JPS63314684A - Medium detection circuit - Google Patents

Abstract

PURPOSE:To prevent mis-detection of a medium by correcting a luminous quantity detection signal affected by a voltage fluctuation of a light source and discriminating the detection level of the medium in response to the voltage fluctuation and the luminous quantity fluctuation. CONSTITUTION:A light from a light source 1 is received by a detection sensor 3 and a detection output of a read signal in response to the luminous quantity is obtained by a luminous quantity detection circuit 4. A power reference voltage is supplied from a reference voltage setting circuit 6 to a voltage fluctuation correction circuit 5 and a correction quantity of voltage fluctuation is outputted with a delay corresponding to a thermal inertia of a light source 1. Then a detection output of a luminous quantity detection circuit 4 and a correction quantity of the voltage fluctuation correction circuit 5 and given to an adder circuit 7, from which a detection output with the voltage fluctuation component corrected therein is obtained. A comparator circuit 8 compares the detection output from the adder circuit 7 with a prescribed discrimination level and a medium detection signal is obtained. Thus, the detection signal corrected in following to the luminous quantity fluctuation of the light source is obtained with respect to the fluctuation of the power voltage and mis-detection of the medium is prevented.

Description

[Detailed Description of the Invention] [Summary] The present invention corrects a light amount detection signal due to voltage fluctuations of a lamp light source with thermal inertia in an optical reading device for a medium such as a form to prevent erroneous detection of the medium. This is what I did.

In addition, in optical reading devices, the light intensity detection signal due to voltage fluctuations of a lamp light source with thermal inertia is corrected, and the detection level of the medium is varied according to voltage fluctuations and light intensity fluctuations, thereby preventing media reading errors and double feed errors. This is to prevent detection, etc.

[Industrial application field]

The present invention relates to a medium detection circuit for an optical reading device, and more particularly to a medium detection circuit that can prevent erroneous medium detection due to voltage fluctuations and light amount fluctuations.

[Traditional techniques]

2. Description of the Related Art Conventionally, an optical reader R) or an optical mark reader (OMR) has been known as a device that can read characters or marks written on a medium such as a form and input them into a computer. The reading throat of these optical reading devices is equipped with a medium detection circuit that illuminates the medium with a light source such as a lamp, detects the amount of lamp light by transmission or reflection, and reads characters, marks, etc. on the medium. . This medium detection circuit also detects double feed (feeding of two or more sheets of medium).

[Problem that the invention seeks to solve]

In the media detection circuit of conventional reading devices, when the power supply voltage fluctuates, the electronic circuit responds immediately, but the lamp light source has thermal inertia, so fluctuations occur with a certain delay, and therefore reading is performed based on fluctuations in the lamp output voltage. Functions such as mistakes and double feeds [8] could have occurred.

Furthermore, when detecting double fields, etc., even if the light intensity changes due to deterioration of the light source or the NH main voltage fluctuates, the identification range may become narrower and false detection may occur because the judgment level is constant. Ta.

The present invention has been made to solve these problems, and its purpose is to be able to compensate for fluctuations in the light intensity of the lamp light source even when the power supply voltage fluctuates, and to prevent erroneous detection of media. The object of the present invention is to provide a medium detection circuit that can prevent the above. Furthermore, another object of the present invention is to provide a medium detection circuit that can prevent false detection of double feed due to changes in the light source, fluctuations in power supply voltage, and the like.

[Means for solving problems]

FIG. 1 is a principle block diagram of a medium detection circuit according to the present invention. In the figure, 1 is a light source such as a lamp for the reading head;
2 is a medium such as a form, 3 is a detection sensor, 4 is a detection sensor 3
5 is a voltage fluctuation correction circuit that corrects fluctuations in the power supply voltage supplied to the light source 1 according to fluctuations in the light amount of the light source 1; 6 is a standard for setting the reference voltage of the voltage; A voltage setting circuit; 7 is an addition circuit that adds the outputs of the light amount detection circuit 4 and the voltage fluctuation correction circuit 5; 8 is a voltage setting circuit that compares the output of the addition circuit 7 with a judgment level set to a predetermined value and outputs a medium detection signal; This is a comparison circuit that

FIG. 3 is a block diagram of the principle of the medium detection circuit of the present invention. In the figure, 10 is a detection sensor that detects the light intensity of the light source, 11 is a voltage fluctuation detection circuit that detects fluctuations in the power supply voltage supplied to light source 1, and outputs a judgment level according to the fluctuation to comparison circuit 8, and 12 is a detection sensor. This is a lamp light amount detection circuit that detects the amount of light from the output from the sensor 10 and outputs a determination level according to the amount of light to the comparison circuit 8.

[For production]

In FIG. 1, light from a light source 1 is received by a detection sensor 3, and a light amount detection circuit 4 provides a detection output of a read signal corresponding to the amount of light. In the voltage fluctuation correction circuit 5, the power supply reference voltage is supplied by the reference voltage setting circuit 6, and the voltage fluctuation correction amount is outputted with a delay corresponding to the thermal inertia of the light source 1. Then, the detection output of the light amount detection circuit 4 and the voltage fluctuation correction circuit 5
The correction amount is input to the adding circuit 7, and a detection output with the voltage fluctuation corrected is obtained. A comparison circuit 8 compares the detection output of the addition circuit 7 with a predetermined determination level to obtain a medium detection signal. Therefore, the light source 1
A detection signal that is corrected by following the variation in light amount is obtained, and erroneous medium detection is prevented.

In addition, in FIG. 3, a detection signal that follows the light intensity fluctuation of the light source 1 due to voltage fluctuation is obtained, and the voltage fluctuation detection circuit 11 detects the detection level according to the power supply fluctuation, and the lamp light amount detection circuit 12 detects the deterioration of the light source 1. The lamp light amount detection circuit 12 can obtain a detection level according to the amount of light caused by deterioration of the light source 1, etc. Therefore, a detection signal is obtained that is corrected by following the light intensity fluctuation of light source 1 with respect to the power supply voltage fluctuation, and the detection level is set according to the power supply voltage and light power fluctuation, thereby preventing false detection such as double feed. be done.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a circuit diagram showing a specific configuration of a medium detection circuit in double feed detection. Note that the same parts as in FIG. 1 are denoted by the same reference numerals. In the figure, the reading head section 21 of the optical reading device is connected to a platform 2 through which a medium 2 such as a sheet passes.
A reading hole 23 is formed in 2, a lamp or the like having thermal inertia is disposed as a light source 1 in the upper part of this hole 23, and a detection sensor 3 is disposed as a light receiving part in the lower part. A power supply voltage (5■) is applied to the light source 1, and the medium 2 on the table 22
The passage of is detected by the detection sensor 3.

The light amount detection circuit 4 for detecting the medium 2 includes an amplifier 24 whose non-inverting input terminal is connected to the output terminal of the detection sensor 3 and whose inverting input terminal is grounded via a resistor R1;
4, and a variable resistor VR+ connected between the inverting input terminal of the amplifier 24 and ground.

The voltage fluctuation correction circuit 5 adjusts the power supply voltage (
Variable resistor VR2 connected to one supply terminal of 5)
and a capacitor C, a slow IH amplifier 26 whose output side is connected to a non-inverting input terminal, and whose inverting input terminal is connected to an output terminal, and an output unit of the buffer amplifier 26 is An amplifier 27 connected to an inverting input terminal via a resistor R4 and having a non-inverting input terminal grounded via a resistor R5, and a variable resistor VR3 connected between the inverting input terminal and the output terminal of the amplifier 27. It consists of

The reference voltage setting circuit 6 includes a resistor R6 and a Zener diode ZD connected in series between a negative power supply (-12V) and ground, and a variable voltage regulator connected between the connection point of the resistor lRa and Zener diode ZD and ground. Resistor V R4
and VH2. A sliding terminal of the variable resistor VRa is connected to an inverting input terminal of the amplifier 27.

The adder circuit 7 has an inverting input terminal connected to the connection point of resistors R2 and R3 via a resistor R6, and an output terminal of the amplifier 27 via a resistor R7, and a non-inverting input terminal connected to a resistor R8. an amplifier 28 connected to ground via the amplifier 28;
and a variable resistor VRs connected between the output terminal of the controller and ground. Then, the variable resistor VR of the reference voltage setting circuit 6
The sliding terminal of 5 is connected to the inverting input terminal of amplifier 28 via resistor R9.

The comparison circuit 8 includes an amplifier 129 whose inverting input terminal is connected to the sliding terminal of the variable resistor VR6 via a resistor R+o, and whose non-inverting input terminal is grounded via a resistor R++'; A resistor 3R+2 is connected between the inverting input terminal and the output terminal, the inverting input terminal is connected to the output terminal of the amplifier 29 via the resistor R13, and the non-inverting input terminal is connected in series between the power supply (+5 V) and ground. Connected resistor R+
and a comparator 30 connected to the connection point of
5 V) connected between resistors R15 and R+a.

In the medium detection circuit configured as described above, first, the variable resistor VR2 of the integrating circuit 25 is adjusted, and the time constant is set to match the amount of delay due to the thermal inertia of the light source 1 due to fluctuations in the power supply voltage. Next, the variable resistor VRa of the reference voltage setting circuit 6 is set so that the output terminal voltage of the amplifier 27 becomes 0■ when there is no fluctuation in the power supply voltage. Also, the variable resistor R5 of the base voltage setting circuit 6 adjusts the bias input to the adder circuit. The variable resistor VR6 of the amplifier 28 is set so that the level of the video signal becomes a predetermined value.

In the medium detection circuit, when the power supply voltage fluctuates, the light source 1 does not respond immediately, but is detected by the detection sensor 3 with a predetermined delay, and the detected voltage of the detection sensor 3 is transferred to the light H detection circuit 4. is amplified by the amplifier 24, and the adder circuit 7
is output to the amplifier 28. On the other hand, the voltage fluctuation correction circuit 5
Then, the power supply voltage fluctuation is caused by the variable resistor VR2 of the integrating circuit 25.
is input from the buffer amplifier 26 to the inverting input terminal of the amplifier 27 with a delay determined by the capacitor C. amplifier 27
In this case, since the reference voltage from the reference voltage setting circuit 6 and the output voltage from the buffer amplifier 26 are inverted and added, the voltage obtained by inverting the amount of variation from the reference voltage is added to the amplifier 2 of the adding circuit 7.
8 is output. In the amplifier 28 of the adder circuit 7, the output of the light amount detection circuit 4 and the output of the voltage fluctuation correction circuit 5 are added, so that fluctuations in the power supply voltage are canceled out and a constant output is obtained. The output of the adder circuit 7 is amplified by the amplifier 29 in the comparator circuit 8, and the output is amplified by the amplifier 29 in the comparator circuit 8.
15 to obtain a medium detection signal. Therefore, even if the power supply voltage fluctuates, a corrected detection signal can be obtained that follows the fluctuation in the amount of light from the light source 1, and erroneous medium detection can be prevented.

FIG. 3 is a block diagram showing the configuration of a medium detection circuit according to another embodiment of the present invention. Note that the same parts as in FIGS. 1 and 2 are denoted by the same numbers and detailed explanations are omitted. In the figure, a detection sensor 10 is disposed near a light source 1 to detect deterioration of the light source 1, and the output from this detection sensor 10 is sent to a lamp light amount detection circuit 12 to obtain a judgment level according to the light amount. , are output to the comparison circuit 8. Further, the voltage fluctuation detection circuit 11 obtains a determination level according to the voltage fluctuation, and outputs it to the comparison circuit 8.

In the medium detection circuit having the above configuration, when the fluctuations in the power supply voltage match, as in the embodiment described above, a detection signal that is corrected by following the fluctuation in the light amount of the light source 1 can be obtained.

In addition, as shown in FIG. 4, when the power supply voltage fluctuates or the light intensity fluctuates due to deterioration of the light source, the voltage fluctuation detection circuit 11 or the lamp light intensity detection circuit 12 changes the detection level of the comparator circuit 8 to the same level. In other words, in FIG. 4, between the detection range A for one thick sheet and the detection range B for two thin sheets, there is a sheet detection level line a that corresponds to fluctuations in the power supply voltage or light amount. Therefore, since detection is performed in accordance with voltage fluctuations and fluctuations in the amount of light from the light source, the identification range can be prevented from narrowing, and erroneous detections such as double feed can be prevented.

In the above embodiments, the medium detection signal is used for medium reading, double feed detection, and other medium detection, and is not limited to the embodiments. Further, as long as the detection of the medium is optical, it may be of a transmission type or a reflection type. Furthermore, the voltage fluctuation correction circuit 5 may be of any type as long as it follows a delay in the voltage fluctuation of the light source 1 and corrects the amount of fluctuation.

〔Effect of the invention〕

As explained in detail above, according to the present invention, the variation in light intensity due to voltage variation of the light source is tracked and the amount of variation is corrected, so that there is no influence of voltage variation and erroneous detection of the medium is prevented. be able to.

In addition, it tracks and corrects fluctuations in light intensity, and
Furthermore, since the detection level of the medium is varied in accordance with voltage fluctuations and light intensity fluctuations, narrowing of the identification range is prevented, and misreading of the medium and double feed misdetection can be prevented.

[Brief explanation of drawings]

FIG. 1 is a basic diagram of the medium detection circuit of the present invention, FIG. 2 is a circuit diagram showing the specific configuration of the medium detection circuit in double feed detection of the present invention, and FIG. FIG. 4 is a block diagram of the principle of the medium detection circuit, and is a diagram showing sheet detection levels with respect to power supply and light amount fluctuations. ■...Light source, 2...Medium, 3...Detection sensor, 4...Light amount detection circuit, 5...Voltage change! LJ? iR positive circuit, 6... Reference voltage setting circuit, 7... Addition circuit, 8... Comparison circuit, 10... Detection sensor, 11... Voltage fluctuation detection circuit, 12... Lamp light amount detection circuit. Patent applicant: Fujitsu Machine Electric Co., Ltd. Figure 4 shows the power supply and the 6-sheet detection level fluctuation for the first time in mass production.

Claims (1)

[Claims] 1) Medium (2) by light from the light source (1) of the reading head
a light amount detection circuit (4) that detects a read signal of the light source (1), a voltage fluctuation correction circuit (5) that obtains a correction amount corresponding to a light amount fluctuation due to a fluctuation in the power supply voltage supplied to the light source (1), and the light amount detection circuit A medium detection circuit characterized by comprising an addition circuit (7) that adds the detection output of (4) and the correction amount of the voltage fluctuation correction circuit (5). 2) Medium (2) by light from the light source (1) of the reading head
a light amount detection circuit (4) that detects a read signal of the light source (1), a voltage fluctuation correction circuit (5) that obtains a correction amount corresponding to a light amount fluctuation due to a fluctuation in the power supply voltage supplied to the light source (1), and the light amount detection circuit an adding circuit (7) that adds the detection output of (4) and the correction amount of the voltage fluctuation correction circuit (5); and obtaining a judgment level output according to fluctuations in the power supply voltage supplied to the light source (1). A voltage fluctuation detection circuit (11) and a lamp light amount detection circuit (12) that obtains a judgment level output according to the light amount of the light source (1), and an output of the addition circuit (7) are connected to the voltage fluctuation detection circuit (11) and A medium detection circuit comprising: a comparison circuit (8) for obtaining a medium detection signal by comparing the determination level output of the lamp light amount detection circuit (12). 3) The voltage fluctuation correction circuit (5) is an integrating circuit (25)
and an amplifier (27) for inverting and adding the output of the integrating circuit (25) and a reference voltage.