JPH0298607A - Device for measuring length of sheet - Google Patents

Abstract

PURPOSE:To increase the kinds of originals which can be measured by providing an optical detection means provided at a position opposed to an original sheet and a scanning means for scanning at least one of the above-mentioned sheet and the optical detection means. CONSTITUTION:Since interruption is allowed after scanning is started, external interruption processing is executed every time a 1st carriage 51 advances 0.4mm and a counter is incremented. Then, it is checked whether the scanning position of an optical scanning system 2 reaches a return position, that means, a position where go-scanning is completed. It is decided with the acid of a signal outputted from a return position sensor RP1. When the output level of the return position sensor RP1 changes from L to H, the go-scanning is stopped and return-scanning is started by inverting the driving direction of an electric motor M7. When the output level of the RP1 changes, the scanning position at such a time is regarded as a return-scanning reference position and a counter is cleared to zero.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a sheet length measuring device that automatically measures the sheet length of a document sheet placed on an image reading surface of a copying machine or the like. The present invention relates to a sheet length measuring device capable of measuring sheet length even when using a pressure plate, an automatic document feeder, or other devices with different spectral sensitivity characteristics as light reflecting means.

(Prior Art) Generally, a copying machine is equipped with a plurality of paper feed systems each having recording sheets of different sizes.

The size of the recording sheet on which the image is to be recorded is determined by selecting the paper feed system. A copying machine with an automatic paper selection function detects the size of the original sheet, automatically determines the size of the sheet to be recorded according to the detected size and copy magnification, and prepares a sheet of that size. The selected paper source is automatically selected. In addition, copying machines equipped with an automatic magnification function detect the size of the original sheet and automatically set the copy magnification according to the detected pressure size and the size of the recording sheet of the paper feed system specified in advance. do.

By the way, in this type of device, it is necessary to pressure-detect the size of the original sheet, and as a conventional technique for detecting the size of the original sheet, for example, Japanese Patent Application Laid-Open No. 61-3673
Publication No. 2 is known.

In the apparatus described in the above publications, the original sheet and the optical detector facing it are moved relative to each other (that is, scanned).
The length of the sheet is detected by detecting the scanning position at which the document presence/absence detection state of the detector is switched.

By the way, in a copying machine, for example, a document sheet is fixedly arranged on an image reading surface, a document detector is provided in an optical scanning system for reading the document image, and while the optical scanning system is scanning, the document sheet is fixedly placed on the image reading surface. By detecting the light reflectance at each position and identifying the presence or absence of a document at each position, it is possible to identify the size of the area where the presence of a document is detected, that is, the length of the document.

However, in this type of apparatus, a pressure plate is usually placed on the back side of the document. The surface of the pressure plate facing the image reading surface is exposed to light at the wavelength (for example, 580n+++) to which the photoreceptor of the copying machine is most sensitive, in order to prevent unnecessary toner images from being formed in areas other than the document area. It is colored to reflect. Therefore, in order to detect the presence or absence of a document by scanning the image reading surface, in order to distinguish between the document and the pressure plate, a document detector is used to detect the wavelength of the light reflected by the pressure plate, as shown in FIG. It is necessary to use optical detectors with peak sensitivity at different wavelengths (eg 420 nm).

However, there are various types of sheets used as original documents, and each type has different light reflection characteristics. Here, FIG. 20 is a graph showing the spectral reflection characteristics of each of the seven types of sheets, and in FIG. 20, 1, for example, code C2 is
The characteristics of the manuscript are colored yellow. Looking at this, you can see that the yellow original has an anti-M
It can be seen that the rate is very low. In other words, 420na
Even if an optical detector having a sensitivity peak at + wavelengths is placed opposite a yellow original, the level of light received by the optical detector is low, so the level of the signal it outputs will also be low.

Therefore, in order to distinguish between the original and the pressure plate, the output level of the optical detector is compared with a predetermined threshold value, and the discrimination is made based on the magnitude relationship of the output level with respect to the threshold value.
This threshold value is determined by the output level for the press and the output level for the document to be discriminated. Therefore, if the output level for compression is low, the threshold value can be set low, increasing the number of types of documents that can be discriminated. Conversely, if the output level to the pressure plate is high, the threshold value must be set high, and the number of types of documents that can be discriminated will be reduced.

(Problem to be Solved by the Invention) Copying machines and the like are sometimes equipped with not only a pressure plate but also an automatic document feeder (hereinafter referred to as ADF) as a document holder. In the case of using the ADF, the light reflecting section becomes a conveyor belt of the ADF. The conveyor belt of this ADF is made of rubber, silk, film, etc., depending on the conveyance conditions.Recently, silk yarn has been used for reasons such as improving the conveyance of the belt and improving the prevention of surface stains that occur during document conveyance. A belt is used.

On the other hand, the light reflecting portion of the pressure plate is often made of rubber.

However, as shown in FIG. 21, it is difficult to make the spectral sensitivity characteristics of the light reflecting part the same when the materials are different.
For this reason, in the past, the threshold level was determined based on the one with the highest output level among the various light reflecting parts used, such as rubber and silk thread, and this threshold level was used fixedly. However, as a result, the threshold level becomes too high, resulting in a problem that fewer documents can be identified.

In addition, in conventional devices, the threshold value for comparing the signal output from the optical detector in magnitude is always a fixed value.
For example, if this threshold value is set based on the light anti-sealing part of the pressure plate, if an ADF having a light reflection part (feeding belt) with different spectral sensitivity characteristics from the pressure plate is used, the 1M paper This was a problem because it sometimes became impossible to measure the sheet length.

The present invention has been made in order to solve the problems of the above-mentioned prior art, and even when using either a pressure plate or an ADF having light reflecting means with different spectral sensitivity characteristics,
It is an object of the present invention to provide a sheet length measuring device that can detect the presence or absence of a document using an optimal threshold and can measure the sheet length of various types of documents.

(Means for Solving the Problems) In order to achieve the above object, the sheet length measuring device according to the present invention includes an optical detection means provided at a position facing a yXX receipt, and at least one of the original sheet and the optical detection means. scanning means for scanning and relatively scanning the two; and position signal generating means for generating a signal according to the position of the scanning means.

a light reflecting means disposed at a position facing the optical detecting means with the original sheet interposed therebetween and reflecting light of a predetermined wavelength; and a light reflecting means that biases the scanning means to detect the original sheet and the optical detecting means. The scanning position is grasped by the signal outputted by the position signal generating means through relative scanning, and the presence or absence of the original sheet is determined based on the result of a comparison between the signal outputted by the optical detection means and a predetermined threshold value. a sheet length measuring means for reading the scanning position and detecting the sheet length from the result; a determining means for determining the light reflecting state of the light reflecting means; and a light reflecting state determined by the light reflecting state determining means. The present invention is characterized by comprising threshold setting means for changing and resetting the threshold.

(Function) In the sheet length measuring device of the present invention having the above-mentioned configuration, there is provided a discrimination means for discriminating the light reflection state of the light reflection means such as a pressure plate or an ADF having light reflection means having different spectral sensitivity characteristics, and a discrimination means for determining the light reflection state of the light reflection means such as a pressure plate or ADF, It is equipped with a threshold setting means for changing and resetting the threshold according to the light reflection state determined by the reflection state determining means, so that the threshold value can be adjusted according to the type of light irradiation means used, such as a pressure plate or ADF. The optimal threshold value is set, and the presence or absence of a document can always be detected using the optimal threshold value.

The sheet length of various types of originals can be measured.

(Example) Hereinafter, the present invention will be explained in detail based on the illustrated example.

FIG. 1 is a schematic configuration diagram of a copying machine showing an example of a device equipped with a sheet length measuring device according to the present invention, and FIG. 2 is a schematic configuration diagram of a drive system of the same copying machine when viewed from the back. .

First, the schematic structure of the apparatus will be explained with reference to FIG.

In FIG. 1, reference numeral 1 is a contact glass on which an original is placed, and an optical scanning system 2, which will be described later, is provided below this contact glass 1, and an image formed by light reflected from the original is transferred to the contact glass. An image is formed on the photoreceptor drum 3 via the optical scanning system 2.

Incidentally, this photosensitive main drum 3 rotates clockwise in FIG. 1.

On the other hand, the paper feed system has two stages, with paper feed cassettes 4 and 5.
The recording paper is fed by the paper feed roller 6 or 7 depending on which one is selected. Also.

The fed paper passes between a registration roller 8 and a leading edge bending roller 9 and is guided to the photosensitive drum 3. Around the photosensitive drum 3, there is a charger 10. Eraser 11. Developing device 12. Pre-transfer static elimination lamp & P sensor 13.
Transfer charger 14. Separation charger 152 Separation claw 16
．． Fur brush 17. Electrostatic lamps 18 and the like are arranged.

Here, to explain the copying process of the above-mentioned copying machine, the photosensitive drum 3 is charged to a uniform potential by the charger 10, and when it is irradiated with reflected light from the yK document,
The surface potential changes depending on the light intensity, thereby forming an electrostatic latent image. When this electrostatic latent image passes through the developing device 12, it becomes visible with toner. On the other hand, paper feed cassette 4,
The recording paper fed from the recording paper 5 is fed by a registration roller 8 at a predetermined timing according to the rotation of the photosensitive drum 3.

The toner image is superimposed on the surface of the photosensitive drum 3 on which the toner image is formed. Thereafter, a predetermined voltage is applied to the transfer charger 14, whereby the toner image is transferred from the photosensitive drum 3 to the recording paper side. After the toner image is transferred, the recording paper on which the toner image has been transferred is separated from the photosensitive drum 3 by a separation charger 15 and sent to a conveyor belt 19 . Then, the recording paper is conveyed by the conveyor belt 19 to a fixing roller 20 having a built-in heater, the toner image is fixed by the fixing roller 20, and the recording paper is discharged to a copy tray 22 via a paper discharge roller 21.

The copying process using the copying machine having the configuration shown in FIG. 1 has been described above. Next, the drive system of the copying machine will be briefly described with reference to FIG. 2.

In Fig. 2, the symbol KI in one cycle is the main motor,
The main motor M1 rotates a drum pulley 32 coupled to the photosensitive drum 3 via a main motor pulley 30 and a timing belt 31, and is coupled to each mechanical sliding part via a belt 33. Cleaning immediate sprocket 34. Folding tip roller sprocket 3
5. Resist clutch 36° development drive sprocket 37
．． Toner hopper drive sprocket 38. Fixing quick-acting sprocket 39. Rotate the pulse generator PG, etc. On the other hand, the paper feed motor is coupled to an upper paper feed swing gear 40 and a lower paper feed parking gear 41. Further, reference numeral M7 is a stepping motor that scans and drives the optical scanning system.

Next, FIG. 3 shows a schematic configuration of the optical scanning system 2 of the above-mentioned copying machine.
FIG. 4 shows their perspective views, and will be explained in terms of the optical scanning system.

First, referring to FIG. 3, the optical scanning system 2 will be explained as follows.
Illumination light (halogen lamp) 2a1 reflection plate 2b.

A first carriage 51 consisting of a first mirror 20, etc., and a second carriage 52 consisting of a second mirror 2d, a third mirror 28, etc.
, a lens 2f, a fourth mirror 2g, etc. In addition, the code|symbol 2h is the glass for dustproofing. Further, the first carriage 51 and the second carriage are driven in reciprocating scanning by a stepping motor M7 at a speed ratio of 2:1 so that the optical path length from the original does not change during scanning.

Next, a description will be given with reference to FIG. A drive wire 51 coupled to an optical scanning system is wound around a pulley 60 fixed to the shaft of the stepping motor M7, and the drive wire 61 is connected from one end 61a to a stud pulley 62. Drive pulley 6 coupled to second carriage 52
3. Turn pulley 64. Bracket pulley 65. Pulley 60. Bracket Boo IJ65. A turn pulley 66, a bracket 67 coupled to the first carriage 5I, a U-motion pulley 63. It is connected to the other end 61b passing through the tightener pulley 68 to form a closed loop.

In addition, the HPI shown in Figure 4 is a scanner (optical scanning system)
RPI is a switch (photo sensor) that detects the home position of the scanner, and RPI is a limit switch that detects the end position of one forward scan of the scanner.

RP2 is a limit switch that detects another forward scanning end position. Although not shown in this drawing, the variable magnification mechanism (that is, the lens) is also provided with a photosensor HP2 for detecting the home position.

Here, details of the first carriage 51 are shown in FIGS. 5 and 6. Referring to each episode, the first carriage 51 is
It is supported movably in the scanning direction by book guide bars 71 and 72. Two holes 51b and 51c are formed in the upper surface of the cover 51a that covers the upper part of the first carriage 51. One hole 51b is located approximately at the center of the cover 51a, and the other hole 51c is approximately 90 mm from the center.
It is placed at a position of mm.

Further, one end of an optical fiber 73 is fixedly arranged in the hole 51b, and one end of an optical fiber 74 is arranged in the hole 51c. The other ends of each of the optical fibers 73 and 74 face the light receiving surfaces of photodiodes PDI and PD2, which will be described later. One end of each optical fiber 73, 74 is provided with a hole 51b.

51c, it is arranged so as to face the contact glass 1 as shown in the sixth section. In FIG. 6, ORG is an original, and 80 is a pressure plate that presses the original ORG, and this pressure plate 80 also functions as a light reflecting means.

Next, referring to FIG. 7, which shows an example of the operation board arranged on the top surface of the main body of the copying machine having the configuration shown in FIG.
, K2. K3. K4a, K4b, K5. K
6a.

6b, K7. K8. K9a, K9b, K9
c, KIO, Kll, K12a.

K12b, K13. C, KS, KI, KI and KP, and a number of indicators DI, D2. D3. D4.
It is equipped with D5 etc.

Here, various typical key switches provided on the operation board will be briefly explained.

K6a, K6b, K9a, K9b and Ni9c are
Used to specify copy magnification.

K7 is used to specify/cancel the automatic magnification mode that automatically sets the copy magnification according to the document size and recording paper size.

8 and 11 are used to specify the document size and paper feed system selection, respectively.

KIO is a numeric keypad and is used for specifying the number of copies, etc.

K12a and K12b are used to specify copy density.

KC is the clear/stop key, and 10 is on the numeric keypad.
This is used to clear the number of copies specified and to instruct the stop of the copy operation.

KS is a key for instructing to start printing.

Next, typical displays provided on the operation board will be briefly explained.

Dl is a 7-segment, 2-digit numerical display.

In the normal operation mode, the set value for the number of copies is displayed during standby, and the number of copies is displayed during copying.

D2 displays the copy density setting state.

D3 displays the paper size, paper orientation, and selected paper feed system for each paper feed system.

D4 is a 7-segment, 3-digit numerical display that displays the copy magnification in units of 1% in the normal operating mode.

D5 displays the designated document size.

Next, referring to FIG. 8, which schematically shows the electrical circuit configuration of the copying machine of FIG. 1, the main control board 200 includes a microprocessor 210. Read-only memory (R
OM) 220, read/write memory (RAM) 230
, parallel I10 port 240. Serial I10 port 250, A/D (analog/digital) converter 260. A timer 270 and non-volatile read/write memory (RAM) 280 are provided.

This main control board 200 includes an operation board 310 (seventh
(see figure), optical system control board 320. Lamp control board 330. Heater control board 340. High voltage power supply unit 3
50, yK manuscript detection board 360. Paper feeding unit 36
5. Drivers 370, 380 and signal processing circuit 390
is connected.

The optical system control board 320 controls the electric motor M7 for scanning drive of the optical scanning system 2 and the electric motor M2 for adjusting the magnification of the zoom lens. ENC is a pulse encoder that outputs an electric pulse signal according to the amount of rotation of the electric motor M7. Although not shown, the optical system control board 32
Similarly to the main control board 200, the microprocessor, parallel I10° serial I10. ROM, R.A.
Equipped with M and A/D converters.

The lamp control board 330 controls the light amount of the exposure lamp 2a of the optical scanning system 2.

The heater control board 340 controls the temperatures of the fixing heater HTI provided in the fixing device 20 and the drum heater HT2 built in the photosensitive drum 3.

The high voltage power supply unit 350 generates high voltage power to be applied to each of the bias electrode 12a of the main charger 10° developer 12, the transfer charger 14, and the separation charger 15.

Various AC loads 400 are connected to the driver 370 , various DC loads 410 are connected to the driver 380 , and various sensors 420 are connected to the signal processing circuit 390 . More specifically, typical AC loads 400 include a main motor Ml that drives the photoreceptor drum 3 and the like, a developer cartridge motor, an III feeding fan motor, and a cooling fan motor. Typical DC loads 410 include a cleaning control solenoid, a registration roller control clutch, a separation claw control solenoid, and an eraser 11. These are a total counter, a toner replenishment control solenoid, and an oil replenishment control solenoid.

Furthermore, typical sensors 420 include a timing pulse generator that generates pulses synchronized with the rotation of the main motor, a toner image sensor, a toner color sensor, and a toner color sensor that detects recording paper near the registration roller 27. These are a registration sensor, a paper size sensor, and a paper presence/absence sensor provided in each paper feed system.

9@ shows an example of the circuit configuration of the document detection board 360 shown in FIG. 8. Referring to FIG. 9, this board is equipped with two photodiodes PDI and PO2, and these photodiodes The optical fibers 73 and 74 are arranged opposite to each light receiving surface.

In this example, each photodiode PDI, PO2
The spectral sensitivity characteristic has a peak at a wavelength of 420 nm, as shown as Vaps in FIG. 19 above. Also,
In the copying machine in this embodiment, the photosensitive drum 3
The wavelength of peak sensitivity is 580 nm, and the lower surface (the surface facing the contact glass) of the pressure plate 80 shown in FIG. 6 is colored so as to reflect light with a wavelength around 580 nm. Note that the exposure lamp 2a has a wavelength of 420 nm and a wavelength of 58 nm.
(Generates light containing both wavelengths of lnm.

Referring again to FIG. 9, the photodiode P
DI generates a current according to the received light level.

A signal corresponding to the current is amplified by operational amplifiers OPI and OF2 and output as a signal 'Japs. Similarly,
A signal corresponding to the current generated by photodiode PD2 is amplified by operational amplifiers OP3 and OF2, and a signal Vap
Output as 2.

Here, in FIG. 8, a signal VA is applied from the document detection board 360 to the main control board 200, and signals Vaps and Vap2 are applied from the document detection board 360 to the optical system control board 320.

Next, a schematic operation of the microprocessor 210 of FIG. 8 is shown in FIG. 10, and will be described below with reference to the same figure.

When the copier is turned on, the first step is step SA1 C.
PU initialization processing is performed. In this process,
Initialize the state of the main control board 200 itself.

That is, the contents of the read/write memory 230 are cleared, various mode settings are initialized, and the output ports are reset. Next, the initial setting process of step SA2 is performed. In this process, the states (operation modes) of various boards and devices connected to the main control board 200 are initialized, and the copying machine is set to its initial state. It also sets the mode and count value of the timer 270.

Next, in step SA3, standby mode processing is performed.
At this point, the copying operation is stopped and the copying machine is in a standby state. In this process, the following processing is performed. First, the states of the signals applied to various input ports are read, and the results are stored in the memory 230. Second, the outputs stored in the memory 230 in advance are read. A control data group is output to an output port associated with each data, and a device connected to the output port is controlled. Furthermore, the states of various input ports that have been read in advance and stored in the memory 230 are determined, and the presence or absence of an abnormality is checked.

If there is an abnormality, predetermined abnormality processing is executed.

If there is no abnormality, determine the status of other input ports,
For example, it processes input from the operation board 310, outputs display data stored in the memory 230 in advance to a predetermined output port at a predetermined timing, and displays the data on various displays on the operation board 310. 6 Furthermore, the data to be displayed can be changed according to the state of the mode switch. When the normal operation mode is designated, the number of copies is displayed on the display D1, and the copy magnification is displayed on the display D4.

Note that if the copying is not possible or if the print start key KS is not turned on, the standby mode processing described above is repeatedly executed. Further, copying is not possible when, for example, the fixing temperature is outside a predetermined range or when some abnormality is detected.

When the print start key KS is pressed in the copy-enabled state, the pre-copy mode process of step SA4 is executed. In this process, the main motor starts driving immediately before starting the copying process.

Performs photosensitive drum pre-copy cleaning processing, paper feeding processing, etc.

Next, when step SA4 is completed, copy mode processing of step S^5 is executed. At this point, the copy process is actually executed. This processing includes copy process processing, paper transport processing, toner replenishment processing, abnormality check processing, and the like. In the copy process, various process elements are controlled on/off at predetermined timings synchronized with output pulses from a timing pulse generator that generates pulses corresponding to the amount of rotation of the main motor. If a plurality of copies are to be made continuously, the copy mode process in step SA5 is repeatedly executed.

When the copy mode process of step SA5 is completed for the final copy, the post-copy mode process of step SA6 is executed. In this process, the paper on which the copy image has been transferred is ejected, the photoreceptor drum is cleaned after copying, etc. When the paper ejection is completed, the process returns to step SA3, the standby mode process, and the power is turned off. Repeat the above process until.

Now, next, let's move on to Figures 11, 12, 13, and 14.
The general operation of the optical system control board 320 will be described with reference to the flowchart showing the general operation of the optical system control board 320 shown in the figure. 11 shows the main routine, FIGS. 12 and 13 show the "prescan" subroutine, and FIG. 14 shows the external interrupt processing routine. Here, the external interrupt processing routine is executed at each rising timing of the pulse signal output by the encoder ENC shown in FIG. ) is executed.

First, explanation will be given with reference to FIG. When the copier is turned on, initialization is first performed. That is.

After setting the control board itself to the initial state, the optical scanning system 2
The scanning position of is positioned at the home position, and the magnification of the lens 2f is set to a predetermined magnification (for example, 100%).

When this process is completed, a "ready" message is sent to the main control board 200. Then, it waits for data to be received from the main control board 200, and the received data is stored in a predetermined memory. Also.

When a command is received, processing is performed according to the type of command. Further, when a "prescan" command is received, "busy" is first transmitted, and the "prescan" subroutine is executed. When this is completed, the processing results (Rpos, Fv) are sent to the main control board, and "Ready" is also sent.

When a magnification adjustment command is received, a "visit" is first transmitted, and the 1 magnification adjustment process is executed until the copy magnification reaches the specified magnification. That is, when the zero magnification adjustment for adjusting the magnification of the lens 2f is completed by driving the motor M2, "ready" is transmitted.

When a normal scanning command is received, a ``visi'' is first sent, and normal scanning processing (same as the scanning processing of a general copying machine) is executed until the optical scanning system completes one round trip scan. . Then, when scanning is completed, "ready" is transmitted.

Next, the contents of the "prescan" subroutine will be explained with reference to FIGS. 12 and 13. In this process, first, the exposure lamp 2a is turned on, and in order to wait for the light intensity of the lamp to become stable, a waiting time of 200 m5ec is performed.First, scanning of the optical scanning system 2 is started, and an interrupt is permitted. Note that before starting scanning, the first carriage 51 is
It is positioned at the position shown by the solid line in the figure (home position), and this position is the home position sensor shown in Fig. 4).
It is determined based on the signal output by I.

Since one interrupt is permitted when scanning is started, the external interrupt process shown in FIG. 14 is executed every time the first carriage 51 advances by 0.41, and the counter CNT is incremented. Therefore, the contents of counter CNT correspond to the scanning position.

Next, it is checked whether the scanning position of the optical scanning system 2 has reached the return position, that is, the forward scanning end position. This is determined by the signal output by the return position sensor RPI (see FIG. 4). This return position sensor R
When the output level of PI changes from L to H, the scanning position is regarded as the return position, the forward scanning is stopped, the late movement direction of the electric motor M7 is reversed, and the backward scanning is started. Then, when the output level of RPI changes from H to L, that scanning position is regarded as the backward scanning reference position, and the counter CNT is cleared to 0.

Next, wait for the counter CNT to reach N2; in this example, N2 is set to 85. When the content of the counter CNT reaches N2, that is, when the first carriage 51 advances 34 mm in the backward scanning direction from the backward scanning reference position, the sampling counter CNS is cleared to 0, and the PS sampling flag F aps is set to 41148.

When Faps becomes "1", the level of the signal Vaps is sampled every time the external interrupt process shown in FIG. 14 is executed. The sampled signal is then A/D converted and stored in memory. Also, V
After sampling the aps, the sampling counter CNS is incremented.

Now, returning to FIG. 12, the explanation will be continued.

After the flag F aps reaches II I It, the process waits for the sampling counter CNS to reach 10 in step S52. When CNS reaches 10, that is, when 10 samplings of V aps are completed, the next step S5
Proceed to step 3.

In step 553, one of the sampled Vaps is
Find the average value of 0 and store the result in register Rpx. Then, F aps is reset to II O''.

Note that the position at which Vaps sampling is started in step S52 is a position 454 mm in the forward scanning direction from the starting edge position of the M document. Therefore, the sheet placed on the contact glass 1 is A3 standard size (297 x 420 m).
m) If the sheet has a size equal to or smaller than 0.m), the Vaps sampled in step SS2 corresponds to the level of reflected light at a wavelength of 420 nm at a portion where the original sheet does not exist. In this example, in the portion where no original sheet exists, the Vaps level is 1. It never exceeds Ov.

Now, after executing step S53, register Rp
Check the contents of x, and if both of them exceed 1.0■, it is assumed that the document silt is larger than A3 size, and in this case, the length cannot be measured.
The flag Fmax is set to '1'' and the process immediately returns to the main routine.

Further, if Rpx is 1.0v or less, the following process is executed. First, the flag F aps is set to 11117 again, and the sampling counter CNS reaches 4 in step S54.
Wait until CNS becomes 0, and when CNS becomes 40, proceed to step S55, store the average value of the latest 40 sampled Vaps values in register Rpx,
Reset the flag Faps to ``0''.

Then, if R,px is 1.0v or less, the process advances to step S56, sets CNS to 39, and sets flag Fa.
1''' is added to ps and the process returns to step 54. In this case, when Vaps is sampled once,
Since CNS becomes 40, each time sampling is performed,
The latest 40 average values of Vaps are computed and the results are compared with THV. Here, the contents of Rpx are T)
When the IV is exceeded, the primary processing is executed.

If the comparison result does not satisfy the condition RPX>T)IV, the process returns to step S56 and a new sampling process is repeated.

The above THV is a threshold level that is set to distinguish between a document and a light-reflecting member such as a pressure plate, and to detect the presence or absence of a yK document. The settings are changed depending on the type. In this embodiment, the threshold value THV is set to the level when a pressure plate is used. Further, the means for setting the threshold value will be described later.

Here, referring to FIG. 15, which shows an example of a change in Vaps when performing backward scanning near the end of the original sheet (the right side in FIG. It can be seen that the signal level changes depending on the presence or absence of the pressure plate 80 in the area (without ).

Now, the explanation will be given again with reference to FIG.

When the condition Rpx>THV is satisfied, the contents of the count CNT at that time are stored in the register Rpos.

At this time, the content of Rpos corresponds to the backward scanning distance from the backward scanning reference position, so it is converted to the length of the original sheet. That is, the starting edge position of the original sheet is constant (in this example, 32 mm from the home position), and the distance between the home position and the backward scanning reference position is also constant (in this example, 486 mm).
), the following conversion process of equation (1) is performed and the result (L) is stored in the register Rpos.

L=483-32-(RposXo, 4)”
(1) Also, here, the value of L is compared with the length of various standard size sheets, and if there is one with a similar value, the standard size code is stored in a predetermined register.

Now, through the above process, the length of the original sheet in the scanning direction is detected and stored in the register, but next, the size of the sheet in the width direction (direction of the axis perpendicular to the scanning direction of the optical scanning system) is detected. identify

That is, the process advances to step S57, where the counter CNS is cleared to 0, and the AP2 sampling flag F ap2 is set to 11.
'' is set. When the flag Fap2 becomes 11111, the signal V is set every time the external interrupt processing shown in FIG. 14 is executed.
Sampling of the level of ap2 cannot be performed.

The sampled signal is then A/D converted and stored in memory. Furthermore, after sampling V a p 2, the sampling counter CNS is incremented. Therefore, the first carriage 51 is 0.
, 4 mm, the level of the signal Vap2 corresponding to the level of the light received by the photodiode PCI through the optical fiber 73 and the light received by the photodiode PD2 through the optical fiber 74 is sampled and stored.

Further, in step S58, the content of the counter CNS is 40.
Then, the 40 average values of the sampled Vap2 are stored in the register Rpx. At this time, flag F
ap2 is reset to ll01l. Then, as in the case of measuring the length in the scanning direction, first, it is checked whether the contents of RPX exceed the threshold value THV.

As a result of this check, if Rpx is less than or equal to THV, the process advances to step S59, and the sampling counter CNS is set to 3.
9 is set, Faρ2 is set to 11171, and the process returns to step 558. The contents of Rpx are both T)IV
In other words, when the condition Rpx>THV is satisfied, "1 N" is placed in the flag Fw and the process returns to the main routine.Also, without the condition Rpx>THV being satisfied, the contents of the counter CNT are If N3 is reached,
The flag FV is reset to non and the process returns to the main routine.

As described above, when the above "prescan" subroutine is completed, the processing result (Rpos) is determined according to the main routine shown in FIG.

FW) is sent to the main control board, and the yKH sheet length and width are detected.

In this example, in terms of the scanning position of the first carriage 5I, the value of N3 corresponds to a position 11.2 mm ahead in the forward scanning direction from the starting edge position of the original sheet.

As mentioned above, the tip of the optical fiber 75 is connected to the cover 51.
901 from the center of a, that is, the center in the width direction of the image reading surface
It is placed at a position shifted by 1offl. Further, the original sheet is positioned so that its widthwise center coincides with the widthwise center of the image reading surface (contact glass) 6 Therefore, the reason why the flag Fw is 1'' is because the optical fiber 75 is This is when the light from the original sheet is received.
This is when the width of the original sheet exceeds 18 mm. Also, when the flag Fw is ''O11, the width dimension of the original sheet is 180 or less. Therefore, the flag Fw is ''1
'' or ``0'''' determines whether the width dimension of the original sheet is 1000 or more or less.

By the way, the commonly used standard sheet [P! The dimensions are as follows.

A3: 297 x 420 [+l
Im Ko A 4: 2], OX 297 Em
mco A5: 1411 x 210 [mm] A6
: 105 X 148 Emco B
4: 257 x 364 cm B
5: 182 x 257 [m++
+CoB 6: 128 x 182 Ctrr++]
Among these, the A3 and B4 sheets are large, so in this example, they can be placed on the contact glass with the longitudinal direction of the sheet facing the scanning direction of the optical scanning system (vertical orientation); It cannot be placed on the contact glass when the direction is oriented in the width direction perpendicular to the scanning direction (horizontal orientation). For this reason, A3 and B4 sheets are always placed vertically, so the length in the scanning direction (sheet length)
Based on the detection result, it is determined whether the image is A3 or B4.

On the other hand, sheets other than A3 and B4 can be placed on the contact glass in either the vertical direction or the horizontal direction. Therefore, the sheet length in the scanning direction is the same when an A4 size sheet is arranged horizontally and when an A5 size sheet is arranged vertically. Also, A
The sheet length in the scanning direction is also the same when an S size sheet is arranged horizontally and when an Ae size sheet is arranged vertically. Therefore, in these cases, the sheet size cannot be determined just by measuring the sheet length in the scanning direction, but as mentioned above, if the sheet width dimension is 180 mm
If the size exceeds ++m, the flag F becomes 11111, so by determining whether the flag F is 7+1# or II Ol/, it is easy to determine whether the sheet size is A4 or A5, or A5 or A6. This means that it can be determined.

By the way, as mentioned above, in order to distinguish between the original sheet and the pressure plate, the output levels of the optical detectors PDI and PD2 are compared with a predetermined threshold value THV, and the discrimination is made based on the magnitude relationship of the output level with respect to the threshold value. However, in some copying machines, not only a pressure plate but also an automatic document feeder (ADF) is installed as a document holder. For example, when an ADF is used, the light reflecting part is It becomes the conveyor belt of ADF. The conveyance belt of this ADF is made of rubber, silk, film, etc., depending on the WJ conveyance conditions.Recently, silk belts have been used for reasons such as improving belt conveyance and preventing surface stains that occur during document conveyance. It is being On the other hand, rubber-based materials are usually used for the light-reflecting part of the pressure plate, and for this reason, it is difficult to make the spectral sensitivity characteristics of the light-reflecting part the same when the materials are different, as shown in Figure 21. Therefore, conventionally, the threshold was determined and fixed based on the one that produced the highest output level of the photodetector among the various light reflecting parts used, but with this method, the threshold value was fixed based on the A problem arises in that the types of documents that can be determined are limited.

Therefore, the threshold value needs to be changed depending on the material of the light reflecting section.

Therefore, in the present invention, the type and condition of the light reflecting section, specifically, whether a pressure plate is attached to the main body of the copying machine,
New determination means will be provided to determine conditions such as whether a DF is installed. This discrimination means inputs a code manually through the operation unit 310 shown in FIGS. 7 and 8, stores the data in the nonvolatile memory 280 of the control board 200, and reads out the stored data. Various methods can be considered, such as a method of determining the value by using an ADF, or a method of setting by an electric switch means when an ADF or the like is installed.

Then, by changing the setting of the threshold value depending on the determined state of the light reflection means, an optimal threshold value corresponding to the spectral distribution characteristics of the light reflection means can be obtained.

The number of types of manuscripts that can be identified increases.

Furthermore, when the pressure plate or ADF is open, the output level of the optical detector is the lowest regardless of the light reflecting means, and the threshold value can be set to the lowest. Therefore, in the present invention, the position of the light reflecting means with respect to the original sheet, that is,
It also detects the ``open'' or ``closed'' state, and the threshold value is ``open''.
′, it should be set low.

Here, FIG. 18 shows the output of the optical detection means (optical detector) when measuring the length of the original sheet.

In FIG. 18, the pressure plate or ADF area is the area where there is no original, the solid line shows the output when the pressure is released or the ADF is opened, the - dotted line shows the output when the pressure plate is closed, and the broken line shows the output when the pressure plate is closed.
The respective outputs are shown when the DF is in the closed state. Also,
(a), (b), (C), and (d) in the manuscript area show the output of different manuscripts, and also THI.

TH2, T)13 indicates threshold values corresponding to the ADF closed, pressure released closed, and opened states, respectively.

In the conventional method, the threshold value is usually set to T)II, which is the highest level, so only documents (a) and (b) can be measured, but documents (c) and (d) cannot be measured. However, in the present invention, THI when the ADF is closed, TH2 when the pressure plate is closed, and TH3 when the pressure plate or ADF is open.
Because the threshold value is reset depending on the state of the light reflecting means, it is possible to measure the document size in (a), (b), and (c) when the pressure plate is idle, and when the pressure plate is released or the ADF is open. The document sizes of (a), (b), (C), and (d) can be measured.

Next, as a more specific example, as shown in FIG. 16, whether the pressure plate is set or the ADF is set is input from the operation unit (operation board) 310 shown in FIG. An example of a control program for storing data into the nonvolatile memory will be briefly explained using a flowchart.

The program mode shown in the flowchart of FIG. 16 is a mode that is set when a service person or the like initializes various copying conditions, and the settings are already completed when the copying machine is used normally.

There is no need to reset the settings. Incidentally, this program mode can be called up by turning on the program key KP (see FIG. 7) of the operation section 310.

This will be explained below with reference to FIG.

First, when the program key KP of the operation unit 310 is turned on, execution of the program mode is started, and the operation unit 310 is turned on.
10 keys are waiting for 10 inputs. Therefore, first, use the 10-key KIQ to select one of the various program modes for the 6-pressure plate and ADF settings.
It can be selected by inputting 12'' using the 0 key KIO.

Next, when pt12t* is input using the 10-key KIO, the setting mode for pressure plate, A, and DF is entered, and when selecting the pressure plate, input 1lol# using the 10-key KIO, and when selecting ADF. input ``1''.

Note that other inputs are invalid.

After inputting ``O'' or ``1'' by 10 on the 10 key, enter the confirmation key H#JI, and the 2 non-volatile memory 28
ADF sector flag (ADFSETFG) of 0 is '''O
``'' or 1'''', and the pressure plate and ADF setting process is completed.

Note that the program shown in FIG.
The above A is executed by the side microprocessor 210.
The contents of the DF set flag (ADFSETFG) are sent to the optical system control board 320 that performs sheet length detection processing.

Further, the main control board 200 reads a signal from an open/close detection switch (not shown) that detects the opening/closing of the pressure plate or the ADF, and the result of this open/close signal is also transmitted to the optical system control board 320 .

Here, in the memory of the optical system control board 320, the first
Threshold level (an example is shown in Figure 7)
A program for determining the THV is stored, and the optical system control board 320 first opens and closes the pressure plate or ADF based on the ADF set flag (ADFSETFG) and the open/close signal result sent from the main control board 200. First, it is determined whether the light reflecting means is a pressure plate or an ADF, and a threshold value THV corresponding to the state of the light reflecting means is determined and set in the memory.

That is, to explain in conjunction with the previous FIG.
When F is open, the threshold value is determined and set based on TI(3) and the state of the light reflecting means.

Therefore, according to the present invention, when measuring the document size (sheet length and III), the threshold value is set according to the state of the light reflecting means, so the presence or absence of the document is always detected using the optimal threshold value. This makes it possible to measure the sheet length of various types of originals.

(Effects of the Invention) As described above based on the illustrated embodiment, according to the sheet length measuring device according to the present invention, a pressure plate, an ADF, an RDH (recycled document handler), etc. No matter which one is installed, the optimal threshold level can always be set, so the types of documents that can be measured can be increased.

Furthermore, since sheet length detection is always performed under the optimum threshold value, detection accuracy and reliability can be greatly improved.

[Brief explanation of drawings]

FIG. 1 is a front view showing an example of the configuration of a copying machine equipped with a sheet length measuring device according to the present invention, FIG. 2 is a rear view showing the configuration of a drive system inside the same copying machine, and FIGS. 3 and 4 are a front view and a perspective view showing the configuration of the optical scanning system of the copying machine shown in FIG. 1, respectively, and FIGS. 5 and 6 show the first carriage of the optical scanning system shown in FIGS. 3 and 4, respectively. 7 is a plan view showing an example of the operation board of the copying machine shown in FIG. 1; FIG. 8 is a block diagram showing an example of the electric circuit configuration of the copying machine shown in FIG. 1; 9 is an electric circuit diagram showing a configuration example of the document detection board shown in FIG. 8, FIG. 10 is a flowchart showing a schematic operation of the microprocessor 210 shown in FIG. 8, and FIGS. 11 to 14 are the same as in FIG. FIG. 15 is a flowchart showing the general operation of the optical system control board 320 shown in FIG. Flowchart, 1st
FIG. 7 is a flowchart showing an example of a schematic operation when determining a threshold value by the optical system control board 320 shown in FIG.
The figures are graphs showing changes in the output of the optical detection means when measuring the length of the original, FIG. 19 is a graph showing the spectral sensitivity characteristics of the photodiode used as the optical detection means, and FIG.
The figure is a graph showing the spectral reflection characteristics of various sheets, and FIG. 21 is a graph showing the spectral sensitivity characteristics of various light reflecting means. 1...Contact glass, 2...Optical scanning system (
scanning means), 2a...illumination lamp, 3...photosensitive drum, 12...developing device, 51...first carriage, 51b. 51c...hole, 71.72...guide bar,
73.74... Optical fiber, 80... Pressure plate (light reflecting means), 200... Main control board (discrimination means)
, 210... microprocessor, 280...
・Non-volatile read/write memory, 310...Scanning board, 320...Optical system control board (sheet length measuring means, threshold setting means), 360...Document detection board, ENC... Encoder (position signal generation means), KP...key switch, PDI, PD2
...Photodiode (optical detection means), ORG
...Manuscript sheet, Ml, M2. M7...Electric motor, HPI, RPI...Switch. Mamoru) U4σ Saragatazu 40 Horse 47 Phantom 7th □ Time Steel 74 Kaku I Seikyu V Wataru Hakuni 1

Claims (1)

[Claims] an optical detection means provided at a position facing the original sheet; a scanning means for scanning at least one of the original sheet and the optical detection means; and a scanning means for scanning both relative to each other; and a signal according to the position of the scanning means. a position signal generating means for generating a position signal; a light reflecting means for reflecting light of a predetermined wavelength and disposed at a position facing the optical detecting means with the original sheet interposed therebetween; The sheet and the optical detection means are relatively scanned, the scanning position is determined based on the signal outputted by the position signal generation means, and the scanning position is determined based on the result of a comparison between the signal outputted from the optical detection means and a predetermined threshold value. sheet length measuring means for determining the presence or absence of a document sheet and reading the scanning position and detecting the sheet length from the result; determining means for determining the light reflection state of the light reflection means; and means for determining the light reflection state. A sheet length measuring device comprising threshold setting means for changing and resetting the threshold according to the light reflection state determined by.