JPS61102817A - Photoelectric switch - Google Patents

Abstract

PURPOSE:To compensate appropriately temperature with respect to a logarithm amplifier circuit by connecting output terminals of the logarithm amplifier for converting a reference voltage into logarithm to the reference input terminal of a comparator through a level setting resistance and supplying a current to each resistance from a constant current source. CONSTITUTION:The logarithm amplifier A converts the reference current I0 arising in the constant current source J0 into logarithm. Provided that said amplifier A is composed of an operation amplifier G1 and a silicon diode D1. The output terminal of the amplifier A is connected to the 1st comparator 5 through the resistance R1 and to the 2nd comparator 8 through the resistance R2. The constant current sources J1 and J2 are connected to output sides of the resistances R1 and R2. With this constitution the reference voltage V0 subjected to the logarithm conversion can be obtained by shifting a level by arbitrary amount. When the resistances R1 and R2, or the currents I1 and I2 are made variable, adjustment can be made without affecting adversely other set levels.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Technical Field 1 The present invention relates to a distance detection type photoelectric switch used in parking meters and the like.

[Background technology 1] This type of photoelectric switch, as shown in Fig. 3 (,),
The light beam P is irradiated onto the object to be detected X by the light projector 11 and the light projecting optical system 12, and the reflected light R is collected by the light receiving optical system 1, and the light receiving element 2a or 2 arranged on the light collecting surface is
By comparing the light reception level of b with the reference voltage, it is detected that the distance AIL to the detected object x is within a predetermined range, and the output of the light receiving element 2a or 2b is (
b) As shown in the figure, the light receiving signal voltage is detected because it changes continuously as the condensed light or S moves! II!
It is determined whether the detected object X has entered the detection area by comparing it with the set separation voltage. In reality, in order to cancel out changes in external light and differences in the reflectance of the detected object, the difference signal between the two light receiving elements 2a + 2b is input to the comparison circuit. It is configured so that it can be set at the construction site whether or not to output the information.

Figure 4 shows the circuit configuration of a conventional photoelectric switch, in which the output type 2 of the light receiving element 2 is converted into a voltage signal by the light receiving circuit 31, and the output is converted into a voltage signal by the operational amplifier G0 and the feedback diode D. By performing logarithmic transformation using the amplifier circuit 4, the guinami-no-krenno is enlarged, making it possible to detect from short distances to long distances. This signal is input to the first comparison circuit 5, and the detection level setting circuit 6
It is compared with the detection distance setting voltage Va output from . The signal processing circuit 9 uses the synchronization signal from the oscillation circuit 14 to
The output of the comparator circuit 5 is sampled at the timing when the light beam P is generated from the light projecting element 11 in the drive circuit 13 to remove external light noise, and this signal processing circuit 9
Output circuit 15 consisting of relays etc. and operation display 8
In addition to S16. The margin display section 17 is for displaying whether there is a margin between the light receiving signal voltage and the detection distance setting voltage, in other words, whether cleaning of the lens is required. However, the margin display film constant voltage lT1. which is slightly higher than the above-mentioned detection distance setting voltage \+a. ~b is output, and the second comparison circuit 8 compares the light reception signal voltage with this margin display setting voltage \.b, and the output of the comparison circuit 8 controls the lighting of the 1 millimeter margin display section 17.

However, the above conventional configuration has the following problems. That is, the reason why the detection level setting circuit 6 and the margin level setting circuit 7 are provided individually is that the detection distance setting voltage V
This is to set a and the margin display setting voltage ~b independently of each other, but both setting circuits 6 and 7 are configured as shown in FIG. Then, the signals generated by the constant current sources J, J, are coupled by a logarithmic amplifier consisting of operational amplifiers C, , C, and output/rifing diodes D, , D,! tf: and its output voltages Va and \+b are input to the respective comparison circuits 5 and 8. This is because the logarithmic amplifier circuit 4 utilizes the logarithmic characteristics of the silicon diode, and its temperature characteristics include a change of 18 degrees in temperature due to a change in the temperature of the PN junction.
Therefore, even if a temperature sensing element such as a thermistor is used for setting the reference level, it is impossible to provide the same temperature characteristics as the logarithmic amplifier circuit 4, and the level setting circuit 6 and V 7 i This is because there is no appropriate temperature compensation method unless the same circuit as the two-logarithmic amplifier circuit 4 is used, but providing a logarithmic amplifier for each level setting circuit in this way requires a high-precision operational amplifier. Therefore, there was a problem that it was extremely uneconomical.

[Object of the Invention] The present invention has been made in view of the above-mentioned problems, and its purpose is to be able to perform appropriate temperature compensation for a logarithmic amplifier circuit, and also to An object of the present invention is to provide a circuit configuration of a level setting section that can generate mutually independent reference levels for supplying the signals using a single logarithmic amplifier.

[Disclosure 1 of the Invention According to the present invention, the level of reflected light from the object to be detected is as follows:
The distance to the object to be detected is detected by logarithmically converting it in the l amplifier circuit and comparing it with the detection distance setting voltage in the comparator circuit, and also converting the above 11 number conversion output from the detection distance setting voltage in the comparison circuit @2. In a photoelectric switch, the output terminal of the logarithmic conversion amplifier that converts the reference voltage into N numbers is used to display whether or not there is a margin between the signal level and the operating limit level by comparing it with a slightly higher margin display set voltage. Both of the above comparison circuits through level setting resistors, respectively! The voltage at the output terminal of the logarithmic amplifier in the level setting section is determined by the value of each level setting resistor and the constant current applied to that resistor. Some of them are characterized in that they are not affected by the value of the current supplied from the source.

FIG. 1 shows an embodiment of the photoelectric switch of the present invention, and in FIG.
The output signal Vin is input into the first comparison circuit 5 and compared with the detection distance setting voltage Va, and the second comparison circuit 8 compares the received light signal voltage Vin with the margin setting level ~° In the present invention, the detection distance setting voltage Va and the margin display setting voltage \b are supplied from a single level setting section 10, and the circuit configuration of the circuit is as shown in Fig. 4(a). It's the same.

FIG. 1 (llI) shows the circuit configuration of the level setting section 10, which includes an operational amplifier G and a silicon diode D.
The reference current 1.1 generated by the constant current source J0 by the logarithmic amplifier A of 1. Convert the output terminal to the resistor R
1 to the first comparator circuit 5 and a resistor R2.
is connected to the second comparator circuit 8 through each resistor R, O!
A constant voltage source aj and Va2 are connected to the load side of IR2, respectively. With this configuration, logarithmic amplification can be achieved even if each resistance value changes! 5AI7') Output terminal voltage ■. does not change, and each setting level X/! and vb is Va=Vo+I, XR.

Vb=Vc+I)XRz, and the resistance value R,,R or the current value 1. , [, can be adjusted independently without affecting the set level of the pond. There are several ways to adjust the resistance value, such as switching multiple resistors with a changeover switch, cutting off unnecessary resistors at the construction site, and using a semi-fixed resistor. However, instead of changing the resistance value, do you change the current value of each constant source? You can avoid noise from entering the input terminal of the comparator circuit, which has a very high input voltage, from the volume etc. by rubbing it a little.

In addition, if a photoelectric switch is used in a parking meter, etc., a margin indicator lamp can be used to compare the received light signal level with the margin setting level and issue a warning when there is no margin, and furthermore, the received light signal level can be lowered. In this case, it is necessary to stop the operation of the device to prevent malfunction, and a malfunction prevention voltage Vc is set higher than the detection distance setting voltage Va and lower than the margin display setting voltage.
The third comparison circuit compares the light reception signal voltage \40 with the malfunction prevention voltage ~C. The embodiment shown in FIG. 2(,) can cope with the case where the number of comparison circuits is increased as described above, and even in this case, the constant current sources J175 to J,
By making the voltage ziL value or each resistance value R1 to R1 variable/variable, the setting level of h can be adjusted to 1jl without affecting each other.
can be adjusted. (1+) in the same figure shows the relationship between the light reception signal ~in when detecting an object and various constant voltages ■1 to ■, so the above Va, Vb, and Vc are, for example, v+
This corresponds to +Vs, ■, and ;.

[Effect of the invention 1] As described above, the photoelectric switch of the present invention includes a first comparison circuit that compares the level of reflected light from the detected object with the detection distance setting voltage, and a margin display setting voltage that is slightly higher than the detection distance setting voltage. The output 4 of the logarithmic conversion amplifier for logarithmically converting the reference voltage is connected to the reference input terminal 1 of both comparison circuits via level setting resistors, respectively. Since each resistor 1 is connected to supply a current from a constant current b, only one logarithmic amplifier is used for temperature compensation, and it is supplied to multiple comparison circuits. There is an advantage in being able to generate reference voltages that are different from each other, and also to be able to measure the reference voltages independently from each other.

[Brief explanation of the drawing]

1121(i) is a block diagram of an embodiment of the photoelectric switch of the present invention, (b) is a block diagram of the main part of the same, and FIG.
) is a main part Brorak diagram showing an embodiment of the pond of the present invention, (b)
3(aHb) is an explanatory diagram of the principle of the photoelectric switch used in the present invention, FIG. 4(a) is an overall block diagram of the conventional example, and (b) and (C) are the same as the above. This is a section block. 1 is a light-receiving optical system, 2 is a light-receiving element, 3 is a light-receiving circuit, 4 is a U/1 amplification circuit, 5 is a first comparison circuit, 6 is a detection level setting circuit, 7 is a margin level setting circuit, 8 is a first 2 a comparison circuit, 9 a signal processing circuit, 10 a level setting section, 11 a light projecting element, 12 a light projecting optical system, 13 a drive circuit, 14
is an oscillation circuit, 15 is an output circuit, 16 is an operation display section, 17
That's it! 6 display evil, G Ol (l l I G: is an operational amplifier, D,, D,, D2 is a silicon diode,
Jl to J are constant current sources, R1 to R1 are resistors, Va is a detection distance setting voltage, vb is a margin display setting voltage, A is a photoelectric switch, χ is an object to be detected, P is a light beam, and R is reflected light. Agent Ibuji Ishi 1) Chief 7 Figure 2 (b) Figure 4 L J procedure amendment (spontaneous) December 21, 1980 Advocated Patent Order No. 224554 2, Title of the Invention Photoelectric switch 3, relationship with the case of the person making the amendment Patent applicant location 1048 Kadoma, Kadoma City, Osaka Name Name (583) Matsushita Electric Works Co., Ltd. Representative Iku Kobayashi 4, agent As per the attached document, amended specification special Application No. 59-224554 1, Title of the invention Photoelectric switch 2, Claims (1) The reflected light Δi and ii from the object to be detected are logarithmically converted by a logarithmic amplifier circuit. In the comparator circuit, the "Eri" standard] -52 hi division j [heavy JH upper] 1 - is carried out, and the logarithmic conversion output is compared with the basic level setting voltage of the second comparator circuit U2. In the photoelectric switch, the output terminals of the pair of amplifiers for logarithmically converting the reference voltage are connected to the basic terminals of both of the above comparison circuits through level setting resistors, and current is applied to each resistor from a constant current source. A photoelectric switch characterized in that it is configured to supply electricity. 3. Detailed Description of the Invention [Technical Field] Akira Honji describes a photoelectric switch 1 that utilizes reflected light from an object to be detected. [Background technology 1] This type of photoelectric switch includes a diffuse reflection type that detects the presence of an object based on the presence or absence of reflected light, as shown in Figure 3 (, ), and a diffuse reflection type that detects the presence of an object by the presence or absence of reflected light, as shown in Figures 4 (a) and (b). There is a distance detection type that detects the distance to an object based on the angle of incidence of reflected light on the light receiving section. First, in the diffuse reflection type, as shown in Fig. 3(a), the light receiving element 2 receives the diffuse reflection light from the object surface, converts it into a voltage signal in the light receiving circuit 3, and then logarithmically converts it in the logarithmic amplifier circuit 4. , input this output Vin to the object detection comparison circuit 5,
It compares with a detection level setting voltage Va for adjusting sensitivity, and when Vin is larger, a detection signal is output. The signal processing circuit 9 uses the synchronization signal from the oscillation circuit 14 to
The output of the comparator circuit 5 is sampled at the timing when the light beam P is generated from the light projecting element 11 in the drive circuit 13 to remove external light noise, and this signal processing circuit 9
The output is applied to an output circuit 15 consisting of a relay or the like and a detection display section 16. Further, the margin display section 17 is for displaying whether there is a margin between the received light signal level and the dynamic limit level, in other words, whether or not cleaning of the lens is required. From 7, a tolerance display setting voltage vb, which has a little more margin than the above-mentioned detection level setting voltage Va, is added, and the margin display comparison circuit 8
The light reception signal voltage is compared with this margin display setting voltage vb, and the margin display section 17 is controlled to be turned on based on the output 1 of the comparison circuit 8. Figure (b) shows the configuration of the logarithmic amplifier circuit 4. By logarithmically converting the received light signal output using an operational amplifier G and a feedback diode D, 1) the distance to the object and the detected signal level are The dynamic lens is expanded in proportion to the above, thereby enabling highly accurate detection. However, the above conventional configuration has the following problems. That is, the detection level setting circuit 6 and margin level setting circuit 7 are provided individually because the detection level setting voltage V
This is to set λ and margin display setting voltage vb independently of each other, but both setting circuits 6 and 7 are connected to i The signal generated by the constant voltage ilt source j1 or J2 is logarithmically converted by a logarithmic amplifier consisting of operational amplifiers G, , G and silicon diodes D, , D.
The output voltages Va and vb are input to respective comparison circuits 5 and 8. In other words, the logarithmic amplifier circuit 4 uses the logarithmic characteristics of a silicon diode, and its temperature characteristics depend on changes in carrier concentration due to changes in the temperature of the PN junction. Even if the reference level setting circuit of 2 is constructed with an inexpensive temperature compensation circuit using a thermistor or the like, it is impossible to provide the same temperature characteristics as the logarithmic amplifier circuit 4, and both level setting circuits 6 and 7 This is because there is no appropriate temperature compensation method unless the same circuit as the logarithmic amplifier circuit 4 is used. However, using a logarithmic amplifier for each level setting circuit in this way requires a high-precision operational amplifier for each, which is extremely uneconomical. Next, in the distance sensing type, as shown in Figure 4 (, ), the emitter and receiver are placed side by side at a predetermined distance from each other, and the emitter is placed between the elements 1 and 2.
A light beam P irradiated from 1 through the light projection optical system 12 is diffusely reflected on the surface of the object to be detected X, and when the reflected light R is focused by the light receiving optical system 1, It detects whether or not the detected object X exists in the detection area by utilizing the displacement in 11111 directions according to the distance to the detected object X. The circuit configuration is shown in the same figure (b). As shown, two light-receiving elements 2a are placed in the light collecting plane.
, 2b or the output current of the semiconductor device detection element (PSD) is converted into a signal voltage by the light receiving circuits 3m and 3b, respectively.
Further, the logarithmic amplifier circuits 4a and 4b perform FIL conversion and then input it to the differential amplifier circuit 18, and the difference output is used as the signal human power Vcl of the distance detection comparison circuit 19 and the reference voltage supplied from the detection pressure 1Ill setting circuit 20. It is compared with Vc. In this case as well, one of the two logarithmic conversion circuit outputs, Vin, is manually input to the margin display comparison circuit 8 to display whether there is sufficient margin between the received light signal level and the operating limit level, and further The indicator lamp goes out.From now on, it is necessary to indicate whether or not the received light signal level is higher than the operating limit level to indicate whether or not operation is possible without malfunctioning.For this purpose, a comparator circuit for indicating operation is required. 21 and an operation display section 22 are required. In the above configuration, the input signal Vd of the distance detection comparison circuit 19 is obtained by taking the difference between the outputs of the logarithmic amplifier circuits 4a and 4b, so that the seven temperature errors are canceled out by each other, and therefore the detection pressure B setting circuit 20 does not require a logarithmic amplifier, but the operation level setting circuit 23 and the margin level setting circuit 7 for supplying reference voltages to the operation display comparison circuit 21 and the margin display comparison circuit 8, respectively, include: A logarithmic amplifier is required to compensate for the temperature error of the N-number conversion output Vin, and as in the case of the diffuse reflection type shown in Fig. 3,
There is a problem in that an expensive logarithmic amplifier is required for each setting circuit. [Objective of the Invention 1 The present invention has been made in view of the above-mentioned problems, and its object is to be able to perform proper temperature compensation for an N-number amplifier circuit, and to An object of the present invention is to provide a circuit configuration of a level setting section that can generate mutually independent base levels to be supplied to a comparison circuit of the present invention using a single logarithmic amplifier. [Disclosure of the Invention 1] Accordingly, the present invention converts the received light reflected from the object to be detected into a logarithm in a logarithmic amplifier circuit, and converts the logarithmically converted output into a first In a photoelectric switch that compares a reference level setting voltage and also compares the logarithmically converted output with a second reference level setting voltage in a second comparison circuit, the output of a logarithmic amplifier that converts a base I voltage into a pair!! It has a vf characteristic in that its ends are connected to the reference input terminals of both comparison circuits through h level setting resistors, and current is supplied to each resistor from a constant current source, respectively. The voltage at the output end of the logarithmic amplifier in the level setting section is not affected by the value of each level setting resistor or the value of the current supplied to that resistor from a constant current source. Figure 1 shows an embodiment of the photoelectric switch of the present invention. It is converted into a voltage signal by the logarithmic amplifier circuit 4.
Versus using! The converted output signal Vin is input to the first comparison circuit 5 and compared with the first reference level setting voltage Va, and the second comparison circuit 8 compares the received light signal voltage ν1n with the second reference level setting voltage Va. Compare the voltage vb. These first and second comparison circuits 5 and 8 are connected to the third
In the wave number reflection type embodiment shown in Figure (a), the object detection comparison circuit 5 and the margin display display comparison circuit 8
In the distance detection type embodiment shown in FIG. 4(b), the comparison circuit 21 for displaying operation and the comparison surface for displaying margin! 8, and in the present invention, two types of reference level setting voltages Va and Vb to be applied to these comparison circuits are supplied from a level setting section 10 in a cabinet. Since FIG. 1(b) shows the circuit configuration of the level setting unit 10, the reference current 1° generated by the constant current source J0 is logarithmically converted by a logarithmic amplifier A consisting of an operational amplifier G and a silicon diode D1, and its output is The terminals are connected to the first comparator circuit 5 via a resistor R1, and are connected to the second comparator circuit 8 via a resistor R2, and constant current sources J1 and J2 are connected to the output sides of each resistor R1 and R2, respectively. Connected. With this configuration, each reference level setting voltage Va
and vb is Va=V. +1. XR. Vb=V, +I2XR2, and the logarithmically converted reference voltage ■. can be obtained by level-shifting each by an arbitrary value. Also, the resistance value R,,R, or the current value 1. ．． By making 12 variable, it is possible to adjust each level without affecting the set level of each pond. Further, although the above embodiment uses a single logarithmic amplifier to supply two types of reference levels, for example, In the case of the Maki-reflection type, an operation limit level may be required to indicate whether or not operation is possible at a detection level and a margin level. The embodiment shown in FIG. 2 (&) shows a case where the number of comparison circuits is increased to three or more, and in this case as well, the current values of the constant current fAJ + to J or the respective resistance values R1 to R3 are changed. By making it variable, each setting level can be adjusted without affecting each other. FIG. 5B shows the relationship between the light reception signal Vin and the constant voltages 1 to V at each stage when an object is detected. E Effect of the Invention 1 As described above, the present invention provides a photoelectric switch equipped with a plurality of comparison circuits for comparing the level of reflected light from a detected object with a plurality of reference levels. Since the reference levels can be supplied independently from each other, there is no need to perform temperature compensation for the logarithmic amplifier circuit installed in each comparison circuit to expand the dynamic range of the received light signal, which eliminates the need to provide an individual logarithmic amplifier. This has the advantage that the number of expensive operational amplifiers used can be reduced compared to the conventional example. 4. Brief description of the drawings Figure 1 (&) is a block diagram of an embodiment of the photoelectric switch of the present invention, (1,) is a circuit diagram of the same main part as above, and Figure 2 (a) is a diagram of the photoelectric switch of the present invention. 4 circuit diagrams showing examples of ponds, (
1+) is an explanatory diagram of the same operation as above, and Figure 3 (a) is the conventional TS
A block circuit diagram of the heart switch, (b) and (c) are circuit diagrams of the same essential parts as above, FIG. 1 is a light receiving optical system, 2 is a light receiving element, 3 is a light receiving circuit, 4 is a logarithmic amplifier circuit, 5 is a first comparison circuit or a comparison circuit for object detection, 6 is a detection level setting circuit, 7 is a margin level setting circuit, 8 is a second comparison circuit or a margin display comparison circuit; 9
10 is a signal processing circuit, 10 is a level setting section, 11 is a light emitting element, 12 is a light emitting device, 13 is a drive circuit, 14 is an oscillation circuit, 15 is an output circuit, 16 is a detection display section, 17 is a margin display 18 is a differential amplifier circuit, 19 is a distance detection comparison circuit, 20 is a detection distance setting circuit, 21 is a first comparison circuit or an operation display comparison circuit, 22 is an operation display section, and 23 is an operation level setting circuit. ,A is a logarithmic intensifier,G,,G,,G,
is an operational amplifier, D, , D, , D is a Hanrifun diode, and J1 to J are constant voltages i! Todoroki, R7-R3 is resistance, Vin
is the logarithmic conversion output, Va is the first base level setting voltage,
vb is the second reference level setting, IQ pressure. Agent Patent Attorney Ishi 1) Mr. Nanao, I would like to correct Figures 3 and 4 of the attached drawings as shown in the attached sheet.

Claims (1)

[Claims] (1) The reflected light level from the object to be detected is logarithmically converted by a logarithmic amplifier circuit and then compared with the detection distance setting voltage by a comparison circuit to detect the distance to the object to be detected, and
In the photoelectric switch, the presence or absence of a margin between the signal level and the operating limit level is displayed by comparing the logarithmically converted output with a margin display set voltage slightly higher than the detection distance set voltage in a second comparison circuit, The output terminals of the logarithmic conversion amplifiers for logarithmically converting the reference voltage are connected to the reference input terminals of the above-mentioned comparison circuits via level setting resistors, respectively, and current is supplied to each resistor from a constant current source. A photoelectric switch characterized by: