CN203744072U - LED auto high beam - Google Patents

Abstract

The utility model discloses an LED auto high beam. The LED auto high beam comprises a plurality of LED light sources, a plurality of free-form surface optical lenses, a lens bracket and a base plate, wherein the lens bracket and the LED light sources are fixed on the base plate; a plurality of holes are correspondingly formed in the lens bracket and can allow emergent light of the LED light sources to pass through; each hole in the lens bracket is provided with one free-form surface optical lens; the distance between the light-emitting surfaces of the LED light sources and the incident surfaces of the corresponding free-form surface optical lenses is determined through the height of the lens bracket. The LED auto high beam is simple and stable in structure, high in light energy utilization rate, convenient to assemble, low in cost, long in service life and good in photometric characteristics, and can meet the GB25991-2010 photometric requirement. In the utility model, the emergent surfaces of the free-form surface optical lenses of the LED auto high beam are free curve surfaces, so that the appearance molding of the whole LED auto high beam is more flexible and cam meet the modern auto lamp design requirements of beautify and streamline.

Description

A kind of LED dazzle light

Technical field

The utility model relates to LED auto lamp lighting technical field, particularly for the optical lens with free curved surface of LED dazzle light.

Background technology

In recent years, along with the continuous progress of light emitting diode (LED) technology and popularizing of applying, the application of LED in automobile lighting is also more and more general.There is the shortcomings such as efficiency is low, the life-span is short, not environmental protection in the light source of orthodox car headlamp, and the plurality of advantages such as that LED light source has is energy-conservation, efficient and environmental protection are used LED light source to substitute conventional light source by a development trend that is automotive headlamp.In recent years, along with the continuous progress of LED technology and popularizing of applying, the application of LED in automobile lighting is also more and more general.But, while making LED be applied to car headlamp, also to face complicated optical design.

Utility model content

The LED high beam that the utility model provides automobile to use, this LED dazzle light capacity usage ratio is high, and glare effect is low, and fabrication and installation are convenient, can meet the light distribution requirements of GB 25991-2010 to vapour Vehicular LED headlamp.

The utility model adopts following technical scheme:

LED dazzle light, it comprises multiple LED light sources, multiple optical lens with free curved surface, lens carrier and base plate, lens carrier and multiple LED light source are fixed on base plate, and on lens carrier, have accordingly multiple holes of passing through for LED light source emergent light, each hole place on lens carrier is all provided with an optical lens with free curved surface, and the height of the distance scioptics support between LED light source light-emitting area and the optical lens with free curved surface plane of incidence fixes.

Further, the number of described LED light source, optical lens with free curved surface is 4.

Further, in the each hole on lens carrier, be equipped with the reflector that enters the described plane of incidence after the light of the directly freedom of entry curved surface optical lens plane of incidence of LED light source outgoing is reflected.

Described optical lens with free curved surface comprises the circular plane of incidence, cylindrical side and the exit facet that seamlessly transit each other in turn, exit facet is free form surface, the effect of optical lens with free curved surface is that the light that LED light source is sent carries out luminous intensity distribution, makes this LED dazzle light can meet the light distribution requirements of GB 25991-2010.In the utility model, the design principle of 4 optical lens with free curved surface is the same, tells about below as an example of corresponding 1 LED light source of 1 optical lens with free curved surface example.

Optical lens with free curved surface is made up of transparent material, and transparent material can be PC or PMMA or optical glass.The circular flat of described lens bottom is the plane of incidence, and the free form surface at lens top is exit facet lens, and lens side is the face of cylinder for connecting lens and lens carrier.The position relationship of LED light source and optical lens with free curved surface is as follows: before the plane of incidence of lens is positioned at the light-emitting area of LED light source, and the plane of incidence of lens is parallel to the light-emitting area of LED light source, the line in the center of LED light source light-emitting area and the circular flat center of circle, lens bottom is perpendicular to lens bottom circular flat.When the light that LED light source sends passes through lens, reflect respectively at the circular flat plane of incidence of lens bottom and the free form surface exit facet at lens top, finally shine on illuminated area.

The shape of optical lens with free curved surface is determined as follows:

Set up rectangular coordinate system taking the central point of LED light source light-emitting area as origin of coordinates O, LED light-emitting area place plane is XOY plane, cross initial point and the axle vertical with XOY plane is Z axis, wherein XOZ plane is horizontal plane, with Z axis intersection point be that o and the plane that is parallel to XOY plane are illuminated area xoy plane, the some o central point that is illuminated area; Luminous energy distribution on illuminated area is what to be realized by the luminous stack of multiple LED light sources, because the relative light source of the spacing between LED light source is very little to the distance of illuminated area, can calculate luminous energy by a LED light source and distribute, adopt multiple relation directly to obtain total luminous energy and distribute; First according to dazzle light Illumination Distribution feature on illuminated area, field of illumination on illuminated area is set as to the elliptical region centered by illuminated area central point, then this elliptical region is carried out to grid division, uses energy law of conservation is divided light source solid angle again, finally use the law of refraction to obtain the free form surface of lens by numerical computations, free form surface shape is specifically determined as follows.

First the distance of target illumination identity distance LED is d=25m, and the total light flux of LED light source is Q, and central light strength is I ₀=Q/ π.Wherein for the angle of emergent ray and Z axis positive direction, θ is the projection of emergent ray on XOY plane and the angle of X-axis, and α is any point and the some line of o and the angle of x axle in illuminated area xoy plane.

For high beam, it is oval setting its target illumination region, and oval major semiaxis is a, and semi-minor axis is b.The coordinate of illuminated area is carried out to discretization, first oval major semiaxis a and semi-minor axis b are divided into respectively to n part, a _iand b _irepresent respectively i part of major semiaxis a and i part of semi-minor axis b, wherein 0 < i≤n after decile; Then centered by illuminated area central point, respectively with a _ifor major semiaxis, b _idraw ellipse for semi-minor axis, field of illumination is divided into n part vesica piscis region.Again angle α (0≤α≤360 °) is divided into m part, α _jj part of α after expression decile.On illuminated area, taking an o as end points, with the angle of x axle be α _jbeam every a vesica piscis region is subdivided into m part again.Like this, target illumination region is divided into m × n sub-box, and the energy in each sub-box is:

$E_Q=E\&CenterDot;k_i\&CenterDot;{\&Integral;}_{{\mathrm{\&alpha;}}_{j-1}}^{{\mathrm{\&alpha;}}_j}\frac{1}{2}\&CenterDot;(\frac{{a_i}^2\&CenterDot;{b_i}^2}{{\cos }^2\mathrm{\&alpha;}\&CenterDot;{b_i}^2+{\sin }^2\mathrm{\&alpha;}\&CenterDot;{{\mathrm{\&alpha;}}_i}^2}-\frac{{{\mathrm{\&alpha;}}_{i-1}}^2\&CenterDot;{b_{i-1}}^2}{{\cos }^2\mathrm{\&alpha;}\&CenterDot;{b_{i-1}}^2+{\sin }^2\mathrm{\&alpha;}\&CenterDot;{a_{i-1}}^2})\mathrm{d\&alpha;}$

In formula, Ek _irepresent brightness value, according to GB GB25991-2010 requirement, therefore constant E is set for default brightness value, in conjunction with variable k _ibe used for controlling the brightness value size of appointed area on illuminated area, in order to form predetermined Illumination Distribution, wherein, 0≤k (i)≤1.K _ivalue size need set according to illumination requirement on illuminated area, as for brightest area k _ispan be 0.9-1, for fringe region k _ispan be 0-0.1.

Endless belt corresponding to target illumination region is divided, and the light source solid angle that participates in reflection is carried out to discretization (angle in this example be set to θ 0 °≤θ≤360 °), angle be divided into n part, represent i part, with a _iand b _icorresponding; Angle θ is divided into m part, θ _jrepresent j part of θ, θ _jwith α _jcorresponding.Before reflection, the luminous flux of every a angle inner light source is:

So, do not consider the energy loss of light in the time of scioptics and in communication process, have according to the conservation of energy:

E _Q＝E _t

Combine above-mentioned various, thereby can solve obtain corresponding and θ _j.

Obtained the normal vector of putting on described curved surface by the law of refraction, utilize this normal vector to try to achieve tangent line, by asking the intersection point of tangent line and incident ray to obtain the coordinate of putting on curve, the vector form of the law of refraction can be expressed as:

${[1+n^2-2\&CenterDot;n\&CenterDot;(\stackrel{\&RightArrow;}{\mathrm{Out}}\&CenterDot;\stackrel{\&RightArrow;}{\mathrm{In}})]}^{\frac{1}{2}}\&CenterDot;\stackrel{\&RightArrow;}{N}=\stackrel{\&RightArrow;}{\mathrm{Out}}-n\&CenterDot;\stackrel{\&RightArrow;}{\mathrm{In}}$

Wherein, for incident ray unit vector, for emergent ray unit vector, for unit normal vector, n is the index of refraction in lens.In calculating, what first need to determine is the calculating initial point of lens, determining of initial point is as follows: first establish initial point value is 0 °, then sets the distance of lens bottom circular flat and LED light source light-emitting area, determines the position of the lens plane of incidence, then chooses suitable lens thickness according to this distance again.The value (if angle θ is 0 °) of fixed angles theta, by changing angle value (angle be increased to 60 ° by 0 °), can be calculated a free curve on free form surface exit facet by the initial value of determining above; By fixing respectively the value (0 °≤θ≤360 °) of different angle θ, and change angle value (angle be increased to 60 ° by 0 °), just can calculate respectively a series of free curves on free form surface exit facet.Finally formed the free form surface exit facet of lens by these free curves.

The discrete point coordinate obtaining is imported to mechanical modeling software, can obtain the free form surface of lens exit facet by setting-out matching.On the basis of free form surface exit facet, add the circular flat plane of incidence of lens bottom and the face of cylinder of lens side, do suitable processing in face and the junction of face and be connected accordingly, make all faces be combined into a closed entity, can be processed into the physical model of lens, finally obtain the optical lens with free curved surface of LED dazzle light.

Optical lens with free curved surface is fixed on the hole of lens carrier by bonding mode.Owing to there is distance between lens and LED light source, so just have part light and do not lose through lens outgoing.In order to reduce light loss of energy, a reflector is set in each hole of lens carrier, make above-mentioned part light first reflex to the lens plane of incidence through reflector, then pass through lens outgoing, thereby improve the utilization rate of the energy.

Compared with prior art, the utlity model has following advantage and technique effect: the utility model efficiency of light energy utilization is high, simple and stable structure, be convenient to assembling, cost is low, the life-span is long, luminous intensity distribution performance is good, meets the light distribution requirements of GB25991-2010.The utility model utilizes gridding method to distribute the energy of LED light source, set up the corresponding relation of coordinate in the angle of LED light source emergent ray and illumination plane, the optics of lens precision that uses the method to obtain is high, can obtain oval-shaped field of illumination, is more applicable for the far lighting of auto lamp.High beam lens exit facet in the utility model is free form surface, makes the appearance and modeling of whole auto lamp have more flexibility, meets attractive in appearanceization and the fairshaped requirement of modern car light design.

Brief description of the drawings

Fig. 1 is the 3 D stereo schematic diagram of LED dazzle light in embodiment

Fig. 2 is the structural representation of LED dazzle light in embodiment

Fig. 3 be in embodiment on illuminated area target area grid divide schematic diagram.

Fig. 4 is LED dazzle light illuminator coordinate system schematic diagram in embodiment.

Fig. 5 is the luminous intensity distribution principle schematic of LED dazzle light in embodiment.

Fig. 6 is the two-dimensional representation of optical lens with free curved surface in embodiment.

Fig. 7 is the 3 D stereo schematic diagram of optical lens with free curved surface in embodiment.

Detailed description of the invention

Below in conjunction with the drawings and specific embodiments, the utility model is described in further detail.

As depicted in figs. 1 and 2, the LED dazzle light that the utility model provides is made up of LED light source 400, optical lens with free curved surface 100, lens carrier 200 and base plate 300, LED light source and lens carrier are fixed on base plate, optical lens with free curved surface is installed on lens carrier, and the distance between LED light source light-emitting area and the optical lens with free curved surface plane of incidence is that the height of scioptics support fixes.This LED dazzle light has 400 and 4 optical lens with free curved surface 100 of 4 LED light sources, each optical lens with free curved surface is corresponding each LED light source respectively, 4 LED light sources are fixed on base plate 300 by certain position, have 4 circular holes for 4 optical lens with free curved surface are installed on lens carrier 200.In order to reduce light loss of energy, a reflector 200A is set in each hole of lens carrier 200, make not have the part light of directive optical lens with free curved surface 100 first to reflex to the optical lens with free curved surface plane of incidence through reflector, pass through again optical lens with free curved surface outgoing, thereby improve the utilization rate of the energy.

For LED dazzle light, GB 25991-2010 requires on 25m illuminated area far away, to specify that the brightness value in region is up to standard before auto lamp, and this brightness value is progressively to reduce by centre is approximate to both sides.According to light type and the Illumination Distribution of the light distribution requirements of GB, the field of illumination on illuminated area is set as to the elliptical region centered by illuminated area central point, then it is carried out to grid division, as shown in Figure 3.The luminous energy distribution in this region is what to be realized by 4 luminous stacks of LED light source, because the relative light source of spacing between 4 LED light sources is very little to the distance of illuminated area, in order to simplify calculating, can calculate luminous energy by a LED light source and distribute, adopt the multiple relation of 4 times directly to obtain total luminous energy distribution.

Then uses energy law of conservation, divides light source solid angle, and the energy in every a solid angle corresponds to the energy in every little lattice on illuminated area.Be illustrated in figure 4 auto lamp illuminator coordinate system schematic diagram, set up coordinate system taking the central point of LED light source 400 light-emitting areas as origin of coordinates O, according to spherical coordinates diagram, solid angle luminous LED light source is divided.Wherein θ is the projection of emergent ray on XOY plane and the angle of X-axis, for the angle of emergent ray and Z axis positive direction, α is any point and the some line of o and the angle of x axle in illuminated area xoy plane.

The luminous intensity distribution principle schematic of LED dazzle light as shown in Figure 5, from the light of LED light source 400 outgoing or direct directive optical lens with free curved surface 100 or reflex to optical lens with free curved surface through reflector 200A, when light process optical lens with free curved surface, reflect respectively at the circular flat plane of incidence of lens bottom and the free form surface exit facet at lens top, finally shine on illuminated area.

The light source solid angle of dividing and dividing by law of conservation of energy accordingly according to the grid in the primary condition of setting, target illumination region, use the law of refraction to obtain the normal vector on optical lens with free curved surface that incident ray acts on 100 exit facets, utilize this normal vector to try to achieve tangent line, by asking the intersection point of tangent line and incident ray to obtain the coordinate of putting on curve.Free form surface that can setting-out matching lens by these a series of points that calculate.

Free form surface shape is specifically determined as follows.

First the distance of target illumination identity distance LED is d=25m, and the total light flux of LED light source is Q, and central light strength is I ₀=Q/ π.Wherein for the angle of emergent ray and Z axis positive direction, θ is the projection of emergent ray on XOY plane and the angle of X-axis, and α is any point and the some line of o and the angle of x axle in illuminated area xoy plane.

For high beam, it is oval setting its target illumination region, and oval major semiaxis is a, and semi-minor axis is b.The coordinate of illuminated area is carried out to discretization, first oval major semiaxis a and semi-minor axis b are divided into respectively to n part, a _iand b _irepresent respectively i part of major semiaxis a and i part of semi-minor axis b, wherein 0 < i≤n after decile; Then centered by illuminated area central point, respectively with a _ifor major semiaxis, b _idraw ellipse for semi-minor axis, field of illumination is divided into n part vesica piscis region.Again angle α (0≤α≤360 °) is divided into m part, α _jj part of α after expression decile.On illuminated area, taking an o as end points, with the angle of x axle be α _jbeam every a vesica piscis region is subdivided into m part again.Like this, target illumination region is divided into m × n sub-box, and the energy in each sub-box is:

$E_Q=E\&CenterDot;k_i\&CenterDot;{\&Integral;}_{{\mathrm{\&alpha;}}_{j-1}}^{{\mathrm{\&alpha;}}_j}\frac{1}{2}\&CenterDot;(\frac{{a_i}^2\&CenterDot;{b_i}^2}{{\cos }^2\mathrm{\&alpha;}\&CenterDot;{b_i}^2+{\sin }^2\mathrm{\&alpha;}\&CenterDot;{{\mathrm{\&alpha;}}_i}^2}-\frac{{{\mathrm{\&alpha;}}_{i-1}}^2\&CenterDot;{b_{i-1}}^2}{{\cos }^2\mathrm{\&alpha;}\&CenterDot;{b_{i-1}}^2+{\sin }^2\mathrm{\&alpha;}\&CenterDot;{a_{i-1}}^2})\mathrm{d\&alpha;}$

In formula, Ek _irepresent brightness value, according to GB GB25991-2010 requirement, therefore constant E is set for default brightness value, in conjunction with variable k _ibe used for controlling the brightness value size of appointed area on illuminated area, in order to form predetermined Illumination Distribution, wherein, 0≤k (i)≤1.K _ivalue size need set according to illumination requirement on illuminated area, as for brightest area k _ispan be 0.9-1, for fringe region k _ispan be 0-0.1.

Endless belt corresponding to target illumination region is divided, and the light source solid angle that participates in reflection is carried out to discretization (angle in this example be set to θ 0 °≤θ≤360 °), angle be divided into n part, represent i part, with a _iand b _icorresponding; Angle θ is divided into m part, θ _jrepresent j part of θ, θ _jwith α _jcorresponding.Before reflection, the luminous flux of every a angle inner light source is:

So, do not consider the energy loss of light in the time of scioptics and in communication process, have according to the conservation of energy:

E _Q＝E _t

Combine above-mentioned various, thereby can solve obtain corresponding and θ _j.

Obtained the normal vector of putting on described curved surface by the law of refraction, utilize this normal vector to try to achieve tangent line, by asking the intersection point of tangent line and incident ray to obtain the coordinate of putting on curve, the vector form of the law of refraction can be expressed as:

${[1+n^2-2\&CenterDot;n\&CenterDot;(\stackrel{\&RightArrow;}{\mathrm{Out}}\&CenterDot;\stackrel{\&RightArrow;}{\mathrm{In}})]}^{\frac{1}{2}}\&CenterDot;\stackrel{\&RightArrow;}{N}=\stackrel{\&RightArrow;}{\mathrm{Out}}-n\&CenterDot;\stackrel{\&RightArrow;}{\mathrm{In}}$

Wherein, for incident ray unit vector, for emergent ray unit vector, for unit normal vector, n is the index of refraction in lens.In calculating, what first need to determine is the calculating initial point of lens, determining of initial point is as follows: first establish initial point value is 0 °, then sets the distance of lens bottom circular flat and LED light source light-emitting area, determines the position of the lens plane of incidence, then chooses suitable lens thickness according to this distance again.The value (if angle θ is 0 °) of fixed angles theta, by changing angle value (angle be increased to 60 ° by 0 °), can be calculated a free curve on free form surface exit facet by the initial value of determining above; By fixing respectively the value (0 °≤θ≤360 °) of different angle θ, and change angle value (angle be increased to 60 ° by 0 °), just can calculate respectively a series of free curves on free form surface exit facet.Finally formed the free form surface exit facet of lens by these free curves.

The discrete point coordinate obtaining is imported to mechanical modeling software, can obtain the free form surface of lens exit facet by setting-out matching.On the basis of free form surface exit facet, add the circular flat plane of incidence of lens bottom and the face of cylinder of lens side, do suitable processing in face and the junction of face and be connected accordingly, make all faces be combined into a closed entity, can be processed into the physical model of lens, finally obtain the optical lens with free curved surface of LED dazzle light.

Finally, on free form surface basis, add the circular flat plane of incidence of lens bottom and the face of cylinder of lens side, do suitable processing in the junction of face and face, make all faces be combined into a closed entity, can be processed into the physical model of lens, finally obtain the optical lens with free curved surface of LED dazzle light, as shown in Figure 6.Figure 7 shows that the 3 D stereo schematic diagram of optical lens with free curved surface.

Above LED dazzle light provided by the utility model is described in detail, this LED dazzle light efficiency of light energy utilization is high, simple and stable structure, be convenient to assembling, cost is low, the life-span is long, luminous intensity distribution performance is good, meets the light distribution requirements of GB25991-2010.In the utility model, apply various illustratons of model detailed description of the invention has been set forth, the foregoing is only the better feasible examples of implementation of the utility model.For those skilled in the art, according to thought of the present utility model, all can be improved in specific embodiments and applications part.In sum, this description should not be construed as restriction of the present utility model.

Claims (5)

1. a LED dazzle light, it is characterized in that comprising multiple LED light sources, multiple optical lens with free curved surface, lens carrier and base plate, lens carrier and multiple LED light source are fixed on base plate, and on lens carrier, have accordingly multiple holes of passing through for LED light source emergent light, each hole place on lens carrier is all provided with an optical lens with free curved surface, and the height of the distance scioptics support between LED light source light-emitting area and the optical lens with free curved surface plane of incidence fixes.

2. LED dazzle light according to claim 1, is characterized in that the number of described LED light source, optical lens with free curved surface is 4.

3. LED dazzle light according to claim 1, is characterized in that being equipped with in the each hole on lens carrier the reflector that enters the described plane of incidence after the light of the directly freedom of entry curved surface optical lens plane of incidence of LED light source outgoing is reflected.

4. LED dazzle light according to claim 1, is characterized in that described optical lens with free curved surface comprises circular plane of incidence, cylindrical side and the exit facet seamlessly transitting each other in turn, and exit facet is free form surface.

5. LED dazzle light according to claim 4, is characterized in that the shape of free form surface is determined as follows:

Set up rectangular coordinate system taking the central point of LED light source light-emitting area as origin of coordinates O, LED light-emitting area place plane is XOY plane, cross initial point and the axle vertical with XOY plane is Z axis, wherein XOZ plane is horizontal plane, with Z axis intersection point be that o and the plane that is parallel to XOY plane are illuminated area xoy plane, the some o central point that is illuminated area; Luminous energy distribution on illuminated area is what to be realized by the luminous stack of multiple LED light sources, because the relative light source of the spacing between LED light source is very little to the distance of illuminated area, can calculate luminous energy by a LED light source and distribute, adopt multiple relation directly to obtain total luminous energy and distribute; First according to dazzle light Illumination Distribution feature on illuminated area, field of illumination on illuminated area is set as to the elliptical region centered by illuminated area central point, then this elliptical region is carried out to grid division, uses energy law of conservation is divided light source solid angle again, finally use the law of refraction to obtain the free form surface of lens by numerical computations, free form surface shape is specifically determined as follows:

First the distance of target illumination identity distance LED is d, and the total light flux of LED light source is Q, and central light strength is I ₀=Q/ π; Wherein for the angle of emergent ray and Z axis positive direction, θ is the projection of emergent ray on XOY plane and the angle of X-axis, and α is any point and the some line of o and the angle of x axle on illuminated area;

For high beam, it is oval setting its target illumination region, and oval major semiaxis is a, and semi-minor axis is b; The coordinate of illuminated area is carried out to discretization, first oval major semiaxis a and semi-minor axis b are divided into respectively to n part, a _iand b _irepresent respectively i part of major semiaxis a and i part of semi-minor axis b, wherein 0 < i≤n after decile; Then centered by illuminated area central point, respectively with a _ifor major semiaxis, b _idraw ellipse for semi-minor axis, field of illumination is divided into n part vesica piscis region; Again angle α is divided into m part, 0≤α≤360 °, α _jj part of α after expression decile; On illuminated area, taking an o as end points, with the angle of X-axis be α _jbeam every a vesica piscis region is subdivided into m part again; Like this, target illumination region is divided into m × n sub-box, and the energy in each sub-box is:

$E_Q=E\&CenterDot;k_i\&CenterDot;{\&Integral;}_{{\mathrm{\&alpha;}}_{j-1}}^{{\mathrm{\&alpha;}}_j}\frac{1}{2}\&CenterDot;(\frac{{a_i}^2\&CenterDot;{b_i}^2}{{\cos }^2\mathrm{\&alpha;}\&CenterDot;{b_i}^2+{\sin }^2\mathrm{\&alpha;}\&CenterDot;{{\mathrm{\&alpha;}}_i}^2}-\frac{{{\mathrm{\&alpha;}}_{i-1}}^2\&CenterDot;{b_{i-1}}^2}{{\cos }^2\mathrm{\&alpha;}\&CenterDot;{b_{i-1}}^2+{\sin }^2\mathrm{\&alpha;}\&CenterDot;{a_{i-1}}^2})\mathrm{d\&alpha;}$

In formula, Ek _irepresent brightness value, according to GB GB25991-2010 requirement, constant E is set for default brightness value, in conjunction with variable k _ibe used for controlling the brightness value size of appointed area on illuminated area, in order to form predetermined Illumination Distribution, wherein, 0≤k (i)≤1; k _ivalue size need set according to illumination requirement on illuminated area, as for brightest area k _ispan be 0.9-1, for fringe region k _ispan be 0-0.1;

Endless belt corresponding to target illumination region is divided, and the light source solid angle that participates in reflection is carried out to discretization, angle be divided into n part, represent i part, with a _iand b _icorresponding; Angle θ is divided into m part, θ _jrepresent j part of θ, θ _jwith α _jcorresponding; Before reflection, the luminous flux of every a angle inner light source is:

Have according to the conservation of energy:

E _Q＝E _t

Combine above-mentioned variously, obtain corresponding and θ _j;

Obtained the normal vector of putting on described curved surface by the law of refraction, utilize this normal vector to try to achieve tangent line, by asking the intersection point of tangent line and incident ray to obtain the coordinate of putting on curve, the vector form of the law of refraction can be expressed as:

${[1+n^2-2\&CenterDot;n\&CenterDot;(\stackrel{\&RightArrow;}{\mathrm{Out}}\&CenterDot;\stackrel{\&RightArrow;}{\mathrm{In}})]}^{\frac{1}{2}}\&CenterDot;\stackrel{\&RightArrow;}{N}=\stackrel{\&RightArrow;}{\mathrm{Out}}-n\&CenterDot;\stackrel{\&RightArrow;}{\mathrm{In}}$

Wherein, for incident ray unit vector, for emergent ray unit vector, for unit normal vector, n is the index of refraction in lens; In above-mentioned calculating, what first need to determine is the calculating initial point of lens, determining of initial point is as follows: first establish initial point value is 0 °, then sets the distance of lens bottom circular flat and LED light source light-emitting area, determines the position of the lens plane of incidence, then chooses suitable lens thickness according to this distance again; The value of fixed angles theta, by changing angle value, calculate a free curve on free form surface exit facet by the initial value of determining above; By fixing respectively the value of different angle θ, and change angle value, just obtain a series of free curves on free form surface exit facet; Finally formed the free form surface exit facet of lens by these free curves.