JPS59202731A - Photoelectric switch - Google Patents

Abstract

PURPOSE:To correct properly a temperature drift of a logarithmic amplifying circuit, and to make an operating level of a comparing circuit constant by forming a reference voltage generating means by using a circuit being equal to a logarithmic amplifying circuit for an output of a photodetecting circuit. CONSTITUTION:As for logarithmic amplifying circuits 80, 90 for forming a reference voltage generating means of a malfunction preventing means 8 and a surplus display means 9, those which are equal to a logarithmic amplifying circuit 22b of a distance measuring control means 5 are used, and temperature drifts of these logarithmic amplifying circuits 22b, 80 and 90 are equal. Accordingly, even in case when a temperature drift of the logarithmic amplifying circuit 22b is large, the same temperature drift is generated in the logarithmic amplifying circuits 80, 90 of the reference voltage generating means, too, therefore, a relative value of a voltage level applied to both input terminals of a comparing circuit consisting of comparators G8, G10 is not varied, a substantial operating level of the malfunction preventing means 8 and the surplus display means 9 is not varied by a temperature, and a stable operation is executed.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to a photoelectric switch.

[Background technology]

In the past, as shown in FIG.
In this type of photoelectric switch, in which the logarithmic amplification is performed by the comparator circuit and the fault-proof amplification is performed by the comparator circuit, the reference voltage V8 that sets the operating level of the comparator circuit (to) is the power supply voltage VC.
It was formed by dividing the voltage using the Of resistors (Ra) (Rb).

By the way, in such a conventional example, the logarithmic increase time 19
! In order to correct the temperature drift of 221, a resistor (Ra
) (Rb), it is necessary to use a temperature-sensitive resistor to change the reference voltage vs in response to the temperature drift of Width circuit - Temperature characteristics equivalent to 4? It is difficult to hold back, until now.
The response speed of the thermal resistor is slow (usually 20 seconds or more)
Therefore, it is not possible to properly control the temperature drift of the circuit in the logarithmic term. If the temperature drift of the logarithmic amplifier circuit cannot be corrected, this type of comparison circuit V
There was a problem that the output circuit controlled by the 6tZa+ output, the malfunction prevention means, the margin display means, etc. did not operate stably. It should be noted that the circuit in the pair is formed of an operational amplifier (G6) and a junction diode (D), and uses the voltage-current characteristics of the diode (D) to obtain logarithmic amplification characteristics. In this case, the diffusion current I of the diode (DJ is 1
= I o CeXp('t V / k T )
-1], q: elementary charge, k: Bormann's constant, and in the forward direction, the term of the exponential function is sufficiently larger than -1, so 1=Io exp (9V/kT) ・”tl
), and a relationship of ■■in 1 is established between the forward voltage ■ and the current I. If we rewrite equation (1) to the 0th order shown in Fig. 2, we get V==kT/q [: in (1/lo)], T=3000K (, l!7℃) VC. kT/q
is 26 mV, υ, 1°C, the winning piece is about 03% (1/convex OO)
There is a temperature drift. FIG. 5 shows the characteristics of the voltage VF and the ambient temperature Ta of the silicon tie auto.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned points, and has the following objectives: 1) To provide a photoelectric switch that can positively compensate for the temperature drift of the circuit and has stable zero operation. The purpose is to

[Disclosure of the invention]

Embodiment FIGS. 4 to 6 show an example of an area reflection type optical heavy switch, in which a light beam (P?) is directed against an object to be detected (CX).
The light projecting means 11) for projecting light and the light projecting means +1) are arranged at a predetermined interval ΔL, and the light receiving optical system condenses the reflected light (R) of the light beam (P) by the light projecting means 11) and the light projecting means +1). +21
, a position detection means (4) disposed on the condensing surface of the light-receiving optical system (2) and outputting a position signal corresponding to the position of the condensed spot (S), and position '' is a detection means (4) It is equipped with a distance measurement control means (5) that determines whether the detected object (X) exists within a predetermined detection area (DE) based on the output and controls the output circuit (6), and a coating tool, and performs triangulation. The distance f'z to the object to be detected is determined by the method, and when there is a flash of the object to be detected within the detection area (DE), the output circuit (6) is activated to output the object detection code. It is something. Here, the light emitting means 11 that emits a light beam (P) consisting of pulse * dimming to the object to be detected (X) is connected to an oscillation circuit (lO) that generates a synchronization signal to set the light emitting timing. , a drive circuit (11), a light emitting element such as a light emitting diode or a laser diode, and a light beam (P
)? It is formed by a condenser lens, and a projection optical system consisting of 7 lenses. A predetermined interval Δ from the light projecting means (1)
The light receiving means (2) arranged parallel to each other with L are triangulated with respect to the light projecting means rtl and the object to be detected (x), and this light receiving means (2) is arranged parallel to the object to be detected ( X
) reflected light (R)'a- A light receiving optical system (3) consisting of a convex lens for condensing the light, and a light receiving optical system (3) arranged on the light converging surface of the light receiving optical system (3) to form a condensing spot (S). It is composed of a position detection means (4) that outputs a position signal corresponding to the position. This position detection means (4) includes a light receiving optical system (3)
It is formed by two light-receiving elements (20a) and (20b) disposed in the light incident plane of the light receiving element (20a) and (20b) arranged in series in the moving direction of the condensed spot (S). These light receiving elements (20a) (20b) include phototransistors, photodiodes, solar streetcars,
CDS etc. are used. Alternatively, a so-called PSDi may be used as the position detecting means (4). Distance measurement control means +51u, output current IA from light receiving elements (2oa) (2ob), light receiving circuit (21a) (21b) for amplifying and converting IBi signal voltage V to VB, operational amplifier (G3) and tie auto (1) The anti-fault increasing circuit (22a) (22b) consisting of 1) and the anti-fault increasing circuit (22
a) Logarithmic increase rf3 circuit (22b
) Output 1 n V B full subtraction circuit 123+,
Subtraction circuit output! Set with nVA/VB and detection area setting policy (VR))
Work level VS? Comparison and subtraction circuit cause) Output l n V
A ratio soft circuit (2
4I and the comparison circuit output t sumbly J (four-part detection) in synchronization with the light emission timing (synchronization signal output from the oscillation circuit (lO)) of the light emission element (light beam tP from the light source).
By doing this, the detected object (x) is located in the detection area (LI
E) Does it exist within? An example of a day number processing circuit that is designed to discriminate exactly, and a control signal for the output circuit (6) only when the day number is continuously output for a predetermined period or longer from the signal processing circuit Q0, or when it is not output? Integrating circuit (
26), which is formed by a relay for load control, a semiconductor switch element for load control, etc., or an error in the output circuit (6) when the power supply voltage at 1 is lower than a preset voltage. Delivery? This is a malfunction prevention circuit that prevents

Note that the light receiving circuits (21a) (21b) are inverted up (G
1) and non-inverted anj(Gg)r,
It includes all bandpass filter circuits that pass only the pulsed optical signal, cut the DC optical signal, or pass only a specific frequency. Further, the subtraction circuit 123) is a differential amplifier (G
4). (7) is the light receiving circuit (21a
) is a light amount control means consisting of a comparator (G6) that discriminates the relative softness of the output based on the reference voltage Vs1, and the reflected light (
Based on the light intensity level of R), does the detected object (D) exist within the Hagichi area (DE)? The object detection signal Vx'i is outputted, and malfunctions can be prevented even when skin detection@body (X and l are specular bodies). (8) is an operational amplifier (G7). and a logarithmic amplification circuit (80) consisting of a diode (D2) and an &I$ voltage generating means and a cosciparator (Cz).
This is a malfunction prevention means that prevents malfunctions due to noise and is composed of a soft ratio circuit (15ll) and an AND circuit (AND). Depending on whether the light receiving circuit (21b) is connected to the light receiving circuit (21b), the light receiving signal I! Whether n ■ is obtained or not? The object detection VX, vX' inputted to the outside of the number processing circuit through the OR circuit ((JR)k) is blocked by the AND circuit (AND).

(9) uses a logarithmic amplification circuit (9Q) consisting of an operational amplifier (G9) and a tie-auto (DA), and a logarithmic amplifier consisting of a reference voltage generating means and a comparator (G, 0). It is a margin display means formed by a circuit requirement and a margin display section (92), and $ electric ratio V is based on the malfunction prevention means (
When the base 'I$ voltage v8 of 8) is set slightly higher and the output 1d of the logarithmic amplification circuit (22b) is higher than the reference voltage V, the margin display section (92) indicates the logarithmic amplification circuit (22b). circuit(
22b) Output! , n vB level is within the normal operating range? Hereinafter, one of the works of the husband example will be explained in detail. Now, the detected object (X) is the seventh
As shown in figure (a), a reflective photoelectric switch (Y) 7>
) at distances pHla, lb, lc [a, b, c, n light-receiving elements (20
a) The position of the focused spot (S) with respect to (20b) is as shown in FIG. 20a)(
The ratio of the amount of light incident on 20b) will change,
The output currents I, , IB of the light receiving elements (20a) (20b) become position signals corresponding to the position of the focused spot (S).

In the distance measurement control means (5), the light receiving circuits (21a) (21b
), the voltage VA proportional to this output current IA, 1B,
Vb'i is formed, and the logarithmic amplification circuit (22a) (22b) increases the voltage of IJ by 1nVA, and fnVBk subtracts from the subtraction circuit to the light receiving element (
20a) Logarithm value of the ratio of the amount of light incident on (2ob) 1
nVA/VB will be output. This subtraction circuit crocodile j outputs 1nV a/V.

becomes a friend as the detected object (X) moves, and the subtraction circuit (c) outputs 1 n V A / V B for the distance %l from the reflective photoelectric switch (Y) to the 4N detected object (x) 1.
is as shown in FIG. Therefore, the previous work level (V
By appropriately setting B), accurate detection area (
DE) can be easily set, and the subtraction circuit (MU) output I! nV
When A/■B is below the operating level, the ratio soft circuit 124
1 output becomes H level (illi processing circuit 12
5+ i valve and the output circuit (6) is turned off. In this case, the distance measurement control means (5) controls the light receiving elements (20a) (20
1)) Output level ratio? When the level ratio is the preset previous level VS, the output circuit (6) is turned off, and detection is performed regardless of the level of the reflected light tR) from the detected object IX). Since the area (DE) is set, it is possible to prevent erroneous previous detection due to an object with a large light reflectance that exists behind the detection area (DE), and to adjust the light reflectance of the detected object (X). The detection area (DE) is set in z stages regardless of the detection area (DE), and is not affected by contamination of the optical system 0413+ for projecting and receiving light. Also, in the previous embodiment, the reference voltage generation means for the malfunction prevention means (8) and the margin display means (9)? Logarithmic amplification circuit to form (
81)) (9α) is equivalent to the logarithmic amplification circuit (22b) of the distance measurement control means (5), and these n logarithmic amplification circuits (22Is) (80) (90) The temperature drifts of are equal. Therefore, even if the temperature drift of the logarithmic amplifier circuit (22b) is large,
Similar temperature drift occurs in the logarithmic amplification circuits (80) (90') of the reference voltage generation means, so the surface input of the comparison circuit consisting of the J3 regulator (Gl) (Gl.) The relative value of the voltage level applied to the terminal does not change,
The malfunction prevention means (8) and the margin display means (9) operate stably, and the bells do not change due to temperature, resulting in stable operation. Magnitude, comparator (Ga
)(The input signal source impedances from the input terminal of Gl(1) are also equal,] comparator G,)(G1°)
It can be eliminated by the shadow 9 by Iasumi style. That is, when the impedances of the input signal sources are not equal (in the case of the conventional example), the input bias 'II
When the i current drifts with temperature, the amount of change in this offset voltage will be different, and the comparator (cys) Cax
.

) The operation level fluctuated, which was a negative effect.0 Note that when using NEC's μPC271Ck as the cossiparator (GS) (G), the input bias current is 50
nA, and the temperature drift I/i is about 40 nA between 0 and 80°C.

Embodiment 49 Figure 49 shows a photoelectric switch similar to the FJiJ example, in which the logarithmic amplification circuit forming the reference voltage generating means of the margin display means (9) is replaced with a malfunction prevention means ( 8) is formed using the logarithmic amplification circuit (8G) t-, and by appropriately setting the values of the resistors (Rs), the reference voltages V, , V can be set.

The relationship is set to a predetermined relationship. In the figure, (R3) to (R6) are resistors.

Now, in the malfunction prevention means (8), the logarithmic amplification circuit (22
Only when the light reception signal level outputted from b) is higher than the noise level to some extent and higher than the lowest discrimination level, the surface control means (5) and (7) output the object detection signals eVx, Vx'. By controlling the sound of the output circuit (6), external noise and internal noise are completely prevented from fA previous work, and the margin display means (9) uses a logarithmic amplification circuit (
When the received light signal level output from 22b) is greater than the malfunction prevention means (8) by a preset amount of margin, the remaining sleeve display group (92) is entirely removed to adjust the optical axis. It is designed to display that the amount of received light has decreased to some extent (approximately 20%) due to errors, lens dirt, etc., and that the malfunction prevention means (8) and margin display means (9) Operating level (i.e. reference voltage V8, V9
) is a very complicated process if you set them separately, but
In the dog embodiment 2, the operation level can be set in conjunction with the variable current source U) which is varied by the operation level setting volume, so the operation level setting work becomes easy.

Embodiment FIG. 10 further shows a pond dog embodiment, in which the light projecting means +
The reflected light (R) from the object to be detected of the diffused light emitted from the light receiving means (2) is received by the light receiving means (2). The circuit (21) converts it into a voltage signal, the logarithmic amplification circuit (2) logarithmically compresses it, and the comparison circuit (to) logarithmically amplifies it; the received light output VR output from 24 is set in advance. base #-voltage v
It compares and determines whether it is larger than sl and outputs the output circuit (6
) It is a diffuse reflection type photoelectric switch with sound control, and it is designed to determine whether the detected object (■) exists within the detection area (DE) based on the light intensity level of the seven reflected light beams. The reference voltage Vs# of the ratio soft circuit (to) is formed by a reference voltage generating means using a logarithmic amplification circuit φ0)k, and the detection area (DE) k is set by changing the variable current source U)k. It has become.

The operation of Medical Example 5 will be described below. This kind of diffused photoelectric switch has a reception output VR of reflected light @) at a distance l.
Taking advantage of the change in Fig. 11, the received light output ■
When R becomes larger than the reference voltage s' of the comparison circuit example, the output circuit (6) is fully operated, and the reference voltage s' is generally fixed. therefore,
Light t of the light beam (P) projected from the light projecting means fil'
The detection area (DE)'r is changed depending on whether the detection area (DE)'r is changed or the current-voltage conversion impedance of the light receiving circuit t21+ is changed. however,
In the former method, when the detection area (DE) T is set far away, the influence of ambient light increases and the S/N decreases.
In the latter case, when the conversion rate of the light receiving circuit υ is increased, the internal noise due to the volume that causes switching inheatance increases, resulting in a decrease in the S/N ratio. there were. In the convex case of the second embodiment, the detection area (DE
)', the above-mentioned problems do not occur. Furthermore, the husband example 1.
As in case 2, by forming the reference voltage generating means using a seven-pair amplification circuit, it is possible to correct the humidity drift of the logarithmic amplification circuit □□□.
The previous level of the output circuit (6), that is, the detection area (DE) does not fluctuate due to temperature changes, and a photoelectric switch with stable operation can be obtained.

〔Effect of the invention〕

As described above, the present invention includes a light receiving circuit that detects a change in the amount of light received by a temporarily detected object, a logarithmic amplification circuit that logarithmically amplifies the output of the light receiving circuit, and a method that compares and determines the magnitude of the output of the logarithmic amplification circuit with respect to a reference voltage. In a photoelectric switch equipped with a comparative soft circuit that controls output circuits, malfunction prevention means, margin display means, etc., the reference voltage? The reference voltage generating means is formed using a logarithmic amplification circuit equivalent to the above-mentioned logarithmic amplification circuit, and when the logarithm amplification circuit that increases the light receiving circuit output due to a fault has a temperature drift of 7C, a comparison is made. Since the reference voltage of the circuit also drifts with temperature, the temperature drift of the logarithmic amplifier circuit can be properly corrected and the operating level of the comparator circuit can be kept constant.
There is an advantage that it is possible to provide a photoelectric switch in which the operation of the output circuit, malfunction prevention means, margin display means, etc. controlled by the comparison circuit output is stable.

[Brief explanation of the drawing]

Fig. 1 is the circuit diagram of the main 61S of the conventional example, Fig. 2 and Fig. 5 are explanatory diagrams of the previous work of the same as above, Fig. 4 is a diagram showing the configuration of the embodiment of the present invention, and Fig. 5 is the main part of the same as above. Is the block circuit diagram, Figure 6, an example of the same main circuit as above? Figures 7 and 8 are explanatory diagrams of the same operation as above, and Figure 9 is a circuit diagram of the main part of the Ikenobu embodiment.
Fig. 10 is a circuit diagram of the main part of Ike's example, and Fig. 11 is a J-section which explains the operation of the same as above. 1211 (21a) (21b) are light receiving circuits,
)(22b) is a logarithmic amplification circuit, 124+18υIll
Compare the circuit,! 0)■)) is a logarithmic amplification circuit. (Figure 3 Figure 4

Claims (1)

[Claims] (1) A standard for generating the reference voltage in a photoelectric switch that is fully equipped with a photodetector circuit that detects changes in the amount of light received by the detected object and a comparison circuit that controls the logarithmic increase in the total logarithmic term of the output of the photodetector circuit. A photoelectric switch in which a voltage generating means is formed using a logarithmic amplification circuit equivalent to the above-mentioned logarithm amplification circuit.