JPH036485A - object detection device - Google Patents

Abstract

PURPOSE:To enhance the detection accuracy of an object to be detected having high transmissivity and to reduce a detection error by differentiating the light detection signal corresponding to the transmissivity of the object to be detected according to a predetermined time constant before comparing the same with predetermined reference potential. CONSTITUTION:When an object 15 to be detected is inserted between the light emitting circuit 12 and light detecting circuit 13 of a detection part 14, the current value of the circuit 13 is changed and the output of said circuit 13 is amplified to a predetermined value by an amplifying circuit 16 to be supplied to a differentiation circuit 29. This signal is differentiated by the differentiation circuit 29 according to the time constant determined by a resistor and a capacitor and the current values of the starting end and terminal of the object 15 to be detected generated when the object 15 to be detected is inserted are compared with predetermined reference potential by comparing circuits 30a, 30b and the output signals thereof are supplied to a change-over circuit 31 to detect the presence of the object 15 to be detected and a result signal is outputted through an output circuit 17. By this circuit constitution, not only an object to be detected having high shading properties but also an object to be detected having high transmissivity are certainly trapped by a comparator and a detection error can be prevented.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an object detection device such as a sheet of paper, and particularly to an object detection device capable of detecting objects with high transmittance. .

(Prior Art) A conventionally used device for detecting an object to be detected such as a sheet of paper is configured as shown in FIGS. 4 and 5, for example. FIG. 4 shows a block diagram of a conventional object detection device, in which light is emitted from a light emitting circuit 12 in response to an input signal from an input terminal 11. In FIG. A light receiving circuit 13 receives the light generated by the light emitting circuit 12. The light emitting circuit 12 and the light receiving circuit 13 constitute a detection section 4,
Optical coupling is performed between these light emitting circuits 2 and the light receiving circuit 13. The object 15 to be detected is inserted between the detection section 4, that is, the light emitting circuit 12 and the light receiving circuit 13, and the output of the light receiving circuit 13 changes accordingly. There is. The output of the light receiving circuit I3 is amplified to a predetermined value by an amplifier circuit 16, further passes through an output circuit 17, and then output from an output terminal 18.

FIG. 5 is a sectional view showing an example of the configuration of the detection section 14,
For example, a light emitting diode 21 as a light emitting circuit 12 and a light receiving circuit 1 are placed between a concave portion 20 in a housing 19 having a concave cross section.
Phototransistors 22 (No. 3) are arranged facing each other at a predetermined interval. Furthermore, windows 28 and 24 are provided at positions where the light emitting diode 21 and the phototransistor 22 face each other on the fourth part 20 side of the housing 19, and constitute a detection execution section 25.

In the object detection device having such a configuration, the detected object 15
Whether or not paper, for example, is detected is determined by inserting the detected object 15 into the detection section 14, that is, the recess 20 of the housing 19. A constant amount of light is supplied from the light emitting diode 21 arranged across the windows 23 and 24 of the detection execution unit 25 to the phototransistor 22, and when the detected object 15 blocks this light, the amount of current changes. The presence or absence of detection is then determined. That is, the light receiving circuit 13 in FIG.
Referring to the output characteristic diagram of the phototransistor 22, for example, when there is no detected object 15, that is, when there is no detected object 15 in the detection execution unit 25, the characteristic is as shown by curve A. Here, when the object to be detected 15 is paper with high light-shielding properties, a characteristic shown by a curve B having a smaller amount of current than the curve A is obtained. Therefore, the presence or absence of the detected object 15 is determined by the difference in the amount of current of the light receiving circuit 13.

(Problem to be Solved by the Invention) However, as described above, when the presence or absence of the detected object 15 is determined based on the difference in the amount of current of the light receiving circuit 13, the detected object 15 is transparent. Problems arise in some cases. For example, if the detected object 15 is a film with high light transmittance such as 0HP (overhead projector) paper, even if the detected object 15 is present in the detection execution unit 25, light will not be transmitted from the light emitting diode 21 to the phototransistor 22. is almost reached.

Therefore, in the film, as shown by curve C in FIG. 6, the current value is close to that in the case where there is no object to be detected. Moreover, this current value varies widely due to the optical coupling characteristics of the detection execution section 25, and changes depending on the transmittance of the object to be detected 15. Therefore, even if the detected object 5 exists in the detection execution unit 25, the detection unit I4 actually detects the detected object 1.
Assuming that 5 is not present, a large number of detection errors may occur.

In order to solve this detection error, an object detection device as shown in FIG. 7 is used which mechanically and indirectly detects the object 15 to be detected. That is, similar to the conventional example shown in FIG. 5, a light emitting diode 21 and a phototransistor 22 are arranged facing each other in a housing 19'. A mounting portion 28 that engages with the support shaft 27 of the actuator 26 is provided at the top of the housing 19'. The actuator 2B rotates about the support shaft 27 so as to be able to block light from the detection execution section 25 between the light emitting diode 21 and the phototransistor 22 which are arranged facing each other. That is, when the object 15 to be detected is transported, its tip comes into contact with one end of the actuator 26 . Then, the other end of the actuator 26 blocks the detection execution section 25 and changes the output current of the phototransistor 22. The presence of the detected object 15 is revealed by the collector.

However, in this method of using the actuator 26, the apparatus has a problem in that the detection accuracy is poor because the actuator is interposed between the detected object 15 and the detection execution unit 25. Further, there also arises the problem of increased manufacturing cost of the detection device.

Furthermore, in order to solve the above-mentioned detection error, it is possible to consider a method that enables linear detection by suppressing variations in the optical coupling characteristics due to variations in the output of the light emitting diode and the sensitivity of the phototransistor, for example. In addition to requiring the selection of
The problem arises that it leads to

This invention was made in view of the above points, and it is an object detection method that increases detection accuracy and reduces detection errors even if the object to be detected has a high transmittance, and does not increase costs. The purpose is to provide equipment.

[Structure of the Invention] (Means for Solving the Problems) In other words, the object detection device of the present invention generates a photocurrent by receiving light from a light emitting means generated by an input signal. a light receiving means for outputting a signal according to a change in the current of the detected object when the detected object blocks the light from the light emitting means; and a differentiating means for differentiating the signal from the light receiving means with a predetermined time constant. , a comparing means for supplying a signal representing the detected object according to a comparison result of the signal differentiated by the differentiating means with a predetermined reference potential; and a comparing means for supplying a signal representing the detected object supplied from the comparing means. By providing a switching means that recognizes whether or not the object to be detected is detected by switching, an object detection device with high detection accuracy is realized.

(Function) The object detection device includes a light emitting means that generates light in response to an input signal, and a light emitting means that receives light from the light emitting means by blocking the light from the light emitting means to be detected. A light receiving means that generates a photocurrent and outputs a signal outputs a signal corresponding to the transmittance of the object to be detected, and a differentiating means that differentiates the signal from the light receiving means with a predetermined time constant; and a comparison means for supplying a signal representing the detected object according to a comparison result of the signal differentiated by the means with a predetermined reference potential, ensuring that the detected object is detected regardless of the transmittance. The switching means for switching the signal representing the object to be detected supplied from the comparing means makes it clear the starting and ending ends of the object to be detected, and therefore the accuracy of the object to be detected is determined regardless of the transmittance. can ensure high detection.

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

Incidentally, in this embodiment, the same parts as in the above-mentioned conventional example are given the same reference numerals, and the explanation thereof will be omitted.

FIG. 1 shows a block diagram of an object detection device according to an embodiment of the present invention, in which light is generated from a light emitting circuit 12 in response to an input signal from an input terminal 11. As shown in FIG. This light emitting circuit 12 constitutes a detection section 14 together with a light receiving circuit 13, and the light generated by the light emitting circuit 12 is supplied to the light receiving circuit 13 through optical coupling.

Then, the object 15 to be detected is detected by the detection unit 1
The light receiving circuit 13 is inserted between the light emitting circuit 12 and the light receiving circuit 13 of No. 4, and the output of the light receiving circuit 13 changes accordingly. The configuration of the detection unit 14 is the same as that of the conventional example shown in FIG. 5, so the explanation will be omitted here.

The output of the light receiving circuit 13 is amplified to a predetermined value by an amplifier circuit 16 and then supplied to a differentiating circuit 29. Then, the signals differentiated by the differentiating circuit 29 are transferred to the comparing circuits 30a and 3.
0b. These comparison circuits 30a and 30b are for comparing the values at the start and end ends of the detected object 15 with a predetermined reference value when the detected object 15 is inserted into the detection section 14, respectively. The signals output from the comparison circuits 30a and 30b are supplied to a switching circuit 31 to determine the presence or absence of the object to be detected, and a signal resulting from this determination is outputted from an output terminal 18 via an output circuit 17.

FIG. 2 shows an example of the differential circuit 29, comparison circuit 30a, and 30b1 switching circuit 31 described above.

A signal input from the amplifier circuit 16 is input to the negative input terminal of the operational amplifier 32 via a resistor Rs and a capacitor Cs connected in series. The positive input terminal of the operational amplifier 321 is grounded, and the feedback resistor Rf is connected between the output terminal and the negative input terminal.

The output signal of this operational amplifier 32 is sent to a comparator 33a.
and the negative input terminal of the comparator 33b, respectively.

Negative input terminal of comparator 33a and comparator 3
Power supplies 34a and 34b of the illustrated polarity are connected to the positive input terminal of 3b, respectively. Also, comparator 33
The signal from the output terminal of the comparator 33b is supplied to the reset input of the flip-flop 35, and the signal from the output terminal of the comparator 33b is supplied to the set input of the flip-flop 35. And the Q output of this flip-flop 35 is
The signal is supplied to the output circuit 17 as a signal indicating that the detected object 15 has been determined.

Next, the operation of the present invention will be explained with reference to FIGS. 3(a) to 3(e). In FIGS. 3(a) and 3(b), solid lines represent objects to be detected such as highly transparent films, and dotted lines represent objects to be detected that are highly light-blocking.

In the object detection device having such a configuration, detection of the detected object 15, such as paper, is performed by inserting the detected object 15 into the detection section 14, as described above. When the detected object 15 blocks the light from the light-emitting circuit 12, the amount of current in the light-receiving circuit 13 changes, and the presence or absence of detection is determined.

When the output signal of the light receiving circuit 13 is amplified by the amplifier circuit 16 at a predetermined amplification factor, the characteristics shown in FIG. 3(a) appear.

That is, time t. From time to time t1, a signal with a predetermined current value is output from the amplifier circuit 16.

Then, at time t1, when the object 15 to be detected, such as a highly transparent film, reaches the detection execution unit 25 and blocks the light from the light emitting circuit 12 in the detection unit 14, the amount of current supplied to the light receiving circuit 13 decreases. Decrease. Next, when the terminal end of the detected object 15 passes through the detection execution unit 25 at time t2, the photocurrent of the light receiving circuit 13 and the output current of the amplifier circuit 16 increase again.

The signal output from this amplifier circuit 16 is differentiated according to a time constant determined by a resistor Rs and a capacitor Cs.

Referring to FIG. 3(b), at time 3 tl and time t2, pulses α or α' (tl) and β or β' (t2) are generated depending on the amount of change in the photocurrent as shown in the figure, respectively. . The amplitudes of these signals are
It differs depending on the transmittance of the object 15 to be detected.

By the way, when the starting end of the detected object 15 reaches the detection execution section 25 at time t1, the comparator 33 is activated by the signal α or α' indicating that the detected object 15 has been inserted.
The peak value of the signal α or α' at the voltage source 34b becomes lower than the reference potential v7□ of the power supply 34b. Then, this causes the third
A pulse (= sign α') as shown in FIG.
Since the reference potential of a is set to (+) VTI, the output does not change (see FIG. 3(d)).

Next, at time t2, the terminal end of the detected object 15 is detected by the detection execution unit 2.
5, the signal β or β' shown in FIG. 3(b) is input to the comparator 33a.

Here, when the peak value of the signal β or β' exceeds the reference potential VT1 of the power supply 34a, a pulse signal β' as shown in FIG. 3(d) is outputted to the 4 output of the comparator 33a. At this time, in the combiner 933b, the reference potential of the power supply 84b is (-) VT2, so the output does not change (see FIG. 3(c)).

Comparators 33a and 33 that change in this way
The output signals of b are supplied to the reset input and set input of the flip-flop 35, respectively. That is, the signal shown in FIG. 3(C) is supplied to the set input of the flip-flop 35, and the signal shown in FIG. 3(d) is supplied to the reset input thereof. The flip-flop 35 detects the detected object 15
is detected (time t1), a signal (α
') is input, so the Q output becomes "1". On the other hand, when the detected object 15 passes through the detection execution unit 25 (
At time t2), the signal (β') is input to the reset input, so the output becomes "0". That is, the detected object 15
Yes if the presence or absence of is "1", absent if it is "0",
It can be determined in this condition.

The output signal of this flip-flop 35 is supplied to the output port 5 17, and the output circuit 17 is driven by this signal. Here, the output of the flip-flop 35 is inverted using, for example, an inverting circuit, as shown in FIG. 3(e).
FIG. In this case, the state where the detected object 15 is absent (time t.-tl and after time t2) is high level, and the state where the detected object 15 is detected (time t1 to t2) is high level.
2) is determined as low level.

According to the above circuit configuration, the presence or absence of the detected object can be detected reliably by the comparator, even if the detected object has a high light-shielding property, as well as a detected object with high transmittance such as a film. Errors can be improved.

In addition, since the detection section detects the presence or absence of the object to be detected by detecting a sharp change in photocurrent, it is not effective against the long-life coupling characteristics of conventional methods. be.

The circuit configurations of the differentiating circuit, comparison circuit, and switching circuit are not limited to the embodiments described above, and can be modified in various ways without departing from the gist of the invention.

[Effects of the Invention] As described above, according to the present invention, by employing a light-receiving semiconductor element, an object with high transmittance, which was conventionally difficult to detect directly, can be detected without using an actuator. This makes it possible to reduce costs.

Furthermore, since no actuator is used, the resolution is much higher than that of object detection devices that use actuators.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram of an object detection device according to an embodiment of the present invention, FIG. 2 is a circuit configuration diagram showing an example of the differential circuit, comparison circuit, and switching circuit of FIG. 1, and FIG. 3(a) ~(e
) is an output characteristic diagram explaining the operation, FIG. 4 is a block configuration diagram showing an example of a conventional object detection device, FIG. 5 is a sectional view showing an example of the configuration of the detection section in FIG. 4, and FIG. FIG. 4 is an output characteristic diagram of the light receiving circuit, and FIG. 7 is a side view showing another example of the conventional object detection device. 7 12... Light emitting circuit, 13... Light receiving circuit, 14...
Detection unit, 15... Object to be detected, 16... Amplification circuit, 1
7... Output circuit, 29... Differential circuit, 30a,
Bob...comparison circuit, 31...switching circuit.

Claims (7)

[Claims] (1) A light emitting means that generates light in response to an input signal, and a device that generates a photocurrent by receiving light from the light emitting means, and when an object to be detected blocks the light from the light emitting means to be detected. A light receiving means for outputting a signal corresponding to a change in the current of the object to be detected, a differentiating means for differentiating the signal from the light receiving means with a predetermined time constant, and a signal differentiated by the differentiating means at a predetermined reference potential. a comparison means for supplying a signal representing the detected object according to a comparison result with the detected object; and recognizing whether or not the detected object is detected by switching the signal representing the detected object supplied from the comparing means. An object detection device comprising: switching means. (2) The predetermined reference potential includes at least a first and a second reference potential, and the comparing means compares the signal differentiated by the differentiating means with the first reference potential, and
a first comparing means for supplying a signal; and a second comparing means for supplying a second signal as a result of comparing the signal differentiated by the differentiating means with the second reference potential. The object detection device according to claim 1, characterized in that: (3) The first and second comparing means respectively supply the first and second signals representing the starting and ending ends of the detected object when detecting the detected object, respectively. The object detection device according to claim 2. (4) The first and second comparing means are constituted by first and second comparators, and if the signal from the differentiating means is lower than the first reference potential, the first comparator 4. An object according to claim 3, characterized in that it provides a first signal, and the second comparator provides the second signal if the signal from the differentiating means is higher than the second reference potential. Detection device. (5) The first and second comparing means are constituted by first and second comparators, and the first comparator selects the first reference potential when the signal from the differentiating means is higher than the first reference potential. 4. An object according to claim 3, characterized in that the second comparator supplies a first signal, and the second comparator supplies the second signal if the signal from the differentiating means is lower than the second reference potential. Detection device. (6) The switching means indicates that the detected object is detected by switching to the first signal supplied from the comparing means, and indicates that the detected object is detected by switching to the second signal. 3. The object detection device according to claim 2, wherein the object detection device indicates that the object is not detected. (7) The object detection device according to claim 6, wherein the switching means is comprised of a flip-flop.