JPH03188305A - Method and apparatus for detecting thickness of sheet - Google Patents

Abstract

PURPOSE:To detect the thickness of a sheet to be inspected in the light emitting mode corresponding to the kind of the sheet to be inspected by changing over a continuous light emitting mode and a pulse light emitting mode. CONSTITUTION:The first drive circuit 40 converts the emitted light quantity instruction data LD inputted from a CPU 43 to an emitted light quantity signal of a DC level by a D/A converter 400 and allows a light emitting element 8 to continuously emit light in the indicated quantity of light through a transistor 401. The second drive circuit 41 converts emitted light quantity data LD to a pulse signal having the height corresponding to the LD in synchronus relation to the output of a clock oscillator 410 by a D/A converter 413 and drives the light emitting element 8 through a transistor 416. Therefore, the light emitting element 8 emits continuous or pulse-like light corresponding to the instruction of the CPU 43. Transmitted light is detected by a photodetector 9 and compared with a reference value by a comparing circuit 42.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to double feeding of manuscripts, forms, etc.
The present invention relates to a sheet thickness detection method and apparatus suitable for detecting sheet thickness.

[Prior Art] In devices that feed sheets such as manuscripts and forms to the image input section of a copying machine or image reading device, or devices that feed paper on which images are to be recorded to a recording section, these sheets are In order to feed one sheet at a time, it is necessary to detect double feeding in advance.

Therefore, a light-emitting element and a light-receiving element are arranged facing each other on the sheet conveyance path, and when the sheet starts to be fed, the light-emitting element continuously irradiates the sheet with light, and the amount of light emitted is A method has been considered in which the amount of transmitted light passing through the sheet is detected while sequentially changing the number of sheets, and if the amount of transmitted light corresponds to the thickness of two or more sheets, it is determined as double feeding.

In addition, the light emitted from the light emitting element is emitted in a pulsed intermittent light emitting state to irradiate the sheet, and the amount of transmitted light transmitted through the sheet is detected while sequentially changing the amount of emitted light,
If the amount of transmitted light corresponds to the thickness of two or more sheets, a method has been considered in which it is determined as double feeding.

[Problem to be Solved by the Invention 1] In the sheet thickness detection method used to determine double feeding of a sheet as described above, a light emitting element is made to emit light in a continuous light emitting state, and the amount of transmitted light is determined by the sheet thickness detection method. According to the method of detecting whether or not a sheet has a thickness equal to or greater than two sheets, the sheet thickness can be detected at high speed because the amount of emitted light can be continuously varied. However, if the thickness detection range is wide, such as when the thickness to be detected includes thick objects, the light emitting element must emit a large amount of light for thick objects. When a light emitting element emits light in a light emitting state, there is a problem that the life of the light emitting element is shortened and stability is reduced.

On the other hand, according to the method of causing a light emitting element to emit light intermittently, since the light emitting element emits light intermittently, even if the light emitting element is temporarily emitted with a large amount of light, its lifespan will not be reduced. Although it is suitable, there is a problem that it takes time to detect the desired thickness due to the presence of a pause period of light emission, which is related to the thickness.

The present invention was made to solve such problems, and even when the detection range of the thickness of a test sheet is wide, the thickness can be detected stably and at high speed. It is an object of the present invention to provide a sheet thickness detection method and apparatus.

[Means for Solving the Problem 1] The above detection method provides a continuous light emission mode in which the light intensity of the light emitting part is sequentially changed in a continuous light emission state and a pulsed light emission mode in which it is sequentially changed in a pulsed intermittent light emission state. and pulse emission mode to detect the thickness of the sheet to be inspected.

Alternatively, the emission light amount range may be divided into two, and the continuous light emission mode may be selected in the first emission light amount area, and the pulse emission mode may be switched to the pulse emission mode in the second emission light amount area.

Furthermore, the light emitting section may emit light intermittently and the light emitting interval may be changed.

Further, the sheet thickness detection device of the present invention includes a first means for sequentially changing the light amount of the light emitting section in a continuous light emitting state, and a second means for sequentially changing the light amount of the light emitting section in a pulsed intermittent light emitting state.
and controlling the first means to change the amount of light emitted in a first light amount range, and controlling the second means to change the amount of light emitted by the first means in a second light amount range where the amount of light emitted is higher than the first light amount range. a switching means for controlling the amount of emitted light to be changed in the means; a light receiving means for detecting the amount of transmitted light transmitted through the test sheet; and the amount of transmitted light received by the light receiving means and the current amount of emitted light emitted from the light emitting section. and a thickness calculation means for calculating the thickness of the sheet to be inspected based on.

[Function] According to the above configuration, by switching between the continuous light emission mode and the pulsed light emission mode, the thickness of the test sheet can be detected in the light emission mode depending on the type of the test sheet.

In addition, in the range where the thickness of the test sheet is thin, that is, in the first light emission range where the amount of emitted light is small, the thickness of the test sheet is detected in a continuous light emitting state, and as the thickness of the test sheet becomes thicker, the amount of emitted light is In the second light emitting light amount range where the emitted light amount is required to be greater than a predetermined light emitting amount, the thickness of the test sheet is detected in an intermittent light emitting state.

Further, the light emitting section is caused to emit light intermittently, and the thickness of the test sheet is detected while changing the emitting interval.

Therefore, it is possible to stably detect light-emitting elements ranging from thick to thin without reducing their life.

Furthermore, unless the material is thick, its thickness can be detected at high speed.

[Example 1] Hereinafter, the present invention will be described in detail based on an illustrative example.

FIG. 1 is a block diagram showing an embodiment of an image reading system to which the present invention is applied, which includes an image reading device 1 and a sheet feeding device 2 that feeds sheets such as originals or forms to the image reading device 1. and a sheet thickness detection device 4 that detects the thickness of the sheet 3 fed by the sheet feeding device 2.

The sheet feeding device 2 includes two pairs of conveyance rollers 6.7 for feeding the sheet 3 into the paper feed port 5 of the image reading device 1, and also includes two pairs of conveyance rollers 6.7 for feeding the sheet 3 into the paper feed port 5 of the image reading device 1. It includes a light emitting element 8 and a light receiving element 9 for detecting.

After a predetermined period of time has elapsed while the light receiving element 9 detects the leading edge of the sheet 3, the sheet thickness detection device 4 measures the thickness of the sheet 3 passing between the light emitting element 8 and the light receiving element 9 and detects the amount of transmitted light. The details of the detection are shown in FIG. 2.

In FIG. 2, 40 is a first drive circuit that changes the amount of light emitted from the light emitting element 8 in a continuous light emission state, and becomes active when the switching signal SEL is 1".
A DA converter 400 converts the light emitting light amount command data LD input from the PU 43 into a corresponding DC level light emitting light amount command signal, and a drive current corresponding to the light emitting light amount command signal is transmitted to the light emitting element 8 via resistors R1 and R2. The transistor 401 has a transistor 401 that allows current to flow through the transistor 401, and resistors 402 and 403 that control the base current of the transistor 401.

Next, 41 is a second drive circuit that causes the light emitting element 8 to emit light in a pulse-like intermittent light emission state and sequentially changes the amount of light, and includes a clock oscillator 410 that generates a clock pulse of a predetermined period, and a switching signal. S E L to inverter 4
and date 412 which passes the signal inverted at step 11 only when the clock pulse is "i", and when the output signal of this AND date 412 is "i" (S E L =
a DA converter 413 that becomes active when the clock pulse is ``0'' and the clock pulse is 1'') and converts the light emission amount command data LD input from the CPU 43 (to be described later) into a corresponding DC level light emission amount command signal; By inputting the light emitting light amount command signal outputted from this DA converter 413 to the base via resistors 414 and 415, a drive current corresponding to the light emitting light amount command signal is passed through the resistor R7 to the light emitting element 8.
It has a transistor 416 that allows the current to flow.

42 is a comparison circuit that detects whether the amount of light transmitted through the sheet 3 received by the light receiving element 9 has converged to the amount of light corresponding to the thickness targeted for detection, and the upper limit value of the thickness targeted for detection ■u a variable resistor 420 that determines the lower limit value VL, a variable resistor 421 that determines the lower limit value VL, a comparator 422 that sends out an output of '1'' when the amount of transmitted light received by the light receiving element 9 exceeds the upper limit value VU; The amount of transmitted light received is the lower limit\/l
, a comparison 423 that sends out an output of '1' when the value falls below .
and inverters 424 and 42 that invert the output signals of these comparators 422 and 423 and input them to the CPU 43, respectively.
The CPU 43 detects that the output signals of the comparators 424 and 425 have both become i'', that is, that the amount of transmitted light has converged to the amount of light corresponding to the thickness to be detected, and sends a signal OK indicating this to the CPU 43. and date 426 to be input.

43 is the output f of the inverter 424, the output signal LW of the inverter 425, the output signal OK of the AND date 426, and the light emission command data L sent from the first drive circuit 40 to the second drive circuit 41. This is a central processing unit (CPU) that detects the thickness of the sheet 3 based on L'). Note that this CPU 43 includes a clock oscillator 410.
Signals HG and O when the clock pulse is intermittently emitted
It is manually input as a timing signal for sampling K and LW. Further, the CPU 43 outputs a leading edge detection signal of the sheet 3 and a double feed signal to the image reading device.

Here, when detecting the thickness of the sheet 3, the upper limit value u and the lower limit value VIL set by the variable resistors 420 and 421 are set corresponding to a sheet having a reference thickness. Further, when a double feed is detected, a value is set such that an OK signal is sent from the ANDDATE 426 only when one sheet is detected.

Next, regarding the operation related to the above configuration, see 70-- in FIG. 3.
Explain with reference to the chart.

In addition, the following description assumes that the thickness of the test sheet is detected.

First, when the light-receiving element 9 detects the leading edge of the sheet 3, the CPU 43 sends a signal indicating this to the image reading device 1, and after a certain period of time has elapsed, the sheet 3 is connected to the light-emitting element 8 and the light-receiving element 9. While passing through the space, the amount of light emitted from the light emitting element 8 is changed and the thickness of the sheet is detected in the following manner. That is, the continuous light emission mode is set by setting the switching signal SEL to '1'', and the minimum light emission value L + sin in the continuous light emission mode is specified by the light emission quantity specification data LD (step 100).Then, this light emission quantity data LD is converted by the DA converter 400 of the first drive circuit 40 into a corresponding DC level light emission command signal and inputted to the base of the transistor 401.

As a result, the transistor 401 connects the light emitting element 8 to wAr.
5JJ, the light with the minimum light emission amount value 1-1Ilin is emitted. Next, the CPU 43 reads the output signals HG, OK, and LW of the comparator circuit 42 in this minimum light amount state, and when the signal 1-I G = 0'', it is determined that the sheet 3 is too thin and 1' cannot be determined. It is determined that this is the case, and the process ends (step 101).

However, when the signal 1-IG is '1'', it means that the sheet 3 has a certain thickness, so next the switching signal S E L is set to S E I-=''(1'' to switch to the intermittent light emission mode. After switching, the maximum emitted light amount value P max in the intermittent light emission mode is specified by the emitted light amount designation data LD (step 102). Then, this emitted light amount data LD is converted by the I)A converter 413 of the tltJ2 drive circuit 41. It is changed into a light emission command signal having a corresponding DC level and a period corresponding to the period of the clock pulse output from the clock oscillator 410, and is input to the base of the transistor 416.Thereby, the transistor 416 becomes a light emitting element. 8 to cause the light emitting element 8 to emit light having the maximum light amount value Psa for a time corresponding to the period of the tarok pulse.
43 reads the output signals HG, OK, and LW of the comparator circuit 42 in the intermittent light emitting state at the maximum light intensity as in step 101, and when the signal LW is "0", the sheet 3 is too thick to be determined. It is determined that this is the case, and the process ends (step 103).

However, when the signal LW is "1", it means that the sheet 3 has a thickness within the range that can be determined, so next, the specified data LD is set so that the minimum light emission amount value P win in the intermittent light emission state is obtained. is set, and the light-emitting cable 8 is caused to emit light at the minimum light amount value Pll1n for a time corresponding to the period of the clock pulse (Step 7 104).

Then, in this light emitting state, the output signal HG of the comparison circuit 42,
OK, load LW. Among these read signals, signal HG
is 0'', the sheet 3 is considered to be thin, and the switching signal SEL is switched to ``1'' to switch to continuous light emission mode (steps 105 and 106>).

After switching to the continuous light emission mode, next set the data LD so that the maximum light amount value L wax in the continuous light emission mode is set, and set the light emitting cord 8 to the maximum light amount value L wax in the continuous light emission mode.
+eaxt' emit light (step 107 > and
In this light emitting state, the output signal 14G of the comparator circuit 42 is OK,
Read the LW and check whether the signal OK is "1" (step 108). If OK = "1", it is assumed that the thickness is thinner than the target thickness, and the amount of emitted light is reduced to 1.
The step is lowered (step 109), and it is checked whether OK="1" is established again in the new light emission state.

For example, if a sheet with a reference thickness is irradiated with light of the maximum light intensity Lmax in the continuous light emitting state, the upper limit value vU is set by the variable resistor 420, 421 so that the AND date 426 of the comparator circuit 42 outputs a signal OK. and lower limit value V
Suppose that L is set, and the vertical width of the light intensity is 1 per step.
For example, if No. 43 OK is output when the light intensity is lowered by two steps from Lma, the thickness of the test sheet 3 will be 81% (90%) of the standard sheet.
%×90%).

On the other hand, when the signal HG is '1' in steps 105 & 2, it can be assumed that the sheet 3 is thick, so the mode is switched to intermittent light emission mode (step 110), and then the maximum light amount pH lax in the intermittent light emission mode is and minimum light iP+
Set the data LD so that the light intensity is between the in and
The light emitting element 8 is caused to emit light with the intermediate light amount (step 11).
1). In this light emission state, the signal HG is either "0" or "1".
'' (step 7, step 112), and if HG=``O'', lower the light intensity by one level from the intermediate light intensity and check whether the signal OK has become ``1'' (steps 113, 114). Further, in the case of HG=1'', the light intensity is increased by one level from the intermediate light intensity, and it is checked whether the signal OK becomes "1" or not (steps i1s, i16).

Through the processing from step 112 onward, the thickness of the thick sheet is determined in the same way as for the thin sheet.

In this manner, it is possible to easily detect how many times the thickness of the test sheet 3 as the reference sheet is based on the level of the emitted light amount when the OK signal is output.

By using such a detection method, it is possible to easily detect whether or not the sheet 3 has been double fed. That is, according to the above method, when there are sheets having a thickness of A to 13, it is found that the levels of the amount of emitted light when only one sheet is fed are a, +1, and c, respectively. Therefore, when sending a sheet with a thickness of A, data L such that the level of emitted light amount is fixed at a is used.
) is given to the first drive circuit 40 or ttS2 drive circuit 41 which is in charge of this light intensity level, and the light emission amount of the light emitting element 8 is fixed at the level a. In this state, the thickness is A
If two sheets are sent at the same time, the signal is OK.
Since the signal LW becomes "o" without being output, it is possible to detect a double feed. Also, if a large number of sheets of thickness A are sent out one after another, and there are sheets thinner than this,
Since the signal 1-IG becomes "o", it is also possible to detect that thin sheets are mixed.

The way to fix the emitted light amount to a predetermined level with Uni is to check the light intensity level of each sheet and set the CP.
The sheet is stored in the memory 430 in the U 43, and when starting feeding, the user specifies which sheet it is from the operation panel, etc., and the data of the light intensity levels corresponding to the specified contents are successively output from the memory 430. The configuration may be such that it is output as data LD.

Alternatively, when feeding a group of sheets of the same thickness,
It may be configured such that the appropriate light intensity level is checked only for the first sheet, and subsequent sheets are fixed at the light intensity level based on the result of the investigation.

Therefore, if applied to a system that feeds securities or documents by type and reads their contents, reading errors due to double feeding can be prevented, and different types of securities or documents can be mixed. These can be easily removed as foreign substances when they are removed.

By the way, in the thickness detection operation of the circuit shown in FIG. 2, the amount of light emitted by the light emitting element 8 is determined as shown in FIG. If the thickness is , the variation is that the amount of light is sequentially moved up and down in an intermittent or continuous light emitting state, but the present invention is not limited to this variation, and various variations can be implemented. .

Further, the light emission interval in the pulse light emission mode is not constant and may be changed.

Further, in the embodiment described above, a continuous light emission region and a pulsed light emission region are provided, but the thickness of the test sheet may be detected using only pulsed light emission while changing the light emission interval.

[Advantageous Effects of the Invention 1] As described above, according to the present invention, by switching between the continuous light emission mode and the pulsed light emission mode, the thickness of the test sheet can be detected in the light emission mode depending on the type of the test sheet.

In addition, in the range where the thickness of the test sheet is thin, that is, in the first light emission range where the amount of emitted light is small, the thickness of the test sheet is detected in a continuous light emitting state, and as the thickness of the test sheet becomes thicker, the amount of emitted light is In the second light emitting light amount range where the emitted light amount is required to be greater than a predetermined light emitting amount, the thickness of the test sheet is detected in an intermittent light emitting state.

Further, the light emitting section is caused to emit light intermittently, and the thickness of the test sheet is detected while changing the emitting interval.

Therefore, it is possible to stably detect light-emitting elements from thick to thin without reducing their lifetime.

Furthermore, unless the material is thick, its thickness can be detected at high speed.

Then, the light intensity level of the light emitting part corresponding to the detected thickness is determined, so if this light intensity level is fixed, double feeding can be prevented and sheets of different types can be easily excluded. By applying it to systems that read securities and forms, it has an excellent effect of preventing reading errors and the like.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an image reading system to which the present invention is applied, FIG. 2 is a circuit diagram showing the detailed configuration of a sheet thickness detection device, and FIG. 3 is a sheet thickness detection procedure. The flowchart shown is a diagram showing a form of change in light amount of the light emitting section. 1 - Image reading device 2... Sheet feeding device 3... Sheet 4... Sheet thickness detection device 8... Light emitting element 9... Light receiving element 40... r51 Drive circuit 41... f52 Drive circuit 42... Comparison circuit 4: (...Cl) U Fig. 4

Claims (6)

[Claims] (1) In a sheet thickness detection method in which the thickness of the test sheet is detected by the amount of transmitted light transmitted through the test sheet by irradiating light from the light emitting part onto the test sheet and sequentially changing the amount of emitted light, the light emitting part A continuous light emission mode that sequentially changes the light intensity in a continuous light emission state, and a pulsed light emission mode that sequentially changes the light intensity in a pulsed intermittent light emission state. A sheet thickness detection method characterized by detecting thickness. (2) In a sheet thickness detection method in which the thickness of the test sheet is detected by the amount of transmitted light transmitted through the test sheet by irradiating light from the light emitting part onto the test sheet and sequentially changing the amount of emitted light, the light emitting part A continuous light emission mode that sequentially changes the light intensity in a continuous light emission state and a pulsed light emission mode that sequentially changes the light intensity in a pulsed intermittent light emission state are provided.In the first light emission range, the continuous light emission mode detects the thickness of the test sheet. death,
A sheet thickness detection method comprising: detecting the thickness of the sheet to be inspected in a pulsed light emitting mode in a second light emitting light amount region having a higher light emitting light amount than the first light emitting light amount region. (3) In a sheet thickness detection method in which the thickness of the test sheet is detected by the amount of transmitted light transmitted through the test sheet by irradiating light from the light emitting part onto the test sheet and sequentially changing the amount of emitted light, the light emitting part A sheet thickness detection method comprising: emitting light intermittently and detecting the thickness of a sheet to be tested while changing the emission interval. (4) In a sheet thickness detection device that irradiates the test sheet with light from a light emitting part and sequentially changes the amount of emitted light to detect the thickness of the test sheet based on the amount of transmitted light transmitted through the test sheet. a first means for sequentially changing the light amount of the light emitting portion in a continuous light emitting state; a second means for sequentially changing the light amount of the light emitting portion in a pulsed intermittent light emitting state; and in the first light emitting light amount region, the first means a switching means that controls the second means to change the amount of emitted light in a second emitted light amount region where the emitted light amount is higher than the first emitted light amount region; A light receiving means for detecting the amount of light transmitted through the test sheet, and a thickness calculation for calculating the thickness of the test sheet based on the amount of transmitted light received by the light receiving means and the current amount of light emitted from the light emitting part. A sheet thickness detection device comprising means. (5) The thickness calculation means includes a comparison means for detecting whether or not the amount of transmitted light has converged to a light amount value corresponding to a sheet having a reference thickness; 5. The sheet thickness according to claim 4, further comprising calculation means for converting the thickness of the sheet to be detected based on the amount of emitted light when the detection signal from the comparison means indicating that the detection signal has converged. Detection device. (6) The thickness calculation means includes a comparison means for detecting that the transmitted light amount has converged to a light amount value corresponding to the thickness targeted for detection, and a comparison means for detecting that the transmitted light amount has converged to a light amount value corresponding to the thickness targeted for detection, and and a light amount fixing means for fixing the light amount control by the first means or the second means, so that the amount of transmitted light of the test sheet does not converge to the light amount value targeted for detection while the amount of light emitted from the light emitting section is fixed. 5. The sheet thickness detecting device according to claim 4, wherein when the sheet thickness is not detected, a signal indicating that the sheet to be inspected has a thickness other than the thickness targeted for detection is outputted.