JP2600076Y2 - Circuit and device for detecting small change in signal in detection device - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit and a detection device for detecting a minute change in a detection signal due to the presence or absence of a transparent object such as a transparent bottle, transparent glass, and film.

[0002]

2. Description of the Related Art Conventionally, when packaging a transparent film or filling a transparent plastic bottle with a liquid in a machine or a factory, the presence or absence of a transparent body such as a transparent film or a transparent plastic bottle is optically determined. To detect
The apparatus shown in FIG. 2 is used.

In this device, a light projecting section (11) constituted by a light emitting diode and a light receiving section (3) constituted by a photodiode are arranged on both sides of a path of an object to be measured.
Thus, a light beam having a pulse waveform is emitted from the light projecting unit (11) to illuminate the light receiving unit (3) to generate a pulse-like detection signal of a current corresponding to the intensity of the light beam. The input detection signal vb is amplified by an amplifying section (6) constituted by an OP amplifier via a DC cutoff capacitor (5), and the amplified output signal Vc is compared with a reference voltage Vo in a comparator (7). As a result of the comparison, the output signal Vc
If the voltage exceeds the reference voltage Vo, the detection output is detected and output.
(8).

In the above conventional apparatus, the detection signal vb at the point B on the input side of the amplifying section (6) is a transparent signal to be measured (2).
There depending on whether existing between the Receiver Emitter (11) (3), the input signal strength as shown in FIG. 3, [Delta] V ₁ changes.
By inputting the detection signal vb to the amplifier unit (6), the output signal V _c is the strength by the presence or absence of the object to be measured is reduced by [Delta] V _2. Since this voltage difference of ΔV _{2 is} the signal change amount due to the beam passing through the transparent object to be measured, the reference voltage Vo of the comparator is intermediate between the signal with and without the object to be measured: for example (Vc - △ is set to V _2/2), it is possible to detect the presence or absence of an object to be measured.

[0005]

[Problems to be Solved] However, since the object to be measured is a transparent body, the signal variation Δ
V ₁ is low, so that the signal ΔV ₂ output is small even when amplified by the amplification section (6). In order to increase the output ΔV ₂ , the light beam of the light emitting section (11) should be strengthened or an amplifier should be used.
(4) It is conceivable to increase the amplification factor of the amplification unit (6). However, if ΔV _{2 is} to be enlarged sufficiently large in order to accurately detect the presence or absence of the transparent body, the semiconductor of the amplification unit (6) is required. Saturates beyond the capacity of the device.

Therefore, even if the light quantity of the light projecting section (11) is increased or the amplification factor of the amplifier (4) or the amplifying section (6) is increased,
When the amplification section (6) is saturated, detection becomes impossible as shown in FIG. That is, even if the detection signal vb changes by ΔV ₁ due to the presence of the object to be measured, the output signal of the output unit (6) does not change and remains in the saturated state, and remains as ΔV ₂ = 0. This is a unique problem caused by the object to be measured being a transparent body.

[0007]

[Problems to be solved by the present invention]
Even if b is amplified, the output signal does not cause saturation in the amplifying section, and the variation Δ
The V _1, proportionally enlarged according to the amplification factor, is intended to clarify the output detecting circuit and a detection device.

[0008]

The present invention relates to a detection circuit for detecting a small change in a signal in a detection device, and amplifies a detection signal vb of an intensity obtained according to a state of a device under test (2). The amplified detection signal Vc is compared with a reference value Vo by a comparator (7), and in a detection circuit that outputs the comparison result, an OP amplifier (6) of an amplification unit (6) is used.
The negative input side of the 1), a resistor R ₃ connected between the constant voltage Vcc, and a resistor R ₄ between the ground and set at the resistor R _3, the connection point of the R ₄ A potential When the value obtained by adding the detection signal vb to Va exceeds the reference voltage Vr of the amplifying section (6), the detection signal is transmitted to the OP amplifier (61).
The values of the resistors R ₃ and R ₄ are determined so as to amplify the current, then the value is compared with the reference voltage Vo by the comparator (7), and the comparison result is digitally output.

Further, the present invention relates to a detecting device for detecting a minute change in a signal, wherein a light projecting unit (1) and a light receiving unit (3) are disposed opposite to each other on both sides of a measurement position for measuring a substantially transparent object to be measured.
An amplifying unit (6) for amplifying a detection signal vb corresponding to the intensity of a light beam detected directly from the light emitting unit to the light receiving unit or passing through the transparent object to be measured according to the presence or absence of the object to be measured; And a comparator (7) for comparing the amplified detection signal Vc with a reference value Vo and outputting the comparison result. The negative input side of the OP amplifier (61) of the amplifier (6) is provided with a constant voltage. while a resistor R ₃ between the vcc, resistor R ₄ is connected to, and the resistor R _3, R ₄ of the value obtained by adding the detection signal vb to set the potential Va at the connection point a between the ground Determine the values of the resistors R ₃ and R ₄ so that the OP amplifier (61) amplifies the detection signal when the voltage exceeds the reference voltage Vr of the amplifier (6). It is characterized by comparison with Vo.

[0010]

[Action] amplifying section (6) connects the resistor R ₃ between the constant voltage Vcc to the negative input of OP amp (61) having an inverting amplifier circuit, and a resistor R ₄ between the ground, When the value obtained by adding the detection signal vb to the set potential Va at the connection point A of the resistors R ₃ and R ₄ exceeds the reference voltage Vr of the amplifier (6), the detection signal is sent to the OP amplifier (6).
By adopting a configuration in which the values of the resistors R ₃ and R ₄ are determined so as to amplify 1), the constant voltage Vcc is distributed on the input side of the amplifier connected to the resistors R ₃ and R _4. The detection signal vb is superimposed on the compressed DC potential Va at the connection point A, and the sum of the detection signal vb and the partial pressure Va at the set point becomes an input signal,
(Vb− | Vr−Va |) is amplified by the amplification unit (6).

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, an amplifying section (6) uses an OP amplifier (61) having an inverting amplifier circuit.
4.5V, constant voltage Vcc = 6V, set voltage Va at connection point A
= 3.8V is set. Therefore, due to the characteristics of the OP amplifier, the amplifying unit does not operate until the potential at the connection point A exceeds 4.5 V.
The output of (6) does not occur. That is, the output signal of the amplifier (6) does not become an output signal until the potential vb of the detection signal superimposed on the connection point A becomes 0.7V.

When the detection signal vb exceeds the level of 0.7 V, the voltage higher than that level is amplified by the amplifying section (6) to become an amplified signal Vc.

Since the input signal of the amplifier (6) is equivalent to increasing the zero level of the input signal to the level of 0.7 V in the conventional circuit, the input signal is supplied to the amplifier as shown in FIG. No saturation occurs. Therefore, the variation ΔV ₁ of the detection signal vb due to the presence or absence of the object to be measured is enlarged to ΔV ₂ . By simply setting the level of the comparison voltage Vo in the comparator (7) between ΔV ₂ , the presence / absence of the object to be measured can be accurately determined, and the detection output section (8) can be operated.

Although the detection circuit and the device according to the present invention accurately detect the presence or absence of a transparent body, the detection target is not limited to this, and is used for applications in which a minute change in a detection signal should be recognized, for example, a minute object. Of course, it can be used for detecting a small temperature change and a slight shape change.

[0015]

[Effect of the Invention] The minute change of the detection signal due to the presence or absence of the transparent body can be amplified by a small amount without causing a saturation state in the amplifying unit, and the setting of the comparator becomes easy, and Since the output signal ΔV ₂ is greatly amplified, the output unit supplied with the output signal ΔV ₂ can be reliably operated.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a detection circuit and a detection device including the same according to the present invention.

FIG. 2 is a schematic diagram of a conventional detection circuit and detection device.

FIG. 3 is a signal diagram at point B and point C for a case where there is no object to be measured and a case where there is an object to be measured, respectively.

FIG. 4 shows points B and C depending on the presence or absence of an object to be measured when the intensity of the detection light beam or the amplification factor of the amplification unit is increased.
It is a wave form diagram of a point.

FIG. 5 is a signal waveform diagram at a point C in a case where there is no measured object and in a case where there is an object to be measured in the circuit and the device of the present invention.

[Explanation of symbols]

 (11) Emitter (2) DUT (3) Light receiver (6) Amplifier (7) Comparator (8) Detector / output

Claims (2)

(57) [Scope of request for utility model registration] 1. Amplifying section (6) amplifies a detection signal vb of an intensity obtained according to the state of a device under test (2), and amplifies the detected signal Vc with a reference value Vo by a comparator (7). comparison, at a detection circuit for outputting a result of the comparison, to the negative input side of the OP amplifier (61) of the amplifier (6) connects the resistor R ₃ between the constant voltage Vcc, the ground the resistor R ₄ is connected between, and when the resistor R _3, the value obtained by adding the detection signal vb to set the potential Va at the connection point a of R ₄ is, exceeding the reference voltage Vr of the amplifier (6) The detection signal is amplified so that the OP amplifier (61) amplifies the detection signal.
Determine the values of the resistors R ₃ and R ₄ , and then the comparator (7)
A detection circuit for detecting a minute change in a signal in the detection apparatus, wherein the detection signal is compared with a reference voltage Vo. 2. A light-emitting unit (1) and a light-receiving unit (3) disposed on both sides of a measurement position for measuring a substantially transparent object, and a light-emitting unit to a light-receiving unit according to the presence or absence of the object. An amplification unit (6) for amplifying a detection signal vb corresponding to the intensity of a light beam detected directly or through a transparent object; and comparing the amplified detection signal Vc with a reference value Vo. Comparative constructed from result comparator (7) for outputting, to the negative input side of the OP amplifier (61) of the amplifier (6) is configured to connect a resistor R ₃ between the constant voltage Vcc,
A resistor R ₄ is connected to the ground, and the resistors R ₃ and R ₄
When the value obtained by adding the detection signal vb to the set potential Va at the connection point A exceeds the reference voltage Vr of the amplifier section (6), the detection signal is amplified by the OP amplifier (61).
Wherein the values of the resistors R3 and R4 are determined and then compared with a reference voltage Vo by a comparator (7).