Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
2000-03-30
2002-11-05
Allen, Stephone (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C358S475000
Reexamination Certificate
active
06476369
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a linear light source of an image sensor that is used in an image input section of a facsimile apparatus etc. The present invention also relates to a contact image sensor having such a linear light source.
2. Background Art
FIGS. 9-11
show a conventional image sensor that is listed in the Mitsubishi contact image sensor catalogue (produced in February 1993), for example.
FIG. 9
is a sectional view of the contact image sensor,
FIG. 10
shows a linear light source of the contact image sensor, and
FIG. 11
shows the directivity characteristic of each LED chip that is used in the linear light source of the contact mage sensor.
In
FIG. 9
, reference numeral
10
denotes an original document;
20
, a linear light source in which LED chips are arranged linearly;
30
, an erect 1:1 imaging rod lens array, or an erect-image, equimagnification imaging rod lens array, that is composed of a plurality of rod lenses (not shown);
40
, a sensor board;
50
, sensor ICs attached to the sensor board
40
so as to be arranged linearly;
60
, a glass plate on a document running surface;
70
, a sensor frame; and
80
, a path of light that is output from the linear light source
20
and imaged on the sensor ICs
50
.
In
FIG. 10
, reference numeral
90
denotes a LED bare chip;
100
, substrate that is mounted with the respective LED bare chip
90
; and
110
, a resin body with which the respective LED bare chip
90
is sealed. The surface of each resin body
110
, from which light generated by the corresponding LED bare chip
90
is emitted, is flat. An LED bare chip
90
, a substrate
100
, and a resin body
110
constitute a surface mounting type LED chip
120
. Reference numeral
130
denotes a circuit board on which a plurality of LED chips
120
are mounted linearly. The plurality of LED chips
120
and the circuit board
130
constitute an LED array linear light source
20
. Reference numeral
140
denotes an exposed surface (document surface) that is illuminated by the LED chips
120
;
150
, the distance between adjacent LED chips
120
;
160
, paths of light that spreads radially from each LED chip
120
;
170
, the distance between each LED bare chip
90
and the document surface
140
;
180
, an exposure profile of one chip that is obtained when the illumination surface
140
is illuminated by light coming from each LED chip
120
; and
190
, a total exposure profile as the sum of exposure profile
180
of each chip.
Next, the operation will be described with reference to
FIGS. 9-11
. Light that is output from the linear light source
20
passes through the glass plate
60
and illuminates the original document
10
uniformly. The exposed light is reflected by the original document
10
in accordance with light-and-shade information of an image and goes along the path
80
of light. The reflected light passes through the rod lenses of the rod lens array
30
and is imaged on the sensor ICs
50
. The sensor ICs
50
accumulate charges in accordance with the intensity of the reflected light and outputs signals via the sensor board
40
. The linear light source
20
is realized by arranging the point light sources of LED chips
120
, and is composed of the LED bare chips
90
, the substrates
100
, the resin bodies
110
, and the circuit board
130
. Each LED chip
120
has a wide directivity characteristic as shown in
FIG. 11
, and the exposure profile
180
on the document surface is somewhat convex. The total exposure profile
190
as superimposition of the exposure profiles
180
assumes a flat line.
The conventional linear light source is configured in the above-described manner, and each LED chip
120
has the wide directivity characteristic as shown in FIG.
11
. Although the directivity characteristic of
FIG. 11
is the one taken along the surface of the drawing of
FIG. 10
, each LED chip
120
exhibits approximately the same directivity characteristic in the direction perpendicular to the surface of the drawing of FIG.
10
. As for the exposure in the direction perpendicular to the surface of the drawing, it is more efficient to illuminate a reading position in a concentrated manner. However, conventionally, priority is given to uniform illumination of a document and the efficiency of light utilization is sacrificed in the direction perpendicular to the surface of the drawing of FIG.
10
.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above problems in the art, and an object of the invention is therefore to provide a linear light source that has a uniform exposure characteristic and is superior in efficiency of light utilization.
According to one aspect of the present invention, a linear light source comprises a circuit board and a plurality of LED chips arranged linearly on the circuit board, and each of the LED chips has a light condensing function.
In another aspect, in the linear light source, an arrangement interval between the adjacent LED chips is preferably shorter than or equal to a distance between the LED chips and a document exposure surface.
In another aspect, in the linear light source, a ratio between the interval of the adjacent LED chips and the distance from the LED chips to the document exposure surface is preferably determined according to a directivity characteristic of each of the LED chips and an equation
L
(&thgr;)=
L
(0°)/(2·cos
2
&thgr;)
where L(&thgr;) is exposure at an angle &thgr;, and &thgr; is an angle with respect to a perpendicular to the document exposure surface from the LED chips.
Other and further objects, features and advantages of the invention will appear more fully from the following description.
REFERENCES:
patent: 4970606 (1990-11-01), Shima
patent: 5182445 (1993-01-01), Yamashita
patent: 5489992 (1996-02-01), Endo
patent: 5670971 (1997-09-01), Tokimoto et al.
patent: 5926286 (1999-07-01), Fujieda
patent: 6160250 (2000-12-01), Miksch et al.
patent: Sho 61-136369 (1986-06-01), None
patent: Hei 2-222583 (1990-09-01), None
patent: Hei 6-012920 (1994-02-01), None
patent: Hei 7-162586 (1995-06-01), None
patent: Hei 7-183478 (1995-07-01), None
patent: Hei 11-163409 (1999-06-01), None
Allen Stephone
Hill Bradford
Mitsubishi Denki & Kabushiki Kaisha
Rothwell Figg Ernst & Manbeck
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