Document scanner driven by electromagnetic actuators

A two-dimensional image pick-up device using a one-dimensional image pick-up element which is useful as an image reader. Drive coil type linear motors for driving an element moving carriage in the subscanning direction of the one-dimensional image pick-up element are disposed on both sides of the element moving carriage, enabling the deivce to be economically small-sized as a whole.

TECHNICAL FIELD 
The present invention relates to a two-dimensional image pick-up device in 
which subscanning is mechanically carried out by using a one-dimensional 
image pick-up element. 
BACKGROUND ART 
FIG. 7 is a perspective view illustrating a conventional two-dimensional 
image pick-up device disclosed in the Japanese Laid-Open Patent 
Publication (unexamined) No. 58-69173, FIG. 8 is an exploded perspective 
view illustrating an element moving carriage and guide rail of the 
conventional two-dimensional image pick-up device, and FIG. 9 is a 
sectional view illustrating that the element moving carriage and the guide 
rail in FIG. 8 are in an assembled state. 
In these drawings, reference numeral 1 indicates a frame of the 
two-dimensional image pick-up device, numeral 2 indicates the guide rail 
mounted on the frame 1, and numeral 3 indicates the element moving 
carriage which is supported on the guide rail 2 through the bearings 4, 5 
(see FIGS. 8 and 9) so as to be movable in the direction of the arrows A 
and B. The one-dimensional image pick-up element (not illustrated) is 
attached to the element moving carriage 3. Numeral 6 indicates an arm of 
the element moving carriage 3, numeral 7 indicates a spring for downward 
partial loading connected to the arm 6, numeral 8 indicates a micrometer 
head which is disposed beneath the arm 6 and securely fitted to the frame 
1 through a fitting member 9. The micrometer head 8 having a spindle 10 
connected to the arm 6 comprises a motion converting mechanism 11 of 
micrometer type which converts an inputted rotary motion to a linear 
motion in the axial direction of the spindle 10, and a rotary encoder 12 
which detects the rotary motion and generates a pulse for each rotary 
motion of a specified angle, so that the spindle 10 pushes up the arm 6 of 
the element moving carriage 3 against the spring 7. Numeral 13 indicates 
an input gear mounted on the rotary input shaft of the micrometer head 8, 
numeral 14 indicates an electric motor installed in the vicinity of the 
micrometer head 8, and numeral 15 indicates an output gear engaged with 
the input gear 13. Numeral 16 indicates an upper side limit switch 
disposed above the element moving carriage 3, and numeral 17 indicates a 
lower side limit switch disposed beneath the element moving carriage 3. 
These upper and lower side limit switches 16 and 17 automatically stop the 
motor 14 when the element moving carriage 3 moving up and down (in linear 
motion) reaches a prescribed position and turns the switches on. Numeral 
18 indicates an optical system which generates image of an original 
picture on the focal plane, and numeral 19 indicates a disc carriage for 
exchanging filters. A red filter 20, a green filter 21, a blue filter 22 
and a black-and-white filter 23 are respectively arranged in the filter 
exchanging carriage 19 with equal distance therebetween. Numeral 24 
indicates a filter exchanging electric motor which intermittently drives 
the filter exchanging carriage 19 rotationally, so that each of red, 
green, blue and black-and-white filers 20 to 23 is exchanged and comes at 
the position corresponding to the optical system 18. 
A conventional device of above construction operates as follows. 
When the motor 14 starting, the rotary input shaft of the motion converting 
mechanism 11 is rotationally driven through the output gear 15 and the 
input gear 13, and the rotation is converted to a linear motion by the 
motion converting mechanism 11 and transmitted to the micrometer head 8, 
whereby the arm 6 of the element moving carriage 3 starts a linear motion 
so that the one-dimensional image pick-up element of the element moving 
carriage 3 is scanned along the guide rail 2. The range of the linear 
motion of the element moving carriage 3 at the time of scanning is 
determined by counting pulses from the rotary encoder 12. Further, as the 
result of intermittent rotational drive of the filter exchanging carriage 
19 by means of the filter exchanging motor 24, any one of the red, green, 
blue and black-and-white filters can alternatively assume a position in 
the light path behind the position of optical system 18. 
Since the conventional two-dimensional image pick-up device is constructed 
as described above, the element moving carriage 3 and the filter 
exchanging carriage 19 are individually driven by the two motors 14 and 24 
for their respective exclusive use. Moreover, the rotation of the motor 14 
is converted to a linear motion and transmitted to the element moving 
carriage 3, and the micrometer head 8 is required for the subscanning of 
the element moving carriage 3. Accordingly, a problem exists in that the 
conventional device is undesirably large-sized as a whole. Besides, since 
the filter exchanging carriage 19 is of rotary type, the size of the color 
filters is required to correspond to the subscanning distance of the 
one-dimensional image pick-up element 25 at the time of exchanging the 
filters, whereby the color filters are also obliged to be large-sized. As 
a result the filter exchanging carriage 19 itself is also large-sized. 
This brings about such a drawback as increase in cost. 
SUMMARY OF THE INVENTION 
The present invention was made to overcome the above-discussed drawback and 
has an object of providing a novel two-dimensional image pick-up device 
which is small-sized thereby contributing to reduction in cost. 
To accomplish the foregoing object, in the two-dimensional image pick-up 
device according to the invention, drive coil type linear motors for 
driving the element moving carriage in the subscanning direction of 
one-dimensional image pick-up element are disposed on both sides of the 
element moving carriage on which the one-dimensional image pick-up element 
is mounted positionally corresponding to the optical system. 
In the two-dimensional image pick-up device of the above construction 
according to the invention, when supplying power to the drive coils of the 
linear motors, a driving force for moving the element moving carriage is 
generated in the voice drive coils, and the one-dimensional image pick-up 
element is subscanned by the movement of the element moving carriage.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
An embodiment of the present invention is now described with reference to 
the accompanying drawings, in which FIG. 1 is a partially sectional 
perspective view of the two-dimensional image pick-up device according to 
one embodiment of the present invention; FIG. 2 is a schematic front view 
of the two-dimensional image pick-up device; FIG. 3 is a perspective view 
illustrating the relative position detecting means for the element moving 
carriage and the filter exchanging carriage; FIG. 4 is a schematic view 
illustrating the absolute position detecting means for the element moving 
carriage; FIG. 5 is a block diagram schematically illustrating the 
arrangement in FIG. 1; and in which like reference numerals are designated 
to the same or like parts as FIGS. 7 to 9 to omit repeated description. 
In the drawings, numerals 2a, 2b indicate guide rails comprising a pair of 
round bars disposed at positions parallel to each other, and the element 
moving carriage 3 is movably supported on the guide rails 2a, 2b through 
the bearings 4a, 4b (see FIGS. 1 and 2). Numeral 19 indicates a plate-like 
filter exchanging carriage which is disposed between the element moving 
carriage 3 and the optical system 18 (see FIG. 5) and driven in the safe 
direction as the element moving carriage 3 in parallel thereto. The filter 
exchanging carriage 19 is mounted with red filter 20, green filter 21, 
blue filter 22 and black-and-white filter 23, each arranged at a certain 
distance therebetween in the direction of width the of the filter 
exchanging carriage 19. Numeral 25 indicates one-dimensional image pick-up 
element mounted on the element moving carriage 3 to be subscanned, and 
numeral 26 indicates relative position detecting means mounted on the 
element moving carriage together with the one-dimensional image pick-up 
element 25 for detecting a relative position between the element moving 
carriage 3 and the filter exchanging carriage 19. Numeral 26a indicates a 
detecting fin of the relative position detecting means 26, which is 
attached to the filter exchanging carriage 19. Numeral 27 indicates drive 
coils fixed to both ends of the element moving carriage 3, numeral 28 
indicates yokes of magnetic circuits each forming a drive source of the 
element moving carriage 3, and which are arranged on both ends of the 
element moving carriage 3, and numeral 29 indicates permanent magnets 
respectively fixed to the yokes 28. The permanent magnets 29 and the drive 
coils 27 form linear motors M1 which drive the element moving carriage 3 
in the subscanning direction of the one-dimensional image pick-up element 
25. Numeral 30 indicates rail supporting members respectively provided on 
the yokes 28, and numeral 31 indicates guide rails each comprising a round 
bar supported by the rail supporting member 30. Both end portions of the 
filter exchanging carriage 19 are movably supported by the guide rails 31. 
Numeral 34 indicates a drive coil which is wounded around the yoke 28 of 
one of the magnetic circuits serving as a drive source of the element 
moving carriage 3 and crosses over the magnetic field of the permanent 
magnet 29, thus forming a part of the linear motor M1 to drive the filter 
exchanging carriage 19. Numeral 35 indicates an optical sensor serving as 
the absolute position detecting means for detecting the absolute position 
of the element moving carriage 3 with respect to the stationary side. The 
optical sensor 35 is provided with a light source 36 such as a light 
emitting diode attached to the element moving carriage 3 side, a diaphragm 
plate 37 arranged in front of the light source 36 and having an aperture 
for restricting light from the light source 36, a reflecting mirror 38 and 
a lens 39 both arranged in front of the light source 36, as illustrated in 
FIGS. 4 and 5. Numeral 40 indicates a position detecting circuit for 
detecting the absolute position of the element moving carriage 3, and 
numeral 41 indicates a controller to which an absolute position detecting 
signal and a command signal b from the position detecting circuit 40 are 
inputted, and from which a control current obtained as the result of 
comparison of the signals is sent to the drive coils 27 of the element 
moving carriage 3. Numeral 42 indicates a controller to which an input 
signal and a command signal "a" from the relative position detecting means 
26 are inputted and compared, and from which a control current 
corresponding to the value obtained by the comparison is supplied to the 
voice coil 34 of the filter exchanging carriage 19. 
The device of the above arrangement operates as follows. 
When the current is supplied from the controller 41 to the drive coils 27 
of the element moving carriage 3 located in the magnetic field of the 
permanent magnets 29, a driving force for driving the element moving 
carriage 3 is generated in the drive coils 27 in the direction of the 
arrow A (or arrow B) in FIG. 1, and, by this driving force, the element 
moving carriage 3 moves in the direction A (or B) and subscans the 
one-dimensional image pick-up element 25. When light from the light source 
36 is detected by the optical sensor 35 through the diaphragm plate 37, 
reflecting mirror 38 and lens 39 at the time of subscanning, the detected 
signal is inputted to the position detecting circuit 40 which detects the 
absolute position of the element moving carriage 3, and this detected 
signal is then inputted to the controller 41, whereby the controller 41 
compares the input signal from the position detecting circuit 40 with the 
command signal b and determines a quantity of current to be supplied to 
the drive coils 27 so that the current corresponding to the determined 
quantity is supplied thereto. In this manner, the element moving carriage 
3 moves in the subscanning direction by a distance which corresponds to 
the quantity of current determined based on the command signal "b", thus 
positioning the one-dimensional image pick-up element 25 in the 
subscanning direction. 
In the filter exchanging carriage 19, when a current is supplied from the 
controller 41 (see FIG. 4) to the drive coil 34 for exchanging the color 
filters located in the magnetic field of the magnetic circuits 28, a force 
generated in the drive coil 34 serves as a driving force for the filter 
exchanging carriage 19, whereby the carriage 19 moves in the subscanning 
direction to place the proper color filter 20 to 23 in the light path. In 
this manner, the magnetic circuits 28 perform a function of driving both 
element moving carriage 3 and filter exchanging carriage 19. In addition, 
likewise in the filter exchanging carriage 19, the controller 42 compares 
the input signal from the relative position detecting means 26 with the 
command signal "a" and determines a quantity of current to be supplied to 
the drive coil 34, so that a relative positional relation between the 
filter exchanging carriage 19 and the element moving carriage 3 is 
controlled by the command signal "a" which corresponds to the determined 
quantity of current, eventually selecting the color filters 20 to 23. When 
the element carriage 3 is scanned in accordance with the command signal 
"b", a current is supplied to the drive coil 34 so as to keep a relative 
positional relation controlled by the command signal "a", whereby the 
element moving carriage 3 and the filter exchanging carriage 19 are held 
at their appropriate relative position. 
In effect, the absolute position of the element moving carriage 3 is 
detected by the optical sensor 35 without contact, and a relative position 
between the element moving carriage 3 and the filter exchanging carriage 
19 is detected by the relative position detecting means 26, whereby the 
filter exchanging carriage 19 is controlled by the controller 42 in the 
system, making it possible to carry out accurately the positioning of the 
element moving carriage 3 and the subscanning. 
FIG. 6 illustrates another embodiment of the invention, in which the drive 
coil 34 for color filter exchange is so arranged as to cross over the 
magnetic field of the element driving magnetic circuit 28 on the opposite 
side of that in FIG. 1. Other arrangements and functions remain the same 
as in the foregoing embodiment. 
In addition, the drive coil 34 for color filter exchange can be wound 
around each yoke of the magnetic circuits 28 on both sides, in which case 
the filter exchanging carriage 19 is driven on both sides allowing the 
same to be driven more smoothly. 
FIG. 10 illustrates a further embodiment, in which another linear motor M3 
for exclusive use in connection with color filter exchange is additionally 
disposed on the opposite side of the linear motor M2 for exclusive use in 
connection with color filter exchange in the foregoing embodiment, so that 
the filter exchanging carriage 19 is driven by these two linear motors M2, 
M3 both for exclusive use in connection with color filter exchange. 
Accordingly the driving of the filter exchanging carriage 19 can be 
carried out even more smoothly. The additional linear motor M3 comprises a 
permanent magnet 33a provided in the yoke 32a of the magnetic circuit of 
the system, and a drive coil 34a which is attached to the arm 19b on the 
opposite side of the arm 19a of the filter exchanging carriage 19 in such 
a manner as to cross the permanent magnet 33, eventually resulting in the 
same design as the linear motor M2 on the opposite side. 
It is also preferred that a PSD (position sensing device) is adopted in 
place of the optical sensor 35 in the foregoing embodiment. 
As has been described so far, since drive coil type linear motors are 
adopted as drive source for subscanning the one-dimensional image pick-up 
element in the present invention, an advantage is achieved such that the 
entire device can be small-sized resulting in reduction of cost. 
The present invention can be utilized as an image reader used as a 
peripheral device for a computer.