Document size-detecting device of copying machine

A copying machine having an optical scanner adapted to transfer an optical image onto a photoreceptor during movement between the scanner and the object to be copied. A platen cover with a document-holding surface bears against the document being copied and is provided with a plurality of colored portions corresponding to various sizes of documents in the scanning direction. There is a light projector which irradiates the surface of the platen, including the colored portions, and a light-receiving means adapted to distinguish the colored portions from the rest of the surface. The light receiving means generates an output signal which corresponds to the colored portions and there is a means for determining, from the output, whether the signal is in the range corresponding to the wavelength of the colored portions.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an improvement in a document 
size-detecting device detecting the size of the document placed on a 
platen for a copying machine such as an electrophotographic copying 
machine and others. 
2. Description of the Prior Art 
Heretofore, Japanese Patent Publication Open to Public Inspection No: 
11242/1975 has shown a copying machine wherein copy papers in different 
sizes or papers in roll type are loaded and a sheet of paper with a 
suitable size for the size of a document placed on a platen of the copying 
machine is selected or cut and then conveyed. In the document 
size-detecting device of such copying machine, the light projecting 
devices and the photoelectric converting devices are provided in parallel 
along the diagonal direction of the document on both the document-holding 
cover (platen cover) and the under surface of the platen so that the light 
projecting device and the photoelectric converting device oppose each 
other and the detection of the document size is made based on the 
information of the sizes of output of the photoelectric converting devices 
in parallel. On such a document size-detecting device, owing to the 
dispersion of the sensitivity of photoelectric converting devices in 
parallel, the dispersion and variation of the emission intensity of the 
light projecting device and further to the external light that enters 
leaking through the clearance of the platen cover, it is feared that the 
information on the size of output of the photoelectric converting device 
does not necessarily reflect the size of the document and thereby it 
causes an erroneous selection of the paper. Further, either one of light 
projecting device and photoelectric converting device is provided on the 
platen cover that is opened and closed, therefore a failure tends to take 
place thereon and the shade of the light projecting device or of the 
photoelectric converting device appears on the copy paper, which is 
disadvantageous. 
The present applicant has made a proposal in Japanese Patent Publication 
Open to Public Inspection No. 22424/1981 (U.S. application Ser. No. is 
172,821/1980) with an object to provide the document size-detecting device 
that solves aforesaid problems. The proposal includes a document 
size-detecting device for the copying machine comprising a colored portion 
that is colored to a certain color, the light projecting device 
irradiating the colored portion and the light-receiving member that 
receives the light irradiated from the light projecting device and is 
reflected on the colored portion, and is characterized in that a part of 
or all of the light irradiated from aforesaid light projecting device to 
aforesaid light-receiving member are intercepted by the document placed on 
the platen and thereby the size of the document is detected. 
Namely, in the document size-detecting device of aforesaid proposal, the 
characteristics of the light-receiving member where plurality of the 
detecting elements capable of obtaining signals proportional to the 
wavelength of incident light are arranged, are utilized thereby the 
reflected light or the transmitted light from the colored portion which is 
not covered by the document is detected and the detection of document size 
is made according to the information relating to the existence of 
aforesaid detection made by detecting elements in parallel relating to 
document size. 
Aforesaid proposal has advantages that there is no dispersion of 
sensitivity which has been experienced in the light-receiving member of 
the conventional photoelectric converting device and that it is hardly 
influenced by the dispersion variation of radiation intensity of the light 
projecting device and by the external light whose intensity ratio for the 
specific wavelength relating to the colored portion is low and thereby 
there is not a fear of erroneous operation. On the other hand, however, 
the document size-detecting device of aforesaid proposal has detecting 
elements for each document size to be detected and detection of document 
size is made by the combination of outputs of the detecting elements. 
Therefore it is necessary to use a lot of detecting elements and function 
thereof is complicated, then inexpensive document size-detecting device 
has not been available. Further, when the color of the document is similar 
to or close to the color of colored portion, the detecting capability may 
fall, which has been a disadvantage. 
OBJECTS AND SUMMARY OF THE INVENTION 
An object of the present invention is to improve remarkably the reliability 
by simplifying the circuit structure with only one detecting element and 
by enabling it to detect even in the case that the color of the document 
is similar to or close to the color of the colored portion and further to 
provide an inexpensive document size-detecting device. 
The present invention is intended to attain aforesaid object and to provide 
a document size-detecting device for copying machine wherein plural 
colored portions which are colored to a certain color are provided on the 
document-holding surface of the document-holding member with intervals 
corresponding to the document sizes and the light projector to irradiate 
against aforesaid document-holding surface for each document as well as 
the light-receiving member to receive the reflected light from aforesaid 
document-holding surface are provided and aforesaid document size is 
detected through the output time of the reflected light from the colored 
portion on aforesaid document-holding surface which is not covered by 
aforesaid document. 
Namely, in the present invention, the document is held, while copying, by 
the platen cover whose document-holding surface is furnished with plural 
colored portions with intervals corresponding to the document sizes, the 
light projector to irradiate against the document surface and the 
detecting element to receive the reflected light from the document or the 
document-holding surface which is irradiated by the light projector are 
provided and the time information generated from aforesaid colored portion 
detected by the detecting element is compared with the information stored 
previously in the controlling section on the main body thus the detection 
of document size is made with a coincidence of both information which is 
judged to be colored portion on the surface of document-holding member.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 is an example showing the state of the colored portions provided on 
the document-holding surface of the document-holding member (platen cover) 
in which plural colored portions with a fixed width are provided in the 
direction of scanning for document reading (direction of arrow X in FIG. 
1) with intervals corresponding to document sizes and placing positions of 
documents in various sizes are shown with dashed lines. FIG. 2 is a 
schematic diagram showing an example of a principal part of the copying 
machine having the document-holding surface shown in FIG. 1. Incidentally, 
1a in both FIG. 1 and FIG. 2 represents the starting point for document 
reading scanning. 
On the main body 1 of the copying machine, there are arranged the platen 2 
made of transparent glass on which the document D is placed and the platen 
cover 3 that covers the document D after the document D is placed on the 
platen 2. On the document-holding surface 3a of the platen cover 3 that 
touches the document D, the colored portions shown in FIG. 1 are arranged 
at the fixed locations. 
Under the platen 2 and inside the main body of copying machine, there is 
provided a first mirror unit 6 having thereon an exposure lamp 4 and the 
first mirror 5 so that it can travel rectilinearly in the direction from 
left to right or from right to left in the drawing in parallel with 
aforesaid platen 2, thus it scans optically the entire face of the 
document D. The numerals 7 and 8 are the second mirror and the third 
mirror respectively and the second mirror unit 9 in which the second 
mirror and the third mirror are unified travels rectilinearly in the 
direction from left to right or from right to left at the speed that is 
half the speed of the first mirror unit so that the necessary optical path 
length can be kept. Of course, the movement of the second mirror unit 9 is 
parallel to the platen 2 similarly to aforesaid first mirror unit. The 
light reflected on the document D on the platen 2 is further reflected on 
the aforesaid first mirror 5, the second mirror 7 and on the third mirror 
8 and then is led through the primary lens 10 and fourth mirror 11 onto 
the photoreceptor drum 20 as an image carrier through the slit S provided 
near the document surface. 
On the copying machine having such optical system, the exposure lamp 4 is 
used as a light projector in the present example and there is provided on 
the close side of the primary lens 10 the color sensor 21 (e.g., 
semiconductor color sensor PD-150 . PD-150, commercialized by Sharp Co., 
Ltd. in Japan) to which the reflected light from the colored portion 
(e.g., yellow is desirable because it is not sensitive to the 
photoreceptor like Se (Selenium, Selenium alloy) and others but it can be 
detected by the color sensor) on aforesaid document-holding surface 3a is 
projected. 
Referring to FIG. 3, the circuit from the output of the color sensor 21 as 
a detecting element that detects the colored portion will be explained as 
follows. 
In FIG. 3, 22 is a color sensor unit arranged at the location corresponding 
to the document size to be detected, 23 is a binary level discriminant 
circuit and 24 is a control section. 
The outputs of two photodiodes PD 1 and PD 2 contained in the color sensor 
21 whose spectral-response characteristics are different each other are 
logarithmically compressed by the color sensor unit 22 through the 
logarithmic amplifying circuits LA 1 and LA 2 respectively and when the 
compressed one is inputted in the subtracting circuit SUB, the voltage 
V.sub.0 whose degree is independent of the intensity of the incident light 
and is proportional to the detection wavelength. Namely, V.sub.0 is in a 
relation of V.sub.0 .varies.(log I.sub.sc2 -log I.sub.cs1)=log(I.sub.sc2 
/I.sub.sc1) [where, I.sub.sc1 and I.sub.sc2 are output current of 
photodiodes PD 1 and PD 2 respectively]. 
The binary level discriminant circuit 23 receives from the color sensor 
unit 22 the voltage V.sub.0 whose degree is proportional to the detection 
wavelength and detects whether the voltage V.sub.0 is caused by the light 
having the specific wavelength corresponding to the color of aforesaid 
colored portion pouring into the color sensor. Namely, in the binary level 
discriminant circuit 23, the output voltage V.sub.0 of the color sensor 
unit 22 is first fed into (-) input terminal of the comparison amplifier 
CA 1 and into (+) input terminal of the comparison amplifier CA 2 and then 
on CA 1, the comparison is made with a reference voltage V.sub.1 which is 
inputted in (+) input terminal and is slightly lower than the voltage 
corresponding to aforesaid specific wavelength relating to fixed color and 
on CA 2, the comparison is made with a reference voltage V.sub.2 which is 
fed in (-) input terminal and is slightly higher than the voltage 
corresponding to the specific wavelength and CA 1 generates high level 
signals under the condition of V.sub.0 &lt;V.sub.1 and generates low level 
signals under the condition of V.sub.0 &gt;V.sub.1 and then CA 2 generates 
low level signals under the condition of V.sub.0 &lt;V.sub.2 (where, V.sub.1 
&lt;V.sub.2) and generates high level signals under the condition of V.sub.0 
&gt;V.sub.2. The output signals of the comparison amplifier CA 1 and CA 2 as 
mentioned above are processed in the transistor circuit and then are fed 
into the transistor. transistor logical circuit TTL and TTL generates low 
level signals when V.sub.0 is in a condition of V.sub.1 &lt;V.sub.0 &lt;V.sub.2 
and it generates high level signals when V.sub.0 is in a condition of 
V.sub.0 &lt;V.sub.1 or V.sub.0 &gt;V.sub.2 and therefore the binary level 
discriminant circuit 23 detects the existence of the incidence of the 
light having the specific wavelength against the color sensor 21. 
The relation between the input and the output on the aforesaid binary level 
discriminant circuit is shown in Table 1. 
TABLE 1 
______________________________________ 
input 
voltage CA 1 CA 2 TTL TTL TTL 
(V.sub.0) output output input 2 
input 2 
output 
______________________________________ 
V.sub.0 &lt; V.sub.1 
H L L H H 
V.sub.1 &lt; V.sub.0 &lt; V.sub.2 
L L H H L 
V.sub.0 &gt; V.sub.2 
L H H L H 
______________________________________ 
(note) 
H represents high level signals and 
L represents low level signals. 
Since the inverter is interposed between the output side of TTL and the 
input side of the control section 24, the signal from the colored portion 
is fed into the control section 24 as a high level (convex upward) pulse 
signal. On the control section 24, as mentioned above, the detection of 
document size is made by the comparison between the information stored 
previously and the number of lines (number of pulses) on the colored 
portion. 
FIG. 4 is a time chart showing the relation between the lighting of the 
exposure lamp 4 and the input signal obtained through the color sensor 21 
into the control section corresponding to the colored portion, and it 
shows the state in which the document with B5 size is copied. 
For example, when the document D with B5 size is placed on the platen 2 and 
if the copy button is pressed, the exposure lamp 4 which doubles as a 
light-projecting lamp is lit and optical scanning is made. The exposure 
lamp 4 illuminates the platen 2 and the light reflected therefrom passes 
through the slit S and then is reflected on the first mirror 5, second 
mirror 7 and third mirror 8 and then is led to the color sensor 21. The 
exposure lamp 4 which doubles as a light-projecting lamp is moved in the 
direction X first and thereby irradiates the document D with B5 size and 
then irradiates the document-holding surface 3a of the platen cover 3 
which is not covered by the document. While the document-holding surface 
3a is being irradiated, three lines signal on the colored portion is 
obtained on the color sensor 21 when the document size is B5. 
Since the colored portion is of the striped pattern in the direction of 
scanning for document reading as shown in FIG. 1, signals of pulse 
waveform convex upward corresponding to three lines of colored portions 
are obtained when the document size is B5 (as shown in FIG. 4 - 2). 
Likewise, the signals of colored portions in two lines for A4 size, one 
line for B4 size and 0 lines for A3 size are obtained respectively. 
On the circuit shown in FIG. 3 or the like, therefore, the relation between 
the number of lines of colored portions and the document size mentioned 
above is previousely stored in the control section of the copying machine. 
And in the control section 24, the pulses corresponding to aforesaid 
colored portions which are convex upward are counted and the value thus 
counted is compared with a value stored as mentioned above and 
corresponding to the document size, thus the signal showing the 
corresponding document size is generated. 
When the size-change such as an enlargement or a reduction is made, the 
relation between the document size to be changed and the size of the 
papers to be supplied can be stored for supplying the paper of pertinent 
size. 
In the present example, incidentally, an explanation has been made, 
referring to the example shown in FIG. 2, on a copying machine wherein the 
platen is stationary while the optical system for copying travels for 
document scanning but the present invention is not limited to this and the 
present invention may be applied to a copying machine wherein the optical 
system for copying is stationary and the platen travels for document 
scanning if the document can be scanned on the copying machine. The 
present invention may also be naturally applied to a copying machine 
wherein a solid image pickup element such as CCD and others is employed. 
Even when the platen travels, the detection of the document size is made 
by the color sensor arranged near the exposure lamp. 
Though the exposure lamp is used also as a light-projecting device in the 
present example, such combined use is naturally unnecessary and they may 
be provided separately. 
In the present example explained above, various sizes of documents can be 
detected by only one detecting element used and it has proved to provide 
an excellent document size-detecting device of a copying machine wherein 
the circuit structure is simple and the reliability for detection of the 
document size has been improved. 
FIG. 5 is a circuit diagram to be connected to the control section 25 and 
is an example of the circuit that detects the reflected light from the 
colored portion and detects the document size based on the detection of 
the reflected light. 
In FIG. 5, 22 represents the color sensor unit arranged at the location 
corresponding to the document size to be detected, 23 is a binary level 
discrimination circuit and 25 is a control section. 
The outputs of two photodiodes PD 1 and PD 2 contained in the color sensor 
21 whose spectral-response characteristics are different each other are 
logarithmically compressed by the color sensor 22 through the logarithmic 
amplifying circuits LA 1 and LA 2 respectively and when the compressed one 
is inputted in the subtracting circuit SUB, the voltage V.sub.0 whose 
degree is independent of the intensity of the incident light and is 
proportional to the detection wavelength. Namely, V.sub.0 is in a relation 
of V.sub.0 .varies.(log I.sub.sc2 -log I.sub.sc1)=log(I.sub.sc2 
/I.sub.sc1) [where, I.sub.sc1 and I.sub.sc2 are output current of 
photodiodes PD 1 and PD 2 respectively]. 
The binary level discriminant circuit 23 receives from the color sensor 
unit 22 the voltage V.sub.0 whose degree is proportional to the detection 
wavelength and detects whether the voltage V.sub.0 is caused by the light 
having the specific wavelength corresponding to the color of aforesaid 
colored portion pouring into the color sensor. Namely, in the binary level 
discriminant circuit 23, the output voltage V.sub.0 of the color sensor 
unit 22 is first fed into (-) input terminal of the comparison amplifier 
CA 1 and into (+) input terminal of the comparison amplifier CA 2 and then 
on CA 1, the comparison is made with a reference voltage V.sub.1 which is 
inputted in (+) input terminal and is slightly lower than the voltage 
corresponding to aforesaid specific wavelength and on CA 2, the comparison 
is made with a reference voltage V.sub.2 which is fed in (-) input 
terminal and is slightly higher than the voltage corresponding to the 
specific wavelength and CA 1 generates high level signals under the 
condition of V.sub.0 &lt;V.sub.1 and generates low level signals under the 
condition of V.sub.0 &gt;V.sub.1 and then CA 2 generates low level signals 
under the condition of V.sub.0 &lt;V.sub.2 and generates high level signals 
under the condition of V.sub.0 &gt;V.sub.2. The output signals of the 
comparison amplifier CA 1 and CA 2 as mentioned above are processed in the 
transistor circuit and then are fed into the transistor. Transistor 
logical circuit TTL and TTL generates low level signals when V.sub.0 is in 
a condition of V.sub.1 &lt;V.sub.0 &lt;V.sub.2 and it generates high level 
signals when V.sub.0 is in a condition of V.sub.0 &lt;V.sub.1 or V.sub.0 
&gt;V.sub.2 and therefore discriminant cirouit 23 detects the existence of 
the incidence of the light having the specific wavelength against the 
color sensor 21. 
The relation between the input and the output on the aforesaid binary level 
discriminant circuit is shown in Table 1. 
Since the inverter is interposed between the output side of TTL and the 
input side of the control section 25, the signal from the colored portion 
is fed into the control section 25 as a high level pulse signal. 
Since the colored portion is of the striped pattern in the direction of 
scanning for document reading as shown in FIG. 1, signals of three lines 
of colored portions are obtained when the document size is B5. Likewise, 
the signals of colored portions in two lines for A4 size, one line for B4 
size and 0 lines for A3 size are obtained respectively. 
FIG. 6 is a time chart showing the relation between the lighting of the 
exposure lamp 4 and input signals as well as encoder pulses obtained 
through the color sensor 21 into the control section and it shows the 
state in which the document with B5 size is copied. 
The output a from TTL through the invertor and encoder pulses with a 
constant frequency or clock pulses b are fed into the control section 25. 
When the detecting system of the present invention detects the level of 
the colored portion, namely, when the output a is H, the control section 
25 of the main body detects the encoder pulses of the main body. When the 
output a becomes L, the detection of the encoder pulses is discontinued. 
This signal corresponds to output c signal. Since the width H of the 
colored portion and the scanning speed of the exposure lamp 4 are known 
previously, the colored portion is surely proven by the number of encoder 
pulses fed and corresponds to the width of the colored portion. 
For example, when the width H of the colored portion is 15 mm, the scanning 
speed of the exposure lamp 4 is 170 mm/s, one pulse period of encoder 
pulse is 10 msec and the slit S of the optical system is 8 mm, the 
distance during which the reflected light from the colored portion passes 
through the entire width of the slit corresponds to the 7 mm in accordance 
with scanning direction of the exposure lamp, and the distance during 
which the reflected light from the colored portion passes through the half 
or more of the width of the slit corresponds to 15 mm in accordance with 
direction and for both cases, the time required for them is about 40 msec 
and 90 msec respectively which relate to 4 pulses and 9 pulses 
respectively. These are set up to 3-10 pulses considering the margin. 
Therefore, if the output a is H during the period between the minimum of 3 
pulses and the maximum of 10 pulses, this can be judged as a colored 
portion. In the case of 3 pulses or less than that, it will be judged as a 
noise and in the case of 10 pulses or more than that, it will be judged as 
a document whose color is akin to that of colored portion. So, when the 
light corresponding to the reflected light from the colored portion 
continues for the period of 10 pulses or more of encoder pulse, the method 
for detecting the document size may be the one wherein the pulses 
generated continuously are counted and the continuing time for the number 
of pulses thus counted detects the size in the scanning direction. 
Since the relation between the number of lines of colored portion and the 
document size is previously stored in the control section (not 
illustrated) of the main body of copying machine like the case, for 
example, that three lines of the colored portion represent B5 size, when 
the c signal output from the control section 25 in FIG. 5 is generated in 
a way shown in FIG. 6, the detection of the document size is made by the 
judgment of the number of pulses corresponding to the time frame for the 
number of lines of colored portion. 
Further, when the size-change such as an enlargement or a reduction is 
made, the relation between the document size to be changed and the size of 
the paper to be supplied stored in the control section 25 enables the 
pertinent size paper to be supplied. 
In the present example, the number of lines of the colored portion or the 
time frame corresponding to the number of lines is detected and thereby 
the document size is detected, but the present invention is not limited to 
this. It is possible, utilizing the encoder pulse, to count the total 
pulse number generated for the period from copy start ON up to the point 
when the detection of the colored portion is first started and to compare 
the total pulse number with the pulse number which is stored previously 
for the detection of the document size, which is included in the present 
invention. 
In the present example, the explanation was made, referring to the example 
shown in FIG. 2, on the copying machine wherein the platen is stationary 
and the optical system for copying travels for the scanning of document 
but the present invention is not limited to this. The present invention 
may further be applied to the copying machine wherein the optical system 
for copying is stationary and the platen travels for the scanning of 
document. It may further be applied naturally to the copying machine 
wherein a solid image pickup element such as CCD or the like is employed. 
Even in the case of a movable platen, the detection of document size is 
made with a color sensor provided near the exposure lamp. 
Though the exposure lamp is used also as a light-projecting device in the 
present example, such combined use is naturally unnecessary and they may 
be provided separately. 
In the present example explained above, various sizes of documents can be 
detected by only one detecting element used and the circuit structure 
proved to be simple. Further, the level of colored portion as well as the 
width thereof can be detected and documents of all colors can be detected 
while in the past, the document with a color that is akin to that of the 
colored portion was not able to be detected. Thus, there has been provided 
an excellent document size-detecting device of a copying machine wherein 
the reliability for detection of the document size has been improved. 
Further, as the third embodiment, it is possible to provide many colored 
portions on the document-holding surface of the platen cover 3 with a 
constant interval in the direction of scanning and to count the number of 
colored lines which are not covered by the document when detecting the 
document size and to compare the counted number with the correspondence 
between the document size and counted number which is stored in the 
control section previously, in order to detect the document size.