CN101586779A - Design method of LED homogeneous reflector based on optical extension and use thereof - Google Patents

Abstract

The invention discloses a design method of LED homogeneous reflector based on optical extension and use thereof; general mathematic models are established by using the theory of optical extension conservation in non-imaging optics according to the luminescence properties of LED light source and the analysis of special target plane illumination requirement; and the reflection surface is a curved surface determined by curved rotation limited by the curvilinear equation in the description. Uniform illumination can be realized by using a single reflector, and higher illumination homogeneity and energy utilization rate are obtained on the target plane. The design method of reflector with uniform illumination in the invention can be used for system of uniform illumination in high requirement, such as microscope illumination system, indoor illumination and optical projection system using LED as light source. Therefore, the invention not only can simplify the structure of the system but also can increase the utilization rate of optical energy, and the illumination homogeneity also can be greatly improved. Therefore, the invention has very good application prospect.

Description

Method for designing and application based on the even illumination reflector of LED of optical extend

Technical field

The present invention relates to the LED lighting engineering, particularly a kind of method for designing of even illumination reflector and the reflector that adopts this method for designing to obtain.

Background technology

Along with the development of semiconductor lighting technology, LED is as a kind of emerging artificial light sources, because advantage such as its volume is little, and energy consumption is low, and monochromaticjty is good has shown very wide application prospect.LED replaces conventional light source just gradually, becomes light source of new generation.But, LED remains in many deficiencies at present, single led total light energy is lower, and most of LED product all has the lambertian distribution luminosity curve at Vernonia parishii Hook angle, therefore can not be used for illuminator separately, in most of application scenarios, the optical element that people need add cooperates with LED, realizes even illumination within the specific limits.

It is that quadratic form reflecting condenser and the optical wand of mentioning in the patent documentation of CN1948823A and CN2760613Y spared light that publication number is arranged in the prior art.Be that employing reflective compound eye or the transmission-type fly's eye of mentioning in the patent documentation of CN1554983A and CN2891006Y spared means such as light also just like publication number.

Though but these methods based on traditional image optics principle have solved the problem of the even illumination in the certain limit, but because the restriction of himself character, there is certain collection angle, therefore can not realize the purpose of LED luminous energy high usage, optical wand even light effect when long enough is better, is that cost wastes energy to sacrifice the efficiency of light energy utilization still, simultaneously the whole system more complicated, and becoming today of trend day by day in microminiaturization, the uniformity limitation of traditional illumination system also becomes clear day by day.

Also having human nonimaging optics theory to realize even design of Lighting, utilize TEDs (Tailored Edge-ray Device) method for designing as J.M.Gordon andAri Rabl, evenly throws light in design axial symmetry reflector realization far field.People such as Ding Yi set up partial differential equations based on the catadioptric equation and the conservation of energy, obtain being used for even free-form surface lens and the free-form surface reflector that throws light on by numerical solution, but for rotational symmetric reflector design, this method are comparatively loaded down with trivial details.

The increasing reflector structure of application along with the auxiliary design of three-dimensional adopts equation to express in addition, realize in industrial production by the auxiliary design of three-dimensional afterwards, in the Chinese invention patent 200510037129.0 a kind of back light system and reflection shield thereof are disclosed for example, comprise a plurality of light sources, one reflection shield and a LGP, this LGP comprises incidence surface, be connected in the exiting surface of this incidence surface and with respect to the bottom surface of this exiting surface, this light source this incidence surface relatively is provided with, this reflector has a plurality of reflector elements, these a plurality of reflector elements are accommodated this a plurality of light sources respectively, each reflector element has two reflectings surface that are oppositely arranged, and these two reflectings surface and cross sectional shapes this two reflectings surface relative with this incidence surface are limited by a particular equation in polar coordinates.

But the structure of the reflector of prior art and LGP combination is too complicated, processing inconvenience, although the problem that adopts the optical transmission device to solve even illumination is also arranged, the optical transmission device can consume part energy, and capacity usage ratio is very low.

Summary of the invention

The present invention is according to the distribution requirement of led light source characteristic and objective plane illumination, according to the optical extend conservation theory in the nonimaging optics, provides the method for designing of a kind of even illumination and reflector simple for structure.

A kind of method for designing of the even illumination reflector of LED based on optical extend comprises:

(1) be that initial point is set up polar coordinate system with the led light source,

(2) need to determine the illuminated target zone at the opposite direction place of the beam emissions of led light source;

(3) utilize following curvilinear equation to set up the reflecting surface curve at the positive direction place of the beam emissions of led light source,

$\frac{\mathrm{dr}}{\mathrm{d\θ}}=r\tan \left(\frac{\mathrm{\θ}-\arctan \frac{r\sin \mathrm{\θ}-\frac{\sin \mathrm{\θ}}{\sin {\mathrm{\θ}}_{\max }}R}{r\cos \mathrm{\θ}+x_0}}{2}\right)$

In the formula:

R is the distance between any point P on led light source light-emitting area center and the reflecting surface;

θ is that led light source light-emitting area center is transmitted into the light of any point P on the described reflecting surface and the angle of led light source light-emitting area normal;

θ _MaxThe maximum angle of divergence for led light source light-emitting area output beam;

x ₀Be the distance between illumination target plane and the led light source light-emitting area center;

R is the radius of field of illumination on the objective plane;

(4) the reflecting surface curve is obtained the reflecting surface of the described even illumination reflector of LED based on optical extend around led light source light-emitting area centre normal rotation.

In the method for designing of the present invention with the position x of illumination zone R and the relative led light source of target face ₀Structural parameters as equation.Because different illumination zone R and different position x ₀, can select according to concrete lighting requirement, enlarged the range of application of described method for designing.

When carrying out designing and calculating, can:

A) utmost point footpath r that selects initial point for the reflector culminating point to led light source light-emitting area center apart from r ₀, θ is 0 ° of beginning, to θ _MaxFor terminal point finishes;

Perhaps b) selecting initial point is h from reflector half bore, the utmost point footpath r of this moment ₀=h/sin θ _Max, polar angle is θ _Max, to θ be 0 ° of end.

Led light source of the present invention can be various power, the light emitting diode of different colours (LED).The light emitting diode light intensity distributes and has lambert's type or the distribution of class lambert type.The reflectivity of reflector adopts reflectance coating commonly used to get final product.

Led light source is luminous towards the reflecting surface that scribbles reflectance coating, and after reflection, almost all light can both arrive objective plane, has improved the utilization rate and the illuminance uniformity of luminous energy.

The present invention also provides the even illumination reflector of the LED based on optical extend of utilizing described method for designing to obtain, comprise led light source and be used for the light of led light source emission is reflexed to the reflector that needs the illuminated target plane that described reflector two-dimensional silhouette curve is limited by following equation:

$\frac{\mathrm{dr}}{\mathrm{d\θ}}=r\tan \left(\frac{\mathrm{\θ}-\arctan \frac{r\sin \mathrm{\θ}-\frac{\sin \mathrm{\θ}}{\sin {\mathrm{\θ}}_{\max }}R}{r\cos \mathrm{\θ}+x_0}}{2}\right)$

In the formula:

R is the distance between any point P on led light source light-emitting area center and the reflecting surface

θ is that led light source light-emitting area center is transmitted into the light of any point P on the described reflecting surface and the angle of led light source light-emitting area normal;

θ _MaxThe maximum angle of divergence for led light source light-emitting area output beam;

x ₀Be the distance between illumination target plane and the led light source light-emitting area center;

R is the radius of field of illumination on the objective plane;

Wherein said curved surface is the curve that above-mentioned curvilinear equation is determined, by forming around the rotation of led light source light-emitting area centre normal.

Described reflecting surface can adopt general reflectorized material of the prior art to make, and reflecting surface is a concave surface, with the luminous energy of led light source to around expansion, make Energy distribution even.Led light source is luminous towards the reflecting surface direction, and after reflection, almost all light can both arrive objective plane, has improved the utilization rate and the illuminance uniformity of luminous energy.

Optical extend is (can be referring to W.Cassarly. " Non-imaging Optics:Concentration and Illumination, " OSA Handbook ofOptics, 2 of important notion in the nonimaging optics theory ^NdEdition, Vol 3.Chap 2.McGraw-Hill, New York (2001) .), the integration of the solid angle that area and light beam occupied that light beam passed through is described, be used to weigh desired area and solid angle, determine the collection of energy rate of system, thereby determine structural parameters.Optical extend is defined as:

U＝n ²∫∫cos?θdAdΩ(1)

N is a refractive index in the formula, and θ is the angle of the central shaft of the normal of infinitesimal area dA and infinitesimal solid angle d Ω.

For desirable optical system, do not consider to reflect, under the situation of losses such as reflection, scattering, absorption, light beam is through optical extend conservation after the optical system.The optical extend coupling is most important Consideration in the non-imaging optical system design.The smaller the better for the light source optical extend, and should be the bigger the better for the optical extend of optical element.But the increase of propagation might not produce the raising of the energy efficiency of same degree, also can cause the increase of system complexity and cost simultaneously.Therefore need reasonably design illuminator, control light trend realizes the coupling of optical extend, thereby obtains the higher efficiency of light energy utilization and required illumination uniformity.

The even illumination reflector of LED that the present invention is based on optical extend is based on that optical extend conservation theory designs in the nonimaging optics theory, promptly in desirable optical system, do not consider to reflect, under the situation of losses such as reflection, scattering, absorption, light beam is through optical extend conservation after the optical system.Optical extend for light source is the smaller the better, and should be the bigger the better for the optical extend of optical element.But the increase of propagation might not produce the raising of the energy efficiency of same degree, also can cause the increase of system complexity and cost simultaneously.Therefore need reasonably design illuminator, control light trend realizes the coupling of optical extend, thereby obtains the higher efficiency of light energy utilization and required illumination uniformity.

The present invention passes through the characteristics of luminescence of led light source and the analysis of given objective plane lighting requirement, according to the optical extend conservation theory in the nonimaging optics, set up the general mathematics model of reflector, use single reflector can realize even illumination, and on objective plane, can obtain higher illuminance uniformity and capacity usage ratio.The present invention evenly method for designing of the reflector of illumination can be used for the high evenly system of illumination of requirement, as to be used for LED be the illuminators such as microscope illumination system, room lighting, optical projection system of light source.The structure that not only can simplify system can also increase the utilization rate of luminous energy, and illuminance uniformity also is greatly improved.Therefore method for designing of the present invention has good application prospects.

Description of drawings

The surface of intensity distribution that the light emitting diode light intensity that Fig. 1 adopts for the present invention distributes and has lambert's type feature,

Abscissa is the θ angle among the figure, and ordinate is the normalization light intensity;

Fig. 2 is the principle schematic of reflector of the present invention;

Fig. 3 is used for the reflector model figure of microscope illumination system for reflector of the present invention;

Fig. 4 is the analogous diagram of microscope illumination system among Fig. 3;

Fig. 5 is the Illumination Distribution figure in the field of illumination;

Fig. 6 is the Illumination Distribution curve of level and vertical direction; The A line is represented the Illumination Distribution curve on the vertical direction among the figure; The B line is represented the Illumination Distribution curve on the horizontal direction;

The specific embodiment

Method for designing of the present invention is according to the characteristics of luminescence of led light source and the analysis of specific objective flat illumination requirement, use the optical extend conservation theory in the nonimaging optics, set up the general mathematics model of reflector, use single reflector can realize even illumination, and on objective plane, can obtain higher illuminance uniformity and capacity usage ratio.

Utilize the optical extend correlation theory, referring to Fig. 2, set up polar coordinate system, the center of lumination of light emitting diode face is put in coordinate origin (0,0), and the normal of light-emitting area is along x axle negative direction.Under polar coordinates, the differential equation of reflecting surface appearance profile is:

$\frac{\mathrm{dr}\left(\mathrm{\θ}\right)}{r\left(\mathrm{\θ}\right)}=\tan \left(\frac{\mathrm{\θ}-\mathrm{\α}\left(\mathrm{\θ}\right)}{2}\right)\mathrm{d\θ}---\left(2\right)$

θ is the angle that the led light source center is transmitted into the normal of the light of reflector any point P and lumination of light emitting diode face in the formula.

Can get according to Fig. 2

$\mathrm{\α}\left(\mathrm{\θ}\right)=\arctan \frac{r\sin \mathrm{\θ}-y}{r\cos \mathrm{\θ}+x_0}---\left(3\right)$

X in the formula ₀Be the distance of light-emitting diodes tube hub and objective plane, can select according to the difference of illumination plane position.Y is the position of dropping on behind the light process P point reflection on the objective plane.Make n=1 in the formula (1), then, can obtain light from led light source arbitrary taper θ internal reflection

U in the formula _sBe the optical extend of θ inner light source, A _sLight-emitting area for led light source.By the illumination on the objective plane that calculates θ angle correspondence

$E_t=\frac{{\mathrm{LU}}_t}{A_t}---\left(5\right)$

In the formula, L is illuminated area brightness, A _tBe the lighting area on the objective plane, U _tBe the optical extend on the objective plane.The illumination that other gets boundary point is

${\mathrm{<figure-callout\; id="0"\; label="E"\; filenames="A2009100995520012H1.png"\; state="\{\{state\}\}">E</figure-callout>}}_0=\frac{{\mathrm{LU}}_0}{A_0}---\left(6\right)$

According to optical extend conservation and equiluminous condition

U _s＝U _t

(7)

E _t＝E ₀

Obtain,

$\frac{U_s}{A_t}=\frac{U_{s0}}{A_0}---\left(8\right)$

U _S0Be θ _MaxPairing optical extend.With A _t=π y ², A ₀=π R ², U _s=π A _sSin ²θ, U _S0=π A _sSin ²θ _MaxSubstitution formula (8) obtains

$y\left(\mathrm{\&theta;}\right)=\frac{\sin \mathrm{\&theta;}}{\sin {\mathrm{\&theta;}}_{\max }}R---\left(9\right)$

In the formula, R can design according to the needs on illuminated target plane, and R is the radius of field of illumination.Formula (9) and formula (3) substitution formula (2) are obtained formula (10),

$\frac{\mathrm{dr}}{\mathrm{d\&theta;}}=r\tan \left(\frac{\mathrm{\&theta;}-\arctan \frac{r\sin \mathrm{\&theta;}-\frac{\sin \mathrm{\&theta;}}{\sin {\mathrm{\&theta;}}_{\max }}R}{r\cos \mathrm{\&theta;}+x_0}}{2}\right)---\left(10\right)$

By formula (10) as seen, can find the solution the discrete point coordinate that obtains r and θ by numerical integration method, these discrete points form a curve, curve is around the rotation of led light source light-emitting area centre normal, and the curved surface (can utilize the 3D modeling software to carry out surface fitting) that obtains being made of three-dimensional data points promptly obtains the reflecting surface of reflector.

Utilizing described method for designing to carry out reflector and make, is initial point with the led light source, the reflector culminating point to led light source light-emitting area center apart from r ₀Be 5mm, objective plane position x ₀Be 15mm, the illumination zone radius R is 45mm, and the led light source size is 1mm * 1mm, led light source angle of divergence θ _Max=90 °, luminous flux is set to 10lm, and the reflectivity of reflector is made as 1.

Led light source adopts the light emitting diode of the light distribution with lambert's type feature, the visible Fig. 1 of the surface of intensity distribution, and abscissa is the θ angle among Fig. 1, ordinate is the normalization light intensity.

According to above-mentioned data, substitution formula (10) is utilized the matlab program, uses the Runge-Kutta numerical integration method to find the solution the discrete points data that described reflector equation obtains reflector profile, obtains reflector model through rotation and three-dimensional software match, as shown in Figure 2.This moment, the bore of reflector was 63.6mm.

The reflector that obtains is used for microscope illumination system, and the analogous diagram of its reflector model figure and microscope illumination system can be referring to Fig. 3, Fig. 4.

Open led light source, light forms the hot spot that diameter is 90mm, uniformity＞85% after reflecting through reflector on objective plane.The designed reflector of the present invention is carried out ray tracing and Illumination Distribution result of calculation referring to Fig. 5, Fig. 6, and Fig. 5 is the Illumination Distribution figure in the field of illumination; Fig. 6 is the Illumination Distribution curve of level and vertical direction; The A line is represented the Illumination Distribution curve on the vertical direction among the figure; The B line is represented the Illumination Distribution curve on the horizontal direction; Reflector illuminance uniformity of the present invention has reached 90.6%, and capacity usage ratio reaches 99.6%.

Claims (2)

1, a kind of method for designing of the even illumination reflector of LED based on optical extend is characterized in that, comprising:

(1) be that initial point is set up polar coordinate system with the led light source,

(2) need to determine the illuminated target zone at the opposite direction place of the beam emissions of led light source;

(3) utilize following curvilinear equation to set up the reflecting surface curve at the positive direction place of the beam emissions of led light source,

$\frac{\mathrm{dr}}{\mathrm{d\&theta;}}=r\tan \left(\frac{\mathrm{\&theta;}-\arctan \frac{r\sin \mathrm{\&theta;}-\frac{\sin \mathrm{\&theta;}}{\sin {\mathrm{\&theta;}}_{\max }}R}{r\cos \mathrm{\&theta;}+x_0}}{2}\right)$

In the formula:

R is the distance between any point P on led light source light-emitting area center and the reflecting surface;

θ is that led light source light-emitting area center is transmitted into the light of any point P on the described reflecting surface and the angle of led light source light-emitting area normal;

θ _MaxThe maximum angle of divergence for led light source light-emitting area output beam;

x ₀Be the distance between illumination target plane and the led light source light-emitting area center;

R is the radius of field of illumination on the objective plane;

(4) the reflecting surface curve is obtained the reflecting surface of the described even illumination reflector of LED based on optical extend around led light source light-emitting area centre normal rotation.

2, the even illumination reflector of a kind of LED based on optical extend, comprise led light source and be used for the light of led light source emission is reflexed to the reflecting surface that needs the illuminated target plane, it is characterized in that: described reflecting surface is the curved surface that curve rotation that following curvilinear equation limited is determined:

$\frac{\mathrm{dr}}{\mathrm{d\&theta;}}=r\tan \left(\frac{\mathrm{\&theta;}-\arctan \frac{r\sin \mathrm{\&theta;}-\frac{\sin \mathrm{\&theta;}}{{\sin \mathrm{\&theta;}}_{\max }}R}{r\cos \mathrm{\&theta;}+x_0}}{2}\right)$

In the formula:

R is the distance between any point P on led light source light-emitting area center and the reflecting surface

θ is that led light source light-emitting area center is transmitted into the light of any point P on the described reflecting surface and the angle of led light source light-emitting area normal;

θ _MaxThe maximum angle of divergence for led light source light-emitting area output beam;

x ₀Be the distance between illumination target plane and the led light source light-emitting area center;

R is the radius of field of illumination on the objective plane;

Wherein said curved surface is that the curve negotiating that above-mentioned curvilinear equation is determined forms around the rotation of led light source light-emitting area centre normal.

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