JP2001094140A - Transmission type optical sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission type optical sensor having less power consumption by allowing operation at an appropriate light-emission intensity. SOLUTION: In this transmission type optical sensor a detecting part 6 and an electron mirror part 7 are provided, the detecting part 6 emits a modulation beam 3 at a prescribed current value I, and informs the electron mirror part 7 of the light-emission intensity which is determined with the current value I by its modulation frequency (f). The detecting part 6 receives only a modulation beam 4 of the same current value I as is transmitted from the electron mirror part 7, and based on the presence of received light, changes the modulation frequency (f) and the current value I for adjusting light-emission intensity.

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 that operates at an appropriate light emission intensity to reduce current consumption.

[0002]

2. Description of the Related Art Conventionally, there is a transmission type optical sensor as an optical sensor for detecting the presence or absence of an object.

[0003] The transmission type optical sensor has, for example, as shown in FIG.

[0004] With this configuration, the detecting unit 10 can detect the predetermined light 4
When “0” is intermittently emitted at predetermined intervals and sent to the electronic mirror unit 20, the electronic mirror unit 20 returns exactly the same light 50 as the light 40 with the timing shifted, for example.

Accordingly, when the detection unit 10 receives the light 50 from the electronic mirror unit 20, it determines that there is no object 30, and when it does not receive the light 50, it determines that there is the object 30. .

[0006]

[Problems to be solved by the invention]

However, in the transmission type optical sensor of the electronic mirror type in which the detection unit 10 and the electronic mirror unit 20 are opposed to each other as shown in FIG. 6, since the detection unit 10 and the electronic mirror unit 20 both emit and receive light. Each has a light emitting element and a lens system.

Therefore, if the light emission intensity becomes insufficient due to aging of the light emitting element or contamination of the lens system, the transmission type optical sensor (FIG. 6) will not correctly detect the object 30 and will cause a malfunction.

Therefore, in the conventional transmission type optical sensor (FIG. 6), malfunction is prevented by increasing the light emission intensity from the beginning to the end of the operation.

However, when the light emission intensity is increased, the drive current of the light emitting element is increased, and the current consumption as a whole is accordingly increased, resulting in a disadvantage that the life of the transmission type optical sensor is shortened.

An object of the present invention is to provide a transmission type optical sensor which operates with an appropriate light emission intensity to reduce current consumption.

[0012]

In order to solve the above-mentioned problems, the present invention comprises a detecting section 6 and an electronic mirror section 7 as shown in FIGS. Value I
And the electronic mirror 7 is notified of the intensity of the light determined by the current value I based on the modulation frequency f, and receives only the modulated light 4 of the same current value I sent from the electronic mirror 7. The light emission intensity is adjusted by changing the modulation frequency f and the current value I depending on the presence or absence of light reception.

According to the configuration of the present invention, it is possible to adjust the light emission intensity to such an extent that the presence or absence of the object 2 (FIG. 1) can be accurately determined (FIG. 4B), thereby suppressing the current consumption. By operating at an appropriate emission intensity, a transmission optical sensor with reduced current consumption is provided.

[0014]

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 an overall view showing an embodiment of the present invention. The illustrated transmission type optical sensor 1 has a detection unit 6 and an electronic mirror unit 7.

The detecting section 6 and the electronic mirror section 7 are installed to face each other, and both have the same frequency f (FIG. 2A) and the same current value I.
Light emission and light reception are performed for the modulated light controlled in (FIG. 2B).

The detection unit 6 includes a control unit 6 for controlling the whole.
H, and a pulse oscillating unit 6A controlled by the control unit 6H
, A modulator 6B, a light emitter 6C, a one-shot multivibrator 6D, a light receiver driver 6E, and a light receiver 6F.
And an output unit 6G.

The control unit 6H has terminals A, B, and C. The terminal A is connected to the oscillation circuit 6B1 of the modulation unit 6B, the terminal B is connected to the constant current circuit 6C3 of the light emitting unit 6C, and the terminal C is connected to the output unit 6G. Each is connected to the output terminal 6G2.

With this configuration, the control unit 6H detects the presence or absence of light reception through the terminal C by feeding back the detection signal D (FIG. 5E) from the output terminal 6G2, and determines whether the object 2 exists. (FIG. 2 (C)), and the terminal A,
The frequency f of the oscillation circuit 6B1 via B (FIG. 2A)
And the current value I (FIG. 2B) of the constant current circuit 6C3.

Thus, according to the present invention, the light emission intensity is adjusted to such an extent that the presence or absence of the object 2 (FIG. 1) can be accurately determined, the consumption current is suppressed, and the operation is performed with an appropriate light emission intensity. Current consumption can be reduced.

In this case, the frequency f for the above-mentioned modulation is (FIG. 2A), and the detection unit 6 has the current value I (FIG. 1) (FIG. 2).
(B)) This is an identification signal for informing the electronic mirror unit 7 of the prescribed light emission intensity, and therefore, the frequency f and the current value I are paired.

For example, if the signals output from the terminals A and B of the control unit 6H are "00" (FIG. 2A and FIG. 2B), the frequency f is 50 kHz, the current value I is 10 mA,
In the case of "01", the frequency f is 100 kHz and the current value I
Are determined as a pair in advance, such as 20 mA.

Therefore, the detection unit 6 outputs the modulated light 3 defined in advance by the frequency f and the current value I (see FIG. 5).
(A)), for example, light emission time 1 ms, interval time 100 ms
At the frequency f as described above.
Is notified to the electronic mirror unit 7 through the
Only the same modulated light 4 (FIG. 5 (C)) sent from is received.

As described above, the detecting unit 6 and the electronic mirror unit 7
Performs light emission and reception of the same modulated light 3 and 4 because the sunlight 5
This is also to prevent disturbance light such as that shown in FIG. 1 from being received and to prevent a malfunction that the target object 2 is not detected even if it is present.

The pulse oscillating unit 6A includes an operational amplifier 6A1
1, a power supply 6A2 and voltage dividing resistors 6A3 and 6A4, a resistor 6A5 connected to the positive-phase input terminal, and a capacitor 6A6 and a resistor 6A7 connected to the negative-phase input terminal. ), Repetition period 1
A pulse signal of 00 ms is oscillated, and the pulse signal is input to the modulator 6B and the one-shot multivibrator 6D to drive them.

The modulating section 6B modulates the pulse signal from the pulse oscillating section 6A (FIG. 1) at a frequency f (FIG. 2A) designated by the control section 6H, and oscillates the oscillation circuit 6B1 and the emitter ground. Of the transistor 6B2.

The base of the transistor 6B2 is grounded via a bias resistor 6B5 and a stabilizing resistor 6B4, and the pulse oscillator 6 is connected via an input resistor 6B6.
A is connected.

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.

With this configuration, when a pulse signal from the pulse oscillating unit 6A (FIG. 1) is input to the base of the transistor 6B2 via the input resistor 6B6, the transistor 6B2 receives a pulse of the pulse signal (FIG. 1). It is turned on for a width of 1 ms.

As a result, a pulse wave of the designated frequency f (FIG. 2A) is output from the oscillation circuit 6B1,
From the emitter of the transistor 6B2, a modulated wave (corresponding to FIG. 5A) modulated at the frequency f for 1 ms while the transistor 6B2 is on 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, has a magnitude of the current value I designated by the control section 6H (FIG. 2B), and has a light emitting time of 1 ms (FIG. 2B). FIG. 5A shows a configuration in which the modulated light 3 is emitted at an interval of 100 ms, and a constant current circuit 6C3, a light emitting diode 6C1, and a transistor 6C2 with a common emitter 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 side of the light emitting diode 6C1, and the anode side of the light emitting diode 6C1 is connected to the constant current circuit 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 is reduced by the specified current value I of the constant current circuit 6C3 (FIG. 2).
(B)), the light-emitting signal (FIG. 5A) flows to the light-emitting diode 6C1, and the light-emitting diode 6C1 has a light-emitting time of 1 ms in proportion to the light-emitting signal (FIG. 5A) and the current is Modulated light 3 of value I (FIG. 2B) is 100 m
Intermittent light emission occurs at s intervals.

The one-shot multivibrator 6D is
When a pulse signal (FIG. 5) is input from the pulse oscillating unit 6A, a light receiving time 1 ms predetermined by a time constant defined by a resistor 6D1 and a capacitor 6D2 (FIG. 5), the light-receiving unit 6F is driven via the light-receiving drive unit 6E, and light is received (FIG. 5A).
The timing of (C) is shifted.

Thus, even if the modulated light 3 radiated from the light emitting section 6C (FIG. 1) is reflected by the object 2, it is reflected by the light receiving section 6C.
Even if the light enters F, the light receiving section 6F has not been driven yet, so it does not receive light, and an erroneous determination that the object 2 is not present despite being present is prevented.

The one-shot multivibrator 6
D is a signal that determines the light receiving time 1 ms (FIG. 5B).
D-type flip-flop 6G constituting an output section 6G by using the inverted signal of FIG.
1 to the CP terminal.

Thus, the D-type flip-flop 6G1
Can hold data at its D terminal (for example, an arrow from FIG. 5D to FIG. 5E).

The light-receiving drive section 6E comprises a transistor 6E1 having a common emitter, a bias resistor 6E2 and an input resistor 6E3.

With this configuration, the timing at which a signal (FIG. 5B) determining the light receiving time 1 ms from the one-shot multivibrator 6D is input to the G terminal of the light receiving circuit 6F1 described later is determined by the operating time of the transistor 6E1. The light receiving unit 6F is driven slightly later by only delaying the light receiving unit 6F.

That is, the one-shot multivibrator 6
The one-shot timing of D (for example, t3 in FIG. 5B) is more than the actual light-receiving timing of the light receiving unit 6F (for example, FIG.
Delay t4) of (C).

As a result, at the falling time t5 of the one-shot (FIG. 5B), in other words, at the rising time of the clock pulse of the D-type flip-flop 6G1 (FIG. 1), the D-type flip-flop 6G1 receives its D signal. The output signal “0” of the light receiving circuit 6F1 input to the terminal is securely held (arrows from FIG. 5D to FIG. 5E),
By stabilizing the operation, the range t1 to
t5 (FIG. 5 (E)) was made clear so that the object 2 (FIG. 1) could be clearly detected.

The light receiving section 6F receives only the same modulated light 4 sent from the electronic mirror section 7 and converts it into an electric signal, and receives a light receiving circuit 6F1 and a power supply 6F2 connected to its V _CC terminal. And pull-up resistor 6F connected to the OUT terminal
3.

With this configuration, when the modulated light 4 from the electron mirror unit 7 enters the light receiving circuit 6F1, its V _CC terminal is
As described above, a light receiving signal having a predetermined voltage appears whose actual light receiving time (t4 in FIG. 5C) is later than the one-shot time (t3 in FIG. 5B) of the one-shot multivibrator 6D. (T4 to t2 in FIG. 5C)).

From the OUT terminal of the light receiving circuit 6F1, "0" which is an inverted signal of the light receiving signal (FIG. 5C) is output (t4 to t2 in FIG. 5D).

The output unit 6G detects when the modulated light 4 sent from the electronic mirror unit 7 is interrupted by the object 2 (FIG. 1) and is no longer received, and outputs a detection signal D (FIG. 5).
(E)) Output.

The output section 6G is constituted by a D-type flip-flop 6G1.

With this configuration, the D-type flip-flop 6
G1 is an output signal from the light receiving unit 6F in the preceding stage (FIG. 5).
(D)) When the signal is input to the D terminal, at the falling point of the one-shot (FIG. 5B) of the one-shot multivibrator 6D, that is, at the rising point of the clock pulse (FIG. 1) input to the CP terminal. (For example, FIG. 5 (B)
6 (E), the light receiving portion 6F
5D is held at the D terminal (arrows from FIG. 5D to FIG. 5E)
).

Then, D of the D-type flip-flop 6G1
When the output signal “1” from the light receiving unit 6F is held at the terminal (for example, an arrow from FIG. 5D to FIG. 5E), the detection signal D (FIG. 5) is output from the output terminal 6G2.
(E)) is output and the modulated light 4 from the electronic mirror unit 7 is blocked by the target 2 (FIG. 1) and is no longer received (for example, time t1 in FIG. 5C). The object 2 is detected.

In this case, the input signal to the terminal C (FIG. 1) of the control section 6H is "1" (FIG. 2 (C)), and as described above, the detection section 6 (FIG. 1) Since the modulated light 4 from the mirror unit 7 is not received, it may be determined that the target object 2 exists.

However, it is actually unknown whether the detection unit 6 does not receive light due to the object 2 or not due to the contamination of the lens system but the object 2.

Therefore, in the present invention, the frequency f of the oscillation circuit 6B1 is controlled via the terminals A and B of the control section 6H (FIG. 1).
And the current value I of the constant current circuit 6C3 (FIG. 2 (A) and FIG. 2 (B)), as shown in FIG. 4 (A), starting from 10 mA at 50 kHz and 200 kHz.
It gradually increases up to 40 mA in z.

If the detecting unit 6 does not receive the modulated light 4 from the electronic mirror unit 7 (FIG. 4A) even if the light emission intensity reaches the upper limit, it is determined that the object 2 is present and the light is emitted. By fixing the intensity to the upper limit, the object 2 is accurately detected.

That is, in step 101 in FIG. 3, "00" is applied to the terminals A and B of the control section 6H (FIG. 2A, FIG.
(B))), and in step 102, when the input to the terminal C of the control unit 6H is “1” (FIG. 2C) (YES), in the next step 104, “0” is similarly set.
"1" is output. If the C input is "1" in step 105, "10" is output in step 107. If the C input is "1" in step 108, "110" is output in step 110. 11 "is output.

As described above, the output from the terminals A and B of the control unit 6H is "11" (FIG. 2A), and the emission intensity of 40 mA at 200 kHz (FIG. 4A) is the highest upper limit. Also, only when the C input is “1” in step 111 of FIG. 3, in step 113, the process returns to step 110 with the object 2 present, and the light emission intensity is fixed to this upper limit.

On the other hand, the D-type flip-flop 6G1
When the output signal “0” from the light receiving unit 6F is held at the D terminal of FIG. 1 (for example, an arrow from FIG. 5D to FIG. 5E), the output terminal 6G2 (FIG. Since the detection signal D (FIG. 5E) is not output from 1) and the modulated light 4 is received from the electronic mirror unit 7 (for example, t4 to t2 and t9 to t10 in FIG. 5C). , The object 2 is not detected.

In this case, the input signal to the terminal C (FIG. 1) of the control unit 6H is "0" (FIG. 2C), and as described above, the detection unit 6 (FIG. 1) Since the modulated light 4 from the mirror unit 7 is received, it is determined that the object 2 is not present.

In this case, the frequency f output from the terminals A and B of the control unit 6H at that time (FIG. 2)
(A)) and the emission intensity based on the current value I (FIG. 2 (B)) are fixed.

For example, in step 101 of FIG.
“00” is applied to terminals A and B of the control unit 6H (FIG. 2A, FIG.
(B))), and if the C input is “0” in step 102 (NO), it is determined that there is light reception, and step 10
In step 3, it is determined that there is no object 2, and
The emission intensity is fixed based on "00", that is, the frequency f is 50 kHz and the current value I is 10 mA.

Similarly, in step 101,
Although "00" was output, in step 102, the C input is "1" (YES), the flow proceeds to step 104, where "01" is output, and in step 105, the C input is now "0". If it does (NO), step 10
In step 6, it is determined that there is no object 2 and step 101
Returning to "01", that is, when the frequency f is 100 kHz
To fix the emission intensity based on the current value I of 20 mA.

However, with only such a uniform control operation, for example, as shown in FIG. 4A, when it is determined that there is no object 2 and no light is received and the light emission intensity is fixed to the upper limit, When the object 2 suddenly disappears, the luminous intensity may not be fixed properly.

Therefore, in the present invention, as shown in FIG. 4B, the detection unit 6 determines that there is an object 2 without receiving light, and the emission intensity at a frequency f of 200 kHz and a current value I of 40 mA is an upper limit. In the state described above, when the object 2 suddenly disappears and receives light, the emission intensity is temporarily reduced to the lower limit (50 kHz).
z to 10 mA).

However, the reason why the light emission intensity was lowered to the lower limit was too low. Therefore, light was not received due to contamination of the lens system. When the light emission intensity was increased by one step (20 mA at 100 kHz), the light was received again. It is determined that there is no object 2, and the emission intensity is fixed.

That is, in step 110 of FIG. 3, "11" is applied to the terminals A and B of the control section 6H (FIG. 2A, FIG.
(B))) and the emission intensity is fixed to the upper limit, and in step 111, the terminal C of the control unit 6H is
When the input is set to "0" (FIG. 2 (C)) (NO), it is determined that there is no light reception, and in step 112, it is determined that there is no target object 2, in step 114, unless the operation is terminated (NO). , The process proceeds to step 101, where "00"
To reduce the emission intensity to the lower limit.

However, in step 102, the C input becomes "1" (FIG. 2C) (YES), and no light is received.
When "1" is output, in step 105, the C input becomes "0" (FIG. 2C) (NO), and it is determined that there is no light reception. In step 106, it is determined that the object 2 is not present, and the process returns to step 104. Emission intensity at that time ("0
1 "= 20 mA at 100 kHz).

The electronic mirror unit 7 (FIG. 1) includes a frequency / voltage conversion unit 7G, an A / D conversion unit 7H, a one-shot multivibrator 7A, a light receiving drive unit 7B, and a light receiving unit 7C.
, One-shot multivibrator 7D, and modulation section 7
E and a light emitting unit 7F.

The configuration of the one-shot multivibrator 7A and the like is the same as that of the one-shot multivibrator 6D of the detection unit 6.

The frequency / voltage conversion section 7G inputs the amplified modulated light 3 output via the fout terminal of the light receiving circuit 7C1 constituting the light receiving section 7C and converts it into a voltage.

The A / D converter 7H performs A / D conversion on the voltage output from the frequency / voltage converter 7G to obtain a 2-bit digital output, thereby obtaining an output of the oscillation circuit 7E1 constituting the modulator 7E. The frequency f and the current value I of the constant current circuit 7F3 constituting the light emitting section 7F are designated, respectively.

In this case, the oscillating circuit 7E1 decodes the two oscillating circuits into 2-bit inputs and switches them by a relay, and the constant current circuit 6C3 decodes the four resistors into 2-bit inputs. It may be switched by a relay.

One-shot multivibrator 7 at the preceding stage
A indicates that when the light receiving unit 7C first receives light (t in FIG. 5A).
12 to t6) At time t6 when the output signal (FIG. 5B) rises to "0", the resistor 7A1 and the capacitor 7
An inverted signal having a pulse width of 95 ms predetermined by the time constant defined by A2 is output (from FIG. 5B to FIG. 5B).
Arrow toward (c)).

As a result, the inverted signal (FIG. 5)
At the end time point t7 of (c)), the light receiving time T is started, and the signal representing the light receiving time T (FIG. 5C) is delayed by the operation time of the transistor 7B1 of the light receiving driving unit 7B to the light receiving unit 7C. The modulated light 3 is input to the G terminal of the light receiving circuit 7C1 and receives the modulated light 3 from the detecting unit 6 with a margin (FIG. 5A).

The modulated light 3 from the detector 6 is
When the light receiving circuit 7C receives light for the second time during the light receiving time T (FIG. 5C) (t11 to t in FIG. 5A).
8)), "0" of the output signal from the OUT terminal is input to the one-shot multivibrator 7A (t11 to t8 in FIG. 5B) (FIG. 1).

Therefore, at the end time t8 of the second light reception by the light receiving circuit 7C (FIG. 5 (a)), OUT
When the output signal from the terminal becomes "1" (FIG. 5B),
The inverted signal is output again from the one-shot multivibrator 7A (arrows from FIG. 5B to FIG. 5C), thereby ending the light receiving time T.

In this case, the modulated light 3 received by the light receiving section 7C of the electronic mirror section 7 (FIG. 1) is emitted by the light emitting section 6C of the detecting section 6 (FIG. 5A) (FIG. A)), the control unit 6H has a frequency f designated (FIG. 1) and a current value I (FIG. 2 (A)) (FIG. 2 (B)), the light emission time is 1 ms, and the interval time is 100 ms. is there.

Accordingly, the pulse width 9 of the inverted signal from the one-shot multivibrator 7A set based on the modulated light 3 (FIG. 5A) received by the light receiving section 7C.
The sum of 5 ms (FIG. 5C) and the light receiving time T = 5 ms is just 100 ms.

Then, the total time 95 ms + 5 ms =
The start time t6 of 100 ms (FIG. 5 (c)) and the end time t8 are the first light reception by the light receiving unit 7C (t in FIG. 5 (a)).
12 to t6)), the rising time t6 of the output signal “0” (FIG. 5B) and the second light reception (t11 in FIG. 5A).
To t8) coincide with the rising time t8 of the output signal “0” (FIG. 5B).

For this reason, the one-shot multivibrator 7D at the subsequent stage (FIG. 1) receives the output signal from the light receiving section 6F (FIG. 5B), and at the rising points t6 and t8 of "0", Resistor 7D1 and capacitor 7D2
1 m emission time predetermined by the time constant specified in
If you hit one shot for only s (from FIG.
(D), the modulated light 3 (FIG. 5) of the detecting unit 6 via the modulating unit 7E (FIG. 1) and the light emitting unit 7F.
5 (A) and FIG. 5 (a)), the modulated light 3 having the same frequency f and current value I with the timing shifted by 1 ms (FIG. 5 (d)).
It can emit light.

That is, the one-shot multivibrator 7
When a pulse signal indicating a light emission time of 1 ms from D (FIG. 1) is input to the base of the transistor 7E2 constituting the modulation section 7E via the input resistor 7E6, the transistor 7E
2 turns on only for the pulse width 1 ms of the pulse signal (FIG. 1).

As a result, the oscillation circuit 7E1 outputs a pulse wave of the specified frequency f (same as the oscillation circuit 6B1 of the detection section 6 (FIG. 2A)), and the emitter of the transistor 7B2 outputs 1m when it is on
A modulated wave (corresponding to FIG. 5D) modulated by the frequency f by s is output and input to the next-stage light emitting unit 7F.

Accordingly, the light emitting section 7F is driven by the modulated wave output from the modulating section 7E, and has a current value I (FIG. 2B) and a light emission time of 1 ms (FIG. 5D). The modulated light 4 is emitted at intervals of 100 ms.

The modulated light 4 (FIG. 5D) is sent to the detector 6, and as described above (FIG. 5C), the detector 6 emits the modulated light 3 (FIG. 5 (C)). A) Same modulation frequency f as in
According to the present invention, the modulation frequency f, (FIG. 2 (A)) and current value are determined based on the presence or absence of the received light (FIG. 2 (C)). The emission intensity is adjusted by changing I (FIG. 2B) via the control unit 6H (FIG. 1) (FIGS. 3 and 4).

[0084]

As described above, according to the present invention, the detecting section emits modulated light having a predetermined current value, notifies the electronic mirror section of the light emission intensity determined by the current value according to the modulation frequency, and sends the modulated light to the electronic mirror section. Only the modulated light of the same current value sent is received,
By adjusting the light emission intensity by changing the modulation frequency and current value according to the presence or absence of the light reception, it is possible to reduce the current consumption by adjusting the light emission intensity to the extent that the presence or absence of an object can be accurately determined. By operating at an appropriate light emission intensity, there is an effect that a transmission type optical sensor with reduced current consumption is provided.

[0085]

[Brief description of the drawings]

FIG. 1 is an overall view showing an embodiment of the present invention.

FIG. 2 is a diagram showing input / output signals of a control unit 6H constituting the present invention.

FIG. 3 is a flowchart for explaining the operation of the present invention.

FIG. 4 is a diagram showing a mode of adjusting light emission intensity according to the present invention.

FIG. 5 is a waveform chart of each part of the present invention.

FIG. 6 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 transmission optical sensor 2 object 3, 4 modulated light 5 sunlight 6 detection unit 6A pulse oscillation unit 6B modulation unit 6C light emission unit 6D one-shot multivibrator 6E light reception drive unit 6F light reception unit 6G output unit 6H control unit 7 electronic mirror Unit 7A one-shot multivibrator 7B light-receiving drive unit 7C light-receiving unit 7D one-shot multivibrator 7E modulation unit 7F light-emitting unit 7G frequency / voltage conversion unit 7H A / D conversion unit

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Ryuichi Aida 3-3-1 Marunouchi, Chiyoda-ku, Tokyo Nihon Signal Co., Ltd. F-term (reference) 2G065 AA04 AB02 AB04 AB23 AB28 BA01 BC09 BC14 BC21 CA29 DA15 5F089 BB04 BB20 CA16 FA03 FA05 FA06 FA10

Claims (4)

[Claims] 1. A detection unit comprising: a detection unit; and an electronic mirror unit. The detection unit emits a modulated light having a predetermined current value, notifies the electronic mirror unit of a light emission intensity determined by the modulation frequency, and transmits the light from the electronic mirror unit. Receiving only the modulated light of the same current value
A transmissive optical sensor, wherein the light emission intensity is adjusted by changing a modulation frequency and a current value depending on the presence or absence of the light reception. 2. The transmission type optical sensor according to claim 1, wherein the detection unit increases the light emission intensity and fixes the light emission intensity when it is determined that there is no object after receiving the light. 3. The transmission-type optical sensor according to claim 1, wherein the detection unit determines that there is an object when the light emission intensity is raised to the upper limit, and fixes the light emission intensity to the upper limit. 4. The detection unit determines that there is no object when receiving light with the emission intensity fixed at the upper limit, and reduces the emission intensity to the lower limit. If the light is received at that time, it determines that there is no object. 2. The transmission type optical sensor according to claim 1, wherein the light emission intensity is fixed to the lower limit, and when no light is received, the light emission intensity is increased to increase the light emission intensity and to fix the light emission intensity when it is determined that there is no object.