CN203082793U - Free-form surface lens for projection-type light-emitting diode (LED) automobile dipped headlight - Google Patents

Abstract

The utility model provides a free-form surface lens for a projection-type light-emitting diode (LED) automobile dipped headlight. The free-form surface lens is composed of two surfaces, wherein a first surface is a circular flat surface, and a second surface is a free-form surface. According to the refraction law, a normal vector of a point on the free-form surface is obtained, a tangent plane is obtained by using the normal vector, a coordinate of the point on the free-form surface is obtained by determining the intersection point of the tangent plane and light rays which are refracted by the first surface of the lens and then are incident to the free-form surface of a next point, the next point is obtained by intersecting of a straight line of the tangent plane of a preceding point and a straight line of the normal vector of the next point, the coordinates of all the points of a curve of the free-form surface on a coordinate plane are obtained by iterating, the obtained point coordinates are fitted to form the curve and then are rotated by 360 degrees around a Z-axis, and a final lens free-form surface is obtained. By means of the free-form surface lens for the projection-type LED automobile dipped headlight, the direction and the distribution of the light rays are controlled through the free-form surface of the lens, and so that a light area can meet the requirements of light distribution and illumination of the automobile dipped headlight by a national standard.

Description

The free-form surface lens that is used for projection-type LED automobile dipped headlight

Technical field

The utility model belongs to the LED lighting technical field, is specifically related to a kind of free-form surface lens of projection-type LED automobile dipped headlight.

Background technology

Traditional headlamp light source has incandescent lamp, Halogen lamp LED and high-intensity gas discharge lamp (HID), and incandescent lamp and Halogen lamp LED are short service life, though HID is longer service life, energy consumption is very big.And led light source has long, the incomparable advantages of conventional light source such as volume is little, energy-conserving and environment-protective, the response time is short, design freedom is big of life-span, therefore become car headlamp the 4th generation light source.

Headlamp is throw light on when the night running light fixture of road ahead of automobile, and its luminous intensity distribution design is the key factor that influences automotive lighting quality and effect.In the design of car headlamp, standard GB 25991-2010 stipulates that to the luminous intensity distribution figure of car headlamp purpose is to prevent that car headlamp from disturbing the opposite to sail vehicle and cause traffic accident.Concerning dipped headlights, require to produce on before the car light 25m illuminated area far away upwards 15 ° "cut-off"line of a horizontal line and horizontal line right side.The lower beam illumination face can be divided into four zones: ZONE I (I district) satisfies the marginal illumination demand in the scope of whole road surface for to have bigger diffusion, the good substrate luminous intensity distribution of the uniformity; ZONE II, III, IV are to have that light energy is comparatively concentrated, range center luminous intensity distribution far away, satisfy this track and road surface, the right (is example with vehicle right lateral standard) lighting demand at a distance.In I, II in III and the IV district, should not have the transverse illumination that influences good visibility and changes.

Early stage LED projection-type system adopts a plurality of led light sources, each led light source all has separate optical system, it is big that this optical system takies volume, be unfavorable for heat radiation, energy loss is serious, and the aplanatic non-spherical lens of the general employing of lens, light evenly can't be dispersed, it is less that fringe region luminous energy is distributed.

The utility model content

The utility model is with non-spherical lens during as lens at traditional LED automobile dipped headlight, distribution of light and move towards control rational drawback inadequately, propose a kind of can reasonable distribution light and the free-form surface lens that is used for projection-type LED automobile dipped headlight of luminous energy, improved the efficiency of light energy utilization, increase field range, and met the light distribution requirements of automobile dipped headlight.

The utility model is achieved through the following technical solutions:

Projection-type LED automobile dipped headlight free-form surface lens is made by transparent material, and transparent material is PMMA.Free-form surface lens comprises two faces, and first is plane (plane of incidence), and second is free form surface (exit facet).The shape of this free form surface is determined by following method:

The free-form surface lens that is used for projection-type LED automobile dipped headlight is characterized in that this free-form surface lens made by transparent material, and free-form surface lens is made of two faces, i.e. the plane of incidence and exit facet, and wherein the plane of incidence is a circular flat, exit facet is a free form surface.

Further, the shape of described free form surface is determined as follows:

Second focus with the ellipsoid reflector of projection-type LED automobile dipped headlight is that the origin of coordinates is set up rectangular coordinate system, with the plane crossing initial point and be parallel to the free-form surface lens plane of incidence is XOY plane, with described free-form surface lens thickness direction (promptly perpendicular to the plane of incidence) place straight line is the Z axle, choosing a straight line of crossing initial point at XOY plane is X-axis, since this free-form surface lens be with the Z axle serve as the rotation axisymmetric, so for the terseness of describing, following calculating is chosen in the XOZ plane to be carried out;

Target illumination face and described origin of coordinates distance are H, and the target illumination face is divided into I district, II district, III district and IV district according to the national standard (GB25991-2010) of vapour automobile-used LED headlamp, all there is corresponding illumination requirement value in each zone, the III district is a glare area, its maximal illumination can not surpass 0.7lx, and the light that second focus of ellipsoid reflector is sent is according to angle θ ₁, θ ₂, θ ₃Be divided into 3 parts and project other 3 zones except that the III district on the illuminated area respectively;

Light according to the given whole illuminated area of request of national standard is distributed as P ₀, the central light strength of light source is I ₀, the light and the Z-direction angle that send from ellipsoid reflector second focus are θ ₁That part of light incide that to be radiated at from illuminated area centre distance behind the lens be r ₁The position, with the z axis angle less than θ ₁That part of light behind lens, be radiated at the position of illuminated area and illuminated area centre distance less than r ₁, with the angle θ of first's light correspondence ₁Be divided into i part, each θ ₁In radius r ₁On also be divided into i part accordingly, the corresponding like this array θ that obtained ₁(i) and array r ₁(i), the conservation of energy expression formula of the illumination on first area emergent light and the illuminated area is so:

$2\mathrm{\&pi;}{\&Integral;}_0^{{\mathrm{\&theta;}}_1\left(i\right)}{I}_0\cos \mathrm{\&theta;}\sin \mathrm{\&theta;}\&CenterDot;\mathrm{d\&theta;}=2\mathrm{\&pi;}{\&Integral;}_0^{r_1\left(i\right)}{\mathrm{<figure-callout\; id="0"\; label="P"\; filenames="130116173739.png"\; state="\{\{state\}\}">P</figure-callout>}}_0\&CenterDot;r\&CenterDot;\mathrm{dr}---\left(1\right);$

In like manner, light and the Z-direction angle that sends from ellipsoid reflector second focus is θ ₁～θ ₂Between that part of light incide that to be radiated at from illuminated area centre distance behind the lens be r ₁~ r ₂The position, this part light is divided into j part, corresponding each angle also is divided into j part, the corresponding like this array θ that obtained on radius ₂(j) and array r ₂(j), then should the zone emergent light and illuminated area on the conservation of energy expression formula of illumination be:

$2\mathrm{\&pi;}{\&Integral;}_{{\mathrm{\&theta;}}_1}^{{\mathrm{\&theta;}}_2\left(j\right)}{I}_0\cos \mathrm{\&theta;}\sin \mathrm{\&theta;}\&CenterDot;\mathrm{d\&theta;}=2\mathrm{\&pi;}{\&Integral;}_{r_1}^{r_2\left(j\right)}{\mathrm{<figure-callout\; id="0"\; label="P"\; filenames="130116173739.png"\; state="\{\{state\}\}">P</figure-callout>}}_0\&CenterDot;r\&CenterDot;\mathrm{dr}---\left(2\right);$

In like manner, light and the Z-direction angle that sends from ellipsoid reflector second focus is θ ₂～θ ₃Between that part of light incide that to be radiated at from illuminated area centre distance behind the lens be r ₂～r ₃The position, this part light is divided into k part, corresponding each angle also is divided into k part on radius, so just obtained array θ ₃(k) and array r ₃(k), can the zone emergent light and illuminated area on the conservation of energy expression formula of illumination be

$2\mathrm{\&pi;}{\&Integral;}_{{\mathrm{\&theta;}}_2}^{{\mathrm{\&theta;}}_3\left(k\right)}{I}_0\cos \mathrm{\&theta;}\sin \mathrm{\&theta;}\&CenterDot;\mathrm{d\&theta;}=2\mathrm{\&pi;}{\&Integral;}_{r_2}^{r_3\left(k\right)}{\mathrm{<figure-callout\; id="0"\; label="P"\; filenames="130116173739.png"\; state="\{\{state\}\}">P</figure-callout>}}_0\&CenterDot;r\&CenterDot;\mathrm{dr}---\left(3\right);$

By above-mentioned three expression formulas, the relational expression that obtains respectively between each zone radius and the emergent light angle is as follows:

$r_1\left(i\right)=\sqrt{\frac{I_0}{{\mathrm{<figure-callout\; id="0"\; label="P"\; filenames="130116173739.png"\; state="\{\{state\}\}">P</figure-callout>}}_0}\&CenterDot;{\sin }^2{\mathrm{\&theta;}}_1\left(i\right)}---\left(4\right)$

$r_2\left(j\right)=\sqrt{\frac{I_0}{{\mathrm{<figure-callout\; id="0"\; label="P"\; filenames="130116173739.png"\; state="\{\{state\}\}">P</figure-callout>}}_0}\&CenterDot;({\sin }^2{\mathrm{\&theta;}}_2\left(j\right)-{\sin }^2{\mathrm{\&theta;}}_1)+{r_1}^2}---\left(5\right)$

$r_3\left(k\right)=\sqrt{\frac{I_0}{{\mathrm{<figure-callout\; id="0"\; label="P"\; filenames="130116173739.png"\; state="\{\{state\}\}">P</figure-callout>}}_0}\&CenterDot;({\sin }^2{\mathrm{\&theta;}}_3\left(k\right)-{\sin }^2{\mathrm{\&theta;}}_2)+{r_2}^2}---\left(6\right);$

Draw the normal vector of putting on the described free form surface by the law of refraction, utilize this normal vector to obtain the section, by determining that section and the intersection point through inciding the light on the free form surface after first refraction of lens that descends any obtain the coordinate of putting on the free form surface, obtain down a bit with the straight line at the normal vector place of descending any is crossing by more preceding section, obtain the coordinate of the curve each point of free form surface on coordinate plane by iteration, after the point coordinates that obtains fitted to curve, promptly obtain final lens free form surface for 360 ° around the rotation of Z axle.

Be provided with the free-form surface lens plane of incidence and ellipsoid reflector second focus apart from f=10mm, then the free-form surface lens plane of incidence has according to the law of refraction:

$\frac{\sin \mathrm{\&theta;}}{\sin {\mathrm{\&theta;}}^{\&prime;}}=\frac{n^{\&prime;}}{n}---\left(7\right)$

Light incides the free form surface medium from air, and the refractive index of air is n=1, and free-form surface lens uses material PMMA to make refractive index n '=1.4935; θ is the angle (i.e. light and the Z-direction angle that sends from ellipsoid reflector second focus) of incident ray, θ ' is the angle (i.e. light and Z-direction angle through reflecting behind the free-form surface lens plane of incidence) of refracted ray, the intersecting point coordinate value of the incident ray and the free-form surface lens plane of incidence is (ftan (θ), f), and the slope value of refracted ray is cot (θ '), utilizes point slope form can obtain the equation of refracted ray;

Light reflects again when the exit facet of process free-form surface lens, and the vector form of the law of refraction is expressed as

$[1+n^2-2n(\stackrel{\&RightArrow;}{\mathrm{Out}}\&CenterDot;\stackrel{\&RightArrow;}{\mathrm{In}}){]}^{1/2}\&CenterDot;\stackrel{\&RightArrow;}{N}=\stackrel{\&RightArrow;}{\mathrm{Out}}-n\&CenterDot;\stackrel{\&RightArrow;}{\mathrm{In}}---\left(8\right),$

Wherein: n is the free form surface medium refraction index,

Be the incident ray unit vector,

Be the emergent ray unit vector,

Be the unit normal vector of free form surface at the light incidence point;

When definite free form surface shape, at first determine an initial point, this initial point operated by rotary motion on the Z axle, numerical values recited be free-form surface lens thickness h and the lens plane of incidence and ellipsoid reflector second focus apart from f with, be initial point coordinate for (0, h+f).If the intersection point A coordinate of the incident ray and the free-form surface lens plane of incidence be (x ', f), the point B coordinate that light shines on the free form surface after reflecting through the plane of incidence is (x, z), the point C coordinate that light projects on the illuminated area after reflecting through lens is (r, H), H=25m wherein, r according to law of conservation of energy by formula (4), (5), (6) decision; So can obtain incident ray

With emergent ray Unit vector, utilizes the law of refraction (formula 8) promptly to obtain the normal vector that B is ordered again, thereby determine the section of this point, thereby the more following of free form surface determined with any ray intersection through inciding on the free form surface after the plane of incidence refraction down in this section; Obtain down a bit with the straight line at the normal vector place of descending any is crossing by more preceding section, promptly obtain the coordinate of each point by the machine iteration; After the point coordinates that obtains fitted to curve, promptly obtain final lens free form surface for 360 ° around the rotation of Z axle.

The utlity model has following beneficial effect: the utility model provides a kind of lens of projection-type LED automobile dipped headlight, the free form surface of scioptics is controlled the trend and the distribution of light, makes its field of illumination meet light distribution and the illumination requirement of national standard to automobile dipped headlight.The utility model can reasonable distribution light and the free-form surface lens that is used for projection-type LED automobile dipped headlight of luminous energy, has improved the efficiency of light energy utilization, has increased field range.

Description of drawings

Fig. 1 is the light zoning figure during to illuminated area for the ray cast of coming out from ellipsoid second focus in the embodiment.

Fig. 2 is the coordinate profiles figure of lens in the embodiment.

Fig. 3 is the front view of lens in the embodiment.

Fig. 4 is the side view of lens in the embodiment.

Fig. 5 is the 3 dimensional drawing of lens in the embodiment.

Fig. 6 is the front view of projection-type dipped headlights system in the embodiment.

Fig. 7 is the side view of projection-type dipped headlights system in the embodiment.

The specific embodiment

Below in conjunction with accompanying drawing and example enforcement of the present utility model is described further, but enforcement of the present utility model is not limited thereto.

(1) determine primary condition and the target illumination zone divided, the result as shown in Figure 1.

Fig. 6, Fig. 7 are respectively the front view and the side view of projection-type LED dipped headlights system, and projection-type LED dipped headlights system comprises led light source 201, ellipsoid reflector 202, baffle plate 203 and free-form surface lens 204.According to the optical characteristics of ellipsoid reflector, led light source is placed on first focus of ellipsoid reflector in the mode vertical with optical axis; Baffle plate is placed on second focus of ellipsoid reflector, and overlaps with the focus of free-form surface lens.Because the light that light source sends can be assembled at the second focus place of ellipsoid reflector after reflection, thereby can will regard a spot light outgoing as from the light of the second focus outgoing.Second focus with the ellipsoid reflector of projection-type LED automobile dipped headlight is that the origin of coordinates is set up rectangular coordinate system, is the Z axle with described free-form surface lens thickness direction (perpendicular to first face) place straight line, is X-axis with the straight line parallel with described circular flat.

At first the distance of target illumination face and this dipped beam system is 25m, according to GB25991-2010, the target illumination zone is divided into 4 districts (I district, II district, III district, IV district), the III district is a glare area, its brightness value is no more than 0.7lx, will be divided into other 3 zones except that the III district that 3 parts project the target illumination zone respectively through the light of outgoing after the ellipsoid reflector reflection.According to the Illumination Distribution of field of illumination, the length of field of illumination is divided into 3 parts, because dipped beam requires its zone length to reach 3960mm, thereby our radius of maximum is set to r ₃=4m, first's radius is made as r ₁=500mm, the second portion radius is set to r ₂=2250mm; Because being approximately lambert's body, the optical field distribution of LED distributes, unsuitable excessive according to the size of dim head lights lamp again so the angle that can be utilized through the reflector light reflected is not 90 °, thereby we select to utilize light angle to be approximately 65 °.The light of these 65 degree is divided into 3 parts, θ ₁, θ ₂, θ ₃With 0 ~ θ ₁, θ ₁~ θ ₂, θ ₂~ θ ₃Light be divided into 100 parts, so just formed θ ₁(100), θ ₂(100), θ ₃(100) array; Then all light are projected the correspondence position of field of illumination respectively.

(2) set up through energy behind the ellipsoid reflector and the relational equation that projects the energy of illuminated area according to law of conservation of energy

If the gross energy of light source is 100lm, then given light is distributed as P ₀=3.9789lx, the central light strength of light source are I ₀=31.8310cd, the consideration direction is θ ₁The position of the illuminated area that incides of light be r ₁, with axis angle less than θ ₁The position coordinates of light incident also less than r ₁, with the light θ of first ₁Be divided into i part, corresponding each θ ₁In radius r ₁On also be divided into i part, so just obtained array θ ₁(i) and r ₁(i), the conservation of energy expression formula of the illumination on first area emergent light and the illuminated area is so:

$2\mathrm{\&pi;}{\&Integral;}_0^{{\mathrm{\&theta;}}_1\left(i\right)}{I}_0\cos \mathrm{\&theta;}\sin \mathrm{\&theta;}\&CenterDot;\mathrm{d\&theta;}=2\mathrm{\&pi;}{\&Integral;}_0^{r_1\left(i\right)}{\mathrm{<figure-callout\; id="0"\; label="P"\; filenames="130116173739.png"\; state="\{\{state\}\}">P</figure-callout>}}_0\&CenterDot;r\&CenterDot;\mathrm{dr}---\left(9\right)$

Angle is θ ₁～θ ₂Between the light position of inciding illuminated area be r ₁～r ₂, this part light is divided into j part, corresponding each angle also is divided into j part on radius, so just obtained array θ ₂(j) and r ₂(j), then should the zone emergent light and illuminated area on the conservation of energy expression formula of illumination be:

$2\mathrm{\&pi;}{\&Integral;}_{{\mathrm{\&theta;}}_1}^{{\mathrm{\&theta;}}_2\left(j\right)}{I}_0\cos \mathrm{\&theta;}\sin \mathrm{\&theta;}\&CenterDot;\mathrm{d\&theta;}=2\mathrm{\&pi;}{\&Integral;}_{r_1}^{r_2\left(j\right)}{\mathrm{<figure-callout\; id="0"\; label="P"\; filenames="130116173739.png"\; state="\{\{state\}\}">P</figure-callout>}}_0\&CenterDot;r\&CenterDot;\mathrm{dr}---\left(10\right)$

In like manner, angle is θ ₂～θ ₃Between the light position of inciding illuminated area be r ₂～r ₃, this part light is divided into k part, corresponding each angle also is divided into k part on radius, so just obtained array θ ₃(k) and r ₃(k), can the zone emergent light and illuminated area on the conservation of energy expression formula of illumination be

$2\mathrm{\&pi;}{\&Integral;}_{{\mathrm{\&theta;}}_2}^{{\mathrm{\&theta;}}_3\left(k\right)}{I}_0\cos \mathrm{\&theta;}\sin \mathrm{\&theta;}\&CenterDot;\mathrm{d\&theta;}=2\mathrm{\&pi;}{\&Integral;}_{r_2}^{r_3\left(k\right)}{\mathrm{<figure-callout\; id="0"\; label="P"\; filenames="130116173739.png"\; state="\{\{state\}\}">P</figure-callout>}}_0\&CenterDot;r\&CenterDot;\mathrm{dr}---\left(11\right)$

By these three expression formulas, the relational expression that can obtain respectively between each zone radius and the emergent light angle is as follows:

$r_1\left(i\right)=\sqrt{\frac{I_0}{{\mathrm{<figure-callout\; id="0"\; label="P"\; filenames="130116173739.png"\; state="\{\{state\}\}">P</figure-callout>}}_0}\&CenterDot;{\sin }^2{\mathrm{\&theta;}}_1\left(i\right)}---\left(12\right)$

$r_2\left(j\right)=\sqrt{\frac{I_0}{{\mathrm{<figure-callout\; id="0"\; label="P"\; filenames="130116173739.png"\; state="\{\{state\}\}">P</figure-callout>}}_0}\&CenterDot;({\sin }^2{\mathrm{\&theta;}}_2\left(j\right)-{\sin }^2{\mathrm{\&theta;}}_1)+{r_1}^2}---\left(13\right)$

$r_3\left(k\right)=\sqrt{\frac{I_0}{{\mathrm{<figure-callout\; id="0"\; label="P"\; filenames="130116173739.png"\; state="\{\{state\}\}">P</figure-callout>}}_0}\&CenterDot;({\sin }^2{\mathrm{\&theta;}}_3\left(k\right)-{\sin }^2{\mathrm{\&theta;}}_2)+{r_2}^2}---\left(14\right)$

With r ₁=500mm, r ₂=2250mm brings in above-mentioned 3 formulas, obtains r respectively ₁Sequence, r ₂Sequence, r ₃Sequence.

(3) obtain the normal vector of putting on the described curved surface by the law of refraction, utilize this normal vector to try to achieve the section, obtain the coordinate of putting on the curve by asking section and the intersection point that descends any through inciding the light on the free form surface after first refraction.

Be provided with the free-form surface lens plane of incidence and ellipsoid reflector second focus apart from f=10mm, then the free-form surface lens plane of incidence has according to the law of refraction:

$\frac{\sin \mathrm{\&theta;}}{\sin {\mathrm{\&theta;}}^{\&prime;}}=\frac{n^{\&prime;}}{n}---\left(15\right)$

Light incides the free form surface medium from air, and the refractive index of air is n=1, and free-form surface lens uses material PMMA to make refractive index n '=1.4935.If the intersection point A coordinate of the incident ray and the free-form surface lens plane of incidence be (x ', f), the point B coordinate that light shines on the free form surface after reflecting through the plane of incidence is (x, z), light through project after the lens refractions on the illuminated area some C coordinate for (r, H), A point coordinates value can be tried to achieve and is (ftan (θ), f), and the slope value of refracted ray AB is cot (θ '), utilizes point slope form can obtain the linear equation of AB.

Light reflects through second of free-form surface lens the time, and the vector form of the law of refraction can be expressed as

$[1+n^2-2n(\stackrel{\&RightArrow;}{\mathrm{Out}}\&CenterDot;\stackrel{\&RightArrow;}{\mathrm{In}}){]}^{1/2}\&CenterDot;\stackrel{\&RightArrow;}{N}=\stackrel{\&RightArrow;}{\mathrm{Out}}-n\&CenterDot;\stackrel{\&RightArrow;}{\mathrm{In}}---\left(16\right)$

Wherein: n is the free form surface medium refraction index,

Be the incident ray unit vector,

Be the emergent ray unit vector, Be the unit normal vector of free form surface at the light incidence point.

When calculating free form surface face type, at first determine the initial point (0.0215 of a calculating, 0.01), if the some B coordinate that light incides on the free form surface after through first refraction is (x, z), light through project after the lens refractions on the screen some C coordinate for (r, H), H=25m wherein, r according to law of conservation of energy by formula (12), (13), (14) decision.So, incident ray With emergent ray Unit vector all can try to achieve, utilize the law of refraction (formula 16) can obtain the normal vector that B is ordered again, thereby determine the section of this point, thereby the more following of free form surface determined with the ray intersection through inciding after first refraction on the free form surface that descends any in this section.Obtain down a bit with the straight line at the normal vector place of descending any is crossing by more preceding section, can obtain the coordinate of each point by computer iterations.Thereby determined the coordinate of each point on the free form surface.

(4) point that utilizes mechanical modeling software to obtain fits to curved surface

As Fig. 2, the point coordinates that obtains fitted to curve after, promptly obtain final lens free form surface for 360 ° around the rotation of Z axle.Fig. 3 ~ 5 are respectively free-form surface lens front view, side view, stereogram, and free-form surface lens comprises the plane of incidence 101, free form surface 102.

After adopting technique scheme, can reasonably control distribution of light and trend, make light type field range wider, spot zone is remarkable, good illumination effect.

Claims (3)

1. the free-form surface lens that is used for projection-type LED automobile dipped headlight, it is characterized in that this free-form surface lens made by transparent material, free-form surface lens is made of two faces, i.e. the plane of incidence and exit facet, wherein the plane of incidence is a circular flat, and exit facet is a free form surface.

2. the free-form surface lens that is used for projection-type LED automobile dipped headlight according to claim 1 is characterized in that, the shape of described free form surface is determined as follows:

Second focus with the ellipsoid reflector of projection-type LED automobile dipped headlight is that the origin of coordinates is set up rectangular coordinate system, with the plane crossing initial point and be parallel to the free-form surface lens plane of incidence is XOY plane, with described free-form surface lens thickness direction place straight line is the Z axle, choosing a straight line of crossing initial point at XOY plane is X-axis, since this free-form surface lens be with the Z axle serve as the rotation axisymmetric, so for the terseness of describing, following calculating is chosen in the XOZ plane to be carried out;

Target illumination face and described origin of coordinates distance are H, and the target illumination face is divided into I district, II district, III district and IV district according to the standard GB 25991-2010 of vapour automobile-used LED headlamp, all there is corresponding illumination requirement value in each zone, the III district is a glare area, its maximal illumination can not surpass 0.7lx, and the light that second focus of ellipsoid reflector is sent is according to angle θ ₁, θ ₂, θ ₃Be divided into 3 parts and project other 3 zones except that the III district on the illuminated area respectively;

Light according to the given whole illuminated area of described request of national standard is distributed as P ₀, the central light strength of light source is I ₀, the light and the Z-direction angle that send from ellipsoid reflector second focus are θ ₁That part of light incide that to be radiated at from illuminated area centre distance behind the lens be r ₁The position, with the z axis angle less than θ ₁That part of light behind lens, be radiated at the position of illuminated area and illuminated area centre distance less than r ₁, with the angle θ of first's light correspondence ₁Be divided into i part, each θ ₁In radius r ₁On also be divided into i part accordingly, the corresponding like this array θ that obtained ₁(i) and array r ₁(i), the conservation of energy expression formula of the illumination on first area emergent light and the illuminated area is so:

$2\mathrm{\&pi;}{\&Integral;}_0^{{\mathrm{\&theta;}}_1\left(i\right)}{I}_0\cos \mathrm{\&theta;}\sin \mathrm{\&theta;}\&CenterDot;\mathrm{d\&theta;}=2\mathrm{\&pi;}{\&Integral;}_0^{r_1\left(i\right)}{P}_0\&CenterDot;r\&CenterDot;\mathrm{dr}---\left(1\right);$

In like manner, light and the Z-direction angle that sends from ellipsoid reflector second focus is θ ₁～θ ₂Between that part of light incide that to be radiated at from illuminated area centre distance behind the lens be r ₁~ r ₂The position, this part light is divided into j part, corresponding each angle also is divided into j part, the corresponding like this array θ that obtained on radius ₂(j) and array r ₂(j), then should the zone emergent light and illuminated area on the conservation of energy expression formula of illumination be:

$2\mathrm{\&pi;}{\&Integral;}_{{\mathrm{\&theta;}}_1}^{{\mathrm{\&theta;}}_2\left(j\right)}{I}_0\cos \mathrm{\&theta;}\sin \mathrm{\&theta;}\&CenterDot;\mathrm{d\&theta;}=2\mathrm{\&pi;}{\&Integral;}_{r_1}^{r_2\left(j\right)}{P}_0\&CenterDot;r\&CenterDot;\mathrm{dr}---\left(2\right);$

In like manner, light and the Z-direction angle that sends from ellipsoid reflector second focus is θ ₂～θ ₃Between that part of light incide that to be radiated at from illuminated area centre distance behind the lens be r ₂～r ₃The position, this part light is divided into k part, corresponding each angle also is divided into k part on radius, so just obtained array θ ₃(k) and array r ₃(k), can the zone emergent light and illuminated area on the conservation of energy expression formula of illumination be

$2\mathrm{\&pi;}{\&Integral;}_{{\mathrm{\&theta;}}_2}^{{\mathrm{\&theta;}}_3\left(k\right)}{I}_0\cos \mathrm{\&theta;}\sin \mathrm{\&theta;}\&CenterDot;\mathrm{d\&theta;}=2\mathrm{\&pi;}{\&Integral;}_{r_2}^{r_3\left(k\right)}{P}_0\&CenterDot;r\&CenterDot;\mathrm{dr}---\left(3\right);$

By above-mentioned three expression formulas, the relational expression that obtains respectively between each zone radius and the emergent light angle is as follows:

$r_1\left(i\right)=\sqrt{\frac{I_0}{P_0}\&CenterDot;{\sin }^2{\mathrm{\&theta;}}_1\left(i\right)}---\left(4\right)$

$r_2\left(j\right)=\sqrt{\frac{I_0}{P_0}\&CenterDot;({\sin }^2{\mathrm{\&theta;}}_2\left(j\right)-{\sin }^2{\mathrm{\&theta;}}_1)+{r_1}^2}---\left(5\right)$

$r_3\left(k\right)=\sqrt{\frac{I_0}{P_0}\&CenterDot;({\sin }^2{\mathrm{\&theta;}}_3\left(k\right)-{\sin }^2{\mathrm{\&theta;}}_2)+{r_2}^2}---\left(6\right);$

Draw the normal vector of putting on the described free form surface by the law of refraction, utilize this normal vector to obtain the section, by determining that section and any intersection point through inciding the light on the free form surface after the refraction of the lens plane of incidence down obtain the coordinate of putting on the free form surface, obtain down a bit with the straight line at the normal vector place of descending any is crossing by more preceding section, obtain the coordinate of the curve each point of free form surface on coordinate plane by iteration, after the point coordinates that obtains fitted to curve, promptly obtain final lens free form surface for 360 ° around the rotation of Z axle.

3. the free-form surface lens that is used for projection-type LED automobile dipped headlight according to claim 2 is characterized in that,

Be provided with the free-form surface lens plane of incidence and ellipsoid reflector second focus apart from f=10mm, then the free-form surface lens plane of incidence has according to the law of refraction:

$\frac{\sin \mathrm{\&theta;}}{\sin {\mathrm{\&theta;}}^{\&prime;}}=\frac{n^{\&prime;}}{n}---\left(7\right)$

Light incides the free form surface medium from air, and the refractive index of air is n=1, and free-form surface lens uses material PMMA to make refractive index n '=1.4935; θ is light and the Z-direction angle that the angle of incident ray is promptly sent from ellipsoid reflector second focus, θ ' promptly passes through light and the Z-direction angle that reflects behind the free-form surface lens plane of incidence for the angle of refracted ray, the intersecting point coordinate value of the incident ray and the free-form surface lens plane of incidence is (ftan (θ), f), and the slope value of refracted ray is cot (θ '), utilizes point slope form can obtain the equation of refracted ray;

Light reflects again when the exit facet of process free-form surface lens, and the vector form of the law of refraction is expressed as

$[1+n^2-2n(\stackrel{\&RightArrow;}{\mathrm{Out}}\&CenterDot;\stackrel{\&RightArrow;}{\mathrm{In}}){]}^{1/2}\&CenterDot;\stackrel{\&RightArrow;}{N}=\stackrel{\&RightArrow;}{\mathrm{Out}}-n\&CenterDot;\stackrel{\&RightArrow;}{\mathrm{In}}---\left(8\right),$

Wherein: n is the free form surface medium refraction index,

Be the incident ray unit vector,

Be the emergent ray unit vector, Be the unit normal vector of free form surface at the light incidence point;

When definite free form surface shape, at first determine an initial point, this initial point is arranged on the Z axle, numerical values recited be free-form surface lens thickness h and the lens plane of incidence and ellipsoid reflector second focus apart from f with, be initial point coordinate for (0, h+f); If the intersection point A coordinate of the incident ray and the free-form surface lens plane of incidence be (x ', f), the point B coordinate that light shines on the free form surface after reflecting through the plane of incidence is (x, z), the point C coordinate that light projects on the illuminated area after reflecting through lens is (r, H), H=25m wherein, r according to law of conservation of energy by formula (4), (5), (6) decision; So can obtain incident ray With emergent ray

Unit vector, utilizes the law of refraction (formula 8) promptly to obtain the normal vector that B is ordered again, thereby determine the section of this point, thereby the more following of free form surface determined with any ray intersection through inciding on the free form surface after the plane of incidence refraction down in this section; Obtain down a bit with the straight line at the normal vector place of descending any is crossing by more preceding section, promptly obtain the coordinate of each point by the machine iteration; After the point coordinates that obtains fitted to curve, promptly obtain final lens free form surface for 360 ° around the rotation of Z axle.

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