JP2002131448A - Transmission optical sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To synchronize light emitting and light receiving without a connecting line for synchronization and reduce influence of disturbance light. SOLUTION: Synchronous circuits 6A, 7G that are composed of a light emitting means 6, light receiving means 7, crystal oscillating circuits 6A1, 7G1, and frequency dividers 6A2, 7G2 are placed, and the emitting means 6 and receiving means 7 are individually synchronized by each circuit 6A, 7G.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmissive optical sensor, and more particularly, to a transmissive optical sensor in which light emission and light reception are synchronized without providing a connection line for synchronization and the influence of disturbance light is reduced.

[0002]

2. Description of the Related Art Conventionally, light is received in synchronization with light emission.
Only when the synchronous light reception is interrupted, it is determined that the target object 25 is present, and the detection signal D is output, so that a malfunction such as the absence of the target object 25 even when external light such as sunlight 26 is received is prevented. FIGS. 5 and 6 show transmission optical sensors.

The transmission type optical sensor shown in FIG. 5 has a configuration in which a light emitting element 21 and a light receiving element 22 are connected to a control unit 20 and the light emitting element 21 is separated from the control unit 20 by a connection line 24.

With this configuration, when there is no object 25, the light from the light emitting element 21 is received by the light receiving element 22 as it is, and the control unit 20 determines that there is no object 25.

However, when there is an object 25, the light from the light emitting element 21 is blocked by the object 25.
The amount of light received by the light receiving element 22 changes, whereby the control unit 20 outputs the detection signal D from the output terminal 23 and determines that the object 25 is present.

Accordingly, the transmission type optical sensor shown in FIG. 5 is configured such that, even if the light receiving element 22 receives disturbance light such as sunlight 26, the synchronous light reception is interrupted by the object 25, Since the detection signal D is output based on the change in the amount of light received by the light receiving element 22 and it is determined that the object 25 is present, malfunction does not occur.

The transmission type optical sensor shown in FIG. 6 has a configuration in which the light emitting side and the light receiving side are connected by a connection line 48 dedicated to the synchronization signal 47.

With this configuration, the light-emitting side pulse oscillator 3
When the pulse signal oscillated from 5 is input via the input resistor 34 to the base of the transistor 33 having the bias resistor 36, the transistor 33 is turned on and the power supply 3
Current from the light emitting diode 3 via the braking resistor 31
2, the light emitting diode 32 emits light.

The light emitted from the light emitting diode 32 is received by a photodiode 40 on the light receiving side, and a light receiving signal 49 at that time is amplified by a differential amplifier 42 having a feedback resistor 41 and is output to a synchronous detector 43. And is detected in synchronization with the synchronization signal 47 input from the light emitting side.

That is, when there is no object 25, the synchronous detector 43 receives the received light signal 49 and the synchronous signal 47 at the same time and outputs the detected signal 50, so that the detected signal 50 continues to be output. In other words, when synchronous light reception continues, the transistor 45 is not turned on via the comparator 44, and the detection signal D is not output from the output terminal 46.

However, when there is an object 25, the synchronous light reception is cut off and the detection signal 50 is not output, the transistor 45 is turned on via the comparator 44, and the detection signal D is output from the output terminal 46. Is done.

Accordingly, even if the photodiode 40 receives disturbance light such as sunlight 26 when the synchronous light reception is interrupted by the object 25, the transmission type optical sensor of FIG. Since the detection signal 50 is not output and the detection signal D is output and it is determined that the target 25 is present, malfunction does not occur.

[0013]

[Problems to be solved by the invention]

However, the transmissive optical sensors shown in FIGS. 5 and 6 each have a light-emitting side and a light-receiving side connected by wire, and are provided with synchronization connection lines 24 (FIG. 5) and 48 (FIG. 5). 6) must be provided.

As a result, there are adverse effects such as an increase in the size of the device and troublesome wiring, which is not preferable.

An object of the present invention is to synchronize light emission and light reception without providing a connection line for synchronization, and to reduce the influence of disturbance light.

[0017]

According to the present invention, as shown in FIGS. 1 to 4, the light emitting means 6 and the light receiving means 7 include crystal oscillation circuits 6A1 and 7G1 and a frequency divider 6A.
Synchronous circuits 6A and 7G comprising 2, 7G2 are provided, and the light emitting means 6 and the light receiving means 7 synchronize light emission and light reception by the synchronous circuits 6A and 7G, respectively.

Therefore, according to the present invention, the light emitting means 6 (FIG. 1) is controlled by the synchronization circuit 6A, for example, to emit light at a light emitting period H.
= 250 ms, and emits a predetermined modulated light 9 (FIG. 2 (A)). In synchronization with this, the light receiving means 7 (FIG. 3)
The synchronization circuit 7G starts from the time point t2 at which the reception of the modulated light 9 having the light emission cycle of 250 ms ends (arrow (1) from FIG. 4B to FIG. 4C and the subsequent FIG. 4).
The arrow (2) from (c) to FIG. 4 (d)) (the arrow (3) from FIG. 4 (d) to FIG. 4 (c)) so as to end at time t9, for example, 1 ms from the light emission period 250 ms. Since the short light receiving period J of 249 ms can be set, the light emitting means 6 (FIG. 1) and the light receiving means 7 (FIG. 3) can be independently synchronized with each other. Therefore, a connection line for synchronization must be provided. In addition, light emission and light reception can be synchronized, and the influence of disturbance light can be reduced.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described by way of embodiments with reference to the accompanying drawings. FIG. 1 is a view showing a light emitting means 6 constituting the present invention, FIG. 2 is a view for explaining the operation of FIG. 1, FIG. 3 is a view showing a light receiving means 7 which constitutes the present invention, and FIG. is there.

The light emitting means 6 (FIG. 1) emits modulated light 9 having a predetermined period H (for example, 250 ms (FIG. 2A)).
The light receiving means 7 (FIG. 3) receives the light in synchronization with the modulated light 9 (FIG. 4A) and sets a light receiving cycle J (FIG. 4).
(C)) When the light reception is interrupted (for example, FIG.
(T3 to t4 in FIG. 4A) A detection signal D is output (FIG.
(T11 to t6 in (f)) It is determined that the object 8 (FIG. 3) is present.

Accordingly, a malfunction such as the disturbance light such as the sunlight 11 (FIG. 3) is not received, and the object 8 is present and is not detected.

In this case, the light emitting means 6 and the light receiving means 7 are provided with a synchronizing circuit 6 for synchronizing with each other, as described later.
A (FIG. 1) and 7G (FIG. 3). According to the present invention, light emission and light reception can be synchronized without providing a connection line for synchronization, and the influence of disturbance light can be reduced. it can.

The light emitting means 6 (FIG. 1) includes a synchronizing circuit 6A, a one-shot multivibrator 6H, a modulator 6B, and a light emitting section 6C.

The synchronization circuit 6A comprises a crystal oscillation circuit 6A1 and a frequency divider 6A2.
The synchronization signal is output to the one-shot multivibrator 6H, and the synchronization signal is driven.

In this case, the crystal oscillating circuit 6A1 is a Colpitts-type crystal oscillating circuit having capacitors 6A1D and 6A1E, and has a natural frequency of 32,768 kHz, for example.
It has a z crystal oscillator 6A1A and a linear amplifier including an inverter 6A1B and a resistor 6A1C.

[0026] When inputting pulse signals 32,768kHz oscillated from the crystal oscillation circuit 6A1 to the CP terminal of the next stage of the frequency divider 6A2, by which it is 13 stages division, from Q ₁₃ pin The above-mentioned cycle H is 250 m
The s synchronization signal is output.

The one-shot multivibrator 6H is
When a synchronizing signal is input from the synchronizing circuit 6A, the resistor 6H1 and the capacitor 6H
Time 250 predetermined by the time constant specified in 2
By hitting one shot for μs, the cycle becomes 250
A pulse signal having a pulse width of 250 μs in ms is output.

As a result, the light emission period H of the modulated light 9 emitted from the light emitting unit 6C (FIG. 2A) is 250 m.
s and a pulse width of 250 μs are respectively set.

The modulation section 6B modulates the pulse signal from the one-shot multivibrator 6H at a predetermined frequency f, and comprises an oscillation circuit 6B1 and a transistor 6B2 with a common emitter.

The base of the transistor 6B2 is grounded via a bias resistor 6B5 and a stabilizing resistor 6B4, and is connected to the one-shot multivibrator 6H via an input resistor 6B6.

The collector of the transistor 6B2 is connected to the output side of the oscillation circuit 6B1, and the input side of the oscillation circuit 6B1 is connected to the power supply 6B3.

According to this configuration, when a pulse signal from the one-shot multivibrator 6H is input to the base of the transistor 6B2 via the input resistor 6B6, the transistor 6B2 receives the pulse signal having a pulse width of 250 μm.
Turn on only for s.

As a result, a pulse wave having the natural frequency f is output from the oscillation circuit 6B1,
From the emitter of No.2, the time that it is on is 250μ
A modulated wave (corresponding to FIG. 2A) modulated by the frequency f by s is output and input to the next-stage light emitting unit 6C.

The light emitting section 6C is driven by the modulated wave output from the modulating section 6B, emits the modulated light 9 having a light emitting time of 250 μs (FIG. 2A) at a cycle of 250 ms, and emits a light emitting diode 6C1 and an emitter. Grounded transistor 6C2
Are connected in series.

The base of the transistor 6C2 is grounded via a bias resistor 6C5, and the input resistor 6C
It is connected to the modulation section 6B via C6.

The collector of the transistor 6C2 is connected to the cathode of the light emitting diode 6C1, and the anode of the light emitting diode 6C1 is connected to the power supply 6C4 via the braking resistor 6C3.

With this configuration, when the modulated wave from the modulator 6B is input to the base of the transistor 6C2 via the input resistor 6C6, the transistor 6C2 turns on.

As a result, the current from the power supply 6C4 flows through the braking resistor 6C3 as a light emission signal (FIG. 2A) to the light emitting diode 6C1, and the light emitting diode 6C1
Emits the modulated light 9 having a light emission time of 250 μs in proportion to the light emission signal (FIG. 2A) at a cycle of 250 ms.

On the other hand, the light receiving means 7 (FIG. 3) includes a D-type flip-flop 7A, a light receiving driving section 7B, a light receiving section 7C,
One-shot multivibrator 7D and output unit 7E
And a synchronization circuit 7G.

The D-type flip-flop 7A receives light from a light-receiving section 7C described later (for example, from t1 to t in FIG. 4A).
2) "0" of the output signal (FIG. 4 (b)) is input to the CP terminal, and at the rising time t2, an inverted signal of the signal held at the D terminal is output (see FIG. 4 (b)). Arrow (1) toward 4 (c)).

Then, this inverted signal is (FIG. 4C)
The signal is input to a frequency divider 7G2 included in a synchronous circuit 7G described later, and is reset (arrow (2) from FIG. 4C to FIG. 4D).

In this case, the synchronizing circuit 7G is constituted by a similar crystal oscillation circuit 7G1 (FIG. 3) so as to synchronize with the light emitting means 6 side (FIG. 1), and a frequency divider 7G2 is connected thereto. ing.

With this configuration, as described above, the synchronization circuit 7G outputs a synchronization signal (FIG. 4D) for setting the light receiving period J = 249 ms (FIG. 4C), and outputs the synchronization signal. Is input to and drives the D-type flip-flop 7A (arrow (3) from FIG. 4D to FIG. 4C).

The crystal oscillation circuit 7G1 includes a capacitor 7
This is a Colpitts-type crystal oscillation circuit provided with G1D and 7G1E, for example, a crystal resonator 7G1A having a natural frequency of 32 or 768 kHz, an inverter 7G1B and a resistor 7G1C.
Having a linear amplifier.

When the 32,768 kHz pulse signal oscillated from the crystal oscillation circuit 7G1 is input to the next-stage frequency divider 7G2, the synchronizing signal (FIG. 4D) is obtained.
Is output.

In this case, the frequency divider 7G2 (FIG. 3)
A frequency divider 7G2A and a second frequency divider 7G2B,
The two frequency dividers are connected by an inverter 7G2C as shown in the figure, and as described above, each time light is received, the frequency divider is reset and starts counting (for example, the arrow (1) at time t2 in FIG. 4 and the subsequent arrow ( 2)).

When the 32 or 768 kHz pulse signal oscillated from the crystal oscillating circuit 7G1 is input to the CP terminal, the first frequency divider 7G2A divides the pulse signal into six stages to obtain Q _6. A pulse signal having a cycle of approximately 1 ms is output from the terminal, and the pulse signal is inverted by the inverter 7G2C and input to the CP terminal of the second frequency divider 7G2B.

As a result, the second frequency divider 7G2B
By further 8 stages dividing the input pulse signal to the terminal, and outputs a synchronizing signal previously described from the Q ₈ terminals (FIG. 4 (d)).

This synchronizing signal is reset (for example, FIG.
(D) Time t2) The cycle H set by the light emitting means 6
= 249 which is 1 ms earlier than 250 ms (FIG. 2A)
In ms, the reset is released and the device starts up (Fig. 4
Time point t9 in (d)).

When the synchronization signal for setting the light receiving cycle is input to the R terminal (FIG. 3) of the D-type flip-flop 7A (FIG. 4D), the output inverted signal is reset (FIG. 4). The arrow (3) from (d) to FIG. 4 (c)) starts after the inverted signal is output (time t2 in FIG. 4 (c)) and ends after the elapse of 249 ms (time in FIG. 4 (c)). t9) The light receiving cycle J is set.

In this case, during the light receiving cycle J (FIG. 4)
(Time t2 to t9 in (c)), the light receiving drive unit 7B described later
(FIG. 3) is not activated, and therefore, the light receiving section 7C is in the off state and is inactive, but after the light receiving cycle J is completed (time t9 in FIG. 4C) via the light receiving driving section 7B (FIG. 3). 7C
Is turned on, and if there is no next light reception (time t3 to t4 in FIG. 4A), this on state continues, and if there is light reception (time t5 to t6 in FIG. 4A). ), The next light receiving cycle J starts from the time when the light reception is completed (time t6 in FIG. 4B) (arrow (7) from FIG. 4B to FIG. 4C), and the light receiving section is started. 7C is turned off again and pauses.

As described above, the light receiving cycle 249 ms set by the synchronization circuit 7G of the light receiving means 7 is as shown in FIG.
The light emission period 250 set by the synchronization circuit 6A of the light emission means 6
1 ms shorter than ms (FIG. 2A), thereby enabling light reception before light emission.

Further, since it is necessary to synchronize with the light emitting means 6 side (FIG. 1), as described above, the time from when the light receiving from the light emitting means 6 is completed (for example, at time t2 in FIG. The light receiving cycle 249 ms is started (see FIG. 4).
Arrow (1) from (b) to FIG. 4 (c)).

When the inverted signal from the D-type flip-flop 7A is input (FIG. 4C), the light receiving drive unit 7B, as described above, rises when it is reset (for example, FIG. By starting at time t9) of c), the light receiving section 7C is driven, that is, the power supply 7C2 is turned on, and as shown in FIG.
B1 and its bias resistor 7B2 and input resistor 7B3.

The light receiving section 7C receives only the modulated light 9 (FIG. 4 (a)) having a period of 250 ms sent from the light emitting means 6, converts the modulated light 9 into an electric signal, and receives a light receiving circuit 7C1 and its V _CC. It is composed of a power supply 7C2 connected to the terminal and a pull-up resistor 7C3 connected to the OUT terminal.

With this configuration, when the modulated light 9 from the light emitting means 6 enters the light receiving circuit 7C1, its V _CC terminal is
A light receiving signal having a predetermined voltage appears (t1 in FIG. 4A).
To t2)), the light receiving signal (FIG. 4
“0” which is an inverted signal of (a) is output (FIG. 4).
(T1 to t2 in (b)).

Thus, the light receiving means 7 (FIG. 3) transmits the modulated light 9 having a light emission period of 250 ms sent from the light emitting means 6.
Only light is received by the light receiving section 7C (FIG. 4).
(A)) As described above, an erroneous operation in which disturbance light such as sunlight 11 (FIG. 3) is not received, and the object 8 is not detected even when it is present is prevented.

The one-shot multivibrator 7D is
When the light receiving section 7C receives light (for example, t1 in FIG. 4A)
To t2) "0" of the output signal (FIG. 4B) is input to the B terminal, and at the rising time t2, the resistor 7D
By hitting one shot for a predetermined time of 300 ms based on the time constant defined by 1 and the capacitor 7D2 (arrow (4) from FIG. 4B to FIG. 4E), the pulse width longer than the period of 250 ms Is 300m
s pulse signal is output.

In this state, for 300 ms (FIG. 4E)
T2 to t11), when there is no next light reception (for example, t3 to t4 in FIG. 4A), the pulse signal from the one-shot multivibrator 7D is output at the time t (FIG. 4E).
The light falls at 11, the light reception is cut off, and the object 8 (FIG. 3)
When it is determined that there is, a detection signal D is output from an output unit 7E described later (arrow (6) from FIG. 4E to FIG. 4F).

When the one-shot multivibrator 7D receives the next light (at time t5 in FIG. 4A).
To t6), a pulse signal is output again (arrow (12) from FIG. 4B to FIG. 4E), and further light is received during the 300 ms (time t7 to t8 in FIG. 4A). Since the restart is performed before the pulse signal falls, the pulse signal is released (after time t6 in FIG. 4E), the detection signal D from the output unit 7E is not output, and it is determined that there is no target object 8. (After time t6 in FIG. 4 (f)).

The output unit 7E (FIG. 3) detects when the modulated light 9 having a light emission cycle of 250 ms sent from the light emission signal 7 is blocked by the object 8, and as described above, detects the light. The signal D is output (FIG. 4F), and a diode 7E1 is output.
An input resistor 7E2 and a common emitter transistor 7E3
It consists of.

With this configuration, the output unit 7E receives the pulse signal (FIG. 4E) from the one-shot multivibrator 7D at the end of the light reception (for example, the time t2 in FIG. 4B). The potential of the output terminal 7E2 becomes "0" and the detection signal D is not output (FIG. 4).
Arrow (5) from (e) to FIG. 4 (f)), object 8
Is not detected.

However, as described above, the duration of the pulse signal of the one-shot multivibrator 7D is 300 m.
If there is no next light reception during s (time t3 to t in FIG. 4A)
4) Since the pulse signal falls (time t11 in FIG. 4 (e)), the potential of the output terminal 7E2 of the output section 7E is not "0" and the detection signal D is output (FIG. 4 (e)).
4 (f) to the arrow (6)), the target object 8 is detected.

As described above, according to the present invention, the light emitting means 6 and the light receiving means 7 are provided with the synchronization circuits 6A and 7G, respectively, so that the light emitting means 6 and the light receiving means 7 can independently synchronize light emission and light reception. Therefore, it is no longer necessary to provide a connection line for synchronization as in the related art (FIGS. 5 and 6).

Further, according to the present invention, as described below,
The light receiving time T (for example, time t10 to t8 in FIG. 4C)
Shortening also has the effect of reducing power consumption.

That is, when the light receiving section 7C constituting the light receiving means 7 (FIG. 3) continuously receives light, for example, as shown in FIG.
When light reception ends at time t6 in (b), an inverted signal is output from the D-type flip-flop 7A (arrow (7) from FIG. 4 (b) to FIG. 4 (c)), and as described above, The light receiving cycle J = 249 ms starts, and the synchronization circuit 7
The frequency divider 7G2 constituting A is reset to output a synchronization signal (arrow (8) from FIG. 4C to FIG. 4D), and the reset of the synchronization signal is released after 249 ms has elapsed. Then, the inverted signal of the D-type flip-flop 7A is reset, and the light receiving period T is started at the same time when the light receiving period J = 249 ms ends (arrow (9) from FIG. 4D to FIG. 4C). At time t in FIG.
8, when the next light reception is completed, the D-type flip-flop 7A
, The light receiving time T ends (arrow (10) from FIG. 4B to FIG. 4C), and at the same time, the frequency divider 6A2 is reset (FIG. 4). The arrow (1) from (c) to FIG.
1)).

In this case, the light receiving time T is 250 ms-
249 ms = 1 ms (FIG. 4C), and the light receiving time T is set using a synchronization signal obtained by dividing the frequency of the pulse signal oscillated from the crystal oscillation circuit 7A1 having good time accuracy. Therefore, the light receiving time T can be shortened, for example, to 1 ms (FIG. 4C) described above with respect to the light emitting cycle of 250 ms, and the ratio of the light receiving time to the light emitting cycle is as small as 0.5 to 1%. This makes it possible to reduce power consumption by shortening the light receiving time.

[0068]

As described above, according to the present invention, the light-emitting means and the light-receiving means can independently synchronize with each other, so that light emission and light-receiving can be performed without providing a connection line for synchronization. Synchronization has the effect of reducing the influence of disturbance light, and further has the effect of reducing power consumption by shortening the light receiving time.

[0069]

[Brief description of the drawings]

FIG. 1 is a view showing a light emitting means 6 constituting the present invention.

FIG. 2 is an operation explanatory diagram of FIG. 1;

FIG. 3 is a diagram showing a light receiving means 7 constituting the present invention.

FIG. 4 is an operation explanatory diagram of FIG. 3;

FIG. 5 is an explanatory diagram of a configuration of a first related art.

FIG. 6 is a configuration explanatory view of a second conventional technique.

[Explanation of symbols]

 Reference Signs List 6 light emitting means 6A synchronous circuit 6B modulating section 6C light emitting section 6H one-shot multivibrator 7 light receiving means 7A synchronous circuit 7B light receiving driving section 7C light receiving section 7D one-shot multivibrator 7E output section 7G synchronous circuit 8 object 9 modulated light 11 sunlight

Claims (4)

[Claims] A transmission circuit characterized in that a synchronizing circuit comprising a crystal oscillation circuit and a frequency divider is provided in the light emitting means and the light receiving means, and each of the light emitting means and the light receiving means synchronizes light emission and light reception by each synchronous circuit. Type optical sensor. 2. The transmission type optical sensor according to claim 1, wherein the synchronization circuit of the light receiving means sets a light receiving cycle shorter than the light emission cycle set by the synchronization circuit of the light emitting means. 3. The transmission type optical sensor according to claim 2, wherein said light receiving cycle is started when light reception from said light emitting means is completed. 4. The transmission type optical sensor according to claim 2, wherein the light receiving time is shortened by bringing the light receiving cycle as close as possible to the light emitting cycle.