CN102681066A - High-efficient wide-angle coupling grating - Google Patents

Abstract

Translated fromChinese

一种高效率宽角度的耦合光栅。包括闪耀光栅结构的基底，在基底的斜面上，镀折射率、厚度不完全相同的三层膜，第一层膜和第三层膜的折射率相同，第二层膜的折射率小于第一层膜和第三层膜。第一层膜的厚度大于第二层膜，第二层膜的厚度大于第三层膜，在膜层上方粘合透明的光学胶，与耦合光束的出射介质相连。耦合光栅的周期，与入射波长及出射介质的折射率相关。在入射波长为532nm，出射介质的折射率为1.52时，周期为410nm。当光束垂直入射时，耦合效率接近97%。当光束的纵向角在[-8°，12°]、横向角在[-15°，15°]内变化时，耦合效率大于93%。本发明的耦合光栅可在宽入射角的范围内，高效率的耦合光束。该光栅可应用于大视场的衍射屏显系统。

A high-efficiency wide-angle coupling grating. The substrate including the blazed grating structure, on the inclined surface of the substrate, three layers of films with different refractive indices and thicknesses are plated, the refractive index of the first layer and the third layer are the same, and the refractive index of the second layer is smaller than that of the first layer. layer and third layer. The thickness of the first layer of film is greater than that of the second layer of film, the thickness of the second layer of film is greater than that of the third layer of film, transparent optical glue is glued on the film layer, and connected with the outgoing medium of the coupled light beam. The period of the coupling grating is related to the incident wavelength and the refractive index of the outgoing medium. When the incident wavelength is 532nm and the refractive index of the exiting medium is 1.52, the period is 410nm. When the beam is vertically incident, the coupling efficiency is close to 97%. When the longitudinal angle of the beam is within [-8°, 12°] and the transverse angle is within [-15°, 15°], the coupling efficiency is greater than 93%. The coupling grating of the invention can couple light beams with high efficiency in a wide range of incident angles. The grating can be applied to a diffraction screen display system with a large field of view.

Description

The wide-angle coupling grating of high-level efficiency

Technical field

The present invention relates to diffraction screen and show the field, relate in particular to a kind of diffraction screen and show in the system, the coupling grating of high-level efficiency coupling imaging beam at big visual field, small size.

Background technology

Show the field at diffraction screen, the system design of the big visual field of small size has become trend, and especially the wear-type diffraction screen shows, and more requires small volume and less weight.As shown in Figure 1, traditional approach is the imaging beam with each visual field, and incident has in the waveguide plate on wedge shape inclined-plane behind collimation, and the coupling energy of light beam can be near 100%.But require imaging source to tilt to place, waveguide plate needs the xsect of broad, has increased the volume and weight of system.As coupling element, imaging beam can the incident of vertical waveguide face, behind the light beam generation diffraction, propagates in the waveguide inner total reflection with blazed grating for Fig. 2.This design can reduce volume and weight, but the coupling efficiency of blazed grating generally is lower than 70%, and bigger when the powerful and influential visual field of asking of screen, promptly during incident angle variation range broad, the coupling efficiency of part angle can reduce to 30%, has lost more projectile energy.

Summary of the invention

The objective of the invention is to solve existing diffraction screen and show in the system, the coupled system of small size is in the imaging scope of big visual field; Can't realize high diffraction coupling problems; Provide a kind of high-level efficiency wide-angle coupling grating, can embed in the waveguide, form the light beam coupling system of small size; And in 20 ° * 30 ° field range, the coupling efficiency greater than 93% is provided.

The wide-angle coupling grating of high-level efficiency provided by the invention comprises the substrate of blazed grating structure, in substrate, plates refractive index, the incomplete same trilamellar membrane of thickness, i.e. first tunic, second tunic and trilamellar membrane.First tunic is identical with the refractive index of trilamellar membrane, and the refractive index of second tunic is less than first tunic and trilamellar membrane.The refractive index of first tunic and trilamellar membrane greater than the refractive index of 2.4, the second tunics less than 1.4.

By the direction of substrate to emergent medium, the thickness of rete changes according to the rule of attenuation gradually, the thickness of first tunic greater than the thickness of 100nm, second tunic greater than 60nm and less than the thickness of 100nm, trilamellar membrane less than 60nm.

The rete top is that trilamellar membrane and light beam emergent medium are bonding.The light beam emergent medium is generally waveguide.The refractive index of emergent medium is less than first tunic and trilamellar membrane.

The substrate of coupling grating presents the structure and morphology of blazed grating.The grooved of blazed grating section can be single blazed grating, and the blazed grating line of rabbet joint on one side tilts with the bottom surface, one side the line of rabbet joint vertical with the bottom surface; Also can be double balzed grating, the blazed grating line of rabbet joint and bottom surface on one side tilts, and the line of rabbet joint of another side also tilts with the bottom surface.Base material is a metal.

The cycle of coupling grating is decided by the wavelength of incident beam, and the relation of cycle and wavelength is: cycle=wavelength/(n * sinA), wherein n is the refractive index of emergent medium; When A is light beam vertical incidence grating surface, the angle of first-order diffraction light beam and grating surface normal.A is greater than the aerial cirtical angle of total reflection of emergent medium.

Advantage of the present invention and good effect:

And comparing with prior art, high-level efficiency wide angle coupling grating provided by the invention can form the coupled system of small size, in the imaging scope of big visual field, realizes high efficiency light beam coupling.

Description of drawings

Fig. 1 is an existing wedge shape inclined-plane coupled system.

Fig. 2 is existing blazed grating coupled system.

Fig. 3 is the monocycle structural drawing of coupling grating of the present invention.

Fig. 4 is the coupled light beam synoptic diagram of coupling grating of the present invention.

Fig. 5 be coupling grating of the present invention under wide angle incident, the distribution plan of diffraction efficiency.

Among the figure, the 1st, waveguide plate, the 2nd, the wedge shape inclined-plane, the 3rd, blazed grating, the 4th, the substrate of blazed grating structure, 5 is that first tunic, 6 is that second tunic, 7 is trilamellar membranes, the 8th, emergent medium, the 9th, coupling grating.

Embodiment

Fig. 3 is the monocycle structural drawing of coupling grating of the present invention.This coupling grating is made up of substrate, multilayer film, emergent medium.Whereinsubstrate 4 presents the trench structure of blazed grating.In the present embodiment,substrate 4 is single blazed gratings, and the blazed grating line of rabbet joint on one side tilts with the bottom surface, one side the line of rabbet joint vertical with the bottom surface.Blazing angle is 30 °.The material ofsubstrate 4 is argents.

On the inclined-plane ofsubstrate 4, platefirst tunic 5,second tunic 6, trilamellar membrane 7 successively.In the present embodiment, the refractive index ofground floor rete 5 and trilamellar membrane 7 is that the medium of 2.5, thesecond tunics 6 is 1.38.

The plated film ofground floor rete 5,second layer rete 6, trilamellar membrane layer 7 is even, and the upper and lower surface of rete is all parallel with the inclined-plane of substrate 4.The thickness of first tunic is greater than the thickness of second tunic, and the thickness of second tunic is greater than the thickness of trilamellar membrane.In the present embodiment, the thickness of first tunic is 120nm, and the thickness of second tunic is 100nm, and the thickness of trilamellar membrane is 50nm.

Emergent medium 8 and trilamellar membrane 7 are bonding, andemergent medium 8 is the transparent material of low-refraction, and the refractive index of emergent medium is less than first tunic and trilamellar membrane.In the present embodiment, the refractive index of emergent medium is 1.52.

As shown in Figure 4,coupling grating 9 is bonding throughemergent medium 8 andwaveguide plate 1, and light beam is by the direction incident perpendicular to coupling grating, and behind diffraction, total reflection takes place in waveguide plate the first-order diffraction light beam, continues to propagate.

Among Fig. 4, when light beam changed in the paper of instructions, the angle of variation was referred to as longitudinal angle b; The angle that light beam changes in the plane vertical with paper is referred to as lateral angle a.

The cycle of coupling grating is to be decided by the wavelength of incident beam.The relation of cycle and wavelength is: cycle=wavelength/(n * sinA), wherein n is the refractive index of emergent medium; When A is light beam vertical incidence grating surface, the angle of first-order diffraction light beam and grating surface normal.A is greater than the aerial cirtical angle of total reflection of emergent medium.In this example, wavelength is 532nm, and n is 1.52, and A is 60 °.Through calculating, obtaining cycle T is 410nm.

When changing in [15 °, 15 °], high coupling efficiency is near 97% at [8 °, 12 °], lateral angle a for the longitudinal angle b that Fig. 5 has shown light beam, and minimum coupling efficiency is greater than 93%.The result of calculation of Fig. 5 is based on " M.G.Moharam; Formulationfor stable and efficient implementation of the rigorous coupled-wave analysis of binary gratings; J.Opt.Soc.Am.A 12; 5 (1995) ", and the theoretical method of employing rigorous coupled wave calculates.

The above is merely preferred embodiment of the present invention; Therefore do not limit claim of the present invention; Every equivalent structure or flow change of utilizing instructions of the present invention and accompanying drawing content to be done; Or directly or indirectly be used in other relevant technical fields, all in like manner be included in the scope of patent protection of the present invention.

Claims (9)

Translated fromChinese

1.一种高效率宽角度的耦合光栅，其特征在于，所述的耦合光栅包含闪耀光栅结构的基底，在基底上镀折射率、厚度不完全相同的三层膜，即第一层膜、第二层膜和第三层膜，第一层膜和第三层膜的折射率相同，第二层膜的折射率小于第一层膜和第三层膜；第一层膜的厚度大于第二层膜的厚度，第二层膜的厚度大于第三层膜的厚度，膜层上方即第三层膜与光束出射介质相粘合；光束出射介质一般为波导。1. A coupling grating with high efficiency and wide angle is characterized in that, the coupling grating comprises a base of a blazed grating structure, and three layers of films with different refractive index and thickness are plated on the base, i.e. the first layer of film, The second layer of film and the third layer of film, the refractive index of the first layer of film and the third layer of film are the same, the refractive index of the second layer of film is smaller than the first layer of film and the third layer of film; the thickness of the first layer of film is greater than the first layer of film The thickness of the second layer of film, the thickness of the second layer of film is greater than the thickness of the third layer of film, above the film layer, that is, the third layer of film is bonded to the beam exit medium; the beam exit medium is generally a waveguide.2.根据权利要求1所述的耦合光栅，其特征在于，基底呈现闪耀光栅的结构形貌；闪耀光栅断面的槽型是单闪耀光栅，闪耀光栅一边的槽线与底面倾斜，一边的槽线与底面垂直。2. The coupling grating according to claim 1, characterized in that, the substrate presents the structural appearance of a blazed grating; the groove type of the blazed grating section is a single blazed grating, the groove lines on one side of the blazed grating are inclined to the bottom surface, and the groove lines on one side perpendicular to the bottom.3.根据权利要求1所述的耦合光栅，其特征在于，基底呈现闪耀光栅的结构形貌；闪耀光栅断面的槽型是双闪耀光栅，闪耀光栅一边的槽线与底面倾斜，另一边的槽线也与底面倾斜。3. The coupling grating according to claim 1, characterized in that, the substrate presents the structural appearance of a blazed grating; the groove type of the blazed grating section is a double blazed grating, the groove line on one side of the blazed grating is inclined to the bottom surface, and the groove on the other side The lines are also inclined to the bottom surface.4.根据权利要求1所述的耦合光栅，其特征在于，基底材料为金属。4. The coupling grating according to claim 1, wherein the base material is metal.5.根据权利要求1所述的耦合光栅，其特征在于，第一层膜和第三层膜的折射率大于2.4，第二层膜的折射率小于1.4。5. The coupling grating according to claim 1, wherein the refractive index of the first film and the third film is greater than 2.4, and the refractive index of the second film is less than 1.4.6.根据权利要求1至5中任一项所述的耦合光栅，其特征在于，由基底到出射介质的方向，膜层的厚度按照逐渐变薄的规则变化，第一层膜的厚度大于100nm、第二层膜的厚度大于60nm并小于100nm、第三层膜的厚度小于60nm。6. The coupling grating according to any one of claims 1 to 5, characterized in that, from the substrate to the direction of the exit medium, the thickness of the film layer changes according to the rule of gradual thinning, and the thickness of the first film is greater than 100nm , the thickness of the second film is greater than 60nm and less than 100nm, and the thickness of the third film is less than 60nm.7.根据权利要求1至5中任一项所述的耦合光栅，其特征在于，与膜层上方粘合的出射介质是低折射率透明介质，出射介质的折射率小于第一层膜和第三层膜。7. The coupling grating according to any one of claims 1 to 5, characterized in that the outgoing medium bonded to the top of the film layer is a low-refractive-index transparent medium, and the refractive index of the outgoing medium is smaller than that of the first film and the second film. Three layers of film.8.根据权利要求1至5中任一项所述的耦合光栅，其特征在于，耦合光栅的周期由入射光束的波长而定，周期与波长的关系是：周期=波长/（n×sinA），其中n是出射介质的折射率；A是光束垂直入射光栅表面时，一级衍射光束与光栅表面法线的夹角。8. The coupling grating according to any one of claims 1 to 5, characterized in that the period of the coupling grating is determined by the wavelength of the incident light beam, and the relationship between the period and the wavelength is: period = wavelength/(n×sinA) , where n is the refractive index of the exit medium; A is the angle between the first-order diffracted beam and the normal of the grating surface when the beam is incident on the grating surface normally.9.根据权利要求8所述的耦合光栅，其特征在于，A大于出射介质在空气中的全反射临界角。9. The coupling grating according to claim 8, wherein A is greater than the critical angle of total reflection of the exit medium in air.

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