Illumination – Illuminated scale or dial – Edge illuminated modifier or light rod/pipe
Reexamination Certificate
2003-01-14
2004-11-23
Sember, Thomas M. (Department: 2875)
Illumination
Illuminated scale or dial
Edge illuminated modifier or light rod/pipe
C362S555000, C362S230000, C362S023000, C116S288000
Reexamination Certificate
active
06820991
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a light emitting apparatus that projects light emitted by a light emitting diode through a light guiding member. More particularly, it relates to a light emitting apparatus and a vehicle instrument panel display used in vehicles or as the pointer of various meters.
BACKGROUND ART
Light emitting apparatuses currently in use include, for example, light bulbs and fluorescent lamps that are used so that meters of automobiles and motorcycles can be recognized at night. Light bulbs, however, are not appropriate due to problems related to reliability, power consumption and size. Fluorescent lamps have problems such as requiring ancillary devices necessary for alternating current driving, and containing mercury that is used inside the lamp and may be released into the atmosphere when the vehicle is scrapped. Meanwhile, a light emitting diode having a relatively simple constitution of a single-chip, 2-terminal construction that is capable of emitting white light has been developed. Such a light emitting diode uses an LED chip that is a semiconductor light emitting device having high reliability with low power consumption and is capable of being designed to be small in size, and a fluorescent substance that converts light emitted by the LED chip in at least a part of the spectrum so as to emit blended light such as white light.
The light emitting diode as described above may be applied to a meter pointer of a vehicle or a bar-shaped light source as shown in FIG.
6
. The apparatus shown in
FIG. 6
comprises bullet-shaped light emitting diodes
602
disposed at an end of a needle-shaped light guiding member
601
. The light emitting diode comprises an LED chip and a fluorescent substance that absorbs light emitted by the LED chip and converts the wavelength thereof. When the light emitting diode is fed with current, blue light emitted by the LED chip and color-blended light produced by the fluorescent substance that absorbs the blue light emitted by the LED chip and emits yellow light are introduced into a light guiding member. The light guiding member is covered with a reflecting member except for a surface thereof through which light is emitted, so that light is repetitively reflected within the light guiding member before being emitted in a needle-shaped beam through the surface that is not covered by the reflecting member. By using the needle-shaped light guiding member of such a construction as a meter pointer, such a light emitting apparatus can be made that is small in size, light in weight, high in reliability and efficiency, and is environment-friendly.
However, the light emitting apparatus of the constitution described above cannot meet the requirements of higher brightness and smaller size that are currently imposed in such a trend that the meter panel is covered with a filter for decorative purposes. While light intensity can be increased by increasing the current supplied to the light emitting apparatus, there is a limitation due to heat dissipation, rated operating current, circuit construction, and other factors. When the number of light emitting diodes shown in
FIG. 6
is simply increased, on the other hand, a larger space is required and color blending between the light emitting diodes becomes a problem. That is, while the light emitting diode is formed on a semiconductor wafer by a MOCVD process or the like, it is very difficult to achieve a uniform light emission characteristic, drive characteristic and other properties among some 20,000 pieces of semiconductor light emitting diode that are manufactured from the same wafer, since the properties are affected by the flow rate of gas, temperature distribution and other factors.
As a result, when two or more LED chips are used, there is such a problem that unevenness in color and/or brightness of light emitted by the light emitting apparatus through blending of light from the plurality of LED chips leads to a lower yield of production. Selective use of the LED chips also results in a lower yield of production.
In the case of a light emitting diode that utilizes light emitted by an LED chip and a fluorescent substance that absorbs the light emitted by the LED chip and converts the wavelength thereof, in particular, the problems described above become conspicuous together with the problems of light emission characteristic and uneven distribution of the fluorescent substance. These problems are serious because the human eye is capable of perceiving a difference in hue more distinctly in a white region.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a light emitting apparatus capable of satisfactorily blending light color and emitting light with high brightness with a small construction, and a vehicle instrument panel display.
The present invention provides a light emitting apparatus comprising a light guiding member that projects light, that is incident on an end face thereof, through a principal plane, and a plurality of light emitting diodes that are optically coupled with the end face. The light guiding member has a protruding surface formed in part of the end face thereof, and comprises a first light introducing portion that is formed on the protruding surface and is optically coupled to a first light emitting diode. A second light introducing portion is optically coupled to a second light emitting diode and is formed on the rest of the end face. The constitution described above produces a light emitting apparatus capable of satisfactorily blending light colors and emitting light with high brightness. In the present invention, the light guiding member preferably has a part of a surface protruding on the side of the principal plane that emits light or on the side opposing the principal plane. Such a constitution described above produces a light emitting apparatus capable of satisfactorily blending light colors and emitting light with high brightness.
Also in the present invention, the first light emitting diode and the second light emitting diode are preferably surface-mounted light emitting diodes, with a light emitting portion of the first light emitting diode being higher than that of the second light emitting diode. In this constitution, since the portion of the light emitting plane of the first light emitting diode where the emitted light is observed is higher than the second light emitting diode, all the light emitted by the first light emitting diode is introduced into the light guiding member without being blocked by the second light emitting Therefore, a light emitting apparatus of high brightness can be made.
The present invention also provides a light emitting apparatus comprising a light guiding member that has a distal end, an end face opposing the distal end, and a principal plane located between the former two so as to project the light incident on the end face through the principal plane, and at least first and second light emitting diodes are optically connected to the end face of the light guiding member. The end face of the light guiding member is made in such a structure that the optical path over which light propagates through the light guiding member is different in length depending on which of the light emitting diodes emits the light. Such a constitution described above produces a light emitting apparatus capable of satisfactorily blending light colors and emitting light with high brightness.
In the present invention, the light guiding member has a shape of a plate having the end face and an end face opposing the former end face. The end face of the light guiding member has two portions corresponding to the first and second light emitting diodes, and the optical path between the first end face portion and the end face is made longer than the optical path between the other end face portion and the end face. Such a constitution described above produces a light emitting apparatus capable of satisfactorily blending light colors and emitting light with high brightness.
Also in the present invention, the end face of the light g
Kurokawa Kazumasa
Tominaga Hiroshi
Wakaki Ryosuke
Nichia Corporation
Sember Thomas M.
Truong Bao Q.
Wenderoth , Lind & Ponack, L.L.P.
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