Illumination – Plural light sources – With modifier
Reexamination Certificate
2001-03-14
2004-05-04
Husar, Stephen (Department: 2875)
Illumination
Plural light sources
With modifier
C362S247000, C362S248000, C362S240000, C362S347000, C362S800000, C362S303000
Reexamination Certificate
active
06729746
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light source device. The present invention also relates to a signal light utilizing a light source device and a light emitting device for a display and others.
The present application is based on the following Japanese Patent Applications, which are incorporated hereon by reference: 2000-69800, 2000-93333, 2000-135529, 2000-225572, 2000-294264, 2000-294893, 2000-296052, 2000-296053, and 2000-310634.
2. Description of the Related Art
Heretofore, for a light source device used for a signal light, a light source device that has a light bulb as a light source and emits light from a light source via a filter pigmented in each-target color such as red and cyan as desired monochromatic light is generally used. A light source device in which plural lens-type light emitting diodes (LEDs) that emit light of desired color are densely arranged on a board is also known. A light source device having LED as a light source has an advantage that no pseudo-lightening is caused and labor for maintenance can be greatly reduced. In addition, as LED itself emits monochromatic light, external radiation efficiency can be enhanced more than that in a method of using a light bulb that most of emitted light is cut via a filter. Also, in case a filter is used, the color of the filter is displayed by light incident from the outside and may be recognized as if a light source device was turned on, however, in case LED is used for a light source, no filter is required and such pseudo-lightening is not caused. Further, LED is not burn out as a light bulb and has high reliability.
However, as a signal light which has known and has LED as a light source uses lens-type LED as described above, the external radiation efficiency is not enough. The reason is that in lens-type LED, as the directivity is enhanced, loss increases in radiated light and the external radiation efficiency is deteriorated.
Also, to secure sufficient luminous intensity and eliminate the unevenness of emission so that a signal light has satisfactory visibility, LEDs are densely mounted, however, it is troublesome and in addition, as great deal of heat is caused and outgoing radiation is not efficiently performed, LEDs have high temperature. As emission is deteriorated and a life characteristic is deteriorated when LEDs are operated in a state of high temperature, it is not desirable that LEDs are operated in a state of high temperature. Even if the number of LEDs arranged in a fixed area can be reduced by enhancing the output of a light emitting element in future, a problem of the unevenness of emission caused because the mounting number of density of LEDs is reduced, that is, a problem that a signal light does not produce satisfactory visibility is not solved.
Though optics (silver plate on the surface of a lead frame and others) provided to enhance the external radiation efficiency of LED reflects external light and pigmented pseudo-lightening is not caused, it may cause the deterioration of contrast between when LEDs are turned on and when they are turned off.
Reflection-type LED different from lens-type LED is also generally known. As reflection-type LED can utilize light emitted laterally from a light emitting element by reflecting the light on its reflecting surface as external emitted light, it has high external radiation efficiency. As lens-type LED has light distribution characteristics higher in directivity, the external radiation efficiency is greatly deteriorated, however, the external radiation efficiency of reflection-type LED does not depend upon light distribution characteristics. As described above, reflection-type LED is provided with a characteristic that light of high luminance can be radiated at a wide light distribution angle. It is considered that reflection-type LED is installed outdoors and in other place and is suitably used for a display for which high visibility is demanded and others respectively because of such a characteristic.
FIGS. 77 and 78
show a light source device
1200
using conventional type reflection-type LED.
FIG. 78
is a plan viewing the light source device
1200
from the side on which light is radiated outside (from the top in FIG.
77
). In the light source device
1200
, after light from a light emitting element
1110
is once reflected by a reflecting mirror
1120
, it is radiated outside from a radiation surface
1140
. A reference number
1130
denotes an encapsulating member,
1400
and
1410
denote a lead and
1210
denotes LED.
On a display installed outdoors and in other place, when external light is taken in on the side of LED and is reflected, light (dark noise) which looks emitted from the side of LED is also observed when LED is turned off and as a result, a problem that contrast between when LED is turned on and when LED is turned off is deteriorated occurs. Then, to inhibit such dark noise and reduce the deterioration of contrast, a part except the radiation surface of LED is covered with a black or other color of member so that taking in external light on the side of LED is inhibited as much as possible. To take the light source device
1200
as an example, external light is prevented from being taken in from a place except the radiation surface
1140
by a light shielding plate
1300
.
However, as shown in
FIGS. 77 and 78
, as the radiation surface
1140
having large area of LED
1210
is exposed to external light, the deterioration of contrast between when LED is turned on and when it is turned off due to dark noise is still left as a large problem. Such a problem occurs not only in case reflection-type LED is used but in case lens-type LED is used.
Next, a light source device
2005
using another conventional type lens-type LED is shown in
FIGS. 79 and 80
.
FIGS. 79A and 79B
show an optical path of the light source device
2005
.
FIG. 80
is a plan view in which the light source device
2005
is viewed from the side of external radiation of light (from the top in FIGS.
79
). In the light source device
2005
, LED
2100
is arranged in a state that it is fitted into a through hole
2310
provided to a light shielding plate
2300
. Light from a light emitting element (not shown) is radiated outside as light having a desired angle range &agr; from the surface of the lens
2120
of an encapsulating member
2110
. A reference number
2200
denotes a board on which LED
2100
is mounted.
On a display installed outdoors and in other place, when external light is taken in on the side of LED and is reflected, light (dark noise) which looks emitted from the side of LED is also observed when LED is turned off and as a result, a problem that contrast between when LED is turned on and when LED is turned off is deteriorated occurs. To inhibit such dark noise and reduce the deterioration of contrast, a part except the radiation surface of LED is covered with a black or other color of member so that taking in external light on the side of LED is inhibited as much as possible. To take the light source device
2005
as an example, external light is prevented from being taken in on the side of LED by the light shielding plate
2300
.
However, the effect of external light has many problems to be improved. That is, as the surface of the lens
2120
of LED
2100
is exposed to external light, much external light is taken inside LED
2100
via the lens surface
2120
. The taken external light is reflected by optics (silver plate and other on a lead frame) provided to enhance the external radiation efficiency of LED
2100
and is observed as reflected light. As a result, contrast between when LED is turned on and when LED is turned off is deteriorated.
Also, in a shop of the service industry such as a discotheque, a conventional type light emitting device is used for various projectors that emit light for gorgeously decorating the inside intentionally darkened of the shop. For one type of such a projector, there is a light pattern projector that projects a predetermined geometrical pattern on a screen a
Kato Hideaki
Nakano Hideyuki
Omoya Hideki
Suehiro Yoshinobu
Takahashi Yuji
Husar Stephen
McGinn & Gibb PLLC
Payne Sharon
Toyoda Gosei Co,., Ltd.
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