Patent Application
20080084693
A lighting system in an embodiment of the present invention will be described in detail with reference to
The LED module 12 includes a plurality of LED chips 11, an electrical wiring substrate 15 on which the LED chips 11 are mounted by predetermined intervals, a cable for supplying power to each LED chip 11 and the like. Condenser lenses 11a are incorporated integrally into the respective LED chips 11 so that optical axes of the condenser lenses 11a are in parallel to each other. The cable 16 is connected to connectors 15a disposed in the electrical wiring substrate 15. The LED chip 11 used as the semiconductor light emitting device of the present invention is made of a white power LED and for radiating heat, the base of the electrical wiring substrate 15, the housing 14 or the like is formed of aluminum having a relatively high thermal conductivity. In the embodiment, 17 pieces of the LED chips 11 are arrayed in two rows on the electrical wiring substrate 15 and mounted in a state where they are shifted by a half pitch with each other along the direction of each row. However, an array state or the like of the LED chips 11 to the electrical wiring substrate 15 can be changed as needed in accordance with a characteristic required in the lighting system.
When a special illumination effect is not intended for an object to be illuminated, it is general to use a white LED having color rendering properties close to sunlight as in the case of the embodiment. In a case where desired color rendering properties can not be obtained only with a single kind of white LED, at least two kinds of white LEDs having different color rendering properties are combined and subtraction mixing of the colors is used, whereby an illumination light adjusted to desired color rendering properties can be obtained. For example, in a case of obtaining an illumination light having a color temperature of 5600K, a white LED having a color temperature of 7200K and a white LED having a color temperature of 4800K, which are commercially available, are adopted in a ratio of 1 to 2 to obtain an illumination light having a color temperature close to about 5600K. That is, according to this method, it is not required to manufacture the white LED having a color temperature of 5600K and it is possible to effectively use commercially available white LEDs.
Since the modulation of color temperatures on the chromaticity coordinates is depicted in a curve, not linearly, a linear interpolation of the color temperatures as described above is possible in a limited region (for example, a range of 4800K to 7200K). Accordingly, in a case of using a LED having a color temperature out of this range, it is required to adjust a ratio of a LED combination based upon a color temperature curve.
The deflection lens array 13 in this embodiment located at a predetermined distance from and in proximity to the LED module 12 is a product molded of optically transparent polymethylmethacrylate (PMMA). The deflection lens array 13 includes deflection lenses 17 (plano-convex lenses in the embodiment) set in a reduced array pattern similar and corresponding to the respective LED chips 11. Each deflection lens 17 includes a flat optical surface 17a facing toward the LED chip 11, and a convex optical surface 17b facing an illumination region Z, i.e., to the top board T. An optical axis 17c of the deflection lens 17 is set in parallel to an optical axis 11b of the condenser lens 11a of the LED chip 11. The respective deflection lenses 17 are set in a reduced array pattern corresponding and similar to the LED chips 11. Therefore, an interval between the adjacent deflection lenses 17 is set to be shorter than that between the adjacent condenser lenses 11a. The optical axis 17c of the deflection lens 17 is offset to the central side of the illumination region Z from the optical axis 11b of the corresponding condenser lens 11a. An offset amount of each deflection lens 17 is set depending on a focus distance thereof or a relative position between the corresponding LED chip 11 and the illumination region Z.
In this embodiment, the flat optical surfaces 17a directed toward the LED chip 11 are all positioned on a common plane so as to be perpendicular to the optical axis 11b of the condenser lens 11a. This causes easy manufacture of a mold for injection-molding the deflection lens array 13 and further, eliminates an eclipse occurring due to the shoulder in the boundary part between the adjacent deflection lenses 17, making it possible to prevent occurrence of a dark line or a bright line in the illumination region Z. As a result, it is possible to produce a further high density mounting of the LED chips 11. And yet, the distance between the condenser lens 11a and the deflection lens array 13 is reduced to the minimum, and with this, it is possible to produce a more compact lighting system.
The function required for the deflection lens 17 is to guide a light flux emitted from the condenser lens 11a of each LED chip 11 to a single illumination region Z in a as uniform illumination distribution as possible. In other words, each deflection lens 17 is designed so that an image of an end face of the condenser lens 11a is formed in a single illumination region Z, i.e., on the surface of the top board T in an enlarged state in the embodiment. For this purpose, the offset amount of each deflection lens 17 is set based upon a relative position between the corresponding LED chip 11 and the illumination region Z. Further, for making an illumination distribution of lights in the illumination region Z be uniform, it is effective to mold the convex optical surface 17b of each deflection lens 17, together with the condenser lens 11a incorporated into the LED chip 11, to any proper aspheric surface configuration, not limited to a spherical surface.
When the optical axis 17c of the deflection lens 17 is offset toward the central side of the illumination region Z from the optical axis 11b of the corresponding condenser lens 11a, the illumination distribution of lights reaching the illumination region Z becomes uneven along the offset direction of the deflection lens 17. Additionally, the illumination at one end along the offset direction (the side of the optical axis 11b of the corresponding condenser lens 11a) relatively increases. However, the offset direction of each of the optical axes 17c of all deflection lens 17 is set to be symmetric to the center of the LED module 12 and thereby, the unevenness of the illumination distribution is all cancelled out. As a result, it is possible to maintain the illumination distribution in the illumination region Z to be substantially uniform.
Thus, since the lights from the respective LED chips 11 are all condensed in the single illumination region Z, it is possible to perform illumination with extremely high illumination to the surface of the top board T. And further, even if light emitting luminance of each LED chip 11 is uneven due to the variations in the manufacture of the respective LED chips 11, the illumination unevenness occurring in the conventional lighting system can be completely eliminated. Therefore, even the LED chips 11 wasted conventionally as defectives for reasons of lack of the luminance can be used without any problem, thereby reducing largely part costs in the semiconductor light emitting device. Further, even if one LED chip 11 has not emitted light for any reason, the illumination in the illumination region Z is simply reduced by the corresponding amount, and the illumination can continue as it is as long as a specific reason does not occur.
A plurality of spacer pins 18 are formed as projected from the region except the flat optical surface 17a on the surface (the side of the flat optical surface 17a) of the deflection lens array 13 facing the LED module 12 for maintaining a predetermined clearance between the LED module 12 and the deflection lens array 13. The clearance between the LED module 12 and the deflection lens array 13 is set in accordance with a focal distance of the deflection lens 17 and a size (expansion rate of the LED chip 11) of the illumination region Z. Since a design of the deflection lens 17 is required to change in accordance with a distance between the deflection lens array 13 and the illumination region Z (surface of the top board T) or the size of the illumination region Z, a length of the spacer pin 18 is also required to change with this modification. It is important to set the clearance between the LED module 12 and the deflection lens array 13 as designed. Accordingly, it is effective that the LED module 12 and the deflection lens array 13 are integrally assembled by any fastening means in such a manner that a relative position between the LED module 12 and the deflection lens array 13 does not become misaligned by an external force.
The housing 14 includes a body portion 14a having a cup-shaped cross section in conformity to an outline configuration of the LED module 12 and the deflection lens array 13 and a cover portion 14b fitted to an open end of the body portion 14a and connected integrally to the body portion 14a by a setscrew (not shown). The deflection lens array 13 is adapted not to fall off the housing 14 by getting both end edges in the array direction in contact with the cover portion 14b. The deflection lens array 13 may be more securely fixed inside the housing 14 by any engagement means. The body portion 14a has a hole 19 firmed therein for guiding the cable 16 outside of the housing 14. The cable 16 pulled out of the hole 19 outside of the housing 14 is connected to the power supply cable (not shown) through an on/off switch or a dimmer switch (both are not shown). The LED module 12 is arranged so that the back side of the electrical wiring substrate 15 is in contact with a bottom portion 14c of the body portion 14a, thereby efficiently radiating heat onto the housing 14. The structure of the housing 14 requires only a secure fixation of the LED module 12 and the deflection lens array 13 in a state where both are respectively positioned. Therefore, it is possible to change the structure of the housing 14 as needed in consideration of easy assembly or the like.
Accordingly, when power is supplied to the LED module 12 through the cable 16, the illumination region Z on the surface of the top board T is illuminated in a uniform luminous intensity distribution characteristic. It is possible to change the configuration of the illumination region Z into a rectangular shape or an elliptic shape as needed by changing the outline configuration of each deflection lens 17.
The above embodiment describes a reading lamp 10 where the illumination region Z is substantially perpendicular to the irradiation direction of the illumination light. The present invention may be, however, applied to a lighting system where the illumination region Z is inclined to the irradiation direction of the illumination light.
A heat radiation member 22 made of aluminum having radiator fins 22a is jointed integrally to an electrical wiring substrate 15 of the LED module 12. The heat radiation member 22 is fixed to the housing 14 through a bracket 23 disposed in an inner wall of the housing 14. In this embodiment, nine pieces of the LED chips 11 are arrayed in a grid pattern with the same pitch on the electrical wiring substrate 15. Since the illumination direction of each LED chip 11 is inclined to an optical axis 11b of a condenser lens 11a of the LED chip 11, the LED module 12 is received in an offset state in the housing 14 to prevent occurrence of an eclipse by the housing 14.
The hologram 21 in this embodiment retained inside of the body portion 14a of the housing 14 is a molding of optically transparent polymethylmethacrylate (PMMA). The hologram 21 functions to lead the light from each LED chip 11 to the same illumination region Z in an expansion state by using diffraction phenomena of light. In other words, the hologram 21 has the function substantially similar to a projection lens 24 as shown in a phantom line of
The deflection lens array as shown in the previous embodiment may be used in place of the hologram 21 in this embodiment. In this case, the optical surfaces of the respective deflection lenses directed toward the LED chip 11 can be all positioned on the common plane in such a manner as to be substantially perpendicular to the optical axis 11b of the condenser lens 11a. Alternatively, the optical axis of the deflection lens may be inclined to the central side of the illumination region Z, but in this case, it is required to set a convex optical surface of the deflection lens directed toward the illumination region Z to an aspheric surface.
In this embodiment, a filter 25 for color temperature adjustment is disposed between the LED module 12 and the hologram 21 so as to be overlapped with the hologram 21. The filter 25 functions so that only a region to which, for example, the light from any one of the LED chips 11 is led is colored in a predetermined color and the rest of it is completely transparent with no color. This allows a color temperature in the illumination region Z to be adjusted to such a minute degree that it can not be adjusted only by a combination of commercially available LED chips 11. Further, it is possible to use a filter coloring any region in a plurality of different colors as needed.
Two or more illumination regions Z maybe set.
The above-mentioned embodiment describes the reading lamp 10 incorporated into the writing desk D and the down spot light 20 mounted into the ceiling R of the building. However, the present invention is not limited to such a lighting system, but may be used as a general lighting system in place of a conventional incandescent lamp or fluorescent lamp. For example, the present invention may be applied to an arm light mounted to a tip of a movable arm having a plurality of joints. Or by using an advantage of high luminance, the present invention may be used as a stage lighting system, an outdoor type spot light mounted on the ground for illuminating a wall portion of the building out of doors or the like. Besides, by using an advantage of the LED that is long lifetime, the present invention may be used as a lighting system required to be used in a difficult place in exchange or maintenance, for example, as a foot lamp incorporated into a bed in a hotel.
When the present invention is applied to an arm light, it is required that a light deflection optical element can be replaced in accordance with a distance between the illumination region and the semiconductor light emitting device and also a clearance between the semiconductor light emitting device and the light deflection optical element can be changed.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
