JPH0268577A - Copying device - Google Patents

Abstract

PURPOSE:To obtain maximum copy efficiency by measuring the time from when an optical system including a document illumination lamp moves forth to when an image head is detected and starting the forward movement of the optical system the measured time before the completion time of document replacement. CONSTITUTION:The time (ST) from when the optical system including the document illumination lamp 103 moves forth to when an image head sensor 117 detects the image head of a document 1001 is measured. An automatic document feeder (ADF) 300 starts the forward movement of the optical system including the document illumination lamp 103 the measured ST time before the completion time of document replacement. Thus, while the time of the document replacement is held constant, the maximum copy efficiency is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The invention of the present application (hereinafter referred to as the present invention) relates to a copying machine having an automatic document feeder.

(Prior Art) Conventionally, in this type of apparatus, automatic document feeder (hereinafter referred to as RDF)
Original document exchange is performed when the optical system including the document illumination lamp moves backward.

[Problem to be solved by the invention]

However, since the time required to exchange the RDF document is usually longer than the time required for the optical system to move backward, the copying efficiency is limited by the time required to exchange the document.

The present invention has been made in view of this point, and is a patent characterized in that it provides a copying apparatus that can obtain maximum copying efficiency with a constant document exchange time.

[Means to solve the problem]

In order to achieve the above object, the present invention configures a copying apparatus as shown in (1) and (2) below.

(1) Provide the components a, b, and c of the tsuza.

a. Automatic document feeder.

b, yl, time measuring means for measuring the time from when the optical system including the illumination lamp starts moving forward to when the image tip is detected.

c. means for starting the forward movement of the optical system at a time corresponding to the time measured by the time measuring means before the completion time of document exchange in the automatic document feeder;

(2) Provide the following components a and b.

a. Automatic document feeder.

b. Starting from the time when the document exchange in the automatic document feeder is completed, multiplying the copying magnification by a predetermined time corresponding to the time from the start of forward movement of the optical system including the document illumination lamp to the detection of the image tip at the same magnification. means for starting the advancement of the optical system a pre-determined time;

[Effect]

According to the configurations of No. 111 (1) and (2), the optical system including the document illumination lamp starts moving forward by a time corresponding to the magnification ratio prior to the completion time of document exchange by the automatic document feeder.

〔Example〕

The present invention will be explained below with reference to Examples.

FIG. 2 is a mechanical diagram of a "copying apparatus" according to a first embodiment of the present invention, FIG. 3 is a layout diagram of an operation panel of the same embodiment, and FIG. 4 is a block diagram of the same embodiment.

The explanation will start from the overall configuration, but the main parts are mainly shown in FIGS. 1, 5, and 6.

In Fig. 2, 100 is a main body that has an image reading function and an image recording function, and 200 is a double-sided processing function that turns the recording medium (paper) over during double-sided recording, and performs multiple recordings on the same recording medium. 300 is an automatic document feeder that automatically feeds documents;
400 is a sorting device, that is, a sorter, and these 200
~400 devices can be used in combination with the main body 100 as desired.

A1 main body (100) In the main body 100, 101 is a document table glass on which a document is placed, 103 is a document illumination lamp (n-light lamp) that illuminates the document, and 105, 107, and 109 are respectively used to change the optical path of reflected light from the document. scanning reflective mirror (scanning mirror),
Reference numeral 111 is a lens having focusing and variable magnification functions, and reference numeral 113 is a fourth reflection mirror (scanning mirror) that changes the optical path. 115 is an optical system motor that drives the optical system; 117.1
Reference numeral 21 denotes an image tip sensor and a home position sensor.

131 is a photosensitive drum, 133 is a main motor that drives the photosensitive drum 131, 135 is a high pressure unit, and 170 is a 2
．． A blank exposure unit has LEDs arranged at a pitch of 5 mm, 171 is a potential sensor for measuring the potential of the photosensitive drum 131, 172 is a color developer, and 173 is a black developer, both of which can be removed. 141 is a transfer charger, 1
43 is a separation charger, and 145 is a cleaning device.

176, 177, and 178 are document size detection sensors that detect the presence or absence of a document placed on the document platen glass;
9 is a sensor that detects just before the RDF or the pressure plate (not shown) closes.

151 is the upper cassette, 153 is the lower cassette, 155
157 is a paper feed roller, and 159 is a registration roller. Further, 161 is a conveyor belt that conveys the recording paper on which an image has been recorded to the fixing side, 163 is a fixing device that fixes the conveyed recording paper by thermocompression bonding, and 167 is a sensor used for double-sided recording.

The surface of the photosensitive drum 131 described above is made of a seamless photoconductor using a photoconductor and an electric conductor. The motor 133 starts rotating in the direction of the arrow shown. Next, when the predetermined rotational control of the drum 131 and potential @ control processing (preprocessing) are completed, the original placed on the original platen glass 101 is illuminated by the illumination lamp 103 configured integrally with the first scanning mirror 105. , the reflected light from the original is passed through the first scanning mirror 105 and the second scanning mirror 105.
Scanning mirror 107, third scanning mirror 109, lens 11
1 and a fourth scanning mirror 113 to form an image on the drum 131.

The drum 131 is corona charged by a high pressure unit 135. After that, the image illuminated by the illumination lamp 103 (
The original image) is exposed to slit light, and an electrostatic latent image is formed on the drum 131 using the known Carlson method.

Next, the electrostatic latent image on the photosensitive drum 131 is transferred to a developing device 172.
Alternatively, it is developed by developing rollers 174 and 175 of 173 and visualized as a toner image, and the toner image is transferred onto transfer paper by a transfer charger 141 as described later.

The transfer paper in the upper cassette 151 or the lower cassette 153 is fed into the main unit by a paper feed roller 155 or 157, and then transferred to the registration roller! 59, the latent image is sent toward the photosensitive drum 131 with accurate timing, and the leading edge of the latent image is aligned with the leading edge of the transfer paper. Thereafter, the transfer paper passes between the transfer charger 141 and the drum 131, so that the toner image on the drum 131 is transferred onto the transfer paper. After this transfer is completed, the transfer paper is separated from the drum 131 by a separation charger 143, guided to a fixing device 163 by a conveyor belt 161, fixed by pressure and heat, and then discharged to the outside of the main body 100 by a discharge roller 165. be done.

After the transfer, the drum 131 continues to rotate, and its surface is cleaned by a cleaning device 145 composed of a cleaning roller and an elastic blade.

B. Bedistal (200) - Bedistal ZOO has a deck 201 that can be separated from the main body 100 and can store 2000 sheets of transfer paper.
and an intermediate tray 203 for double-sided copying.

Further, the lifter 205 of the deck 201 which can accommodate 2000 sheets is raised according to the amount of transfer paper so that the transfer paper always comes into contact with the paper feed roller 07.

Further, 211 is a paper discharge flapper that switches the path between the double-sided recording side or multiplex recording side and the discharge side path, and 213, 2
Reference numeral 15 denotes a conveyance path of a conveyor belt, 217 denotes an intermediate tray weight for holding down the transfer paper, and the transfer paper that has passed through the paper ejection flapper 211 and the conveyance path 213° 215 is turned over and stored in the double-sided copy intermediate tray 203. Ru. 219 is a multiple flapper that switches the path between double-sided recording and multiplex recording,
It is arranged between the conveyance paths 213 and 215, and guides the transfer paper to the multiplex recording conveyance path 221 by rotating upward.
Reference numeral 223 is a multiple sheet discharge sensor that detects the end of the transfer sheet passing through the multiple flapper 219. A paper feed roller 225 feeds the transfer paper to the drum 13f through a path 227. 229 is a discharge roller that discharges the transfer paper to the outside of the machine.

During double-sided recording (double-sided copying) or multiplex recording (multiple overlapping copying), first raise the paper ejection flapper 211 of the main body 100 upwards and move the copied transfer paper to the conveyance path 213 of the Bediskuru ZOO.
．． It is stored in the intermediate tray 203 via 215. At this time, the multiplex flapper 219 is lowered during double-sided recording.
At the time of multiplex recording, the multiplex flapper 219 is raised. This intermediate tray 203 can store up to 99 sheets of transfer paper, for example. The transfer paper stored in the intermediate tray 203 is pressed down by an intermediate tray weight 217.

During the next back-side recording or multiplex recording, the transfer paper stored in the intermediate tray 203 is moved one by one from the bottom to the path 2 by the action of the paper feed roller 225 and the weight 217.
27 to the registration rollers 159 of the main body 100.

C, RDF (automatic document feeder) (300) RDF30
0, 301 is a loading tray on which the R-shaped bundle 302 is set, and first, one-sided Jli! Half moon roller 304 at M time
The separation roller 303 separates the originals one by one from the bottom of the stack, and the transport roller 305 and full-surface belt 306 move them to the exposure position on the platen glass 101.
The conveyance is stopped and the copying operation is started. After the copying is completed, the sheet is sent to the bus V via the bus M by the large transport roller 307, and then returned to the upper surface of the document bundle 302 by the discharge roller 308. Reference numeral 309 denotes a recycle lever (which detects one cycle of the original).It is placed on the top of the stack of originals when the original is started to be fed, and when the originals are fed one after another and the trailing edge of the last original passes through the recycle lever 309. One cycle of the original was detected as it fell under its own weight.

Next, for double-sided originals, as mentioned above, transfer the originals to buses I and II.
By switching the rotatable switching flapper 310 there, the leading edge of the document is guided to the bus ■, and the transport roller 3
05, it passes through the bus (2) and is stopped on the platen glass 101 by the full-surface belt 306. In other words, the large transport roller 307 is configured to reverse the document along the routes of buses 1 to 2. The number of originals can also be counted by conveying the original bundle 302 one by one through the buses ~■~■~■~■ until one cycle is detected by the recycle lever 309.

D. Sorter (device for sorting) (400) The sorter (400) has a tray of 25 bins and performs sorting.

Copied sheets are sequentially ejected from the paper ejection roller 229 of the main body, enter the conveyance roller 401 of the sorter, and are transferred to the bus 403.
The paper is discharged from the discharge roller 405 to each bin 411 via the discharge roller 405 . For example, in the sorting mode, each time sheets are discharged into each bin, the bins are raised by a bin shift motor (not shown) and collated.

FIG. 3 shows an example of the arrangement of the operation panel provided on the main body 100 described above. The operation panel has a key group 600 and a display group 700 as described below.

E. Key group (600) In Fig. 3, 601 is an asterisk (*) key, which is used by the operator (user) when in the setting mode, such as setting alternative binding or original eraser size. .

606 is an all reset key, which is pressed to return to the standard mode.

Reference numeral 602 is a preheating key, which is pressed to put the machine of the main body 100 into a preheating state and to cancel the preheating state. Also,
This key 602 is also pressed when returning from the auto-shutoff state to the standard mode.

605 is a copy start key (copy start key);
Press to start copying.

A clear/stop key 604 functions as a clear key during standby and as a stop key during copy recording. This clear key is pressed to cancel the set number of copies. It is also used to cancel * (asterisk) mode. Also, press the stop key to interrupt continuous copying. The copying operation stops after the copying at the time of pressing is completed.

Numeric keys 603 are pressed to set the number of copies. It is also used to set the * (asterisk) mode. A memory key 619 allows the user to register frequently used modes.

Copy density keys 611 and 612 are pressed when manually adjusting the copy density. 613 is AE (＾ut
This key is pressed to automatically adjust the copy density according to the density of the original, or to cancel AE (automatic copy density adjustment) and switch the density adjustment to manual. A cassette selection key 607 is pressed to select the upper cassette 151, the middle cassette 153, and the lower cassette 201. Reference numeral 627 is an automatic paper cassette selection key, which automatically selects a cassette corresponding to the document and the designated magnification ratio.

Reference numeral 610 is a same size key, which is pressed to make a same size (original size) copy. 616 is an auto-magnification key that automatically reduces the original image to fit the specified transfer paper size.
Press to enlarge. 617 and 618 are zoom keys, which are pressed to specify any magnification between 50% and 200%.

608 and 609 are fixed size scaling keys, which are pressed when specifying reduction or enlargement of the fixed size.

A double-sided key 626 is pressed to make a double-sided copy from a single-sided original, a double-sided copy from a double-sided original, or a single-sided copy from a double-sided original. 625 is a binding margin key, which can create a binding margin of a specified length on the left side of the transfer paper. 62
4 is a photo key, which is pressed when copying a photo original.

Reference numeral 623 is a multiple key, which is pressed when creating (combining) an image from two originals on the same side of transfer paper.

Reference numeral 620 denotes a document frame erase key, which the user presses when erasing the frame of a standard size document.The size of the document at that time is set using the asterisk key 601. Reference numeral 621 is a sheet frame erase key, which is pressed to erase the frame of the document according to the cassette size.

622 is a page continuous copying key, which allows you to copy the left and right pages of a manuscript.
Press to make copies on separate sheets.

614 is the paper discharge method (stable, sort, group)
This is a selection key, and if a stapler that can staple paper after printing is connected, it can select or cancel the stapling mode or sort mode, and if a tray (sorter) is connected, it can be used for sorting. , sort mode, and group mode can be selected or canceled.

Reference numeral 615 is a paper folding selection key that allows selection and cancellation of Z-folding, which folds recorded paper of A3 or B4 size into a Z-shaped cross section, or half-fold, which folds recorded paper of A3 or B4 size in half.

630 is a developer selection key, and each time the key is pressed, a black developer and a color developer are alternately selected.

F. Display group (700) In Fig. 3, 701 is an LCD (liquid crystal) type message display, for example, 5 x 7 dots form one character, a 40-character message and a fixed size variable key 6.
08,609, same size key 610, zoom key 617.6
The copy magnification set in step 18 can be displayed. This display 701 is a transflective liquid crystal display with two colors of backlight, and the green backlight is normally lit.
The orange backlight lights up when an error occurs or when copying is not possible.

Reference numeral 706 denotes an equal magnification display, which lights up when equal magnification is selected. Reference numeral 730 is a developer display device that displays the selected developer. A copy number display 702 displays the number of copies or a self-diagnosis code. Reference numeral 705 is a used cassette display, which displays which of the upper cassette 151, the middle cassette 153, and the lower deck 201 is selected.

704 is an AE display, and the AE key 613
Lights up when (Auto copy density adjustment) is selected. 7
09 is a preheating indicator, which lights up in the preheating state.

When in the auto shut-off state, this display 709
flashes. 707 is a ready/wait indicator;
Two-color LED of green and orange when ready (
When copying is possible), the green light is lit, and when there is a wait (copying is not possible), the orange light is lit.

A double-sided copy indicator 708 lights up when either double-sided copying from a double-sided original or double-sided copying from a single-sided original is selected.

Note that when using the RDF300 in standard mode, the settings are 1 copy, automatic paper selection, same size, and 1-sided copying from a 1-sided original. In standard mode when RDF300 is not in use, the number of copies is 1, manual density mode, 1x,
The settings are for single-sided copying from a one-sided original. RDF30
The difference between when 0 is used and when it is not used is determined by whether or not a document is set in the RDF300.

A power lamp 710 lights up when a power switch 712 is turned on. 711 is a copy density display section.

G. Control Device (SOO) FIG. 4 shows a block diagram of the control device 800 of this embodiment. In the figure, 801 and 814 are a mask CP[J and a slave CPU. 803 is a read-only memory (ROM) in which a control procedure (control program) as shown in FIG. 6 according to the present invention is stored in advance;
1 controls each component device connected via the bus according to the control procedure stored in this ROM. Reference numeral 805 denotes a random access memory (RAM) which is a main storage device used for storing input data and as a working storage area.

807 is an interface (Ilo) that outputs the CPU 801 control signal to loads such as the main controller 133;
inputs input signals from the image tip sensor 121, etc., and outputs the CPU 80.
1, an interface 811 is an interface for controlling input/output between the key group 600 and the display 700. These interfaces 807, 809° 81
1 uses NEC's input/output circuit board μPD8z55, for example.

Note that the display group 700 is each display device shown in FIG. 3, and uses LEDs and LCDs. Further, the key group 600 is each key shown in FIG. 3, and the CPU 801 can know which key has been pressed using a known key matrix.

813 is a dual port RAM in which the CPU 801 and CPU 814 can read and write data to each other.
It is used for data communication between U801 and CPU814.

The CPU 814 controls the blank exposure unit 170 according to the blank data calculated by the CPU 801. Then, a potential sensor 171, a size detection 176.
The output signals of 177 and 178 are A/D converted and the data is transferred to the CPU 801 via the dual port RAM 813.

Reference numeral 812 denotes a watchdog circuit (control unit monitoring means) for monitoring abnormalities in CPUSOI, and generates a reset signal for the CPU 801 and CPU 814 when an abnormality is detected.

815 is a power supply to be supplied to this embodiment, and 816 is a 24V (ON), 10V (OFF
, ) to 5V10Vk: With this circuit, CPUAO t detects the opening of the power switch, generates a pseudo abnormal signal by the program, transmits this to the watchdog, resets it, and disconnects all loads. Turn off the drive.

Next, the main parts of the first embodiment will be explained with reference to FIGS. 1, 5, and 6.

Figure 1 is a conceptual diagram of the main parts of this embodiment, Figures 5 (a) and (b)
6 is a timing chart explaining the operation of the same main part, and FIG. 6 is a flow chart showing the operation of the same main part.

In FIG. 1, 300 is an RDF, 1001 is a stacked am, 1002 is a fed document, and 1003 is a discharged document. 121 is a home position sensor, 117 is an image tip sensor, and 103 is an original illumination lamp. As shown in the figure, the document does not need to be completely set during the period (time ST) after the optical system including the document illumination lamp 103 starts moving forward until it detects the image edge.
It is possible to start advancing the optical system including the original illumination lamp by a time ST in advance of the completion time of setting the original;
The optical system including the RH4 illumination lamp 103 starts to move backward, since the original may be exposed during the period from when the DF 300 receives an original replacement instruction signal from the CPU 801 until it enters the movable state (time ET). It is possible to instruct document exchange in advance by time ET.

Next, this advance operation will be explained with reference to the timing chart of FIG.

FIG. 5(a) is a timing chart when the conventional advance operation is not performed, and FIG. 5(b) is a timing chart when the advance operation of this embodiment is performed.

In FIG. 5(a), the document exchange is executed at the same time as the optical system including the document illumination lamp is reversed, and the forward movement of the optical system including the document illumination lamp is started after the document is completely set. It can be seen that the copy processing speed slows down when replacing originals.

On the other hand, in FIG. 5(b), as explained in FIG. 1, the document is instructed to be replaced ET before the optical system including the document illumination lamp starts moving backward, and furthermore, the document is completely replaced. Since the optical system including the document illumination lamp starts moving forward ST hours before the set time, the copying processing speed does not drop when replacing the document, and the copying efficiency is higher than in case (a). ing.

FIG. 6 is a flowchart showing the operation of the main part of this embodiment, which executes the above-mentioned preceding operation while measuring times ST and ET.

Start with 2000, make initial settings to set 30 m5ec in the delay timer area in 2001, and set 200
In step 2, the first document is fed, in step 2003 it is checked whether the document has been set, and when it has been set, in step 2004 the document illumination lamp is turned on and the rise timer for measuring the rise of the document illumination lamp is cleared. Advance. When the image tip signal is checked in 2005 and the image tip is detected, 2006
Then, stop the rising timer for measurement and use it as the rising timer value. 2007 is A4 reversal time 7
00 m5ec is set in the inversion timer, and 700 m5ec - delay timer value 30m5ec is set in the exchange timer for performing advance operation. In 2008, check the time-up of the exchange timer, and after the time-up, in 2009, check whether the first round of the manuscript has finished, and if it has finished, check 2.
The original is ejected at 018, the time-up of the reversal timer is checked at 2019, and after the time-up, the optical system including the original illumination lamp is reversed and moved backward at 2020, and the process ends at 2o21.

If the document has not completed one cycle, in order to enable the optical system including the document illumination lamp to move forward before the document is set in 2010, a timer that is calculated by subtracting the rise timer value measured in 2006 from the RDF document exchange time is set as the advance timer. Set the value.

In 2011, a document exchange is instructed, in 2012, the delay timer is cleared, and in 2013, it is determined whether the RDF is activated. (
Although not shown, this can be done by checking the occurrence of encoder pulses applied to the motor driving the RDF 300 using a well-known interrupt terminal. ) When the RDF is activated, the delay timer is stopped in 2014 and used as a measurement value, which is used in 2007.

The time-up of the reversal timer is checked in 2015, and after the time-up, the optical system including the original illumination lamp is reversed in 2016. The time-up of the preceding timer is checked in 2017. After the time-up, the process returns to 2004 and the operations from 2004 onwards are repeated.

In this way, the document exchange instruction is issued to the RDF before the optical system including the document illumination lamp is reversed from forward to backward, and the optical system including the document illumination lamp starts moving forward before the document is completely set. It is possible to improve copying efficiency. Furthermore, since the times ST and ET required for advance are measured and set, wasted time can be minimized regardless of the copying magnification ratio or variations between machines.

Next, an example in which the values of the times ST and ET required for the preceding operation are set to predetermined values (predetermined values) without being measured during the copying operation will be described as a second embodiment.

The second embodiment has the overall mechanism and configuration shown in FIGS. 2 to 4 like the first embodiment, and performs the same operation as shown in FIGS. 1 and 5(b). The operation is as shown in FIG.

In Figure 7, it starts at 3000 and 1 at 3001.
Feeds the first original, checks whether the original is set in 3002, turns on the original illumination lamp in 3003 when the original is set, and starts moving forward of the optical system including the lamp;
At 3004, when the image tip signal is checked and there is an image edge signal, at 3005, 700 seconds, which is the A4 reversal time, is set in the reversal timer, and 700-30 = 670 is set in the exchange timer for performing the advance operation. Set m5ec.

In 3006, the time-up of the exchange timer is checked, and after the time-up, in 3007, it is checked whether one round of the original has been completed.If it has been completed, in 3013, the original is ejected,
At 3014, the time-up of the reversal timer is checked, and after the time-up, at 3015, the optical system including the document illumination lamp is reversed.

The vehicle is moved backward and the process ends at 3016.

If the first round of originals has not been completed, in step 3008, the advance timer that enables the optical system including the original illumination lamp to move forward after setting the original is set to the rise time at the same magnification (the optical (a predetermined time corresponding to the time from the start of forward movement of the system to the detection of the image tip) Set a timer value obtained by subtracting the value obtained by multiplying 140 m5ec by the magnification.

3009 instructs to replace the original, checks 3010 to see if the reversal timer has timed up, and after time-up, 3
At 011, move the optical system of the RM4 illumination lamp backwards, and at 301
At 2, it is checked whether the preceding timer has timed up, and after the time has expired, the process returns to 3003 and the operations from 3003 onwards are repeated.

In this way, as in the first embodiment, the parking time can be minimized regardless of the copying magnification ratio, and the copying efficiency can be improved.

Incidentally, in a device where the automatic document feeder RDF and the copying machine main body transfer data through well-known serial communication, it is also possible to perform advance operation in consideration of the delay of this serial communication.

Furthermore, instead of measuring the drive delay time with the first input of the motor encoder pulse, it is also possible to provide a sensor on the document paper feed bus and measure this 0N10FF.

〔Effect of the invention〕

As explained above, according to the present invention, from the completion time of RDF original exchange, the time measured by the time measuring means is
Alternatively, since the optical system including the document illumination lamp starts moving forward by a time related to the copying magnification ratio, wasted time can be reduced regardless of the copying magnification ratio, and copying efficiency can be increased. In particular, when using a time measuring means, there is no need to consider variations between machines, so wasted time can be minimized.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram of the main parts of the first embodiment, Fig. 2 is a mechanical diagram of the same implementation, Fig. 3 is a layout diagram of the operation panel of the same embodiment, and Fig. 4 is a block diagram of the same embodiment. 5(a) and 5(b) are timing charts explaining the operation of the main parts of the second embodiment, FIG. 6 is a flowchart showing the operation of the main parts, and FIG. 7 is the main part of the second embodiment. It is a flowchart showing the operation. 101-1 Original platen glass 103-1 Original illumination lamp 117-1 Image tip sensor 300-1 Automatic document feeder aoi---CPU

Claims (2)

[Claims] (1) A copying apparatus characterized by comprising the following components a, b, and c. a. Automatic document feeder. b. Time measuring means for measuring the time from when the optical system including the document illumination lamp starts moving forward until it detects the edge of the image. c. means for starting the forward movement of the optical system at a time corresponding to the time measured by the time measuring means before the completion time of document exchange in the automatic document feeder; (2) A copying apparatus characterized by comprising the following components a and b. a. Automatic document feeder. b. Starting from the time when the document exchange in the automatic document feeder is completed, multiplying the copying magnification by a predetermined time corresponding to the time from the start of forward movement of the optical system including the document illumination lamp to the detection of the image tip at the same magnification. means for starting the forward movement of the optical system before the calculated time.