KR101063269B1 - LED lighting system and optical system - Google Patents

Abstract

FIELD OF THE INVENTION The present invention relates to LED lighting devices, and more particularly to LED lighting devices that improve light directivity that can be used in projection display devices such as LCDs, LCoS or DLP. The device according to the invention comprises an LED chip installed on an LED substrate; An external parabolic mirror reflecting light emitted from the LED chip at a large angle with respect to an emission reference line to make quasi-parallel light; A coupler lens for converting light emitted at a small angle with respect to an emission reference line from the LED chip into quasi-parallel light; and a window surface for emitting light incident from the external parabolic and coupler lenses to the outside, the coupler The lens includes a parabolic surface that reflects light emitted at a greater angle with respect to the emission baseline and a focusing lens surface that transmits light emitted at a smaller angle with respect to the emission baseline.

External parabolic mirrors, focusing lens surface, coupler lens, Fresnel lens, rod lens

Description

LED lighting device and optical system {An apparatus for LED Illumination}             

Figure 1 shows the general light emission characteristics of the LED, Figure 1 (a) is the light emission form, (b) Lambert (Lambertian) radiation pattern and (b) the Batwing radiation pattern It is shown.

2A and 2B show known inventions each using LEDs as a projection optical system.

Figure 3a shows one embodiment of the LED lighting device according to the present invention.

Figure 3b shows another embodiment of the LED lighting apparatus according to the present invention.

4A to 4C show an embodiment in which the LED lighting apparatus according to the present invention is applied to the optical system, respectively, and the right side of FIG. 4A shows the angular distribution of the illumination light in the left embodiment.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode (LED) lighting device, and in particular, to improve light directivity to be used in a projection display device such as a liquid crystal display (LCD), a liquid crystal on silicon (LCoS), or a digital light processing (DLP). It relates to a LED lighting device.

In general, an LED refers to a device that generates a minority carrier injected by using a P-N junction structure of a semiconductor and then emits light by recombination of the minority carriers. The emission wavelength of the LED depends on the type of impurities added, and the emission of zinc and oxygen atoms is red (wavelength 700 nm), and the emission of nitrogen atoms is green (wavelength 550 nm). Such light emitting diodes have the advantages of small size, long life, high efficiency and high speed response compared to conventional light sources. Such LEDs can be used as displays, in particular flat panel displays. Generally, flat panel displays are divided into LCDs, which are light-receiving, and plasma display panels (PDP), field emission display (FED), electro luminescence display (ELD), and vacuum fluorescence display (VFD). It can be applied as a display device belonging to the dual emission type. LEDs used in flat panel displays are highly reliable, compact solid-state light emitting devices, low driving voltage, high speed modulation, high compatibility with semiconductor driving circuits, and other display devices in terms of color reproducibility, lifetime or efficiency. It has the advantage of being advantageous compared to. However, there are disadvantages in that the power consumption per device is large and the light emission angle is large as shown in FIG. Therefore, when using an LED, a special illumination optical device for directing the emitted light is required, and research into an appropriate illumination system for the effective use of the LED for application as a flat panel display is being actively conducted.

As a prior invention for such an LED lighting device, there is an LED lighting device such as FIG. 2A developed by Lumileds in the United States. According to the present invention, when the light emitted from the LED 10 is emitted, the light emitted from the central portion of the LED 10 is shifted from the device by changing the angle to quasi-parallel rays by the lens 11 installed at the central portion. . The light emitted outside the central portion passes through the inside of the plastic optical system and then totally reflects from the external parabolic surface 12 to likewise change the angle to quasi-parallel light, thereby leaving the illumination optical system. The invention, which operates in the above manner, has a disadvantage in that the conversion efficiency is severe for light emitted at a large angle from the center because the configuration is simple since only one injection optical component can be implemented.

Another known invention for the directivity of light is EP Publication No. 1452797 "Illumination Apparatus" registered by Cateye, Japan. As shown in FIG. 2B, the invention comprises an LED device 5, an LED chip 6, a first reflector 4 and a second reflector 2, and the light of the central portion emitted from the LED chip 6. The angle is changed to quasi-parallel light by the second reflector located therein. The large angle of the emitted light of the outer portion of the LED chip 6 which is not processed by the second reflector 2 is changed to parallel light by the first reflector 4 located outside, so that the entire LED emitting light Is a device for changing to quasi-parallel light. The invention, which operates in the above manner, increases the transmission efficiency of light having a large angle compared to the invention of Lumileds, but has a disadvantage in that it cannot reach the second reflector 2 and make the light near the center emitted into parallel light. . In addition, the prior art has a problem that the assembly and adjustment of the entire optical system is not easy when installing a separate lens system to make parallel light.

It is an object of the present invention to provide an LED lighting device having a light directivity that can be used as a projection optical system, for example a display.

Illumination apparatus according to an embodiment of the present invention includes an LED chip installed on the LED substrate; An external parabolic mirror reflecting light emitted from the LED chip at a large angle with respect to an emission reference line to make quasi-parallel light; A coupler lens for converting light emitted at a small angle with respect to an emission reference line from the LED chip into quasi-parallel light; and a window surface for emitting light incident from the external parabolic and coupler lenses to the outside, the coupler The lens may include a parabolic surface that reflects light emitted at a greater angle with respect to the emission baseline and a focusing lens surface that transmits light emitted at a smaller angle with respect to the emission baseline.

The parabolic surface may protrude toward the LED chip rather than the focusing lens surface, or the inner surface of the outer parabolic mirror on which the light of the LED chip is reflected may be a total reflection coating.

The window surface on which light is incident from the outer parabolic mirror is an antireflective coating, or the protruding inner surface of the parabolic surface upon which light is incident from the LED chip is an antireflective coating, and the parabolic surface is coated so that the incident light is totally reflected. Can be.

In the parabolic surface of the coupler lens, a parabolic surface may be formed for total reflection, or the focusing lens surface of the coupler lens may be a Fresnel lens.

According to another embodiment of the present invention, a system to which an LED lighting device is applied includes: an LED chip installed on an LED substrate; An external parabolic mirror reflecting light emitted at a large angle with respect to an emission reference line from the LED chip to transform into quasi-parallel light; A parabolic surface for reflecting a portion of light emitted from the LED chip at a small angle with respect to an emission reference line to make quasi-parallel light, and protruding more in the direction of the LED chip than the focusing lens surface to transmit the remaining portion of light emitted at the small angle. A coupler lens including a focusing lens surface and a window surface emitting light emitted from the LED to the outside of the LED lighting device; An optical lens for guiding light emitted from the window surface; and a panel for receiving using the light derived from the optical lens.

The optical lens may be a rod lens, the panel may be an LCD panel or an LCoS panel, or may further include a PBS.

The coupler lens and the optical lens may be integrally formed, or the focusing lens surface may be a Fresnel lens.                     

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings by way of example, but the presented embodiments are not intended to limit the scope of the present invention.

Figure 3a shows one embodiment of the LED lighting device according to the present invention.

As shown in Fig. 3a, the LED lighting device 3 according to the present invention is a semi-parallel light which is emitted from the central portion of the LED substrate 30, the LED chip 31 for fixing the LED chip 31. A coupler lens 33 for making a light source and an external parabolic mirror 32 for making semi-parallel light emitted while forming a large angle with respect to the central portion of the LED chip 31. The LED substrate 30 may use any known device capable of installing the LED chip 31 and the external parabolic mirror 32. And the LED chip 31 can be any LED chip already developed and to be developed later. In general, according to the development of semiconductor technology, LEDs can emit not only the three primary colors of light, red, green, and blue, but also light in the visible, infrared, and ultraviolet regions, and white light using them. ). Such LEDs are being applied in various fields such as lighting light, communication devices, and display devices. For example, in display devices, LEDs emitting 660 nm red with AlGaAs, LEDs emitting 570 nm or 555 nm with GaP, and 450 nm blue with InGaN LEDs can be used to implement flat panel display devices. Therefore, the LED chip 31 shown in FIG. 3A can be any LED chip that can be used in the above fields. Light emitted from the LED chip 31 has no directivity and is emitted in all directions. In the LED lighting device 3 according to the present invention, the light emitted at a constant angle from the central portion of the LED chip 31, for example, at an angle of 30 to 45 degrees from the reference line X of the LED chip 31 is coupled to the coupler lens ( 33), and light emitted at an angle greater than the angle can reach the outer parabola 32. The angle may be determined in consideration of the application field of the LED lighting device 3 according to the present invention, the overall size of the lighting device 3 or the light efficiency. For example, when used as a lighting device, the angle may be smaller and when used as a display device it will have to be larger. Light emitted at an angle greater than a constant angle from the baseline X of the LED chip 31 reaches the outer parabola 32. The outer parabola 32 is fixed to the LED substrate 30 and preferably the inner surface is a reflective coating. The reflective coating may be advantageously a metal thin film coating such as aluminum, silver, or the like for improving the reflection efficiency. The reflective coating may be a high-reflective coating and may be a thin film coating in which one or more metal materials are mixed and made according to methods known in the art. The outer parabolic mirror 32 is a parabolic mirror focused on the LED chip 31, and the light emitted from the LED chip 31 is emitted to the outside of the device while forming quasi-parallel light with respect to the reference line X. It is shown as a1 and a2.

The coupler lens 33 includes a parabolic surface 331, a focusing lens surface 332, and a window surface 333. Light emitted from the central portion of the LED chip 31 is transformed into quasi-parallel light while passing through the parabolic surface 331 and the focusing lens surface 332 and is emitted outside the lighting device 3. A part of the light emitted from the LED chip 31, for example, 15 to 35 degrees from the reference line X, is emitted while refracting and transmitting through the inner surface of the coupler lens 33 and then at the parabolic surface 331. Reflected and emitted to the outside of the device (3). It is advantageous in the lighting device 3 of the present invention that the inner surface of the coupler lens 33 is fully transmissive and the parabolic mirror 331 is pre-reflective. The coupler lens 33 may be a thin film coating using a dielectric material or the like for the front-transmissive or non-reflective. Non-reflective lenses using such thin coatings are known in the art and can be used in the lighting device 3 according to the invention. Light incident on the inner surface of the coupler lens 33 should be totally reflected at the parabolic surface 33. The total reflection method is a method in which the angle of incidence emitted from the LED chip 31 and refracted by the inner surface of the coupler lens 33 and incident on the parabolic surface 331 is total reflection. Another possible method is to apply total reflection by coating the parabolic mirror with a higher refractive index material. The shape of the coupler lens 33 needs to be adjusted so that only light within a critical angle range that allows total reflection from the light emitted from the LED chip 31 is incident on the inner surface of the coupler lens 33. Since the critical angle depends on the refractive index, it may vary depending on the material of the lens. It may also vary depending on whether or not the parabolic surface 331 is coated. Light incident on the parabolic surface 331 becomes quasi-parallel light and is emitted to the outside of the lighting device 3. The parabolic surface 331 has to be focused in consideration of the refractive index, and thus, when the shape of the parabolic surface 331 is formed, an angle in a predetermined angle range of the light emitted from the LED chip 31 becomes total reflection while the lighting device 3 Can be released to the outside of the. Light totally reflected at the parabolic surface 331 and emitted to the outside of the lighting device 3 is shown as b1 and b2.

As shown in FIG. 3A, light emitted from the central portion of the LED chip 31 is emitted to the outside of the device through the focusing lens surface 332. The focusing lens surface 332 forms a parabolic surface and the lens surface is an antireflective coating is similar to that described with respect to the inner surface of the coupler lens 33. Light incident on the focusing lens surface 332 is light emitted in a range of 0 to 15 degrees to the reference line X. Light incident on the focusing lens surface 332 and emitted to the outside of the lighting device 3 is shown as C in FIG. 3A.

As described above, light incident on the parabolic surface 331, the inner surface of the coupler lens 33, and the focusing lens surface 332 is vertically incident on the window surface 333 and is emitted to the outside of the lighting device 3. The inner face of the window face 333 may be a anti-reflective coating and the edge of the window face 333 is coupled with the outer parabolic 32 as shown in FIG. 3A. In addition, the window surface 333 must be perpendicular to the incident light, and as shown in FIG. 3A, the outside of the window surface 333 becomes a complete plane and excludes the window surface 333 except for the part contacting the coupler lens 33. It is also advantageous that the inner surface of) is also a complete plane.

As described above, the light emitted by the LED chip 31 is changed into quasi-parallel light through the external parabolic 32, parabolic surface 331, and focusing lens surface 332 according to the angle emitted from the reference line X, and thus the window. It penetrates the surface 333 and is emitted to the exterior of the lighting device 3. The emitted angle may be determined in consideration of the total reflection angle of the coupler lens 33, whether or not the coating and the size of the entire lighting device (3). A feature of the present invention is to use the external parabolic mirror 32, the parabolic surface 331 and the focusing lens surface 332 as described above so that the light emitted to the LED chip 31 does not directly enter the window surface 333. will be. As described above, the light efficiency of the projection optical system may be improved by minimizing the amount of light emitted to the outside. In addition, as shown in FIG. 3A, the protruded toward the LED chip 31 as compared to the parabolic surface 331 focusing lens surface 332. Protruding from the parabolic surface 331 serves to reduce the amount of light emitted from the LED chip 31 to the outside. As well as the function of reducing the length of the entire lighting device (3). In consideration of the critical angle at which total reflection may occur at the parabolic surface 331 and the shape of the coupler lens 33, the parabolic surface 331 is more advantageous as it protrudes toward the LED chip 31. However, the degree of protrusion must be determined in consideration of the light loss generated while the light is transmitted through the coupler lens 33. In general, a high degree of protrusion is advantageous for thinning the lighting device 3.

Figure 3b shows another embodiment of the lighting device according to the present invention.

Unlike the embodiment illustrated in FIG. 3A, as shown in FIG. 3B, the focusing lens surface 332 is formed of a Fresnel lens 332a. Fresnel lens 332a is to reduce the thickness of the lens by dividing the refractive surface of the lens into a number of bands to perform the refractive action of the lens in each band to implement the same performance as a general lens, and use a known one in the art Can be.

As described above, the Fresnel lens 332a is a series of concentric circles which are the constituent elements of the lens so that a short focal length can be formed. By using the Fresnel lens 332a in the lighting device according to the present invention, light loss can be reduced, and at the same time, the weight and thickness of the entire lighting device can be reduced. Even when the Fresnel lens 332a is used, the thin film coating may be made by reflection-free.

4A, 4B and 4C show an embodiment of the optical system to which the lighting apparatus according to the present invention is applied.

4A illustrates an embodiment in which the lighting device according to the present invention is applied to the LCD panel 41.

As shown in FIG. 4A, the light emitted from the LED chip 31 enters the external parabolic mirror 31, the parabolic surface 331 and the focusing lens surface 332 according to the emission angle, and changes to quasi-parallel light so that the window Emitted to face 333. The total reflection or anti-reflective coating on each side is the same as in the embodiment described with reference to FIG. 3A. And the focusing lens surface 332 may be formed of a Fresnel lens is the same as described in Figure 3b. Light emitted from the window surface 333 is incident to the rod lens 40. The rod lens 40 is a device that allows the light distribution to be homogeneous for each angle when the incident light passes through the inside and is totally reflected on the outer surface of the rod lens 40 to exit the rod lens 40. The light emitted from plane 333 is used for size conversion and light homogeneity improvement. The light guided by the rod lens 40 is incident on the LCD panel 41 to become illumination light necessary for implementing image information. The angle distribution of the illumination light guided by the rod lens 40 to the LCD panel 41 is shown on the right side of FIG. 4A. It shows that the illumination light is directed to the center. As such, the illumination device according to the present invention provides the advantage that it is possible to form a highly efficient projection optical system in which some degree of homogeneity and angular distribution are ensured.

Figure 4b shows another embodiment of a lighting device according to the present invention.

In the embodiment illustrated in FIG. 4B, unlike the embodiment described with reference to FIG. 4A, the window surface is not formed separately. Therefore, the coupler lens 33b and the rod lens 40b are integrally formed. The shape as described above may be combined with the rod lens 40b by manufacturing the coupler lens 33b having no window surface, or may be formed by lens processing the coupler shape into the required shape after manufacturing the rod lens 40b. . In view of light efficiency and ease of fabrication, it would be advantageous to manufacture the required shape through lens processing. The optical system shown in FIG. 4B works the same as described with respect to FIG. 4A except that the rod lens 40b is directly coupled to the outer parabola 32.

Similar to the embodiment described above, in the optical system shown in FIG. 4B, the coupler lens and the rod lens may be manufactured by plastic molding. However, in the optical system shown in FIG. 4B, the coupler lens 33 and the rod lens 40b are integrally processed by plastic molding, which is advantageous in weight reduction and thinning, and may also provide advantages in terms of manufacturing cost.

Figure 4c shows an embodiment of another optical system to which the illumination device according to the present invention is applied.

In the optical system shown in FIG. 4C, an LCoS 44 panel is used as the display device.

In the same manner as the embodiment shown in FIGS. 4A and 4B, the light emitted from the LED chip 31 is transformed into parallel light through the external parabolic 32 and the coupler lens 33 according to the emission angle, and thus the rod lens 40c. ) Although the coupler lens 33 and the rod lens 40c are shown separately in the embodiment shown in FIG. 4C, the coupler lens 33 and the rod lens 40c may be manufactured integrally with plastic molding and manufactured by lens processing, as shown in the embodiment of FIG. 4B. Light guided by the rod lens 40c proceeds to a polarization beam splitter (PBS) 43. In the PBS 43, generally, incident light is separated into an S wave component and a P wave component so that the P wave component passes through the PBS 43 and only the S wave component is reflected to the liquid crystal on silicon (LCoS) panel 44. Proceed. The LCoS panel 44 stores the necessary image information as a micro display in the incident light and directs it to the screen. The LCoS panel 44 also modulates the S wave to P wave as needed. As shown in FIG. 4C, the light reflected from the LCoS panel 44 is modulated by P waves to display image information on a screen (not shown) via the PBS 43. Although not shown in FIG. 4C, red / green / blue (R / G / B) may be synthesized if necessary using known devices such as X-prisms or Color Cubes. LCoS panel 44 may also be installed for each of red / green / blue. One of ordinary skill in the art would be able to add such known devices to the embodiment presented in FIG. 4C by making the necessary modifications.

Although only the LCD panel and the LCoS panel are presented as examples of other lighting devices in the present invention, it is obvious that the present invention can be applied to DLP (Digital Light Processing) by applying appropriate modifications. In addition, the lighting device according to the present invention can also be applied to a light control device such as a headlight of an automobile or an optical communication, and all such devices are included in the scope of the present invention.

The LED lighting device according to the present invention is to give an appropriate directivity to the LED light emitting light in all directions to improve the light efficiency. Due to the above advantages, the lighting apparatus according to the present invention facilitates the implementation of an optical projection system that can take advantage of color characteristics, long-life characteristics, fast start-up characteristics and ease of coupling with semiconductor devices. In addition, by applying a suitable modification to the external parabolic mirror or coupler lens of the present invention can be applied to various lighting devices such as headlights, street lights of automobiles.

The lighting apparatus according to the present invention has been described above in detail by the presented embodiments. The presented embodiments are illustrative and it will be apparent to those skilled in the art that various modifications and variations may be made to the disclosed embodiments without departing from the scope of the inventive concept. The scope of the present invention is not limited by the above modified and modified inventions, but only by the following claims.

Claims (14)

In the LED lighting device, An LED chip mounted on the LED substrate; An external parabolic mirror reflecting light emitted from the LED chip at a first angle range greater than a first reference angle with respect to a normal of the LED substrate to make quasi-parallel light; A coupler lens for converting light emitted from the LED chip into a second angle range smaller than a first reference angle with respect to the normal to quasi-parallel light; And A window surface for emitting light incident from the external parabolic lens and the coupler lens to the outside; The coupler lens includes a parabolic surface that reflects light emitted at an angle greater than a second reference angle among the second angle ranges, and a focusing lens surface that transmits light emitted at an angle smaller than the second reference angle. . The method according to claim 1, The parabolic surface protrudes toward the LED chip than the focusing lens surface. The method according to claim 1, The inner surface of the outer parabolic reflecting light of the LED chip is a total reflection coating is an LED lighting device. The method according to claim 1, The window surface to which light enters from the said external parabolic mirror is an anti-reflective coating. The method according to claim 2, The protruding inner surface of the parabolic surface into which light is incident from the LED chip is an antireflective coating, and the parabolic surface is coated so that the incident light is totally reflected. The method according to claim 1, The parabolic surface of the coupler lens is characterized in that the parabolic surface is formed so that the total reflection. The method according to any one of claims 1 to 6, An LED illuminating device, wherein the focusing lens surface of the coupler lens is a Fresnel lens. An optical system comprising an LED lighting device, An LED chip mounted on the LED substrate; An external parabolic mirror reflecting light emitted from the LED chip at a first angle range greater than a first reference angle with respect to a normal of the LED substrate to make quasi-parallel light; The light emitted from the LED chip at a second angle range smaller than a first reference angle with respect to the normal is transformed into quasi-parallel light, and reflects light emitted at an angle greater than a second reference angle of the second angle range. A coupler lens including a parabolic surface and a focusing lens surface for transmitting light emitted at an angle smaller than the second reference angle; A window surface for emitting light incident from the external parabolic mirror and the coupler lens to the outside; An optical lens for guiding light emitted from the window surface; And And a panel for receiving using light derived from the optical lens. The method according to claim 8, And the optical lens is a rod lens. The method according to claim 8, The panel being an LCD panel or an LCoS panel. The method according to claim 10, An optical system further comprising PBS. The method according to any one of claims 8 or 11, And the coupler lens and the optical lens are integrally formed. The method according to any one of claims 8 to 11, And said focusing lens surface is a Fresnel lens. The method according to claim 12, And said focusing lens surface is a Fresnel lens.

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