JPH0460800A - Light energy driving type detector - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a detection device that drives a detection section with optical energy and optically transmits a measurement signal, and particularly relates to a detection device that drives a detection section with optical energy and optically transmits a measurement signal. This invention relates to a light energy-driven detection device that has been improved so that it can be operated for a certain period of time regardless of variations in the lifespan of the device.

(Prior Art) In optical energy-driven detection devices such as those described above, a semiconductor laser is generally used as a light source.
A method is used in which this optical energy is transmitted to the detection unit using an optical fiber.

However, this method has the following problems. That is, the first problem is that the emission power of the semiconductor laser is 10
It is around mW, and the light energy that can actually reach the detection part is 1/10 to 1/3 of the emitted light power, and the output that can be stably extracted electrically is around 1/10 of that, and the power is less than a few hundred μW. Therefore, it is necessary to drive a detection circuit that also includes optical transmission. The second problem is that high-NA, large-diameter optical fibers and fibers that can be used for energy transmission, such as multi-component optical fibers and polymer-clad optical fibers, have large optical transmission losses of around 1θdB/km. , there is a large loss fluctuation over a transmission distance of 200 to 300 m, and a large margin in the emission power is borne by the semiconductor laser, making it difficult to ensure its lifetime.

Therefore, in order to solve the problem of causing the semiconductor laser to emit extra light regardless of the length of the transmission distance, as shown in "-", we have developed Even if the ratio of power (power), transmission distance, or other factors change, the light emission is controlled so that the power received and taken by the detection section is the minimum necessary value, and an attempt is made to eliminate excessive light emission. It is being done.

(Invention or Problem to be Solved) However, the lifespan of semiconductor lasers is subject to large variations due to chips and chips, and even if the lifespan of each semiconductor laser is maximized, the time to replace the semiconductor laser will differ depending on the device. Therefore, there were problems with its maintenance and reliability. Additionally, as mentioned above, there has been a strong desire to develop a light energy-driven detection device that can minimize the amount of optical power received by the detection section by controlling the amount of light emitted by the semiconductor laser. .

The present invention was proposed to eliminate the above-mentioned drawbacks, and its purpose is to control the light emission of a semiconductor laser so that the optical power received and taken by the detection section is the minimum necessary value. The object of the present invention is to provide a highly reliable optical energy-driven detection device that can be driven for a certain period of time regardless of variations due to the life of the laser.

[Configuration of the Invention (Means for Solving the Problems) The present invention transmits light from a semiconductor laser provided in a receiving section to a detecting section, drives a detecting circuit with this potential energy, and generates a second detecting circuit. In the optical energy-driven detection device configured to transmit the measurement signal obtained by the above to the receiving section 1 and further send it to an external device, the detecting section detects the amount of optical energy transmitted from the receiving section. A light energy amount detection means and a signal transmission means for transmitting the information to a receiving section are provided, and the receiving section includes a light emission amount control means for controlling the amount of light emitted from the semiconductor laser based on the information; The present invention is characterized by being provided with intermittent drive control means for calculating the remaining life of the detector, intermittently driving the detection device according to this remaining life, and controlling the interval of the intermittent driving.

(Function) In the optical energy-driven detection device of the present invention, information about the amount of optical energy received by the detection section is transmitted to the reception section, and the amount of light emitted from the semiconductor laser is controlled based on that information. Even if the proportion of optical power reaching the detection section changes, the power received by the detection section remains at the minimum necessary value. The light emission is controlled as follows. In addition, the forward current of the semiconductor laser is detected, and in this order @tF, the remaining life of the semiconductor laser is determined from the history by W, lL. If this remaining life is shorter than the predetermined driving period of the device, the semiconductor laser is Control is performed to switch to intermittent driving at intervals such that the semiconductor laser is driven until then, and the device can be driven for a certain period of time regardless of the life span of the semiconductor laser.

(Example) Hereinafter, an example of the present invention will be specifically described based on FIGS. 1 to 7.

(ID 1st Embodiment As shown in FIG. 1, the optical energy-driven detection device of this embodiment is composed of a receiving section A, a detecting section B, and an optical fiber C that optically couples the two. First,
The receiving unit A converts the photodiode 15 and the electrical signal output from the photodiode 15 into two signal components a,
a separation/demodulation circuit 16 that separates the electrical signal components into an appropriate signal;
7. Laser control drive circuit 12 as intermittent drive control means;
It is composed of a semiconductor laser 11, a photodiode 13 for automatic laser light intensity control, and a charging current amplification circuit]4.

On the other hand, the detection section B includes a photodiode 2], a transformer 2
2. A rectifier circuit 23, a voltage comparator 24 which is a means for detecting the amount of light energy received by the detection section, a sensor 25 that detects physical quantities such as temperature and pressure, a conversion processing section 26 that converts the detection signal, and the voltage It consists of a modulation circuit 27 that superimposes the output signal of the comparator 24 and the output signal of the conversion processing section 26, and a light source 28 driven by the output of the modulation circuit 27. Moreover, the optical fiber C includes an optical fiber 30 for optical energy transmission and an optical fiber 31 for signal transmission.
It consists of

The optical energy-driven detection device of this embodiment having such a configuration operates as described below.

That is, the semiconductor laser 11 disposed in the receiving section A keeps the sum of the output of the photodiode 13 for automatic light amount control and the output from the signal processing section 17, which is the light emitting amount control means, constant. The configuration is such that the forward current is controlled so that. Therefore, by changing the output of the signal processing section 17, the amount of light emitted from the semiconductor laser 11 can be changed. The semiconductor laser 11 is modulated with a pulse signal of several kilohertz and several tens of kilohertz, and the amplifier circuit 14 performs peak value control using a peak hold circuit.
Alternatively, average value control is performed using an integrating circuit. The optical signal from the semiconductor laser 11 frequency-modulated in this manner is transmitted to the photodiode 21 provided in the detection section B via the optical fiber 30 for transmitting optical energy.

On the other hand, in the detection section B, since the transmitted optical power is modulated by pulses, the optical/electric conversion signal output by the photodiode 21, which is the optical energy detection means, becomes an alternating current, and the output is converted by the transformer 22. It is boosted and used to drive the conversion processing section 26. Here, when the input optical power is insufficient, the boosted voltage becomes smaller than the reference voltage, and the output of the voltage comparator 24 is superimposed on the output of the conversion processing section 26 in the modulation circuit 27.

Conversely, if the input optical power is excessive, the obtained voltage will be higher than the reference voltage, and the output of the voltage comparator 24 will not be superimposed on the output of the conversion processing section 26.

The signal superimposition method in this modulation circuit 27 is such that the signal from the sensor 25 is converted into a frequency signal by voltage-frequency conversion by the conversion processing unit 26, and when there is an output from the voltage comparator 24, each pulse of this frequency signal is There is a method to convert from single pulse to double pulse. According to this method,
When the obtained optical power is sufficiently large, the sensor output becomes a single pulse frequency signal, and when the optical power decreases, the sensor output becomes a double pulse frequency signal. Note that the output signal of the modulation circuit 27 is converted into an optical pulse signal by the light source 28 and transmitted to the receiving section A via the signal transmission optical fiber 31.

Furthermore, in the receiving section A, a signal transmission optical fiber 3
The optical signal transmitted through 1 is input to the separation/demodulation circuit 16, where the output signal a of the voltage comparator 24 is separated from the sensor output signal S, and the presence or absence of the signal is determined by the signal processing section 17.
The output to the control drive circuit 12 is increased or decreased.

The overall flow of control is shown in the timing chart of FIG. First, as shown in FIG. 2(B), there is an output from the voltage comparator 24, and when this is superimposed on the sensor output signal and sent from the detection section B to the reception section A, the signal processing section 17 generates an optical signal. The power is judged to be low. Then, the signal processing unit 17 calculates the forward current of the semiconductor laser 11 as shown in FIG. 2(C).
This semiconductor laser 1 was gradually increased as shown in
As the forward current increases with respect to 1, the output voltage of the rectifier circuit 23 also increases as shown in FIG. 2(A). However, when the rectified output reaches the upper limit of the hysteresis of the voltage comparator 24, the output of the voltage comparator 24 disappears and is no longer superimposed on the sensor output, so the signal processing unit 17 reduces the forward current of the semiconductor laser 11. go. As a result, the optical power decreases, and when the voltage comparator 24 starts outputting again, the power of the semiconductor laser 11 is increased.

In this way, the amount of light emitted from the semiconductor laser 11 is controlled,
By transmitting the minimum optical power necessary for the sensor 25 to detect the physical quantity, it is possible to prevent the semiconductor laser 11 from emitting excessive light and shortening its lifespan.

By the way, keeping the power incident on the detection unit B at a substantially constant minimum necessary value means keeping the amount of light emitted from the semiconductor laser 11 substantially constant. However, as the semiconductor laser deteriorates, the DC current-light output characteristic curve changes sequentially from curve 1 to curve 2, curve 3, and curve 4 shown in Figure 3. In this case, it is necessary to increase the operating current in response to the progress of deterioration. Generally, the lifespan of a laser is determined by the operating current or the initial value■. For semiconductor lasers with a threshold current of 50 mA or less, it is often defined as around 1.5 times. In addition, the relationship between the energization time and the operating current in constant light output operation is as shown in Figure 4. The time T when the operating current reaches 1 is the lifespan, and the curve up to that point is approximately linearly approximated. I can do it. Therefore, in the control drive circuit 12, as shown in FIG. It can be predicted that T is the lifetime of the laser. By the way, semiconductor laser chips have large variations, and the lifespan varies greatly depending on the chip. It is very dangerous to predict the lifespan from the beginning.Therefore, there is no sure way to calculate the lifespan from the individual energization time vs. operating current curve. It is.

Therefore, the predicted lifespan T is limited to a certain fixed period T9.
．． (for example, the laser replacement period)
N<T<TM), the control drive circuit 12 is configured to switch the drive of the semiconductor laser 11 to intermittent drive. Incidentally, the interval of this intermittent drive can be calculated from the slope of the straight line connecting points A and B in FIG. By switching the semiconductor laser to intermittent driving in this way, it is possible to guarantee driving during a predetermined period when the semiconductor laser is desired to be used as a detection device.

As mentioned above, in this embodiment, even if the proportion of optical power reaching detection section B changes due to transmission distance or other factors, the optical power received and received at detection section B is kept at the minimum necessary value. In addition, it is possible to provide an extremely reliable device that can guarantee the operation of the detection device for a certain predetermined period despite variations in laser chips.

■Second Embodiment The optical energy-driven detection device of this embodiment also uses a receiving section D, a detecting section E, and a light beam for optically coupling the receiving section and the detecting section E, as shown in FIG. It is composed of fiber F.

First, the receiving section includes a photodiode 54, a resistor 55,
Optical/electric conversion section 56, pulse shaping section 57, signal conversion section 5
8, a peak hold section 59, a comparison section 60, a current control section 61 as a light emission amount control means, a laser drive section 62 as an intermittent drive control means, and a semiconductor laser 41.

The photodiode 54 and the optical/electrical conversion section 56 receive the optical pulse signal transmitted from the detection section E via the signal transmission optical fiber 53, convert it into an electrical signal, and output it. Further, the pulse shaping section 57 pulse-shapes the electrical signal from the optical/electrical converting section 56. Furthermore, the signal conversion section 58 inversely converts the signal from the pulse shaping section 57 into measurement data, and outputs it as an analog signal such as voltage or current. In addition, the peak hold section 5
9 holds the peak value of the electrical signal from the optical/electrical converter 56. Furthermore, the comparison section 60 compares the peak value obtained by the peak hold section 59 with the reference voltage Vr.
This is a comparison. In addition, the current control section 61
The drive current of the laser drive unit 62 is controlled so that the peak value becomes equal to the reference voltage Vr based on the comparison result of the comparison unit 60, and the history of the drive current is memorized. The remaining life of the laser is calculated, and when the remaining life is shorter than a certain predetermined period, the laser driving section 62 is switched to intermittent driving. Furthermore, the laser drive section 62 drives the semiconductor laser 41 in accordance with the control by the current control section 61, and the semiconductor laser 41 emits laser light and uses the light as driving power for the detection section E. It supplies the fiber 42.

On the other hand, the detection section E includes a solar cell 43, a power supply stabilization section 44,
Sensor 45, amplification section 46, data conversion section 47, transistor 48, light emitting diode 49, voltage dividing resistor 50.5
1 and a capacitor 52. The solar cell 43 receives light supplied from the semiconductor laser 41 via the optical fiber 42 for transmitting light energy, and converts the light energy into electrical energy. In addition, the power supply stabilizing section 44 stabilizes the voltage of the power from the solar cell 43 and outputs power to the sensor 45, the amplifying section 46, and the data converting section 47.
It drives a detection circuit consisting of: Furthermore, the sensor 45 detects measurement signals such as pressure and temperature, converts them into electrical signals, and outputs them. Further, the amplifying section 46 is
The electric signal from the sensor 45 is kept constant and amplified to a high degree.

Furthermore, the data conversion section 47 performs frequency conversion, digital conversion, etc. on the signal from the amplification section 46, and outputs it to the transistor 48 as a pulse signal. Further, the light emitting diode 49 is directly driven by the output voltage from the solar cell 43, and uses a current flowing when the transistor 48 is turned on to provide a light pulse signal corresponding to the measurement signal to the signal transmission optical fiber 53.

Further, the optical fiber F includes an optical fiber 42 for transmitting optical energy and an optical fiber 53 for transmitting a signal. The optical fiber 42 for transmitting optical energy transmits the light from the semiconductor laser 41 to the detection section E side. On the other hand, the signal transmission optical fiber 53 transmits the optical pulse signal from the light emitting diode 49 to the receiving section.

Here, the oscillation light from the semiconductor laser 41 which is the light source is
The spread angle in the direction perpendicular to the junction is largely 30 degrees or more due to diffraction, and in order to easily obtain a high coupling rate with the optical fiber 42 for transmitting optical energy, it is desirable to use an optical fiber with a high NA. For example, multi-component glass fiber with NAO of 33-0.5, NAO.

4 or so is suitable for devices with a transmission distance of several hundred meters or less. Furthermore, unlike the optical energy transmission optical fiber 42, the signal transmission optical fiber 53 does not have any characteristic requirements, and there is no problem as long as the loss is less than that of the optical energy transmission optical fiber 42.

The optical energy-driven detection device of this embodiment having such a configuration operates as described below.

That is, in FIG. 6, the light from the semiconductor laser 41 in the receiving section is supplied to the detecting section E as driving power through the optical fiber 42 for transmitting optical energy. On the other hand, in the detection section E, the light supplied from the semiconductor laser 41 via the optical fiber 42 for transmitting optical energy is received by the solar cell 43, and the optical energy is converted into electrical energy. Then, in the power supply stabilizing section 44, the voltage of the power converted by the solar cell 43 is stabilized, and is supplied to a detection circuit consisting of a sensor 45, an amplifying section 46, and a data converting section 47 to drive these. Then, measurement signals such as pressure and temperature are detected by the sensor 45 and converted into electrical signals, which are amplified to a certain level by the amplifier 46 and then sent to the data converter 47.
Frequency conversion, digital conversion, etc. are performed at , and the result is given to the transistor 48 as a pulse signal. As a result, in the final stage of the detection section E, the transistor 48 is ONL, and current flows through the light emitting diode 49 that is directly driven by the output voltage of the solar cell 43, so that the optical pulse signal corresponding to the measurement signal is transmitted to the signal transmission light source. The signal is transmitted to the receiving section through the fiber 53.

On the other hand, in the receiving section, the optical pulse signal transmitted from the detecting section E via the signal transmission optical fiber 53 is received by the photodiode 54 and the optical/electrical conversion section 56 and converted into an electrical signal. The electrical signal from the optical/electrical converter 56 is subjected to pulse shaping in a pulse shaping unit 57, and then reverse data conversion is performed in a signal converting unit 58 to be converted into analog signals such as voltage and current for external devices. is output to.

Further, the peak value of the electrical signal from the optical/electrical converter 56 is held by a peak hold unit 59, and the held value is compared with a reference voltage Vr by a comparison unit 60. and,
Based on this comparison signal, the current control section 61 controls the current of the laser drive section 62 so that the hold value becomes equal to the reference voltage Vr, and the amount of light emitted from the semiconductor laser 41 is controlled, thereby controlling the detection section. The peak value of the optical pulse signal from E is maintained at a certain level. That is, the peak value P peak of the optical pulse signal from the detection section E is
8 is turned on, the output voltage of the solar cell 43 is set to Vl.
l, the resistance value of the resistor 50 is R1,1, the light emitting diode 49
Letting the forward electric current of 2 be (■), it is given by Ppeakoc(Vtq - Vl), /R1°. peak value of optical pulse signal Yj)'pe
Keeping ak constant means keeping the output voltage of the solar cell 43 constant, and the relationship between the output voltage of the solar cell 43, the incident power and C, and the increase in voltage as shown in FIG. Conclusion) By keeping the output voltage of the solar cell 43 constant, the power incident on the solar cell 43 can be kept constant. As described above, the detection unit E
It would be a good idea to measure the incident power required for this, determine the output voltage corresponding to it from the characteristics shown in FIG. 7, and set the reference voltage Vr in the receiving section so as to have that value.

As described above, the amount of light emitted by the semiconductor laser can be kept at the minimum amount necessary for driving the sensor, so the amount of light emitted by the semiconductor laser 1. - It is possible to prevent shortening of lifespan due to excessive light emission. 7. In order to drive a semiconductor device with large chip variations for a predetermined period, the current controller 61 calculates the semiconductor device based on the energization time-operating current curve, as in the first embodiment.
- Calculate the lifespan of the laser 7 and, if the predicted lifespan is shorter than a certain predetermined period, switch the laser drive section 62 to intermittent drive.2 As mentioned above, in this embodiment, Even if the proportion of the optical power reaching the detection section E varies depending on the transmission distance and other factors, the optical power received at the detection section E is the minimum necessary value, and for a given period. This makes it possible to provide an extremely reliable device that can guarantee the operation of the detection device despite the fluctuations of the single-nozer chip.

[Effects of the Invention] As described above, according to the present invention, information about the amount of optical energy received by the detection section is transmitted to the reception section, and the amount of light emitted from the semiconductor laser is controlled based on the information. Even if the proportion of optical power reaching the detector changes due to transmission distance or other factors, the light emission is controlled so that the optical power received and taken by the detector is the minimum necessary value. It is possible to provide a highly reliable optical energy-driven detection device that can guarantee drive of the detection device for a predetermined period despite variations.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the optical energy-driven detection device according to the present invention, FIGS. 2(A) to (C) are timing charts showing the flow of control in the first embodiment, and FIG. is a diagram showing the relationship between the deterioration of a semiconductor laser and the current-light output characteristic curve, FIGS. 4 and 5 are diagrams showing the relationship between the energization time and the operating current in constant light output operation, and FIG. FIG. 7, a block diagram showing the second embodiment, is a diagram for explaining its operation. A... Receiving section, B... Detecting section, C... Optical fiber, D... Receiving section, E... Detecting section, F... Optical fiber 11... Semiconductor laser, 12...・Control drive circuit,
13... Photodiode, 14... Charge current amplification circuit, 15... Photodiode, 16... Separation demodulation circuit, 17... Signal processing section, 21... Photodiode, 22... Transformer , 23... rectifier circuit, 24...
- Voltage comparator, 25... Sensor, 26... Conversion processing unit, 27... Modulation circuit, 28... Light source, 30...
Optical fiber for light energy transmission, 31... Optical fiber for signal transmission, 41... Semiconductor laser, 42... Optical fiber for light energy transmission 7-i/<43... Solar cell, 4
4... Power supply stabilization section, 45... Sensor, 46...
Amplification section, 47... Data conversion section, 48... Transistor, 49... Light emitting diode, 50... Resistor, 5
DESCRIPTION OF SYMBOLS 1... Resistor, 52... Capacitor, 53... Optical fiber for signal transmission, 54... Photodiode, 55
...Resistor, 56... Optical/electric conversion section, 57... Pulse shaping section, 58... Signal conversion section, 59... Peak hold section, 60... Comparison section, 61... Current control unit, 62...Laser drive unit. Gravity In 1 Electricity Figure 1A Electricity Time Diagram

Claims (1)

[Claims] Transmitting light from a semiconductor laser provided in the receiving section to the detecting section, driving a detection circuit with this light energy,
In a light energy-driven detection device configured to transmit a measurement signal obtained by this detection circuit to the receiving section and further to an external device, the detecting section has an amount of optical energy transmitted from the receiving section. A light energy amount detection means for detecting the amount of light energy and a signal transmission means for transmitting the information to a receiving section are provided, and on the other hand, the receiving section includes a light emission amount control means for controlling the light emission amount of the semiconductor laser based on the information. and an intermittent drive control means for calculating the remaining life of the semiconductor laser, intermittently driving the detection device according to this remaining life, and controlling the interval of the intermittent driving. Type detection device.