Image sensor and facsimile apparatus incorporating the same

An image sensor and a facsimile apparatus incorporating the same. The upper surface of a substrate with a light receiving device attached thereto is pushed upward so as to fix the substrate to a frame. Since the substrate is fixed to the frame at the upper surface of the substrate, it is easy to adjust the focus of an optical system on the light receiving portion.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an image sensor used for a facsimile 
machine, an optical character reader, etc. and a facsimile apparatus 
incorporating such an image sensor. 
2. Description of the Related Art 
A conventional image sensor is generally provided with a transparent cover 
attached to the upper portion of a frame so as to place an object being 
photographed thereon, a light emitting portion for projecting light onto 
the object, an optical system for receiving the light reflected from the 
object, and a light receiving portion for receiving the light from the 
optical system. The light emitting portion and the light receiving portion 
are provided on respective substrates which are fixed to the frame. In 
most image sensors, the substrate having the light emitting portion is 
attached to the frame in an inclined manner so as to project light onto 
the transparent cover obliquely, and the substrate having the light 
receiving portion is fixed to the lower portion of the frame so as to 
receive the light reflected from the object perpendicularly downward. 
The substrate having the light receiving portion is attached to the frame 
by one of the following three methods: 
(a) The upper surface (the surface on which the light receiving portion is 
provided) of the substrate is pushed downward by an elastic member which 
is provided in the frame, and the under surface (the opposite surface to 
the upper surface) of the substrate is pressed against the lower portion 
of the frame and fixed thereto. 
(b) The substrate is fixed to the frame by screwing it from the under 
surface of the substrate. That is, the upper surface of the substrate is 
pressed against the frame. 
(c) The under surface of the substrate is fixed to the lower portion of the 
frame by an adhesive. 
In the method (a) of pushing the substrate downward and fixing the under 
surface of the substrate to the lower portion of the frame, the under 
surface of the substrate comes into contact with the lower portion of the 
frame. In other words, since the substrate is fixed to the frame at the 
under surface, the accuracy of the frame and the uniformity in thickness 
of the substrate have much influence on the focal length between the light 
receiving portion and the optical system, thereby making it difficult to 
adjust the focus on the light receiving portion, which deteriorates the 
picture quality when it is used for a facsimile machine or the like. In 
the method (c) of fixing the under surface of the substrate to the lower 
portion of the frame by an adhesive, since the substrate sticks to the 
frame, it is impossible to replace the light receiving portion. 
In the case (b) of fixing the substrate to the frame by screwing it from 
the under surface of the substrate, since the substrate is fixed to the 
frame at the upper surface, although the focal distance between the light 
receiving portion and the optical system is slightly influenced by the 
accuracy of the frame, it is not in the least influenced by the thickness 
of the substrate, so that it is easy to adjust the focus on the light 
receiving portion. However, since it is necessary to form a threaded hole 
in the frame and to form a through hole in the substrate, not only does 
the cost increase but also the substrate must be increased in size in 
order to prevent the strength of the substrate from being reduced due to 
the through hole. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to eliminate the 
above-described problems in the related art and to provide an image sensor 
which facilitates the adjustment of the focus of an optical system on a 
light receiving portion, which allows a light receiving portion to be 
replaced and which enables a substrate to be fixed to a frame at a low 
cost, and a facsimile apparatus which incorporates the image sensor. 
To achieve this aim, the present invention provides an image sensor 
comprising an elastic member for fixing the upper surface of a substrate 
with a light receiving portion attached thereto to a frame. Since the 
upper surface of the substrate with the light receiving portion attached 
thereto is pressed against the upper portion of the frame by the elastic 
member, it is easy to adjust the focus on the light receiving portion. In 
addition, since the substrate is fixed to the frame by the elastic member 
which presses the substrate against the frame, it is possible not only to 
replace the light receiving portion but also to fix the substrate to the 
frame at a low cost. 
The above and other objects, features and advantages of the present 
invention will become clear from the following description of the 
preferred embodiments thereof, taken in conjunction with the accompanying 
drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
An image sensor according to the present invention will now be explained 
with reference to preferred embodiments. A first embodiment of an image 
sensor according to the present invention is shown in FIG. 1. In this 
embodiment, a transparent cover (glass cover) 12 is attached to the upper 
portion of a frame 11. In the frame 11 are disposed a substrate 15 having 
a light emitting device 13 such as an LED chip as a light emitting 
portion, and a light receiving device 14 such as a photodiode chip as a 
light receiving portion, and a rod lens array 16 as an optical system for 
converging the light from a copy W on the glass cover 12. 
The under surface of the substrate 15 is pushed upward by a curved spring 
17 having a U-shaped section provided in the lower portion of the frame 11 
as an elastic member so that the upper surface of the substrate 15 is 
pressed against protruded walls 11a, 11b formed on the inner wall of the 
frame 11, thereby fixing the substrate 15 to the frame 11. In this way, 
since the substrate 15 is fixed to the frame 11 at the upper surface of 
the substrate 15 having the light receiving device 14, it is easy to 
adjust the focus of the rod lens array 16 on the light receiving device 14 
irrespective of the accuracy of the frame 11. In this embodiment, the 
curved spring 17 is provided not extending over the total length of the 
image sensor, but leaving approximately a quarter of the total length at 
both ends of the frame 11. 
The rod lens array 16 is provided in such an inclined manner that the 
optical axis thereof has an oblique angle relative to the surface of the 
glass cover 12, and a lens supporter 18 presses the rod lens array 16 
against the inner wall of the frame 11, thereby fixing the former to the 
latter. In order to efficiently introduce the light from the light 
emitting device 13 to the copy W, a light reflecting mirror 19 is provided 
in the frame 11, and the surface of the lens supporter 18 which opposes 
the light reflecting mirror 19 also has a light reflecting function. 
In this image sensor, the light emitting device 13 is situated directly 
under the glass cover 12, and the light receiving device 14 is situated on 
the optical axis of the rod lens array 16. Therefore, the light emitted 
from the light emitting device 13 is converged by the rod lens array 16, 
and received and converted into an electric signal by the light receiving 
device 14. 
FIG. 2 shows a second embodiment of an image sensor according to the 
present invention. In this embodiment, a frame 21 is fitted into a bottom 
case 30 having a U-shaped section and is removably engaged therewith at 
projections 30a, 30b. A glass cover 22 is provided at the upper portion of 
the frame 21. A substrate 24 having a light emitting device 23 as a light 
emitting portion and a substrate 26 having a light receiving device 25 as 
a light receiving portion are provided in the vicinity of the middle 
portion and at the lower portion, respectively, of the frame 21. The 
substrate 24 is unmovably supported by a supporting piece 27 which is 
attached to the frame 21. A rod lens array 29 is disposed at the middle 
portion of the frame 21 so as to be perpendicular to the glass cover 22 
and the substrate 26, and the optical axis of the rod lens array 29 is 
also perpendicular thereto. 
The under surface of the substrate 26 is pushed upward by a sponge 28 
having a rectangular section provided at the bottom plate of the bottom 
case 30 as an elastic member, and the upper surface of the substrate 26 is 
pressed against protruded walls 21a, 21b of the frame 21, thereby fixing 
the substrate 26 to the frame 21. Since the substrate 26 is fixed to the 
frame 21 at the upper surface of the substrate 26, it is easy to adjust 
the focus of the rod lens array 29 on the light receiving device 25 in the 
same way as in the first embodiment. The sponge 28 need not be provided 
extending over the total length of the image sensor, and it may be 
provided at, for example, three portions (both ends and the central 
portion) of the bottom plate of the bottom case 30 at regular intervals. 
In this image sensor, the light emitted from the light emitting device 23 
is projected onto the copy W on the glass cover 22 at about 45 degrees 
with respect to the glass cover 22. The light reflected from the copy W 
perpendicularly to the glass cover 22 passes through the rod lens array 
22, and is received and converted into an electric signal by the light 
receiving device 25 directly under the rod lens array 22. 
In this embodiment, as the substrate 26 is pushed upward by the sponge 28 
having a rectangular section provided on the bottom plate of the bottom 
case 30, and the bottom case 30 is removable from the frame 21, assembly 
of the image sensor is easy. 
FIG. 3 shows a third embodiment of an image sensor according to the present 
invention. This embodiment has approximately the same structure as that of 
the second embodiment. A frame 31 is fitted into a bottom case 40 having a 
U-shaped section and is removably engaged therewith at projections 40a, 
40b. A glass cover 32 is provided at the upper portion of the frame 31. A 
substrate 34 having a light emitting device 33 as a light emitting 
portion, a substrate 36 having a light receiving device 35 as a light 
receiving portion and a connector 41, and a rod lens array 39 are provided 
in the frame 31. The substrate 34 is unmovably supported by a supporting 
piece 37 which is attached to the frame 31. 
The under surface of the substrate 36 is pushed upward by a leaf spring 38 
provided at the bottom plate of the bottom case 40 as an elastic member, 
and the upper surface of the substrate 36 is pressed against protruded 
walls 31a, 31b of the frame 31, thereby fixing the substrate 36 to the 
frame 31. Since the substrate 36 is fixed to the frame 31 at the upper 
surface of the substrate 36, it is easy to adjust the focus of the rod 
lens array 39 on the light receiving device 35. 
As described above, according to these embodiments, since the substrate 
having the light receiving device is fixed to the frame at the upper 
surface of the substrate, it is easy to adjust the focus of the optical 
system on the light receiving portion. Since the substrate is pressed 
against the frame by an elastic member such as a curved spring, a sponge 
or a leaf spring, it is easy to replace the light receiving portion, which 
leads to a reduction in cost. 
The material of the elastic member may be selected from various materials 
such as resin, metal and rubber. 
FIG. 4 shows the internal structure of a facsimile machine with an image 
sensor having the above-described structure mounted therein. 
A facsimile machine B comprises a copy supplying portion 51, an image 
sensor 52 as an image reader, a substrate 53 having a control portion for 
controlling the operation of the facsimile machine as a whole including 
transmission/reception, a printing portion 54, a copy discharging portion 
55a, 55b and a power source 56. 
The operation of the facsimile machine B will now be explained. When a copy 
50 is supplied into the copy supplying portion 51, the copy 50 is 
transferred by platen rollers 57a, 57b. The image sensor 52 reads the 
image of the copy 50 and outputs the image information to the control 
portion in the form of an electric signal. The electric signal input to 
the control portion is transmitted to an external machine through a 
telephone line or the like. After the image of the copy 50 is read, the 
copy 50 is discharged from a copy discharging portion 55a. 
When the control portion receives the signal transmitted from an external 
machine, the control portion so controls the printing portion 54 as to 
print the transmitted image on printing paper 58. The printed paper 58 is 
discharged from a copy discharging portion 55b by a platen roller 57c. 
By using the image sensor of the present invention as the image sensor 52 
of the facsimile machine B having the above-described structure, it is 
easy to read an image accurately and it is possible to obtain a good 
picture quality. 
While there has been described what are at present considered to be 
preferred embodiments of the invention, it will be understood that various 
modifications may be made thereto, and it is intended that the appended 
claims cover all such modifications as fall within the true spirit and 
scope of the invention.