JPH0548459B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a variable magnification image forming apparatus.

In a variable magnification image forming apparatus, such as a variable magnification electrophotographic copying machine, an original image is formed by changing the position of optical members such as lenses and/or mirrors that constitute an optical system that projects and forms an original image on a photosensitive surface. It is common to change the magnification of the image. One conceivable method is to control the amount of movement of the optical member as described above by counting the pulses generated by the pulse train generating means when changing the magnification, but even if the driving means is stopped after counting a predetermined number of pulses, , the optical member may deviate from its normal position corresponding to the selected magnification due to the inertial force of the optical member and stop, or the discrepancy between the number of pulses and the amount of rotation of the drive means may occur due to uneven rotation of the drive means, etc. A deviation from a predetermined relationship may occur, causing the optical member to deviate from the normal position and stop. In this way, as the magnification changing operation is repeated many times, the deviations described above accumulate, and it becomes impossible to form an original image of the required magnification on the photosensitive surface, or the focus state of the image goes out of the permissible range. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a variable magnification image forming apparatus that solves the above-mentioned disadvantages.

In order to achieve the above object, the present invention includes a lens that focuses an original image on a photoreceptor, and a pulse train generating means that generates pulses, and the number of pulses generated by the pulse train generating means is adjusted according to a change in magnification. In a variable magnification image forming device that controls the movement of a lens by counting with a counter, there is provided a detection element provided at the end of a lens movement path that detects when the lens reaches a reference position, and a magnification changing means that changes the magnification. , comprising a measuring means for measuring the number of magnification changes by the magnification changing means from the time of detection by the detecting element, and a comparing means for comparing a predetermined number of times set in advance with the number of times measured by the measuring means. If the comparison means determines that the number of times measured by the measuring means is greater than the predetermined number of times, the lens is moved to the reference position and the counter is set to a new value based on the detection signal from the detection element. The lens is reset to the number of pulses, and by counting the new number of pulses, the lens is moved from the reference position to a predetermined position determined by the magnification changing means.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram of a variable magnification electrophotographic copying machine to which the present invention can be applied. In the figure, reference numeral 1 denotes a photosensitive drum having an electrophotographic photosensitive member on its circumferential surface, which rotates in the direction of the arrow. As the drum 1 rotates, it is first uniformly charged by a corona discharger 2, and then an optical image of a document O at a selected magnification is slit-exposed through a slit 3 by an optical system to be described later. The electrostatic latent image thus formed on the drum 1 is developed by the developing device 4, and a toner image is obtained. This toner image is then transferred under the action of a transfer corona discharger 5 to a transfer paper P that is conveyed in the direction of the arrow. This transfer paper P is then sent to a fixing device 6, and the transferred toner image is fixed on the paper P. On the other hand, the drum 1 after the transfer is cleaned by a cleaning device 7 and used again for the image forming process.

The original O is placed on a fixed transparent original table 8. This original O is illuminated by a lamp 9, and the light reflected from the original is reflected by mirrors 10, 11, 1.
2 are sequentially reflected and incident on the zoom lens 13.
The imaging light beam from the document exiting the zoom lens 13 is reflected by the mirror 14 and enters the photosensitive drum 1 as described above, forming an optical image of the document O at a selected magnification. When the lens 13 is at the solid line position 13 ₁ in the figure, an m ₁ times image of the document is formed on the drum 1, and when the lens 13 is moved to the 13 ₂ position, an m ₂ times image is formed.
When moved to the ₁₃₃ position, an _m3 magnification image is formed.
Here, it is assumed that m ₁ > m ₂ > m ₃ . For convenience, in the example
Although the description will be made assuming that m ₁ =1, the present invention can also be applied to an apparatus that can copy an enlarged image of a document. Furthermore, 13 ₄
is the reference position of the lens 13.

When the position of the zoom lens 13 is changed as described later, zooming is performed in conjunction with this, and the lens focal length is changed to a value corresponding to the new lens position, in other words, a value corresponding to the selected copy magnification. Ru.

Here, the sum of the optical path length l ₁ between the original and the lens and the optical path length l ₂ between the lens and photoreceptor is l (l is constant), and the imaging magnification of the original image (i.e., the selected copying magnification) is m , the lens focal length is f, then the position and focal length of the lens are adjusted according to the selected magnification m so that l ₁ = l/m+1 l ₂ = ml/m+ ¹ f=ml/(m+1) 2 Just change it.

The apparatus shown in FIG. 1 is of an original scanning type. In order to scan the original, the mirror 10 is integrated with the lamp 9 in the direction of the arrow, and the peripheral speed of the drum 1 is multiplied by the reciprocal of the selected copying magnification, 1/m, in order to set the copying magnification in the direction of rotation of the drum to m. The mirrors 11, 1
2 moves in the direction of the arrow at half the speed of the mirror 10 in order to keep the optical path length between the original and the lens constant. The original O is thus scanned, and its image is slit-exposed onto the drum 1. When scanning of the original is completed, member 9
-12 move backward and return to their respective forward movement starting positions.

FIG. 2 shows the movement and zooming mechanism of the lens 13. In the figure, 15 is the zoom lens 13.
It is a lens barrel with a built-in. This lens barrel 15 is fixed to a lens stand 16. Slide bearings 17 and 18 are fixed to the lens stand 16, and these bearings 17 and 18 are slidably fitted into a linear guide rail 19 fixed to a substrate 20. Therefore, the lens stand 16 on which the lens 13 is mounted can reciprocate under the guidance of the guide rail 19 in directions parallel to the guide rail (direction A, direction B). Although the direction of the rail 19 and therefore the direction of movement of the lens 13 are inclined with respect to the optical axis X of the lens 13, even when copying at such a magnification, the side edge of the document is set as the reference edge of the document table 8. This is to align the image of the document side edge to the reference position of the photoreceptor side edge. Therefore, in a copying machine in which the center of the document is placed at the center of the document table when copying at any magnification, and the image of the center of the document is formed at the center of the photoreceptor, the rail 19 is placed parallel to the optical axis X. You may.

Both ends 21' of the wire 21 are attached to the lens stand 16,
21'' is locked. The wire 21 is connected to the board 20
It is hung around pulleys 22 and 23 that are rotatably supported by shafts 22' and 23' fixed to the drive pulley 24, and is wound around a drive pulley 24 several times between the pulleys 22 and 23. This drive pulley 24 is connected to the shaft 2 through a torque limiter 25, an example of which is shown in FIG.
It is attached to 6. A worm wheel 27 is fixed to this shaft 26, and is engaged with a worm gear 28 fixed to an output shaft 30 of a motor 29. When the motor 29 rotates forward, the shaft 26 is rotated clockwise by the worm gear 28 and the worm wheel 27, and the torque limiter 25 rotates between the shaft 26 and the pulley 24.
When fixedly connected, this pulley 24 rotates clockwise, so the lens stand 16 on which the lens 13 is mounted is indexed by the wire 21 and moves in the direction of arrow A. Similarly, when the motor 29 reverses, the pulley 24
is rotated counterclockwise, and the lens stand 1
6 is indexed by the wire 21 and moves in the direction of arrow B.

A disk 31 as shown in FIG. 3 is fixed to the output shaft 30 of the motor 29. As shown in FIG. Therefore, this disc 31 rotates in synchronization with the shaft 26, and therefore, when the shaft 26 and the pulley 24 are fixedly connected by the torque limiter 25, as is clear from the above, the disc 31 rotates in synchronization with the shaft 26. rotates in synchronization with the movement of the lens stand 16 on which the lens 13 is mounted.

The disc 31 is an opaque disc 3 as shown in FIG.
1', a large number of light transmitting slits 3 of equal width are spaced at equal intervals.
1'' and 32 is the substrate 20.
The light emitting element section 32' and the light receiving element section 32'' are arranged with the slit forming area of the disk 31 in between. 31, the emitted light from the light emitting element section 32' reaches the slit 3.
1'' periodically, the light receiving element section 32'' periodically generates electric pulses. Therefore, the rotation angle of the shaft 26 that rotates during one pulse period of this pulse train is the same at any time, and therefore the amount of movement of the lens stand 16 on which the lens 13 is mounted during the above-mentioned one pulse period is the same at any time. . During the magnification changing operation, when the motor 29 is driven, the lens 13 starts to move as described above, and in synchronization with this, the above pulse train starts to be generated.As will be described later, the number of these pulses is counted and the selected When the number of pulses corresponding to the magnification is counted, the motor 29 is deenergized and lens movement is stopped. Therefore, lens 1
3 moves by a distance corresponding to the selected magnification.

As mentioned above, the lens 13 is a zoom lens,
In the embodiment shown in FIG. 2, zooming of the lens is performed in conjunction with the lens movement. That is,
The lens barrel 15 is provided with a cam hole 15', and a lens holding tube for changing the focal length, which is movable in the optical axis direction inside the lens barrel 15, is fixed to the cam hole 15'. A pin 33 is engaged and protruded. 34 is the lens barrel 15, the lens barrel 1
Although it does not move relative to 5 in the optical axis direction, the optical axis
This is a zoom ring that is rotatable around the center. The zoom ring 34 is provided with a long hole 34', and the pin 33 is engaged with this long hole 34'. Therefore, when the zoom ring 34 is rotated, the pin 33 moves along the cam hole 15'.
As a result, the distance between predetermined lens elements within the lens barrel 15 changes, so the focal length of the lens 13 also changes. The mechanism for rotating the zoom ring 34 is as follows.

That is, the wire 35 is wound around the zoom ring 34 once to several times. 36 is a wire support member slidably attached to the lens stand 16, one end 35' of the wire 35 is locked to one end of the support member 36, and the other end 35'' of the wire 35 is used to prevent loosening. Support member 36 via tension spring 37
is connected to the other end. A linear guide rod 38 extending perpendicular to the optical axis X is fixed to this support member 36, and this rod 38 is slidably inserted into slide bearings 39, 40 fixed to the lens stand 16. ing.

Therefore, the wire support member 36 moves relative to the lens stand 16 in the direction perpendicular to the optical axis X, and this movement drives the wire 35, so that the zoom ring 34
rotates. Here, a cam follower 41 is fixed to the wire support member 36, and this follower 41 is a cam groove that is provided in a cam plate 43 fixed to the substrate 20 and has a long cam groove in a direction inclined with respect to the lens movement direction. 42. Therefore, if the lens stand 16 on which the lens 13 is mounted is moved as described above, the wire support member 36 will move relative to the lens stand 16 under the control of the cam 42 as described above, and the zoom ring 34 will thereby move. Since it rotates, the focal length of the lens 13 is changed. As can be seen from the above, the amount of lens movement and the amount of lens zooming correspond. The shapes and installation directions of the cams 15' and 42 are set so that the three equations described above hold between the lens position and focal length.

Now, 44 is a stopper fixed to the board 20.

In FIG. 2, this stopper 44 is provided at one end of the lens moving path. When the lens stand 16 moves in the direction of arrow A and reaches its movement end position, the side surface 18' of the bearing 18 mentioned above comes into contact with the side surface 44' of the stopper 44, and the lens stand 16 moves further in the direction of arrow A. Movement is prevented. The bearing 18 of the lens stand 16 is connected to the stopper 4 as described above.
4 is the reference position of the lens stand 16. In other words, the position of the lens 13 in this state (13 in Fig. 1) is the reference position of the lens stand 16.
₄ ) is the reference position of the lens 13. A microswitch 45 is fixed to the stopper 44, and the side surface 18' of the bearing 18 comes into contact with the actuator of the microswitch 45 when the bearing 18 comes into contact with the stopper 44. In other words, when the lens stand 16 comes to the reference position,
In other words, when the lens 13 comes to the reference position ₁₃₄ ,
The micro switch 45 issues a signal.

As described above, when the motor 29 is rotated in the forward direction to continue moving the lens in the direction of arrow A, the microswitch 45 issues a signal after a certain period of time has elapsed. This signal is a signal indicating that the lens 13 has reached the reference position as described above, but if the motor 29 is deenergized and the driving of the lens stand 16 is stopped at the same time as this signal is generated, the lens 13 There is a possibility that the robot stops at a position deviated from the reference position ₁₃₄ . This may be due to an error in the mounting position of the switch 45, an error in the operating timing of the switch 45, or an error in the bearing 18 and stopper 4.
This is because the platform 16 may be displaced in the direction B due to the reaction from the collision of the vehicle. In any case, if the lens 13 stops at a position deviated from the reference position ₁₃₄ , when the lens 13 is moved from this position a distance corresponding to the number of pulses corresponding to the selected magnification, the new lens position will be This results in a position deviated from the position 13 ₁ , 13 ₂ , or 13 ₃ corresponding to the selected magnification, and a copy with the desired magnification cannot be obtained. Therefore, in the embodiment shown in FIG. 2, a torque limiter 25 is provided in the drive force transmission path to the lens stand 16, and
continues to operate the motor 29 until some time after the time when the signal is formed, thereby causing the bearing 18 to
The motor 29 is deenergized after the lens 13 is securely pressed against the stopper 44 (that is, after the lens 13 is securely stopped and held at the reference position ₁₃₄ ). In addition to the switch 45 shown in the illustrated example, as a means for detecting the position of the lens, it is also possible to use a device in which a magnet is attached to one of the lens stand 16 and the stopper 44, and a Hall element is attached to the other. The signal generated by the Hall element at the time can be used in the same way as the signal from the microswitch 45.

Figure 4 shows an example of a torque limiter. Fourth
In the figure, a shaft 26 to which a worm wheel 27 is fixed is rotatably supported by bearings 46 and 47 fixed to the substrate 20. A flange 26' is integrally provided on this shaft 26. Also, the shaft 26
A perforated disk 48 is loosely fitted in the . The base of the pulley 24, the shaft 26, the flange 26', and the disc 4
8, spacers 49, 50, and 51 are interposed between them. And another one on the disk 48 and the shaft 26.
A compression spring 53 is interposed between the perforated discs 52 that are loosely fitted. Numeral 54 is a nut screwed onto a screw provided on the shaft 26 to receive the disc 52. By adjusting the nut 54, the spring 53
The pressing force applied to the disc 48 can be adjusted.

In any case, due to the elastic pressing force of the spring 53, the disk 48 and the spacer 51, the spacer 51 and the pulley 24
, the base of the pulley 24 and the spacer 50, and the spacer 50 and the flange 26' are brought into pressure contact.
Therefore, unless a load exceeding a predetermined value is applied to the wire 21, the shaft 26 and the pulley 24 are fixedly connected, and when the wheel 27 is driven to rotate, the pulley 24 also rotates integrally with the shaft 26, and as described above, the lens is Direction, B
move in the direction. However, when the motor 29 is rotated in the forward direction with the bearing 18 of the lens stand 16 in contact with the stopper 44 as described above, that is, when the lens stand 16 is further moved in the direction of arrow A, the load applied to the wire 21 is Since the above predetermined value is exceeded, the shaft 26, flange 26', and disc 48 that are in contact with the spacers 49, 50, and 51, respectively.
As a result, the worm wheel 27 only rotates integrally with the shaft 26 while the pulley 24 remains stationary. In other words, the motor 29 idles. Accurate positioning of the lens 13 at the reference position 13 ₄ is thus guaranteed.

Incidentally, in cases where accurate positioning and accurate operation timing of the lens position detection means are guaranteed, and it is guaranteed that there will be no reactionary displacement when the platform 16 collides with the stopper 44, the torque limiter may be omitted. The transmission of the driving force to the lens stand 16 may be stopped immediately when the microswitch 45 issues the signal.

Next, the operation of the above mechanism will be explained. A microcomputer is used for operation control. That is, as shown in Fig. 5, a one-chip microcomputer
The MC includes a copy key SWC that instructs the copying machine to perform a copy operation, and an m _1x key SW that instructs the copy magnification _m1 .
1. Specify the copying magnification m _{2 2x} key SW2, specify the copying magnification m _{3 3x} key SW3, signals from the pulse train generator 32 and lens position detector 45 are applied, and the motor 29 rotates forward. Drive circuit DA
It outputs a signal to energize the motor 29, a signal to energize the drive circuit DB to reverse the motor 29, and various signals to cause the copying machine to perform a copying operation. When the signal is at H level, the circuit DA is energized and the lens 13 moves in the direction of arrow A in FIG. Also, when the signal is at H level, the circuit DB is energized, and the lens 13 is connected to the arrow B in Fig. 2.
move in the direction. When the signal is at L level, the circuit
DA and DB are not energized and the lens 13 is stopped. In addition, by outputting a signal, the driving means for the photosensitive drum 1, the driving means for the chargers 2 and 5, the driving means for the developing device 4, the driving means for the fixing device 6, the driving means for the lamp 9, and the driving means for the mirrors 10, 11, and 12 are driven. means, paper P
transport drive means (all the above drive means together)
(hereinafter referred to as a CD) is energized according to a predetermined sequence, and the copying process described in FIG. 1 is performed to form a copy image from the original O onto the paper P.
Since the sequence of the copying process in which each driving means CD operates can be a known one, the description thereof will be omitted in this specification to avoid complexity.

The microcomputer MC also has a counter TN1 function that counts the number of pulses generated by the pulse train generator 32, and a counter TN2 function that counts the number of times the lens is moved to change the magnification.

Furthermore, as shown in Fig. 7, the lens is at the reference position 1.
The pulse train generator 32 generates P ₁ pulses to move from 3 ₄ to the position 13 ₃ at the time of m ₃ times copying,
P ₂ pulses are generated to move from position 13 ₃ to position 13 ₂ during _double copying, and from position 13 ₂
Assume that P ₃ pulses are generated to move to the position 13 ₁ when m is _1x copying.

Now, what is shown in FIGS. 6A, B, and C is a flowchart of the control software by the microcomputer MC. In FIG. 6A, when the power is connected to the copying machine (power ON), whether or not the lens 13 is located at the reference position ₁₃₄ is determined depending on whether or not the micro switch 45 is forming a signal. Make a judgment (Step S ₁ ), and if Yes, proceed to Step S ₄ .
However, if NO, the signal is set to H level and the lens 13 is moved in the direction of arrow A (step S ₂ ).

When it is determined from the signal from the micro switch 45 that the lens 13 has reached the reference position ₁₃₄ (step _S3 ), the counter TN2 is first cleared (step _S4 ), and then the number of pulses P is set in the counter TN1. Set ₄ pieces (step
_S5 ). This means that the bearing 18 is connected to the micro switch 4.
This is to continue driving the motor 29 in the normal rotation until a time point corresponding to the number of pulses P ₄ from the time when the pulse number P 5 is applied, and to accurately hold the lens 13 at the reference position ₁₃₄ as described above. (Therefore, _P4 does not need to be a very large value; it is selected to be as small as possible within the range that allows accurate positioning of the lens 13 at position _134. ) For this reason, after step _S5 , the counter TN1 is It is determined whether or not there is a pulse input from the pulse train generator 32 (step _S6 ), and the counter TN
Each time a pulse enters 1, the counter TN1 is decremented (step _S7 ).

In this way, it is determined whether TN1=0 or not, that is, after the micro switch 45 issues a signal.
It is determined whether the time corresponding to the number of _P4 pulses has elapsed (step _S8 ), and if yes, the signal is set to L level and the drive of the motor 29 is stopped (step _S9 ). Next, the counter TN2 is set to 1 (step _S10 ). This counter TN2 is a coefficient indicating how many times the lens 13 has been moved and positioned to the position 13 ₁ or 13 ₂ or 13 ₃ (that is, each position when the copying process is performed), and the number of times this positioning is α (for example, 5 times, etc.). (the number of times is selected depending on the desired imaging magnification accuracy, positioning error at each position, etc.), the lens 13
This is to temporarily return to the reference position 13 ₄ and move from that position to the position 13 ₁ or 13 ₂ or 13 ₃ corresponding to the selected magnification. Therefore, in the embodiment, this counter TN2 corresponds to the lens 1.
3 to the above-mentioned position 13 ₁ or 13 ₂ or 13 ₃ , the movement is counted as one time. In any case, after step _S10 , the number of counting pulses ( _P1 + _P2 + _P3) required to move the lens 13 from the reference position ₁₃₄ to the position 131 for forming a ₁ -magnification image is set. (step)
_S11 ). Next, the signal is set to H level and the lens 13 starts moving from position ₁₃₄ in the direction of arrow B (step _S12 ). Then, it is determined whether the lens is at position _13-4 (step _S13 ), and then the counter
It is determined whether or not TN1 has an input from the pulse generator 32 (step _S14 ), and if this input is received, counter TN1 is decremented (step _S15 ), and then counter TN1 is set. It is determined whether all the pulse numbers (P ₁ +P ₂ +P ₃ ) have been counted (step S ₁₆ ). When it is determined that TN1=0 in this step _S16 , the lens has reached the ₁₃₁ position, so the signal is then set to L level, the motor 29 is stopped, and the lens movement is stopped (step _S17 ). . Thus, when the power is turned on to the copying machine, the lens 13 first moves to the reference position 13.
₄ , and is moved and stopped from that position to position ₁₃₁ for full size copying. Therefore, when the copy key SWC is turned on next time, an exact same-size image of the original can be copied. (Note that the highest copying frequency is same-size copying.) Now, the operator presses the keys SW1, SW2, and SW3.
Turn on the desired magnification designation key. Therefore, the microcomputer MC next determines whether or not there is a magnification designation key input in step _S18 .
If No, the process goes to step _S20 described later, but if Yes, the process goes to step _S19 to determine whether the current position of the lens corresponds to the selected magnification designation key or not. It is determined whether it is necessary to move the lens to a position corresponding to the magnification, and if No, the process returns to step _S18 . Again in step _S18 , it is determined whether or not there is a magnification specifying key input, but at this time, since this input information has already been determined and deleted, the determination is No and the process goes to step _S20 . step
In _S20 , it is determined whether or not the copy key SWC has been turned on. If Yes, the above-mentioned copying step _S21 is executed by the signal, but if No, the step S21 is executed.
Return to _S18 . Therefore, steps S ₁₈ and S ₂₀ are repeated until the next time the copy key SWC is turned on or the magnification designation key is turned on.

On the other hand, if it is determined in step _S19 that it is necessary to move the lens 13, a counter is set in step _S22 .
The counter TN2 is incremented, and then a comparison means (not shown) compares and determines whether the count number of the counter TN2 has reached (α+1) (step S ₂₃ ).

If it is determined that TN2 = (α+1) here, the operation of moving the lens to the 13 ₁ , 13 ₂ , or 13 ₃ position has already been performed α times, so the operation shown in Figure 6C System, the lens 13 is once returned to the reference position ₁₃₄ , and then moved from that position to the position designated by the magnification designation key. However, if the answer is No in step _S23 , the process moves to step _S24 in FIG. 6B, where the lens is moved to position 1.
Determine whether or not to move the lens from position ₁₃₁ to position _132. If no, move the lens from position ₁₃₁ to position ₁₃₂ in step _S25 .
If the answer is No, it is further determined in step _S26 whether the lens should be moved from position ₁₃₂ to _{position 133} . Steps S ₂₄ , S ₂₅ and S ₂₆ are all for determining whether or not to move the lens in the A direction. Then, if Yes in step _S24 , count pulse number _P3 , if Yes in step _S25 , count pulse number ( _P3 + _P2 ), and if step _S26 Yes, count pulse number _P2. are set in the counter TN1, respectively (steps S ₂₇ , S ₂₈ , S ₂₉ ).

Next, set the signal to H level and turn the lens 13
starts moving in the direction A from its current position (step S ₃₀ ), and executes steps S ₃₁ , S ₃₂ , S ₃₃ , and S ₃₄ similar to steps S ₆ , S ₇ , S ₈ , and S ₉ . Then, the lens 13 is moved a distance corresponding to the number of pulses set in the counter TN1. That is, the lens 13 is moved to a position corresponding to the magnification designated by the magnification designation key and stopped. When this is completed, the program jumps to the location shown in FIG. 6A.

On the other hand, if the answer is No in step _S26 , the remaining case is to move the lens 13 in the B direction. Then, in step _S35 , it is determined whether or not to move the lens from position ₁₃₂ to position ₁₃₁ (step _S35 ).
If the answer is No, it is determined whether or not to move the lens from position ₁₃₃ to position ₁₃₁ (step _S36 ).
If so, it is required to move the lens from position 13 ₃ to 13 ₂ , so the counter TN
Set the counting pulse number P to 1 to ₂ (step
_S30 ). On the other hand, if the answer is Yes in step _S35 , the number of counted pulses _P3 is set in the counter TN1, and if the answer is Yes in step _S36 , the number of counted pulses ( _P2 + _P3 ) is set in the counter TN1 (steps _S37 , _S38 ). Next, in step _S40 , the signal is set to H level, and the lens 1
3 starts moving in the direction of arrow B from its current position. Then, steps S ₄₁ , S ₄₂ , S ₄₃ , and S ₄₄ similar to steps S ₁₄ , S ₁₅ , S ₁₆ , and S ₁₇ are executed to move the lens 13 a distance corresponding to the number of pulses set in the counter TN1. . In other words, lens 1
3 is moved to a position corresponding to the magnification designated by the magnification designation key and stopped. When this is completed, the program jumps to the location shown in FIG. 6A.

Next, if the answer is Yes in step _S23 of FIG. 6A, the process moves to step _S45 of FIG. 6C, and the lens 1
3 in the A direction, and the following steps S ₂ ,
Steps similar to S ₃ , S ₄ , S ₅ , S ₆ , S ₇ , S ₈ , S ₉ , S ₁₀ S ₄₅ , S ₄₆ , S 47 , S ₄₈ , S ₄₉ , S ₅₀ , _{S 51 ,} S ₅₂ ，
Repeat _S53 to accurately position the lens at the reference position ₁₃₄ , and set the counter TN2 to an initial value of 1. Incidentally, in step _S48 , a new number of pulses is set again, that is, TN2 is reset to the new number of pulses. Next step S ₅₃
At this point, determine whether or not to move the lens to the ₁₃₃ position.
If No, in step _S35 , remove the lens from 13 ₂
If the answer is No, the lens is to be moved to the ₁₃₁ position, so in step _S58 the counter TN1 is set to the number of counted pulses (P ₁ + P ₂ +
_P3 ). On the other hand, in the case of Yes in step _S54 and in the case of Yes in step _S55 , the counted pulse numbers P ₁ and (P ₁ +P ₂ ) are set in the counter TN1 in steps S ₅₆ and S ₅₇ , respectively. Then, in step _S59 , the signal is set to H level to start moving the lens 13 from the reference position ₁₃₄ in the direction B.
Steps similar to steps S ₁₄ , S ₁₅ , S ₁₆ , S ₁₇
S ₆₀ , S ₆₁ , S ₆₂ and S ₆₃ are executed to move the lens 13 from the distance reference position 13 ₄ corresponding to the number of pulses set in the counter TN1. In other words, move the lens 13 to the position specified by the magnification specifying key.
Move and stop from reference position 13 ₄ . When this is completed, the program jumps to the state shown in FIG. 6A.

When jumping after steps S ₃₄ , S ₄₄ , and S ₆₃ , the magnification specifying key is pressed during the movement of the lens.
Step S ₁₈ and Step
S ₂₀ is repeated. And copy key SWC is ON
Then, a copying step _S21 is performed to form a copy image at the selected magnification. If the magnification specifying key is turned ON again at another location during the lens movement operation, the process moves to step _S22 via steps _S18 and _S19 , and the above-described control is performed.

In the above example, the lens is returned to the reference position after multiple magnification changing operations, but if you do not mind that it takes time to change the magnification each time, it is necessary to return the lens to the reference position after each magnification changing operation. It may be possible to return to the reference position for accurate positioning, and then move to a position corresponding to the selected magnification. For this purpose, steps S ₄ , S ₁₀ , S ₂₂ , S ₂₃ of the program flowchart described above can be used, for example.
(thus, the function of counter TN2 is removed from the microcomputer _CPU ), and step _S19
If Yes, immediately proceed to step S ₄₅ in Figure 6C.
All you have to do is connect it to .

Further, in the above example, the end of the lens movement path is set as the reference position for the lens, but a position between both ends of the lens movement path may be set as the reference position. In this case, the stopper that stops the lens at its reference position is moved in and out of the lens table movement path using a solenoid or the like, and when the lens is once positioned at the reference position, the stopper is inserted into the path and engages the lens table. make it stop.

Furthermore, in the above example, the reference position of the lens was set to a position other than the lens position used in the copying process, but the lens position used in the copying process may be used as the reference position. For example, if the lens is placed at the 13 ₄ position, it may be possible to obtain m ₄ times as many copied images.

In the above embodiment, the magnification can be changed in 3 to 4 stages, but the present invention can also be applied to a copying machine capable of copying at other magnifications, or can change the magnification in a very large number of stages. The present invention can also be applied to an apparatus capable of changing the magnification, that is, an apparatus capable of substantially steplessly changing the magnification.

Further, in the embodiment described above, a means for generating a pulse train using a slit disk rotated by a motor was used, but other clock pulse generators or the like may also be used. In this case, the motor 29 may be a pulse motor whose rotation is controlled by the clock pulse oscillator.

Furthermore, in the above embodiment, the movement and stopping of the lens was controlled by energizing and deenergizing the motor 29, but a clutch is provided between the motor 29 and the worm gear 28, etc., and the lens is controlled by energizing and deenergizing the clutch. Movement and stopping may also be controlled.

Further, although a zoom lens was used as the lens in the above example, the present invention can also be applied to an apparatus using a fixed focus lens. In that case, when changing the magnification, it is necessary to change the total optical path length between the original and the photosensitive surface.
2 or the position of the mirror 14 may be changed in accordance with the selected magnification. The present invention can also be applied to changing the mirror position as described above.

Furthermore, the present invention is applicable to a device of the type that scans the document by moving the document table or by moving the document using a document transport roller, a belt, etc., or a device of the type that scans the document by moving the document table or by moving the document using a document transport roller, a belt, etc. It can also be applied to equipment.

The present invention can also be used in digital copying machines, facsimile machines, etc., which form an original image on a CCD or the like to once form an electrical signal corresponding to the original image, and then use that electrical signal to form a desired image. be.

In any case, according to the present invention, in a device that controls the amount of movement of an optical member by counting pulses when changing the magnification, the optical member is temporarily returned to the reference position after the magnification changing operation is performed at least a plurality of times. After that, the optical member is moved, so the number of counted pulses, the position of the optical member moved corresponding to the number of pulses, and the selected magnification are accurately correlated, and accurate It is possible to form an original image with high magnification and focus.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an example of a variable magnification electrophotographic copying machine to which the present invention is applied, FIG. 2 is an explanatory diagram of an example of a lens moving mechanism of the apparatus shown in FIG. 1, and FIG. 3 is an explanatory diagram of an example of a slit disk. 4 is an explanatory diagram of an example of a torque limiter, FIG. 5 is a block diagram of a control system according to an embodiment of the present invention, and FIGS. 6A, B, and C are explanatory diagrams of software of the control system of FIG. The flowchart, FIG. 7, is an explanatory diagram of the number of pulses for lens movement. O is an original, 1 is a photosensitive drum, 13 is a zoom lens, 15 is a lens barrel, 16 is a lens stand, 19 is a guide rail, 21 is a drive wire, 24 is a drive pulley, 25 is a torque limiter, 26 is a drive shaft, 2
7 is a worm wheel, 28 is a worm gear, 2
9 is a motor, 31 is a slit disk, 32 is a photocoupler, 34 is a zoom ring, 44 is a stopper, 45
is a micro switch.

Claims (1)

[Claims] 1. A lens that forms an original image on a photoreceptor, and a pulse train generating means that generates pulses, and a counter counts the number of pulses generated by the pulse train generating means in accordance with a change in magnification. In a variable magnification image forming device that controls the movement of a lens by A measuring means for measuring the number of magnification changes by the magnification changing means from the time of detection by the element, and a comparing means for comparing a predetermined number of times set in advance with the number of times measured by the measuring means. If it is determined that the number of pulses measured by the measuring means is greater than the predetermined number of pulses, the lens is temporarily moved to the reference position and the counter is set to a new number of pulses based on the detection signal from the detection element. A variable magnification image forming apparatus characterized in that the lens is reset and the lens is moved from a reference position to a predetermined position determined by a magnification changing means by counting the new number of pulses.