromatic structure exists, extra phase difference exists in the diffracted light reaching the second meniscus lens 7, and finally the obtained image is subjected to diffraction aliasing, so that the quality of later-stage image data reconstruction is affected. The use of an achromatic structure can reduce or eliminate chromatic aberration due to transmission, so that light rays of different wavelengths can be clearly focused on the cmos sensor 10 after being diffracted. The symmetric achromatic system can ensure good imaging quality of the paraxial part, and only takes single-color aberration into consideration without considering high-level aberration when correcting aberration. In use, the human eye 11 is in a conjugate state with the image received by the detector, so that the aberration reaches a minimum state. The lens group of the optical imaging system adopts an approximately symmetrical structure, the aperture diaphragm 4 is arranged in the middle of the approximately symmetrical structure, and the aperture diaphragm 4 effectively controls the energy of imaging beams and ensures the condition of paraxial imaging. The first meniscus lens 1 and the second meniscus lens 7 are approximately symmetrical; the first cemented doublet 2 and the fourth cemented doublet 6 are approximately symmetrical; the second cemented doublet 3 and the third cemented doublet 5 are approximately symmetrical.

The MTF curve of the optical imaging system of the present invention is shown in fig. 3, and in order to achieve higher sharpness of the image edge, there are requirements for high and medium frequencies: the MTF values were above 0.8 at the mid frequency of 33.79lp/mm and 67.58lp/mm were above 0.7 at high frequencies, approaching the diffraction limit. The monochromatic aberration and chromatic aberration of each lens are shown in fig. 4, and the histogram corresponding to each region is spherical aberration, coma aberration, astigmatism, curvature of field, distortion, axial chromatic aberration, and vertical axis chromatic aberration from left to right. In fig. 4, "1" in the figure is a plane, and can be regarded as a parallel plate in actual processing, and can be regarded as a reference plane in measurement, and "2" and "3" in the figure represent the second meniscus lens 7, and "4", "5" and "6" in the figure represent the fourth cemented doublet 6, and "7", "8" and "9" in the figure represent the third cemented doublet 5, and "11", "12" and "13" in the figure represent the second cemented doublet 3, and "14", "15" and "16" in the figure represent the first cemented doublet 2, and "17" and "18" in the figure represent the first meniscus lens 1, and it is shown that although spherical aberration, coma aberration, and lateral chromatic aberration of individual lenses are more obvious, total aberration and chromatic aberration before the combined action by the combined lenses are almost small, and imaging quality is good. Fig. 5 shows a standard dot array diagram, where the visible diffuse spots are all smaller than the selected sensor pixel size. Has good image quality, size close to that of the Airy spots and good resolution.

Analyzing the influence of the corneal contact lens 12 with the cornea on the AR imaging equipment, optimally designing and imaging an optical imaging system on an image sensor, and calculating the bending degree of the cornea through the analysis of concentric rings on an image, the deformation degree of the concentric rings on a reflected image and the steepness of the distance between the concentric rings; and (3) analyzing the curvature radius, diopter and angular vision resolution of each sampling point image of the front surface of the cornea. Through diopter to people's eye 11, corneal curvature, wear 12 thicknesses of corneal contact lens, material and carry out the analysis to the formation of image effect, and then solve different people's eye 11 and to the detection of current AR equipment's adaptability, solve the formation of image quality difference that produces between people's eye 11 and the matching AR equipment, wear to produce 3D giddiness, resolution ratio low, technical bottleneck such as transmittance low. The optical imaging system is used for analyzing the AR equipment by the image acquisition systems with different diopters, and has wide research value.

Based on the optical imaging system, a complete cornea image can be obtained. The optical system has the advantages of wide visual field, clear imaging, no influence of illumination and the like, can detect the use conditions of different corneal contact lenses 12 and naked eyes thereof, and selects the optimal solution for the adaptive performance of AR glasses. By establishing human eye 11 imaging models with different diopters, the human eye 11 with the corneal contact lens 12/the standard human eye 11 are respectively subjected to optical imaging system simulation imaging based on the Placido plate 9. By matlab iterative computation, the reflection image formed by the Placido plate 9 system formed by simulated imaging has errors with the actual reflection image, and a complete cornea image cannot be formed.

The imaging cornea analysis of different people is performed through the optical imaging system, the existing defects of the AR glasses are eliminated, and the following conclusion can be obtained: if a contact AR device/retinal display AR device is used for imaging, the virtual image presented by the wearer may also be projected onto a plane, as the virtual image is located a distance behind the apex of the corneal surface. The contact lens 12 is selected to be a rigid gas impermeable contact lens 12, thicker than plastic polymer such as (PMMA), suitable for use in myopia or hyperopia patients and for use by individuals without foreign body sensation when wearing the thicker contact lens 12. The method has the advantages of large visual field, clear imaging and the like; if a helmet-type AR display is used for imaging, the image is formed on a user screen in an information enhancing mode, the visual range is short, the visual field is wide, the influence of stray light is easy to cause, and the method is suitable for people who need to wear the thin and clear silica gel type corneal contact lens 12 for high myopia. The monocular head-mounted projection AR equipment avoids excessive interference on users to watch real environment information because the spectroscope is positioned above the front surface of a monocular, performs imaging through interactive virtual reality of two eyes, is small in size, light in weight and not easy to generate 3D dizziness, and is suitable for being used by people with normal cornea forms, good diopter without pathological changes or normal eyesight recovering after eye laser surgery. The invention is beneficial to the selection of the human eye 11 on the existing AR equipment and the enhancement of the adaptability and comfort of the human eye to the real environment, and is beneficial to clearer imaging, more convenient wearing and wider applicable population.

Claims

1. The optical imaging system is characterized by comprising a first meniscus lens (1), a first doublet (2), a second doublet (3), an aperture diaphragm (4), a third doublet (5), a fourth doublet (6) and a second meniscus lens (7) which are sequentially arranged along the same optical axis, and further comprising a Placido disc (9) made of diffuse reflection materials, wherein the aperture of the aperture diaphragm (4) is the same as that of a central small hole of the Placido disc (9), the first meniscus lens (1) is positioned between the Placido disc (9) and the first doublet (2), incident light is diffusely reflected by the Placido disc (9) to enter a human eye (11) and is reflected by the cornea of the human eye (11), and the light reflected by the cornea of the human eye (11) is deflected by a corneal contact lens (12) and then is corrected by the first meniscus lens (1) to form spherical aberration, The first doublet (2) and the second doublet (3) eliminate chromatic aberration, the aperture diaphragm (4) limits the beam, the third doublet (5) and the fourth doublet (6) eliminate chromatic aberration, and the second meniscus (7) corrects spherical aberration and then images.

2. An optical imaging system for detecting the adaptation of the cornea to an AR device as claimed in claim 1, characterized in that the aperture diameter of the aperture stop (4) is 8 mm.

3. The optical imaging system for detecting the adaptability of the cornea to the AR device as claimed in claim 1, wherein the optical imaging system further comprises a cylinder (8), the first meniscus lens (1), the first doublet (2), the second doublet (3), the aperture stop (4), the third doublet (5), the fourth doublet (6) and the second meniscus lens (7) are all located in the cylinder (8), and the Placido plate (9) is arranged corresponding to the cylinder (8).

4. The optical imaging system for detecting the suitability of a cornea for an AR device of claim 1, wherein the optical imaging system further comprises an illumination device.

5. The optical imaging system for detecting the adaptation of the cornea to the AR equipment as set forth in claim 4, wherein the illumination device illuminates the human eye (11) with visible LED light sources in the wavelength bands 486nm, 587nm, and 656 nm.

6. The optical imaging system for detecting the adaptability of the cornea to the AR equipment as set forth in claim 1, further comprising a detector for receiving an image formed by correcting spherical aberration by the second meniscus lens (7), wherein the human eye (11) is conjugate to the image received by the detector.

7. The optical imaging system for detecting the adaptability of the cornea to the AR device as claimed in claim 1, wherein the outer surfaces of the first cemented doublet (2), the second cemented doublet (3), the third cemented doublet (5) and the fourth cemented doublet (6) are coated with antireflection films in the visible light range.