CN104279509A - LED (Light-emitting Diode) uniform light intensity lens - Google Patents

Abstract

The invention discloses an LED lens with uniform light intensity. The lens is symmetrical to the central axis, and the outgoing surface of the lens is a free curved surface. Take the section passing through the central axis of the lens as the reference plane, establish a coordinate system, the central axis is the Z axis, the origin is on the central axis, the LED chip is placed at the origin, and the direction passing through the origin and perpendicular to the central axis is the X axis. By setting the virtual For the target surface, establish the energy correspondence between the chip and the target surface to obtain the forming curve of the free-form surface of the lens, and rotate the forming curve around the Z-axis for a circle to obtain the shape of the free-form surface of the exit surface of the LED lens with uniform light intensity. The invention is relatively intuitionistic, easy to calculate, large in design target angle selection, and good in uniformity of light intensity, and has a good application prospect in the field of beacon lights, traffic lights and other signal indicators or indoor lighting that need to achieve uniform light intensity distribution.

Description

A LED Uniform Light Intensity Lens

technical field

The invention relates to the technical field of LED lighting, in particular to an LED uniform light intensity lens.

Background technique

Due to its high luminous efficiency, low energy consumption, long life, short response time and no pollution, LED is gradually replacing traditional light sources and becoming the most competitive new solid light source in the 21st century. The light intensity distribution of the LED chip is nearly Lambertian, which is different from the traditional light source, and the light distribution design needs to be carried out for it. With its advantages of redistribution of light energy, small size of optical system, high efficiency and controllable light pattern, free-form surface optics are widely used in the surface design of point light sources and extended light sources with uniform illuminance light distribution devices, and become LED optical systems. An effective means to achieve uniform illuminance light distribution.

It is necessary to achieve uniform light intensity distribution in signal indicators such as navigation lights and traffic lights or indoor lighting, and free-form surface optics are rarely used in this aspect. Some researchers use energy conservation to establish partial differential equations to realize the design of uniform light intensity lenses for point light sources, or use the principle of edge ray method to realize the design of uniform light intensity lenses for extended light sources. The calculations of the two methods are cumbersome and difficult to popularize.

Contents of the invention

The technical problem to be solved by the present invention is to provide an LED uniform light intensity lens and its preparation method in view of the deficiencies of the above-mentioned prior art. better.

Technical scheme of the present invention is as follows:

Disclosed is an LED uniform light intensity lens, wherein the LED uniform light intensity lens has a central axis symmetric shape, and the lens exit surface is a free-form surface.

The light emitted by the LED chip is refracted by the exit surface of the LED uniform light intensity lens to achieve equal light intensity output.

Another purpose of the present invention is to provide a method for preparing an LED uniform light intensity lens, the exit surface of the LED uniform light intensity lens is a free-form surface; the free-form surface of the lens exit surface is determined by the following method:

Take the section passing through the central axis of the LED uniform light intensity lens as the reference plane, establish a coordinate system, the central axis is the Z axis, the origin is on the central axis, the LED chip is placed at the origin, and the direction passing through the origin and perpendicular to the central axis is the X axis. Establish the energy correspondence between the chip and the target surface to obtain the forming curve of the free-form surface of the lens, and rotate the forming curve around the Z-axis for a circle to obtain the shape of the free-form surface of the exit surface of the LED lens with uniform light intensity.

The target surface is a hemispherical virtual target surface.

The forming curve of the free-form surface of the exit surface of the lens is determined by the following steps:

The light intensity distribution of the LED chip is I _θ = I _o cosθ, where I ₀ is the central light intensity, and θ is the angle between the LED outgoing light and the central axis;

1) Calculate the uniform light intensity by energy conservation:

The ray with θ=0 propagates along the Z-axis, and the angle between the intersection point of the maximum exit angle ray on the virtual target surface and the coordinate origin and the Z-axis after light distribution by the lens is The rays of θ=π/2 are refracted to At the intersection with the virtual target surface, uniform light intensity is obtained according to energy conservation:

2) Calculate the angle between the incident ray and the Z-axis angle θ and the intersection point of the outgoing ray on the virtual target surface and the origin of the coordinates and the Z-axis through the energy correspondence Corresponding relationship:

3) Recursively obtain the point coordinates on the forming curve:

Will Evenly divided into M equal parts, horizontal The angle between the intersection point of the i-th outgoing ray O _i on the virtual target surface and the origin of the coordinates and the Z axis is:

The angle between the i-th incident ray i _i and the optical axis Z-axis is obtained from formula (2):

Let the coordinates of point A _i be (x _i , z _i ), and the coordinates of point B _i be Then the unit vector of the incident ray i _i is:

${\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; in</span>}}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\sqrt{{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; z</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; z</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

The unit vector of the outgoing ray O _i is:

Then according to Snell's law, the normal vector of point A _i can be obtained:

${\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; N</span>}}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; z</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; \&CenterDot;</span>{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; in</span>}}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; out</span>}}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

n is the refractive index of the lens, then the tangent equation of point A _i is:

$\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; z</span>}}}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; x</span>}}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; z</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

And the linear equation of the incident light i _{i +1 corresponding to θ i+1} is:

z＝cot(θ _i+1 )x (7)

Simultaneous formula (6), formula (7) can get the intersection of the tangent line passing through A _i point and the incident ray i _{i +1 corresponding to θ i+1} , which is approximately A _i+1 ;

The initial ray i ₀ corresponding to θ ₀ is the ray propagating forward along the Z axis, and the initial point A ₀ (0, d) is selected as the starting point of the optical surface of the lens on its propagation path, then the above steps can be followed to obtain Get M discrete points A _i , i∈[1, M], and connect M discrete points to obtain a shaped curve.

Compared with the prior art, the present invention has the following advantages and effects: it provides a LED uniform light intensity lens and its preparation method, by adopting a hemispherical virtual target surface, an integral relational expression for the conservation of luminous flux is established, and the contour curve of the free-form surface of the lens is recursively obtained On the discrete data points, a solid model of the lens is generated. The design method is relatively intuitive, the calculation is simple, the choice of the design target angle is large, and the light intensity uniformity is good. It has a good application prospect in the field of navigation lights, traffic lights and other signal indicators or indoor lighting that require uniform light intensity distribution. .

Description of drawings

Fig. 1 is the front view of uniform light intensity lens in the embodiment;

Fig. 2 is a perspective view of the uniform light intensity lens shown in Fig. 1;

Fig. 3 is a schematic diagram of the coordinate system for solving the free-form surface of the lens with uniform light intensity in the embodiment of the present invention;

Fig. 4 is the light intensity distribution diagram in the embodiment;

detailed description

The implementation of the present invention will be further described in detail below in conjunction with the accompanying drawings.

As shown in FIG. 1 and FIG. 2 , the outgoing surface 101 of the LED uniform light intensity lens of the present invention is a free-form surface. As shown in FIG. 3 , the light emitted by the LED chip 201 is refracted by the emitting surface 101 of the LED uniform light intensity lens to achieve equal light intensity output. The free-form surface of the lens exit surface 101 is determined by the following method:

The thickness of the lens is d=5mm, the material of the lens is PC, which is a common material for primary lenses, and the refractive index is n=1.591.

The forming curve is determined by the following steps:

Let the lens exit angle Calculate the angle between the incident ray and the Z-axis angle θ and the intersection point of the outgoing ray on the virtual target surface and the origin of the coordinates and the Z-axis through the energy correspondence Corresponding relationship:

Recursively obtain the coordinates of the points on the forming curve:

Will Divided into 500 equal parts, namely The angle between the intersection point of the i-th outgoing ray O _i 203 on the virtual target surface and the origin of the coordinates and the Z axis is:

The included angle between the i-th conditional ray i _i 202 and the optical axis Z-axis is obtained from formula (2):

Let the coordinates of point A _i be (x _i , z _i ), and the coordinates of point B _i be Then the unit vector of the incident ray i _i 202 is:

${\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; in</span>}}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\sqrt{{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; z</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; z</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

The unit vector of the outgoing ray O _i 203 is:

Then according to Snell's law, the normal vector of point A _i can be obtained:

${\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; N</span>}}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; z</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; \&CenterDot;</span>{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; in</span>}}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; out</span>}}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

n is the refractive index of the lens, then the tangent line 204 equation of A _i point is:

$\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; z</span>}}}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; x</span>}}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; z</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

And the linear equation of the incident light i _i+1 205 corresponding to θ _i+1 is:

z＝cot(θ _i+1 )x (7)

Simultaneous formula (6), formula (7) can get the intersection point of the tangent line 204 of point A _i and the incident light i _i+1 205 corresponding to θ _i+1 , which is approximately A _i+1 ;

The initial ray i ₀ corresponding to θ ₀ is the ray propagating forward along the Z axis, and the initial point A ₀ (0, 5) is selected as the starting point of the optical surface of the lens on its propagation path. 1500 discrete points A _i , i∈[1, 1500] are obtained, and then the coordinates of the discrete points are imported into the 3D graphics software Solidworks, the rotation axis is selected, and the curve is rotated around the axis to obtain the free-form surface of the rear surface of the lens.

Fig. 1 and Fig. 2 are respectively the front view and the perspective view of the uniform light intensity lens obtained by the above scheme.

Figure 4 is the light intensity distribution diagram of the LED uniform light intensity lens, and it can be seen that the overall light intensity uniformity of the designed lens is relatively high.

Claims (4)

1. the even power lenses of LED, axisymmetric shape centered by the even power lenses of described LED, is characterized in that lens exit facet (101) is free form surface.

2. a preparation method for the even power lenses of LED, the even power lenses exit facet (101) of described LED is free form surface; It is characterized in that described lens exit facet (101) free form surface is determined by the following method: to cross the cross section of the even power lenses central shaft of LED for datum level, set up coordinate system, central shaft is Z axis, initial point on center shaft, LED chip (201) is placed on initial point, cross initial point and be X-axis with the direction of central axis, set up the energy corresponding relation of chip and target face, lens free form surface forming curve, forming curve to be rotated a circle to obtain LED even power lenses exit facet (101) free form surface shape around Z axis.

3. the even power lenses of LED according to claim 2, is characterized in that described target face (206) is for hemispherical virtual target face.

4. the even power lenses of LED according to claim 2, is characterized in that the forming curve of described lens exit facet (101) free form surface is determined as follows:

LED chip (201) light distribution is I _θ=I ₀cos θ, wherein I ₀centered by light intensity, θ is the angle of LED emergent ray and central shaft;

1) even light intensity is obtained by the conservation of energy:

The light of θ=0 is propagated along Z axis, and after lens luminous intensity distribution, the line of the intersection point of maximum angle of emergence light on virtual target face and the origin of coordinates with the angle of Z axis is the light refraction of θ=pi/2 arrives with the point of intersection in virtual target face, obtain even light intensity according to the conservation of energy:

2) angle of line with Z axis of intersection point on virtual target face of incident ray and Z axis angle theta and emergent ray and the origin of coordinates is obtained by energy corresponding relation corresponding relation:

3) recursion tries to achieve point coordinates on forming curve:

Will be divided into M decile, namely article i-th, emergent ray O _i(203) intersection point on virtual target face and the line of the origin of coordinates with the angle of Z axis are:

Corresponding i-th incident ray i is tried to achieve by formula (2) _i(202) with the angle of optical axis Z axis be:

If A _ipoint coordinates is (x _i, z _i), B again _ipoint coordinates is then incident ray i _i(202) unit vector is:

${\stackrel{\&RightArrow;}{\mathrm{in}}}_i=\frac{1}{\sqrt{{x_i}^2+{z_i}^2}}(x_i,z_i)---\left(3\right)$

Emergent ray O _i(203) unit vector is:

A can be obtained again according to snell law _ithe normal vector of point:

${\stackrel{\&RightArrow;}{N}}_i(N_{i\_x},N_{i\_z})=n\&CenterDot;{\stackrel{\&RightArrow;}{\mathrm{in}}}_i-{\stackrel{\&RightArrow;}{\mathrm{out}}}_i---\left(5\right)$

N is the refractive index of lens, then A _itangent line (204) equation of point is:

$\frac{1}{-\frac{N_{i\_z}}{N_{i\_x}}}=\frac{z-z_i}{x-x_i}---\left(6\right)$

θ again _i+1corresponding incident ray i _i+1(205) linear equation is:

z＝cot(θ _i+1)x (7)

Simultaneous formula (6), formula (7) can cross A _ithe tangent line (204) of point and θ _i+1corresponding incident ray i _i+1(205) intersection point, is approximately A _i+1;

θ ₀corresponding original light i ₀for the light along z-axis forward-propagating, its propagation path is selected initial point A ₀(0, d) as the starting point of lens optical surfaces, then recursion can obtain M discrete point A successively according to above-mentioned steps _i, i ∈ [1, M], connects M discrete point and obtains forming curve.