JPH0481807A - Optical scanner - Google Patents

Abstract

PURPOSE:To prevent the degradation in scanning efficiency with simple constitution by detecting the acceleration distance at the time of first scanning and controlling a scanning start position in such a manner that the scanner makes an approach run by the acceleration distance detected at the time of the 2nd and subsequent scanning. CONSTITUTION:A CPU 200 moves a scan motor 29 by one step upon receipt of the lapse of the set time from a speed timer 201. Then, the acceleration and deceleration control of the scan motor 29 is possible by continuously changing the set time of the timer 201 to increase or decrease by the CPU 200. A position counter 202 indicates the position on the scanning line of the scanner and is interlocked to the scan motor 29. The counter is also connected to a memory 203 to control the scanner. The 2nd and subsequent scanning start position S'2 is changed in the case of continuous scanning of >=2 times at the same magnification in order to eliminate the wasteful approach run distance which can be discovered by the 1st scanning, by which the scanning time is shortened and the degradation in the scanning efficiency is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical scanning device used in a copying machine, a laser beam printer, an image scanner, etc., and particularly relates to a technique for controlling a scanning start position during multi-scanning.

[Conventional technology]

Copying machines consist of an optical scanning system that optically scans the original image, an image forming section that forms the image of the scanned original on a photoreceptor and transfers it to paper, and a transport system that transports the paper. configured.

2. Description of the Related Art In recent years, the mainstream of copying machines has become one that has a so-called zoom function that allows a copy image of an original to be obtained at an arbitrary magnification. In order to change the magnification of the copied image, the scanning optical system uses a constant scanning speed V2-V, which is obtained by multiplying the circumferential speed V1 of the photoreceptor by the reciprocal 1/n of the magnification n.

It is necessary to perform exposure scanning of the document from the leading edge of the document at ×1/n.

In copying machines with such a zoom function, the scanning speed of the optical scanning system varies depending on the magnification, and the acceleration distance to reach that scanning speed varies, so a sufficient approach distance from the scanning start position to the leading edge of the document must be ensured. It is necessary to do so.

In other words, the smaller the magnification, the faster the scanning speed and the longer the acceleration distance, so in order to accommodate all magnifications, the approach distance must be longer than the acceleration distance at the minimum magnification (maximum scanning speed). be.

[Problems to be Solved by the Invention] However, the frequency of copying at the minimum magnification is not so high in normal copying, and usually copies are made at other magnifications, especially at the same magnification. Therefore, in the case of copying at a magnification other than the minimum magnification, the run-up distance becomes longer than necessary, resulting in wasted run-up time. This is not so much of a problem when performing one scan from one document, or, although it is less of a problem, when scanning multiple sheets from one document. When copying and performing full-color copying in which a full-color image is obtained by scanning one original document four times according to yellow, magenta, cyan, and flank, wasted run-up time is repeated and accumulated, reducing the scanning capacity per hour. There was a problem in that the copying efficiency of copying machines was lowered.

In order to reduce this wasteful run-up time, it is conceivable to change the scan start position according to the magnification.

For example, it is known that a position detection sensor is provided at a scanning start position corresponding to the magnification, and the optical scanning system is moved to the corresponding position detection means when changing magnification such as enlargement or reduction.
(Special Publication No. 56-36425). If the magnifications are limited to a few types, the method using the position detection means disclosed in the above publication is feasible, but in a copying machine with a zoom function, position detection means may be provided at the scanning start position corresponding to all the magnifications. That is impossible. Therefore, in a copying machine with a zoom function, the optical scanning system is driven by a motor with a position detection function, such as a motor with an encoder or a stepping motor, and the number of steps is counted to set the optimum scanning start position according to the magnification. is possible.

However, if all scanning start positions for setting are stored in a memory, a large capacity memory is required and the configuration of the apparatus becomes complicated.

It is also possible to calculate the scanning start position each time the magnification is changed, but if the acceleration pattern becomes complicated,
There is a problem in that the computation becomes complicated and a large-capacity arithmetic device is required to perform the computation in a short time.

The present invention was made in view of the above circumstances, and includes detecting the acceleration distance during the first scan during multi-scanning, and controlling the scan start position so that the acceleration distance detected during the second and subsequent scans is covered. Accordingly, it is an object of the present invention to provide an optical scanning device that can prevent a decrease in scanning efficiency with a simple configuration.

[Means to solve the problem]

The optical scanning device according to the present invention exposes and scans the original image by accelerating from a predetermined position along one direction of the original image until it reaches a relative speed according to the scanning magnification ratio. When one original image is scanned multiple times, an acceleration distance detection means for detecting the acceleration distance during the first scan, and a means for controlling the start position of the second and subsequent scans based on the detected acceleration distance are provided. It is characterized by being prepared.

C Effect] In the present invention, when one original image is scanned multiple times, the first scan is started from a predetermined position where a sufficient run-up distance can be obtained even at the minimum magnification, and the acceleration distance is detected. Then, the stop control at the time of return is performed so that the second and subsequent scans are started from a position that is toward a predetermined position by the detected acceleration distance from the leading edge of the document. This eliminates wasted run-up time and improves scanning efficiency.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on figures showing embodiments thereof.

FIG. 1 is a vertical cross-sectional view showing the general structure of a copying machine using an optical scanning device according to the present invention.

A photoreceptor drum 3 is arranged to be rotatable in a clockwise direction (in the direction of the arrow) at the upper left of the center of the copying machine 1. Surrounding the photoreceptor drum 3 are a charger 4, an editing eraser 5, and a developing device. Containers 6 to 9, a transfer belt 11, a cleaning device 22, and a main eraser 23 are provided.

The photosensitive drum 3 is provided with a photosensitive layer on its surface, and the surface is uniformly charged by passing through the main eraser 23 and the charging charger 4, and the photosensitive drum 3 is used as an optical system including an optical scanning device of the present invention, which will be described later. From 27, it is exposed to light for forming a latent image.

The editing eraser 5 is used for full-color image formation, and consists of an LED array in which a large number of LEDs are arranged in a row in a holder arranged along the axial direction of the photoreceptor drum 3. is configured so that it can be partially erased.

Each developing device 6, 7, 8.9 stores a developer in which a carrier is mixed with toner of each color of yellow (Y), magenta (M), cyan (C), and black (BK). Toner density sensor (ATDC sensor) for controlling the density of each color toner 71y71m 71c, 71
k is provided.

Note that the developing units 6 to 9 are not limited to a type in which they are fixedly arranged around the photoreceptor drum 3, but may be in a type in which the developing units 6 to 9 are integrated and movable in the vertical direction, for example. Any type of toner may be used as long as it can selectively supply toner of different colors to the photoreceptor drum 3.

The transfer belt 11 temporarily holds the toner image developed on the photoreceptor drum 3 by the developing devices 6 to 9 in order to transfer it to the paper P (secondary transfer).
The hooks extend from 2 to 16, and are supported so as to be rotatable in the counterclockwise direction (in the direction of the arrow -1) while always being in contact with the photoreceptor tram 3.

A transfer charger 17 for primary transferring the toner image from the photosensitive drum 3 onto the transfer belt 11 is arranged inside the transfer belt 11, and a transfer charger 17 for secondary transfer is arranged outside the transfer belt 11. Transfer charger 20, separation charger 21 that separates paper P from transfer belt 11, and transfer belt 1
A heald cleaner 19 having a fur brush 19a for cleaning the outer surface of the fur brush 1 is provided. The fur brush 19a can be pressed into contact with the transfer belt 11 (during cleaning) or separated.

A document platen glass 28 is arranged on the top surface of the copying machine 1, and a document size detector that moves to the rear side directly below the document platen glass 28 to detect the size of the document plate without interfering with scanning. A device 101 is installed.

Further, an optical system 27 is arranged at the top of the copying machine 1. The optical system 27 is located below the document platen glass 28 with an arrow mark M5.
A scanner 30, which is an optical scanning device of the present invention, is capable of reciprocating in the direction (forward movement direction) and the direction of arrow M6 (backward movement direction), and a main lens 3 whose position is adjusted according to the copying magnification.
5. A filter selection device 36 that performs color separation exposure, a fixed mirror 37 that guides the scanning light reflected by the mirror attached to the filter selection device 36 to the photosensitive drum 3, and a scanning light transmitted through the mirror of the filter selection device 36. It is composed of a color image sensor 38 that receives light, and when the scanner 30 moves forward, it scans the document sheet and exposes the photoreceptor drum 3 to light.

The scanner 30 includes a first slider 31 having an exposure lamp 33, a mirror 34 and a detection piece 39, a mirror 35a,
35b, the first slider 31 moves forward at a speed of V,/n (n is the copying magnification) with respect to the circumferential speed v1 of the photosensitive drum 3 during scanning of the document. , the second slider 32 is driven by a scan motor 29 using a stepping motor so as to move forward at a speed of V+/2n. The reference position (home position) of the scanner 30 is detected when the scanner home switch 74, which is a microswitch, turns on the detection piece 39.

The length of the detection piece 39 in the moving direction is such that the scanner home switch 74 will not be turned off even when the first slider 31 is at its rightmost movement limit. Detection of the reference position by the scanner home switch 74 is performed only when detection of the reference position is necessary, such as when the power is turned on, and if the scanner home switch 74 is turned off at that time,
The scanner 30 is moved to the right and stopped at the timing when the switch 74 is turned on. If it is already on, the scanner 30 is moved to the left, moved to the right again when the switch 74 is turned off, and stopped when the switch 74 is turned on. That is, by always detecting the switch and the back 4 from a fixed direction, the detection accuracy of the reference position is improved. Further, the reciprocating positioning of the scanner 30 is controlled by the number of steps of the scan motor 29. Note that positioning by the stepping motor is under open control, and even if the planned drive and the actual drive differ for some reason, there is a risk that an undetectable misstep may occur.

To prevent this, for example, place the original on the document table glass 28 with the right reference, and install an image edge detection switch that indicates the position of the image edge to detect a misstep from the expected number of steps to reach the image edge and the switch detection timing. Just do it.

The filter selection device 36 has a half mirror 36ND (ratio of i3 transmission and reflection is 6:4) centered on the axis 36a;
and three filter mirrors 36YB, 361'IG, 3
6CRs are arranged radially at 90 degree angles to each other, and rotation selectively switches any of these mirrors. Filter mirror 36YB, 3
61'1G36CR is blue (B) and green (
A mirror and a filter are integrated by vapor-depositing color separation filters of G) and Shi7do (R) on the mirror surface, and are used for Y, M, and C color toners, respectively.

During exposure scanning for image formation, the reflective surface of the selected mirror is positioned so as to be tilted approximately 10 degrees clockwise with respect to the vertical plane, thereby guiding the scanning light to the exposure point of the photoreceptor drum 3. It will be destroyed.

In addition, in the preliminary scan to read the image of the document sheet prior to the exposure scan, the half mirror 36ND is used.
is selected and positioned perpendicular to the incident direction of the scanning light in order to improve the MTF (imaging power) of the color image sensor 38. 77 is a filter selection device 36
This is a rotational position detection sensor for determining the home position of the filter mirror 36CR, and FIG. 1 shows a state in which the filter mirror 36CR is selected and positioned.

In the following description, the half mirror 36ND, filter mirrors 36YB, 36MG, and 36CR may be referred to as an ND filter, a B filter, a G filter, and an R filter, respectively, based on their color separation characteristics.

The color image sensor 38 is provided with three element rows each consisting of a large number of light receiving elements arranged in the main scanning direction, and the first to third element rows each include an R filter, a G filter, and a B filter. is provided. One light receiving element corresponds to one pixel of the original image, and each light receiving element corresponds to one pixel of the original image.
A photoelectric conversion signal SO corresponding to the intensity of reflected light with respect to color is sent to the image processing section 100 as document information.

On the other hand, an upper paper cassette 42 and a lower paper cassette 43 containing paper P are installed in the lower part of the copying machine 1, and the left side of the copying machine 1 is equipped with a paper cassette 42 for storing paper P and a lower paper cassette 43 for manually feeding the paper P. A manual paper feed port 41 is provided which is opened by opening the door 41a, and these paper cassettes 42, 43, and manual paper feed port 41 are used selectively when feeding paper.

The paper size sensors 42 and 43 each include pick-up rollers 44 and 45 that feed out the paper P one by one, and paper size sensors 81 and 82 that detect the size of the paper P.
, paper empty sensors 83 and 84 for detecting lack of paper P are provided, and a manual feed sensor 87 for detecting insertion of paper P is provided in the manual paper feed port 41.

The paper P fed out from the paper cassette 42 is conveyed to the timing roller 46 by a paper feed roller 47, and the paper P fed out from the paper cassette 42 is conveyed to the timing roller 46 by paper feed rollers 48, 47, where it waits. do. Further, the paper P inserted into the manual paper feed port 41 is conveyed to the timing roller 46 by the manual feed roller 49 .

A paper detection sensor 85 is provided near the paper feed roller 47 to detect the presence or absence of paper P in the paper feed path R1 between the paper feed roller 47 and the timing roller 46. A timing sensor 86 is provided to detect the leading edge position of the passing paper P.

The waiting paper P is conveyed by the rotation of the timing roller 46 in synchronization with the transfer mark 1, and the toner image 2 is transferred from the transfer belt 11 to the paper P at the transfer position.
Next to be transferred. Thereafter, the paper P is sent to the fixing unit 51 by a conveyor belt 50 having a linear distance corresponding to an A4 size paper.

The fixing unit 51 includes an upper roller 52 having two heater lamps 54 and 55, a lower roller 53 having one heater lamp 56, and a temperature sensor 91 including a thermistor placed near the upper roller 52. The toner image is melted and fixed on the paper P.

The paper P on which a desired copy image has been formed by fixing the toner image is sent to the sorter 2 by an ejection roller 57 with an ejection sensor 88 disposed nearby, and is sent to the storage tray 6 of the sorter 2.
1 or to a bin (shelf) 62 for sorting.

In FIG. 1, 24 is a main motor that mainly drives various parts related to feeding and transporting paper P, and 25
26 is a PC motor that drives the photosensitive drum 3, transfer belt 11, etc., and 26 is a cooling fan.

In the copying machine 1 configured as above, the above-mentioned Y, M,
Monochrome copy image of each single toner color of C and BK, Y
R (Y and M), G (Y and C), obtained by superimposing toner images of two of the three primary colors of , M, and C.
It is possible to form a full-color copy image obtained by superimposing a composite monochrome copy image of B (M and C) and toner images of three primary colors.

When forming a single toner color or composite monochrome copy image, a half mirror 36ND is used to expose and scan the original, and the latent image formed on the photoreceptor drum 3 is divided into various colors according to the specified color. Developing is performed using any one of the developing devices 6 to 9, and the toner image is transferred onto the sheet 11. Furthermore, in the case of a composite monochrome copy image, the same original document is exposed and scanned again by the half mirror 36ND, and the toner image developed using the developing devices 6 to 9 different from the previous one is transferred to the transfer heald 11. The toner images of the two colors are superimposed on the transfer sheet 11.

In addition, in forming a color copy image, the copying machine 1:
To improve the reproducibility of black areas, four toner colors, including Y, MC, and BK, are sequentially used. That is, a total of four exposure scans are performed on the same document, and for each scan, B,
The G, R, and NO filters and the developing devices 6 to 9 are selectively switched, and the photoreceptor tram 3 forms and develops a latent image by color-separating the document, and the toner images are sequentially transferred to the belt 11. The toner images of each color are transferred and superimposed on the transfer belt 11.

When overlapping toner images (hereinafter referred to as "multiple transfer"), it is necessary to transfer each toner image to the same position on the transfer plate 1, so the copying machine 1 of this embodiment uses multi-scanning as described later. The start timing of the movement of the scanner 30, that is, the start timing of forming a latent image on the photoreceptor drum 3 is controlled by the timing of .

When forming a color copy image, a preliminary scan is performed to distinguish the original image into a color image area containing colored images and a monochrome image area consisting only of achromatic colors.
When forming an image with each C toner, the latent image corresponding to the monochrome image area is erased by the editing eraser 5 prior to development, and conversely, when forming an image using BK toner, the latent image corresponding to the color image area is erased using the editing eraser 5 prior to development. to erase. That is, the color image area is reproduced by multiple transfer of Y, M, and C toners, and the monochrome image area is reproduced using only BK toner. As a result, it is possible to obtain clear reproduced images without subtle color shifts for images with small line widths such as characters and line drawings that are generally expressed in black, and it is also possible to obtain clear reproduced images without subtle color shifts for images with small line widths such as characters and line drawings that are generally expressed in black. A natural-looking copy image with good reproducibility can be obtained.

FIG. 2 is a block diagram showing a schematic configuration of a control system of a scanner 30, which is an optical scanning device of the present invention.

The scanner 30 is controlled by the CPU 200.

A scan motor 29, a speed timer 201, a position counter 202, and a memory 203 are connected to the CPU 200.

The speed timer 201 is a timer that determines the speed of the scan motor 29, counts the time set by the CPU 200, and notifies the CPU 200 when the set time has elapsed. In response to this, the CPU 200 moves the scan motor 29 by one step. Therefore, by continuously increasing/decreasing the set time of the speed timer 201 by the CPU 200, it becomes possible to control the acceleration/deceleration of the scan motor 29.

The position counter 202 indicates the position of the scanner 30 on the scanning line, and the count value is 0 at the first scanning start position, and increases by 1 each time the scan motor 29 moves one step in the forward direction. Decreases by 1 each time you move in the backward direction.

The memory 203 stores the target speed corresponding to the magnification, the target number of acceleration/deceleration steps, and the detected acceleration distance.

Next, an outline of the operation of the present invention will be explained.

The present invention focuses on the fact that the decline in scanning ability becomes a significant problem when the number of scans increases, and when scanning at the same magnification two or more times in succession, the starting position of the second and subsequent scans is changed. It is something to do.

There are two reference scanning start positions here. One is the first scanning start position S corresponding to the case of reduction.

, and the others are the second scanning start position S2 corresponding to the range from normal magnification to enlargement.

FIG. 3 is a diagram showing the relationship between scanning position and scanning speed,
The vertical axis represents the scanning speed, and the horizontal axis represents the scanning position.

FIG. 3 (al indicates the case where scanning is performed only once; when reducing, the scanning starting position is the same as in the conventional case, and the first scanning starting position S, which can secure the acceleration distance necessary for the maximum scanning speed;
It becomes. Further, in the case of the same magnification or enlargement, the second scanning start position S2 is set so that the acceleration distance necessary for the same magnification scanning can be secured.

Note that this first scanning start position S and the reference position detected by the scanner home switch 74 may be the same position, but in this embodiment, they are set apart from the reference position by a predetermined step.

FIG. 3(b) shows the case of continuous scanning with enlargement, 1
The first scan starts from the second scan start position S2, returns to the changed second scan start position 82' and stops during the backward movement, and from the second time onwards, the scan starts from the changed second scan start position 82'. Here, the second change start position s2 is a position in front of the leading edge of the image by the acceleration distance required to reach the target speed set by the magnification, and is the shortest distance position that can secure the acceleration distance necessary for the speed set by the magnification. .

Fig. 3 fc+ shows the case of continuous scanning with reduction, 1
At the time of scanning, start scanning from the first scanning start position S1,
During the backward movement, it returns to the changed first scanning start position Sl' and stops, and
After the first scan, scanning is started from the changed first scan start position 31'. Here, the modified first scan start position 81' is the shortest distance position that can secure the acceleration distance necessary for the set speed based on the magnification.

The above will be explained in more detail using FIG. 4.

FIG. 4 is a diagram showing the relationship between speed and position during reciprocating motion, with the vertical axis representing speed and the horizontal axis representing scanning position. FIG. 4(a) shows a case where enlargement scanning is performed only once, and this case is similar to the conventional case. Conventionally, this operation was repeated to perform multiple scans. In this case, the stop position during the backward movement is the same as the second scanning start position S2. Here, the speed of the backward movement should be faster than the scanning speed during the forward movement, since the scanning process will be faster if it is as fast as possible.

Further, the deceleration is larger than the acceleration because the weight of the scanner 30 and the friction of the traveling path act in the direction of deceleration.

Further, since the backward movement speed may be constant regardless of the magnification, the deceleration distance during the backward movement is always constant. Therefore, in the case of Fig. 4(a), acceleration starts from the second scanning start position s2, reaches the target speed at position d, scans at a constant speed from there to the image rear end position C, decelerates to a stop, and then accelerates backward. After reaching the backward movement speed, it moves backward at a constant speed until it reaches the position, and then starts decelerating and returns to the second scanning start position S2.

Here, the position a of the leading edge of the image and the position C of the trailing edge of the image are constants set before the start of scanning, and by comparing them with the number of steps of the scan motor 29, the timing of paper feeding and the on/off timing of the exposure lamp 33 are determined. Determine various timings such as

However, in this scanning method, the position d at which a constant velocity is reached
The distance from to position a of the leading edge of the image is a wasteful run-up distance. This may be fine if the scanning is performed only once, but if scanning is performed multiple times, this will accumulate and lead to a decrease in scanning efficiency. Therefore, as shown in Figure 4, the stop position during the backward movement is set to positions ad, and the second and subsequent scans are performed from there, thereby eliminating the wasteful run-up distance.

Next, the above operation will be explained in detail. FIG. 5 is a flowchart showing the control procedure of the CPU 200 that controls the scanner 30. Note that this flowchart shows the case of multi-scanning such as multi-copy and full-color. First, it is determined whether or not reduced copying has been selected using a magnification specifying key (not shown) (step #100), and in the case of reduction, the scanner 30 is moved to the first scanning start position S (
Step #102), in the case of same magnification or enlargement, move the scanner 30 to the second scanning start position S2 (step #10
1). Then, set the position counter 202 to O and the speed timer 201 to the initial speed (Step #10
3, #104).

Then, when a copy signal is input by operating a print button (not shown), scanning is started and forward acceleration operation is started (step #105). In forward acceleration, the scanner 30 is accelerated until it reaches a predetermined target speed corresponding to the magnification.

The target speed and current speed are compared by comparing the set value of the speed timer 201 and its target value (step 411).
06) If the current speed has not reached the target speed, reset the speed timer 201 in the direction of increasing the speed. Step #107) Count the set time of the speed timer 201 in the timer subroutine (Step #1
08). After counting, the CPU 200 moves the scan motor 29 one step in the forward direction and increases the position counter 202 by one (step #109, $11
10). The processing from step #107 to step #110 is repeated until the target speed is reached, the scanner 30 is accelerated and scanned, and its position is grasped. After reaching the target speed, the value d (-acceleration distance) of the position counter 202
is stored in the memory 203 (step #111), and the process moves to forward constant speed operation. Speed timer 201 for constant speed operation
Step #113 to Step #11 without changing the setting values of
In step 5, the same control as steps #108 to #110 is repeated to continue increasing the position counter 202,
The position of the scanner 30 is grasped and the process proceeds to position C at the rear end of the image (step #112). When the image reaches position C at the rear end of the image, the forward deceleration operation begins. In the forward deceleration operation, reset the speed timer 201 in the direction of speed reduction until the speed of the scanner 30 reaches the initial value.Step #117) Perform the same operation as the acceleration at steps #118 to #120. The scanner 30 is stopped and moves to a backward motion.

In the double motion operation, a double acceleration motion is first performed. Here, the speed timer 201 is reset in the direction of increasing the speed until the target speed is reached, and after the counting is completed (step #123) the scan motor 29 is moved 1 step and 7 steps in the backward direction (
Step #124), and the position counter 202 is decremented by 1 (Step #125). When the target speed of the double motion is reached, the speed shifts to the constant speed of the double motion. This operation is similar to the forward constant speed operation, but the position counter 202 decrements one by one (steps #127 to #129).

The transition from double-acting constant speed to double-acting deceleration is performed when the position counter 202 reaches the value b+ (a-d) (step #
126). As a result, the stop position during the backward movement becomes position a-d. When moving to backward deceleration, the speed timer 201 is reset in the direction of speed down until the initial speed is reached, and after counting is completed, the scan motor 29 is moved one step in the backward direction and the position counter 202 is decremented by 1 ( Step #14
0 to step #143). When it stops, it is determined whether or not the specified number of scans have been completed (step #144).
, if not completed, the process returns to step #106, and if not completed, the process returns to step #100. Therefore, from the second time onward, scanning is started from positions a to d, so that the target speed of the magnification is reached at position a at the leading edge of the image, making it possible to perform exposure scanning with high efficiency.

Next, a method of fixing the mirrors 35a and 35b will be explained.

The mirrors 35a and 35b are moved by a stepping motor (not shown) to a position corresponding to the magnification, but there is a risk that the positions of the mirrors 35a and 35b may shift due to vibrations generated when the second slider 32 moves during exposure scanning. . mirror
When the positions of 35a and 35b shift, the optical path length changes,
Significant image deterioration occurs due to magnification, focus shift, etc.

If only a small number of magnifications are selected, the mirrors 35a and 35b may be fixed using a mechanical fixing method, but in the case of a zoom mechanism, the mechanical fixing method has the problem of complicating the device. In this embodiment, since the mirrors 35a and 35b are moved using stepping motors, they can be fixed as they are by continuing excitation at the position moved by changing the magnification. However, while power is being supplied to the copying machine 1,
If it is fixed all the time, power consumption will increase and other problems such as heat dissipation measures will arise.

In this embodiment, attention is paid to the fact that the stepping motor has a self-holding force, and the self-holding force is used to stop the mirrors 35a and 35b during periods other than exposure scanning, and when an external force is applied such as during scanning, the stepping motor is excited. Let me, mirror 3
The positions of 5a and 35b are now more securely fixed.

FIG. 6 is a diagram for explaining three types of fixing methods, and shows the relationship between the position and speed of the reciprocating movement of the scanner 30. Fig. 6 (In al, excitation is performed only during scanning, and not during standby. In addition, Fig. 6 (In bl, acceleration mirror 35a,
Excitation is performed to ensure position retention only when a large external force is applied to 35b. Although excitation is performed during both acceleration and deceleration in Fig. 6 (bl), it is also effective to excite one side or a portion depending on the pattern of speed changes. Fig. 6 (
In C), excitation is performed only when the direction of movement changes continuously from reciprocation to backward movement. Therefore, the power consumption in FIG. 6 (al) is the highest, and the power consumption decreases as the power consumption increases toward FIG. 6 (b) and (C).

In this embodiment, the present invention has been explained using the optical system of a copying machine as an example, but it goes without saying that the present invention is not limited to this and can be applied to other optical systems such as a laser beam printer and an image scanner. .

In addition, in this embodiment, two scanning start positions were provided in order to shorten the scanning time during normal magnification and enlargement, but the effects of the present invention can be obtained even if there is only one position regardless of the magnification. It's self-evident.

〔effect〕

As explained above, in the present invention, when performing multi-scanning, the acceleration distance of the first forward movement is detected, and from the second time onwards, scanning is started at the front end position of the image by the detected acceleration distance. Since the scanning start position is controlled, the unnecessary run-up distance can be eliminated with a simple configuration, the scanning time can be shortened, and a reduction in scanning efficiency can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing the schematic configuration of a copying machine using an optical scanning device according to the present invention, FIG. 2 is a block diagram showing the configuration of the control system, and FIGS. 3 and 4 schematically show the operation. 5 is a flowchart showing the processing procedure of the CPU, and FIG. 6 is a diagram explaining the mirror fixing method. 29... Scan motor 30... Scanner 20
0...CPU201...Speed timer 202.
...Position counter patent Applicant Minolta Camera Co., Ltd. Representative Patent attorney Noboru Kono Mistake diagram S2 Image leading edge position 62' Image leading edge position (b) S+' Image leading edge position (c) Figure Tokizono Tokimon ( b) Figure time (c)

Claims (1)

[Scope of Claims] 1. In an optical scanning device that exposes and scans the original image by accelerating from a predetermined position along one direction of the original image until a relative speed corresponding to a scanning magnification is achieved, 1. When one original image is scanned multiple times, the method includes acceleration distance detection means for detecting the acceleration distance during the first scan, and means for controlling the start position of the second and subsequent scans based on the detected acceleration distance. An optical scanning device characterized by: