CN104267591A - Achromatic method based on three-time exposure technology - Google Patents

Abstract

The invention provides an achromatic method based on a three-time exposure technology. The method relates to a miniature display screen, a collimating lens, a first optical grating and a second optical grating. Colored light emitted from the miniature display screen irradiates to the first optical grating after passing through the collimating lens, through modulation of the first optical grating, RGB three-color light waves can be reflected in the same direction to enter an optical waveguide, the light waves are modulated and reflected out at the second optical grating to enter human eyes, and thus colored images can be seen by the human eyes. According to the achromatic method based on the three-time exposure technology, the angle change is recorded, exposure can be conducted on the same holographic material for three times, and accordingly a grating structure capable of modulating the RGB three-color light can be obtained. A laser of 532 nm is used as a recording light source, a silver salt plate (a silver halides latex material) is selected to be used as the holographic recording material, the method is simple, effective and practical, and the method is of great economic significance to large-scale industrial production particularly.

Description

Based on three achromatic methods of exposure technique

Technical field

The present invention relates to a kind of based on three achromatic methods of exposure technique, particularly relate to a kind of based on three achromatic methods of exposure technique, belong to multispectral imaging field.

Background technology

Holographical wave guide grating utilizes grating diffration principle, by diffraction light by total reflection principle, makes it enter in substrate of glass to form waveguide to propagate, after running into another block grating, then equally by grating diffration principle, goes out to inject the eyes of people from waveguide.Such people can observe scenery at a distance through glass, can observe the image formed by waveguide again simultaneously.

Holographic recording can be called as record and the reproduction of wavefront by its physical significance, is that English physicist Denis in 1948 covers uncle proposition in 1948.Lid uncle is from theory and experimentally prove, interfere with the diffraction light wave (Object light wave) of a reference light wave and object, object light wave amplitude and phase information can be recorded completely, and interferogram can carry out diffraction to lighting light wave thus, thus reproduce original Object light wave, and the picture of object.

Wavefront record is from the interference ultimate principle theory of light, and the intensity distributions of two-beam interference is relevant in the phasic difference of two-beam, and namely isophote is equiphase difference line.If a branch of coherent light is simple light wave (such as plane wave or spherical wave), it is known at the phase mehtod of record plane, so interference strength just distributes and phase mehtod of another bundle has simple corresponding relation.Utilize the coding that the interference of reference light and Object light wave can realize Object light wave position phase.

The reproduction of wavefront is diffracted to basis with hologram to what reproduce light wave.For this reason, irradiate hologram with a branch of coherent light waves, if reproducing light wave is exactly record the reference light wave being, the reproduction of this original objects light wave just.Concerning observer, by the Object light wave of hologrm reconstruction be as broad as long from the Object light wave that original objects sends.

Light, in travel path, runs into opaque or transparent barrier, cut-through thing, and the phenomenon producing off-straight propagation is called the diffraction of light.Huygens proposes, each point on medium in wave front, can regard as and launch the wave source of wavelet, thereafter any time these wavelets envelope, be exactly this moment new wave front.Huygens-Frensel principle can describe the propagation problem of light in diffraction phenomena qualitatively.Fresnel has enriched Huygens' principle, and he proposes each bin on wavefront and can be considered the wave source of wavelet, in the superposition of the vibration of the space point P coherent vibrational that to be all these wavelets produce at this point, is called Huygens-Frensel principle.

According to the scalar diffraction theory of grating, can obtain:

D (nsin β _{diff, k}+ sin θ _inc)=k λ wherein d is the cycle of grating, and k is the order of diffraction time, and n is the refractive index of waveguide medium, and β diff, k are the kth order diffraction angle in waveguide, and θ inc is incident angle, and λ is wavelength.

Coupled wave theory is from Maxwell equation, according to the electricity of recording medium when there being modulation or optical constant, directly solving system of equations, can obtain diffraction efficiency in all cases.

Coupled wave theory hypothesis incides in volume holographic grating close to the Single wavelength light of Bragg angle, only has two-beam to be appeared in grating by hypothesis, and a branch of is incident reference light wave, and another bundle is signal light-wave.Only have and to meet or at least approximate light wave meeting Bragg condition just can be considered, other multiorder diffractive or strong run counter to being considered of Bragg condition.These hypothesis make coupled wave theory only be suitable for volume holographic grating.

Object light wave and reference light wave coherence stack, define interference field at three dimensions, if these interference fields are recorded by thick hologram recording material, then the interference fringe on hologram is then the equal strength face of three-dimensional interference field and the cross section of recording materials.The thickness of general hologram recording material is greater than interference fringe space periodic, and even the thickness of holographic material is more than 50 fringe spacings.In this case, the diffraction mechanism of plane hologram will be no longer applicable, must consider the three-dimensional character of hologram, and this hologram be based upon on three-dimensional model basis is called volume hologram.

When two-beam is incident from the same side of recording materials, to observes in the transmission direction of lighting light wave during reproduction, be called transmission-type volume hologram.Record as schemed light wave incident from the both sides of medium respectively time, then will observe from the reflection direction of lighting light wave in reality, this hologram is called reflection hologram.Dotted line in figure represents equal strength face.The point primitive volume hologram of symmetrical record, its equal strength face is one group of parallel equally spaced plane striped parallel or vertical with optical axis.

After lighting light wave enters volume hologram, there is diffraction by each some place of holographic grating, cause the Energy Coupling between incident wave and diffracted wave.Therefore describe the propagation of lighting light wave in volume hologram, the Maxwell equation in nonhomogeneous media and corresponding boundary condition must be applied.Namely coupled wave theory is so a kind of diffraction theory, and it by solving the Maxwell equation in nonhomogeneous media, thus draws the analytical expression of dissimilar Diffraction Efficiency of Volume Holograms.

Because holographic optical elements (HOE) has aberration, so be used in waveguide imaging, the aberration of generation can affect the reproduction of imaging realistic colour.The people such as L.Eisen propose and adopt graded index materials to make substrate of glass, but this kind of method implement very difficult.The people such as the Hiroshi Mukawa of Sony propose and utilize three layers of holographic emulsion layer, and every one deck latex, respectively to RGB wavelength sensitive, then makes three layers of grating, to coupling light, realizes achromatism.But this kind of requirement of method to manufacture craft is high, and consuming time, and cost is also very high.

Summary of the invention

In view of above-mentioned the deficiencies in the prior art part, the object of the present invention is to provide

In order to achieve the above object, this invention takes following technical scheme: a kind of based on three achromatic methods of exposure technique, described method comprises miniature display screen, collimation lens, the first grating and the second grating, the colored light sent from miniscope is by being irradiated to the first grating after collimation lens, by the modulation of the first grating, RGB tri-coloured light ripple is reflected into into optical waveguide with same direction, at the second grating place, light wave is modulated again to be reflected away, enter human eye, make human eye can see colored image.

The present invention also provides a kind of based on three achromatic methods of exposure technique, and described method comprises miniature display screen, collimation lens, coupling input grating, coupling output grating, holographic dry plate, substrate of glass and isosceles right-angle prism,

Described coupling input grating and coupling output grating are separately positioned on the two ends of substrate of glass;

The colored light sent from miniscope inputs grating by being irradiated to coupling after collimation lens, by the modulation of grating, RGB tri-coloured light ripple is reflected into into optical waveguide with same direction, at coupling output grating place, light wave is modulated again to be reflected away, enter human eye, make human eye can see colored image;

Described holographic dry plate is provided with substrate of glass, isosceles right-angle prism is bonded in the substrate of glass side of holographic dry plate by index liquid, select the centre wavelength of RGB, calculate the angle of two bundle plane waves and holographic dry plate normal and the angle with a prism right-angle side normal, draw the time shutter, and then produce holographical wave guide grating.

Compared to prior art, provided by the invention is change by recording angular based on three achromatic methods of exposure technique, carries out three exposures respectively, obtain the optical grating construction respectively light of RGB three kinds of colors being had to modulation to same holographic material.Have employed the laser of 532nm as recording light source, silver salt dry plate (silver halide emulsion glue material) selected by hologram recording material, simple effectively practical, is especially more added with economic implications for large-scale commercial production.

Accompanying drawing explanation

Fig. 1 is grating waveguide imaging colour killing schematic diagram;

Fig. 2 is the relation schematic diagram of total reflection condition and Bragg angle;

Fig. 3 is three exposure achromatism schematic diagrams;

Fig. 4 is two-beam interference pattern;

Fig. 5 is for reading Diffraction of light wave schematic diagram;

Fig. 6 is the schematic diagram of other restriction field angle factors;

Fig. 7 a is the experiment index path of electric torch experiment;

Fig. 7 b is electric torch original image schematic diagram;

Fig. 7 c is without achromatic electric torch image schematic diagram;

Fig. 7 d is through three exposure achromatism electric torch image schematic diagram;

Fig. 8 a is the experiment index path of colored apple experiment;

Fig. 8 b is colored apple original image schematic diagram;

Fig. 8 c is without achromatic colored Apple image schematic diagram;

Fig. 8 d is through three colored Apple image schematic diagram of exposure achromatism;

Fig. 9 a is colored tiger face original image schematic diagram;

Fig. 9 b is without achromatic tiger face image schematic diagram;

Fig. 9 c is for expose achromatic tiger face image schematic diagram through three times.

Embodiment

The invention provides a kind of based on three achromatic methods of exposure technique, for making object of the present invention, technical scheme and effect clearly, clearly, developing simultaneously referring to accompanying drawing, the present invention is described in more detail for embodiment.Should be appreciated that specific embodiment described herein only in order to explain the present invention, be not intended to limit the present invention.

Embodiment

The present embodiment is disclosed based on three achromatic methods of exposure technique,

As shown in Figure 1, the colored light sent from miniscope inputs grating by being irradiated to coupling after collimation lens to achromatic principle, and by the modulation of grating, RGB tri-coloured light ripple is reflected into into optical waveguide by with same direction.At coupling output grating place, light wave is modulated again to be reflected away, and enters human eye, makes human eye can see colored image.Crucial problem is the effect how making coupling input and output grating and make it reach to want.When adopting the two bundle plane wave methods come by interfering to make holographic grating, the angle of the cycle of grating and two bundle ripples also has wavelength to meet formula

$2\mathrm{\Λ}\sin \frac{{\mathrm{\θ}}_{\mathrm{rec}}}{2}={\mathrm{\λ}}_{\mathrm{rec}}---\left(1\right)$

Be wherein the cycle of volume holographic grating in Λ, θ _recbe two bundle plane waves angles in media as well, λ _recfor the optical wavelength of record.When volume holographic grating is taken as optical element use, demand fulfillment Bragg condition, namely

2Λsinθ _b＝λ (2)

Wherein θ _bfor Bragg angle, λ is the wavelength of lighting light wave.Process once holographic grating is produced, then the cycle of grating is a constant, therefore simultaneous formula (1), and (2), can obtain

${\mathrm{\θ}}_{\mathrm{rec}}=2\mathrm{arc}\sin \left(\frac{{\mathrm{\λ}}_{\mathrm{rec}}}{\mathrm{\λ}}\sin {\mathrm{\θ}}_b\right)---\left(3\right)$

If design Bragg angle is a constant, then can calculates the angle of two bundle plane waves, realize passing through of the lighting light wave determined.

As shown in Figure 2, want light wave is propagated in waveguide, must total reflection condition be met, namely

$\mathrm{\θ}\≥{\mathrm{\θ}}_c=\arcsin \frac{1}{n}---\left(4\right)$

θ _cbe the angle of total reflection, n is the refractive index of substrate of glass.By simple geometric relationship, can obtain so design θ=60, can calculate Bragg angle is θ _b=60 °, the centre wavelength that have selected RGB is λ _r=635nm, λ _g=532nm, λ _b=465nm.Recording wavelength is 532nm.Can pass through formula (4), the angle calculating two bundle plane waves in medium is respectively θ _r=93.26 °, θ _g=120.00 °, θ _b=166.12 °.

In order to reach the object of total reflection, in manufacturing process, need an isosceles right-angle prism.So need to calculate the angle of two bundle plane waves and holographic dry plate normal and the angle with a prism right-angle side normal, as shown in Figure 3.By simple geometric relationship and refraction law, can calculate these angles, for red centre wavelength, angle is α ₁=20 °, β ₁=45 °, for green centre wavelength, α ₂=0 °, β ₂=22 ° for blue centre wavelength, α ₃=36 °, β ₃=12 °.

From coupled wave theory, can know, Bragg condition demand fulfillment formula

cos(φ-θ ₁₀)＝K/2ζ

Wherein, for grating ripple lose angle of inclination as shown in Figure 4, θ ₁₀and θ ₂₀it is the angle of two beam recording light. for grating wave vector value, effective light wave number, n ₁the refractive index of recording materials, λ _rec' be the wavelength of recording laser.

As shown in Figure 5 when the illumination volume holographic grating of different wave length, the following condition of demand fulfillment:

$\frac{\cos (\mathrm{\φ}-{\mathrm{\θ}}_{10})}{{\mathrm{\λ}}_{\mathrm{rec}}^{\′}{n}_2}=\frac{\cos (\mathrm{\φ}-{\mathrm{\θ}}_{11})}{{\mathrm{\λ}}_{\mathrm{read}}{n}_1}---\left(5\right)$

Wherein θ ₁₁being the angle reading light wave, is λ _readread the wavelength of light wave, n ₂be the refractive index after hologram recording material exposure, because holographic material is when exposing, the degree of modulation of refractive index will be far smaller than its refractive index, so can make n ₂≈ n ₁.Simultaneous formula (4) and refraction law, the incident angle that can obtain outside waveguide is

${\mathrm{\θ}}_{\mathrm{inc}}=\arcsin \left(n\sin (\mathrm{\φ}-\arccos \left(\frac{{\mathrm{\λ}}_{\mathrm{read}}{n}_1\cos (\mathrm{\φ}-{\mathrm{\θ}}_{10})}{{\mathrm{\λ}}_{\mathrm{rec}}^{\′}{n}_2}\right)-\frac{\mathrm{\π}}{2})\right)---\left(5\right)$

Wherein n is the refractive index of substrate, because the angle going out to inject human eye of the incident angle outside waveguide and light wave is identical, so the field angle θ of definition _fOV=θ _inc.Experiment can obtain, and at general section of 430nm-495nm, 495nm-570nm, 580nm-675nm, can reach field angle is ± 10.

As shown in Figure 6, other two factors also can limit field angle, need to consider when designing.One is that angle of propagation will meet total reflection condition cos θ ₁>=1/n, wherein angle in addition also demand fulfillment, wherein d is the thickness of holographical wave guide, and 1 is the distance between coupling input grating and coupling output grating medium line.Thus all conducting light can be made can be irradiated on second block of grating, realize coupling output.

According to 1931 color systems of International Commission on Illumination (CIE), can learn

$X=k\underset{k}{\mathrm{\Σ}}P\left(\mathrm{\λ}\right)\stackrel{\‾}{x}\left(\mathrm{\λ}\right)\mathrm{\Δ\λ}---\left(6\right)$

$Y=k\underset{k}{\mathrm{\Σ}}P\left(\mathrm{\λ}\right)\stackrel{\‾}{y}\left(\mathrm{\λ}\right)\mathrm{\Δ\λ}---\left(7\right)$

$Z=k\underset{k}{\mathrm{\Σ}}P\left(\mathrm{\λ}\right)\stackrel{\‾}{z}\left(\mathrm{\λ}\right)\mathrm{\Δ\λ}---\left(8\right)$

Wherein X, Y, Z are tristimulus values, and k is coefficient, and P (λ) is spectral power, x, y, z spectral tristimulus value, can find from CIE 1931 color space.In order to obtain equal-energy white, demand fulfillment X=Y=Z.Then can from formula (6), (7), (8) calculate the beam intensity ratio of RGB tri-kinds of colors.When field angle is ± 10, three kinds of spectrum is that the ratio of 430nm-495nm, 495nm-570nm, 580nm-675nm, RGB tri-kinds of colors can calculate 1: 0.9194: 1.0336.If when the middle light wave selecting standard is 465nm, 532nm and 635nm, the ratio of RGB tri-kinds of colors can calculate 1: 1.1688: 1.9340.Holographic grating can be used for the beam intensity ratio of control RGB tri-kinds of colors for the diffraction efficiency that RGB is different.And diffraction efficiency is relevant with the time with the light intensity of exposure, if keep light intensity constant, by the record time shutter of control RGB tri-groups of gratings, then can reach the ratio of control RGB tri-kinds of light intensity, thus according to CIE color system rule, realize white light reconstruction.

In order to the feasibility of proposed method is described, Experiments of Optics are carried out.Apply the laser instrument (Oxxius 532-300-COL-PP-LAS-01462) that wavelength is 532nm.After holographic dry plate, placed isosceles right-angle prism, and utilize index liquid to be bonded.Considering the technique of holographic dry plate characteristic and the developing fixing applied in experiment, is 2mw the power setting of plane wave, and for RGB tri-kinds of colors, the time of exposure is 0.5s, 0.8s, 1.2s respectively.As shown in Figure 3, in first step exposure, the plane wave angle of two bundle incidences is α ₁=20, β ₁=45, the time shutter is 0.5s; Second step and the 3rd step angle and time shutter are α respectively ₂=0, β ₂=22,0.8s, α ₃=36, β ₃=12,1.2s.After end exposure, the incident grating that is coupled just has been produced out.Profit uses the same method, and can produce coupling output grating.Eventually pass the chemical technologies such as developing fixing, designed holographical wave guide grating.Then, the achromatism imaging of made grating is tested by Experiments of Optics.As shown in Fig. 7 (a), the light of electric torch enters waveguide by coupling input grating, after transmission, is coupled output grating and is coupled out, gather image with camera (Canon 5D mark II).Fig. 7 (b) is depicted as the original image of electric torch, and Fig. 7 (c) is by being single exposure (α ₂=0, β ₂=22) grating waveguide imaging.The lab diagram of the holographical wave guide grating image of Fig. 7 (d) made by three exposure techniques.Can see, this kind of method very effective.Also can see, some greening of top of image shown in Fig. 7 (d), some turns blue below, and these are all do not aim at accurately due to plane wave during three exposures to cause, if adopt more accurate alignment system, these all can improve or avoid.

As shown in Figure 8, Fig. 8 (a) is experimental image harvester, and by original electric torch, Fig. 8 (b) has changed the colored Apple image (12mm × 12mm) having projected light to throw light on in a colour imaging experiment in addition.From for once exposing (α ₂=0, β ₂=22) image that holographic grating waveguide gathers is as shown in Fig. 8 (c).The image of the holographical wave guide grating collection of three exposures is as shown in Fig. 8 (d).Compared with Fig. 8 (c), achromatic effect clearly.More complicated image is also tested, as shown in Fig. 9 (a), it is a colored tiger face (12mm × 12mm), utilize the holographical wave guide of single exposure to be imaged as shown in Fig. 9 (b), wine-colored ' ear ' due to the selectivity of wavelength substantially not reproduced and present black.Utilize the holographical wave guide imaging exposed for three times as shown in Fig. 9 (c), can find out redness, yellow, green is all substantially out reproduced, and the skew of color of image causes owing to not aiming at manufacturing process midplane ripple.

In an experiment, due to the factor such as activity of temperature and humidity and holographic dry plate, also have, in holographical wave guide, the diffraction efficiency detecting each wavelength is very difficult, so color proportioning is in an experiment difficult to reach the so accurate of picture theory calculate.If adopt the surveying instrument of more skilled technique and minute adjustment, the precision of color proportioning just can be controlled more accurately.Image fuzzy is that if under more stable and clean experimental situation, these all can improve or avoid because in the out-of-flatness of silver salt dry plate and experimental record, the fluctuation of air causes.Once holographical wave guide is made into device, then achromatic partial correction work can be undertaken by the software in miniscope.

Generally speaking, the present invention proposes the very simple and convenient and effective achromatism method of one.If be applied in holographical wave guide display, the making complexity of waveguide will be reduced greatly.Especially all the more so after large-scale production.In addition, in other holographic optics imaging system, also can be applied.

What the present invention proposed is change by recording angular based on three achromatic methods of exposure technique, carries out three exposures respectively, obtain the optical grating construction respectively light of RGB three kinds of colors being had to modulation to same holographic material.Have employed the laser of 532nm as recording light source, silver salt dry plate (silver halide emulsion glue material) selected by hologram recording material, simple effectively practical, is especially more added with economic implications for large-scale commercial production.

Be understandable that, for those of ordinary skills, can be equal to according to technical scheme of the present invention and inventive concept thereof and replace or change, and all these change or replace the protection domain that all should belong to the claim appended by the present invention

Claims (2)

1. one kind based on three achromatic methods of exposure technique, it is characterized in that: described method comprises miniature display screen, collimation lens, the first grating and the second grating, the colored light sent from miniscope is by being irradiated to the first grating after collimation lens, by the modulation of the first grating, RGB tri-coloured light ripple is reflected into into optical waveguide with same direction, and at the second grating place, light wave is modulated again to be reflected away, enter human eye, make human eye can see colored image.

2. based on three achromatic methods of exposure technique, it is characterized in that: described method comprises miniature display screen, collimation lens, coupling input grating, coupling output grating, holographic dry plate, substrate of glass and isosceles right-angle prism,

Described coupling input grating and coupling output grating are separately positioned on the two ends of substrate of glass;

The colored light sent from miniscope inputs grating by being irradiated to coupling after collimation lens, by the modulation of grating, RGB tri-coloured light ripple is reflected into into optical waveguide with same direction, at coupling output grating place, light wave is modulated again to be reflected away, enter human eye, make human eye can see colored image;

Described holographic dry plate is provided with substrate of glass, isosceles right-angle prism is bonded in the substrate of glass side of holographic dry plate by index liquid, select the centre wavelength of RGB, calculate the angle of two bundle plane waves and holographic dry plate normal and the angle with a prism right-angle side normal, draw the time shutter, and then produce holographical wave guide grating.