Linear light source unit

Details Linear light source unit Linear light source unit

1999-03-24

2001-02-27

O'Shea, Sandra (Department: 2875)

Illumination

Illuminated scale or dial

Edge illuminated modifier or light rod/pipe

C362S327000, C362S035000

Reexamination Certificate

active

06193383

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a linear light source unit for emitting a linear light beam, which unit is used in a facsimile transmitter, copy machine, image scanner, barcode reader, and others, as a light source for reading images.
In recent years, the light emitting diode (LED) is widely used as a light source for reading the image in a personal facsimile. This tendency is caused by the facts that the LED is suitable for miniaturizing the device, necessary light quantity reduces because the sensitivity of the CCD type sensor is increased, and hence the number of used LED reduces, which causes the manufacturing cost of the device to decrease.
In the linear light source unit, a light leading member is provided for leading the light beam to a linear light beam.
FIG. 8
is a perspective view showing a conventional linear light source unit. In
FIG. 8
, reference numeral
20
designates a linear light source unit which comprises a transparent light leading member
21
made of plastic and formed into a flat plate, and a plurality of LEDs
23
linearly mounted on a print substrate
22
. In order to uniformly distribute light quantity on the LED arranged line, an incidence portion
21
b
of the light leading member is formed into a semicircular shape, inclined walls
21
c
are formed on both sides to form guide surfaces, and a light discharge surface
21
a
is formed into a saw teeth surface or embossing surface. Namely, the distribution of quantity of light is adjusted by using diffusion, refraction and reflection of light.
However, the above described conventional linear light source unit can not achieve a uniform light distribution, and has a problem that an immediately upper portion of the light source becomes most bright.
In addition, in order to improve the uniformity of the light quantity, a plurality of LEDs must be provided, which results in increase of the manufacturing cost of the linear light source unit.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a linear light source unit which may uniformly irradiate a long linear portion with a small number of LEDs, thereby reducing the size of the unit and the manufacturing cost thereof.
According to the present invention, there is provided a linear light source unit comprising, at least one light source, an elongated transparent light leading member provided above the light source, an incidence surface formed in the light leading member opposite to the light source, at least one central hole formed in the light leading member at a position above the light source, the hole having an inverted triangular shape, opposite sides of the hole being provided for reflecting light beams emitted from the light source in a longitudinal direction of the light leading member.
The light leading member has opposite reflecting surfaces radially extending and expanding from the incidence portion.
The incidence surface has a semicircular shape in section.
Each of the opposite sides of the hole is formed by a part of a parabolic line surface.
A plurality of side holes are formed in the light leading member at opposite sides of the central hole.
A pair of notches are also formed in the light leading member at opposite sides of the incidence surfaces.
These and other objects and features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings.


REFERENCES:
patent: 4630895 (1986-12-01), Abdala
patent: 4729185 (1988-03-01), Baba
patent: 4929062 (1990-05-01), Guzik
patent: 5197792 (1993-03-01), Jiao et al.
patent: 5414598 (1995-05-01), Anderson
patent: 5833517 (1998-11-01), Konda
patent: 5876107 (1999-03-01), Parker
patent: 0732679 (1996-09-01), None
patent: 2270409 (1994-03-01), None

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