Apparatus for sensing information on both sides of documents

In a document for sensing information, while the document to be sensed is fed in one direction, both surfaces of the document are illuminated by the respective sources of light. Light reflected by one and then the other surface of the document alternately reach a one-dimensional image pickup element. The light sources may be turned on and off. Alternately, the sources of light may be left on, in which case light reflected by both surfaces of the subject are intermittently interrupted.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an apparatus for sensing or reading information 
on the front and back surfaces of documents. 
2. Description of the Prior Art apparatus, when it is desired to read 
information existing on both the front and back surfaces of an original 
document sheet, the apparatus is ordinarily operated first to read the 
information existing on one surface of the original sheet and second to 
read the information existing on the opposite surface thereof. It is 
therefore necessary to reverse the original document after the completion 
of the first reading operation and before the commencement of the second 
reading operation Generally, such reversing of the original document is 
manually made by the operator. Alternatively, the apparatus may be 
provided with a mechanism for automatically reversing the original 
document to eliminate the operator's manual operation. However, the 
provision of such a mechanism results in an increase in cost and decrease 
in reliability of the apparatus. 
An improved apparatus is also known in which a pair of image pickup sensors 
are provided to be disposed facing respectively the front and back 
surfaces of the original sheet so that the information existing on both 
surfaces of the original sheet can be simultaneously read by the 
apparatus. However, such an apparatus also leads to the problem of high 
cost and low reliability. 
SUMMARY OF THE INVENTION 
It is, therefore, an obJective of the present invention to provide an 
apparatus capable of reading information presented on the front and back 
surfaces of a document to be read with a single image pickup means without 
requiring any reversing operation of the subject. 
In order to achieve the above mentioned objective, document sensing 
apparatus in accordance with the present invention comprises a means for 
feeding a document to be read, sources of light for illuminating both 
surfaces of the document, and a light intermitting means for alternately 
passing a beam of light reflected by the one surface of the subject and a 
beam of light reflected from the other surface thereof to an image sensor 
such as a linear CCD.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIGS. 1a and 1b are front and plan views, respectively, for illustrating 
the disposition of the main components of the first embodiment of the 
present invention, wherein an original document in the form of a sheet 1 
is inserted into a slot formed in one end of the apparatus for sensing 
information A, and then fed in the direction shown by an arrow X by pairs 
of rollers 2, 2' and 3, 3' provided in appropriate positions for pinching 
the original 1 on its upper or front and lower or back surfaces. In order 
to sense the information existing on the front and back surfaces of the 
sheet 1 while it is moved between the rollers 2, 2' and 3, 3' , an array 
of light emitting elements 4 for illuminating the front surface of the 
original sheet 1 is disposed perpendicular to the direction of movement of 
the latter, another array of light emitting elements 5 for illuminating 
the back surface of the sheet 1 being also provided in the position 
opposite to the array 4 with respect to the original sheet 1. Each of the 
arrays 4 and 5 includes a plurality of LEDs arranged in a line of a length 
corresponding to the width of the original sheet 1. 
The arrays of light emitting elements 4 and 5 are controlled by a suitable 
control circuit (not shown) so that they are alternately turned on and off 
at regular intervals. Thus, as shown in FIG. 2a, when the array of light 
emitting elements 4 is turned on the array of light-emitting elements 5 is 
turned off (the intervals a and c of FIG. 2a). On the other hand when the 
array of light-emitting elements 4 is turned off, the array of 
light-emitting element 5 is turned on (the interval b of FIG. 2a). When 
either array of light-emitting elements 4 or 5 is turned on, a narrow 
elongate area R (the hatched portion of FIG. 2b) of the front or back 
surface of the original sheet 1 is illuminated and the information 
existing on the area R is read. The area R is located perpendicular to the 
direction of movement of the original sheet 1. Thus, by appropriately 
choosing the speed of movement of the original sheet 1 and the interval of 
turning on and off of the arrays of light-emitting elements 4, 5, the 
whole front and back surfaces of the original sheet 1 are sequentially 
illuminated as the original sheet moves, and all the information can be 
sensed. After the sensing has been completed with the aid of the arrays of 
light-emitting elements 4, 5, the original sheet 1 is fed through a 
predetermined path to a sheet receiver tray (not shown). Light reflected 
from the elongate areas R on the front and back surfaces of the original 
sheet 1 illuminated by the arrays of light-emitting elements 4, 5 are 
reflected by mirrors 6, 7 disposed parallel to the arrays 4, 5 on the 
upper and lower sides of the original sheet 1, and then propagate in the 
direction of the arrow X. The apparatus for sensing information A is 
further provided at its opposite end with a mirror 8 for reflecting 
downwardly the light which has been reflected by the mirror 6, and also 
with a mirror 9 for similarly reflecting downwardly the light which has 
been reflected by the mirror 7, the mirror 9 being positioned further from 
the original sheet 1 than the mirror 8. Light reflected by the mirror 8 is 
further reflected by a half mirror 10 positioned in a lower portion of the 
apparatus A, and then focused through lens 12 onto a one-dimensional image 
sensing means shown as pickup element 13. Element 13 can be a conventional 
CCD linear image sensor which senses a line of information at a time. 
Similarly, light reflected by the mirror 9 is further reflected by a 
mirror 11 positioned in a lower portion of the apparatus A, and 
transmitted through the half mirror 10 and thereafter focused through the 
lens 12 onto the element 13. 
The front and back surfaces of sheet 1 are scanned by beams of light in the 
period during which the array of light-emitting elements 4 and 5 are 
turned on and the one-dimensional image pickup element 13 outputs 
electrical signals corresponding to the images focused on the image pickup 
element; that is, electric signal which represent the line of pixel 
information contained in the narrow areas R illuminated by the arrays 4 
and 5. The operation of the one-dimensional image pickup element 13 is 
controlled by synchronizing the movement of the sheet 1 with the alternate 
on-off operation of the arrays of light-emitting elements 4 and 5. 
As will be understood from the above description, the information existing 
on the front and back surfaces of the original sheet 1 is sensed 
sequentially line by line when the original sheet 1 is moved by the 
rollers 3, 3' between the arrays of light-emitting elements 4 and 5, and 
then alternatively focused on the one-dimensional image pickup element 13 
through the half mirror 11 and the lens 12. This makes it possible to 
avoid a troublesome reversing operation of the original sheet and to sense 
the information on both the front and back surfaces of the sheet using a 
single image accepting element. 
As shown in FIG. 3, furthermore, it is also possible to arrange that only 
the array of light-emitting elements 4 is left on for illuminating the 
front surface of the original sheet 1 during the period when the original 
sheet moves in one direction by a distance corresponding to the whole 
length of the original sheet (interval f), and thereafter only the array 
of light-emitting elements 5 is left on for illuminating the back surface 
of the original sheet during a subsequent period when the original sheet 
returns in the opposite direction (interval r). This also makes it 
possible to sense the information on both the front and back surfaces of 
the original sheet with a single image pickup element without reversing 
the original sheet. 
FIG. 4 is a front view showing the disposition of the main components of 
the second embodiment of a document information sensing apparatus in 
accordance with the present invention. In this second embodiment, in place 
of the arrays of light-emitting elements 4 and 5 of the first embodiment, 
a pair of light sources 14 and 15 are provided. These light sources are 
disposed on the front and back sides of the original sheet 1, and left on 
in operation. A pair of conventional liquid crystal shutters 16 and 17 are 
provided between the light sources 14, 15 and the original sheet 1. When 
the liquid crystal shutters 16 and 17 are operated to alternately open and 
close in synchronism with the scanning timing of the one-dimensional image 
pickup element 13, and the speed of movement of the original sheet 1 is 
appropriately set, it is possible, as in the first embodiment, to sense 
the information both on the front and back surfaces of the original sheet 
with a single image pickup element without reversing the original sheet. 
FIG. 5 is a front view showing the disposition of the main components of 
the third embodiment of an information sensing apparatus in accordance 
with the present invention, in which the liquid crystal shutter 16 of the 
second embodiment is disposed in the light path between the mirrors 6 and 
8, and the liquid crystal shutter 17 also in the light path between the 
mirrors 7 and 9. 
FIG. 6 is a front view showing the disposition of the main components of 
the fourth embodiment of document information sensing apparatus in 
accordance with the present invention. As with the third embodiment, the 
fourth embodiment is also arranged to illuminate the original sheet 1 with 
the light sources 14, 15 which are left on, but a light-interrupting 
element 18 is provided in place of the liquid crystal shutters 16, 17. The 
light-interrupting element 18 is movable between one position in which it 
interrupts light reflected on the front surface of the original sheet 1 
and then directed to the one-dimensional image pickup element 13, and 
another position in which it interrupts light reflected on the back 
surface of the original sheet 1 and then directed to the one-dimensional 
image pickup element 13, so that the element 18 is in one position during 
the period of interval f shown in FIG. 3, for example, and then also in 
the other position during the period of interval r, thereby allowing the 
information on both the front and back surfaces of the original sheet 1 to 
be read 
FIGS. 7a7b and 7c are front, plan and side views, respectively, showing the 
disposition of the main components of the fifth embodiment of an 
information sensing apparatus in accordance with the present invention. 
The fifth embodiment is intended to provide means for making the apparatus 
compact and is effectively applicable to the information reading apparatus 
of any one of the first to fourth embodiments described above. As an 
example, a case in which such means is applied to the first embodiment 
will be described below. As in the first embodiment, light reflected from 
the front and back surfaces of the original sheet 1 are reflected by the 
mirrors 6 and 7, respectively, and then directed in the same direction as 
that of the movement of the original sheet 1 to mirrors 19 and 20. These 
mirrors are respectively disposed in the paths of propagation of those 
light beams at the angle of 45 degrees with respect to the paths of light 
beams on the upper and lower sides of the plane including the original 
sheet 1. Thus, the light beam from the mirror 6 is reflected by the mirror 
19 and the light beam from the mirror 7 is also reflected by the mirror 
20, and each of the reflected beams is directed in the direction 
perpendicular to the direction of movement of the original sheet 1 along 
the plane of the original sheet 1 (towards the viewer seeing FIG. 7a) 
The light beam reflected by the mirrors 19, 20 are further reflected by the 
mirrors 8, 9 downwardly at right angles. The mirrors 8, 9 are positioned 
on the front side of the information sensing apparatus A such that the 
light beams reflected by the mirrors 8, 9 are not interrupted by the 
moving original sheet 1. The light reflected by the mirror 8 is further 
directed at right angles by the half mirror 10 and directed towards the 
rear side of the apparatus A to impinge on the lens 12. The light beam 
reflected by the mirror 9 is also reflected at right angles by the mirror 
11 and directed towards the rear side of the apparatus A to transmit 
through the half mirror 10 and impinge on the lens 12. Each of the beams 
which have passed through the lens 12 is focused on the one-dimensional 
image pickup element 13. 
In this manner, the direction of the light beams reflected on the front and 
ba:k surfaces of the original sheet 1 and reaching the one-dimensional 
image pickup element 13 is changed by 90 degrees with respect to the 
direction of movement of the original sheet 1 in the midst of the light 
path and further downwardly on one side of the apparatus A to avoid 
intersection of the light path with the path of movement of the original 
sheet 1. Therefore, the information can be read while the original sheet 1 
is moving from one end to the opposite end of the apparatus A and the 
apparatus can be reduced in size regardless of the length of the original 
sheet 1. 
Although the description has been made with reference to examples of the 
apparatus for sensing information existing on original sheets, the present 
invention is not limited to such examples, but can be applicable to 
apparatus for sensing information recorded on relatively flat media 
documents such as photographs. Therefore, the recording media from which 
the information can be sensed by the apparatus of the present invention 
may generally be referred to as subjects to be read. 
As will be apparent from the above detailed description on the present 
invention with reference to some of its embodiments, the apparatus of the 
invention can alternately sense information existing on the front and back 
surfaces of a subject to be read using a single image pickup element 
without reversing the subject. Thus, it is possible to inexpensively 
manufacture the apparatus, minimize the operator's participation and 
simplify the operation of the apparatus. It is also possible to 
simultaneously complete the reading of information on the front and back 
surfaces of a document to be sensed by synchronizing the on off operation 
of the light sources with the scan timing of the image pickup element. 
The invention has been described in detail with particular reference to a 
certain preferred embodiment thereof, but it will be understood that 
variations and modifications can be effected within the spirit and scope 
of the invention.