A kind of waveguide display deviceTechnical field
The present invention relates to augmented reality display device (AR) or display (Head-up) device that comes back, in particular to a kind of increasingsAdd the brightness uniformity of emergent pupil output image, and improves the waveguide display device of system efficiency of transmission.
Background technique
Augmented reality is the new of the same picture or space that real world information and virtual world information are added in real timeTechnology.It is added in real world by prompt information, dummy object or virtual scene that computer generates, realizes exceeding realitySensory experience.Due to having the characteristic that can carry out enhancing display output to true environment, augmented reality is in data modelVisualization, military weapon research and development have extensively with manufacture, flight navigation, medical training, long-range control, amusement with fields such as artApplication.
Display device in augmented reality is divided into Light Transmission according to displaying principle and video transmission-type two is bigClass.Due to high resolution, no visual deviation, without time delay and more meet the advantages such as social habit, Light Transmission augmented realityDisplay system has become mainstream.
In order to realize the augmented reality displaying scheme of Light Transmission, someone devise based on bird bath (Bird Bath) orThe conventional optical systems of person's free form surface element realize virtual and real world superposition using refraction and reflection, however suchOptics total distance is limited by by the display system that traditional optical elements form, can not accomplish frivolous enough, realizes that augmented reality is aobviousShow the glasses of system；In addition by the containing of Lagrange invariant, the emergent pupil size of traditional optical display system is limited, usuallyThe user crowd that interpupillary distance is in both ends can not be adapted to.Compared with conventional optical systems, the displaying scheme based on waveguide is effectively solvedTwo above of having determined problem.One monochrome or RGB image are complete in slab guide element using light by after injection waveguideTransmission and reflection effectively reduces the thickness of optical element, and uses optical element control image substeps one or more in waveguideEmergent pupil extension is realized in output.In the waveguide display device extended based on emergent pupil, the light energy in waveguide is in substep output processIn gradually decay, and the diffraction efficiency that optical element is output and input in diffraction waveguide is lower, and system energy loss is obvious.CauseHow this, realize that brightness of image is uniform within the scope of emergent pupil, improves system efficiency of transmission, is to promote augmented reality display or new lineThe critical issue of display user experience and system performance.
The side of the interference light intensity conversion phase of patent " big emergent pupil holographical wave guide glasses system " (CN104280885A) descriptionMethod is only used for the holographic grating waveguide of refractive index modulation.Patent " optical presentation system " (CN107690599A) and " OpticalWaveguide " (US9329325B2) changes diffraction using the method for plating one or more layers film with gradually variable in monolithic optical waveguideEfficiency, but gradual change coating process is complicated and since this processing step need to carry out in monolithic optical waveguide, thus manufacturing cost is high.
Summary of the invention
In view of above-mentioned deficiencies of the prior art, the purpose of the present invention is to provide a kind of brightness of increase emergent pupil output imageUniformity improves system effectiveness, and reduces the technology of manufacturing cost.
The purpose of the present invention is achieved through the following technical solutions：A kind of waveguide display device, including waveguide-based bottom,Input diffraction optical element and output diffraction optical element；
Input diffraction optical element, for by the output light coupling input of ray machine projector into waveguide-based bottom.
Waveguide-based bottom, for the directive output diffraction optics that is all-trans will to be carried out from the light of input diffraction optical element coupling inputElement is propagated.
Diffraction optical element is exported, the light for will be totally reflected in waveguide-based bottom is in each contact output diffraction optical elementWhen part diffraction and fractional transmission, diffraction light be coupled out waveguide to human eye, direct transmissive portion continues to be all-trans in waveguide-based bottomIt penetrates until being diffracted coupling output, completion emergent pupil extends.
The input diffraction optical element is optimally designed to couple diffraction efficiency with height, for improving display system effectRate reduces power consumption.Input diffraction optical element can be selected from balzed grating, asymmetric surface relief grating or other with high couplingThe diffraction structure of efficiency.
The slab construction to the optical material composition of visible transparent can be used in the waveguide-based bottom, and upper and lower surface is flatRow；Input diffraction optical element/output diffraction optical element can be fitted closely with waveguide substrate surface, also embeddable waveguide-based bottomMaterial internal.
The output diffraction optical element uses the periodic structure of lower coupling diffraction efficiency, to guarantee in emergent pupil extensionThere is lasting light energy output in the process；Coupling diffraction efficiency is modulated in the effective coverage of output diffraction optical element；Area modulation or continuous modulation can be used in modulation system；The specific method of area modulation or continuous modulation is extended according to waveguide emergent pupilPath and mode be optimally designed.
In order to maximize waveguide display system efficiency, input diffraction optical element coupling diffraction efficiency is being improvedOn the basis of, output diffraction optical element is needed in its effective coverage by all light energy substeps in the inner total reflection of waveguide-based bottomOutput.Meanwhile the image that brightness uniformity is presented to user within the scope of its emergent pupil in order to make waveguide display device, export diffractionThe luminous flux that optical element exports in unit area in its effective coverage is kept constant.According to the output diffraction optical elementEnergy substep output realizes the characteristic of emergent pupil extension, and the coupling output diffraction efficiency for exporting diffraction optical element is optimised for：
Wherein N is the output order of area modulation, NTFor the total number of modulation areas, ηNSpread out for the output of n-th region couplesPenetrate efficiency.
Due to the limitation of diffraction optical element structure or machining accuracy, when the coupling of output diffraction optical element exports effectWhen can not be equal to the result that equation (1) provides after rate is optimized, what is be coupled out in its effective coverage is all-trans in waveguide-based bottomA part of light energy penetrated.Assuming that the ratio that this part light energy accounts for the firing association's light energy that is all-trans is ηT, in order to make within the scope of emergent pupilBrightness of image it is uniform, the coupling efficiency for exporting diffraction optical element is optimised for：
The output diffraction optical element can be selected from one-dimensional diffraction grating.It is sensitive to diffraction structure by modulation diffraction efficiencyParameter, that is, optimize one-dimensional diffraction grating structure on waveguide surface with the variation of position, so that the coupling of output diffraction optical elementIt closes output diffraction efficiency and follows equation (1) or (2).Such as the modulated duty ratio of one-dimensional straight-tooth Surface gratings and tooth it is high, oneTie up that the modulated duty ratio of helical teeth Surface gratings, tooth be high and inclination angle, the modulated tooth height of one-dimensional balzed grating, and face angle.
The output diffraction optical element can be selected from two-dimensional and periodic diffraction structure.By modulation diffraction efficiency to diffraction knotThe parameter of structure sensitivity, i.e. optimization two-dimensional and periodic diffraction structure are on waveguide surface with the variation of position, optimization output diffraction opticsThe coupling of element exports diffraction efficiency.Such as the modulated duty ratio of two-dimentional column diffraction structure and tooth it is high.
The input diffraction optical element and the output available lithography method of diffraction optical element include that electron beam is carvedErosion, reactive ion beam etching (RIBE), magnetic intensified response ion etching, high density plasma etch, inductive coupling type plasma are carvedErosion, transformation coupled plasma etching and electron cyclotron resonance etching.Modulated structure parameter can by control electron beam orIon beam is realized in the exposure of mother matrix substrate.Periodic structure on mother matrix can pass through nano-imprint method, casting, moldingMethod, injection die pressing etc. copy in the resin material of duplicate plate, to adapt to scale of mass production and reduce the demand of manufacturing cost.
Detailed description of the invention
Fig. 1 is the component composition schematic diagram of Light Transmission augmented reality system；
Fig. 2 is the side view of component contained by waveguide type augmented reality glasses side frame and its inside；
Fig. 3 is the top view of waveguide type augmented reality glasses；
Fig. 4 is the top view of waveguide display device；
Fig. 5 is the front view that one-dimensional linear diffraction two-dimensional exit pupil extends optical waveguide；
Fig. 6 A is the side view of one-dimensional straight-tooth Surface gratings；
Fig. 6 B is the side view of one-dimensional helical teeth Surface gratings；
Fig. 6 C is the side view of one-dimensional balzed grating,；
Fig. 7 A is the side view that the one-dimensional straight-tooth Surface gratings of depth modulation are carried out on the basis of grating bottom of the tooth portion；
Fig. 7 B is the side view that the one-dimensional straight-tooth Surface gratings of depth modulation are carried out on the basis of grating tooth crest；
Fig. 8 A is subregion depth modulation helical teeth Surface gratings and non-modulation output diffraction described in Tables 1 and 2Efficiency comparative；
Fig. 8 B is that subregion depth modulation helical teeth Surface gratings described in Tables 1 and 2 and non-modulation output light are logicalAmount comparison；
Fig. 9 A is the front view that two-dimensional linear diffraction two-dimensional exit pupil extends waveguide；
Fig. 9 B is the front view that two-dimentional column diffraction structure two-dimensional exit pupil extends waveguide；
Figure 10 A is the schematic diagram of two-dimentional pyramid diffraction structure；
Figure 10 B is the schematic diagram of two-dimentional gridiron pattern diffraction structure；
Figure 10 C is the schematic diagram of two-dimentional column diffraction structure；
Figure 10 D is the schematic diagram of two-dimensional linear skewed crossing diffraction structure；
Figure 10 E is the schematic diagram of the orthogonal diffraction structure of two-dimensional linear；
Figure 11 A is two-dimentional column diffraction structure and relevant rectangular coordinate system, and the X-axis of coordinate system and a certain period direction are flatRow；
Figure 11 B is the top view and dependency structure parameter of two-dimentional column diffraction structure；
Figure 12 is the polar coordinate system for defining light incident direction；
Figure 13 A is that duty ratio modulation described in table 3 and table 4 and non-modulation two-dimentional column diffraction structure (1,1) grade are saturatingPenetrate diffraction efficiency comparison；
Figure 13 B is that duty ratio modulation described in table 3 and table 4 and non-modulation two-dimentional column diffraction structure (1,1) grade are defeatedLuminous flux compares out；
Specific embodiment
In order to be apparent to realization target of the invention with technical method, below in conjunction with attached drawing and specific implementation example pairThe present invention is further elaborated.
The present invention can be employed for the optical perspective formula augmented reality system based on optical waveguide, as shown in Figure 1, augmented realitySystem 1 includes left eye optical waveguide 2, right eye optical waveguide 3, frame 4, computing unit 5, position sensor 6, exterior space collector 7And remote computing system 8.Left eye optical waveguide 2 and the transmissivity with higher of right eye optical waveguide 3 allow users to clearlyRecognize real world.It configures the computing unit 5 at glasses end and provides corresponding picture signal for right and left eyes, so that user obtains threeTie up stereo vision experience.Computing unit 5 is communicated with each sensor in system simultaneously, including position sensor 6 and outsideSpace acquisition device 7.Position sensor 6 is that augmented reality system determines the position and direction in given coordinate system, this includes edgeThe one-movement-freedom-degree of three rectangular co-ordinate axis directions and rotational freedom around these three reference axis.As a result, in position sensor 6It can be the combination of accelerometer, gyroscope, magnetometer and GPS receiver.Computing unit 5 is by position sensor 6Output processing after, dummy object is accurately rendered in real world.Exterior space collector 7 can be RGB camera, listThe combination of form and aspect machine and depth camera.RGB camera or monochrome cameras obtain the real scene of external environment, and depth camera obtains outerThe depth information of boundary's scene can get reality when depth camera is parallel and synchronous in timing with the optical axis of other camerasThe complete information of scene.Remote computing system 8 can be provided especially by the computing unit 5 that wired or wireless communication is glasses endComputing capability, also can be used as augmented reality system 1 unique computing unit replace glasses end computing unit 5.
As shown in Fig. 2, ray machine projector 9 can be placed in glasses side frame, so that system compact.In ray machine projector 9The image that projects of micro-display 11, pass through 12 coupling of input diffraction optical element of left eye optical waveguide 2 after the amplification of lens group 10It closes and enters left eye optical waveguide 2.Transmissive type liquid crystal display (LCD) can be used by liquid crystal molecule to backlight in micro-display 11Projection modulation forms image, it is possible to use reflective modulation system, wherein there are commonly Digital Light Processor (DLP) and silicon substratesLiquid crystal (LCoS).Self luminous Organic Light Emitting Diode (OLED) and micro- light emitting diode (Micro also can be used in micro-display 11LED).Also micro electromechanical scanning galvanometer (MEMS Scanning Mirror) can be used in micro-display 11.Lens group 10 by a piece of orMulti-disc lens composition.
Glasses vertical view signal as shown in figure 3, for imaging right eye optical waveguide 3 be fixed in frame 4, right eye optical waveguide3 include input diffraction optical element 12 and output diffraction optical element 13.Through input 12 diffraction of diffraction optical element light intoEnter right eye optical waveguide 3 to be totally reflected later, propagates to after output diffraction optical element 13 and gradually couple output to human eye.
The top view of waveguide display device is as shown in figure 4, the light beam 15 that the topmost pixel of micro-display 11 issues passes through lightLens group 10 in machine projector 9 collimates, and after inputting 12 diffraction of diffraction optical element, the first diffraction time light 16 meets waveThe total reflection condition led is totally reflected in waveguide-based bottom 14 and advances to output diffraction optical element 13, defeated contacting each timePart diffraction is partially transmitted when diffraction optical element 13 out, diffraction light is coupled out waveguide-based bottom 14 and reaches human eye, directly transmitsPart continues total reflection in waveguide-based bottom 14 and is advanced until and is diffracted decoupling, thus completes emergent pupil along the extension of Y-direction.
Present invention can apply to the diffraction waveguide augmented reality devices of different frameworks, below to be based on one-dimensional linear diffracted waveIt is explained for the augmented reality device led.The front view of one-dimensional linear diffraction waveguide is as shown in figure 5, optics in this frameworkElement includes input diffraction optical element 12, output diffraction optical element 13 and transmission diffraction optical element 18.This framework canComplete the two-dimensional expansion of emergent pupil.The input picture of ray machine projector (not drawn in the figure) is with flat with the waveguide 19 of one-dimensional linear diffractionThe orthogonal direction in face is the direction of propagation in the center visual field.It inputs diffraction optical element 12 and diffraction is carried out to input light, so that firstDiffraction time meets the total reflection condition at waveguide-based bottom, advances in the substrate towards transmission diffraction optical element 18.One-dimensional linearTotal reflection light can be transmitted or diffraction when contacting each time with transmission diffraction optical element 18 in diffraction waveguide 19.By passingThe transmission direction for the first diffraction time that defeated 18 diffraction of diffraction optical element generates deflects, and meets the total reflection at waveguide-based bottomCondition is advanced towards output diffraction optical element 13 in the substrate.Continue in the light that transmission diffraction optical element 18 directly transmitsTotal reflection is transmitted until being diffracted to output diffraction optical element 13, thus completes the One-Dimensional Extended of emergent pupil in X direction.Carry out autobiographyThe light in defeated area is also partially transmitted part diffraction in contact output diffraction optical element 13 each time, and diffraction light is coupled out oneDimensional linear diffraction waveguide 19 reaches human eye, and direct transmissive portion continues total reflection until being spread out in one-dimensional linear diffraction waveguide 19Decoupling is penetrated, thus completes emergent pupil along the One-Dimensional Extended of Y-direction.Light is expanded in succession in two dimensions of X and Y, therefore Fig. 5In waveguide display device by transmission diffraction optical element 18 and export the achievable emergent pupil of diffraction optical element 13 two dimensional expansionsExhibition.The implementation of waveguide display device can also be different from structure shown in Fig. 5, only include that input diffraction optical element and output are spread outOptical element is penetrated, and without transmission diffraction optical element.In this implementation, input light is after inputting diffraction optical element diffractionIt is directly toward output diffraction optical element total reflection, gradually diffraction exports on output diffraction optical element, completes One-Dimensional Extended.
One-dimensional linear diffraction grating can have a variety of structures, and three kinds be listed in Fig. 6, but be not limited only to this.Input diffractionOptical element 12, output diffraction optical element 13 and transmission diffraction optical element 18 can select in various structures.Fig. 6 A givesThe side view of straight-tooth Surface gratings 20 is gone out, tooth form unit and waveguide-based dolly are straight, and relevant tooth profile parameter has gratingPeriods lambda, facewidth w and the high h of tooth.Helical teeth Surface gratings 21 are as shown in Figure 6B, the normal side of tooth form unit and waveguide-based bottomTo at α, other tooth profile parameters have grating period A, facewidth w and the high h of tooth.Fig. 6 C gives the side view of balzed grating, 22, whereinAngle between glittering face and non-glittering face is β, screen periods Λ, a height of h of tooth.Optical grating construction shown in Fig. 6 all hasInvariable tooth-shape structure, i.e., parameter relevant to tooth form do not change namely grating with grating in the position of waveguide surfaceStructure is non-modulation.However grating diffration efficiency determines that non-modulation optical grating construction is for same side by certain parameters of tooth formTo incident light diffraction efficiency having the same, therefore since need in its effective coverage will be in waveguide for output diffraction optical elementThe light energy substep output of substrate inner total reflection, identical diffraction efficiency make the luminous flux of every step output successively decrease, therefore can notThe image of brightness uniformity is presented to user within the scope of the emergent pupil of waveguide.
In order to solve the above problem, the present invention use modulated grating structures, i.e., tooth form with grating on waveguide surface position and becomeThe method of change, so that output diffraction optical element is different in the coupling output diffraction efficiency of different location.Spread out according to the outputThe characteristic that optical element energy substep output realizes emergent pupil extension is penetrated, when the coupling of output diffraction optical element exports diffraction efficiencyWhen being optimised for the result that formula (1) provides, the luminous flux exported in unit area in effective coverage is kept constant, thus is givenThe brightness of image that user is presented is uniform, and waveguide display system efficiency is maximized, i.e., brightness of image is in certainIt is maximized under system power consumption or system power dissipation minimizes under certain brightness of image.
Wherein N is the output order of area modulation, NTFor the total number of modulation areas, ηNSpread out for the output of n-th region couplesPenetrate efficiency.
Due to the limitation of diffraction optical element structure or machining accuracy, when the coupling of output diffraction optical element exports effectWhen can not be equal to the result that equation (1) provides after rate is optimized, what is be coupled out in its effective coverage is all-trans in waveguide-based bottomA part of light energy penetrated.Assuming that the ratio that this part light energy accounts for the firing association's light energy that is all-trans is ηT, in order to make within the scope of emergent pupilBrightness of image it is uniform, the coupling efficiency for exporting diffraction optical element is optimised for formula (2).
To optimize coupling efficiency, should select to modulate the sensitive parameter that diffraction efficiency has a significant effect.Straight-toothSurface gratings 20 can change diffraction efficiency, helical teeth surface relief light by modulation duty cycle ff=w/ Λ or the high h of toothThe high perhaps modulated tooth of inclined angle alpha balzed grating, 22 height of the modulated duty ratio of grid 21, tooth or face angle β.
For tooth to modulate helical teeth Surface gratings is high, tooth height changes, root with grating in the position of waveguide surfaceAccording to processing method and the mode of process implementing, the side shown in Fig. 7 A on the basis of grating bottom of the tooth portion is can be used in specific structureMethod shown in method or Fig. 7 B on the basis of grating tooth crest is modulated.Available lithography method includes electron beamEtching, reactive ion beam etching (RIBE), magnetic intensified response ion etching, high density plasma etch, inductive coupling type plasmaEtching, transformation coupled plasma etching and electron cyclotron resonance etching.Modulate tooth height can by control electron beam or fromBeamlet is realized in the etch period and exposure intensity of mother matrix substrate.Grating knot for the demand for adapting to scale of mass production, on mother matrixStructure can be copied in the resin material of duplicate plate by nano-imprint method, casting, die pressing, injection die pressing etc..
By taking a modulation helical teeth Surface gratings of refractive index n=1.7 as an example, this grating has 12 depth modulationsRegion.Table 1 lists the relevant parameter of system and grating, and table 2 lists the depth of profile of grating in each modulation areas.Such as figureShown in 8A, the diffraction efficiency of this depth modulation helical teeth Surface gratings is significantly increased with the increase of grating depth, such as Fig. 8 BShown, the output light flux in each region is invariable, thus user it is seen that brightness uniformity image.Ratio in contrastIt is the constant non-modulation helical teeth Surface gratings of tooth depth, modulation and non-modulation situation output total light flux having the same.It can clearly be seen that from the comparison diagram of Fig. 8 A and Fig. 8 B, non-modulation helical teeth Surface gratings have constant output diffractionEfficiency, therefore since light energy is distributed the characteristic of output in the effective coverage of waveguide, output light flux within the scope of emergent pupil withPropagation distance is successively decreased rapidly, thus exports image brightness irregularities within the scope of emergent pupil, influences user's visual experience.
Table 1
| n | 1.7 |
| λ | 525nm |
| Λ | 370nm |
| w | 185nm |
| ff | 0.5 |
| α | 45° |
Table 2
| N | hN(nm) |
| 1 | 37 |
| 2 | 39 |
| 3 | 41 |
| 4 | 43 |
| 5 | 46 |
| 6 | 50 |
| 7 | 58 |
| 8 | 70 |
| 9 | 95 |
| 10 | 134 |
| 11 | 199 |
| 12 | 290 |
The present invention also can operate in the optical waveguide based on two-dimensional and periodic diffraction structure, below to be spread out based on two-dimensional linearEjected wave lead and the augmented reality device based on two-dimentional column structure diffraction waveguide for be explained such optical waveguide work it is formerReason.Fig. 9 A and 9B are respectively the front view of two-dimensional linear diffraction waveguide 23 and two-dimentional column structure diffraction waveguide 26 and optical path.TwoThe input area 24 of dimensional linear diffraction waveguide 23 and the input area 27 of two-dimentional column structure diffraction waveguide 26 can be used one-dimensional linear and spread outStructure is penetrated, two-dimensional and periodic diffraction structure can also be used.The output area 25 of two-dimensional linear diffraction waveguide 23 and two-dimentional column structureThe output area 28 of diffraction waveguide 26 uses two-dimensional and periodic diffraction structure.Two-dimensional and periodic diffraction structure is at least in two directionsWith periodicity, periodically two or more directions are presented can be orthogonal, can also be at other angles.With one-dimensional diffracted waveIt leads while needing to transmit diffraction optical element and output diffraction optical element is different come the two-dimensional expansion for completing emergent pupil, due to moreThe periodicity in direction, two-dimensional and periodic diffraction structure make the light being totally reflected in waveguide-based bottom only need to be in two-dimensional linear diffractionThe two-dimensional expansion of emergent pupil can be completed in the output area 25 of waveguide 23 or the output area 28 of two-dimentional column structure diffraction waveguide 26, obtainsLarge-sized form.
Following five kinds of two-dimensional and periodic diffraction structures are listed in Figure 10：Pyramid, gridiron pattern, column, linear skewed crossingAnd linear orthogonal, but available structure is not limited only to this.It is similar with above-mentioned one-dimensional linear diffraction grating, if two-dimensional and periodicThe dimensional parameters of diffraction structure remain unchanged namely structure is non-modulation, and diffraction efficiency is kept constant, then light is in two-dimentional diffractionThe output light flux of every step successively decreases during the two-dimensional expansion substep output of output area, therefore to use within the scope of the emergent pupil of waveguideThe image brightness that family is presented is uneven.When the present invention is used in the optical waveguide based on two-dimensional and periodic diffraction structure, using modulationThe dependency structure parameter of two-dimensional and periodic diffraction structure, so that coupling output diffraction efficiency gradually becomes during two dimensional expansion pupilsChange, realizes the homogenization of output brightness of image.May be selected, which influences apparent structural parameters to diffraction efficiency, is modulated.
By taking two-dimentional column diffraction structure as an example, Figure 11 A and 11B give its structural schematic diagram and relevant parameter.CoordinateThe X-axis of system and the direction of period 1 are parallel, and Z axis is vertical with waveguide surface.Relevant structural parameters have height h, column diameter d,One periods lambda1With second round Λ2.The incident direction of light is under coordinate system shown in Figure 12 with polar angle θ and azimuthTo determineJustice.Due to having periodically in both direction, the diffraction time of two-dimensional structure is indicated in the form of (m, n).Two-dimentional column is spread outPenetrating structure can be by modulation duty cycle ff1=d/ Λ1And ff2=d/ Λ2Or tooth high h changes diffraction efficiency.It is modulation belowOne design example of duty ratio, wherein the refractive index n=1.7 of column diffraction structure, has the region of 12 duty ratio modulations.Table 3 lists the relevant parameter of system, diffraction structure and incidence angle, and table 4 lists column structure in each modulation areasDuty ratio.This design output diffraction time is (1,1), and Figure 13 A gives duty ratio modulation and non-modulation column structure in this gradeThe comparison of secondary lower transmission diffraction efficiency, the diffraction efficiency of the two-dimentional column diffraction structure of this duty ratio modulation with duty ratio increaseAnd significantly increase, it is seen that sensibility of such diffraction structure diffraction efficiency to duty ratio.As shown in Figure 13 B, having the sameUnder the conditions of exporting total light flux, the output light flux of the constant non-modulation two-dimentional column diffraction structure of duty ratio propagate in waveguide andGradually successively decrease during distribution output, exports image brightness irregularities within the scope of emergent pupil, influence user's visual experience.And dutyIt is more invariable than output light flux of the two-dimentional column diffraction structure of modulation in each modulation areas, thus user sees it being brightUniform picture is spent, user's visual experience is obviously improved.
Table 3
Table 4
| N | d(nm) | ffN |
| 1 | 127.05 | 0.220 |
| 2 | 129.36 | 0.224 |
| 3 | 132.83 | 0.230 |
| 4 | 136.29 | 0.236 |
| 5 | 139.76 | 0.242 |
| 6 | 144.38 | 0.250 |
| 7 | 149.00 | 0.258 |
| 8 | 155.93 | 0.270 |
| 9 | 165.17 | 0.286 |
| 10 | 175.56 | 0.304 |
| 11 | 192.89 | 0.334 |
| 12 | 232.16 | 0.402 |
Basic principles and main features and advantages of the present invention of the invention have been shown and described above.The skill of the industryArt personnel it should be appreciated that the present invention is not limited to the above embodiments, the above embodiments and description only describeThe principle of the present invention, without departing from the spirit and scope of the present invention, various changes and improvements may be made to the invention, theseChanges and improvements all fall within the protetion scope of the claimed invention.The claimed scope of the invention by appended claims andIts equivalent thereof.