JPH0259514B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a device such as an optical character reading device that processes information by transporting paper sheets along a predetermined transport path, and particularly relates to a device for processing information by transporting paper sheets along a predetermined transport path. The present invention relates to a two-sheet feeding detection device that detects presence or absence and two-sheet feeding using transmitted light.

[Technical background of the invention]

Optical character reading devices and the like cannot read data correctly if paper sheets with information written on them are conveyed in a stacked state, so a device is provided to detect double-sheet feeding. FIG. 1 is a circuit diagram of a configuration example of a conventional device. The difference in ream weight of paper sheets is detected as a change in transmitted light by a combination of a light emitting diode LED1 and a photocell CELL1. However, since the characteristics of light emitting diodes and photocells vary depending on temperature, a light emitting diode LED2 and a photocell CELL2 are provided for temperature correction in order to obtain a stable output regardless of temperature changes. Note that a constant voltage V _c is applied to the light emitting diodes LED1 and LED2 through resistors R1 and R2 having the same resistance value, respectively.

The output currents of the photocells CELL1 and CELL2 are determined by a differential input type operational amplifier and resistors R3 and R4, respectively.
Amplifier circuit AMP1, AMP composed of RV1
2, where it is current/voltage converted and amplified. The voltage outputs of the amplifier circuits AMP1 and AMP2 are applied to the differential amplifier circuit AMP3 via resistors R5 and R6 having the same resistance value. The output voltage of the differential amplifier circuit AMP3 is the constant voltage V _c RV2
The slice level voltages VSL1 to VSLN obtained by resistor division by ~RVN+1 etc. are input to one terminal of each of the comparators COMP1 to COMPn, which are input to the other terminal of each of them. Detected. The output can be corrected due to temperature changes by adjusting the value of the resistor RV1 of the amplifier circuit AMP2.
The output was kept constant.

[Problems with background technology]

However, in the conventional device as described above, the drive current for the light emitting diodes LED1 and LED2 is supplied through separate circuits, so a difference appears in the amount of light emitted from the light emitting diodes LED1 and LED2 due to fluctuations in the power supply voltage, etc. The problem was that it would incorrectly detect two sheets being fed. Furthermore, if the drive currents are different from each other, the light emitting amounts of the light emitting diodes LED1 and LED2 will vary depending on the temperature, and the resulting increase in the difference between the outputs of the amplifier circuits AMP1 and AMP2 will be amplified by the differential amplifier AMP3. That will happen. For this reason,
This has the drawback that the margin with respect to the slice level voltage for detecting two-sheet feed is reduced, resulting in one paper sheet being erroneously detected as two sheets.

[Purpose of the invention]

The present invention has been made in order to overcome the drawbacks of the conventional devices as described above, and it is an object of the present invention to provide a two-sheet feed detection device that does not malfunction even when there are fluctuations in power supply voltage, changes in ambient temperature, etc. With the goal.

[Summary of the invention]

In order to achieve the above object, the present invention uses a single constant current source as a light source that provides light to a first light receiver for detecting transmitted light from conveyed paper sheets and a second light receiver for temperature correction. The gain of the detection amplifier circuit that converts and amplifies the output of the first photodetector into current/voltage can be switched to two levels, high and low. By making it possible to continuously change the gain of the temperature compensation amplifier circuit that converts and amplifies the output of the device into current and voltage, and by comparing the output voltages of these amplifier circuits with each other, it is possible to convey paper sheets. The present invention provides a two-sheet feeding detection device that can detect the presence or absence of two-sheet feeding.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 2 to 6 of the accompanying drawings. FIG. 2 is a circuit diagram of the same embodiment, in which the same elements as in FIG. 1 are designated by the same symbols. The light emitting diodes LED1 and LED2 are supplied with drive current from the same power source _Vc , and the constant current drive circuit 1 connected in series is provided with a mechanism that can control the drive current value to a constant value. The amplifier circuit AMP1 that converts and amplifies the output current of the photocell CELL1 has a transmitted light detection resistor R7 and an adjustment resistor R8 (R7>
R8) and a switch sw for switching this. Furthermore, the amplifier circuit AMP2 that converts and amplifies the output current of the photocell CELL2 is provided with a variable resistor RV1 for adjusting the outputs of AMP1 and AMP2 to be the same.

The output of the amplifier circuit AMP1 is input to one terminal of four (not limited to) comparators COMP1 to COMP4, and the output of the amplifier circuit AMP2 is input to the resistor R1.
Resistance divided by 1 to R14 and comparator
It is given to the other terminal of COMP1 to COMP4.
In addition, the voltage drop value due to resistors R11 to R14 is
_V2 to _V5 .

Next, the adjustment operation of the circuit shown in FIG. 3 will be explained.
Since equal constant current is supplied to the light emitting diodes LED1 and LED2, the amplifier circuits AMP1 and AMP2
A constant voltage appears on the output side of. During normal operation (for example, when paper sheets are transported and data can be read), the switch SW is connected to the resistor R7, and a voltage drop occurs due to the resistor R7 and the photocell CELL1. Although it depends on the voltage value of the power supply, in general, when there is no paper sheet (when the light from the light emitting diode LED1 directly reaches the photocell CELL1), the output of the amplifier circuit AMP1 is at a saturated output voltage close to the power supply voltage value. . However, when there is a paper sheet (when the paper sheet blocks the light from the light emitting diode LED1), the output of the amplifier circuit AMP1 is at a predetermined voltage E1 that is below the saturation output voltage.

In order to adjust the output of the amplifier circuit AMP1 to a predetermined voltage, first turn the switch SW and connect the resistor R.
Connect 8. Here, the magnitude of the resistor R8 (R7>R8) is set to such a value that the output of the amplifier circuit AMP1 is not saturated due to the voltage drop caused by the resistor R8 and the photocell CELL1. Then, by adjusting the drive current value by the constant current drive circuit 1, the amplifier circuit AMP
1 is made equal to a predetermined voltage E1.

When the output of the amplifier circuit AMP1 has been adjusted as described above, the switch SW is switched to the resistor R7, and the magnitude of the variable resistor RV1 is adjusted so that the output of the amplifier circuit AMP2 becomes the predetermined voltage E1. When this adjustment is completed, as shown in FIG.
Slice level voltages E2 to E4 for two-sheet feeding detection of the comparators COMP2 to COMP4 are obtained by the voltage drops _V2 to _V5 caused by R1 to R14. As described above, the output can be easily adjusted without actually transporting paper sheets.

FIG. 4 is an explanatory diagram of the two-sheet feed detection operation according to the embodiment shown in FIG. The output of the amplifier circuit AMP1 is when there is no paper sheet, when there is one sheet of 55Kg paper, and when the output is 55Kg.
The level changes depending on the state of the two sheets of paper. The comparator COMP1 changes the output from a high level (hereinafter referred to as "H") to a low level (hereinafter referred to as "L") when the output of the amplifier circuit AMP1 becomes less than a predetermined potential E1, and outputs a single sheet of paper. When the output of the amplifier circuit AMP1 becomes less than the slice level voltage E2, the comparator COMP2, which indicates that the two sheets have been conveyed, changes its output from "H" to "L", indicating that the two sheets have been conveyed. Let me know.
Although only 55 kg paper is explained in FIG. 4, paper sheets of other ream weights are detected in the same manner using the slice level voltages E3, E4, etc.

Next, the operation of the embodiment shown in FIG. 2 when the ambient temperature rises will be explained. FIG. 5 is an explanatory diagram of the operation of the conventional device shown in FIG. 1, and FIG. 6 is an explanatory diagram of the operation of the embodiment of the present invention shown in FIG. 2, and these will be explained in comparison.

In the conventional device shown in Fig. 1, when the temperature rises, the amplifier circuit AMP1,
The difference between the outputs of AMP2 increases, and thereby the output of differential amplifier circuit AMP3 changes. Therefore, the output of the differential amplifier circuit AMP3 shifts to the level indicated by the dotted line in FIG. 5. Therefore the slice level voltage
The ratio of the margin e1 of VSL1 and one sheet of 55Kg paper to the margin e2 of two sheets of 55Kg paper (e1≒e2) is e2'>
e1', and if the margin for two-sheet feed detection is insufficient and the paper moves vertically during conveyance, it may be mistakenly detected as two 55 kg sheets when it is one 55 kg sheet. be.

On the other hand, in the embodiment shown in FIG. 2, the output of the amplifier circuit AMP1 decreases in each case as shown by the dotted line in FIG. 6, but the output of the amplifier circuit AMP2 also decreases in the same way, so the slice level voltage E2
decreases as well. Therefore, the margin between the adjusted slice level voltage E2 and one sheet of 55 kg paper is
There is no difference between e1, the margin e2 between the slice level voltage E2 and two sheets of 55 kg paper, and these margins e1' and e2' when the temperature changes (e1≒
e1′, e2≒e2′) Stable two-sheet feed detection is possible.

Note that even when the temperature drops, stable operation can be achieved without changing the margin. Also,
Even when the power supply voltage fluctuates, constant current is applied to the light emitting diodes LED1 and LED2 by the constant current drive circuit 1, so that a stable and constant output can be obtained from the amplifier circuit AMP1.

〔Effect of the invention〕

As described above, according to the present invention, a constant current can be supplied to the light source composed of a light emitting diode, etc., so that stable operation can be achieved regardless of fluctuations in the power supply voltage, and the detection amplifier circuit and Since we have provided a mechanism to adjust the output of the correction amplifier circuit to a predetermined voltage, it is possible to adjust the output without actually transporting paper sheets. Since the voltage is compared with the output of the resistor-divided correction amplifier circuit, it operates stably even when the ambient temperature changes, and detects two-sheet feeding without falsely detecting two-sheet feeding. You can get the equipment.

Furthermore, the present invention can be realized with a simple circuit and is therefore inexpensive.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of one configuration example of a conventional device, FIG. 2 is a circuit diagram of an embodiment of the present invention, and FIGS.
The figure is an explanatory diagram of the operation of the embodiment shown in Fig. 2, Fig. 5 is an explanatory diagram of the operation of the configuration example shown in Fig. 1 when the temperature changes, and Fig. 6 is an explanatory diagram of the operation of the embodiment shown in Fig. 2. It is an explanatory diagram of the operation at the time. 1... Constant current drive circuit, AMP1, AMP2...
Amplifier circuit, AMP3...Differential amplifier circuit, COMP1
~COMPn……Comparator.

Claims (1)

[Claims] 1: a light source; a first light receiver that receives the light from the light source that has passed through the paper sheets being conveyed; and converting the output of the first light receiver into current/voltage;
a first amplifying means capable of switching the gain into at least two stages of high and low; and when the first amplifying means has a low gain;
adjusting means for adjusting the amount of light emitted from the light source so that the output of the amplifying means becomes a predetermined value; a second light receiver for receiving the light from the light source; Converted,
second amplification means whose gain can be adjusted so that the output becomes the predetermined value when the first amplification means has a high gain; and a plurality of comparators that respectively compare the outputs of the second amplifying means, and detects the presence or absence of paper sheet conveyance and two-sheet feeding based on the outputs of the plurality of comparators.