JP2021131250A - Light detection system and discharge probability calculating method - Google Patents

Abstract

To calculate regular and irregular discharges' probabilities of an optical sensor.SOLUTION: A light detection system includes: an optical sensor 1: a discharge probability calculating portion 202 that calculates discharge probabilities for a first state in which light from an additional light source 101 having known light quantity is incident on the optical sensor 1, a second state in which the additional light source 101's turning-on/turning-off state is the same as the first state and a pulse width of a drive pulse voltage applied to the optical sensor 1 is different from the first state, a third state in which the additional light source 101's turning-on/turning-off state is different from the first and second states with the same pulse width as the first state, and a fourth state in which the additional light source 101's turning-on/turning-off state is the same as the third state with the same pulse width as the second state; and a discharge probability calculating portion 203 that calculates regular and irregular discharges' probabilities of the optical sensor 1 on the basis of sensitivity parameters stored in a sensitivity parameter storing portion 19, the discharge probabilities in the first to fourth states, and the pulse widths in the first to fourth states.SELECTED DRAWING: Figure 1

Description

The present invention relates to a photodetection system that detects light such as a flame.

A photocell type ultraviolet sensor may be used as an optical sensor that detects the presence or absence of a flame based on the ultraviolet rays emitted from the light of a flame in a combustion furnace or the like. It has been observed that a non-regular discharge phenomenon (suspicious discharge) occurs due to a noise component other than the discharge due to the photoelectric effect in the discharge of the phototube type ultraviolet sensor.

Patent Document 1 proposes a flame detection system capable of controlling the pulse width of a drive pulse applied to an optical sensor, obtaining the amount of received discharge from a calculation, and determining the life of the flame sensor from the amount of light. However, the actual discharge of the optical sensor includes a non-regular discharge due to noise, which is collectively called a failure, and even if there is no light due to the flame, the discharge may occur and an erroneous detection may occur. In order to eliminate such false detection of discharge, it is necessary to consider a method for measuring the discharge probability in consideration of the noise component.

Further, in the flame detection system disclosed in Patent Document 2, a method of obtaining a light receiving amount in consideration of the discharge probability of a noise component other than the normal discharge has been proposed, and it is possible to accurately detect the presence or absence of a flame. There is. However, in the flame detection system disclosed in Patent Document 2, it is necessary that the discharge probability of the noise component is known.

Further, in the failure detection device disclosed in Patent Document 3, it is proposed to detect a failure due to self-discharge of the optical sensor by providing a shutter mechanism for blocking electromagnetic waves incident on the optical sensor. However, in the failure detection device disclosed in Patent Document 3, there is no discriminating method for distinguishing between regular discharge and non-regular discharge due to a change in measurement sensitivity due to the life of the optical sensor, and there is a possibility that failure detection may be erroneous. was there.
The above problems occur not only in the flame detection system but also in the light detection system using the optical sensor.

JP-A-2018-84422 JP-A-2018-84423 Japanese Unexamined Patent Publication No. 05-012581

The present invention has been made to solve the above problems, and is generated depending on the discharge probability of a normal discharge excluding noise components other than the discharge due to the photoelectric effect of the optical sensor and the amount of light received by the optical sensor. An object of the present invention is to provide an optical detection system and a discharge probability calculation method capable of calculating the discharge probability of a non-normal discharge due to a noise component.

The light detection system of the present invention has an optical sensor configured to detect light emitted from a first light source, and the generated light is incident on the optical sensor together with light from the first light source. A drive pulse voltage is periodically applied to the installed second light source having a known amount of light, a light source control unit configured to control the lighting / extinguishing of the second light source, and the electrodes of the light sensor. An applied voltage generator configured to detect the discharge current of the optical sensor, a current detector configured to detect the discharge current of the optical sensor, and a discharge current of the optical sensor based on the discharge current detected by the current detector. The discharge determination unit configured to detect, the first state in which the second light source is turned on or off, and the state in which the second light source is turned on / off are the same as those in the first state, and The second state in which the pulse width of the drive pulse voltage is different from the first state and the lighting / extinguishing state of the second light source are different from those in the first and second states, and the drive pulse voltage The third state in which the pulse width is the same as the first state and the lighting / extinguishing state of the second light source are the same as in the third state, and the pulse width of the drive pulse voltage is the second state. For each of the fourth states, which are the same as the states, discharge is performed based on the number of times the drive pulse voltage is applied by the applied voltage generator and the number of discharges detected by the discharge determination unit during the application of the drive pulse voltage. A first discharge probability calculation unit configured to calculate the probability, as known sensitivity parameters of the optical sensor, a reference pulse width of the drive pulse voltage, a reference light receiving amount of the optical sensor, and the first , A storage unit configured to store in advance the difference in the amount of light received by the optical sensor between the second state and the third and fourth states, a sensitivity parameter stored in the storage unit, and The discharge probability calculated by the first discharge probability calculation unit in the first, second, third, and fourth states and the first, second, third, and fourth states. Based on the pulse width of the drive pulse voltage, the discharge probability of a normal discharge when the pulse width of the drive pulse voltage is the reference pulse width and the light reception amount of the optical sensor is the reference light reception amount, and the drive pulse. To calculate the discharge probability of non-regular discharge due to noise components other than the discharge due to the photoelectric effect of the optical sensor, which is generated independently of the pulse width of the voltage and depends on the amount of light received by the optical sensor. It is characterized by including a second discharge probability calculation unit configured in the above.

Further, in one configuration example of the optical detection system of the present invention, the second discharge probability calculation unit has a reference pulse width T ₀ of the drive pulse voltage, a reference light receiving amount Q _{0 of the} optical sensor, and the first and first discharge probabilities. wherein the second state the third, fourth differential Q ₁ -Q ₂ of the light receiving amount of the light sensor in the state and the discharge probability calculated by the first discharge probability calculation unit to the first state ¹ ₁ P, the discharge probability calculated by the first discharge probability calculation unit in the second state ¹ ₂ P, calculated by the first discharge probability calculation unit in the third state. Discharge probability ² ₁ ^{P, discharge probability 2} ₂ P calculated by the first discharge probability calculation unit in the fourth state, pulse width of the drive pulse voltage in the first and third states. Based on T _{1 , the pulse width T 2} of the drive pulse voltage in the second and fourth states, the discharge probability P _{aA of} the normal discharge and the discharge probability P _bA of the non-normal discharge are calculated. It is characterized by that.

Further, the light detection system of the present invention includes an optical sensor configured to detect the light emitted from the first light source, and the generated light is incident on the optical sensor together with the light from the first light source. A second light source having a known amount of light, a light source control unit configured to control the on / off of the second light source, and a drive pulse voltage periodically applied to the electrodes of the light sensor. Based on the applied voltage generation unit configured to apply to, the current detection unit configured to detect the discharge current of the optical sensor, and the discharge current detected by this current detection unit, the optical sensor The discharge determination unit configured to detect the discharge, the first state in which the second light source is turned on or off, and the state in which the second light source is turned on / off are the same as the first state. In addition, the second state in which the pulse width of the drive pulse voltage is different from the first state and the lighting / extinguishing state of the second light source are different from the first and second states, and the drive pulse The third state in which the voltage pulse width is the same as the first state and the lighting / extinguishing state of the second light source are the same as in the third state, and the pulse width of the drive pulse voltage is the first state. The fourth state, which is the same as the second state, and the lighting / extinguishing state of the second light source are the same as those of the first and second states, and the pulse width of the drive pulse voltage is the first and third states. The fifth state, which is the same as either the second or fourth state, or different from the first, second, third, and fourth states, and the lighting / extinguishing state of the second light source. Is the same as the third and fourth states, and the pulse width of the drive pulse voltage is the same as the fifth state. For each of the sixth states, the number of times the drive pulse voltage is applied by the applied voltage generator. A first discharge probability calculation unit configured to calculate the discharge probability based on the number of discharges detected by the discharge determination unit during the application of the drive pulse voltage, and known optical sensors. As sensitivity parameters, the reference pulse width of the drive pulse voltage, the reference light receiving amount of the optical sensor, and the light in the first, second, and fifth states and the third, fourth, and sixth states. A storage unit configured to store the difference in the amount of light received by the sensor in advance, a sensitivity parameter stored in the storage unit, and the first, second, third, fourth, fifth, and sixth The discharge probability calculated by the first discharge probability calculation unit in the state of, and the pulse of the drive pulse voltage in the first, second, third, fourth, fifth, and sixth states. Based on width and It occurs independently of the discharge probability of normal discharge when the pulse width of the drive pulse voltage is the reference pulse width and the light reception amount of the optical sensor is the reference light reception amount, and the pulse width of the drive pulse voltage. A second discharge probability calculation unit configured to calculate the discharge probability of a non-regular discharge due to a noise component other than the discharge due to the photoelectric effect of the optical sensor, which is generated depending on the amount of light received by the optical sensor. It is characterized by having.

Further, in one configuration example of the optical detection system of the present invention, the second discharge probability calculation unit has a reference pulse width T ₀ of the drive pulse voltage, a reference light receiving amount Q _{0 of the} optical sensor, and the first and first discharge probabilities. 2, wherein a fifth state third, fourth, differential Q ₁ -Q ₂ received light amount of the light sensor in a sixth state, wherein the first discharge probability calculation unit to the first state Discharge probability ¹ ₁ ^{P calculated by, Discharge probability 1} ₂ P calculated by the first discharge probability calculation unit in the second state, and the first discharge probability in the third state. The discharge probability ² ₁ ^{P calculated by the calculation unit, the discharge probability 2} ₂ P calculated by the first discharge probability calculation unit in the fourth state, and the first in the fifth state. The discharge probability ^{1 P calculated by the discharge probability calculation unit, the discharge probability 2} P calculated by the first discharge probability calculation unit in the sixth state, and the discharge probability 2 P in the first and third states. The pulse width T _{1 of the drive pulse voltage, the pulse width T 2} of the drive pulse voltage in the second and fourth states, and the pulse width T of the drive pulse voltage in the fifth and sixth states. Based on this, the discharge probability P _{aA of} the normal discharge and the discharge probability P _bA of the non-regular discharge are calculated.

Further, in the discharge probability calculation method of the light detection system of the present invention, the light from the second light source having a known amount of light is incident on the light sensor that detects the light emitted from the first light source, or the second light source is described. In the first state in which the light source is turned off, the first step of periodically applying a drive pulse voltage to the electrodes of the optical sensor and the discharge current of the optical sensor in the first state are detected. The second step of detecting the discharge of the optical sensor based on the discharge current in the first state, the number of times the drive pulse voltage is applied by the first step, and the number of times the drive pulse voltage is applied. A fourth step of calculating the discharge probability in the first state based on the number of discharges detected in the third step while applying the drive pulse voltage, and lighting / lighting of the second light source. When the extinguishing state is the same as the first state and the pulse width of the drive pulse voltage is different from the first state in the second state, the drive pulse voltage is periodically applied to the electrodes of the optical sensor. The discharge of the optical sensor is performed based on the fifth step of detecting the discharge current of the optical sensor in the second state, and the discharge current of the optical sensor in the second state. The second step is based on the number of times the drive pulse voltage is applied by the seventh step to be detected, the number of times the drive pulse voltage is applied by the fifth step, and the number of discharges detected in the seventh step while the drive pulse voltage is being applied. The eighth step of calculating the discharge probability in the state and the lighting / extinguishing state of the second light source are different from those of the first and second states, and the pulse width of the driving pulse voltage is the first. A ninth step of periodically applying a drive pulse voltage to the electrodes of the optical sensor in the same third state as in the third state, and a third of detecting the discharge current of the optical sensor in the third state. The ten steps, the eleventh step of detecting the discharge of the optical sensor based on the discharge current in the third state, the number of times the drive pulse voltage is applied by the ninth step, and the driving thereof. A twelfth step of calculating the discharge probability in the third state based on the number of discharges detected in the eleventh step while applying the pulse voltage, and turning on / off the second light source. When the state is the same as the third state and the pulse width of the drive pulse voltage is the same fourth state as the second state, the drive pulse voltage is periodically applied to the electrodes of the optical sensor. The thirteen steps and the first to detect the discharge current of the optical sensor in the fourth state. The fourth step, the fifteenth step of detecting the discharge of the optical sensor based on the discharge current in the fourth state, the number of times the drive pulse voltage is applied by the thirteenth step, and the driving thereof. The sixteenth step of calculating the discharge probability in the fourth state based on the number of discharges detected in the fifteenth step while applying the pulse voltage, and as known sensitivity parameters of the optical sensor, The reference pulse width of the drive pulse voltage, the reference light receiving amount of the optical sensor, and the difference in the light receiving amount of the optical sensor between the first and second states and the third and fourth states are stored in advance. The sensitivity parameters stored in the storage unit, the discharge probabilities calculated in the fourth, eighth, twelfth, and sixteenth steps, and the first, second, third, and third storage units are referred to. Based on the pulse width of the drive pulse voltage in the fourth state, the normal discharge when the pulse width of the drive pulse voltage is the reference pulse width and the light reception amount of the optical sensor is the reference light reception amount. Non-regular discharge due to noise components other than discharge due to the photoelectric effect of the optical sensor, which occurs independently of the discharge probability and the pulse width of the drive pulse voltage and depends on the amount of light received by the optical sensor. It is characterized by including the 17th step of calculating the discharge probability.

Further, in the discharge probability calculation method of the light detection system of the present invention, the light from the second light source having a known amount of light is incident on the light sensor that detects the light emitted from the first light source, or the second light source is described. In the first state in which the light source is turned off, the first step of periodically applying a drive pulse voltage to the electrodes of the optical sensor and the discharge current of the optical sensor in the first state are detected. The second step of detecting the discharge of the optical sensor based on the discharge current in the first state, the number of times the drive pulse voltage is applied by the first step, and the number of times the drive pulse voltage is applied. A fourth step of calculating the discharge probability in the first state based on the number of discharges detected in the third step while applying the drive pulse voltage, and lighting / lighting of the second light source. When the extinguishing state is the same as the first state and the pulse width of the drive pulse voltage is different from the first state in the second state, the drive pulse voltage is periodically applied to the electrodes of the optical sensor. The discharge of the optical sensor is performed based on the fifth step of detecting the discharge current of the optical sensor in the second state, and the discharge current of the optical sensor in the second state. The second step is based on the number of times the drive pulse voltage is applied by the seventh step to be detected, the number of times the drive pulse voltage is applied by the fifth step, and the number of discharges detected in the seventh step while the drive pulse voltage is being applied. The eighth step of calculating the discharge probability in the state and the lighting / extinguishing state of the second light source are different from those of the first and second states, and the pulse width of the driving pulse voltage is the first. A ninth step of periodically applying a drive pulse voltage to the electrodes of the optical sensor in the same third state as in the third state, and a third of detecting the discharge current of the optical sensor in the third state. The ten steps, the eleventh step of detecting the discharge of the optical sensor based on the discharge current in the third state, the number of times the drive pulse voltage is applied by the ninth step, and the driving thereof. A twelfth step of calculating the discharge probability in the third state based on the number of discharges detected in the eleventh step while applying the pulse voltage, and turning on / off the second light source. When the state is the same as the third state and the pulse width of the drive pulse voltage is the same fourth state as the second state, the drive pulse voltage is periodically applied to the electrodes of the optical sensor. The thirteen steps and the first to detect the discharge current of the optical sensor in the fourth state. The fourth step, the fifteenth step of detecting the discharge of the optical sensor based on the discharge current in the fourth state, the number of times the drive pulse voltage is applied by the thirteenth step, and the driving thereof. The sixteenth step of calculating the discharge probability in the fourth state based on the number of discharges detected in the fifteenth step while applying the pulse voltage, and turning on / off the second light source. Whether the state is the same as the first and second states and the pulse width of the drive pulse voltage is the same as either the first or third state or the second or fourth state, the first, The 17th step of periodically applying the drive pulse voltage to the electrodes of the optical sensor in the fifth state different from the second, third, and fourth states, and the light in the fifth state. The 18th step of detecting the discharge current of the sensor, the 19th step of detecting the discharge of the optical sensor based on the discharge current in the fifth state, and the drive pulse according to the 17th step. The twentieth step of calculating the discharge probability in the fifth state based on the number of times the voltage is applied and the number of times of discharge detected in the nineteenth step during the application of the drive pulse voltage, and the twelfth step. The electrode of the optical sensor when the lighting / extinguishing state of the light source 2 is the same as the third and fourth states and the pulse width of the driving pulse voltage is the same as the fifth state and the sixth state. The 21st step of periodically applying the drive pulse voltage to the device, the 22nd step of detecting the discharge current of the optical sensor in the 6th state, and the discharge current in the 6th state. The 23rd step of detecting the discharge of the optical sensor based on the above, the number of times the drive pulse voltage is applied by the 21st step, and the discharge detected in the 23rd step during the application of the drive pulse voltage. The 24th step of calculating the discharge probability in the sixth state based on the number of times, the reference pulse width of the drive pulse voltage and the reference light reception of the optical sensor as known sensitivity parameters of the optical sensor. Referencing a storage unit that previously stores the amount and the difference in the amount of light received by the optical sensor between the first, second, and fifth states and the third, fourth, and sixth states, and this storage unit. The sensitivity parameters stored in, the discharge probabilities calculated in the 4th, 8th, 12th, 16th, 20th, and 24th steps, and the 1st, 2nd, 3rd, 4th, and 24th steps. The current of the drive pulse voltage is based on the pulse width of the drive pulse voltage in the fifth and sixth states. When the loose width is the reference pulse width and the light reception amount of the optical sensor is the reference light reception amount, the discharge probability of the normal discharge and the light reception of the optical sensor are generated independently of the pulse width of the drive pulse voltage. It is characterized by including a 25th step of calculating the discharge probability of a non-normal discharge due to a noise component other than the discharge due to the photoelectric effect of the optical sensor, which is generated depending on the amount.

According to the present invention, in addition to the first light source to be detected, a second light source having a known amount of light and a light source control unit are provided, and further, an applied voltage generation unit, a current detection unit, a discharge determination unit, and a first unit are provided. By providing a discharge probability calculation unit, a storage unit, and a second discharge probability calculation unit, the discharge probability of a normal discharge excluding noise components other than the discharge due to the photoelectric effect of the optical sensor and the pulse width of the drive pulse voltage can be obtained. It is possible to calculate the discharge probability of a non-regular discharge due to a noise component, which occurs independently and depends on the amount of light received by the optical sensor. As a result, in the present invention, it is possible to realize the life determination of the optical sensor based on the discharge probabilities of these regular discharges and the discharge probabilities of non-regular discharges.

FIG. 1 is a block diagram showing a configuration of a photodetection system according to an embodiment of the present invention. FIG. 2 is a waveform diagram showing a drive pulse applied to the optical sensor and a detection voltage detected by the current detection circuit in the embodiment of the present invention. FIG. 3 is a flowchart illustrating the operation of the photodetection system according to the embodiment of the present invention. FIG. 4 is a flowchart illustrating the operation of the photodetection system according to the embodiment of the present invention. FIG. 5 is a flowchart illustrating another operation of the photodetection system according to the embodiment of the present invention. FIG. 6 is a flowchart illustrating another operation of the photodetection system according to the embodiment of the present invention. FIG. 7 is a block diagram showing a configuration example of a computer that realizes the photodetection system according to the embodiment of the present invention.

[Example]
Hereinafter, a method for measuring regular discharge excluding noise components and a method for measuring non-regular discharge due to noise components, and a method for measuring the amount of received light will be described. An optical sensor that utilizes the photoelectric effect is a photocell that energizes when a photon hits an electrode. Energization proceeds under the following conditions.

[Operation of optical sensor]
When a photon hits one of the electrodes while a voltage is applied between the pair of electrodes of the optical sensor, photoelectrons are likely to jump out and energize while causing electron avalanche (a discharge current flows between the electrodes).
While the voltage is applied between the electrodes, the optical sensor continues to be energized. Alternatively, as soon as the energization of the optical sensor is confirmed, the energization is stopped by lowering the voltage. In this way, the optical sensor ends energization when the voltage between the electrodes drops.

_{Let P 1} be the probability that the optical sensor will be discharged when one photon hits the electrode of the optical sensor. _{Also, let P 2} be the probability that the optical sensor will be discharged when two photons hit the electrodes of the optical sensor. Since P ₂ is the opposite of the probability that neither the first photon nor the second photon will be discharged, _{the relationship between P 2} and P ₁ is expressed by Eq. (1).

_{Generally, let P n be} the probability that the photosensor will be discharged when _{n photons hit the electrodes of the photosensor, and P m} be the probability that the photosensor will be discharged when m photons hit the electrodes of the photosensor. (N and m are natural numbers), and equations (2) and (3) hold as in equation (1).

From equations (2) and (3), equation (4) can be derived as the relationship between _{P n} and P _m.

If the number of photons flying to the electrodes of the optical sensor per unit time is E, and the time for applying a voltage equal to or higher than the discharge start voltage of the optical sensor between the electrodes (hereinafter referred to as pulse width) is T, voltage application 1 The number of photons that collide with the electrode per turn is represented by ET. Therefore, the relationship between the number of photons E, the pulse width T, and the discharge probability P when the same optical sensor is operated under a certain condition A and another condition B is as shown in the equation (5). Here, if the reference number of photons _{is set to E 0} and Q = E / E ₀ , then the equation (6) is obtained. Here, Q is referred to as a light receiving amount.

[Configuration and operation of optical detection system]
FIG. 1 is a block diagram showing a configuration of a photodetection system according to an embodiment of the present invention. The photodetector system drives the photosensor and calculates the discharge probability and the amount of light received from the light source from the drive result of the photosensor. In this light detection system, a light sensor 1 that detects light (ultraviolet rays) generated from a light source 100 (first light source) such as a flame, an LED, or a lamp, an external power source 2, an optical sensor 1, and an external power source 2 are connected. The arithmetic device 3 is provided with an additional light source 101 (second light source) installed so that the generated light is incident on the light sensor 1 together with the light from the light source 100.

The optical sensor 1 is supported by a cylindrical enclosure with both ends closed, two electrode pins penetrating both ends of the enclosure, and electrode pins inside the enclosure in parallel with each other. It is composed of a phototube provided with two electrodes. In such an optical sensor 1, when a predetermined voltage is applied between the electrodes via the electrode support pins and ultraviolet rays are applied to one of the electrodes arranged to face the light source 100, the electrode has a photoelectric effect. Electrons are emitted and a discharge current flows between the electrodes.

The external power supply 2 comprises, for example, an AC commercial power supply having a voltage value of 100 [V] or 200 [V].

The arithmetic unit 3 includes a power supply circuit 11 connected to an external power supply 2, an applied voltage generation circuit 12 and a trigger circuit 13 connected to the power supply circuit 11, a terminal 1b on the downstream side of the optical sensor 1, and a grounding line GND. The voltage (reference voltage) Va generated at the connection point Pa between the resistors R1 and R2 of the voltage dividing resistor 14 and the voltage dividing resistor 14 composed of the resistors R1 and R2 connected in series between the two flows through the optical sensor 1. A current detection circuit 15 that detects as a current I, a processing circuit 16 in which an applied voltage generation circuit 12, a trigger circuit 13, and a current detection circuit 15 are connected, and a light source control unit 21 that controls lighting / extinguishing of an additional light source 101. It has.

The power supply circuit 11 supplies AC power input from the external power supply 2 to the applied voltage generation circuit 12 and the trigger circuit 13. Further, the electric power for driving the arithmetic unit 3 is acquired from the power supply circuit 11. However, it can also be configured to acquire driving power from another power source regardless of AC / DC.

The applied voltage generation circuit 12 (applied voltage generation unit) boosts the AC voltage applied by the power supply circuit 11 to a predetermined value and applies it to the optical sensor 1. In this embodiment, a pulsed voltage of 200 [V] synchronized with the rectangular pulse PS from the processing circuit 16 ( _{voltage equal to or higher than the discharge start voltage VST} of the optical sensor 1) is generated as the drive pulse voltage PM, and this generation is performed. The driven pulse voltage PM is applied to the optical sensor 1. FIG. 2 shows the drive pulse voltage PM applied to the optical sensor 1. The drive pulse voltage PM is synchronized with the rectangular pulse PS from the processing circuit 16, and its pulse width T is equal to the pulse width of the rectangular pulse PS. The rectangular pulse PS from the processing circuit 16 will be described later.

The trigger circuit 13 detects a predetermined value point of the AC voltage applied by the power supply circuit 11, and inputs the detection result to the processing circuit 16. In this embodiment, the trigger circuit 13 detects the minimum value point at which the voltage value becomes the minimum as a predetermined value point (at the time of triggering). By detecting a predetermined value point for the AC voltage in this way, it is possible to detect one cycle of the AC voltage.

The voltage dividing resistor 14 generates a reference voltage Va as a voltage dividing voltage between the resistors R1 and R2, and inputs the reference voltage Va to the current detection circuit 15. Here, the voltage value of the drive pulse PM applied to the terminal 1a on the upstream side of the optical sensor 1 is as high as 200 [V] as described above, so that a current is generated between the electrodes of the optical sensor 1. If the voltage generated in the terminal 1b on the downstream side when the current flows is input to the current detection circuit 15 as it is, a large load will be applied to the current detection circuit 15. Therefore, in this embodiment, the voltage dividing resistor 14 generates a reference voltage Va having a low voltage value, and this is input to the current detection circuit 15.

The current detection circuit 15 (current detection unit) detects the reference voltage Va input from the voltage dividing resistor 14 as the discharge current I of the optical sensor 1, and inputs the detected reference voltage Va as the detection voltage Vpv to the processing circuit 16. do.
The processing circuit 16 includes a square pulse generation unit 17, an A / D conversion unit 18, a sensitivity parameter storage unit 19, and a central processing unit 20.

The rectangular pulse generation unit 17 generates a rectangular pulse PS having a pulse width T every time the trigger circuit 13 detects the trigger time point, that is, every cycle of the AC voltage applied from the power supply circuit 11 to the trigger circuit 13. The square pulse PS generated by the square pulse generation unit 17 is sent to the applied voltage generation circuit 12. The rectangular pulse generation unit 17 and the applied voltage generation circuit 12 can adjust the pulse width of the drive pulse voltage PM. That is, when the rectangular pulse generation unit 17 sets the pulse width of the rectangular pulse PS to a desired value, the drive pulse voltage PM having a pulse width equal to that of the rectangular pulse PS is output from the applied voltage generation circuit 12.
The A / D conversion unit 18 A / D converts the detection voltage Vpv from the current detection circuit 15 and sends it to the central processing unit 20.

The central processing unit 20 is realized by hardware including a processor and a storage device and a program that realizes various functions in cooperation with these hardware, and includes a discharge determination unit 201 and discharge probability calculation units 202 and 203. , It functions as a pulse application number integration unit 204, an application number determination unit 205, a light reception amount calculation unit 206, and a light reception amount determination unit 207.

In the central processing unit 20, the discharge determination unit 201 detects the discharge of the optical sensor 1 based on the discharge current of the optical sensor 1 detected by the current detection circuit 15. Specifically, the discharge determination unit 201 determines the detection voltage Vpv input from the A / D conversion unit 18 each time the drive pulse voltage PM is applied to the optical sensor 1 (every time a rectangular pulse PS is generated). It is compared with a predetermined threshold voltage Vth (see FIG. 2), and when the detected voltage Vpv exceeds the threshold voltage Vth, it is determined that the optical sensor 1 has been discharged, and the number of discharges n is increased by 1.

The discharge probability calculation unit 202 performs the discharge determination unit 201 when the number of times N of the drive pulse voltage PM applied to the optical sensor 1 exceeds a predetermined number (when the number of pulses of the rectangular pulse PS exceeds a predetermined number). The discharge probability P of the optical sensor 1 is calculated from the number of discharges n detected by the above and the number of times N of application of the drive pulse voltage PM.

This discharge probability P is output as a frame signal. Certain operating conditions, the received light amount _{Q 0 (Q 0 ≠ 0)} , the discharge probability P ₀ of the pulse width T ₀ is known. For example, in the shipping inspection of a photodetection system, there is a method of measuring the discharge probability P at a predetermined light receiving amount and pulse width. At this time, the relationship between the received light amount Q, the pulse width T, and the discharge probability P is given by the equation (7). However, P = 0 is Q = 0. In the present invention, when P = 0 and P = 1, it is excluded from the calculation process of the received light amount Q.

Now, Q ₀ , T ₀ , and P ₀ are known, and T is known because the pulse width is controlled by the photodetection system. If the drive pulse voltage PM is applied to the optical sensor 1 a plurality of times, the number of discharges n is measured, and the discharge probability P is calculated, the light receiving amount Q, which is an unknown number, can be calculated from the equation (7). This received light amount Q may be output as a frame signal.

[Operation of photodetection system considering noise]
From the equation (7), it is assumed that the discharge probability P _{aA at} a certain operating condition, the light receiving amount Q ₀ , and the pulse width T ₀ is known, and the relationship between the received light amount Q, the pulse width T, and the discharge probability P is expressed by the equation (8). Given.

The following two can be considered as the relationship between the discharge of the optical sensor 1 and the time.
(A) Discharge that appears with a uniform probability while the drive pulse voltage PM is applied (Equation (8)).
(B) Drive pulse voltage A discharge that appears when the PM rises or falls.

Next, the relationship between the discharge of the optical sensor 1 and the amount of light received can be considered as follows.
(A) A discharge that appears according to the relationship between the amount of light received and the formula (8).
(B) Discharge that appears regardless of the amount of light received.

As shown in the matrix of Table 1, the noise discharge of the optical sensor 1 can be categorized by the combination of (a), (b) and (A), (B). In the present invention, the combination of (a) and (A) (aA), the combination of (a) and (B) (aB), the combination of (b) and (A) (bA), (b) and (B) It is highly probable that the combination of (bB) is surely observed.

The discharge of the combination of aA is a normal discharge called "sensitivity" (already incorporated in equation (8)). The discharge of the combination of aB is a discharge irrelevant to the amount of ultraviolet rays triggered by thermions and the like. The discharge of the combination of bA is a discharge that depends on the amount of light among the discharges that are limitedly generated when the drive pulse voltage rises or falls due to the inrush current or the residual ions. The discharge of the combination of bB is a discharge that does not depend on the amount of light among the discharges that are limitedly generated when the drive pulse voltage rises or falls due to the inrush current or the residual ions.

It should be noted that the ones categorized in Table 1 are not all of the UV (ultraviolet) failure modes. For example, there are failure modes not included in Table 1, such as discharge not being cut off and sensitivity wavelengths being different.

The above discharge of aA and the noise discharge of the three types of aB, bA, and bB can be expressed in the form of equation (9).

In equation (9), P _aB is the light receiving amount Q, the discharge probability of aB at the pulse width T, P _bA is the light receiving amount Q, the discharge probability of bA at the pulse width T, P _bB is the light receiving amount Q, bB at the pulse width T. Discharge probability of.

[Calculation method of discharge probabilities P _aA and P _bA]
In equation (9), it is assumed _{that the discharge probabilities P aA} , P _bA , and the amount of light Q are unknown, and the discharge probabilities P _aB , P _{bB are known.} For example, in addition to the light source 100, the amount of light received when the additional light source 101 having a known light amount is turned on is Q ₁ , and the amount of light received when only the light source 100 is turned off is Q ₂ (Q ₁ ≠ Q). When _2), since the difference between the amount of received light Q _1, Q ₂ a quantity of additional light source 101, also received light amount Q _1, Q ₂ is an unknown value, Q ₁ -Q ₂ are known values It becomes. If the discharge probability when the light receiving amount Q ₁ ^{is 1} P and the light receiving amount Q ₁ and the discharge probability ¹ P are substituted into the equation (9), the equation (10) is obtained.

Further, if the discharge probability when the light receiving amount Q ₂ ^{is 2} P and the light receiving amount Q ₂ and the discharge probability ² P are substituted into the equation (9), the equation (11) is obtained.

Dividing equation (10) by equation (11) yields equation (12).

Further, the pulse width of the drive pulse voltage PM is at T _1, ¹ ₁ P a discharge probability when the amount of received light Q _1, the pulse width of the driving pulse voltage PM in the T _1, discharge when the amount of received light Q ₂ ' Assuming that the probability is ² ₁ P, the equation (13) can be obtained from the equation (12).

Also, when the pulse width of the drive pulse voltage PM is T ₂ (T ₁ ≠ T ₂ ) and the received light amount is Q ₁ , the discharge probability is ¹ ₂ P, and the pulse width of the drive pulse voltage PM is T ₂ and the received light amount. If the discharge probability when is Q ₂ ^{is 2} ₂ P, the equation (14) can be obtained from the equation (12).

Table 2 summarizes the notation of each discharge probability when the received light amounts Q ₁ and Q ₂ and the pulse widths T ₁ and T _{2 are combined and measured.}

By dividing the equation (13) by the equation (14) and transforming it, the discharge probability P _aA can be obtained as in the equation (15).

Further, by substituting the equation (15) into the equation (12), the discharge probability P _bA can be obtained as in the equation (16).

Therefore, the discharge probabilities P _aA and P _bA can be obtained by measuring the discharge probabilities ¹ ₁ P, ² ₁ P, ¹ ₂ P, ² ₂ P, ¹ P, and ^{2 P, respectively.}
In addition, T = T ₁ may be set. The discharge probability P _{bA in} this case can be obtained as in Eq. (17).

Further, T = T ₂ may be set. The discharge probability P _{bA in} this case can be obtained as in Eq. (18).

[Calculation method of received light amount Q]
In the equation (9), when the discharge probabilities P _aA and P _aB are known from the equations (15) and (16) and the discharge probabilities P _bA and P _bB are also known, the equation (9) is modified from the equation (9). By substituting the equation (15) and the equation (16), the light receiving amount Q can be obtained as in the equation (19).

Therefore, even when at least one of the discharge probabilities P _aA and P _bA is unknown, by using an additional light source 101 having a known light amount in addition to the light source 100 to be detected, the amount of light received is as shown in equation (19). Q can be obtained.

Hereinafter, the operation of the photodetector system of this embodiment will be described in more detail. 3 and 4 are flowcharts for explaining the operation of the photodetection system of this embodiment.
First, the discharge probability calculation unit 202 initializes the variable i for pulse width control to 1 (step S100 in FIG. 3). Then, the discharge probability calculation unit 202 instructs the light source control unit 21 to turn on the additional light source 101.

In response to an instruction from the discharge probability calculation unit 202, the light source control unit 21 turns on the additional light source 101 (step S101 in FIG. 3). The amount of light received by the optical sensor 1 at this time is an unknown value Q ₁ . The additional light source 101 includes, for example, an LED.

When the variable i is smaller than 3 (YES in step S102 in FIG. 3), the discharge probability calculation unit 202 instructs the rectangular pulse generation unit 17 to start applying the drive pulse voltage PM. In response to the instruction from the discharge probability calculation unit 202, the square pulse generation unit 17 sets the pulse width of the square pulse PS to a predetermined value _Ti = T ₁ . By setting this pulse width, the applied voltage generation circuit 12 applies _{the drive pulse voltage PM having the pulse width Ti} = T ₁ between the pair of terminals 1a and 1b of the optical sensor 1 (step S103 in FIG. 3).

The discharge determination unit 201 compares the detection voltage Vpv from the current detection circuit 15 with the predetermined threshold voltage Vth, and determines that the optical sensor 1 has been discharged when the detection voltage Vpv exceeds the threshold voltage Vth. .. When the discharge determination unit 201 determines that the optical sensor 1 has been discharged, the discharge determination unit 201 counts the number of discharges ¹ _inn = ¹ ₁ n as one time (step S104 in FIG. 3). It goes without saying that the initial values of the number of discharges ¹ ₁ n and the number of times the drive pulse voltage PM applied ¹ _{1 N, which will be described later, are both 0.} In this way, the processes of steps S103 and S104 are repeatedly executed.

^{The pulse application number integrating unit 204 counts the number of application times 1} _i N of the drive pulse voltage PM by counting the rectangular pulse PS output from the rectangular pulse generation unit 17.
The application number determination unit 205 ^{compares the application frequency 1} _i N of the drive pulse voltage PM with the predetermined number N th.

The discharge probability calculation unit 202 ^{applies that the number of times 1} _i N = ¹ ₁ N of the drive pulse voltage PM applied from the start of application of the drive pulse voltage PM of the _{pulse width T i} = T ₁ in step S103 exceeds a predetermined number Nth. the number (YES in Fig. 3 step S105) when the determination unit 205 determines, ¹ discharge number detected by the driving pulse application number of the voltage PM ¹ _i n = ¹ ₁ n and the discharge unit 201 at this time _i n = ¹ _{Based on 1} ^{n, the discharge probability 1} ₁ P is calculated by the equation (20) (step S106 in FIG. 3).
¹ ₁ P = ¹ ₁ n / ¹ ₁ N ・ ・ ・ (20)

After calculating the discharge probability ¹ ₁ P, the discharge probability calculation unit 202 increases the variable i for pulse width control by 1 (step S107 in FIG. 3). When the variable i is smaller than 3 (YES in step S102), the discharge probability calculation unit 202 instructs the rectangular pulse generation unit 17 to start applying the drive pulse voltage PM again.

In response to the instruction from the discharge probability calculation unit 202, the square pulse generation unit 17 temporarily stops the output of the square wave PS, and then sets the pulse width of the square wave PS to a predetermined value T _i = T ₂ (T ₁ ≠ T). Set to _2). By setting this pulse width, the applied voltage generation circuit 12 applies _{the drive pulse voltage PM of the pulse width Ti} = T ₂ between the pair of terminals 1a and 1b of the optical sensor 1 (step S103).

The discharge determination unit 201 compares the detection voltage Vpv from the current detection circuit 15 with the threshold voltage Vth in the same manner as described above, and determines that the optical sensor 1 has been discharged when the detection voltage Vpv exceeds the threshold voltage Vth. the number of discharges ¹ _i n = ¹ ₂ n is increased by one (step S104). It goes without saying that the initial values of the number of discharges ¹ ₂ n and the number of times the drive pulse voltage PM applied ¹ _{2 N, which will be described later, are both 0.} In this way, the processes of steps S103 and S104 are repeatedly executed.

The discharge probability calculation unit 202 ^{applies that the number of times 1} _i N = ¹ ₂ N of the drive pulse voltage PM applied from the start of application of the drive pulse voltage PM of the _{pulse width T i} = T ₂ in step S103 exceeds a predetermined number Nth. When the number determination unit 205 determines (YES in step S105), the number of times the drive pulse voltage PM is applied at this time is ¹ _i N = ¹ ₂ N and the number of discharges detected by the discharge determination unit 201 is ¹ _i n = ¹ ₂ n. Based on the above, the discharge probability ¹ ₂ P is calculated by the equation (21) (step S106).
¹ ₂ P = ¹ ₂ n / ¹ ₂ N ・ ・ ・ (21)

After calculating the discharge probability ¹ ₂ P, the discharge probability calculation unit 202 increases the variable i for pulse width control by 1 (step S107). Discharge probability calculation unit 202, when the measurement when the amount of received light Q ₁ has ended, i.e. when the variable i has reached 3 (NO in step S102), and initializes a variable i (FIG. 3 step S108) .. Then, the discharge probability calculation unit 202 instructs the light source control unit 21 to turn off the additional light source 101.

In response to an instruction from the discharge probability calculation unit 202, the light source control unit 21 turns off the additional light source 101 (step S109 in FIG. 3). The amount of light received by the optical sensor 1 at this time is an unknown value Q ₂ . As mentioned above, Q ₁ − Q ₂ are known values.

When the variable i is smaller than 3 (YES in step S110 of FIG. 3), the discharge probability calculation unit 202 instructs the rectangular pulse generation unit 17 to start applying the drive pulse voltage PM. In response to the instruction from the discharge probability calculation unit 202, the square pulse generation unit 17 sets the pulse width of the square pulse PS to a predetermined value _Ti = T ₁ . By setting this pulse width, the applied voltage generation circuit 12 applies _{the drive pulse voltage PM having the pulse width Ti} = T ₁ between the pair of terminals 1a and 1b of the optical sensor 1 (step S111 in FIG. 3).

The discharge determination unit 201 compares the detection voltage Vpv from the current detection circuit 15 with the threshold voltage Vth in the same manner as described above, and determines that the optical sensor 1 has been discharged when the detection voltage Vpv exceeds the threshold voltage Vth. The number of discharges ² _i n = ² ₁ n is increased by 1 (step S112). It goes without saying that the initial values of the number of discharges ² ₁ n and the number of times the drive pulse voltage PM applied ² _{1 N, which will be described later, are both 0.} In this way, the processes of steps S111 and S112 are repeatedly executed.

The discharge probability calculation unit 202 ^{applies when the number of times 2} _i N = ² ₁ N of the drive pulse voltage PM applied from the start of application of the drive pulse voltage PM of the _{pulse width T i} = T ₁ in step S111 exceeds a predetermined number Nth. the number (YES in Fig. 3 step S113) when the determination unit 205 determines, discharge frequency detected by the drive pulse number of the voltage PM ² _i n = ² ₁ n and the discharge unit 201 of the time ² _i n = ² _{Based on 1} ^{n, the discharge probability 2} ₁ P is calculated by the equation (22) (step S114 in FIG. 3).
² ₁ P = ² ₁ n / ² ₁ N ・ ・ ・ (22)

After calculating the discharge probability ² ₁ P, the discharge probability calculation unit 202 increases the variable i for pulse width control by 1 (step S115 in FIG. 3). When the variable i is smaller than 3 (YES in step S110), the discharge probability calculation unit 202 instructs the rectangular pulse generation unit 17 to start applying the drive pulse voltage PM again.

In response to the instruction from the discharge probability calculation unit 202, the square pulse generation unit 17 temporarily stops the output of the square wave PS, and then sets the pulse width of the square wave PS to a predetermined value T _i = T ₂ (T ₁ ≠ T). Set to _2). By setting this pulse width, the applied voltage generation circuit 12 applies _{the drive pulse voltage PM of the pulse width Ti} = T ₂ between the pair of terminals 1a and 1b of the optical sensor 1 (step S111).

The discharge determination unit 201 compares the detection voltage Vpv from the current detection circuit 15 with the threshold voltage Vth in the same manner as described above, and determines that the optical sensor 1 has been discharged when the detection voltage Vpv exceeds the threshold voltage Vth. The number of discharges ² _i n = ² ₂ n is increased by 1 (step S112). It goes without saying that the initial values of the number of discharges ² ₂ n and the number of times the drive pulse voltage PM applied ² _{2 N, which will be described later, are both 0.} In this way, the processes of steps S111 and S112 are repeatedly executed.

The discharge probability calculation unit 202 ^{applies that the number of times 2} _i N = ² ₂ N of the drive pulse voltage PM applied from the start of application of the drive pulse voltage PM of the _{pulse width T i} = T ₂ in step S111 exceeds a predetermined number Nth. When the number determination unit 205 determines (YES in step S113), the number of times the drive pulse voltage PM is applied at this time is ² _i N = ² ₂ N and the number of discharges detected by the discharge determination unit 201 is ² _i n = ² ₂ n. based on the bets, calculates the discharge probability ² ₂ P by the equation (23) (step S114).
² ₂ P = ² ₂ n / ² ₂ N ・ ・ ・ (23)

After calculating the discharge probability ² ₂ P, the discharge probability calculation unit 202 increases the variable i for pulse width control by 1 (step S115). Discharge probability calculation unit 202, when the measurement when the received light quantity Q ₂ has ended, i.e. when the variable i has reached 3 (NO in step S110), and instructed to turn the additional light source 101 to the light source control unit 21 Later, the rectangular pulse generation unit 17 is instructed to start applying the drive pulse voltage PM.
In response to an instruction from the discharge probability calculation unit 202, the light source control unit 21 turns on the additional light source 101 (step S116 in FIG. 3). The amount of light received by the optical sensor 1 at this time is Q ₁ .

In response to the instruction from the discharge probability calculation unit 202, the square pulse generation unit 17 sets the pulse width of the square pulse PS to a predetermined value T. By setting this pulse width, the applied voltage generation circuit 12 applies the drive pulse voltage PM of the pulse width T between the pair of terminals 1a and 1b of the optical sensor 1 (step S117 in FIG. 3).

The discharge determination unit 201 compares the detection voltage Vpv from the current detection circuit 15 with the threshold voltage Vth in the same manner as described above, and determines that the optical sensor 1 has been discharged when the detection voltage Vpv exceeds the threshold voltage Vth. The number of discharges n ₁ is increased by 1 (step S118 in FIG. 3). Needless to say, the initial values of the number of discharges n _{1 and the number of times N 1} of the drive pulse voltage PM applied, which will be described later, are both 0. In this way, the processes of steps S117 and S118 are repeatedly executed.

_{When the discharge probability calculation unit 202 determines that the number of times N 1} of the drive pulse voltage PM applied from the start of application of the drive pulse voltage PM in step S117 exceeds a predetermined number Nth, the application number determination unit 205 determines (FIG. 3, step S119). ^{In YES), the discharge probability 1} P is calculated by the equation (24) based on the _{number of times N 1} of the drive pulse voltage PM applied at this time and the number of times of _{discharge n 1} detected by the discharge determination unit 201 (step 3 in FIG. 3). S120).
¹ P = n ₁ / N ₁ ... (24)

After calculating the discharge probability ¹ P, the discharge probability calculation unit 202, after instructed to turn off the additional light source 101 to the light source control unit 21, instructs the rectangular pulse generating unit 17 to start the application of the drive pulse voltage PM. In response to an instruction from the discharge probability calculation unit 202, the light source control unit 21 turns off the additional light source 101 (step S121 in FIG. 3). The amount of light received by the optical sensor 1 at this time is Q ₂ .

In response to the instruction from the discharge probability calculation unit 202, the square pulse generation unit 17 temporarily stops the output of the square wave PS, and then sets the pulse width of the square wave PS again to a predetermined value T. By setting this pulse width, the applied voltage generation circuit 12 applies the drive pulse voltage PM of the pulse width T between the pair of terminals 1a and 1b of the optical sensor 1 (step S122 in FIG. 3).

The discharge determination unit 201 compares the detection voltage Vpv from the current detection circuit 15 with the threshold voltage Vth in the same manner as described above, and determines that the optical sensor 1 has been discharged when the detection voltage Vpv exceeds the threshold voltage Vth. The number of discharges n ₂ is increased by 1 (step S123 in FIG. 3). Needless to say, the initial values of the number of discharges n _{2 and the number of times N 2} of the drive pulse voltage PM applied, which will be described later, are both 0. In this way, the processes of steps S122 and S123 are repeatedly executed.

_{When the discharge probability calculation unit 202 determines that the number of times N 2} of application of the drive pulse voltage PM from the start of application of the drive pulse voltage PM in step S122 exceeds a predetermined number Nth by the application number determination unit 205 (FIG. 3, step S124). ^{In YES), the discharge probability 2} P is calculated by the equation (25) based on the _{number of times N 2} of the drive pulse voltage PM applied at this time and the number of times of _{discharge n 2} detected by the discharge determination unit 201 (step 3 in FIG. 3). S125).
² P = n ₂ / N ₂ ... (25)

In the sensitivity parameter storage unit 19, as known sensitivity parameters of the optical sensor 1, the reference light receiving amount Q _{0 of the optical sensor 1, the reference pulse width T 0} of the drive pulse voltage PM, and the discharge probability P aB of the non-regular discharge are _stored. , P _bB and the difference in the amount of received light between when the additional light source 101 is turned on and when it is turned off Q ₁ − Q ₂ are stored in advance.

As described above, the discharge probability P _aB is due to a noise component other than the discharge due to the photoelectric effect of the optical sensor 1, which is generated depending on the pulse width of the drive pulse voltage PM and not depending on the amount of light received by the optical sensor 1. The probability of discharge. The discharge probability P _bB is the probability of discharge due to a noise component other than the discharge due to the photoelectric effect of the optical sensor 1, which is generated independently of the pulse width of the drive pulse voltage PM and the amount of light received by the optical sensor 1.
The sensitivity parameter stored in the sensitivity parameter storage unit 19 shall be measured in advance, for example, in the shipping inspection of the photodetection system.

After calculating the discharge probability ² P, the discharge probability calculation unit 203 has the discharge probabilities ¹ ₁ P, ² ₁ P, ¹ ₂ P, ² ₂ P and the discharge probabilities ¹ ₁ P, ^{2 calculated by the discharge probability calculation unit 202.} a pulse width T ₁ of the drive pulse voltage PM when seeking ₁ P, the pulse width T ₂ of the drive pulse voltage PM when seeking discharge probability ^{1 ₂} P, _{2 2} P, stored on the sensitivity parameter storage unit 19 The discharge probability P _aA is calculated by the equation (15) based on the parameters T ₀ , Q ₀ , and Q ₁ −Q ₂ (FIG. 3, step S126). The discharge probability P _aA is the discharge probability of normal discharge when the pulse width of the drive pulse voltage PM is the reference pulse width T ₀ and the light reception amount of the optical sensor 1 is the reference light reception amount Q _{0 as described above.}

Further, the discharge probability calculation unit 203 includes discharge probabilities ¹ ₁ P, ² ₁ P, ¹ ₂ P, ² ₂ P, ¹ P, ² P and discharge probabilities ¹ ₁ P, ^{2 calculated by the discharge probability calculation unit 202.} a pulse width T ₁ of the drive pulse voltage PM when seeking ₁ P, the pulse width T ₂ of the drive pulse voltage PM when seeking discharge probability ^{1 ₂} P, _{2 2} P, discharge probability ¹ P, ² P The discharge probability P _bA is calculated by Eq. (16) based on the pulse width T of the drive pulse voltage PM and the parameters Q ₀ and Q ₁ −Q _{2 stored in the sensitivity parameter storage unit 19.} (FIG. 3, step S127). As described above, the discharge probability P _bA is due to noise components other than discharge due to the photoelectric effect of the optical sensor 1, which are generated independently of the pulse width of the drive pulse voltage PM and depending on the amount of light received by the optical sensor 1. The probability of discharge.

_{When the discharge probabilities P aA} and P _bA calculated by the discharge probability calculation unit 203 are greater than 0 and less than 1 (YES in step S128 of FIG. 3), the light receiving amount calculation unit 206 proceeds to the calculation process of the light receiving amount Q. The rectangular pulse generation unit 17 is instructed to start applying the drive pulse voltage PM. _{Further, when at least one of the discharge probabilities P aA} and P _bA is 0 (NO in step S128), the light receiving amount calculation unit 206 sets the light receiving amount Q to 0 or makes it impossible to calculate the light receiving amount Q as an exception. The process is performed (step S129 in FIG. 3). Further, when at least one of the discharge probabilities P _aA and P _bA is 1 (NO in step S128), the light receiving amount calculation unit 206 performs exception processing so that the light receiving amount Q cannot be calculated (step S129).

In response to the instruction from the light receiving amount calculation unit 206, the square pulse generation unit 17 temporarily stops the output of the square wave PS, and then sets the pulse width of the square wave PS again to a predetermined value T. By setting this pulse width, the applied voltage generation circuit 12 applies the drive pulse voltage PM of the pulse width T between the pair of terminals 1a and 1b of the optical sensor 1 (step S130 in FIG. 4).

The discharge determination unit 201 compares the detection voltage Vpv from the current detection circuit 15 with the threshold voltage Vth in the same manner as described above, and determines that the optical sensor 1 has been discharged when the detection voltage Vpv exceeds the threshold voltage Vth. The number of discharges n ₃ is increased by 1 (step S131 in FIG. 4). Needless to say, the initial values of the number of discharges n _{3 and the number of times N 3} of the drive pulse voltage PM applied, which will be described later, are both 0. In this way, the processes of steps S130 and S131 are repeatedly executed.

_{When the discharge probability calculation unit 202 determines that the number of times N 3} of the drive pulse voltage PM applied from the start of application of the drive pulse voltage PM in step S130 exceeds a predetermined number Nth, the application number determination unit 205 determines (FIG. 4, step S132). In YES), the discharge probability P is calculated by the equation (26) based on the _{number of times N 3} of the drive pulse voltage PM applied at this time and the number of times of _{discharge n 3} detected by the discharge determination unit 201 (FIG. 4 step S133). ).
P = n ₃ / N ₃ ... (26)

Light amount calculating section 206, when the discharge probability P calculated by the discharge probability calculation unit 202 is greater and less than 1 than 0 (YES in FIG. 4 step S134), the discharge was calculated by the discharge probability calculation unit 202 probability ¹ P, ² P, P, the pulse width T of the drive pulse voltage PM when the ^{discharge probabilities 1} P, ² _{P, P are obtained, and the parameters T 0} , P _aB , P stored in the sensitivity parameter storage unit 19. _{Based on bB} and Q ₁ −Q ₂ , the received light amount Q is calculated by the equation (19) (FIG. 4, step S135).

Further, when the discharge probability P calculated by the discharge probability calculation unit 202 is 0 (NO in step S134), the light receiving amount calculation unit 206 sets the light receiving amount Q to 0 or makes it impossible to calculate the light receiving amount Q. Exception handling is performed (step S136 in FIG. 4). Further, when the discharge probability P is 1 (NO in step S134), the light receiving amount calculation unit 206 performs an exception process that makes it impossible to calculate the light receiving amount Q (step S136).

Next, the light receiving amount determination unit 207 compares the light receiving amount Q calculated by the light receiving amount calculation unit 206 with the predetermined light receiving amount threshold Qth (step S137 in FIG. 4), and the light receiving amount Q exceeds the light receiving amount threshold Qth. If (YES in step S137), it is determined that there is a flame (FIG. 4, step S138). Further, when the light receiving amount Q is equal to or less than the light receiving amount threshold Qth (NO in step S137), the light receiving amount determining unit 207 determines that there is no flame (FIG. 4, step S139).

As can be seen from the above description, in this embodiment, the discharge probability _PaA of the normal discharge excluding the noise component and the amount of light received by the optical sensor 1 are generated independently of the pulse width of the drive pulse voltage PM. It is possible to calculate _{the discharge probability P bA} of the non-normal discharge that occurs depending on the discharge. Discharge probability P _aA with the degradation of the optical sensor 1, it is considered that P _bA changes, discharge probability P _aA, it is possible to realize a life determination of the optical sensor 1 based on P _bA.

Further, in this embodiment, _{even when at least one of the discharge probabilities P aA} and P _bA is unknown, the light receiving amount Q excluding the noise component can be calculated, and the presence or absence of the flame can be accurately determined from the obtained light receiving amount Q. It can be detected well. Further, in this embodiment, it is possible to reduce the possibility that the life of the optical sensor 1 is erroneously determined by the light receiving amount Q including the noise component.

In this embodiment, T ≠ T ₁ ≠ T ₂ may be set, or T = T _{1 or T = T 2} may be set. When T = T ₁ , the process shown in FIG. 5 can be performed instead of the process shown in FIG. The processing of steps S100 to S115 of FIG. 5 is as described with reference to FIG.

The discharge probability calculation unit 203 calculates _{the discharge probability P aA} by the equation (15) _{when the measurement at the received light amount Q 2} is completed, that is, when the variable i reaches 3 (NO in step S110 of FIG. 5). (FIG. 5 step S126).
Further, when the discharge probability calculation unit 203 obtains the discharge probabilities ¹ ₁ P, ² ₁ P, ¹ ₂ P, ² ₂ P and the discharge probabilities ¹ ₁ P, ² ₁ P calculated by the discharge probability calculation unit 202. The pulse width T ₁ of the drive pulse voltage PM, the pulse width T ₂ of the drive pulse voltage PM when the discharge probabilities ¹ ₂ P and ² _{2 P are obtained, and the parameter Q 0} stored in the sensitivity parameter storage unit 19. , Q ₁ − Q ₂ and so on, the discharge probability P _bA is calculated by the equation (17) (FIG. 5, step S127a). The processing of steps S128 and S129 is as described with reference to FIG. Further, since the processing after step S130 is as described with reference to FIG. 4, the illustration is omitted.

The case of T = T _{2 is the same as} the case of T = T ₁ . When T = T ₂ , the discharge probability calculation unit 203 may calculate the discharge probability P _bA by the equation (18) in step S127a of FIG. Other processing is the same as in the case of _{T = T 1.}

Further, in this embodiment, the discharge probabilities P _aA and P _bA and the light receiving amount Q are calculated, but when _{only the discharge probabilities P aA} and P _bA are calculated, the light receiving amount calculation unit 206 and the light receiving amount determination are performed. The processing of unit 207 and steps S128 and subsequent steps is unnecessary.

Further, when calculating only the light receiving amount Q, the discharge probability calculation unit 203 is unnecessary. However, if the discharge probability calculation unit 203 is not provided, the processes of steps S126 to S128 of FIG. 3 cannot be performed. Therefore, when the discharge probability calculation unit 203 is not provided, the process shown in FIG. 6 may be performed instead of the process shown in FIG. The processing of steps S100 to S125 of FIG. 6 is as described with reference to FIG.

After calculating the discharge probability ² P, the light receiving amount calculation unit 206 determines that the discharge probabilities ¹ ₁ P, ² ₁ P, ¹ ₂ P, ² ₂ P calculated by the discharge probability calculation unit 202 are greater than 0 and less than 1. (YES in step S128a in FIG. 6), the process proceeds to the calculation process of the light receiving amount Q, and the rectangular pulse generation unit 17 is instructed to start applying the drive pulse voltage PM (step S130 in FIG. 4).

^{Further, when at least one of the discharge probabilities 1} ₁ P, ² ₁ P, ¹ ₂ P, and ² ₂ P calculated by the discharge probability calculation unit 202 is 0, the light receiving amount calculation unit 206 (NO in step S128a). An exception process is performed in which the light receiving amount Q is set to 0 or the light receiving amount Q cannot be calculated (step S129 in FIG. 6). Further, the light receiving amount calculation unit 206 is an exception that the light receiving amount Q cannot be calculated when at least one ^{of the discharge probabilities 1} ₁ P, ² ₁ P, ¹ ₂ P, and ² _{2 P is 1 (NO in step S128a).} The process is performed (step S129). Since the processing after step S130 is as described with reference to FIG. 4, the illustration is omitted.

Further, in this embodiment, the state in which the additional light source 101 is turned on is defined as the first state (pulse width T ₁ ), the second state (pulse width T ₂ ), and the fifth state (pulse width T), and the additional light source is set. The state in which 101 is turned off is defined as the third state (pulse width T ₁ ), the fourth state (pulse width T ₂ ), and the sixth state (pulse width T), and Q ₁ −Q ₂ is a positive value (Q). _{Although 1} > Q ₂ ), Q ₁ − Q ₂ may be a negative value (Q ₁ <Q ₂ ).

Specifically, the discharge probability calculation unit 202 turns off the additional light source 101 in steps S101 and S116 of FIGS. 3, 5, and 6, and turns off the additional light source 101 in steps S109 and S121 of FIGS. 3, 5, and 6. The 101 may be turned on. As a result, the additional light source 101 is turned off, _{the state where the pulse width is T 1} is turned off, the additional light source 101 is turned off, the state where the pulse width is T ₂ is the second state, and the additional light source 101 is turned off. The state where the pulse width is T is the fifth state, the additional light source 101 is lit, _{the state where the pulse width is T 1} is the third state, the state where the additional light source 101 is lit, and _{the state where the pulse width is T 2} is the fourth state. The sixth state is the state in which the additional light source 101 is turned on and the pulse width is T.

However, FIG. 3, if allowed to light an additional light source 101 in step S121 of FIG. 6, the discharge probability calculation unit 202 needs to be instructed to turn off the additional light source 101 to the light source control unit 21 after calculating the discharge probability ² P be. Further, when the additional light source 101 is turned on in step S109 of FIG. 5, the discharge probability calculation unit 202 needs to instruct the light source control unit 21 to turn off the additional light source 101 after the variable i reaches 3 in step S110. There is.

In this embodiment, the case where the light source 100 is a flame is described as an example, but the photodetection system of the present invention can be applied to a light source 100 other than the flame.

The sensitivity parameter storage unit 19 and the central processing unit 20 described in this embodiment can be realized by a computer equipped with a CPU (Central Processing Unit), a storage device, and an interface, and a program for controlling these hardware resources. can.

A configuration example of this computer is shown in FIG. The computer includes a CPU 300, a storage device 301, and an interface device (I / F) 302. The applied voltage generation circuit 12, the rectangular pulse generation unit 17, the A / D conversion unit 18, the light source control unit 21, and the like are connected to the I / F 302. In such a computer, a program for realizing the discharge probability calculation method and the received light amount measuring method of the present invention is stored in the storage device 301. The CPU 300 executes the process described in this embodiment according to the program stored in the storage device 301.

The present invention can be applied to flame detection systems. The present invention can also be applied to the detection of light other than flame.

1 ... Optical sensor, 2 ... External power supply, 3 ... Computational device, 11 ... Power supply circuit, 12 ... Applied voltage generation circuit, 13 ... Trigger circuit, 14 ... Voltage division resistance, 15 ... Current detection circuit, 16 ... Processing circuit, 17 ... Rectangular pulse generation unit, 18 ... A / D conversion unit, 19 ... Sensitivity parameter storage unit, 20 ... Central processing unit, 21 ... Light source control unit, 100 ... Light source, 101 ... Additional light source, 201 ... Discharge determination unit, 202, 203 ... Discharge probability calculation unit, 204 ... Pulse application number integration unit, 205 ... Application number determination unit, 206 ... Light source amount calculation unit, 207 ... Light source amount determination unit.

Claims (8)

An optical sensor configured to detect the light emitted from the first light source,
A second light source having a known amount of light, which is installed so that the generated light is incident on the optical sensor together with the light from the first light source,
A light source control unit configured to control the lighting / extinguishing of the second light source, and
An applied voltage generator configured to periodically apply a drive pulse voltage to the electrodes of the optical sensor,
A current detection unit configured to detect the discharge current of the optical sensor, and
A discharge determination unit configured to detect the discharge of the optical sensor based on the discharge current detected by the current detection unit, and a discharge determination unit.
The first state in which the second light source is turned on or off and the state in which the second light source is turned on / off are the same as in the first state, and the pulse width of the drive pulse voltage is the first state. A third state in which the second state different from the state and the lighting / extinguishing state of the second light source are different from the first and second states, and the pulse width of the driving pulse voltage is the same as the first state. And the fourth state in which the lighting / extinguishing state of the second light source is the same as that of the third state and the pulse width of the driving pulse voltage is the same as that of the second state. A first configuration configured to calculate the discharge probability based on the number of times the drive pulse voltage is applied by the applied voltage generator and the number of discharges detected by the discharge determination unit during the application of the drive pulse voltage. Discharge probability calculation unit and
As known sensitivity parameters of the optical sensor, the reference pulse width of the drive pulse voltage, the reference light receiving amount of the optical sensor, and the light in the first and second states and the third and fourth states. A storage unit configured to store the difference in the amount of light received by the sensor in advance,
The sensitivity parameters stored in the storage unit, the discharge probability calculated by the first discharge probability calculation unit in the first, second, third, and fourth states, and the first and first discharge probabilities. When the pulse width of the drive pulse voltage is the reference pulse width and the light reception amount of the optical sensor is the reference light reception amount based on the pulse width of the drive pulse voltage in the second, third, and fourth states. Due to the discharge probability of the normal discharge and the noise component other than the discharge due to the photoelectric effect of the optical sensor, which is generated independently of the pulse width of the drive pulse voltage and depending on the amount of light received by the optical sensor. An optical detection system including a second discharge probability calculation unit configured to calculate a discharge probability of a non-regular discharge. In the light detection system according to claim 1,
The second discharge probability calculation unit sets the reference pulse width of the drive pulse voltage to T ₀ , sets the reference light receiving amount of the optical sensor to Q ₀ , and sets the first and second states and the third and fourth states. The difference in the amount of light received by the optical sensor is Q ₁ −Q ₂ , the discharge probability calculated by the first discharge probability calculation unit in the first state is ¹ ₁ P, and the difference in the second state is Sometimes, the discharge probability calculated by the first discharge probability calculation unit is ¹ ₂ P, and the discharge probability calculated by the first discharge probability calculation unit in the third state is ² ₁ P, the first. The discharge probability calculated by the first discharge probability calculation unit in the state of 4 is ² ₂ P, the pulse width of the drive pulse voltage in the first and third states is T ₁ , and the second. When the pulse width of the drive pulse voltage in the fourth state is T ₂ , the discharge probability of the regular discharge is P _aA , and the discharge probability of the non-regular discharge is P _bA ,

To calculate the discharge probability P _{aA of the normal discharge,}

,or

A photodetection system characterized by calculating _{the discharge probability P bA} of the non-regular discharge according to the above. An optical sensor configured to detect the light emitted from the first light source,
A second light source having a known amount of light, which is installed so that the generated light is incident on the optical sensor together with the light from the first light source,
A light source control unit configured to control the lighting / extinguishing of the second light source, and
An applied voltage generator configured to periodically apply a drive pulse voltage to the electrodes of the optical sensor,
A current detection unit configured to detect the discharge current of the optical sensor, and
A discharge determination unit configured to detect the discharge of the optical sensor based on the discharge current detected by the current detection unit, and a discharge determination unit.
The first state in which the second light source is turned on or off and the state in which the second light source is turned on / off are the same as in the first state, and the pulse width of the drive pulse voltage is the first state. A third state in which the second state different from the state and the lighting / extinguishing state of the second light source are different from the first and second states, and the pulse width of the driving pulse voltage is the same as the first state. And the fourth state in which the lighting / extinguishing state of the second light source is the same as in the third state and the pulse width of the driving pulse voltage is the same as in the second state, and the second state. The lighting / extinguishing state of the light source is the same as that of the first and second states, and the pulse width of the driving pulse voltage is either the first or third state or the second or fourth state. The fifth state, which is the same or different from the first, second, third, and fourth states, and the lighting / extinguishing state of the second light source are the same as those of the third and fourth states, and For each of the sixth states in which the pulse width of the drive pulse voltage is the same as the fifth state, the number of times the drive pulse voltage is applied by the applied voltage generation unit and the discharge determination unit during the application of the drive pulse voltage. A first discharge probability calculation unit configured to calculate the discharge probability based on the number of discharges detected by
As known sensitivity parameters of the optical sensor, the reference pulse width of the drive pulse voltage, the reference light receiving amount of the optical sensor, the first, second, and fifth states and the third, fourth, and sixth states. A storage unit configured to store in advance the difference in the amount of light received by the optical sensor from the state of
Sensitivity parameters stored in the storage unit, and the discharge probability calculated by the first discharge probability calculation unit in the first, second, third, fourth, fifth, and sixth states. Based on the pulse width of the drive pulse voltage in the first, second, third, fourth, fifth, and sixth states, the pulse width of the drive pulse voltage is the reference pulse width. The said, which is generated independently of the discharge probability of a normal discharge when the received amount of light received by the optical sensor is the reference received amount and the pulse width of the drive pulse voltage, and is generated depending on the received amount of light received by the optical sensor. An optical detection system including a second discharge probability calculation unit configured to calculate the discharge probability of a non-regular discharge due to a noise component other than the discharge due to the photoelectric effect of the optical sensor. In the light detection system according to claim 3,
The second discharge probability calculation unit sets the reference pulse width of the drive pulse voltage to T ₀ , sets the reference light receiving amount of the optical sensor to Q ₀ , and sets the first, second, and fifth states and the third and third states. The difference in the amount of light received by the optical sensor between the fourth and sixth states is Q ₁ −Q ₂ , and the discharge probability calculated by the first discharge probability calculation unit in the first state is ¹ ₁ P. The discharge probability calculated by the first discharge probability calculation unit in the second state is ¹ ₂ P, and the discharge probability calculated by the first discharge probability calculation unit in the third state is ² ₁ P, the discharge probability calculated by the first discharge probability calculation unit in the fourth state is ² ₂ P, calculated by the first discharge probability calculation unit in the fifth state. The discharge probability is ¹ P, the discharge probability calculated by the first discharge probability calculation unit in the sixth state is ² P, and the pulse of the drive pulse voltage in the first and third states. The width is T ₁ , the pulse width of the drive pulse voltage in the second and fourth states is T ₂ , the pulse width of the drive pulse voltage in the fifth and sixth states is T, and the normal When the discharge probability of the discharge of is P _aA and the discharge probability of the non-regular discharge is P _bA ,

To calculate the discharge probability P _{aA of the normal discharge,}

A photodetection system characterized by calculating _{the discharge probability P bA} of the non-regular discharge according to the above. The light is emitted when the light from a second light source having a known amount of light is incident on an optical sensor that detects the light emitted from the first light source, or when the second light source is turned off in the first state. The first step of periodically applying a drive pulse voltage to the sensor electrodes,
The second step of detecting the discharge current of the optical sensor in the first state, and
A third step of detecting the discharge of the optical sensor based on the discharge current in the first state, and
The discharge probability in the first state is calculated based on the number of times the drive pulse voltage is applied by the first step and the number of discharges detected in the third step while the drive pulse voltage is applied. The fourth step to do and
When the lighting / extinguishing state of the second light source is the same as the first state and the pulse width of the driving pulse voltage is different from the first state, the electrode of the optical sensor is used. The fifth step of periodically applying the drive pulse voltage and
The sixth step of detecting the discharge current of the optical sensor in the second state, and
A seventh step of detecting the discharge of the optical sensor based on the discharge current in the second state, and
The discharge probability in the second state is calculated based on the number of times the drive pulse voltage is applied by the fifth step and the number of discharges detected in the seventh step while the drive pulse voltage is applied. Eighth step to do and
When the lighting / extinguishing state of the second light source is different from the first and second states, and the pulse width of the driving pulse voltage is the same as the first state, the optical sensor has a third state. The ninth step of periodically applying the drive pulse voltage to the electrodes,
The tenth step of detecting the discharge current of the optical sensor in the third state, and
The eleventh step of detecting the discharge of the optical sensor based on the discharge current in the third state, and
The discharge probability in the third state is calculated based on the number of times the drive pulse voltage is applied in the ninth step and the number of discharges detected in the eleventh step while the drive pulse voltage is applied. The twelfth step to do and
When the lighting / extinguishing state of the second light source is the same as the third state and the pulse width of the driving pulse voltage is the same as the second state, the electrode of the optical sensor is in the fourth state. The thirteenth step of periodically applying the drive pulse voltage and
The 14th step of detecting the discharge current of the optical sensor in the fourth state, and
A fifteenth step of detecting the discharge of the optical sensor based on the discharge current in the fourth state, and
The discharge probability in the fourth state is calculated based on the number of times the drive pulse voltage is applied in the thirteenth step and the number of discharges detected in the fifteenth step while the drive pulse voltage is applied. 16th step to do and
As known sensitivity parameters of the optical sensor, the reference pulse width of the drive pulse voltage, the reference light receiving amount of the optical sensor, and the light in the first and second states and the third and fourth states. With reference to a storage unit that stores the difference in the amount of light received by the sensor in advance, the sensitivity parameters stored in this storage unit, the discharge probabilities calculated in the fourth, eighth, twelfth, and sixteenth steps, and Based on the pulse width of the drive pulse voltage in the first, second, third, and fourth states, the pulse width of the drive pulse voltage is the reference pulse width and the light receiving amount of the optical sensor is the said. Discharge due to the photoelectric effect of the optical sensor, which is generated independently of the discharge probability of normal discharge at the reference light receiving amount and the pulse width of the driving pulse voltage and is generated depending on the received light amount of the optical sensor. A method for calculating a discharge probability of an optical detection system, which comprises a seventeenth step of calculating a discharge probability of a non-regular discharge due to a noise component other than the above. In the discharge probability calculation method of the photodetection system according to claim 5.
In the seventeenth step, the reference pulse width of the drive pulse voltage is T ₀ , the reference light receiving amount of the optical sensor is Q ₀ , and the first and second states and the third and fourth states are described. The difference in the amount of light received by the optical sensor is Q ₁ −Q ₂ , the discharge probability calculated in the fourth step is ¹ ₁ P, the discharge probability calculated in the eighth step is ¹ ₂ P, and the discharge probability calculated in the twelfth step is 1 2 P. The calculated discharge probability is ² ₁ P, the discharge probability calculated in the 16th step is ² ₂ P, and the pulse width of the drive pulse voltage in the first and third states is T ₁ , the second, When the pulse width of the drive pulse voltage in the fourth state is T ₂ , the discharge probability of the normal discharge is P _aA , and the discharge probability of the non-regular discharge is P _bA .

To calculate the discharge probability P _{aA of the normal discharge,}

,or

A method for calculating the discharge probability of an optical detection system, which comprises a step of calculating _{the discharge probability P bA} of the non-regular discharge. The light is emitted when the light from a second light source having a known amount of light is incident on an optical sensor that detects the light emitted from the first light source, or when the second light source is turned off in the first state. The first step of periodically applying a drive pulse voltage to the sensor electrodes,
The second step of detecting the discharge current of the optical sensor in the first state, and
A third step of detecting the discharge of the optical sensor based on the discharge current in the first state, and
The discharge probability in the first state is calculated based on the number of times the drive pulse voltage is applied by the first step and the number of discharges detected in the third step while the drive pulse voltage is applied. The fourth step to do and
When the lighting / extinguishing state of the second light source is the same as the first state and the pulse width of the driving pulse voltage is different from the first state, the electrode of the optical sensor is used. The fifth step of periodically applying the drive pulse voltage and
The sixth step of detecting the discharge current of the optical sensor in the second state, and
A seventh step of detecting the discharge of the optical sensor based on the discharge current in the second state, and
The discharge probability in the second state is calculated based on the number of times the drive pulse voltage is applied by the fifth step and the number of discharges detected in the seventh step while the drive pulse voltage is applied. Eighth step to do and
When the lighting / extinguishing state of the second light source is different from the first and second states, and the pulse width of the driving pulse voltage is the same as the first state, the optical sensor has a third state. The ninth step of periodically applying the drive pulse voltage to the electrodes,
The tenth step of detecting the discharge current of the optical sensor in the third state, and
The eleventh step of detecting the discharge of the optical sensor based on the discharge current in the third state, and
The discharge probability in the third state is calculated based on the number of times the drive pulse voltage is applied in the ninth step and the number of discharges detected in the eleventh step while the drive pulse voltage is applied. The twelfth step to do and
When the lighting / extinguishing state of the second light source is the same as the third state and the pulse width of the driving pulse voltage is the same as the second state, the electrode of the optical sensor is in the fourth state. The thirteenth step of periodically applying the drive pulse voltage and
The 14th step of detecting the discharge current of the optical sensor in the fourth state, and
A fifteenth step of detecting the discharge of the optical sensor based on the discharge current in the fourth state, and
The discharge probability in the fourth state is calculated based on the number of times the drive pulse voltage is applied in the thirteenth step and the number of discharges detected in the fifteenth step while the drive pulse voltage is applied. 16th step to do and
The lighting / extinguishing state of the second light source is the same as that of the first and second states, and the pulse width of the driving pulse voltage is the first and third states or the second and fourth states. The 17th step of periodically applying the drive pulse voltage to the electrode of the optical sensor in the fifth state different from the first, second, third, and fourth states, which is the same as either of the above.
The eighteenth step of detecting the discharge current of the optical sensor in the fifth state, and
A nineteenth step of detecting the discharge of the optical sensor based on the discharge current in the fifth state, and
The discharge probability in the fifth state is calculated based on the number of times the drive pulse voltage is applied in the 17th step and the number of discharges detected in the 19th step while the drive pulse voltage is applied. 20th step to do and
When the lighting / extinguishing state of the second light source is the same as the third and fourth states and the pulse width of the driving pulse voltage is the same as the fifth state, the optical sensor The 21st step of periodically applying the drive pulse voltage to the electrodes of
The 22nd step of detecting the discharge current of the optical sensor in the sixth state, and
The 23rd step of detecting the discharge of the optical sensor based on the discharge current in the sixth state, and
The discharge probability in the sixth state is calculated based on the number of times the drive pulse voltage is applied in the 21st step and the number of discharges detected in the 23rd step while the drive pulse voltage is applied. The 24th step to do and
As known sensitivity parameters of the optical sensor, the reference pulse width of the drive pulse voltage, the reference light receiving amount of the optical sensor, the first, second, and fifth states and the third, fourth, and sixth states. With reference to a storage unit that stores in advance the difference in the amount of light received by the optical sensor from the state of , The drive pulse is based on the discharge probability calculated in the 24th step and the pulse width of the drive pulse voltage in the first, second, third, fourth, fifth, and sixth states. When the pulse width of the voltage is the reference pulse width and the light receiving amount of the optical sensor is the reference light receiving amount, the discharge probability of the normal discharge and the pulse width of the driving pulse voltage are not dependent on the light sensor. A photodetector system comprising a 25th step of calculating the discharge probability of a non-regular discharge due to a noise component other than the discharge due to the photoelectric effect of the optical sensor, which is generated depending on the amount of light received. Discharge probability calculation method. In the discharge probability calculation method of the photodetection system according to claim 7.
In the 25th step, the reference pulse width of the drive pulse voltage is T ₀ , the reference light receiving amount of the optical sensor is Q ₀ , the first, second, and fifth states and the third, fourth, and fifth states. The difference in the amount of light received by the optical sensor from the state of 6 is Q ₁ −Q ₂ , the discharge probability calculated in the fourth step is ¹ ₁ P, and the discharge probability calculated in the eighth step is ¹ ₂ P. the first 12 ² ₁ P a discharge probability calculated in step, the first 16 ² ₂ P a discharge probability calculated in step, the first 20 discharge probability ¹ P calculated in step, in the 24th step The calculated discharge probability is ² P, the pulse width of the drive pulse voltage in the first and third states is T ₁ , and the pulse width of the drive pulse voltage in the second and fourth states is T. _2. When the pulse width of the drive pulse voltage in the fifth and sixth states is T, the discharge probability of the regular discharge is P _aA , and the discharge probability of the non-regular discharge is P _bA .

To calculate the discharge probability P _{aA of the normal discharge,}

A method for calculating the discharge probability of an optical detection system, which comprises calculating _{the discharge probability P bA} of the non-regular discharge.

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