JPS59142535A - Variable power optical device - Google Patents

Abstract

PURPOSE:To execute scanning corresponding to many kinds of sizes and magnifications by only a few position sensors by providg a means for generating a pulse in accordance with a scanning distance on an optical system scanning means, counting its pulse number, and controlling the scanning. CONSTITUTION:An advance clutch is put on, a driving reel 20 starts its rotation, and an optical system 29 starts its scanning. A pulse number from a disk 23 for generating one pulse in accordance with a scanning distance 1cm is counted by a sensor 24. When five pulses are counted, the preliminary running is ended, it is decided that the scanning speed has completed a rise, and the operation is shifted to the image exposure. In case of an A4 size original, when 21 pulses are counted, it is decided that the exposure is ended, and the scanning system is re- operated by switching to a retreat clutch. The retreat speed is decreased by an operation of the sensor S2, and it is decided that the optical system 29 is returned to the start position by an operation of the sensor S1, and the retreat clutch is cut off.

Description

[Detailed description of the invention] The present invention relates to a variable magnification optical device.

Generally, in a slit exposure type electrophotographic copying apparatus having a variable magnification copying function, the position, moving distance, speed, speed of the photoreceptor, charging conditions, etc. of each scanning member of the optical system are changed according to the magnification, and - The scanning conditions (hereinafter referred to as stroke) of the member during copying are determined and controlled. Conventionally, in order to determine this stroke, the stroke of the scanning member is controlled by arranging a number of position sensors relative to the scanning member, or by calculating the selected magnification, document size, etc. However, recently there has been a demand for copiers that have more variable magnification functions and even more types of variable magnification functions that can accommodate more types of document sizes. Due to the demand for higher speeds, the number of position detection sensors is increasing, and the computing devices are becoming more complex. Therefore, satisfactory results cannot be obtained under all scanning conditions.

The purpose of the present invention is to eliminate the drawbacks of the above-mentioned conventional example.
means for detecting the position of a reciprocating scanning member of the optical system;
The purpose is to detect the position of the scanning member and control its movement by means of the scanning member or the pulse generating means disposed in the means for driving the scanning member, and the scanning member can be controlled during various types of magnification changes. enable.

An embodiment of the present invention will be described below with reference to the drawings. 1st
FIG. 1 is a schematic front sectional view of a stationary original table copying machine to which an embodiment of the present invention is applied. When a document P is placed on the document table and a copy start button (not shown) is pressed, the electrophotographic photosensitive drum starts rotating clockwise in the figure. Then,
The first mirror 3, which is a movable part of the optical system, scans the document in the right direction in the figure at a speed equal to the circumferential speed of the photosensitive drum multiplied by the reciprocal of the selected copying magnification, and the second mirror 3 moves the document to the right in the figure at the speed of that part. Start moving for the purpose. The original image is then transferred to the first mirror 3. The third lens is moved along the optical path to a position corresponding to the selected magnification, and the focal length is changed to correspond to the selected magnification. The image is formed on the imaging section g on the drum controller. 3. The first mirror 3 and the second mirror are each shown in the figure/indicated by the dotted chain line. When the exposure is completed by moving to the `` and '' positions, it starts moving in the opposite direction, that is, to the left in the figure. On the other hand, the photosensitive drum is first positively charged by the primary charger 9, and when it reaches the imaging section, an electrostatic latent image corresponding to the original image is formed by projecting the original image! This latent image is developed with toner by developer/2 and made into a visible image.

Next, the sheet ° fed from the paper feed section /3 is brought into close contact with the photosensitive drum, and the visible image on the drum is transferred by the transfer charger /q. After the transfer, the sheet is separated from the drumco, guided and conveyed through a conveyance unit (15), fixed by a fixing device (B), and further discharged to a sheet tray (7). Further, the surface of the drum after transfer is wiped of residual toner by a cleaning device/g, and is prepared for the next cycle.

In order to stabilize the image quality, the copying machine with a stationary document table starts exposure (that is, starts scanning the document P) after the speed of the optical means becomes constant. That is, as will be described later, the distance from the movement start position of the first mirror 3 to the document scanning start position (hereinafter referred to as the distance).

This is called the run-up distance. ) is set so that scanning of the original is started after the optical means has moved a distance longer than the distance required to reach a predetermined speed.

FIG. 2 is a detailed front view of the optical scanning device of FIG. 1. The first mirror 3 is supported by a first mirror 29 in a tilted position at a required constant angle with respect to the horizontal, and the second mirror 3 is supported vertically by a second mirror 30. There is. 1st Mira 29. One end of the No. 1 Comilla machine 30 is connected to a parallel guide rod 3 fixed to the main body of the copying machine.
3.3'1, and the other ends of the first mirror 2z and the second mirror 30 are also slidably fitted to a similar guide rod (not shown). There is. 1st and 2nd Mira 30
A rotatable movable pulley 27 is fixed to the. To the left of the guide rod 33.3'l are the movement ranges of the first mirror 29 and the first comirror 30 (a movement distance sufficient for the mirrors to scan the maximum document specified by the copier specifications). and
Defined at the time of design. ) A first fixed pulley 2/ is rotatably mounted on the copying machine main body to the left of the mirror 2q, and a first fixed pulley 2/ is mounted on the copying machine main body to the right of the movement range of the mirror unit 2q. ing. A pulse generation disc 23 (having a number of light passage notches arranged at a constant pitch around the periphery) is coaxially fixed to the No. 1 fixed pulley 22, and the pulse generation notches of the disc 3 are arranged Pulse generation detection sensors 2'l are fixed to the main body of the copying machine in correspondence with the portions.

The sensor 2'l has a structure in which a light-emitting element and a light-receiving element are arranged with a disc 23 in between.As the disc 23 rotates, each time the light from the light-emitting element passes through the notch and enters the light-receiving element. , this light receiving element generates a pulsed electrical signal. 1st
A position detection plate 27' is fixed to one mirror 2q, and the plate 2
Position detection sensors S, S2 corresponding to 9' are fixed to the main body of the copying machine at intervals to be described later. Sensor S1. Like the sensor 2tI, S2 also consists of a light emitting element and a light receiving element, and generates a signal when the plate 29' enters between the pixel elements.

A drive pulley 20 is rotatably fixed to the copying machine main body at a lower intermediate position of the first fixed pulley 22 and the second fixed pulley 22. It is rotated via either clutch cr (FIG. 2(a)). One end of the drive wire 2g is locked to a fixed point 3/ on the main body of the copying machine, passed around the movable pulley core, and wound around the fixed pulley 2/ several times to prevent it from slipping. It is wound around the pulley 22 in the same way, and is connected to the first mirror 2, the hook is passed to the movable pulley 27, and the other end is locked to the fixed point 32.

The operation of the above embodiment will be explained with reference to FIG.

In the figure, point A is the starting point of forward movement of the first mirror 3, point B is the exposure start position, that is, the leading edge of the document, and six points are approximately the positions of the exposure end position, that is, the trailing edge of the document. When the copy start button is pressed and the photosensitive drum reaches a predetermined position, the forward clutch Cf, which transmits the speed corresponding to the selected magnification from the motor to the pulley 20, is activated, and the drive of the motor M is transmitted to the drive pulley. When θ starts rotating counterclockwise, the first mirror 29 moves to the right in FIG. ,
The two mirrors 30 start moving in the same direction at half the speed. When the mirror 2q, 3θ reaches a constant speed at point B, scanning of the original begins (thus, exposure of the original image to the photosensitive drum begins), and when the scanning of the original ends at point 6, and therefore the exposure of the original image to the drum ends. The reverse clutch cr operates and the drive pulley 2o rotates clockwise, causing the mirror unit 29 (3
0 double-acts and returns to point A.

As an example to explain this embodiment in detail, a clock disc 2
3, the forward movement of one first mirror y is 10w.
n (therefore, the pitch of the clock pulses of the two sensors corresponds to the movement distance of the mirror 3 in the order of 70), and when copying a JIS standard A4' size document, as shown in the upper row of Fig. 3. You can get a time chart.

In other words, since the scanning length of the document in the short direction is 270 mm, the scanning amount is 2 regardless of the selected magnification or scanning speed.
/ pulse. Furthermore, the run-up distance A-B is 5otran,
This is Sunawachi S Pulse. Therefore, in the case of an A"% size original, the number of pulses generated by sensor 2'l is counted by the pulse counter from the operation of forward clutch Cf, regardless of the selected magnification or scanning speed, that is, the type of forward clutch. Then, after the transition period has elapsed, the forward clutch and lever Cf should be deenergized, and then the reverse clutch cr should be activated.Also, the position detection sensor S1 is for detecting the reciprocating movement of the optical system. , position detection sensor S2 is arranged in the scanning direction 100 times (equivalent to 10 pulses) from sensor S, and outputs a signal to stop the operation of reverse clutch Cr when the optical system moves backward. In the illustrated example, the mirror 3 is arranged at a position where a signal is generated when it is at the forward movement starting position, but the mirror 3 is not limited to the above position as long as the position of the mirror 3 is detected before the end of the run-up of the mirror, that is, before the start of document scanning. Further, if some error in mirror movement amount is allowed, sensor S1 may be arranged to detect the position of mirror 3 after the document scan starts.In any case, the signal from sensor S causes the scanning mirror to move. Pulses from the sensor 24' are measured from the time it is determined that the sensor is at the reference position.

It goes without saying that the sensors S, S2 may also detect the position of the mirror.

In the embodiment described above, pulses are obtained by moving the optical system in order to change the scanning speed of the optical system, forward movement, and backward movement by switching the clutch to drive the motor M.
As shown in the figure, the drive pulley, 20 is the forward/reverse motor M2.
It can also be applied when it is fixed coaxially with. This motor M2 has a built-in encoder and is electrically synchronized with the photoreceptor. The pulses generated by the encoder are the same as the purpose of the pulse generating plate 23 in the above embodiment.
It is also possible to use the sensor S, , S2 to control the scanning member of the optical system. In this embodiment, not only the clutch ON/OFF operation but also the motor M2
If the applied voltage is controlled using a DC servo motor etc.,
It is possible to smoothly drive the scanning member of the optical system at each position at an optimal speed. In addition, the present invention steplessly
The present invention can also be applied to copying apparatuses that can change the magnification in a very large number of steps.

As explained above, regardless of the magnification and scanning speed selected, the scanning amount is determined by the number of pulses depending on the size of the original, so the reciprocating movement of the scanning member of the optical system can be easily controlled, and variable magnification copying is possible. This has the effect of increasing the speed of the device.

[Brief explanation of the drawing]

FIG. 7 is a schematic front cross-sectional view of a copying machine with a stationary document table to which a nine-first embodiment of the present invention is applied, FIG. 2 is a detailed front view of one embodiment of the present invention, and FIG. (2) (a) is a block diagram of the drive reel in Figure 2, Figure 3 is a graph diagram of each subassembly in Figure 2,
FIG. 9 is a front view of another embodiment of the invention. 20... Drive reel, , 22... No. 1 fixed pulley. 23... Disc for pulse generation. 2'l...Pulse detection sensor. 2ヲ′...First mirror detection unit. M, , M2... Drive motor. Sl, S2...First mirror position detection sensor. Figure 2 (a) Is3 diagram

Claims (1)

[Scope of Claims] A variable magnification optical device having a reciprocating optical system scanning member and a driving means for driving the scanning member, comprising: at least seven position detection means for detecting the position of the scanning member; a pulse generating means disposed on the driving means, and when the scanning member reciprocates, a variable drive means detects the position of the scanning member and controls the movement based on signals from the position detecting means and the pulse generating means. Double optical device.