Self-running scanner for optically reading images

Provided is a self-running type scanner including a movable scanner unit and a running guiding and assisting plate mounting the scanner unit for guiding running of the scanner unit. The movable scanner unit includes an illuminating light source, a step motor for running the scanner unit, an inage sensor, a controller for controlling provision of image information and running of the scanner unit, and wheels to which the rotation force of the motor is transmitted. The running assisting plate includes guides engaging with the wheels, a light transmitting area, a white area around the light transmitting area, a black area surrounding the white area and the light transmitting area, and timing marks indicative of the position for starting reading.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an image scanner and, more specifically, 
to an improvement of a scanner structured such that an object such as an 
original is fixedly placed and scanned by moving a scanner including an 
illuminating light source, a photodetector and the like to provide image 
information of the object. 
2. Description of the Background Art 
There has been a strong demand of treating image information in the same 
manner as in treating document information in various fields including the 
field of office automation. A scanner is one of the apparatuses provided 
to meet such a demand. The scanner is structured such that an object such 
as an original is illuminated by light from an illuminating light source 
and the light reflected from the object is detected by a one dimensional 
image sensor comprising CCDs (Charge Coupled Devices) to provide image 
information of the object. One type of such scanner is called a 
self-running type scanner in which an object such as an original is 
fixedly placed and a scanner portion is moved for scanning the object by 
using the light from the illuminating light source. 
FIG. 1 schematically shows a whole structure of a conventional self-running 
type scanner. Referring to FIG. 1, the conventional self-running type 
scanner comprises a scanner unit 1 for illuminating an object such as an 
original (not shown) with light having a prescribed wavelength and for 
detecting light reflected from the object to provide image information of 
the object, and a driving portion 2 for driving running of the scanner 
unit 1. The scanner unit 1 responds through a wire 3 to the rotation of a 
pulse motor 4 included in the driving portion 2, to be moved along the Y 
direction. The rotation of the pulse motor 4 included in the driving 
portion 2 is transmitted to the wire 3 through a pulley 5b. A pulley 5a is 
similarly provided at another portion of the wire 3 so as to smoothly move 
the scanner unit 1 along the Y ,direction. As the scanner unit 1 runs in 
the Y direction, the illuminating light from the illuminating light source 
included in the scanner unit 1 illuminates an object such as an original 
(hereinafter simply referred to as an object) while scanning the same, so 
that the desired image information of the object can be provided. 
The scanner unit 1 and the driving portion 2 are contained in a scanner 
body 6. A scanner upper lid 7 is provided on the scanner body 6 for 
sealing the scanner unit 1, the driving portion 2 and so on, so as to 
prevent contamination due to dust and the like from outside. 
A plate 8 formed of a transparent material for transmitting the 
illuminating light from the illuminating light source included in the 
scanner unit 1 and the light reflected from the object is provided at a 
prescribed region of the scanner body 6. The plate 8 is formed of a 
material such as acryl, glass or the like which is transparent to the 
illuminating light from the illuminating light source therethrough. 
In addition, a white balance sheet 9 for providing a white level reference 
of the light reflected from the object is provided at a prescribed 
position of the scanner body 6. The scanner unit 1 scans the white balance 
sheet 9 to detect the light reflected from the white balance sheet 9. The 
detected level of the reflected light is used as the reference level to 
the white level of the light reflected from the, object during scanning. 
This is a measure to prevent an erroneous reading caused by a change in 
intensity of the reflected light associated with changes of the 
environment such as a change in intensity of the illuminating light from 
the light source. 
FIG. 2 schematically shows an internal structure of the scanner unit shown 
in FIG. 1. Referring to FIG. 2, the scanner unit comprises an illuminating 
light source 10 for illuminating an object, reflecting mirrors 11a, 11b, 
11c and 11d reflecting the light reflected from the object (including the 
white balance sheet) and providing an optical path of the reflected light, 
and a lens 12 for receiving and focusing the reflected light from the 
reflecting mirror 11d onto a one dimensional image sensor 13 consisting 
of, for example, CCDs (Charge Coupled Devices). The one dimensional image 
sensor 13 converts the applied optical signals into electric signals to 
transmit the same to an image information processing apparatus through a 
path, not shown. 
In the above described structure, when the scanner unit 1 scans the object 
along the Y direction, the scanning of the object in the X direction is 
carried out by the one dimensional image sensor 13. In such a self-running 
type scanner, the object is fixedly placed and illuminated by the light 
from the illuminating light source 10 and the illuminating light from the 
object is reflected by the reflecting mirrors 11a through 11d to be 
introduced to the one dimensional image sensor 13 through the lens 12 for 
image formation, so that the object can be scanned in both X and Y 
directions, providing desired image information of the object. 
In the above described structure of the conventional self-running type 
scanner, the scanner unit 1 and the driving portion 2 for driving the 
running of the scanner unit 1 are separately provided, and the scanner 
unit 1, the driving portion 2 and the scanner driving wire 3 must be 
contained in a scanner body 6. In addition, the scanner body and the 
scanner upper lid are both of a separate type structure, so that the 
number of components of the units constituting the conventional 
self-running type scanner becomes large and the apparatus itself becomes 
complicated, preventing reduction in size of the apparatus. Since the 
apparatus comprises a large number of parts, it takes much time to 
assemble the self-running type scanner. The larger number of parts and the 
long time required for the assembly prevent provision of an inexpensive 
self-running type scanner. 
A structure of a scanner unit having a rotary motor attached integrally 
thereto is disclosed in Japanese Patent Laying Open No. 61-232764. In this 
prior art, a flanged roller which is in contact with a guiding slide rod 
is arranged at a tip end portion of an output axis of the rotary motor, 
and a fixed axis having a V grooved bearing in contact with another slide 
rod is provided at a tip end of the other end of the unit. The scanner 
unit moves along the slide rods by the rotation of the output axis of the 
rotary motor. 
A self-scanning type (self-running type) copying apparatus in which an 
original reading mechanism is moved by rotating a driving roller by means 
of a microstep motor is disclosed in Japanese Patent Laying Open No. 
58-111476. In this copying apparatus, feeding of recording paper and the 
scanning of the original are both carried out by the driving of the same 
step motor. No guiding means for moving the copying apparatus is provided 
in this prior art. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide an improved self-running 
type scanner eliminating drawbacks of the conventional self-running type 
scanner. 
Another object of the present invention is to provide an inexpensive 
self-running type scanner having a simple structure with reduced number of 
parts. 
A further object of the present invention is to provide a self-running type 
scanner having a simple structure which can read information exactly. 
A self-running type scanner in accordance with the present invention 
comprises a scanner unit and a scanner driving portion formed integrally, 
and running assisting means for guiding and assisting the running of the 
scanner. 
More specifically, the self-running type scanner of the present invention 
comprises a movable scanner portion including an illuminating light 
source, a photodetector for detecting reflected light, a running driving 
portion, and controlling means for controlling operation of the driving 
portion in accordance with the information detected by the photodetector, 
and means for guiding and assisting running of the scanner portion 
including means for guiding the running of the scanner portion and means 
indicative of a position at which reading of an object of the scanner 
portion starts. 
Preferably, the guiding assisting means comprises a light transmitting area 
for defining an object reading area of the scanner portion and a white 
area for providing reference of white level in reading images of the 
object. 
In the self-running type scanner of the present invention, scanner running 
driving means is integrally provided on the scanner portion, so that a 
simple structure can be realized, and accordingly, an inexpensive 
self-running type scanner can be provided as the number of parts and the 
steps for manufacturing can be reduced. 
Running guiding means, the reading area defining area, means for indicating 
reading start position and the white area provided on the running 
assisting means enable accurate running of the scanner portion through the 
controlling means provided on the scanner portion and realize accurate 
reading of images. 
The foregoing and other objects, features, aspects and advantages of the 
present invention will become more apparent from the following detailed 
description of the present invention when taken in conjunction with the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 3 schematically shows a whole structure of the self-running type 
scanner in accordance with one embodiment of the present invention. 
Referring to FIG. 3, the self-running type scanner of one embodiment of 
the present invention comprises a scanner portion 1' for illuminating an 
object while scanning the same for providing image information of the 
object, and a running assisting plate 23 for guiding and assisting the 
running of the scanner portion 1'. The scanner portion 1' comprises an 
illuminating light source 10 for emitting light of a prescribed 
wavelength; reflecting mirrors 11a through 11d which reflect light 
reflected from objects (including an original and the like and the 
assisting plate 23) illuminated by the light emitted from the light source 
10 for providing optical path of the reflected light; a lens 12 for 
condensing or converging light from the reflecting mirror 11d to form 
images on an image sensor 13; a one dimensional image sensor 13 for 
converting image information of the object applied through the lens 12 for 
into electric signals; and a controlling apparatus 20 receiving image 
information from the one dimensional image sensor 13 to provide desired 
image information and control the running of the scanner portion 1'. 
The controlling apparatus 20 transmits signals to external apparatuses such 
as an image processing apparatus through a cable 25 and receives control 
signals such as an image information reading instructing signal from the 
external apparatuses. The cable 25 is taken outside from the scanner 
portion 1' through an upper cabinet projecting portion 24 provided on an 
upper portion of the upper cabinet 15 housing the scanner portion 1'. 
Front wheels 21 and rear wheels 22 for running and driving the scanner 
portion 1' are also provided. The control of the operation of the front 
and rear wheels 21 and 22 is carried out by the controlling apparatus 20. 
The running assisting plate 23 comprises a front stopper 31 and a rear 
stopper 32 for preventing possible slippage of the scanner portion 1' from 
the running assisting plate 23 which may lead the scanner portion 1' to be 
dropped and damaged. The running assisting plate 23 serves not only to 
guide and assist the running of the scanner portion 1' but also to fixedly 
set the reading area for the scanner portion 1' to read image information 
of the object. 
FIG. 4 shows more specific structure of the running assisting plate. 
Referring to FIG. 4, the running assisting plate 23 comprises front and 
rear stoppers 31 and 32, guiding areas 33a and 33b, and a light 
transmitting area 34. 
The front and rear stoppers 31 and 32 are provided at the front portion and 
rear portion of the running assisting plate 23, respectively, along the 
direction of running (Y direction) of the scanner 1'. 
The guiding areas 33a and 33b are respectively provided at prescribed 
positions on both sides of the running assisting plate 23 along the X 
direction. The front and rear wheels 21 and 22 provided on the scanner 
portion 1' engage with the guiding areas 33a and 33b. Consequently, the 
running of the scanner portion 1' is guided by the guiding areas 33a and 
33b. 
The light transmitting area 34 transmits illuminating light from the 
scanner portion 1' and the light reflected from the object, and it fixedly 
sets the reading area of the scanner portion 1'. The light transmitting 
area 34 is provided by cutting the running assisting plate 23 or by using 
a transparent material (acryl, glass or the like). The light transmitting 
area 34 (A) is larger than an effective reading area B (in which image 
information of the object is actually read) for reading the object, as 
shown in FIG. 4. 
A white area 35 is provided along the X and Y directions of the light 
transmitting area 34 for applying a reference value of white level in 
reading images of the object and for giving information for moving the 
scanner portion 1' to the reading start position when the image reading of 
the object is to be started. Timing marks 36 and 37 each consisting of a 
black area having a width of 1 mm and a length of 2 mm are provided at 
prescribed positions of the white area 35. The timing marks 36 and 37 give 
information on reading start positions in the Y and X directions, 
respectively. The white area 35 has a width w.sub.4 of 4 mm, for example, 
and it is formed to be larger than the length of the timing marks 36 and 
than the width of the timing mark 37, respectively. A black area D is 
provided around the outer periphery of the white region 35 so as to make 
clear the white level of the white area 35 and to prevent unnecessary 
reflection of light. 
The shape of the guiding areas 33a and 33b is determined corresponding to 
to the shape of the front and rear wheels 21 and 22 provided on the 
scanner portion 1'. Alternatively, the shape of the front and rear wheels 
21 and 22 is determined corresponding to the shape of the guiding areas 
33a and 33b. 
As shown in FIG. 5A, if the guiding area 33 is formed of a guiding groove 
40, the wheel provided on the scanner portion 1' (front and rear wheels) 
has a projecting portion 41 engaging with the guiding groove 40. 
If the guiding area 33 is formed of a guiding projecting portion 42 as 
shown in FIG. 5B, the wheel (front and rear wheels) is structured to have 
a groove portion 43 engaging with the guiding projecting portion 42. 
If the guiding area 33 is formed of a guiding groove 40 as shown in FIG. 
5C, the wheel 44 having one side made parallel to the depth direction of 
the guiding groove 40 and the other side made oblique to the depth 
direction of the groove 40 may be used. In that case, a projecting portion 
defined by the parallel portion and the oblique portion of the wheel 44 is 
engaged with the guiding groove 40. 
The front and rear wheels 21 and 22 provided on the scanner portion 1' are 
attached to have a predetermined angle about the moving direction (Y) of 
the scanner portion 1', as shown in FIG. 6. Consequently, if the front and 
rear wheels 21 and 22 are both structured as shown in FIG. 5A and the 
guiding groove 33 is formed as the guiding groove 40, the front and rear 
wheels 21a, 21b, 22a and 22b run along and in contact with - (minus) side 
end portion of the guiding groove 40 in the X direction when the scanner 
portion 1' proceeds (+ direction in the Y direction), while the front and 
rear wheels 21a, 21b and 22a and 22b run along and in contact with + side 
end portion in the X direction of the guiding groove 40 when the scanner 
portion 1' moves rearward (- direction of Y direction shown in FIG. 6). 
Therefore, the stable running of the scanner portion 1' is achieved 
without skews such as fluctuation in the left and right direction and the 
unevenness in the running velocity. The front wheels 21a and 22b are 
supported by an axis 45a. The rear wheels 22a and 22b are supported an 
axis 45b. A first gear 48 is integrally provided with the axis 45b 
supporting the rear wheels 21a and 22b. A second gear 47 is provided to be 
engaged with the first gear 48. The second gear 47 is rotary driven by a 
pulse motor 46. Therefore, the rear wheels 22a and 22b are driven through 
the gears 47 and 48 in response to the rotation of the pulse motor 46, 
whereby the scanner portion 1' runs in the desired direction. 
In association with the attachment of the wheels shown in FIG. 6, the 
scanner portion 1' can be moved in contact with one area of the guiding 
areas when the scanner portion 1' moves forward and rearward, by attaching 
the wheels at a prescribed angle about the direction of movement of the 
scanner portion 1', even when the wheels have the shape shown in FIG. 5B 
or 5C. Therefore, the scanner portion 1' can be moved without skew as in 
the above described case. 
The cable 25 for exchanging signals with the control apparatus in the 
scanner portion 1' is taken out from a projecting area 24 provided on the 
upper portion, of an upper cabinet of the scanner portion 1' for the 
following reason. Namely, as is apparent from the comparison of FIGS. 7A 
and 7B, the distance l1 (FIG. 7A) required for connecting the cable 25 to 
another apparatus or to the running assisting plate when the cable is 
taken out from the projection 24 on the upper portion of the scanner 
portion 1' in this embodiment of the present invention can be made far 
longer than the distance l2 (FIG. 7B) required for connecting the cable 25 
to an apparatus such as the running assisting plate when the cable 25 is 
taken out from the side portion of the scanner portion 1' through a taking 
area 24'. Consequently, undesirable influences to the running of the 
scanner portion 1' derived from friction of the cable 25 or the like can 
be removed, and therefore the scanner portion 1' can be moved more stably. 
FIG. 8 is a block diagram showing an electrical structure of the scanner 
portion in the self-running type scanner in accordance with one embodiment 
of the present invention. Referring to FIG. 9, portions corresponding the 
structure of FIG. 3 are designated by the same reference numerals. 
Referring to FIG. 8, the scanner portion comprises a CPU 50 formed of one 
chip, for example, for controlling various operations of the scanner 
portion. 
The CPU 50 outputs control signals .phi..sub.T, .phi..sub.1, .phi..sub.2, 
.phi..sub.R and .phi..sub.SH for applying operation timing of the one 
dimensional image sensor 13 consisting of, for example, CCDs to the image 
sensor 13 and receives image information .upsilon..sub.0 from the image 
sensor 13 at an A/D terminal thereof. The signal .phi..sub.T gives the 
timing for starting scanning of the image sensor 13. Namely, in response 
to the signal .phi..sub.T, the information of the CCD cells in the image 
sensor 13 is transferred to an analog shift register (not shown). Clock 
signals .phi..sub.1 and .phi.2 are two phase complementary clock signals 
which do not overlap with each other, applying data transfer timing in the 
analog shift register. Namely, the CCD cell information of the image 
sensor 13 is successively transmitted through the analog shift register in 
response to the clock signals .phi.1 and .phi.2. The signal .phi..sub.R 
applies data output timing of the image sensor 13. The information of the 
image sensor 13 is successively outputted in response to the signal 
.phi..sub.R. The signal .phi..sub.SH is a signal for applying timing of 
sampling/holding the CCD cell information outputted in response to the 
signal .phi..sub.R. Namely, each piece of information from the CCD cell is 
sampled/held in response to the signal .phi..sub.SH to be outputted as the 
output signal .upsilon..sub.0 from the image sensor 13. The relation 
between timings of the control signals applied to the CCD image sensor 13 
and the output signal from the image sensor 13 are shown in FIG. 9. FIG. 9 
shows a case in which the image sensor 13 comprises 576 CCD cells, as an 
example. 
The structure comprising 576 CCD cells is determined to satisfy the 
following conditions. Namely, assuming that the reading area (area B in 
FIG. 4) of the scanner portion has a width w.sub.1 of 64 mm and a length 
of 100 mm, the image of the object is resolved with the resolution of 8 mm 
in Y and X directions, respectively, by the scanner portion. In order to 
read the white area 35 provided outside of the area B of FIG. 4, the CCD 
image sensor comprises (64+8).times.8=576 CCD cells, so that an area wider 
than the effective reading width w.sub.1 of 64 mm by 8 mm (w.sub.5 
+w.sub.6) can be read. 
The CPU 50 receives +5 V through the cable 25 as the operational power 
supply. The CPU 50 outputs a STATE signal indicative of the reading of 
image information of the object, a signal SYNC indicative of the starting 
position of one line of the image information to be transmitted, the image 
information DATA from the CCD and the clock signal CLOCK for giving the 
data transmitting timing, in order to transmit the output from the image 
sensor 13 to external apparatuses (host computer, image processing 
apparatus and so on). The image information DATA outputted from the CPU 50 
comprises only the image information of the object read in the effective 
reading area (the area B in FIG. 4), and not the image information of the 
white area 35 or the like provided on the running assisting plate 23. The 
timing relation between the signals outputted from the CPU 50 is shown in 
FIG. 10. 
A pulse motor driver 51 for driving the pulse motor 46 is provided for 
driving the running of the scanner portion 1'. The pulse motor driver 51 
receives motor rotation instructing signals .phi..sub.A, .phi.-.sub.A, 
.phi..sub.B, and .phi.-.sub.B from the CPU 50, amplifies the level thereof 
to be sufficient for driving the pulse motor 46 and transmits control 
signals .phi..sub.A, .phi.-.sub.A, .phi..sub.B and .phi.-.sub.B as well as 
the supply voltage +5 V to the pulse motor 46. A two-phase-on type four 
phase pulse motor is used as the pulse motor 46, and it is stopped or 
rotated in either the negative direction or the positive direction by the 
combination of the signal levels of the control signals .phi..sub.A, 
.phi.-.sub.A .phi..sub.B and .phi.-.sub.B. The pulse motor 46 makes the 
scanner portion 1' run by 1/8 mm per 1 step in response to the control 
signal from the pulse motor driver 51. 
A lighting apparatus 52 is provided for lighting the illuminating light 
source 10, which apparatus applies complementary high voltage signals 
V.sub.R and V.sub.L to the illuminating light source 10 in response to a 
lighting instructing signal FLON from the CPU 50. The illuminating light 
source 10 comprises, for example, a fluorescent lamp which is turned on by 
the application of the complementary lighting signals V.sub.R and V.sub.L, 
which in turn sets the lamp in the same state as is connected to an 
alternating power supply. 
The CPU 50 has a memory device consisting of a RAM (Random Access Memory) 
as will be described later (see FIG. 13). The slice level which is the 
reference for determining whether the read image information is white or 
black is stored in the memory device, and the CPU determines whether the 
read image information is white or black dependent on the stored slice 
level and outputs the result as the output data DATA through the cable 25. 
The operation of the self-running type scanner in accordance with one 
embodiment of the present invention will be described in the following 
with reference to FIGS. 11 through 13. 
The scanner portion 1' is set such that the reading line (the area 
illuminated by the light from the illuminating light source 10, and the 
reflected light from the object reaches the image sensor 13 to be read, 
that is, one line in the X direction in FIG. 4) is at an appropriate 
position of the light transmitting area 34 of the running assisting plate 
23. 
(1) When an object reading instruction is provided from an external 
apparatus, +5 V is applied through the cable 25 to the scanner unit 1', so 
that the CPU 50 starts its operation. In response to the application of +5 
V, the CPU 50 resets to 0 in a second RAM area, that is, memory addresses 
128 to 703 of the memory device included therein. At this time, the 
lighting instruction signal FLON is still in an inactive state, so that 
the lighting apparatus 52 does not operate and the illuminating light 
source 10 formed of a fluorescent lamp does not emit light. 
(2) The CPU 50 applies various controlling signals to the image sensor 13 
to read image information from the image sensor 13. The image sensor 
comprises 576 CCD cells and the CPU 50 receives CCD cell outputs from the 
first to 576th cells (the number of the CCD cells increases from the side 
of the white area 35 to the + direction in the X direction shown in FIG. 
4) to A/D convert (analog-digital convert) the same. During A/D 
conversion, when the CCD cell output is 5 V, the CPU 50 sets the output to 
255 and when the output is 0 V, the CPU 50 set the output to 0. The output 
value between 0 to 5 V is A/D converted stepwise, each step being about 
19.6 mV. Namely, the range from 0 V to 5 V is divided into 256 levels, and 
the CCD cell output is represented by one of these levels. The 256 levels 
are represented in 8 bit binary number. Since the illuminating light 
source 10 does not emit light, the resultant 576 CCD cell outputs after 
the AD conversion are all at about 4 V, which corresponds to a black 
level. The black level data are stored in the memory addresses 704 to 1279 
of a third RAM area of the memory device included in the CPU 50, as VBL1, 
VBL2, . . . VBL576. 
(3) After the black level data are stored in the memory device, the 
lighting instruction signal FLON is generated and the lighting apparatus 
52 is activated to turn on the illuminating light source 10. 
(4) Thereafter, the CPU 50 checks the outputs from the first to 64th CCD 
cells out of the outputs from the image sensor 13. The white level (no 
more than 3 V) w.sub.4 of about 4 mm in width corresponding to the white 
area 35 can be found in the outputs from the first to 64th CCD cells. 
Actually, the outputs from the first to 32nd CCD cells are at the white 
level as shown in FIG. 11A, for example. More specifically, 8.times.4=32 
CCD cells exist in the white area having the width of about 4 mm, as the 
image sensor 13 has the resolution of 8/ mm in the X direction. Therefore, 
if the first CCD cell corresponds to the end portion of the white area, 
the outputs from the first to 32nd CCD cells will be the white level 
outputs. 
(5) When the white level of the white area having a width of 4 mm is found, 
the CPU 50 determines that the scanner portion 1' is not positioned at the 
reading start position, and it outputs a control signal to the pulse motor 
driver 51 of the scanner portion 1' to drive the pulse motor 46, so that 
the scanner portion 1' is moved in the positive direction in the Y 
direction stepwise, each step Y.sub.1 being 1/8 mm. 
(6) As the scanner portion 1' runs, the X direction timing mark 37 is 
detected at a certain time point, and a black level (no less than 3.5 V) 
having the width, Y.sub.n about 1 mm appears as shown in FIG. 11B in the 
outputs from the first to 32nd CCD cells. After the detection of the X 
direction timing mark 37, the scanner portion 1' is further moved in the 
positive direction in the Y direction by the step of 1/8 mm. Consequently, 
the X direction timing mark 37 disappears and the white level of about 4 
mm in width as shown in FIG. 11A is again found in the outputs from the 
first to 32nd CCD cells. The scanner portion 1' continues to run at the 
step of 1/8 mm. 
(7) As the scanner portion 1' runs, the image sensor 13 comes to scan the 
white area 35 extending in the X direction. Consequently, the outputs from 
the 576 CCD cells of the image sensor 13 all become white level, so that 
the output waveform as shown in FIG. 11D is applied to the CPU 50. In the 
present embodiment, the scanner portion 1' is further moved from this 
point to the + direction in the Y direction by 10 mm to be stopped there. 
Therefore, the area detected by the image sensor 13 corresponds to the 
black area D of the running assisting plate 23 (FIG. 11E). 
(8) Thereafter, the scanner portion 1' starts running in the - direction of 
Y direction under the control of the CPU 50. When the Y direction timing 
mark 36 is scanned as the scanner portion runs, the black level having a 
width of about 2 mm is found in outputs from the first to 32nd CCD cells 
included in the image sensor 13. When the black level corresponding to the 
Y direction timing mark 36 is detected, the CPU 50 stops the running of 
the scanner portion 1'. The output signal of the image sensor 13 at this 
point have a waveform such as that shown in FIG. 11C. 
(9) In response to the detection of the Y direction timing mark, the CPU 50 
AD converts the outputs from the first to 576th CCD cells out of the CCD 
cell outputs from the image sensor 13, calculates average values with the 
signal levels which have been stored in the second RAM area of the memory 
device in the CPU 50, and again stores the average values to the original 
addresses. More specifically, assuming that the signal values of the CCD 
cells after AD conversion are VOW'1, VOW'2, . . . VOW'575 and VOW'576, the 
signal values VOW1, VOW2, . . . VOW576 which have been stored in the 
second RAM area are read to provide average output of each of the cells. 
Namely, the values (VOW1+VOW'1)/2, (VOW2+VOW'2)/2, . . . 
(VOW576+VOW'576)/2 are calculated. The average values are written in the 
corresponding addresses from the memory address 128 to 703 as the new 
white level reference values VOW1, VOW2, . . . VOW576. Since the Y 
direction timing mark 36 has been detected, there is an output signal 
indicative of the black level out of the output signals from the first to 
32nd CCD cells. However, only the 65th to 576th CCD cell outputs are used 
as the information from the effective area for reading images of the 
object, that level has no influence on the actual reading of the image 
information of the object. 
(10) Thereafter, the scanner portion 1' runs in the - direction in the Y 
direction only by a step of 1/8 mm under the control of the CPU 50. The 
waveform v0 of the output signal from the image sensor 13 at this time 
point is shown in FIG. 11c as in the above described case, since the width 
of the Y direction timing mark 36 is about 1 mm shown as Y.sub.n. The CCD 
cell outputs from the image sensor 13 are AD converted in a similar manner 
as described above, and the respective numerical values are provided as 
VOW1", VOW" 2, . . . VOW1" 575 and VOW" 576. The average value between 
them and the white level reference values VOW1, VOW2, . . . VOW3 . . . 
VOW576 which have been calculated by the previous averaging operation are 
calculated. The values provided in this manner are stored as the new 
reference level values VOW1, VOW2, . . . VOW576 in the memory addresses 
128 to 703 in the second RAM area of the memory device in the CPU 50. 
(11) The above described operation is repeated for the entire Y direction 
timing mark (8 lines, 1 mm in width). Consequently, the reference values 
V01, V02, VOW3, . . . VOW575 and VOW 576 stored in the second RAM area of 
the memory addresses 128 to 703 in the memory device of the CPU 50 
represent the average values of the levels in a rectangular area having 
the width of 1 mm and the length l5 of 72 mm, which corresponds to the Y 
direction timing mark 36 in the white area having the width of 4 mm 
extending in the Y direction shown in FIG. 4. Out of these, the outputs 
from the 65th to the 576th CCD cells are used as the CCD cell outputs 
corresponding to the length of 64 mm of the reading area. Since only the 
white levels are detected in this area, the average value of the white 
level in this area is used as the white level reference value in the 
actual reading of the image of the object. Namely, as shown in FIG. 12, 
the output from the first CCD cell in 8 times of scanning of the white 
area, that is, P'1, P.sup.2 1, . . . P.sup.8 1 is averaged and the average 
value is stored in the memory address 128 as the value VOW1. Similarly, 
the average value VOW2 of the outputs P'2, P.sup.2 2, . . . P.sup.8 2 from 
the second CCD cell is stored in the memory address 129. The average value 
VOW512 of the outputs P'576, P.sup.2 576, . . . P.sup.8 576 from the 576th 
CCD cell is stored in the memory address 703. 
The average value of the CCD cell outputs over several lines (8 lines in 
the embodiment) is used as the reference value of the white level in order 
to reduce the influence of dust, unevenness of color and the like. 
(13) Thereafter, the CPU 50 provides a slice level which becomes the 
reference for determining white or black in detecting image information, 
by using the stored reference values VOWi and VBLi. The slice level is 
calculated in the following manner. 
EQU SLICE (N)=[VOW (N)-VBL (N)].times.0.7+0 VBL (N) 
where N=1, 2, 3, . . . 576 
The calculated slice levels are respectively stored in a fourth RAM area, 
i.e., the memory addresses 1280 to 1855 of the memory device. 
(14) Thereafter, the scanner portion 1' runs in the - direction of the Y 
direction to a point where the waveform of the output signal from the 
image sensor 13 changes from that of FIG. 11C to that of FIG. 11D, under 
the control of the CPU 50. The fact that the CCD cell output from the 
image sensor 13 has such a waveform as shown FIG. 11D means that the areas 
scanned by the image sensor 13 are all white areas. When the scanning 
areas of the image sensor 13 all become white, the CPU 50 clears the Y 
address in the memory address 1857 of the memory device to "0" in 
response. Thereafter, as the scanner portion 1' runs in the negative 
direction in the Y direction by 1/8 mm, the CPU 50 increments Y address of 
the memory address 18577 by "1". 
(15) The scanner portion 1' continues to run, and when the waveform of the 
output signal from the image sensor 13 changes from that shown in FIG. 11D 
to that shown in FIG. 11B, it means that the image sensor scans the X 
direction timing mark 37. The CPU 50 stores as the X address in the memory 
address 1856 of the memory device, the number value of the CCD cell having 
the largest number outputting black label (no less than 3.5 V) out of the 
first to 32nd CCD cells of the image sensor 13. Now, if the 9th CCD cell 
to 16th CCD cell provide black level, the value to be stored in the memory 
address 1856 is 16, for example. 
(16) When the scanner portion 1' continues to run and the value of the Y 
address becomes 81 (the scanning portion ran by 10 mm shown at l6 Y 
direction timing mark 36 and the effective reading area B is the scanning 
area of the image sensor 13), the CPU 50 sets the signal STATE to an 
active state, that is, "1", which signal indicates that the image reading 
operation is being carried out. At the same time, the CPU 50 outputs the 
signal SYNC indicative of the start of 1 line of the data, the clock 
signal CLOCK giving the transferring timing of the data, and the data DATA 
read from the image sensor 13 through the cable 25. 
The image data DATA outputted from the CPU will be described. Each of the 
output data from (X address+33)=49th CCD cell to the (49+512-1)=560th CCD 
cell is compared with the respective ones of the slice levels SLICE 49 to 
SLICE 560 stored in the fourth RAM area of the CPU 50. Whether it is black 
or white is determined dependent on the result of comparison, and the 
values corresponding to the results of comparison are outputted as the 
data signals DATA. Namely, if the CCD cell output is larger than the slice 
level and it is dark, the value "1" is outputted, and if the output is 
smaller than the slice level and it is near white, the value "0" is 
outputted. In this manner, image information provided from 512 CCD cell 
outputs corresponding to the effective reading area are outputted. The 
position where the effective reading area is terminated can be detected by 
monitoring the Y address. 
In the above described embodiment, all of the 576 CCD cell outputs are used 
in detecting the white level for providing the slice level. Alternatively, 
the outputs from the CCD cells in the area from which the white level is 
surely detected may be used. 
In any case, by providing the slice level using the CCD cell outputs in the 
range larger than the effective reading area (the area B in FIG. 4), 
whether the image information of the object is white or black can be 
surely and reliably determined. 
As described above, according to the present invention, the scanner portion 
and a driving portion for driving the scanner portion are integrally 
provided in a self-running type scanner, so that the number of parts as 
well as the time required for the assembly can be reduced, enabling 
provision of an inexpensive self-running type scanner capable of surely 
providing image information. 
Since an Y direction timing mark and a X direction timing mark are provided 
on a running assisting plate, it is adapted such that the position for 
starting actual image reading of the object is determined in accordance 
with the timing marks and the data of several lines in a white area 
provided on the running assisting plate are used to provide reference for 
determining whether the read information of the object is white or black, 
influences of an unevenness in color in the white area, the dust, 
degradation of illuminating light source and the like can be removed and 
the image information of the object can be surely provided. 
Although the present invention has been described and illustrated in 
detail, it is clearly understood that the same is by way of illustration 
and example only and is not to be taken by way of limitation, the spirit 
and scope of the present invention being limited only by the terms of the 
appended claims.