JPH0333256B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an optical device for slit exposure of an image of a document to be copied onto a photoreceptor at variable magnification in a variable magnification electrostatic copying machine.

[Prior art]

Recently, a variable magnification electrostatic copying machine has been proposed that can selectively copy a document to be copied at two or more magnifications, for example, the same magnification and reduction or enlargement of a predetermined magnification. It has been put into practical use. Such copying machines are equipped with an optical device for slit exposure of an image of a document to be copied onto a photoreceptor at variable magnification. This optical device includes a support frame that is moved as the copying magnification changes, and a lens is fixed to the support frame. As is well known to those skilled in the art, when the exposure magnification of the original image is changed, the exposure amount on the photoreceptor is changed. In order to expose the photoreceptor, it is necessary to appropriately modify the exposure amount in response to changes in the exposure magnification of the original image (this point will be further discussed later with reference to the accompanying drawings). Such exposure correction is generally accomplished by moving an exposure correction plate into the optical path or separating it from the optical path in accordance with a change in the exposure magnification of the original image.

[Problems with conventional technology]

Optical devices that include exposure correction plates have problems to be solved, such as the need to provide special movement and positioning means to move the exposure correction plate as desired in response to changes in magnification.

[Purpose of the invention]

The present invention has been made in view of the above facts, and its main purpose is to provide a variable exposure correction plate that allows the exposure correction plate to be moved as required in response to changes in magnification without requiring special movement and positioning means. An object of the present invention is to provide an optical device for a magnification electrostatic copying machine.

[Means for solving the invention]

According to the present invention, in order to solve the above-mentioned main object, an optical device for slit exposing an original to be copied onto a photoreceptor in a variable magnification electrostatic copying machine is provided. 2
a support frame mounted so as to be movable between different positions;
The lens includes a lens fixed to the support frame, an exposure correction plate attached to the support frame, and at least one fixed reflecting mirror, and the support frame is moved from one of the two positions to the other. and an optical device characterized in that the exposure correction plate is partially allowed to enter into an optical path that is bent with respect to the optical axis of the lens by the bending action of the reflecting mirror. .

[Preferred specific example]

A more detailed explanation will be given below with reference to the accompanying drawings.

General Overview of the Copying Machine Reference is first made to FIG. 1, which is a simplified cross-sectional view of a variable magnification electrostatic copying machine having a preferred embodiment of an optical system constructed in accordance with the present invention. We will outline the overall structure of.

The illustrated copying machine has a generally rectangular parallelepiped-shaped housing, which is indicated by the number 2 as a whole. A transparent plate 4 on which an original to be copied is placed is disposed on the upper surface of the housing 2. As shown in FIG. The transparent plate 4 is supported by a support frame (not shown) attached to the upper surface of the housing 2 so as to be movable in the left and right directions in FIG. When the camera is moved, it is moved from the stop position shown by the solid line in FIG. 1 to the right direction in FIG. It is moved in the scanning exposure direction to the scanning exposure end position shown by the two-dot chain line 4B, and then moved back from the scanning exposure end position to the above-mentioned stop position. The support frame (not shown) on which the transparent plate 4 is supported is further equipped with a document holder (not shown) that can be opened and closed to cover the transparent plate 4 and the document placed thereon. has been done.

A horizontal substrate 6 is disposed within the housing 2 and divides the inside of the housing 2 into an upper space and a lower space. Approximately in the center of the lower space is a cylindrical rotating drum 8 that constitutes a support base for the photoreceptor.
is rotatably mounted, and a photoreceptor 10 is disposed on at least a portion of the circumferential surface of the rotating drum 8. Instead of the rotating drum 8, it is also possible to use an endless belt-like element, which is well known to those skilled in the art, and to arrange the photoreceptor on at least part of the surface of such an endless belt-like element.

Around the rotating drum 8, which is rotationally driven in the direction shown by the arrow 12, there are, in order in the direction of rotation, a charging corona discharger 14, a static elimination lamp 16 that is activated during reduction copying, a developing device 18, and a transfer device. A corona discharger 20 and a cleaning device 22 are provided. The charging corona discharger 14 substantially uniformly charges the photoreceptor 10 to a particular polarity. An exposure area 24 exists between the charging corona discharger 14 and the static elimination lamp 16, and in this exposure area 24, the original on the transparent plate 4 is projected by an optical device, which will be described later, and thus onto the photoreceptor 10. An electrostatic latent image is formed. The static elimination lamp 16 is activated when reduction copying is performed as will be described later, and the photoreceptor 10 is charged by the charging corona discharger 14 but on which no original is projected in the exposure area 24.
irradiate one side of the battery to eliminate the charge on that side. Development device 18, which itself may be of any suitable form known in the art, applies toner particles to the electrostatic latent image on photoreceptor 10 and develops the electrostatic latent image into a toner image. The transfer corona discharge device 20 applies corona discharge to the back side of the copy paper that is brought into contact with the surface of the photoreceptor 10 in the transfer area 26, thereby transferring the toner image on the photoreceptor 10 onto the copy paper. The illustrated cleaning device 22 is selectively positioned in either an active position shown by a solid line in FIG. 1 or a non-active position shown by a two-dot chain line. When the cleaning device 22 is positioned at the operating position, a blade 28 made of an elastic material is pressed against the surface of the photoreceptor 10, and the action of the blade 28 causes the removal of particles remaining on the photoreceptor 10 after transfer. Any remaining toner particles are removed from photoreceptor 10.

At the bottom of the housing 2, there is a copy paper supply mechanism, generally designated by the number 30, and a copy paper, generally designated by the number 32, for conveying the copy paper fed from the copy machine supply mechanism 30 through the transfer area 26. A transport mechanism is provided. Illustrated copy paper supply mechanism 30
The apparatus is well known in itself and includes a cassette receiving part 34, a copy paper cassette 36 which is detachably attached to the cassette receiving part 34, and a feeding roller 38. The feed roller 38 is selectively driven to rotate in the direction indicated by an arrow 40, and feeds the plural sheets of copy paper P stored in the copy paper cassette 36 in a stacked state one by one to the copy paper transport mechanism 32. send.
The illustrated copy paper transport mechanism 32 is a copy paper supply mechanism 3.
a pair of carry-in rollers 42 for receiving and conveying the copy paper P fed from 0, a pair of guide plates 44, a pair of conveyance rollers 46, a pair of guide plates for guiding the copy paper P from the pair of conveyance rollers 46 to the transfer area 26; 48, a roller 50 that peels off the copy paper P that has been brought into contact with the photoreceptor 10 in the transfer area 26 from the photoreceptor 10 and carries it out from the transfer area 26, a guide plate 52, a pair of fixing rollers 54, a guide plate 56, a carry-out roller pair 58, and unloading roller pair 58
It includes a receiving tray 60 for receiving the copy paper P carried out from the housing 2. One roller of the pair of fixing rollers 54, that is, the roller located above, is equipped with a heating element (not shown) inside.
The surface of the copy paper P having the toner image transferred from the photoreceptor 10 is pressed and heated, thus fixing the toner image on the copy paper P. This roller is further provided with a peeling guide member 62 that peels the copy paper P from its surface and guides it downstream. A static elimination lamp 64 is disposed above the guide plate 52. The charge eliminating lamp 64 irradiates light onto the copy paper P being conveyed on the guide plate 52 to eliminate the charge remaining on the copy paper P, and also serves to dissipate the charge remaining on the copy paper P, and also to dissipate the charge remaining on the copy paper P. The photoreceptor 10 is irradiated with light in the area between the two to eliminate the charge remaining on the photoreceptor 10 after the transfer.

In the upper space above the horizontal substrate 6 in the housing 2, a transparent plate 4 moves leftward in FIG. An optical device, generally designated by the number 66, is provided for projecting the original placed on the transparent plate 4 onto the photoreceptor 10 for slit exposure during scanning exposure movement. The illustrated optical device 66 includes an original irradiation lamp 70 for irradiating the original placed on the transparent plate 4 through an original irradiation aperture 68 formed on the upper surface of the housing 2, as well as an original irradiation lamp 70 for irradiating the original placed on the transparent plate 4. 10, a first reflector 72, a second reflector 74, a third reflector 76, a lens assembly 78, and a fourth reflector 80. Original irradiation lamp 70
The reflected light from the original that is irradiated onto the document is sequentially reflected by a first reflecting mirror 72, a second reflecting mirror 74, and a third reflecting mirror 76, and then is housed in a lens assembly 78. The fourth reflecting mirror 8
0, is reflected by the fourth reflecting mirror 80, passes through the opening 82 formed in the horizontal substrate 6, and reaches the photoreceptor 10 in the exposure area 24. A colored glass 83, which is known per se, is arranged between the aperture 82 and the photoreceptor 10 to compensate for the special characteristics of the photoreceptor 10. Further, between the opening 82 and the photoreceptor 10, there is a slit exposure width regulating member 84 for regulating the width of the optical path to the photoreceptor 10 in the movement direction of the photoreceptor 10 (the movement direction of the transparent plate 4), that is, the slit exposure width. is also provided.

In the illustrated copying machine, the housing 2
At the left end in FIG. 1, a blower 86 made of a Sirotsko type fan and a blower 88 made of a normal impeller type fan are disposed. The blower 86 sucks air from outside the housing 2 through a suction hole 90 formed on the top surface of the housing 2 and discharges the air through a discharge hole 92 formed on the left side of the housing 2, thus causing the document irradiation lamp 70 to The transparent plate 4 heated by is cooled. The blower 88 sucks air in the lower space below the horizontal substrate 6 of the housing 2 and discharges it through a discharge hole 92 formed on the left side of the housing 2, thereby removing the heat from, for example, the fixing roller pair 54. To prevent deterioration of the photoreceptor 10 due to being transmitted to the photoreceptor 10.

Thus, the illustrated copying machine has at least two copying magnifications, e.g., copying at substantially equal magnification and copying at approximately
The present invention is configured as a variable magnification electrostatic copying machine that can selectively perform a copying process at either a reduction copying ratio of 0.7x or approximately 0.5x in terms of area ratio. Although this point will be explained in more detail later, the basic principle of variable magnification copying in the illustrated copying machine will be briefly explained as follows.

In the illustrated copying machine, the rotary drum 8 is always rotated at a predetermined speed regardless of the copying magnification. Further, the copy paper transport mechanism 32 always moves at a predetermined speed regardless of the copying magnification, that is, at substantially the same speed as the moving speed of the photoreceptor 10 disposed on the circumferential surface of the rotary drum 8. Copy paper P is conveyed through. On the other hand, the transparent plate 4 is moved for scanning exposure at a speed that is changed according to the copy magnification, and the optical device 66 scans and exposes the original placed on the transparent plate 4 onto the photoreceptor 10 at a set magnification. Project. That is, when performing a copying process at substantially the same magnification, the transparent plate 4 is moved for scanning exposure at substantially the same speed as the moving speed of the photoreceptor 10 (and the moving speed of the copy paper passing through the transfer area 26). The optical device 66 projects the original placed on the transparent plate 4 onto the photoreceptor 4 at substantially the same magnification. However, at a predetermined copying magnification, that is, length ratio, M times (for example, M = approx.
0.7), when performing the copying process, the transparent plate 4
is scanned and exposed at a speed of V/M with respect to the speed V during full-size copying, and the dimension of the electrostatic latent image thus formed on the photoreceptor 10 in the direction of movement of the photoreceptor 10 (scanning exposure movement direction) dimension) is reduced (or enlarged) by M times. At the same time, the optical device 66, in the illustrated embodiment, includes a lens assembly 7, as will be explained in more detail below.
8, the second reflecting mirror 74, and the third reflecting mirror 76 are moved to the required positions, respectively.
The original placed on the transparent plate 4 is exposed to the photoreceptor 10 at a magnification of M.
The widthwise dimension of the electrostatic latent image thus formed on the photoreceptor 10 is reduced (or enlarged) by M times. In this way, a reduced (or enlarged) electrostatic latent image with a length ratio of M times is formed on the photoreceptor 10, and this reduced (or enlarged) electrostatic latent image is developed into a toner image, which is then copied. It is transferred to paper, thus obtaining a reduced (or enlarged) copy image.

Apparatus and Movement Mechanism of Optical Device As mentioned above, the copying machine shown in FIG. The copying process can be carried out by either reducing the size (length ratio: about 0.7 times, area ratio: about 0.5 times). When performing a copying process at substantially the same magnification, the optical device 66 copies the original placed on the transparent plate 4 onto the photoreceptor 10 disposed on the circumferential surface of the rotating drum 8 at substantially the same magnification. Project. When performing the copying process by reducing at a predetermined magnification, the optical device 66 transfers the original placed on the transparent plate 4 to the photoreceptor 1 disposed on the circumferential surface of the rotating drum 8 at the predetermined magnification.
Project onto 0.

When projecting an original placed on the transparent plate 4 onto the photoreceptor 10 at substantially the same magnification, the components of the optical device 66 are positioned as shown in FIG. ing. On the other hand, the transparent plate 4
When reducing and projecting the original placed on the photoreceptor 10 at a predetermined magnification, some of the components of the optical device 66, in the illustrated case, a lens assembly 78 and a second reflecting mirror 74 are used. and the third reflector 76 is moved as required. Lens assembly 78
is the photoreceptor 1 disposed on the circumferential surface of the rotating drum 8
In order to position the projected image reduced with respect to 0 as required, the photoreceptor 1 is moved in a direction inclined at a predetermined angle with respect to the optical axis of the optical device 66.
It is forced to approach 0. In addition, the second reflecting mirror 74
Even when the lens assembly 78 is brought close to the photoreceptor 10, the third reflecting mirror 76 maintains the focal length f of the lens housed in the lens assembly 78.
, the distance a between the original placed on the transparent plate 4 and the lens, and the distance b between the lens and the photoreceptor 10, as shown in the relationship 1/f=1/a+1/b. is somewhat distanced from the lens assembly 78 so that the lens is maintained.

Attachment of some of the components of optical device 66 (in the illustrated example, lens assembly 78 and second reflector 74 and third reflector 76) to achieve positional changes in accordance with the copying magnification. An example of the moving mechanism is as follows. Referring to FIGS. 2, 3, and 4 together with FIG. 1, the horizontal substrate 6 (FIGS. An inclined guide rod 98 extends at a predetermined angle θ (see FIG. 2) with respect to the optical axis of the optical device 66 extending in the left-right direction in FIGS. 1, 2, and 4. , is secured by a pair of mounting blocks 100. And this inclined guide rod 98
A pair of upright pieces 104 formed on one side of a support frame 102 for the lens assembly 78 are slidably attached to the lens assembly 78 . Main part 1 of support frame 102
As can be understood from FIG. A support block 108 is formed which is brought into contact with the support frame 102 and which is slidable over the upper surface of the horizontal base plate 6 as the support frame 102 is moved along the inclined guide rod 98. Therefore, the pair of upright pieces 104 of the support frame 102 are suspended on the inclined guide rods 98, and the support blocks 108 are in contact with the upper surface of the horizontal substrate 6, thereby ensuring that the support frame 102 is supported in the desired state. has been done. A positioning member 110 is also fixed on the horizontal substrate 6 in relation to the support frame 102 . Further, upright stop pieces 11 are provided at both ends of this positioning member 110.
2a and 112b are formed. Support frame 10
2 is at the same magnification position shown by solid lines in FIGS. When forced to do)
As shown in FIGS. 2 and 3, the support frame 102
The end edge of the protruding piece 114 formed on one side of the support frame 102 comes into contact with the stop piece 112b, while the support frame 102 is in the reduced position shown by the two-dot chain line in FIGS. is positioned at this reduced position, the optical device 66 reduces the original by a predetermined magnification and projects the original onto the photoreceptor 10), the front edge portion 11 of the main shaft 106 of the support frame 102
6 (FIG. 3) comes into contact with the stop piece 112a. A protruding piece 118 is also formed on the other side edge of the support frame 102, and a permanent magnet 1 is attached to the lower surface of this protruding piece 118.
20 is fixed. And this permanent magnet 1
20, a permanent magnet 12 is placed on the horizontal substrate 6.
Detection switches S1 and S2 for detecting zero are provided. As will be described in more detail later, the detection switch S1 detects the permanent magnet 120 when the support frame 102 is placed at or near the same magnification position, and the detection switch S2 detects the permanent magnet 120 when the support frame 102 is placed at or near the reduced position. permanent magnet 12
Detects 0.

The lens assembly 78 of the optical device 66 is mounted on the support frame 102 as required. With reference to FIGS. 5 and 6 together with FIG. 3, the support frame 102
To explain the mounting mechanism of the lens assembly 78, the lens assembly 78 itself includes a substantially hollow cylindrical lens housing 122, and at least one lens, usually a plurality of lenses, housed in the lens housing 122 as required. It is composed of a lens 124. To mount such a lens assembly 78 on the support frame 102 as desired, a coupling member 126 and a support member 128 are used in the illustrated embodiment. The connecting member 126 has a hollow cylindrical portion 130 having an inner diameter corresponding to the outer diameter of the lens housing 122 of the lens assembly 78, and flange portions 132 protruding from the cylindrical portion 130 on both sides in the radial direction. A screw hole 134 is formed in the cylindrical portion 130 and extends in the radial direction, and a pair of screw holes 136 are formed in the flange portion 132 in the axial direction. The connecting member 126 is fitted into a predetermined position in the center of the lens housing 122, and then inserted into the screw hole 134.
Screw the setscrew (not shown) into the
It is fixed to the lens assembly 78 by abutting the tip of the set screw against the surface of the lens housing 122 or by screwing it into a corresponding threaded hole (not shown) formed in the lens housing 122. On the other hand, the support member 128 has a base 138 and a protruding support piece 140 that stands upright from the base 138. A relatively large notch 142 is formed in the protruding support piece 140, extending from its upper edge to its lower edge. This notch 142
The protruding support piece 140 has an introduction part 142a extending downward from the upper edge of the protruding support piece 140 with a width somewhat larger than the outer diameter of the cylindrical part 130 of No. 6, and a tapered part 142b that gradually becomes narrower and extends downward from the introduction part 142a. .
Furthermore, a pair of through holes 144 located on both sides of the notch 142 are formed in the protruding support piece 140 . Such support member 128 has a base 138 thereof.
is fixed to the support frame 102 by fixing it to the upper surface of the main part 106 of the support frame 102 by an appropriate method such as welding or screwing. Connecting member 126
The lens assembly 78 to which is fixed is attached to the supporting member 128.
When mounting the lens assembly 78 on the support frame 102 to which the lens assembly 78 is fixed,
The connecting member 126 is inserted through the tapered portion 142b of the notch 142 onto the tapered portion 142b, and the outer peripheral surface of the cylindrical portion 130 of the connecting member 126 is placed on both side edges of the tapered portion 142b as shown in FIG. Next, one flat side of the flange portion 132 of the connecting member 126 is brought into contact with an adjacent flat side of the protruding support piece 140. After that,
The setscrews 146 are passed through each of the pair of through holes 144 formed in the protruding support piece 140 and are screwed into the pair of threaded holes 136 formed in the flange portion 132 of the connecting member 126, and thus the protruding support piece 1
A lens assembly 78 is secured to 40 . Connecting member 1
26 and the support member 128 as described above, the cylindrical portion 130 of the connecting member 126
By bringing the outer circumferential surface of the notch 142 into substantially point or line contact with each of both side edges of the tapered portion 142b, the vertical and lateral positions of the lens assembly 78 relative to the support frame 102 are accurately defined. and also the flange portion 13 of the connecting member 126
By bringing one flat side of the lens assembly 78 into contact with the adjacent flat side of the protruding support piece 140, the position of the lens assembly 78 in the axial direction with respect to the support frame 102 is accurately defined, and the position of the lens assembly 78 with respect to the support frame 102 is accurately defined. The axis of the lens assembly 78 is positioned exactly as desired (more specifically, so that it extends perpendicular to the protruding support piece 140). Therefore, the lens assembly 78 can be mounted as desired on the support frame 102 relatively simply and easily without requiring any skill. If desired, connecting member 126
is formed integrally with the lens housing 122 of the lens assembly 78, and the protruding support piece 140 is formed integrally with the lens housing 122 of the lens assembly 78.
It can also be formed integrally with. In addition, the cylindrical portion 130 of the connecting member 126 is omitted and the outer peripheral surface of the lens housing 122 is protruded from the notch 1 of the support piece 140.
It may be placed directly on the tapered portion 142b of 42.

As shown in FIGS. 2, 3, and 4, a projecting piece 148 is formed at one end of the support frame 102 (that is, the right end in FIGS. 2 and 4). An exposure correction plate 150 is attached to 148 . A pair of elongated holes 152 (only one of which is shown in FIG. 3) are formed in the exposure correction plate 150 at intervals in the lateral direction, and a set screw 154 is projected through each of the pair of elongated holes 152. By screwing into the piece 148, the protruding piece 148
The exposure correction plate 150 is attached to the exposure correction plate 150 so that its position can be adjusted (that is, the amount of projection from the projection piece 148 can be adjusted). The form, effects, etc. of the exposure correction plate 150 itself will be discussed in more detail later.

Explaining with reference to FIGS. 2 and 7, in addition to the support frame 102, a support frame 156 is also mounted on the horizontal substrate 6 (FIGS. 1, 3, and 4). There is. This support frame 156 includes a pair of side plates 158a and 1
58b and the pair of side plates 158a and 158.
and a member 160 connected between b. A second reflecting mirror 74 and a third reflecting mirror 76 (FIGS. 1 and 4) of the optical device 66 are mounted as required between the pair of side plates 158a and 158b. A pair of connection brackets 162 are fixed to the outer surface of one of the pair of side plates 158a and 158b. On the other hand, the horizontal substrate 6
(FIGS. 1, 2, and 4) A guide rod 166 is secured thereon by a pair of mounting blocks 164 that extends substantially parallel to the optical axis of the optical device 66. The pair of connecting brackets 162 are slidably connected to the guide rod 166. A short shaft 168 is embedded in the inner surface of the other side 158b of the pair of side plates 158a and 158b, and a roller 170 located on the horizontal substrate 6 is rotatably attached to the short shaft 168 (the (See also Figures 8-A and 8-B). Such a support frame 156 can be moved along the guide rod 166 by the pair of connecting brackets 162 sliding relative to the guide rod 166 and by the rollers 170 rolling on the horizontal substrate 6. 2 as a solid line and as shown in FIG. 2 (when the support frame 156 is positioned at this reduced position, the optical device 66 reduces the document at a predetermined magnification and projects the document onto the photoreceptor 10). It is positioned in

The optical device 66 further includes the support frame 102 described above.
It also includes a moving mechanism, generally designated by the number 172, for selectively positioning the support frame 156 at either the above-mentioned normal magnification position or reduced size position.

As shown in FIGS. 2 and 7, on the horizontal substrate 6 (FIGS. 1, 3, and 4), there is a base 174a fixed to the horizontal substrate 6, and a base 174a fixed to the horizontal substrate 6.
A mounting member 174 having a mounting portion 174b standing upright from 4a is mounted. The reversible electric motor 1 is attached to the mounting portion 174b of the mounting member 174.
A driving source composed of 76 is attached. In the illustrated embodiment, the reversible electric motor 176 extends through the mounting portion 174b of the mounting member 174 and the seventh
It has an output shaft 178 projecting forward in the figure, and the output shaft 178 itself constitutes the input shaft of the moving mechanism 172. However, if desired, the input shaft of the moving mechanism 172 can be connected to the reversible electric motor 1.
Of course, it is also possible to rotatably attach the input shaft separately from the input shaft 76 and drive the input shaft to the reversible electric motor 176. The moving mechanism 172 further includes a first movement series 180 for moving the support frame 102 in accordance with the rotation of the shaft 178, and a second movement series 180 for moving the support frame 156 in accordance with the rotation of the shaft 178. A moving train 182 is provided.

Referring to FIG. 3 in conjunction with FIGS. 2 and 7, the first movement series 180 includes the shaft 178.
It includes a pulley 184 directly fixed to the. A rope 186, which is preferably a wire rope, is wound around the pulley 184 approximately once. The pulley 184 is rotated by the reversible electric motor 176 between the angular position shown in FIG. 8-A and the angular position shown in FIG. 8-B.
In order to prevent slippage from being created between the rope 84 and the rope 186, the portion of the rope 186 that does not separate from the pulley 184 is secured to the set screw 18.
8 (FIGS. 8-A and 8-B) is advantageously secured to the pulley 184. One side of the rope 186 wound around the pulley 184 extends around a rotatably mounted guide pulley 190 and is connected to a connection fixed to a protruding piece 114 formed on one side of the support frame 102. Piece 19
2 via a tension spring 194. The other side of the rope 186 wound around the pulley 184 is connected to a guide pulley 196 rotatably mounted.
and 198 , and is connected to the connecting piece 192 fixed to the support frame 102 via a tension spring 200 . The guide pulley 190 and the guide pulley 198 are such that the rope 186 is connected to the guide pulley 1.
90 and the connecting piece 192 and the connecting piece 1
A rope 186 is guided between the guide pulley 198 and the guide pulley 198 so as to extend substantially parallel to the inclined guide rod 98 described above.

Next, referring to FIGS. 8-A and 8-B together with FIGS. 2 and 7, the second movement series 182 will be described. It includes a wheel 202, conveniently a sprocket wheel, fixed to the wheel. Further, one side 204 of a pair of side plates (the horizontal board 6 is disposed between the pair of side plates) disposed laterally at intervals within the housing 2 (FIG. 1) has a short axis. 206 is fixed,
A wheel 208, conveniently a sprocket wheel, is rotatably mounted on this short shaft 206. and the wheels 202 and 2
08 is wound with a wrapped transmission link 210, which is conveniently a chain. Above short axis 2
06 is further equipped with a cam 212 that is rotated integrally with the wheel 208. This cam 212 has two different radii on its circumferential surface.
It is composed of a cam plate having two arc-shaped working surfaces, namely a small-diameter working surface 214a and a large-diameter working surface 214b, and a transient surface 214c located between these two working surfaces. On the other hand, the side plate 158a of the support frame 156
A fan-shaped member 216 is attached to the outer surface of the fan-shaped member 216. A short shaft 218 is embedded in the fan-shaped member 216, and a roller 220 constituting a cam follower is rotatably attached to the tip of the short shaft 218. It is installed. The sector-shaped member 216 has its lower end rotatably connected to the side plate 158a through a connecting pin 222, and an arc-shaped slit 2 centered around the connecting pin 222 formed at its upper end.
By screwing a set screw 226 into the side plate 158a through 24, it is attached to the side plate 158a so as to be able to freely adjust the turning angle position about the connecting pin 222. Sector-shaped member 2 for side plate 158a
It will be apparent that changing the above-mentioned swivel angular position of roller 16 causes a change in the position of roller 220 in the longitudinal direction of guide rod 166 relative to support frame 156. In connection with the support frame 156,
The guide rod 166 has one end connected to a pair of mounting blocks 164 and the other end connected to a pair of connecting brackets 164.
A compression spring 228 acting on one of the two is also mounted. This compression spring 228 elastically forces the support frame 156 to the right in FIGS. wear.

The operation of the moving mechanism 172 as described above will be summarized as follows.

For example, when moving the support frame 102 and the support frame 156 from the same magnification position shown by the solid line in FIG. 2 to the reduced position shown by the two-dot chain line in FIG. It is rotated in the direction shown by arrow 230 (FIGS. 7 and 8-A). This causes pulley 184 of first movement series 180 to rotate in the direction shown by arrow 230. When pulley 184 is rotated in the direction shown by arrow 230, rope 186 is moved in the direction shown by arrow 230, thus causing support frame 102 to move in the direction shown by arrow 230.
is moved in the direction shown by arrow 230. When the support frame 102 is moved to the reduced position shown by the two-dot chain line in FIG.
A part 116 (FIG. 3) of the front edge of 6 is the stop piece 112.
It is brought into contact with a. On the other hand, when the support frame 102 is moved to or near the reduced position, the detection switch S2 detects the permanent magnet 120 fixed to the support frame 102. However, even if the detection switch S2 detects the permanent magnet 120, the reversible electric motor 176 is not deenergized, and the detection switch S2 detects the permanent magnet 120.
The reversible electric motor 176 is deenergized after a predetermined delay time has elapsed from the time when the permanent magnet 120 is detected by the reversible electric motor 176. Therefore, even after the support frame 102 contacts the stop piece 112a, the reversible electric motor 176 continues to be energized for a short period of time. Thus, support frame 102 cannot move further in the direction shown by arrow 230, whereas rope 186 is subjected to a force in the direction shown by arrow 230, thus causing tension spring 194
is elastically stretched, and the support frame 102 is elastically pressed against the stop piece 112a by the action of the tension spring 194, thereby ensuring that it is positioned in the desired contracted position.

Further, the reversible electric motor 176 is rotated forward and the shaft 1
78 is rotated in the direction shown by arrow 230 (FIGS. 7 and 8-A), the second movement series 1
The wheel 202 of 82 is also rotated in the direction shown by the arrow 230, and the wheel 208 is rotated in the direction shown by the arrow 230 via the winding transmission node 210. As the wheel 208 rotates, the cam 212 is rotated in the direction shown by the arrow 230 from the position shown in FIG.
12 is a large diameter working surface 214b as shown in Fig. 8-B.
is placed in an angular position that acts on the cam follower or roller 220. When the cam 212 is rotated from the angular position shown in FIG. 8-A to the angular position shown in FIG. 8-B, the action of the cam 212 causes the support frame 156 to move against the elastic biasing action of the compression spring 228. It is moved from the same magnification position shown in FIG. 8-A to the reduced position shown in FIG. 8-B, and thus
It is securely located at the reduced position shown in Figure B. The cam 212 does not need to be precisely positioned at a predetermined angular position when the reversible electric motor 176 is de-energized; as long as the large diameter working surface 214b of the cam 212 is positioned within the angular range that acts on the roller 220, the cam 212 can be supported. The frame 156 is securely positioned at the desired reduced position.

On the other hand, when moving the support frame 102 and the support frame 156 from the reduced position shown by the two-dot chain line in FIG. 2 to the same magnification position shown by the solid line in FIG. It is rotated in the direction shown by arrow 232 (FIGS. 7 and 8-B). This causes pulley 184 of first movement series 180 to rotate in the direction indicated by arrow 232. When pulley 184 is rotated in the direction shown by arrow 232, rope 186 is moved in the direction shown by arrow 232, thus causing support frame 10 to move in the direction shown by arrow 232.
2 is moved in the direction shown by arrow 232.
When the support frame 232 is moved to the same magnification position shown by the solid line in FIG.
b. On the other hand, when the support frame 102 is moved to or near the same magnification position, the detection switch S1 detects the permanent magnet 120 fixed to the support frame 102. However, even if the detection switch S1 detects the permanent magnet 120, the reversible electric motor 176 is not deenergized, and the detection switch S1
1 detects the permanent magnet 120, the reversible electric motor 176 is deenergized after a predetermined delay time has elapsed. Therefore, even after the support frame 102 contacts the stop piece 112b, the reversible electric motor 176 continues to be energized for a short period of time. Thus, while support frame 102 cannot move further in the direction shown by arrow 232, a force in the direction shown by arrow 232 acts on rope 186, thus causing tension spring 200
is elastically stretched, and the support frame 102 is elastically pressed against the stop piece 112b by the action of the tension spring 200, thereby ensuring that it is positioned at the desired same-magnification position.

On the other hand, the reversible electric motor 176 is reversed so that the shaft 1
78 is rotated in the direction shown by the arrow 232 (FIGS. 7 and 8-B), the second movement series 1
The wheel 202 of 82 is also rotated in the direction shown by the arrow 232, and the wheel 208 is rotated in the direction shown by the arrow 232 via the winding transmission node 210. As the wheel 208 rotates, the cam 212 moves from the position indicated by the arrow 2-B.
When the reversible electric motor 176 is deenergized by rotation in the direction indicated by 32, the cam 21
2 is placed at an angular position where the small-diameter working surface 214a acts on the cam driven joint, ie, the roller 220, as shown in FIG. 8-A. When the cam 212 is rotated from the angular position shown in FIG. 8-B to the angular position shown in FIG.
Due to the elastic biasing action of , it is moved from the reduced position shown in FIG. 8-B to the same magnification position shown in FIG. 8-A, and is thus reliably positioned at the same magnification position shown in FIG. 8-A. Even when the support frame 156 is positioned at the same magnification, the cam 212 does not need to be precisely positioned at a predetermined angular position when the reversible electric motor 176 is deenergized; As long as the support frame 156 is positioned within the working angular range, the support frame 156 can be reliably positioned at the required same-magnification position.

The above-mentioned moving mechanism 172 provided in the optical device 66 uses the rope 186 to move the support frame 102, which has a relatively long movement distance, and moves the support frame 156, which has a relatively small movement distance. Since the cam 212 is used for movement, the support frame 102 and the support frame 156, which must be moved in different directions, can be moved in a relatively simple manner using a single drive source (i.e., the reversible electric motor 176). and (b) it is possible, if not impossible, to precisely set the point of de-energization of the drive source (i.e. reversible electric motor 176), which can be coupled and moved as required by an inexpensive mechanism. Although it is extremely difficult, it is possible to accurately position the support frame 102 and the support frame 156 at the desired positions (i.e., the same magnification position or the reduced position) even if there is a considerable error in the time when the drive source is deenergized. It has excellent advantages such as:

Exposure correction plate As described above, the illustrated copying machine has at least two selectively set copying magnifications, more specifically, copying at substantially the same magnification and a predetermined magnification (for example, approximately 0.7 times the length ratio, The structure is such that the copying process can be carried out either by reducing the size of the copy (approximately 0.5 times the area ratio). In such a copying machine, when a copy is converted from substantially the same size to a reduced (or enlarged) copy at a predetermined magnification, the amount of exposure on the photoreceptor 10 changes, and therefore the reduction (or enlargement) is changed. ) In the case of copying, in order to obtain a good copy image as desired, the photoreceptor 10 must be
It is important to appropriately modify the exposure amount above.

This point will be explained in more detail as follows. FIG. 9-A schematically shows a state in which an original O is projected onto the photoreceptor 10 by a lens L as a projection image I of substantially equal size, projection as shown in FIG. 9-A. In this state, as is well known to those skilled in the art, light from a point p on the document O that is incident on the lens L at an incident angle α is a projected image I due to the width direction light attenuation characteristics of the lens L. At point p′ above, it is attenuated by a factor of cos ⁴ α. Therefore, in order to make the illuminance distribution in the width direction of the projected image I substantially uniform by modifying the light attenuation characteristics of the lens L, the specific illuminance Zp at the point p of the original O should be set as Zp(x)=1/ cos ⁴ α = 1/cos (tan ^-1 | 2/8-x | /2f) ⁴ ...(1) In the above formula (1), f: Focal length of lens L B: Total width of original O x: Original It must be the distance from one edge of O to point p. In order to satisfy such requirements, in the illustrated copying machine, a document illumination lamp 70 (FIGS. 1 and 4) of the optical device 66 is used.
As is well known, the luminance is gradually increased from the center in the width direction toward the side edges, and the brightness of the original O to be copied placed on the transparent plate 4 (FIGS. 1 and 4) is The projected image I is irradiated with an illuminance according to the above formula (1), thus canceling out the widthwise attenuation characteristic of the lens L.
The illuminance distribution in the width direction is made substantially uniform. Therefore, when copying is performed at substantially the same magnification, the width of the optical path from the original O to the photoreceptor 10 in the moving direction of the photoreceptor 10 (the moving direction of the transparent plate 4), that is, the slit exposure width is: The slit exposure width regulating member 84 (FIG. 1 and FIG. 4) defines a slit exposure width that is substantially the same over the entire width of the photoreceptor 10 in the width direction.

Therefore, when performing reduction (or enlargement) copying at a predetermined magnification M, in the illustrated copying machine, the lens assembly 78 of the optical device 66 is used as described above.
is moved in a direction inclined at a predetermined angle with respect to the optical axis. Therefore, a state in which the original O is projected by the lens L onto the photoreceptor 10 as a projection image I reduced (or enlarged) at a predetermined magnification M is illustrated in FIG. 9-B. FIG. 9-B shows a case where the reduced (or enlarged) projected image I is positioned in the width direction so that one side edge of the reduced (or enlarged) projection image I matches the one side edge of the same-sized projection image I.

Considering the illuminance change of the projected image I in the projection state shown in FIG. 9-B, it is as follows.
First, considering the change in illuminance caused by the displacement of the optical axis of the lens L in the width direction, the point p of the original O
The specific illuminance at point p' of the projected image I corresponding to is the lens L
For the specific illuminance Zp(x) when projected at substantially the same magnification due to the displacement of the optical axis in the width direction, Z ₁ p'(x) = Zp(x)cos(tan ^{- 1} ｜FG｜/D) ⁴ ...(2) changes. In the above formula (2), D is the distance between the lens L and the projected image I, D=f(1+M), and F is the distance from one side edge of the projected image I to the optical axis of the lens L. , F=B(1+M)/(M+1/M+2) = BM/1+M, G is the distance from one edge of the projected image I to point p', and G=M(B-x) It is.

Second, since the projected image I is M times the original O,
The point p' of the projected image I is substantially 4/ compared to the same size case.
(1+M) Due to the focusing of ^{twice as} much light and therefore the projection of M times as much, the illuminance at point p' of the projected image I is essentially the specific illuminance Zp(x) when projected at the same magnification. On the other hand, it changes to Z ₂ p'(x)=Zp(x)・4/(1+M) ² ...(3).

On the other hand, when copying is performed at a predetermined magnification M,
As already mentioned, the slit exposure speed is changed to 1/M times the speed when the slit exposure speed is substantially the same, that is, in the illustrated example, the moving speed of the transparent plate 4 (instead of moving the transparent plate, the optical device In a type of copying machine that performs slit exposure by moving at least a portion of the optical device, the moving speed of at least a portion of the optical device (moving speed) is changed to 1/M times the speed when the optical device is substantially the same size.

Therefore, M
Change twice. However, as shown in FIGS. 1 and 4, when regulating the slit exposure width between the lens L and the photoreceptor 10 using the slit exposure width regulating member 84, The optical slit exposure width with reference to the original O changes by a factor of 1/M compared to the case where it is substantially the same size, and the change in the exposure time is offset by this change in the optical slit exposure width. On the other hand, when regulating the slit exposure width between the original O and the lens L, even if the magnification M changes, the optical slit exposure width based on the original O does not change, and therefore the projected image I The specific illuminance at point p' of Z ₃ p'(x) is due to the fact that the exposure time changes by a factor of M compared to the case where the exposure time is substantially the same size. =Zp(x)・M...(4) Changes.

As described above, the specific illuminance Zp'(x) at point p' of the projected image I projected at a predetermined magnification M is, when regulating the slit exposure width between the lens L and the photoreceptor 10, Due to the changes expressed by equations (2) and (3) above, Zp'(x)=Zp(x) cos(tan ^-1 |F-G|/D ) ⁴・4/(1+M) ² ...(5) When regulating the slit exposure width between the original O and the lens L, the above equations (2), (3) and (4) are used. Due _to ^{the change expressed} by・M...Changes to (6).

In order to make the illumination in the width direction of the projected image I substantially uniform even when reducing (or enlarging) copying at a predetermined magnification M by correcting the illuminance change expressed by the above equation (5) or (6), the predetermined magnification is When reducing (or enlarging) copying with M, an exposure correction plate 150 (FIG. 2, 3 and 4) to change the slit exposure width and make the exposure amount at point p' on the projected image I substantially equal to the exposure amount when copying at substantially the same size. . That is,
By changing the slit exposure width, the point on the projected image I
The exposure amount of p′ is 1/cos(tan ^-1 |F-G|/D) ⁴・(1+M) ^2/4 or 1/cos(tan ^-1 |F-G|/D) ⁴・(1+M ) ^2/4・
Let it increase by 1/M times.

The amount of decrease (or amount of increase) in the slit exposure width for this purpose can be determined, for example, by approximate calculation using a computer according to the following theory. Explaining with reference to FIG. 10, in reality, it can be considered that the light emitted from the lens L reaches the projected image I while forming countless oblique cones, but the projected image I is In Fig. 10, the vertical direction) is divided into n equal parts (first
(In FIG. 0, the light is divided into two equal parts to simplify the explanation.) It is assumed that the light beams forming n+1 oblique cones coming out of the lens L reach the projected image I.
Then, when the slit exposure width is narrowed by v at a distance y from the lens L, the change in the total light amount of the projected image I is determined by the sum of the cross-sectional areas of each oblique cone at the distance y and the exposure correction plate 150. It is determined by the ratio to the sum of the cross-sectional areas of each interrupted oblique cone.
Assuming n=2 to simplify the explanation, the radius r of each oblique cone at the distance y from the lens L is r=(1-y/D)f/2N...(7) The above formula In (7), N is the so-called F number of the lens L, and N=f/D. Therefore, the cross-sectional area cut off at a distance y from the lens L (cross-sectional area of the shaded part) area)
S′ becomes S′=S ₁ +S ₂ +S ₃ , and S ₁ =πr ² S ₂ =∫ ^vH _2-r √ ² −(− ₂ ) ² dx S ₃ =O. However, as shown in FIG. 10, H represents the length from one end of the slit exposure width (the upper end in FIG. 10) to the center of each oblique cone at a distance y from the lens L. On the other hand, the sum S of all the cross-sectional areas of the three oblique cones at the distance y is S=3πr ² . Therefore, by reducing the slit exposure width by v, the total light amount ratio of the projected image I is S-S'/S=S-(S ₁ +S ₂ +S ₃ )/S=1/3πr ²・[
3πr ² − (πr ² +∫ ^vH _2-r √ ² − (− ₂ ) ² dx)]. Based on this principle, by increasing n to a sufficiently large value, the value of S-S'/S becomes the above-mentioned 1/cos(tan ^-1 |F-G|/D) ⁴・(1+M) ² /4(
The value of v may be determined by a computer so as to approximate the case in which the slit exposure width is changed between the lens L and the projected image I.

In the illustrated copying machine, as mentioned above, the exposure correction plate 150 is also attached to the support frame 102 on which the lens assembly 78 of the optical device 66 is attached, which can be easily understood from FIG. As shown in FIG. 4, when the support frame 102 is moved to the reduced position shown by the two-dot chain line in FIG. More specifically, between the fourth reflecting mirror 80 and the opening 82 formed in the horizontal substrate 6, the light beam enters the optical path and is partially located in the optical path. When the exposure correction plate 150 is placed in the position shown by the two-dot chain line in FIG. 4, it is regulated by the slit exposure width regulating member 84 (FIGS. 1 and 4) as shown in FIG. The slit exposure width V is partially narrowed by the partial shielding effect of the exposure correction plate 150 (this narrowing amount v is set as described above), and is thus expressed by the above equation (5). Exposure changes are fully compensated.

On the other hand, as in the case of enlarged copying, the above formula (5)
Or, if the slit exposure width V for copying at substantially the same size must be at least partially expanded in order to compensate for the exposure change expressed by (6), the slit exposure width regulation The regulation of at least one end of the slit exposure width by the member 84 (FIGS. 1 and 4) is released, and at least one end of the released slit exposure width is partially positioned in the optical path by the exposure correction plate 150. It would be better if it were regulated.

Thus, in the illustrated copying machine equipped with a preferred embodiment of an optical device constructed in accordance with the present invention, support frame 1 on which lens assembly 78 is mounted.
02 is also equipped with an exposure correction plate 150, and when the support frame 102 is moved to the position shown by the two-dot chain line in FIG. The exposure correction plate 1 is positioned in the optical path as required and therefore
It should be noted that the advantage is that no special movement and positioning mechanism for 50 is required. Furthermore, in the illustrated copying machine equipped with a preferred embodiment of an optical device constructed in accordance with the present invention, as readily understood from FIG.
It should be noted that the exposure correction plate 150 is moved into the optical path not substantially perpendicular to the optical axis, but in a direction inclined by a predetermined angle γ. When the exposure correction plate 150 is moved at a predetermined angle γ with respect to the optical axis and entered into the optical path, as can be easily understood, the amount of change in the slit exposure width is compared with the amount of movement of the exposure correction plate 150. Therefore, tolerances regarding the amount of entry of the exposure correction plate 150 into the optical path in the case of reduction (or enlargement) copying (e.g.
The slit exposure width can be changed with sufficient precision even if the allowable error in the shape of the slit itself or the entry position of the exposure correction plate 150 is made relatively large.

[Brief explanation of drawings]

FIG. 1 is a simplified cross-sectional view of a variable magnification electrostatic copying machine including a preferred embodiment of an optical system constructed in accordance with the present invention. FIG. 2 is a partial sectional view showing the main part of the optical device installed in the copying machine shown in FIG.
FIG. 3 is a partial perspective view showing one side of the support frame of the optical device installed in the copying machine shown in FIG. 1 and its related elements. FIG. 4 is a sectional view showing a part of the copying machine shown in FIG. 1. FIG. 5 is an exploded perspective view showing the lens assembly of the optical device installed in the copying machine shown in FIG. 1 and the members used for mounting the lens assembly. FIG. 6 is a partial sectional view showing how the lens assembly of the optical device installed in the copying machine shown in FIG. 1 is attached.
FIG. 7 is a partial perspective view showing the other support frame of the optical device installed in the copying machine shown in FIG. 1 and its related elements. Figures 8-A and 8-B show the first
FIG. 3 is a partial cross-sectional view showing the other side of the support frame of the optical device installed in the copying machine shown in the figure and its related elements, respectively, at a normal magnification position and a reduced position. Figure 9-A, 9th
-B and FIG. 10 are schematic diagrams for explaining changes in illuminance and correction thereof in the case of reduced (or enlarged) copying. FIG. 11 is a plan view showing an exposure correction plate of an optical device installed in the copying machine shown in FIG. 1. 4... Transparent plate, 8... Rotating drum, 10... Photoreceptor, 32... Copy paper transport mechanism, 66... Optical device, 70... Original irradiation lamp, 72... First reflecting mirror, 74... ...Second reflecting mirror, 76... Third reflecting mirror, 78... Lens assembly, 80... Fourth reflecting mirror, 102... Support frame, 150... Exposure correction plate, 156... Support frame , 172...Movement mechanism, 1
76... Reversible electric motor, 180... First movement train, 182... Second movement train.

Claims (1)

[Scope of Claims] 1. An optical device for slit exposure of a document to be copied onto a photoreceptor in a variable magnification electrostatic copying machine, comprising at least two optical devices selected according to the copying magnification.
a support frame mounted so as to be movable between different positions;
The lens includes a lens fixed to the support frame, an exposure correction plate attached to the support frame, and at least one fixed reflecting mirror, and the support frame is moved from one of the two positions to the other. and an optical device characterized in that the exposure correction plate is caused to partially enter into an optical path that is bent with respect to the optical axis of the lens by the bending action of the reflecting mirror. 2. When the support frame is at one of the two positions, the document is projected onto the photoreceptor at substantially equal magnification, and when the support frame is at the other of the two positions. 2. The optical device according to claim 1, wherein the document is sometimes reduced in size and projected onto the photoreceptor. 3. The exposure correction plate is moved in a direction oblique to the optical axis and entered into the optical path.
An optical device according to claim 1 or 2. 4. The optical device according to any one of claims 1 to 3, wherein the exposure correction plate is mounted on the support frame so that its position can be freely adjusted.