Illumination – Illuminated scale or dial – Edge illuminated modifier or light rod/pipe
Reexamination Certificate
2002-04-18
2004-03-16
Husar, Stephen (Department: 2875)
Illumination
Illuminated scale or dial
Edge illuminated modifier or light rod/pipe
C362S035000, C349S065000, C385S146000
Reexamination Certificate
active
06705739
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a display apparatus, more particularly to a backlighting module for a display apparatus.
2. Description of the Related Art
Backlighting modules are used to provide illuminating light to liquid crystal displays. Referring to
FIG. 1
, a conventional backlighting module
1
is shown to include a linear light source
11
, a light guide
12
, a reflector plate
13
, a light diffuser
14
, and a prism unit
15
including two prisms
151
,
152
.
The linear light source
11
is disposed adjacent to a light-incident end of the light guide
12
. Light from the linear light source
11
is radiated toward the light guide
12
or is reflected by a reflector
111
toward the light guide
12
. By virtue of optical elements on a lower surface of the light guide
12
, and by virtue of the reflector plate
13
disposed beneath the light guide
12
, which cooperate to impair the total reflection phenomenon, light incident on the light guide
12
is diffused within a certain angular range at an upper light-emergent surface of the light guide
12
toward the light diffuser
14
in a relatively uniform distribution. The light further propagates through the light diffuser
14
and the prism unit
15
for viewing angle adjustment so that the illuminating light can spread out within a certain viewing angle range of a liquid crystal display (not shown).
As the light guide
12
is the main light propagating medium in the backlighting module
1
, the shape and material of the light guide
12
determine the luminosity and uniformity of the light from the light-emergent surface of the light guide
12
. In order to enhance the luminosity and uniformity of the light from the light-emergent surface of the light guide
12
, there are available various methods of forming light guides of different constructions, including injection molding, dot-printing, etching, cutting, sand blasting, etc.
Referring to
FIG. 2
, the optical elements in the light guide
12
include a plurality of elongated grooves
121
formed by cutting in the lower surface of the light guide
12
. Each of the grooves
121
extends in a direction transverse to the light propagating direction of the light source
11
. The light-emergent surface of the light guide
12
is also formed with a plurality of elongated grooves
122
that are transverse to the grooves
121
. The total reflection effect of the light guide
12
is destroyed by virtue of two reflective surfaces
123
of each of the grooves
121
,
122
.
The thickness of the light guide
12
in general ranges from several hundredths of a millimeter to several millimeters. The grooves
121
,
122
have a depth ranging from 15 to 100 micrometers (&mgr;m, &mgr;=10
−6
), and a width ranging from 30 to 200 micrometers. Therefore, the depth and width of the grooves
121
,
122
are very insignificant when compared to the thickness of the light guide
12
.
FIG. 3
illustrates the construction of another light guide
12
′, which is formed with a plurality of micro-reflectors
125
on a lower surface thereof. Aside from contributing to the impairment of the total reflection effect of the light guide
12
′, the micro-reflectors
125
can also control the viewing angle distribution of the light emitted from the light-emergent surface of the light guide
12
′. By controlling the number of the micro-reflectors
125
on the light guide
12
′, the light emergent therefrom can be effectively modulated.
In the conventional backlighting module
1
of
FIG. 1
, the reflector plate
13
is required to reflect light escaping from the lower surface of the light guide
12
or
12
′ back into the light guide
12
or
12
′. However, the use of the reflector plate
13
increases the overall size and weight of the backlighting module
1
. Besides, as a clearance, though insignificantly small, is present between the reflector plate
13
and the light guide
12
(
12
′), there will be loss of light, which will reduce the rate of reflection. Hence, there is a need in the art for an improved backlighting module.
SUMMARY OF THE INVENTION
Therefore, the main object of the present invention is to provide a backlighting module for a display apparatus, which includes a compact light guide that can reduce the overall size of the backlighting module and minimize undesirable loss of light to enhance the reflection rate.
According to the present invention, a backlighting module for a display apparatus includes:
a linear light source;
a light guide including a plate body disposed adjacent to the light source in a first direction corresponding to a light propagating direction of the light source, the plate body having first and second surfaces opposite to each other in a second direction that is transverse to the first direction, the light guide further including a dielectric layer formed on the first surface of the plate body, and a reflective layer formed on one side of the dielectric layer opposite to the first surface of the plate body, the dielectric layer having a refractive index smaller than that of the plate body, the light guide having a light incident end proximate to the light source in the first direction, wherein light from the light source enters into the light guide via the light incident end, is guided by the light guide toward the second surface of the plate body, and exits the light guide via the second surface of the plate body;
a light diffuser disposed on the second surface of the plate body to receive and diffuse light that exits from the second surface of the plate body; and
a prism assembly disposed on the light diffuser to receive and distribute light from the light diffuser.
REFERENCES:
patent: 6196692 (2001-03-01), Umemoto et al.
patent: 6364497 (2002-04-01), Park et al.
Helix Technology Inc.
Husar Stephen
Keefer Timothy J.
Wildman Harrold Allen & Dixon LLP
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