CN104320187A - Communication emission system packaged based on micro-lens array for homogenizing illumination of LED (Light Emitting Diode) - Google Patents

Abstract

The invention provides a design method of an LED (Light Emitting Diode) illumination communication light source emission (antenna) system packaged based on a micro-lens array, and the design method is mainly used for an emission system for illumination or indoor visible light communication transmission. The system adopts a plurality of LED array element chips which are symmetrical in spatial distribution, firstly, an illumination light field of an LED light source, which takes a Lambert radiation model as an emission model, is initially uniformly deformed, and then further homogenizing treatment of the luminous intensity is obtained through the micro-lens array, and light wave or an optical signal with inconspicuous change of the luminous intensity in a certain receiving area is obtained. The whole system reassigns outgoing beam of the LED light source, so that the damage of highlight to eyes is avoided and occurrence of a dark zone which does not reach the illumination requirement is avoided under the illumination requirements; a signal receiving zone is enlarged and a signal blind zone is avoided under the requirements of a transmission signal, and a micro-lens is convenient to produce and lower in cost.

Description

Based on the communications transmit system of the LED homogenize illumination of microlens array encapsulation

Technical field

The present invention relates to a kind of communications transmit system of the LED homogenize illumination based on microlens array encapsulation of applying in indoor visible light communication.

Background technology

Indoor visible light communication ((Visible Light Communication, VLC) be utilize light-emitting diode (Light Emitting Diode, LED) human eye perceives that sends of radiation less than high speed modulated signal carry out transmission information, to the Data import of transmission be needed on optical carrier, and modulate, then utilize electrooptical device to receive optical carrier demodulation with obtaining information.Compared with traditional lighting apparatus, white light LEDs has low in energy consumption, the advantage such as long service life, size are little, environmental protection.The another one outstanding advantages of white light LEDs is that the response time is very short, therefore can carry out ultra high speed data communication with LED.Visible light communication system can cover the spatial dimension that light can reach, and connects without the need to electric wire.Compared with the WLAN (wireless local area network) (WLAN) used at present, visible light communication system can utilize lighting apparatus to replace WLAN lan base station to transmit, and its communication speed can reach per second tens of million to hundreds of million.Utilize special, can the computer of sending and receiving semiotic function and personal digital assistant device, as long as the place shone at light, just can carry out transfer of data.Visible ray wireless communication technology is a kind of emerging light wireless communication technology grown up on White light LED technology.Compare with other light wireless communications with traditional radio communication, visible light communication have transmit strong, without the advantage such as electromagnetic interference, energy savings.

VLC is primarily of emission system, and transmission medium and receiving system three part form.Its emission system is formed primarily of LED light source and optical transmitting system (lens).The outgoing distribution of usual LED light source can be considered defers to Lambertian radiation model, and namely all directions light distribution is uneven.For reaching good communication and illuminating effect, many white light LED array transmitting antenna can be adopted as the transmitting antenna of communication system.Rational array antenna design can the distribution of luminous power in control room, improves the fluctuating of luminous intensity.Microlens array can carry out shaping to LED transmitted beam, reaches the homogenize process of light beam.The light signal many white light LED array of spatial distribution appropriate design launched, through the microlens array be made up of a series of lenticule, converts light beam, reaches signal and luminous intensity being uniformly distributed in space.Signal, by the wireless transmission in indoor, arrives on the receiving plane of reception antenna, to ensure that receiving plane each position in signal cover obtains the signal of equal illumination, eliminates the inhomogeneities of signal transmission in space, avoids the blind area occurring Received signal strength.

In traditional VLC emission system, the major part face geometry of LED light source that adopts symmetrical more, mainly there is some deficiency following in the light source transmitting antenna formed thus: (1) LED light source Launching Model is Lambertian radiation model, radiation of light source scope is larger, cause the angle of divergence of transmitted beam larger, the light energy losses that light source is sent is larger, reduces capacity usage ratio; (2) luminous intensity of many white light LEDs general spatial distribution is approximate meets Gaussian Profile, the distribution that rises and falls is obvious, and when making transmitting optical signal reach receiver surface, signal strength distribution is uneven, there is signal and lighting blind zone, increase the reception difficulty of signal or the loss of signal.

Summary of the invention

The invention provides a kind of method for designing be applied to based on the system of transmit antennas of microlens array encapsulation in indoor visible light communication system, this system of transmit antennas adopts the rational spatial distribution of many white LED light sources, the microlens array of the light launched again through being made up of a series of lenticule is carried out shaping, the light signal illumination of arrival receiving system is made to obtain homogenizing, to improve the stability of Signal reception, avoid receiving the fluctuating and blind area that occur signal.

This method for designing can be achieved by following technical proposals:

(1) first selected LED light source number, the light energy required for guarantee and illuminance, by theory analysis, obtain the spatial distribution position of LED light source, spread pattern and inclination angle.Then through the homogenization of microlens array, the light that emission system is sent light distribution in receiving plane is more even.

(2) utilize scalar diffraction theory analytical method, provide diffraction type microlens array beam uniformity analytical model and with the homogenize shaping of microlens array to multi-light source LED.

Owing to have employed above-mentioned implementer's case, method provided by the present invention has following advantage:

(1) microlens array be made up of a series of lenticule, can control transmission and the distribution of light beam preferably, improve the fluctuating of luminous intensity;

(2) compare ordinary optical lens, lenticule volume is little, and cost is lower, can be suitable for producing in enormous quantities;

(3) whole emission system light source adopts white LED light source, low in energy consumption, long service life, and size is little, environmental protection, and cost is low;

(4) spatial distribution of multiple white LED light source improves the efficiency of light energy utilization, decreases optical energy loss, thus energy savings, reduce costs;

Accompanying drawing explanation

Fig. 1 is many LED light sources circular array spatial distribution map;

Bin graphic when Fig. 2 is the reception of point-source of light oblique illumination;

Fig. 3 is the index path of light transmission;

Fig. 4 is microlens array analogous diagram;

Fig. 5 is the many LED light sources emission system analogous diagram based on microlens array encapsulation.

Embodiment

Below in conjunction with accompanying drawing, the present invention is described further.

The light signal distribution form given off in VLC system signal transmitting antenna is distributed with material impact to the light signal received by reception antenna.Transmitting antenna design provided by the present invention is formed primarily of multiple LED light source and lenticule group.In indoor visible light communication system, for reaching good communication and illuminating effect, usually adopt many white light LEDs array element transmitting antenna as communication light source.The reasonable layout of LED array element and microlens array to the conversion of light beam, to reach signal and luminous intensity being uniformly distributed in space.

In ordinary optical primary antenna, because the arrangement of light source exists very large light energy losses with distribution, cause capacity usage ratio to decline, and illumination on the receiving surface presents class Gaussian Profile, illuminance fluctuation ratio is larger, jitter, brings difficulty to the reception of signal and subsequent treatment.And microlens array can carry out shaping and control to light beam, reduce the waviness of illuminance, and cost is low, volume is little.The present invention is intended to rational for spatial distribution many LED light sources be utilized the encapsulation of microlens array and then realizes the homogenize process of light beam.In order to solve the problems of the technologies described above, will specifically describe from the following aspects:

(1) spatial distribution of multi-light source LED is on the impact of light intensity distributions

Figure 1 shows that the solid space distribution of LED light source circular array antenna.The design of LED array antenna is distributed on the hemisphere face that radius is d ball, mainly to the radial direction of LED with cut (ring) and design to position distribution.Cross direction profiles is designed to annular, and genesis analysis is based on the longitudinal translation of cross direction profiles.To have symmetrical array antenna for research object, it is d that LED is evenly distributed on radius _l(l=0,1,2 ..., L, d ₀=0), on annulus, l is ascending represents that radius is d successively _lthe number of plies of annulus, total L+1 layer.The LED number of every layer of distribution is N _l(N ₀=1) individual, be highly h _l.Between each LED light Zhou Yu center LED (namely the 0th layer) optical axis on l (l > 0) layer annulus, angle is θ _l, the n-th (n=1,2..., N on l (l > 0) layer annulus _l) horizontal angle of individual LED position is work as h _lwhen=0, array antenna, without radial distribution, namely becomes planar array antenna.

In order to obtain the light intensity distributions of multi-light source LED in space, first can analyze the distribution of single light source space luminous intensity, then using the principle of stacking of optical field distribution, drawing the spatial distribution of multiple light courcess luminous intensity.

1) single led light source

When the space length of beam reception plane separation LED light source is more much larger than the luminous yardstick of LED light source itself (mostly being mm magnitude), when the large I of LED light source self is ignored, LED light source can be considered point-source of light.Therefore the light intensity distributions of single led light source in space is just equivalent to the light distribution of point-source of light.

Point-source of light S is receiving the geometrical relationship of bin dS as shown in Figure 2, if light source luminescent optical axis is θ with receiving bin dS normal angle, if light source S is Lambertian radiation model, the spatial light radiation of point-source of light is the solid angle subtended angle scope of 2 π.Irradiation face unit are dS to the solid angle of point-source of light S is

$d_{\mathrm{\Ω}}=\frac{\mathrm{dS}\cos \mathrm{\θ}}{r^2}---\left(1\right)$

The luminous flux that point-source of light sends in this solid angle is

$d_{\mathrm{\Φ}}=I{d}_{\mathrm{\Ω}}=I\frac{\mathrm{dS}\cos \mathrm{\θ}}{r^2}---\left(2\right)$

R is that point source S is to the distance receiving bin dS.So, the illuminance on bin dS

$E=\frac{\mathrm{d\Φ}}{\mathrm{dS}}=\frac{I\cos \mathrm{\θ}}{r^2}---\left(2\right)$

Wherein I represents the light distribution of LED.

For Lambertian radiation model, the light distribution expression formula of LED is

I(θ)＝I ₀cos ^mθ (4)

When getting half-value angle θ=θ _1/2time, can obtain

$m=\frac{-\ln 2}{\ln \left(\cos {\mathrm{\θ}}_{1/2}\right)}---\left(5\right)$

When in LED illumination to receiving plane, the Illumination Distribution in this plane

$E(r,\mathrm{\θ})=E_0\left(r\right){\cos }^m\mathrm{\θ}=\frac{I_0}{r^2}{\cos }^{m+1}\mathrm{\θ}---\left(6\right)$

2) many LED light sources

By the spatial light Illumination Distribution formula of above-mentioned single led light source, according to the Optical Field Superposition principle that spatial light Illumination Distribution is deferred to, the spatial light Illumination Distribution of many LED light sources array can be derived, be shown below:

$E(x,y,z)=\underset{i=0}{\overset{N}{\mathrm{\Σ}}}{E}_i(x_i,y_i,z_i)---\left(7\right)$

In formula, E (x, y, z) for LED array is in the illuminance at spatial point (x, y, z) place, E _i(x _i, y _i, z _i) be the illuminance of i-th LED at spatial point (x, y, z) place, N is the number of light source led in LED array.

The spatial distribution coordinate of each LED light source in each layer according to Fig. 1, can obtain the spatial light Illumination Distribution under rectangular coordinate system in space, and the intensity of illumination distribution obtained is the function about spatial point coordinate.

According to the spatial light Illumination Distribution formula drawn, mathematical knowledge is used to illuminance formula, carries out relevant extreme value computing, illuminance is changed in certain spatial dimension very little, and use relevant simulation software to carry out assistant analysis to functional digraph, calculate.Thus draw the proportional space distribution form of the LED light source that illuminance fluctuating is less.

(2) beam uniformity of microlens array

Microlens array is the optical element that in arrayed optics, a class is important, its normally a series of aperture at several micron to the micro lens of hundreds of micron by the lens arra of certain rule at plane or curved surface periodic arrangement composition, Figure 4 shows that microlens array.

The optical shaping principle of microlens array can be divided into refraction and diffraction two kinds according to the difference of lens, and therefore its design theory is according to lenticular dissimilar also different.The lenticular optical principle of refractive is the refraction based on light, its design is based on theory of geometric optics, and diffraction microlens is a kind of pure phase position diffraction optical element of relief type, when not considering its reflection and absorption loss, its amplitude transmittance is 1, it is the diffraction principle based on light, and therefore its design is then theoretical according to diffraction optics, and what extensively adopt at present is scalar diffraction theory.

Microlens array not only has the basic function such as focusing, imaging of conventional lenses, and has the advantages that cell size is little, integrated level is high, and the function making it can complete traditional optical elements cannot to complete, is thus widely used use.Diffraction microlens and classical optics elements combination can improve its optical property (visual field and angular aperture) parameter and image quality (contrast and resolution), can also realize the dispersion compensation with classical element.

First set light source as point-source of light, point-source of light sends spherical wave, and through microlens array, light arrives receiving plane, and index path as shown in Figure 3.P ₀for point-source of light place plane, P is receiving plane, P ₁for face, microlens array place.If microlens array center is the initial point of rectangular coordinate system in space, light is along z-axis forward-propagating, and the space coordinates of point-source of light is (x ₀, y ₀, u), the coordinate that light enters microlens array front surface is (x ₁, y ₁, 0), light after microlens array from point (x ₂, y ₂, 0) and outgoing, then light arrives (x, y, the v) point on receiving plane P, and consider that lenticule is very thin here, thickness is ignored.

The light field complex amplitude of light source of setting up an office is E ₀(x ₀, y ₀, u), spherical wave any point (m capable n row the sub-lens) (x on microlens array input face sent by this point can be obtained according to the fresnel diffraction theory in scalar diffraction theory ₁, y ₁, 0) and the light field COMPLEX AMPLITUDE at place:

$E_{1\mathrm{mn}}(x_1,y_1)=\frac{1}{\mathrm{j\λu}}\exp (-\mathrm{jku})E_0(x_0,y_0)\exp \{-j\frac{k}{2u}[{(x_0-x_m-x_{1m}^{\′})}^2+{(y_0-y_n-x_{1n}^{\′})}^2\left]\right\}---\left(8\right)$

Wherein, wave number λ is the wavelength of light wave.(x _m, y _n) be the centre coordinate of mn lenticule unit, (x ' _m, y ' _n) be the coordinate of respective point under lenticule unit coordinate system, (x ₂, y ₂, 0) and be the coordinate of respective point in system coordinate system in the output face of lenticule unit, (x, y, v) is for light is at the spatial point coordinate in the face of investigation.Wherein, (x ₁, y ₁), (x _m, y _n) and (x ' _m, y ' _n) relational expression be:

x ₁＝x _m+x′ _1m (9)

Y ₁=y _n+ y ' _1n(10) relational expression in like manner, between lens output face corresponding coordinate is:

x ₂＝x _m+x′ _2m (11)

y ₂＝y _n+y′ _2n (12)

Because each lenticule unit is mutually optoisolated, so the light wave incided in microlens array surface separately by each lenticule unit, and then will propagate in the output face of array.Like this, optical field distribution in mn microlens array unit output face, only depend on the field distribution of incident light wave on this unit input face, and have nothing to do with the field distribution of other unit, incident light wave, through this microlens array unit, is approximately through thin lens outgoing, outgoing light wave is through fresnel diffraction, the optical field distribution E at point (x, y, v) place on receiving plane can be obtained _mn(x, y), this optical field distribution is single lenticular effect, because each lenticule unit is mutually optoisolated, so point-source of light is by the superposition of microlens array optical field distribution E (x, y) on the receiving surface for the institute's third contact of a total solar or lunar eclipse field distribution on the receiving surface of each lenticule.

$E(x,y)=\underset{n=1}{\overset{N}{\underset{m=1}{\mathrm{\Σ}}}}{E}_{\mathrm{mn}}(x,y)---\left(13\right)$

Thus the light intensity distributions that can be obtained on receiving plane by the optical field distribution on receiving plane is:

$I(x,y)=\underset{n=1}{\overset{N}{\underset{m=1}{\mathrm{\Σ}}}}{\left|E_{\mathrm{mn}}(x,y)\right|}^2---\left(14\right)$

Finally light field COMPLEX AMPLITUDE is on the receiving surface analyzed and simplified operation, if P ₀plane and P plane meet object-image relation, namely

$\frac{1}{u}-\frac{1}{v}=\frac{1}{f}---\left(15\right)$

Using formula (15) carries out abbreviation to luminous intensity I (x, y), calculates, obtains the light intensity distributions I (x, y) in receiving plane.Use MATLAB to carry out analog simulation to the light intensity distributions I (x, y) obtained, observed the fluctuating of luminous intensity by emulation experiment, thus obtain beam uniformity result.

According to above analysis and derivation, the Homogenization Treatments of microlens array to light beam light intensity can be obtained, the unsteadiness of the optical signal transmission avoiding the fluctuating of luminous intensity to cause and signal blind zone.

Utilize this optical property of microlens array, design and produce the microlens array that can be applied to and be encapsulated in many white LED light sources outside, thus obtain the uniform emission system of receiving plane light intensity distributions.Be illustrated in figure 5 the plan view of the many LED light sources emission system based on microlens array encapsulation.

Claims (2)

1. the method for designing based on the communications transmit system of the LED homogenize illumination of microlens array encapsulation, it is characterized in that: first selected LED light source number, light energy required for guarantee and illuminance, by theory analysis, obtain the spatial distribution position of LED light source, spread pattern and inclination angle.Then through the homogenization of microlens array, the light that emission system is sent illumination patterns in receiving plane is more even.

2. the method for designing of the communications transmit system of a kind of LED homogenize illumination based on microlens array encapsulation according to claim 1, it is characterized in that: utilize scalar diffraction theory analytical method, give diffraction type microlens array beam uniformity analytical model and refractive microlens array beam uniformity analytical model.