Magnification varying mechanism for image forming apparatus

A copier for providing photographic copies of different sized originals, having an optical system variable for altering the magnification of an original, a scale member movable to locate the end of each respective size of original on the copier, and a link mechanism intercoupling the optical system and the scale to automatically vary the system magnification in accordance with the location of the scale.

BACKGROUND OF THE INVENTION 
The present invention relates to a technique for changing over optical 
systems having different magnification powers upon alteration of the size 
of original in an image forming apparatus in which the original and a film 
are both disposed in the stationary state so that the original is imaged 
on a surface of the film and which apparatus is arranged such that a 
center portion of an original supporting stage is projected substantially 
onto a center portion of the film. 
In the image forming apparatus in which an original is placed on a 
supporting stage and the image thereof is formed on a light sensitive 
medium such as film or the like, the original has to be so positioned that 
the center thereof coincides with that of the image regardless of 
variation in the size of the original. Otherwise, a portion of the 
original may be excluded from the image. Further, when originals of 
different sizes are to be taken on a film of a same size, there are 
required a plurality of lenses having different magnification powers in 
accordance with the sizes of the originals. Thus, operator must position 
an original and select the lens in accordance with the size of the 
original before photographing it. 
However, the operator may neglect the above procedure and select a wrong 
lens, resulting in wasteful photographing to disadvantage. 
In view of the drawback of the prior art described above, it is an object 
of the present invention to provide a magnification power varying 
mechanism for automatically changing the taking lens to the one having a 
requisite magnification power upon positioning of an original. 
SUMMARY OF THE INVENTION 
For achieving the abovementioned object, the present invention provides a 
magnification varying mechanism for an image forming apparatus arranged 
such that a center portion of an original supporting stage is projected 
substantially to a center portion of an image formed on a light sensitive 
medium, characterized by a scale for regulating end portions of originals 
of different sizes, optical systems including lenses having different 
magnification powers in accordance with the sizes of the originals and a 
mechanism for changing over the optical systems in interlock with the 
movement of the abovementioned scale.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the following, an exemplary embodiment of the present invention will be 
described. FIG. 3 shows an external appearance of an image forming 
apparatus which includes a press plate 2 for keeping an original in place, 
a photographing camera 3, and a manipulation field 4 for manipulating the 
apparatus. A general arrangement of the image forming apparatus to which 
the present invention is applied will be described by referring to FIG. 2. 
The original 2 is disposed on a contact glass plate 5 constituting an 
original supporting stage and kept immovably in place by the press plate 
2. The original 1 is illuminated by a flash lamp 6, wherein light 
reflected from the original is reflected at a first mirror 7 and a second 
mirror 8 and transmits through an optical system 9 composed of a taking 
lens to be focused onto a film 10. The film 10 is contained in the camera 
3 shown in FIG. 3, the exposure being effectuated by opening a shutter in 
synchronism with light emission of the flash lamp. 
FIG. 1 is a plan view showing an exemplary embodiment of the present 
invention, and FIG. 2 shows schematically an internal structure of the 
image forming apparatus associated with the exemplary embodiment. In the 
case of the exemplary embodiment of the present invention, two originals, 
i.e. an original of A4 size according to the ISO (210.times.297 mm) and an 
original of 5".times.7" (127.times.178 mm) in size are demonstrated as the 
originals of different sizes, by way of example. A reference point 5' is 
provided in the vicinity of the center of the original supporting stage 
constituted by the contact glass plat 5 so that an image of the original 
corresponding to this reference point is projected to the center of the 
film. 
The image forming apparatus is so arranged that the optical axis of the 
taking optical system constantly coincides with the reference point of the 
original supporting stage and that the flash lamp constituting the 
illuminating light source illuminates the original around the center of 
the original supporting stage. Since both of the stage and the flash lamp 
are disposed fixedly, it is required to align the center of the original 
with the reference point of the original supporting stage. 
More specifically, the image forming apparatus must be able to copy high 
quality color images of different sizes on a surface of film by varying 
the magnification. In this conjunction, distribution of quantity of light 
illuminating the original is critical and it is difficult to ensure the 
distribution satisfactorily unless the optical axis remains constant. 
Describing the exemplary embodiment of the present invention by referring 
to FIG. 1, a stationary scale 14 is fixedly provided at one edge of the 
contact glass 5 located at a bottom position as viewed in the figure. The 
original of A4 size can be positioned by abutting one end thereof against 
an end of the stationary scale 14. For positioning the original of 
5".times.7" in size, a movable scale 11 is provided. The movable scale can 
be rotated around a shaft 17 thereof from a set position (the position for 
setting in place the original of 5".times.7" in size) shown in a solid 
line to a retracted position extending in parallel with a side of the 
contact glass 5 indicated by a dotted line for allowing the original of A4 
size to be used. 
The taking optical system 9 includes a lens 21 for the size of 5".times.7" 
and a lens 22 for the A4 size both of which are disposed on a turret 15 so 
that a same size of image can be obtained by changing over the 
magnifications of these lens. When the movable scale 11 is set to the 
position for accommodating an original of 5".times.7" in size, the lens 
for the size of 5".times.7" is employed. When the movable scale 11 is 
moved to the retracted position for allowing an original of A4 size to be 
used, the lens for the size of A4 is employed. To this end, a mechanism of 
automatically changing over the lenses is incorporated, as is explained 
below. 
Referring to FIGS. 1 and 2, when the movable scale 11 is rotated to the set 
position (position shown in the solid line) for imaging an original of 
5".times.7" in size, an actuator element 12 mounted on the shaft of the 
movable scale 11 presses a microswitch 13, whereby a signal is produced to 
rotate a motor 16 in one direction, as the result of which the turret 15 
is rotated by way of a gear wheel 16' mounted on the motor shaft and a 
gear 15' formed in the turret 15 to thereby bring the lens 21 for the size 
of 5".times.7" to the position of the axis of the taking optics. FIG. 4 
shows in an enlarged view an associated detecting structure. When the 
abovementioned lens has attained the predetermined position, this is 
detected by a microswitch not shown, whereupon the motor 16 is stopped. 
The turret 15 is provided with a click stop not shown to fix the turret at 
the position where the axes of the optical systems are aligned. In this 
state, an original of 5".times.7" in size can be abutted against the 
movable scale and photographed. 
When an original of A4 size is to be photographed, the movable scale 11 is 
rotated to the retracted position shown in the dotted line in FIG. 1, 
whereupon the microswitch 13 is restored, producing a signal for rotating 
the motor 16 in the direction opposite to that mentioned above, as the 
result of which the turret 15 is rotated in the reverse direction by way 
of the gear wheels 16' and 15' until the lens for the A4 size has been set 
at the taking position. The stopping of the motor as well as operation of 
the chick stop is realized similarly to the manner mentioned before. 
With the arrangement described above, operation of moving the movable scale 
to operative position or inoperative position by operator is interlocked 
with the automatic selection of the optical system having a proper 
magnification power. 
FIG. 5 shows another exemplary embodiment of the present invention 
according to which a change-over mechanism composed of a link mechanism is 
provided between the movable scale and the optical systems. When the 
movable scale 11 is rotated to the set position corresponding to one 
original, a lever 18 mounted on a rotatable shaft 17 for the movable scale 
11 is rotated. A pin 18' anchored in the lever 18 at the other end thereof 
engages in an elongated slot-like groove 26 provided in the turret. 
Rotation of the lever 18 is transmitted to the turret 15 by way of the pin 
18' and the groove 26, whereby the turret 15 is rotated around a shaft 23 
thereof. When the lens 21 for the size of 5".times.7" is brought to the 
taking position, an arm pin 19' of an arm 19 biased by a spring 20 rides 
on a slanted face 15a of the turret, resulting in that the turret 15 is 
pressed against a stopper 25, whereby the optical axis of the optical 
system is positioned in alignment (FIG. 6). 
When the other original of A4 size is used, the movable scale 11 is rotated 
to the retracted position. In this case, the lever 18 and the turret 15 
are rotated in the direction reverse to that mentioned above, whereby the 
lens for the A4 size is set to the taking position by the turret, while 
the arm pin 19' abuts on a slanted face 15b of the turret 15 provided on 
the opposite side to press the turret against the stopper 24. Positioning 
of the optical axis is thus accomplished. According to the instant 
embodiment, the motor and the microswitch can be spared, being attendant 
with reduction in cost. Besides, due to the mechanical structure, 
reliability is also enhanced. 
FIGS. 7 and 8 shows an exemplary embodiment applicable to the movable scale 
11 and the stationary scale 14 described above. As the means for 
positioning an original of slightly different size, the scale is 
constituted by a scale provided with an offset. A numeral 36 designates a 
scale for positioning an original having a letter size according to the 
U.S.A Standards (216.times.279 mm), and 35 designates a scale for 
positioning an original of A4 size according to the ISO (210.times.297 
mm), wherein both scales are fixedly mounted on the original supporting 
stage in a superposed state. The original of the letter size is abutted 
against a front end of the scale 36 for the positioning thereof, while the 
original of A4 size is abutted against a front end of the scale 35. A 
numeral 31 denotes a cover, 32 denotes a side plate having the scale for 
letter size mounted at one end, 33 denotes a set screw, and 34 denotes a 
spacer. In FIG. 8, 1a indicates the set state of an original of the A4 
size and 1b indicates the state of an original of the letter size. 
The scales 35 and 36 may be implemented in one scale formed with the 
offset. Further, a plurality of offsets may be provided for coping with 
various sizes of originals. The illustrated embodiment is very effective 
in handling originals of sizes differing only slightly within a range in 
which the magnification powers of the lenses need not be changed over. By 
applying this embodiment to the stationary scale 14 and the movable scale 
11, the apparatus can deal with originals of numerous types. 
According to the present invention, the scales are provided in 
correspondence with the sizes of originals, wherein the optical system 
having a proper magnification power can be selected by abutting an end of 
an original against the selected scale. Thus, photographing of high 
quality color image can be carried out in a simplified manner without 
mishandling.