KR20100109336A - Concentrating lens for led and designing method thereof - Google Patents

Abstract

PURPOSE: A concentrating lens for a LED is provided to locally illuminate a place by collecting light from a LED chip. CONSTITUTION: A non-spherical part(10) is formed in the central part of a condensing lens. A fresnel lens part(20) is formed in the outside of the non-spherical part and includes a plurality of Fresnel patterns. A light emitting surface(30) irradiates the light which is absorbed to the non-shperical part and the light passing through the fresnel lens part. The non-spherical part controls the oriented angle of the lights which are absorbed from a first virtual light emitting point.

Description

Condensing lens for LED and designing method

The present invention relates to a condensing lens for LED, and more particularly to a condensing lens for LED to focus and locally light the light emitted from the LED chip.

Light-emitting diodes (LEDs) are widely used in lighting and electronics. Due to the rapid growth of personal mobile communication devices such as cell phones and PDAs, various optical elements are contained within a single device. Recent studies have focused on expanding the application of LEDs to these devices.

In the field of projection displays, the use of effective homogeneous illumination with LEDs is increasing, with two areas of interest: light sources and optical lenses. An ideal light source provides light with a very small solid angle and good homogeneity. Resonant-cavity LEDs are ideal for this. Optical researchers and fabricators are dedicated to achieving highly homogeneous lighting patterns through optical design and manufacturing techniques. Electro-optical light sources must overcome the limitations of optical performance in order to compete with optical systems. Total internal reflection (TIR) Fresnel lenses are one of the means to achieve this.

The criterion of performance of an electro-optical system in all applications is generally defined as the concentration efficiency. Condensing efficiency is the ratio of the available flux obtained at the target to the total source flux emitted by the light source. The available flux is usually defined with respect to the orientation angle. However, the LED's light collection efficiency is considerably low, constraining the application because the LED's direct angle is typically greater than 45 microseconds. Besides, personal communication devices are only a few millimeters thick. For this reason, LEDs require special optical elements such as miniaturized Fresnel lenses to meet technical requirements.

Although Fresnel lenses have been used with LEDs in a variety of applications, they are not sufficient for use in miniature optical elements in terms of lens characteristics. Instead, aspherical lenses are commonly used to achieve the performance gains required for optical performance and miniaturization of optical elements.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a condensing lens for LEDs and a method of designing the same, which may be applied to miniature LED applications and collect locally the light emitted from the LED chip.

In order to solve the above technical problem, an LED condensing lens according to the present invention includes an aspherical surface portion formed at a central portion of the condensing lens; A Fresnel lens portion formed outside the aspherical surface portion and having a plurality of Fresnel patterns; And a light emitting surface through which light incident on the aspherical surface portion and light passing through the Fresnel lens portion are emitted, wherein the aspherical surface portion includes a first virtual light emitting point formed between the LED chip to be provided below the aspheric surface portion and the aspheric surface portion. A second virtual formed on an opposite side of the first virtual light emitting point with respect to the LED chip, wherein the at least some of the plurality of Fresnel patterns are designed to adjust a directing angle of the light emitted from the second aspherical portion And is designed to adjust a directing angle of the light emitted from the light emitting point and passing through each of the at least some Fresnel patterns.

Here, the plurality of Fresnel patterns are divided into first Fresnel patterns, second Fresnel patterns, and third Fresnel patterns in the order close to the aspherical surface portion, wherein the first Fresnel patterns are the first Fresnel patterns Designed to adjust a directing angle of light emitted from the virtual light emitting point via each of the first Fresnel patterns, and the second Fresnel patterns are radiated from the second virtual light emitting point to form the second Fresnel patterns The third Fresnel patterns are designed to adjust the directing angle of the light passing through each, wherein the third Fresnel patterns are emitted from a third light emitting point formed below the second light emitting point to direct the light through the third Fresnel patterns It is preferred to be designed to adjust the angle.

In addition, each of the Fresnel patterns is composed of an incident surface to which light is incident and a total reflection surface that totally reflects light incident on the incident surface, and an edge where the incident surface and the total reflection surface meet is preferably circular. .

In addition, the position of the first to third virtual light emitting point is preferably determined according to the position of the light emitting layer of the LED chip, the height of the encapsulant surrounding the LED chip and the refractive index of the encapsulant.

In order to solve the above technical problem, a method of designing a condensing lens for an LED according to the present invention comprises the steps of: designing an aspherical surface formed at a central portion of the condensing lens; And designing a Fresnel lens portion formed on an outer side of the aspherical surface portion and having a plurality of Fresnel patterns, and designing the aspherical surface portion, between the LED chip to be provided below the aspherical surface portion and the aspherical surface portion. In the designing of the Fresnel lens unit, and in order to adjust the directivity angle of the light emitted from the formed first virtual light emitting point incident on the aspherical surface portion, at least a portion of the plurality of Fresnel patterns, the LED chip It is characterized in that for designing to adjust the directivity of the light emitted from the second virtual light emitting point formed on the opposite side of the first virtual light emitting point via each of the at least some Fresnel patterns.

The designing of the Fresnel lens unit may include dividing the plurality of Fresnel patterns into first Fresnel patterns, second Fresnel patterns, and third Fresnel patterns in order of close proximity to the aspherical surface part. The first Fresnel patterns are designed to adjust the directivity angle of the light emitted from the first virtual light emitting point via each of the first Fresnel patterns, the second Fresnel patterns are the second virtual light emitting point Wherein the third Fresnel patterns are radiated from a third light emitting point formed below the second light emitting point to adjust the directing angle of the light passing through each of the second Fresnel patterns. It is desirable to design the angle of directivity of the light via the 3 Fresnel patterns.

The condensing lens for LEDs according to the present invention described above may condense light emitted from an LED chip and locally illuminate it, and may be applied to miniature LED applications.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and the accompanying drawings, substantially the same components are denoted by the same reference numerals, and redundant description will be omitted. In addition, in the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 is a cross-sectional view of a light collecting lens for an LED according to an embodiment of the present invention. Referring to FIG. 1, an LED condensing lens may include an aspherical surface portion 10 formed at a center portion, light incident on a Fresnel lens portion 20 formed at an outer side of the aspherical surface portion 10, and an aspherical surface portion 10. It includes an emission surface 30 through which the light passing through the Fresnel lens unit 20 is emitted to the outside.

The aspherical portion 10 is designed to adjust the resistance of the light emitted from a specific point at the bottom of the aspherical portion 10 and incident on the aspherical portion 10. For example, the light incident on the aspherical portion 10 is designed to travel parallel to the central axis z after incidence. The Fresnel lens unit 20 is composed of a plurality of Fresnel patterns 21 formed in the form of concentric circles. The Fresnel pattern 21 is sawtooth-shaped as its cross-sectional shape is shown so that the light is passed through the Fresnel pattern 21 and the directivity angle is adjusted over the incident and total reflection. For example, it is designed to progress parallel to the central axis z after incidence and total reflection. The structure and design of the aspherical portion 10 and the Fresnel pattern 21 will be described later in detail.

FIG. 2 is a view for explaining a schematic structure of a surface mount (SMT) LED that may be provided at the bottom of the aspherical surface 10 of the light collecting lens for LEDs and a simplified model to be used in the present embodiment.

The SMT LED has an LED chip 100 and an encapsulant 200 surrounding the LED chip 100 on the mounting substrate 300. The encapsulant 200 may be an insulating resin having excellent light transmittance including an epoxy or silicone, and the encapsulant 200 may include a phosphor and / or a diffusing agent.

The characteristics of the light source play a very important role in the design of the condenser lens for the LED. In particular, when the distance between the lens and the LED chip as a light source is close, it is necessary to regard the SMT LED including the encapsulant 200 and the mounting substrate 300 together with the LED chip 100 as one optical system.

Light is emitted from the light emitting layer 110 of the LED chip 100. The light emitting layer 110 may correspond to the quantum well layer of the LED chip 100. The emitted light passes through the encapsulant 200 and comes out as air. Some light is reflected by the mounting substrate 300, and since the refractive index of the encapsulant 200 is different from the air, the surface of the encapsulant 200 is emitted. Refraction occurs at. Therefore, as shown in FIG. 2, light emitted from the light emitting layer 110 of the LED chip 100 may be regarded as being emitted from different light emitting points when viewed from the outside of the LED chip 100, It may be referred to as a virtual light emitting point. The virtual light emitting point emerges from the top of the LED chip 100 and encapsulates the first virtual light emitting point F _T , which is a light emitting point of light refracted by the upper surface of the encapsulant 200, and from the side surface of the LED chip 100. The second virtual light emitting point F _ST , which is a light emitting point of light refracted by the side of the second 200, and the side surface of the encapsulant 200 after being reflected from the mounting substrate 300 after exiting from the side of the LED chip 100. The light emitting point of the light refracted by may be divided into a third virtual light emitting point F _SL . Therefore, the first virtual light emitting point F _{T is} formed on the LED chip 100, and the second virtual light emitting point F _{ST is} formed on the LED chip 100 based on the first virtual light emitting point F _T. The third virtual light emitting point F _SL is formed at the lower side of the second light emitting point F _ST .

The following equation is an equation showing the positions of the virtual light emitting points based on the physical values of the LED chip 100 and the encapsulant 200.

In the above equation, n ₁ and n ₂ are the refractive indices of the encapsulant 200 and air, respectively, and h _c is the position of the light emitting layer 110 of the LED chip 100, that is, the height from the mounting substrate 300. The height of the encapsulant 200 is shown, Φ, Θ, and α represent the angle of incidence, and a represents the radius of the encapsulant 200.

3 shows the distribution of each virtual light emitting point according to the solid angle of light emitted from the SMT LED. Here, the direction angle means an angle formed between the direction of the central axis z of the condensing lens and the direction of light travel.

In the implementation of the light emitting device, the LED chip 100 is positioned about the central axis z at the lower end of the aspherical portion 10 of the condensing lens illustrated in FIG. 1. Therefore, light emitted from the upper portion of the encapsulant 200 is incident on the aspherical portion 10, but light emitted from the side surface of the encapsulant 200 is not incident on the aspherical portion 10. Therefore, in the present exemplary embodiment, the aspherical surface portion 10 is radiated from the first light emitting point F _T formed between the LED chip 100 and the aspherical surface portion 10 and then incident to the aspherical surface portion 10. Design to run parallel.

The following equation is an example of the equation used to design an aspherical surface. Here, z ₀ (x) represents the z coordinate of any point on the aspherical surface corresponding to the distance x from the aspherical center.

Once the position of the point light source is determined, select the radius of curvature (C) of the spherical lens focusing on the position of the point light source, and determine the appropriate k, a ₂ , a ₄ , a ₆ , ... The value can be selected. Meanwhile, the design of the aspherical surface portion may be performed using Code V software, which is software for optical design.

The light reaching the Fresnel lens unit 20 corresponds to both the light coming from the top of the encapsulant 200 and the light coming from the side of the encapsulant 200. However, among the Fresnel patterns of the Fresnel lens unit 20, the Fresnel patterns close to the aspherical portion 10 only reach the light emitted from the upper portion of the encapsulant 200, and are located farther from the aspherical portion 10. Fresnel patterns reach the light coming from the side of the encapsulant 200. Furthermore, the light refracted from the side of the LED chip 100 and refracted at the side of the encapsulant 200 comes out of the side of the LED chip 100 and mounted on Fresnel patterns relatively close to the aspherical portion 10. Light that is reflected off the substrate 300 and then refracted at the side of the encapsulant 200 reaches the Fresnel patterns relatively remote from the aspheric portion 10. Therefore, in the present embodiment, the Fresnel patterns of the Fresnel lens portion 20 are divided into three sets of Fresnel patterns according to the distance from the aspherical portion 10, and the first Fresnels are arranged in order of being close to the aspherical portion 10. Patterns, second Fresnel patterns, and third Fresnel patterns will be referred to as. In addition, the first Fresnel patterns are designed to radiate from the first virtual light emitting point F _T so that the light passing through each of the first Fresnel patterns travels in parallel, and the second Fresnel patterns are arranged in the second virtual light emitting point. And a third virtual light emitting point F _SL formed from a lower portion of the second light emitting point, wherein the light emitted from F _ST and traveling through each of the second Fresnel patterns travels in parallel. The light emitted from) is designed to travel in parallel through the third Fresnel patterns.

The boundary between the aspherical portion 10 and the Fresnel lens portion 20 and the boundary of the three Fresnel patterns described above can be classified according to the angles from the respective virtual light emitting points, and this angle is an optical system model as shown in FIG. It can be determined according to. As illustrated in FIG. 4, the aspherical surface portion 10 has a point where the first virtual light emitting point FT, the second virtual light emitting point FST, and the third virtual light emitting point FSL respectively meet a specific direction angle. And a boundary between the first Fresnel pattern, the boundary of the first Fresnel pattern and the second Fresnel pattern, and the boundary of the second Fresnel pattern and the third Fresnel pattern.

FIG. 5 is a cross-sectional view of the Fresnel pattern as a view for explaining a method of designing a Fresnel pattern when a given virtual light emitting point (point light source) is given according to an embodiment of the present invention. As shown in the figure, the Fresnel pattern is composed of an incident surface where light is incident and a total reflection surface that totally reflects light incident on the incident surface, and an edge where the incident surface and the total reflection surface meet is circular. The incident surface has a circular shape centering on the point light source O and having a radius of curvature ρ.

In FIG. 5, let the position of the point light source be O, and the direction angle is α. In this case, the angle of incidence at the incidence plane is E, the angle of refraction is T, the angle formed by the tangent and the total reflection plane of the entrance plane at the incidence point is T, and the angle between the propagation direction and the total reflection plane of light reflected from the total reflection plane is C, the total reflection plane If the angle formed by the central axis direction of the lens is P and the refractive index of the lens is n, the following equation is established.

At this time, the radius of curvature p of the incident surface is obtained according to the following equation.

Here, r means the distance from the lens center of the incident surface. Therefore, from Equation 3, if the orientation angle α is specified, appropriate T, P, and E values can be calculated. If the calculated E value is substituted into Equation 4, the radius of curvature ρ is obtained.

As described above, according to one embodiment of the present invention, the position of the point light source for determining the shape of the incident surface and the total reflection surface of the Fresnel pattern according to the position of the Fresnel patterns of the Fresnel lens unit 20 Do it differently. When the point light source is the first virtual light emitting point FT, the second virtual light emitting point FST, and the third virtual light emitting point FSL shown in FIG. 2, the orientation angles Φ ', Θ' ', and α' 'Can each be expressed as the following equation.

Accordingly, T, P, and E for the first to third Fresnel patterns corresponding to each of the first to third virtual light emitting points by replacing α with Φ ', Θ' ', and α' 'in Equation 3, respectively. After calculating the value, the curvature radius ρ for the Fresnel pattern can be obtained from Equation 4 using each E value.

Then, the shape of the incident surface of the Fresnel pattern is determined according to the following equation.

Here, r and y mean coordinate points of arbitrary points on the incident surface.

6 is a view showing the shape of the aspherical portion 10 and the Fresnel lens portion 20 of the condensing lens designed according to the embodiment described above. When the shapes of the aspherical portion 10 and the Fresnel lens portion 20 are determined, the thickness of the condensing lens, that is, the distance from the center of the aspherical portion 10 to the exit surface 30 may be appropriately selected. The designed condensing lens can be processed directly using a high precision processing machine on Poly Methyl Methacrylate (PMMA) material, and the processing order is processed in the order of the exit surface 30, the aspherical portion 10, and the Fresnel lens portion 20. do.

7 shows a three-dimensional cross-sectional view of a condenser lens designed according to the embodiment described above.

According to the present invention described above, the aspherical surface portion 10 and the Fresnel lens portion 20 are designed using each virtual light emitting point as a point light source considering the SMT LED as an optical system. Therefore, the light emitted from the SMT LED can be collected more accurately in the vicinity of the SMT LED, and thus can be applied to miniature LED applications.

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

1 is a cross-sectional view of a light collecting lens for an LED according to an embodiment of the present invention.

FIG. 2 is a view for explaining a schematic structure of a surface mount (SMT) LED that may be provided at the bottom of the aspherical surface 10 of the light collecting lens for LEDs and a simplified model to be used in the present embodiment.

3 shows the distribution of each virtual light emitting point according to the solid angle of light emitted from the SMT LED.

FIG. 4 is a diagram illustrating a boundary between an aspherical surface portion 10 and a Fresnel lens portion 20 and a boundary between three Fresnel patterns according to an embodiment of the present invention.

5 is a diagram for describing a method of designing a Fresnel pattern when a virtual light emitting point (point light source) is given according to an embodiment of the present invention.

6 is a view showing the shape of the aspherical portion 10 and the Fresnel lens portion 20 of the condensing lens designed according to an embodiment of the present invention.

7 is a three-dimensional cross-sectional view of a light collecting lens designed according to one embodiment of the present invention.

Claims (7)

In the condenser lens for LED, An aspherical surface portion formed at a central portion of the condensing lens; A Fresnel lens portion formed outside the aspherical surface portion and having a plurality of Fresnel patterns; And an emission surface through which light incident on the aspherical surface portion and light passing through the Fresnel lens portion are emitted, The aspherical surface portion is designed to adjust a directing angle of the light emitted from the first virtual light emitting point formed between the LED chip to be provided below the aspherical surface portion and the aspherical surface portion incident on the aspherical surface portion, At least a portion of the plurality of Fresnel patterns is emitted from a second virtual light emitting point formed opposite to the first virtual light emitting point with respect to the LED chip of the light passing through each of the at least some Fresnel patterns Condensing lens for LED, characterized in that designed to adjust the directivity angle. The method of claim 1, The plurality of Fresnel patterns are divided into first Fresnel patterns, second Fresnel patterns, and third Fresnel patterns in order close to the aspherical surface portion, The first Fresnel patterns are designed to adjust the directivity angle of the light emitted from the first virtual light emitting point via each of the first Fresnel patterns, The second Fresnel patterns are designed to adjust the directing angle of the light emitted from the second virtual light emitting point via each of the second Fresnel patterns, And the third Fresnel patterns are designed to adjust a directing angle of the light emitted from the third light emitting point formed below the second light emitting point to pass through the third Fresnel patterns. The method of claim 1, Each of the Fresnel patterns, A light condensing lens for an LED, characterized in that the light incident surface and the total reflection surface made of the total reflection of the light incident on the incident surface. The method of claim 1, Condensing lens for the LED, characterized in that the edge where the incident surface and the total reflection surface meets a circle. The method of claim 2, The positions of the first to third virtual light emitting points are respectively determined by the position of the light emitting layer of the LED chip, the height of the encapsulant surrounding the LED chip and the refractive index of the encapsulant. In the design method of the condenser lens for LED, Designing an aspherical surface portion formed at a central portion of the condensing lens; And Forming a Fresnel lens portion formed outside the aspherical surface portion and having a plurality of Fresnel patterns; In the designing of the aspherical surface portion, the LED chip to be provided below the aspherical surface portion and the first virtual light emitting point formed between the aspherical surface portion is designed to adjust the directivity angle of the light incident on the aspherical surface portion, In the designing of the fresnel lens unit, at least a portion of the plurality of Fresnel patterns is radiated from a second virtual light emitting point formed opposite to the first virtual light emitting point with respect to the LED chip, A method of designing a condenser lens for an LED, characterized in that it is designed to adjust the directivity angle of the light via each of the Fresnel patterns. The method of claim 6, Designing the Fresnel lens unit, Dividing the plurality of Fresnel patterns into first Fresnel patterns, second Fresnel patterns, and third Fresnel patterns in an order close to the aspherical surface portion; The first Fresnel patterns are designed to adjust the directivity angle of the light emitted from the first virtual light emitting point via each of the first Fresnel patterns, The second Fresnel patterns are designed to adjust the directivity angle of the light emitted from the second virtual light emitting point via each of the second Fresnel patterns, The third Fresnel patterns are condensed lens for the LED characterized in that it is designed to adjust the directivity of the light emitted from the third light emitting point formed below the second light emitting point via the third Fresnel patterns Design method.

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