Note: Descriptions are shown in the official language in which they were submitted.
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sACKGRoUND OF THE INVENTION
5 Field of the Invention
The present invention relates to lighting apparatus,
and particularly to a lighting apparatus such as a
flashlig~lt including a light source and reflecting
mirrors .
10 DescripLion of the Background Art
Fig. 3 is a cross sectional view showing a structure
of a conventional f lashlight .
Referring to Fig. 3, a conventional flashlight
includes a body A 13 protecting a battery housing portion
15 lS, a battery cover 17 covering a battery housed in
housing portion 15, and a body B 21 protecting a lamp bulb
7. In body B 21, a reflecting mirror 1 is attached around
lamp bulb 7 for reflecting forward emitted light from lamp
bulb 7, and a lens 19 for P~r~nrlin~ the irradiation range
20 is attac}~ed in front of lamp bulb 7.
Fig. 4 is an enlarged cross sectional view showLng a
structure of and around t}~e lamp bulb and ref lecting
mirror of the f lashlight in Fig . 3 .
First, as the reference basis, a line passing t}lrough
25 the cen~er of lamp bulb 7 is indicated as an X-Y axis and
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the position of a filament 9 of lamp bulb 7 is indicated
as an origin O. The front end of reflecting mirror 1 is
indicated as C, and the rear end is indicated as D. Since
the structure is symmetric with respect to X-Y axis, only
5 the upper half will hereinafter be descr~bed
In this example, an angle COY is 37.5, and an angle
DOY is 92.4. Luminous flux of filament 9 emitted in the
range of the angle COY is directed forward without
ref lected by ref lecting mirror 1. Luminous f lux of
10 filament 9 emitted in the range of the angle DOC is
ref lected by ref lecting mirror 1 to be made parallel to
the axis OY and directed f orward .
Consequently, only the luminous flux in the range of
the angle DOY (92.4o) emitted from filament 9 is directed
15 forward. A solid angle ANG defined by the range of the
luminous f lux to be directed f orward by ref lecting mirror
1 is det~ nin~l as follows:
ANG = 5 . 24 8 ( steradians )
Assuming that filament 9 irradiates uniformly all the
20 directions, the utilization efficiency of luminous flux R
of reflecting mirror is determlned as follows, based on
the solid angle ANG:
R = 41. 896
In the conventional flashlight described above, when
25 a lamp bulb in which a filament irradiates backward (which
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indicates a light source with a solid angle over 6 . 28
steradians ) is used, it can not be said that the backward
luminous flux is effectively utilized.
Fig. 5 shows an example in which backward luminous
5 flux should be utilized for forward irradiation. In Fig.
5, the angle COY is 37.5, which is the same as in Fig. 4,
while the angle DOY is 125.0, which is larger than the
corresponding angle in Fig. 4. Here, a solid angle ANG
and a utilization efficiency of luminous flux Rl of
0 reflectil~g mirror 1 are determined as follows:
ANGI = 8.5887 (steradians)
R~ = 68 . 3~,
showing large increase in the utilization efficiency of
luminous flux. However, for increasing a utilization
15 efficiency of luminous flux with the angle COY being
constant, reflecting mirror 1 must be made larger compared
to Fig. 4, as can be seen from Fig. 5 (compare the
dimensions L in the figures ) . Fig . 6 is a cross sectional
view of a flashlight with the reflecting mirror of Fig. 5
20 incorporated ttlerein. In Fig. 6, the structure around a
lamp bulb is considerably larger compared to that in Fig.
3, which can not be lead to a compact lig~lting apparatus
with a }ligh utilization efficiency of luminous flux.
One ob ject of Llle present invention is to increase a
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utilization efficiency of luminous flux in a lighting
apparatus .
Another object of the present invention is to make
a lighting apparatus compact while maintaining a
utilization efficiency of luminous flux.
According to the present invention there is
provided a lighting apparatus comprising a light source
having a solid angle over 6.28 steradians defined from its
irradiation range; a reflecting mirror for reflecting
light emitted from said light source to direct the
reflected light forward; and a reflex reflecting mirror
provided at least at the back of said light source, for
reflecting the light emitted from said light source to
direct the reflected light toward said light source.
In the lighting apparatus conf igured as described
above, light emitted backward from the light source is
reflected by the second reflecting mirror to be directed
toward the light source, so that the utilization
efficiency of luminous flux can be enhanced while the
apparatus is being made compact.
The foregoing and other objects, features, aspects
and advantages of the present invention will become more
apparent from the following detailed description- of the
present invention when taken in conjunction with the
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accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a cross sectional view showing a structure
of a f lashlight according to one embodiment of the present
5 invention.
Fig. 2 is an enlarged cross sectional view showing a
structure around a lamp bulb of Fig. 1.
Fig. 3 is a cross sectional view showing a structure
of a conventional f lashlight .
Fig. 4 is an enlarged cross sectional view showing a
structure around a lamp bulb of Fig. 3.
Fig. 5 is an enlarged cross sectional view showing
another example of a structure arolmd a lamp bulb of a
conventional f lashlight .
Fig. 6 is a cross sectional view showing a structure
of another conventional f lashlight with the structure
around the lamp bulb of Fig. 5 incorporated thereinto.
DESCRIPTION OF T~E PREFERRED EMBODIMENTS
Fig. 1 is a cross sectional view showing a structure
20 of a flashlight according to one embodiment of the present
invention, and Fig. 2 is an enlarged cross sectional view
of a structure around a lamp bulb and a reflecting mirror
of Fig. 1.
Since an exterior portion of the flashlight is the
25 same as that of the conventional one shown in Fig. 3, the
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description is not repeated and the structure around a
light source will hereinafter be described with reference
to Fig. 2.
In the figure, a reflecting mLrror 1 is provided
5 approximately in front of the position of a filament g of
a lamp bulb 7, and a ref lex ref lecting portion 5 is
provided bet~een ref lecting mirror l and a socket 11 in
which lamp bulb 7 is inserted and fixed thereto.
The structure and function of reflecting mlrror 1 to
10 which a fitting piece 3 is connected are basically the
same as those Qf ref lecting mirror 1 shown in Fig . 4 .
Specifically, an angle COY is 37.5, and an angle DOY is
92.4. 3~uminous flux emitted from filament 9 in the range
of the angle COY is directed forward as it is, while
15 luminous flux emitted from filament 9 in the range of the
angle DOC is reflected by reflecting mirror 1 to be made
parallel to an axis aY and directed iorward.
Reflex reflecting portion 5 is a reflector of
transparent resin and the like, molded so as to have a
20 plurality of rectangular pro ~ections formed on the sphere
centered on a filament 9 as shown in the figure. For
example, light directed from filament 9 to an A point of
ref lex ref lecting portion 5 is ~ef lected by an inner
surf ace of the rectangular protruding portion, to be made
25 parallel to OA and directed to~7ard filament 9. The light
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passing near filament 9 is then incident to a B point on
the lower surface of reflecting mirror 1 and reflected to
be made approximately parallel to the axis OY and directed
f orwa rd .
As described above, provision of reflex reflecting
portion 5 enables light emitted backward f rom f ilament 9
to be utilized as light to be directed f orward . In this
case, luminous flux in the range of an angle EOY (125.0)
is directed forward, and thus its solid angle ANG2 and its
utilization efficiency of luminous flux Rz of reflecting
mirror 1 and reflex reflecting portion 5 are as follows:
ANG2 = 8 . 5 8 8 7 ( s t eradi an s )
Rz = 68.396
Consequently, according to the present invention, lighting
apparatus having the same ~ dimension of the reflecting
mirror portion as in Figs. 3 and 4 shown as conventional
examples, while having the equivalent reflection
efficiency to those in Figs. 5 and 6 can be realized.
In the above embodiment, a reflex reflecting portion
having a plurality of rectangular steps is provided, while
instead, a reflecting element, such as a spherical mirror,
may be provided for reflecting back light from filament 9.
Although the present invention has been described and
illustrated in detail, it is clearly understood that the
same is by way of illustration and example only and is not
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to be taken by way of limitation, the spirit and scope of
the present invention beins limited only by the terms of
the appended claims.
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