CN103629614A - LED car high beam - Google Patents

Abstract

The invention discloses an LED car high beam. The LED car high beam comprises a plurality of LED light sources, a plurality of free-form surface optical lenses, a lens support and a base plate. The lens support and the LED light sources are fixed to the base plate, and a plurality of holes for emergent light of the LED light sources to pass through are correspondingly formed in the lens support. One free-form surface optical lens is arranged at each hole in the lens support, and the distance between light-emitting faces of the LED light sources and incident planes of the free-form surface optical lenses is fixed according to the height of the lens support. The LED car high beam is simple in structure, high in light energy utilization efficiency, simple and stable in structure, convenient to assemble, low in cost, long in service life, good in light distribution performance and capable of meeting GB25991-2010 light distribution requirements. According to the LED car high beam, exit planes of the lenses are free-form surfaces, so that the appearance of the whole car high beam can be more flexible and meet requirements for beautification and streamline of modern car high beam design.

Description

LED dazzle light

Technical field

The present invention 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.

Summary of the invention

The invention provides the LED high beam that automobile is used, 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 present invention adopts following technical scheme:

LED dazzle light, it comprises a plurality of LED light sources, a plurality of optical lens with free curved surface, lens carrier and base plate, lens carrier and a plurality of LED light source are fixed on base plate, and on lens carrier, have accordingly a plurality of holes of passing through for LED light source emergent light, each place, hole 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 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 circular plane of incidence, cylindrical side and the exit facet seamlessly transitting 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 present invention, the design principle of 4 optical lens with free curved surface is the same, and corresponding 1 LED light source of 1 optical lens with free curved surface of take is below told about as example.

Optical lens with free curved surface is made by 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 for connecting the face of cylinder of 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, at the circular flat plane of incidence of lens bottom and the free form surface exit facet at lens top, reflect respectively, finally shine on illuminated area.

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

The central point of LED light source light-emitting area of take is set up rectangular coordinate system 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 by the luminous stack of a plurality of LED light sources, to be realized, 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 by numerical computations, to obtain the free form surface of lens, 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 _ifor semi-minor axis, draw ellipse, 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, take 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:

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

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 _jthe j part that represents 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 when scioptics and in communication process, according to the conservation of energy, have:

E _Q＝E _t

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

By the law of refraction, obtained the normal vector of putting on described curved surface, 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 according to this distance, chooses suitable lens thickness again.The value of fixed angles theta (if angle θ is 0 °), by changing angle

value (angle

by 0 °, be increased to 60 °), by the initial value of determining above, can be calculated a free curve on free form surface exit facet; By fixing respectively the value (0 °≤θ≤360 °) of different angle θ, and change angle

value (angle

by 0 °, be increased to 60 °), just can calculate respectively a series of free curves on free form surface exit facet.Finally by these free curves, formed the free form surface exit facet of lens.

The discrete point coordinate obtaining is imported to mechanical modeling software, by setting-out matching, can obtain the free form surface of lens exit facet.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, in face and the junction of face, do suitable processing 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, with regard to having part light, through lens outgoing, do not lose so.In order to reduce light loss of energy, a reflector is set in each hole of lens carrier, make above-mentioned part light first through reflector, reflex to the lens plane of incidence, then pass through lens outgoing, thereby improve the utilization rate of the energy.

Compared with prior art, tool of the present invention has the following advantages and technique effect: the efficiency of light energy utilization of the present invention 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 present invention 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 of using 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 present invention 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.

Accompanying drawing explanation

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.

The specific embodiment

Below in conjunction with the drawings and specific embodiments, the present invention is further detailed explanation.

As depicted in figs. 1 and 2, LED dazzle light provided by the invention is comprised 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 4 LED light sources 400 and 4 optical lens with free curved surface 100, respectively corresponding each LED light source of each optical lens with free curved surface, 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 through reflector, to reflex to the optical lens with free curved surface plane of incidence, 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 to stipulate that the brightness value in region is up to standard on before auto lamp 25m illuminated area far away, and this brightness value is progressively to reduce by centre is approximate to both sides.Light type and Illumination Distribution according to the light distribution requirements of GB, be set as the elliptical region centered by illuminated area central point the field of illumination on illuminated area, then it carried out to grid division, as shown in Figure 3.The luminous energy distribution in this region is what by 4 luminous stacks of LED light source, to be realized, 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, the central point of LED light source 400 light-emitting areas of take is set up coordinate system as origin of coordinates O, according to spherical coordinates diagram, the luminous solid angle of 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, during light process optical lens with free curved surface, at the circular flat plane of incidence of lens bottom and the free form surface exit facet at lens top, reflect respectively, 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 _ifor semi-minor axis, draw ellipse, 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, take 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:

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

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 _jthe j part that represents 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 when scioptics and in communication process, according to the conservation of energy, have:

E _Q＝E _t

Combine above-mentioned various, thereby can solve obtain corresponding

and θ _j.

By the law of refraction, obtained the normal vector of putting on described curved surface, 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 according to this distance, chooses suitable lens thickness again.The value of fixed angles theta (if angle θ is 0 °), by changing angle

value (angle

by 0 °, be increased to 60 °), by the initial value of determining above, can be calculated a free curve on free form surface exit facet; By fixing respectively the value (0 °≤θ≤360 °) of different angle θ, and change angle

value (angle by 0 °, be increased to 60 °), just can calculate respectively a series of free curves on free form surface exit facet.Finally by these free curves, formed the free form surface exit facet of lens.

The discrete point coordinate obtaining is imported to mechanical modeling software, by setting-out matching, can obtain the free form surface of lens exit facet.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, in face and the junction of face, do suitable processing 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, in the junction of face and face, do suitable processing, 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 present invention 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 present invention, apply various illustratons of model the specific embodiment has been set forth, the foregoing is only the better feasible examples of implementation of the present invention.For those skilled in the art, according to thought of the present invention, all can be improved part in specific embodiments and applications.In sum, this description should not be construed as limitation of the present invention.

Claims (4)

1.LED dazzle light, it is characterized in that comprising a plurality of LED light sources, a plurality of optical lens with free curved surface, lens carrier and base plate, lens carrier and a plurality of LED light source are fixed on base plate, and on lens carrier, have accordingly a plurality of holes of passing through for LED light source emergent light, each place, hole 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 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, it 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, exit facet is free form surface, and the shape of free form surface is determined as follows:

The central point of LED light source light-emitting area of take is set up rectangular coordinate system 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 by the luminous stack of a plurality of LED light sources, to be realized, 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 by numerical computations, to obtain the free form surface of lens, 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 _ifor semi-minor axis, draw ellipse, 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, take 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:

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

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 _jthe j part that represents θ, θ _jwith α _jcorresponding; Before reflection, the luminous flux of every a angle inner light source is:

According to the conservation of energy, have:

E _Q＝E _t

Combine above-mentioned variously, obtain corresponding

and θ _j;

By the law of refraction, obtained the normal vector of putting on described curved surface, 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 according to this distance, chooses suitable lens thickness again; The value of fixed angles theta, by changing angle value, by the initial value of determining above, calculate a free curve on free form surface exit facet; 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 by these free curves, formed the free form surface exit facet of lens.

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