1. Field of the Invention
The present invention relates to a light source device having a light emitting element, etc., and more particularly, to a light source device suitable for a projector apparatus.
2. Description of the Related Art
In recent years, the demand has been growing for projector apparatuses using liquid crystal elements or DMD (digital micromirror device) elements in use for displaying documents in conference rooms or for displaying images for home theaters, and research and development have been widely conducted for such projector apparatuses.
Conventional light source device 90 comprises, as main components, light emitting element 91 which emits light mainly from a zx-plane of an orthogonal coordinate system defined by an x-axis, a y-axis, and a z-axis; and a parabolic reflection plane 92 for reflecting the light emitted from light emitting element 91 about a −y-direction in a y-axis direction. Illuminated object 93 such as a lens system, a display element etc. is disposed in the +y-axis direction. Emitted light from light emitting element 91 extensively spreads about the −y-axis direction, then is reflected by parabolic reflection plane 92 for transformation into collimated light having a substantially circular emission plane, which is irradiated to Illuminated object 93.
However, conventional light source device 90, since emitted light has a circular emission plane, whereas Illuminated object 93 is rectangular, fails to utilize part of the emitted light. This causes a problem of a lower light utilization efficiency. In addition, since conventional light source device 90 experiences difficulties in narrowing down the angle of emitted light, it is difficult to reduce the size of light source device 90.
It is an object of the present invention to provide a light source device etc. which achieves high light utilization efficiency (low power consumption) and a narrow light emission angle, which is simple and inexpensive, and is capable of being reduced in size.
A light source device according to the present invention includes a light source element and a device reflection plane. The light source element includes a light emitting element for emitting light mainly from a yz-plane in a three-dimensional orthogonal coordinate system defined by an x-axis, a y-axis, and a z-axis, and an element reflection plane for reflecting the light emitted from the light emitting element in the x-axis direction to head in a direction parallel with the yz-plane. The device reflection plane reflects the light emitted from the light source element in a direction parallel with the yz-plane to head in the y-axis direction.
The light emitting element emits light mainly in the x-axis direction and additionally emits light in the ±y-axis directions and ±z-axis directions based on its light distribution characteristics. The emitted light from the light emitting element in the x-axis direction is reflected by the element reflection plane to head in the direction parallel with the yz-plane. A majority of the reflected light is again reflected by the device reflection plane in the +y-axis direction, while the rest of the reflected light is directly headed in the +y-axis direction. Since the emitted light from the light emitting element is utilized in such an effective way, the light source device provides high light utilization efficiency. Furthermore, since a majority of emitted light from the light source element travels in parallel with the yz-plane, a narrow emission light angle can be achieved in the z-axis direction. This permits the width of the device reflection plane to be narrower in the z-axis direction, thus accomplishing a reduction in size of the light source device.
According to another embodiment, the device reflection plane may have a concave shape in the yz-plane and in planes parallel with the yz-plane. said device reflection plane has a concave shape in an xy-plane of the three-dimensional orthogonal coordinate system and in planes parallel with the xy-plane. The device reflection plane also may have a pair of end surfaces in the z-axis direction formed to be plane parallel with the xy-plane; and the device reflection plane may have a pair of end surfaces in the x-axis direction formed to be plane parallel with the yz-plane. A larger amount of emitted light from the light source element in the direction parallel with the yz-plane is reflected in the y-axis direction. The concave shape may be a parabolic shape. The parabolic shape means a parabola or a shape similar to a parabola.
According to another aspect of the present invention, an projector apparatus comprises the light source devices according to the invention each for emitting red, green, and blue light, display means for displaying an image for each of a red component, a green component, and a blue component, and projection means for projecting the image on a screen by irradiating said display means with light in the same color as the image of the color component which is displayed on said display means, wherein the light is emitted from the associated light source device.
According to yet another aspect of the present invention, an illuminator includes the light source device according to the present invention for emitting red, green, and blue light, or white light.
According to still yet another aspect of the present invention, a liquid crystal display comprises a transmission type liquid crystal display panel and a back light disposed on a back of said liquid crystal display panel, said back light including the illuminator according to the present invention.
According to the light source device of the present invention, the light emitted from the light emitting element in the x-axis direction is reflected to head in a direction parallel with the yz-plane by the element reflection plane, then the reflected light is further reflected in the y-axis direction by the device reflection plane. Since emitted light from the light emitting element can be effectively utilized in such a manner, high light utilization efficiency can be achieved. A majority of emitted light from the light source element travels parallel with the yz-plane, a narrow emission light angle can be accomplished in the z-axis direction. Consequently, the width of device reflection plane can be narrowed down in the z-axis direction, and the light source device can also be reduced in size.
In other words, the present invention can provide a light source device which exhibits high light utilization efficiency (low power consumption) and a narrow emission light angle, which is simple and inexpensive, and can be reduced in size, as well as a projector apparatus, an illuminator, and a liquid crystal display which include the light source device and accomplish low power consumption, low cost, and bright images.
The above and other objects, features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings which illustrate examples of the present invention.
First, description will be made on the general outlines of a light source device etc. according to the present invention.
In the following description, assume that a light emitting element mainly emits light in the yz-plane, and the x-axis is perpendicular to the main emission plane. The light source device of the present invention is featured in that it comprises a light source element having an element reflection plane for reflecting light emitted from a light emitting element in the x-axis direction to head in a direction parallel with a yz-plane; a device reflection plane for reflecting light emitted from the light source element in the direction parallel with the yz-plane to head in a predetermined direction within the yz-plane (this predetermined direction is a y-direction); and a lens disposed in the y-axis direction. The main emission plane of the light emitting element means a plane through which the largest amount of light is emitted. A lens is disposed in the y-axis direction in order to further narrow down an emission angle distribution of the light emitted from the light source device.
The device reflection plane has a cross-section in a parabolic shape or a shape similar to a parabola in the yz-plane. The cross section of the device reflection plane in the planes parallel with the yz-plane may be the same as the cross section in the yz-plane. This arrangement makes it possible that the emission angle distribution on the yz-plane for the emitted light from the light source device is narrowed down, and the emitted light from the light source device is transformed into a rectangular shape. The both of cross sections of the device reflection plane in the yz-plane and in the xy-plane may be in parabolic shapes or shapes similar to a parabola, and the device reflection plane may be provided with end faces parallel with the yz-plane and end faces parallel with xy-plane. This arrangement makes it possible that the emission angle distribution of the emitted light from the light source device on the yz-plane and xy-plane is narrowed down, and the light from the light source device is emitted in a shape closer to a rectangular shape.
The lens disposed in the y-direction is preferably a cylindrical lens.
The emitted light from the light source element may be any one or any combination of red, green and blue light. Alternatively, the emitted light from the light source element may be white light. The light source element is preferably a light emitting diode (LED) because of its ease of handling, lower power consumption, low price etc.
The foregoing light source device may be used as a single light source unit, and a plurality of the light source units may be arranged side by side to be combined into another light source device. The plurality of light source units arranged side by side may share a lens to reduce the number of parts and the number of assembling steps. The plurality of light source units arranged side by side may emit light in the same color or emit light in different colors from one another.
With the use of the foregoing light source device, a projector apparatus can be provided which features lower power consumption, low cost, and bright images. A color image can be displayed by lighting the light source device sequentially in the three primary colors, i.e., red, green, blue, and displaying images of a red component, a green component, and a blue component on the display element in time series synchronized with the lighting of the light source device. A color image can also be displayed by dividing the display element in the projector apparatus into a plurality of areas and displaying images of a red component, a green component, and a blue component in the respective areas in time series, while irradiating the respective areas with red, green, and blue light, respectively, synchronized with displayed colors in the respective areas of the display element.
A low power consumption, inexpensive and bright illuminator can be provided by introducing emitted light from the light source device into a light guide plate, and generating planar light emitted from the light guide plate. Emitted light from the light source may be in three colors, i.e., red, green, blue, or in white.
A low power consumption, inexpensive, and bright liquid crystal display can be provided by disposing a liquid crystal display element on the emission plane of the illuminator. A color image can be displayed by lighting the illuminator in the three primary colors, i.e., red, green, and blue in sequence, while displaying images of a red component, a green component, and a blue component on the liquid crystal display element in time series synchronized with the lighting of the illuminator. A color image can also be displayed by dividing the liquid crystal display element into a plurality of areas and displaying images of a red component, a green component, and a blue component in the respective areas in time series, while irradiating the respective areas with red, green, and blue light, respectively, synchronized with displayed colors in the respective areas of the liquid crystal display element.
The light source device of the present invention can be used as a light source for a projector apparatus in combination with an integrator illumination system, a projection lens, etc. Since the light source device of the present invention has high light utilization efficiency (low power consumption) and a narrow light emission angle, is simple and inexpensive, a projector apparatus can be provided which is inexpensive and presents bright images with lower power consumption.
A low power consumption, inexpensive, and bright illuminator can be implemented by introducing emitted light from the light source device of the present invention into a light guide plate, and forming a prism or printing a reflection pattern on a plane opposite to an emission plane to generate planar light emitted from the light guide plate. A low power consumption, inexpensive, and bright liquid crystal display can be provided by disposing a liquid crystal display element on the emission plane of the illuminator.
Next, description will be made on some embodiments of the light source device and associated apparatuses which incorporate the light source device according to the present invention.
Light source device 10 according to the embodiment comprises light source element 13 and device reflection plane 14. Light source element 13 comprises light emitting element 11 which emits light mainly from the yz-plane of the three-dimensional orthogonal coordinate system defined by the x-axis, y-axis, and z-axis; and element reflection plane 12 which reflects light emitted from light emitting element 11 in the x-axis direction in directions parallel with the yz-plane. Device reflection plane 14 reflects light emitted from light source element 13 in directions parallel with the yz-plane to head in the +y-axis direction.
Light emitting element 11 may be LED which is encapsulated in jacket 16 made of resin. A plurality of light emitting elements 11 different in light emission wavelength from one another may be provided in light source element 13 to emit light in a plurality of colors with single light source element 13. For example, a plurality of LED chips different in light emission wavelength may be encapsulated in single jacket 16. EL (Electroluminescent) lamp or the like may be used instead of LED.
Element reflection plane 12 is conical in shape, and is fixed to jacket 16 (
Next, description will be made on the operation of light source device 10. Light emitting element 11 emits light mainly in the x-axis direction, and additionally emits light in ±y-axis directions and in ±z-axis directions based on its light distribution characteristic. Emitted light from light emitting element 11 in the x-axis direction is reflected by element reflection plane 12 to head in the directions parallel with the yz-plane. A majority of the reflected light is again reflected by device reflection plane 14 in the y-axis direction, while the rest of the reflected light is directly headed in the +y-axis direction. Emitted light from light emitting element 11 in the ±y-axis directions and ±z-axis directions, which light is emitted light parallel with the yz-plane, is predominantly reflected by device reflection plane 14 in the y-axis direction, and the rest is headed directly in the y-axis direction. The emitted light from light emitting element 11 is utilized in such an effective way, and the light source device 10 provides high light utilization efficiency. Furthermore, since a majority of emitted light from the light source element 13 travels in parallel with the yz-plane, a narrow emission light angle can be achieved in the z-axis direction. This permits the width of the device reflection plane 14 to be narrower in the z-axis direction, thus accomplishing a reduction in size of the light source device 10. It should be noted that in conventional light source device 90 illustrated in
The operation of light source device 10 will be again described from another point of view. First described is light source element 13. Assume that a main emission plane of light emitting element 11, i.e., the plane from which the largest amount of light is emitted, is the yz-plane, and a direction perpendicular to this main emission plane is a x-axis. Light source element 13 has element reflection plane 12 disposed in the x-axis direction of light emitting element 11. Light emitted from light emitting element 11 in the x-axis direction is reflected by element reflection plane 12, and headed in the directions parallel with the yz-plane. In other words, light source element 13 emits substantially whole light from light emitting element 11 in the directions parallel with the yz-plane.
Device reflection plane 14 surrounds light source element 13, and reflects light from light source element 13 in a predetermined direction (+y-axis direction). Lens 15 disposed in the y-axis direction converges light reflected by device reflection plane 14 and light from light source element 13 to narrow down an emission angle distribution of the emitted light from light source device 10.
Device reflection plane 14 is designed to have a cross section in the yz-plane in a parabolic shape or a shape similar to a parabola to narrow down the emission angle distribution of emitted light from light source device 10 on the yz-plane, and to have cross sections on planes parallel with the yz-plane identical to that on the yz-plane to emit light from light source device 10 in a rectangular shape on emission plane 17, as illustrated in
The second embodiment is featured in that element reflection plane 12a is made only of plastic. As illustrated, light from a light emitting element (not shown) is reflected due to the difference in refractive index between the plastic and air on the interface therebetween. Since element reflection plane 12a can be molded integrally with jacket 16 of the light emitting element, the light source device of the second embodiment can be advantageously manufactured at a lower cost because of a reduction in the number of parts and the number of assembling steps. The light utilization efficiency can be further increased by forming a groove structure and/or a prism structure on element reflection plane 12a. Instead of plastic, glass or the like may be used.
The third embodiment is featured by the structure of element reflection plane 12b. Element reflection plane 12b has a larger angle θ formed by its tangential line and the x-axis at positions further away from light emitting element 11. Specifically, assuming the x-axis is on the center of the main emission plane of light emitting element 11, the tangential line of element reflection plane 12b has an angle θ in a range of 30 to 55° to the x-axis near the x-axis, the angle θ increasing as the position is further away from the x-axis, and has an angle θ in a range of 45 to 70° at its end portion. This structure enables element reflection plane 12b to further narrow down the light emission angle distribution from light source element 13b.
Light source device 10c of the third embodiment is featured by the structure of device reflection plane 14c. First, light source device 10c is featured by main surface 141 which has a cross section in a parabolic shape or in a shape similar to a parabola in the xy plane as well as the cross-section in the yz-plane. Second, light source device 10c is featured by end faces 142, 143 parallel with the xy-plane, and end faces 144, 145 parallel with the yz-plane. The first feature contributes to narrowing down the emission angle distribution of emitted light from light source device 10c on the xy-plane, and forming the emitted light from light source device 10c into a shape closer to a rectangular shape, together with the operation of the second feature. Either of the two features alone may be employed in light source device 10c. End faces 142, 143 may be bands of arc extending along the peripheral edges of main surface 141, although they are illustrated as large semicircles.
Description will be made on desired dimensions of device reflection plane 14c. Assume in
In the fifth embodiment, one of the light source devices according to the foregoing first to fourth embodiments is employed as light source unit 101, and a plurality of light source units 101 are arranged side by side to be combined into another light source device 10d. The plurality of light source units 101 share single elongated lens 151 to reduce the number of parts and the number of assembling steps.
Projector apparatus 20a of this embodiment employs light source device 10d (
Projector apparatus 20b of the second embodiment is a single-plate liquid crystal projector which displays images of a red component, a green component, and a blue component on single liquid crystal element 25 in time series, while sequentially turning on red light source device 21, green light source device 22, and blue light source device 23 synchronized with displayed images. Projector 20b also provides similar advantages to those of projector apparatus 20a in
Projector apparatus 30 of the third embodiment comprises red light source device 31, green light source device 32, and blue light source device 33, like projector apparatus 20b in
Projector apparatus 40 of the fourth embodiment comprises three-color light source device 41. Three-color light source device 41 has a plurality of light source units 101 (
Illuminator 50 of this embodiment has a plurality of white light source devices 51 and light guide plate 52. Emission planes of a plurality of white light source devices 51 face incident planes of light guide plate 52 to surround light guide plate 52. Each of white light source devices 51 may be, for example, light source device 10 (
Liquid crystal display 60 according to the first embodiment comprises liquid crystal display panel 61 having a color filter, disposed over the emission plane of illuminator 50 (
Liquid crystal display 70 according to the second embodiment employs liquid crystal display panel 71 without color filter, instead of liquid crystal display panel 61, and employs red light source device 72, green light source device 73, and blue light source device 74 instead of white light source device 51. Liquid crystal display 70 displays images of a red component, a green component, and a blue component on liquid crystal display panel 71 in time series, while sequentially turning on red light source device 72, green light source device 73, and blue light source device 74 synchronized with these images.
Each of liquid crystal displays 60, 70 can accomplish lower power consumption and higher luminance by use of light source device 10 (
Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications may be made without departing from the spirit or scope of the appended claims.
Number | Date | Country | Kind |
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2004-028887 | Feb 2004 | JP | national |