JP2023006156A - Optical detection system and photon number calculation method - Google Patents

Abstract

To enable a comparison between another optical sensor and an electrical discharge level.SOLUTION: An optical detection system comprises: an electrical discharge probability calculation unit 202 for calculating electric discharge probabilities of an optical sensor 1 regarding a first state in which a focal distance of a lens mechanism 21 is a first value and a second state in which the focal distance is a second value; a sensitivity parameter storage unit 19 for preliminarily storing, as a known sensitivity parameter of the optical sensor 1, an electrical discharge probability at the time of a factory shipment; and a photon number calculation unit 205 for calculating a ratio of the number of photons reaching a light-receiving surface of the optical sensor 1 at the time of the factory shipment of the optical detection system and after on-site installation of the optical detection system, on the basis of the sensitivity parameter, the electrical discharge probabilities calculated by the electrical discharge probability calculation unit 202 at the time of the first and second states, a predetermined first ratio between a reference light-receiving amount of the optical sensor 1 and a light-receiving amount at the time of the first state, and a predetermined second ratio between the reference light-receiving amount and a light-receiving amount at the time of the second state.SELECTED DRAWING: Figure 2

Description

The present invention relates to a light detection system for detecting light such as flame.

2. Description of the Related Art A phototube type ultraviolet sensor is sometimes used as an optical sensor for detecting the presence or absence of a flame based on ultraviolet rays emitted from flame light in a combustion furnace or the like. It has been observed that in the discharge of a phototube type ultraviolet sensor, an irregular discharge phenomenon (false discharge) occurs due to noise components other than the discharge due to the photoelectric effect.

Patent Document 1 proposes a flame detection system that can determine the life of the optical sensor from the amount of light by controlling the pulse width of the driving pulse applied to the optical sensor to calculate the amount of light received by the discharge. However, the actual discharge of the optical sensor includes irregular discharge due to noise, which is collectively called a failure, and discharge occurs even when there is no light from the flame, resulting in erroneous detection in some cases. In order to eliminate such erroneous detection of discharge, it is necessary to consider the amount of received light from which the discharge probability of the noise component has been removed.

Therefore, in the flame detection system disclosed in Patent Literature 2, a method of determining the amount of received light in consideration of the irregular discharge probability of the noise component is proposed, and it is possible to accurately detect the presence or absence of a flame.
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.

The techniques disclosed in Patent Document 1, Patent Document 2, and Patent Document 3 all calculate the amount of light received by the optical sensor. However, since the amount of light received was a relative value of the solid photosensor, it was difficult to compare the degree of discharge with the photosensor of another solid.

JP 2018-84422 A JP 2018-84423 A JP-A-05-012581

SUMMARY OF THE INVENTION It is an object of the present invention to provide a photodetection system and a method for calculating the number of photons that can compare the degree of discharge with a photosensor of another solid.

A light detection system according to the present invention includes a light sensor configured to detect light emitted from a light source, and a light sensor provided between the light source and the light sensor and configured to have an adjustable focal length. a lens mechanism, an applied voltage generation section configured to periodically apply a driving pulse voltage to the electrodes of the photosensor, a current detection section configured to detect discharge current of the photosensor, 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 first state in which the focal length of the lens mechanism is a predetermined first value. , and a second state in which the focal length is a predetermined second value different from the first value, the number of times the driving pulse voltage is applied by the applied voltage generation unit, and the duration of application of the driving pulse voltage. a discharge probability calculation unit configured to calculate a discharge probability based on the number of discharges detected by the discharge determination unit; a storage section configured to store discharge probabilities in advance; sensitivity parameters stored in the storage section; and discharge probabilities calculated by the discharge probability calculation section in the first and second states; , a predetermined first ratio between the reference amount of light received by the optical sensor and the amount of light received in the first state, and a predetermined ratio between the reference amount of light received and the amount of light received in the second state a photon number calculation unit configured to calculate a ratio of the number of photons reaching the light receiving surface of the optical sensor between when the photodetection system is shipped from the factory and after the photodetection system is installed on site, based on the second ratio; It is characterized by

Further, in one configuration example of the photodetection system of the present invention, the photon number calculation unit calculates the discharge probabilities P ₁ and P ₃ calculated by the discharge probability calculation unit in the first and second states. A predetermined _first ratio r1 between the reference amount of received light and the amount of received light in the first state, and a second predetermined ratio between the reference amount of received light and the amount of received light in the second state. The ratio E/E _re of the number of photons is calculated from r ₃ and the discharge probability P _re at the time of shipment from the factory stored in the storage unit.

Also, the light detection system of the present invention includes a light sensor configured to detect light emitted from a light source, and a light sensor provided between the light source and the light sensor, and configured to be adjustable in focal length. an applied voltage generator configured to periodically apply a driving pulse voltage to the electrodes of the photosensor; and a current detector configured to detect the discharge current of the photosensor. 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 second state in which the focal length is a predetermined second value different from the first value, the number of times the driving pulse voltage is applied by the applied voltage generation unit, and the driving pulse voltage. a discharge probability calculation unit configured to calculate a discharge probability based on the number of discharges detected by the discharge determination unit during application; a photoelectric effect of the photosensor that occurs depending on the discharge probability of time, the reference pulse width of the driving pulse voltage, and the pulse width of the driving pulse voltage and independently of the amount of light received by the photosensor; The discharge probability of the first type irregular discharge due to the noise component other than the discharge due to the discharge, and the second type due to the noise component that occurs independently of the pulse width of the driving pulse voltage and the amount of light received by the optical sensor a storage unit configured to store in advance the discharge probability of irregular discharge of the above, the sensitivity parameter stored in the storage unit, and the discharge probability calculation unit in the first and second states and a predetermined first ratio between the reference amount of light received by the optical sensor and the amount of light received in the first state, and the reference amount of light received by the light sensor in the second state. and the pulse width of the drive pulse voltage in the first and second states, the light at the time of factory shipment of the photodetection system and after installation at the site and a photon number calculator configured to calculate the ratio of the number of photons reaching the light receiving surface of the sensor.

Further, in one configuration example of the photodetection system of the present invention, the photon number calculation unit calculates the discharge probabilities P ₁ and P ₃ calculated by the discharge probability calculation unit in the first and second states. A predetermined _first ratio r1 between the reference amount of received light and the amount of received light in the first state, and a second predetermined ratio between the reference amount of received light and the amount of received light in the second state. r ₃ , the discharge probability P _re at the time of shipment stored in the storage unit, the reference pulse width T ₀ of the drive pulse voltage, the discharge probability P _aB of the first type irregular discharge, the second type and the pulse width T of the driving pulse _voltage in the first and second states, the photon number ratio E/E _re is calculated. It is.
In one configuration example of the photodetection system of the present invention, the focal length of the lens mechanism is adjusted so that the ratio between the reference amount of light received and the amount of light received in the first state becomes the first ratio. The light detection system is set to the first state by controlling to the first value, and the ratio of the reference amount of light received and the amount of light received in the second state becomes the second ratio. further comprising a received light amount ratio setting unit configured to control the focal length of the lens mechanism to the second value to place the light detection system in the second state. .
Further, in one configuration example of the photodetection system of the present invention, the discharge probability calculation unit calculates the number of times the drive pulse voltage is applied by the applied voltage generation unit and the driving The discharge probability is calculated based on the number of discharges detected by the discharge determination unit during application of the pulse voltage, and the calculated discharge probability is stored in the storage unit.
In one configuration example of the photodetection system of the present invention, the amount of light received by the optical sensor after the photodetection system is installed on site is calculated based on the ratio of the number of photons calculated by the photon number calculator. It is characterized by further comprising a received light amount calculation unit configured as follows.

Further, in the method for calculating the number of photons of the present invention, when the focal length of a lens mechanism provided between a light source and a photosensor is in a first state in which the focal length is a predetermined first value, the electrodes of the photosensor a first step of periodically applying a drive pulse voltage; a second step of detecting the discharge current of the photosensor in the first state; the number of times the driving pulse voltage is applied in the first step; and the number of discharges detected in the third step during the application of the driving pulse voltage. and a fourth step of calculating the discharge probability in the first state based on and in a second state in which the focal length of the lens mechanism is a predetermined second value different from the first value. a fifth step of periodically applying a drive pulse voltage to the electrodes of the photosensor; a sixth step of detecting a discharge current of the photosensor in the second state; a seventh step of detecting the discharge of the optical sensor based on the discharge current in the state of; the number of times the driving pulse voltage is applied in the fifth step; an eighth step of calculating the discharge probability in the second state based on the number of discharges detected in step 7; By referring to a storage unit that stores discharge probabilities in advance, the sensitivity parameters stored in the storage unit, the discharge probabilities calculated in the fourth and eighth steps in the first and second states, and A predetermined first ratio between the reference amount of light received by the optical sensor and the amount of light received in the first state, and a predetermined ratio between the reference amount of light received and the amount of light received in the second state. and a ninth step of calculating the ratio of the number of photons reaching the light receiving surface of the optical sensor when the optical detection system is shipped from the factory and after it is installed on site, based on the ratio of 2. is.

Further, in the method for calculating the number of photons of the present invention, when the focal length of a lens mechanism provided between a light source and a photosensor is in a first state in which the focal length is a predetermined first value, the electrodes of the photosensor a first step of periodically applying a drive pulse voltage; a second step of detecting the discharge current of the photosensor in the first state; the number of times the driving pulse voltage is applied in the first step; and the number of discharges detected in the third step during the application of the driving pulse voltage. and a fourth step of calculating the discharge probability in the first state based on and in a second state in which the focal length of the lens mechanism is a predetermined second value different from the first value. a fifth step of periodically applying a drive pulse voltage to the electrodes of the photosensor; a sixth step of detecting a discharge current of the photosensor in the second state; a seventh step of detecting the discharge of the optical sensor based on the discharge current in the state of; the number of times the driving pulse voltage is applied in the fifth step; an eighth step of calculating the discharge probability in the second state based on the number of discharges detected in step 7; A discharge due to a photoelectric effect of the photosensor, which occurs depending on the discharge probability, the reference pulse width of the driving pulse voltage, and the pulse width of the driving pulse voltage and independently of the amount of light received by the photosensor. The discharge probability of the first type of irregular discharge due to noise components other than the By referring to a storage section storing in advance the discharge probability of normal discharge, the sensitivity parameters stored in this storage section and the sensitivity parameters are calculated in the fourth and eighth steps in the first and second states. a predetermined first ratio between the reference amount of light received by the optical sensor and the amount of light received in the first state; and the reference amount of light received by the optical sensor and the amount of light received in the second state. and the pulse width of the drive pulse voltage in the first and second states, the light reception of the optical sensor at the time of factory shipment of the light detection system and after installation at the site and a ninth step of calculating the ratio of the number of photons reaching the surface.

In one configuration example of the photon number calculation method of the present invention, the focal length of the lens mechanism is adjusted so that the ratio of the reference amount of light received and the amount of light received in the first state becomes the first ratio. to the first value to bring the photodetection system into the first state; and an eleventh step of controlling the focal length of the lens mechanism to the second value to have a ratio of two to place the photodetection system in the second state. be.
Further, one configuration example of the method for calculating the number of photons of the present invention includes a twelfth step of periodically applying a driving pulse voltage to the electrodes of the photosensor at the time of shipment from the factory before installation of the photodetection system on site; a thirteenth step of detecting the discharge current of the sensor; a fourteenth step of detecting the discharge of the optical sensor based on the discharge current; a fifteenth step of calculating a discharge probability based on the number of discharges detected in the fourteenth step during application of the pulse voltage, and storing the calculated discharge probability in the storage unit. and

According to the present invention, it is possible to calculate the ratio of the number of photons when the photodetection system is shipped from the factory and after it is installed in the field. In the present invention, by calculating the photon number ratio, the degree of discharge can be compared with that of a photosensor of another solid. Since the amount of received light determined by the conventional technique is affected by variations in the optical sensor, there is a possibility that the life of the optical sensor may be erroneously determined if the life of the optical sensor is determined based on the amount of received light. On the other hand, in the present invention, the influence of variation in the photosensor can be eliminated by calculating the ratio of the number of photons. Possibility of erroneous determination can be reduced.

FIG. 1 is a diagram for explaining the light-receiving amount ratio when the light-receiving amount of the electrode surface of the optical sensor is changed by the lens mechanism. FIG. 2 is a block diagram showing the configuration of the photodetection system according to the first embodiment of the present invention. FIG. 3 is a waveform diagram showing drive pulses applied to the photosensor and detection voltage detected in the current detection circuit in the first embodiment of the present invention. FIG. 4 is a diagram for explaining the light-receiving amount ratio when the light-receiving amount of the electrode surface of the optical sensor is changed by the lens mechanism. FIG. 5 is a flow chart for explaining the factory-shipped operation of the photodetection system according to the first embodiment of the present invention. FIG. 6 is a front view of the revolver-type lens mechanism according to the first embodiment of the present invention, viewed from the light source side. FIG. 7 is a flowchart for explaining the operation of the photodetection system according to the first embodiment of the present invention after being installed on site. FIG. 8 is a block diagram showing a configuration example of a computer that implements the photodetection system according to the first and second embodiments of the present invention.

[Principle of Invention]
In the present invention, an optical sensor with a known sensitivity parameter and a lens mechanism with a variable focal length are provided, and the discharge probability is used when the amount of light received is variable in the wavelength of light to which the optical sensor is sensitive. , to determine the photon count relative to the factory default of the photodetection system. As a lens mechanism with a variable focal length, there is an example in which a revolver-type lens mechanism having a plurality of lenses is used to vary the focal length and make the amount of received light relative.

In the present invention, the photon number ratio of the photosensor is calculated. In the technique disclosed in Patent Document 1, the amount of light received by the optical sensor is calculated, and the life of the optical sensor is determined from the amount of light received. However, since the amount of received light was a relative value of the solid optical sensor, it was difficult to compare the amount of received light with the optical sensor of another solid. In the present invention, by calculating the photon number ratio of the photosensor, the degree of discharge of the photosensors of different solids can be compared.

[First embodiment]
A method of calculating the number of photons when the amount of light received by the optical sensor is variable will be described below. In the first embodiment of the present invention, an example in which only the normal discharge of the photosensor is considered will be described. A photosensor that uses the photoelectric effect is a phototube that is energized when photons strike an electrode. Energization proceeds under the following conditions.

[Optical sensor operation]
When a photon hits one electrode while a voltage is applied between a pair of electrodes of the photosensor, photoelectrons are ejected with a certain probability, causing an electron avalanche to conduct electricity (a discharge current flows between the electrodes).
The photosensor remains energized while a voltage is applied between the electrodes. Alternatively, the energization is stopped by immediately lowering the voltage when the energization of the optical sensor is confirmed. Thus, the photosensor terminates energization when the voltage across the electrodes drops.

Let P ₁ be the probability that the photosensor discharges when one photon hits the electrode of the photosensor. Let P ₂ be the probability that the photosensor discharges when two photons hit the electrodes of the photosensor. Since P ₂ is the inverse of the probability that neither the first photon nor the second photon discharges, the relationship between P ₂ and P ₁ is represented by Equation (1).

In general, let Pn be the probability that the photosensor discharges when _n photons hit the electrodes of the photosensor, and Pm the probability that the photosensor discharges when _m photons hit the electrodes of the photosensor. (n and m are natural numbers), and equations (2) and (3) hold as well as equation (1).

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

Consider the case of detecting light through a lens with a variable focal length. E is the number of _photons arriving at the electrodes of the photosensor per unit area and per unit time; ) is denoted by T _i , the number of photons impinging on the electrode per voltage application is represented by ET _i S _l . Therefore, the relationship between the number of photons E, the area S, the pulse width T, and the discharge probability P when the same photosensor is operated under one condition A and another condition B is as shown in equation (5). Here, when the reference number of photons is defined as E ₀ and Q _A =E _A /E ₀ and Q _B =E _B /E ₀ , Equation (6) is obtained. Here, _Qi is called the amount of received light.

As shown in FIGS. 1(A) and 1(B), when the amount of light received by the electrode surface of the optical sensor 1 is assumed to be 100% by the lens mechanism 21 with _a variable focal length, the amount of light received is Qb (Qa Considering the ratio r _b of the amount of received light when ≠Qb), it can be expressed by the equation (7).

[Configuration and Operation of Photodetection System]
FIG. 2 is a block diagram showing the configuration of the photodetection system according to the first embodiment of the present invention. The photodetection system drives the photosensor and calculates the ratio of the number of photons and the amount of received light from the result of driving the photosensor. This light detection system includes an optical sensor 1 that detects light (ultraviolet rays) emitted from a light source 100 such as a flame, an LED, or a lamp, an external power supply 2, an arithmetic unit 3 to which the optical sensor 1 and the external power supply 2 are connected, A lens mechanism 21 is provided between the light source 100 and the optical sensor 1 .

The optical sensor 1 is supported parallel to each other by a cylindrical envelope closed at both ends, two electrode pins passing through both ends of the envelope, and electrode pins inside the envelope. It consists of a phototube with two electrodes. In such an optical sensor 1, when a predetermined voltage is applied between the electrodes via the electrode support pins, when one of the electrodes facing the light source 100 is irradiated with ultraviolet light, the photovoltaic effect causes the ultraviolet light to travel from that electrode. Electrons are emitted and a discharge current flows between the electrodes.

The external power supply 2 is, 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 the external power supply 2, an applied voltage generation circuit 12 and a trigger circuit 13 connected to the power supply circuit 11, a downstream terminal 1b of the optical sensor 1, and a ground line GND. A voltage (reference voltage) Va generated at a connection point Pa between a voltage dividing resistor 14 consisting of resistors R1 and R2 connected in series between A current detection circuit 15 for detecting the current I and a processing circuit 16 to which the applied voltage generation circuit 12, the trigger circuit 13 and the current detection circuit 15 are connected are provided.

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 . Power for driving the arithmetic device 3 is obtained from the power supply circuit 11 . However, it is also possible to obtain power for driving 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 pulse voltage of 200 [V] synchronized with the rectangular pulse PS from the processing circuit 16 (a voltage equal to or higher than the discharge start voltage _VST of the optical sensor 1) is generated as the driving pulse voltage PM. The driving pulse voltage PM thus obtained is applied to the optical sensor 1 . FIG. 3 shows the driving pulse voltage PM applied to the optical sensor 1. As shown in FIG. The driving 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 this detection result to the processing circuit 16 . In this embodiment, the trigger circuit 13 detects the minimum value point at which the voltage value is minimum as a predetermined value point (trigger time point). 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 divided by the resistors R1 and R2 and inputs it to the current detection circuit 15 . Here, since the voltage value of the driving pulse PM applied to the upstream terminal 1a of the optical sensor 1 is a high voltage of 200 [V] as described above, a current is generated between the electrodes of the optical sensor 1. If the voltage generated at the terminal 1b on the downstream side when the current flows is input to the current detection circuit 15 as it is, the current detection circuit 15 will be heavily loaded. Therefore, in this embodiment, the reference voltage Va having a low voltage value is generated by the voltage dividing resistor 14 and 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 photosensor 1, and inputs the detected reference voltage Va to the processing circuit 16 as the detection voltage Vpv. do.
The processing circuit 16 includes a rectangular pulse generation section 17 , an A/D conversion section 18 , a sensitivity parameter storage section 19 and a central processing section 20 .

The rectangular pulse generator 17 generates a rectangular pulse PS with a pulse width T each time the trigger circuit 13 detects a trigger point, that is, for each cycle of the AC voltage applied from the power supply circuit 11 to the trigger circuit 13 . A rectangular pulse PS generated by the rectangular pulse generation unit 17 is sent to the applied voltage generation circuit 12 . The rectangular pulse generator 17 and the applied voltage generator 12 can adjust the pulse width of the driving pulse voltage PM. That is, when the rectangular pulse generator 17 sets the pulse width of the rectangular pulse PS to a desired value, the driving pulse voltage PM having the same pulse width as the rectangular pulse PS is output from the applied voltage generating circuit 12 .
The A/D converter 18 A/D converts the detected 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 consisting of a processor and a storage device, and a program that cooperates with these hardware to realize various functions. It functions as an application number integration unit 203 , an application number determination unit 204 , a photon number calculation unit 205 , a light reception amount calculation unit 206 , a light reception amount determination unit 207 , and a light reception amount ratio setting unit 208 .

In the central processing unit 20 , the discharge determination unit 201 detects discharge of the photosensor 1 based on the discharge current of the photosensor 1 detected by the current detection circuit 15 . Specifically, each time the driving pulse voltage PM is applied to the optical sensor 1 (every time the rectangular pulse PS is generated), the discharge determination unit 201 detects the detection voltage Vpv input from the A/D conversion unit 18 and It is compared with a predetermined threshold voltage Vth (see FIG. 3), and when the detected voltage Vpv exceeds the threshold voltage Vth, it is determined that the photosensor 1 has discharged, and the number of times of discharge n is incremented by one.

When the number of times N of application 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 calculation unit 202 determines the discharge determination unit 201 The discharge probability P of the optical sensor 1 is calculated from the number of times n of discharge detected by and the number of times N of application of the driving pulse voltage PM.

This discharge probability P is output as a frame signal. Assume that the discharge probability P ₀ under certain operating conditions, the amount of received light Q ₀ (Q ₀ ≠0), and the pulse width T ₀ is known. For example, there is a method of measuring the discharge probability P at a predetermined amount of received light and pulse width in a shipping inspection of a photodetection system. At this time, the relationship between the amount of received light Q, the pulse width T, and the discharge probability P is given by equation (8). However, when P=0, Q=0. In the present invention, when P=0 and when P=1, they are excluded from the process of calculating the amount of received light Q. FIG.

Now Q ₀ , T ₀ , P ₀ are known, and T is known because it is the pulse width that the photodetector system is controlling. By applying the driving pulse voltage PM to the optical sensor 1 a plurality of times, measuring the number of times of discharge n, and calculating the discharge probability P, the unknown quantity of received light Q can be calculated from equation (8).

From equation (8), it is assumed that the discharge probability P _aA under certain operating conditions, the amount of received light Q ₀ , and the pulse width T ₀ is known. Given.

[Method for calculating the number of photons when using lenses with different focal lengths]
When the focal length of the lens mechanism 21 is changed as shown in FIGS. 4A to 4C, the discharge probability in three states with different focal lengths is P _i (i=1 to 3), and the amount of received light is be _Qi . Here, Q ₁ =r ₁ Q ₂ , Q ₃ =r ₃ Q ₂ (r ₁ ≠r ₃ ), and when the ratios r ₁ and r ₃ are known and the state shown in FIG. Suppose that the number of photons per unit area of the electrode, E, that reach the electrode of the photosensor 1 is unknown.

Equation (10) is obtained by substituting the discharge probability P ₁ and the received light amount Q ₁ when measuring in the state of FIG. Equation (11) is obtained by substituting the discharge probability P ₃ and the amount of light received Q ₃ when measured in the state in Equation (9).

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

Further, when the photodetection system is shipped from the factory, the focal length of the lens mechanism 21 is set to an arbitrary value, and the amount of received light _{Qre when} the discharge probability is _Pre is calculated. Assume that the amount of received light Q _re is known. Substituting the discharge probability P _re and the amount of received light Q _re into the equation (9), the equation is modified to obtain the equation (13).

Substituting equation (12) into equation (13) and transforming it yields equation (14).

Substituting Q ₁ =r ₁ Q ₂ and Q ₃ =r ₂ Q ₂ into equation (14) yields equation (15).

Substituting Q ₂ =(ES _l )/(E ₀ S _l ) and Q _re =(E _re S _l )/(E ₀ S _l ) into equation (15), E/E You can ask for _re .

Therefore, the known values of P ₁ , P ₃ , r ₁ , r ₂ after field installation of the photodetection system and the factory known values of P _re , Q _re determine the number of photons at factory and after field installation It becomes possible to calculate the ratio E/E _re of .

The operation of the photodetection system of this embodiment will be described in more detail below. FIG. 5 is a flow chart for explaining the operation of the photodetection system of this embodiment at the time of shipment from the factory.
For example, the focal length of the lens mechanism 21 is manually set to an arbitrary value at the inspection stage before shipment from the factory (step S100). Light from the light source 100 enters the optical sensor 1 through the lens mechanism 21 .

FIG. 6 is a front view of the revolver-type lens mechanism 21 viewed from the light source 100 side. The revolver-type lens mechanism 21 has a plurality of lenses 210 to 212 with different focal lengths fixed to a revolver 213. By rotating the revolver 213, the lens 210 is inserted between the light source 100 and the optical sensor 1. ∼212 can be changed, and the focal length can be changed.

The lens mechanism 21 is not limited to the revolver type, and may be one that can change the focal length by moving the lens along the optical axis direction.
Also, the lens mechanism 21 may be configured to include a drive mechanism such as a motor. In this case, the received light amount ratio setting unit 208 can control the focal length of the lens mechanism 21 .

The discharge probability calculator 202 instructs the rectangular pulse generator 17 to start applying the driving pulse voltage PM. The rectangular pulse generator 17 sets the pulse width of the rectangular pulse PS to a predetermined value T according to the instruction from the discharge probability calculator 202 . By setting the pulse width, the applied voltage generation circuit 12 applies the drive pulse voltage PM with the pulse width T between the pair of terminals 1a and 1b of the photosensor 1 (step S101). The pulse width T may be the same as the reference pulse width _T0 .

The discharge determination unit 201 compares the detected voltage Vpv from the current detection circuit 15 with a predetermined threshold voltage Vth, and determines that the optical sensor 1 has discharged when the detected voltage Vpv exceeds the threshold voltage Vth. . When the discharge determination unit 201 determines that the optical sensor 1 has discharged, the discharge determination unit 201 counts the number of times n of discharges as one (step S102). The initial values of the number of times n of discharge and the number of times N of application of the driving pulse voltage PM are both zero. Thus, the processes of steps S101 and S102 are repeatedly executed.

The pulse application number integrating section 203 counts the application number N of the driving pulse voltage PM by counting the rectangular pulses PS output from the rectangular pulse generating section 17 .
The number-of-applications determination unit 204 compares the number of times N of applications of the driving pulse voltage PM with a predetermined number Nth.

The discharge probability calculation unit 202 determines that the number N of applications of the driving pulse voltage PM having the pulse width T from the start of application of the driving pulse voltage PM in step S101 exceeds a predetermined number Nth (step If YES in S103), the discharge probability P _re is calculated by the equation (17) based on the number of times N of application of the driving pulse voltage PM and the number of times of discharge n detected by the discharge determination unit 201 at this time (step S104).
P _re =n/N (17)

In the sensitivity parameter storage unit 19, as known sensitivity parameters of the photosensor 1, the amount of light received by the photosensor 1 _Q0 , the reference pulse width _T0 of the drive pulse voltage PM, and the pulse width of the drive pulse voltage PM are stored as reference pulses. The discharge probability P _aA of the normal discharge when the light receiving amount of the light sensor 1 is Q ₀ with the width T ₀ and the electrode of the light sensor 1 when the reference light receiving amount Q ₂ in the state of FIG. 4B is obtained The light-receiving area S ₂ of the surface is stored in advance.

When the discharge probability P _re calculated by the discharge probability calculation unit 202 is greater than 0 and less than 1 (YES in step S105), the received light amount calculation unit 206 obtains the discharge probability P _re and the discharge probability P _re and the parameters Q ₀ , T ₀ , and P _aA stored in the sensitivity parameter storage unit 19, the amount of received light Q=Q _re is calculated by equation (9) ( step S106). In the calculation at this time, P _re may be substituted for P in equation (9).

If the discharge probability Pre calculated by the discharge probability calculation unit ₂₀₂ is 0 or 1 (NO in step S105), the received light amount calculation unit 206 returns to step S101. In this way, the processing of steps S101 to S105 is repeated until the discharge probability P _re becomes greater than 0 and less than 1, and ends when the amount of received light Q _re is calculated. The discharge probability calculation unit 202 stores the value of the discharge probability P _re that is greater than 0 and less than 1 in the sensitivity parameter storage unit 19 .

Next, the operation of the photodetection system after being installed on site will be described with reference to FIG. After the on-site installation of the photodetection system, the received light amount ratio setting unit 208 initializes the number i of the received light amount ratio and the discharge probability to 1 (step S200). The received light amount _ratio setting unit _{208 sets} the received light amount to _Q1 in the state shown in _FIG . 4A with respect to the reference received light amount Q2 in the state shown in FIG. so that the focal length of the lens mechanism 21 is controlled to a predetermined first value (step S201).

The discharge probability calculator 202 instructs the rectangular pulse generator 17 to start applying the driving pulse voltage PM. The rectangular pulse generator 17 sets the pulse width of the rectangular pulse PS to a predetermined value T according to the instruction from the discharge probability calculator 202 . By setting the pulse width, the applied voltage generation circuit 12 applies the drive pulse voltage PM with the pulse width T between the pair of terminals 1a and 1b of the photosensor 1 (step S202). Note that the pulse width T after installation on site may be a value different from the pulse width T at the time of shipment from the factory.

Similarly to the above, the discharge determination unit 201 determines that the optical sensor 1 has discharged when the detected voltage Vpv from the current detection circuit 15 exceeds the threshold voltage Vth, and increases the number of times of discharge n _i =n ₁ by 1 (step S203). _The initial values of the number of times n1 of discharge and the _number of times N1 of application of the driving pulse voltage PM are both zero. Thus, the processes of steps S202 and S203 are repeatedly executed.

The discharge probability calculation unit 202 calculates the number N of times of application of the drive pulse voltage PM from the start of application of the drive pulse voltage PM with the pulse width T in step S202._i=N₁exceeds the predetermined number Nth (YES in step S204), the number N of times of application of the driving pulse voltage PM at this time_i=N₁and the number of discharges n detected by the discharge determination unit 201_i=n₁and based on the discharge probability P by equation (18)_i=P₁is calculated (step S205).
P.₁=n₁/N₁ (18)

When the calculated discharge probability P ₁ is 0 or 1 (NO in step S206), discharge probability calculation unit 202 returns to step S202. In this way, the processes of steps S202 to S206 are repeated until the discharge probability P ₁ becomes greater than 0 and less than 1.

When the calculated discharge probability P ₁ is greater than 0 and less than 1 (YES in step S206), discharge probability calculation unit 202 increases number i by 2 (step S207). If number i is smaller than 5 (YES in step S208), discharge probability calculation unit 202 returns to step S201.

When the discharge probability P ₁ is greater than 0 and less than 1 and the number i is less than 5, the received light amount ratio setting unit 208 sets the received light amount to the reference received light amount Q ₂ in the state of FIG. The focal length of the lens mechanism 21 is controlled to a predetermined second value so that Q ₃ of the state 4(C) is established and Q ₃ =r ₃ Q ₂ is established (step S201).

Either one of the amounts of received light Q ₁ and Q ₃ may be the same as the amount of received light Q ₂ . That is, either one of the received light amount ratios r ₁ and r ₃ (r ₁ ≠r ₃ ) may be 1.

The discharge probability calculator 202 instructs the rectangular pulse generator 17 to start applying the driving pulse voltage PM. In response to the instruction from the discharge probability calculator 202, the rectangular pulse generator 17 temporarily stops the output of the rectangular pulse PS, and then sets the pulse width of the rectangular pulse PS to a predetermined value T. By setting the pulse width, the applied voltage generation circuit 12 applies the drive pulse voltage PM with the pulse width T between the pair of terminals 1a and 1b of the photosensor 1 (step S202).

Similarly to the above, the discharge determination unit 201 determines that the optical sensor 1 has discharged when the detected voltage Vpv from the current detection circuit 15 exceeds the threshold voltage Vth, and increases the number of times of discharge n _i =n ₃ by 1 (step S203). The initial values of the number of times _n3 of discharge and the number of times N3 of application of the driving pulse voltage PM are _both zero. Thus, the processes of steps S202 and S203 are repeatedly executed.

The discharge probability calculation unit 202 calculates the number N of times of application of the drive pulse voltage PM from the start of application of the drive pulse voltage PM with the pulse width T in step S202._i=N₃exceeds the predetermined number Nth (YES in step S204), the number N of times of application of the driving pulse voltage PM at this time_i=N₃and the number of discharges n detected by the discharge determination unit 201_i=n₃and based on the discharge probability P by the equation (19)_i=P₃is calculated (step S205).
P.₃=n₃/N₃ (19)

When the calculated discharge probability _P3 is 0 or 1 (NO in step S206), discharge probability calculation unit 202 returns to step S202. In this way, the processes of steps S202 to S206 are repeated until the discharge probability P ₃ becomes greater than 0 and less than 1.

When the calculated discharge probability P ₃ is greater than 0 and less than 1 (YES in step S206), discharge probability calculation unit 202 increases number i by 2 (step S207).
When the number i reaches 5 (NO in step S208), the photon number calculation unit 205 sets the discharge probabilities P ₁ and P ₃ calculated by the discharge probability calculation unit 202 and the received light amount ratio setting unit 208 to Based on the received light amount ratios r ₁ and r ₃ and the discharge probability P _re at the time of shipment from the factory stored in the sensitivity parameter storage unit 19, the number of photons at the time of shipment from the factory and after installation at the site is calculated by Equation (16). A ratio E/E _re is calculated (step S209).

Based on the photon number ratio E/E _re calculated by the photon number calculation unit 205 and the light receiving area S ₂ stored in the sensitivity parameter storage unit 19, the received light amount calculation unit 206 uses Equation (20) to obtain A light receiving amount Q is calculated (step S210).
Q=(E/ _Ere )S2 ( ₂₀ )

The received light amount determination unit 207 compares the received light amount Q calculated by the received light amount calculation unit 206 with a predetermined received light amount threshold Qth (step S211), and when the received light amount Q exceeds the received light amount threshold Qth (step S211 YES), it is determined that there is a flame (step S212). Further, when the received light amount Q is equal to or smaller than the received light amount threshold value Qth (NO in step S211), the received light amount determination unit 207 determines that there is no flame (step S213).

As described above, in this embodiment, the photon number ratio E/E _re of the optical sensor 1 can be calculated. In this embodiment, by calculating the ratio E/E _re of the number of photons, it is possible to compare the degree of discharge with that of a photosensor of another solid.

[Second embodiment]
Next, a second embodiment of the invention will be described. In the present embodiment, an example will be described in which an irregular discharge phenomenon (false discharge) due to noise components other than the discharge due to the photoelectric effect is taken into consideration. Also in the present embodiment, the configuration of the photodetection system is the same as in the first embodiment, so the reference numerals in FIG. 2 will be used for description.

[Operation of photodetection system considering noise]
As the relationship between the discharge of the optical sensor 1 and time, the following two cases are conceivable.
(a) A discharge that appears at a uniform probability during application of the driving pulse voltage PM (equation (9)).
(b) A discharge that appears when the drive pulse voltage PM rises or falls.

Next, there are two possible relationships between the discharge of the optical sensor 1 and the amount of light received.
(A) A discharge that appears according to the relationship between the amount of received light and formula (9).
(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 classified by combining (a), (b) and (A), (B). In the present invention, the combination (aA) of (a) and (A), the combination (aB) of (a) and (B), the combination (bA) of (b) and (A), (b) and (B) combination (bB) is likely to be reliably observed.

The aA combination discharge is a normal discharge (implemented in equation (9)) called 'sensitivity'. The discharge of the aB combination is a discharge that is triggered by thermal electrons and the like and is unrelated to the amount of ultraviolet rays. The discharge of the bA combination is the discharge that depends on the amount of light among the discharges that occur limitedly at the rise or fall of the drive pulse voltage due to the rush current or residual ions. The discharge of the combination bB is a discharge that does not depend on the amount of light among the discharges that are limitedly generated at the rise or fall of the drive pulse voltage due to the rush current or residual ions.

Note that not all UV (ultraviolet) failure modes are categorized in Table 1. For example, there are failure modes not included in Table 1, such as discharge failure and different sensitivity wavelengths.

The aA discharge and the three types of noise discharges aB, bA, and bB can be expressed in the form of equation (21).

In equation (21), P _aB is the discharge probability of aB at the amount of received light Q and pulse width T, P _bA is the discharge probability of bA at the amount of received light Q and pulse width T, and P _bB is bB at the amount of received light Q and pulse width T. is the discharge probability of

[Method for calculating the number of photons when using lenses with different focal lengths]
In equation (21), it is assumed that the discharge probabilities P _aB and P _bB are known. When the _focal length of the lens mechanism 21 is changed as shown in FIGS. Let the quantity be _Qi . Here, Q ₁ =r ₁ Q ₂ , Q ₃ =r ₃ Q ₂ (r ₁ ≠r ₃ ), and when the ratios r ₁ and r ₃ are known and the state shown in FIG. Suppose that the number of photons per unit area of the electrode, E, that reach the electrode of the photosensor 1 is unknown.

Equation (22) is obtained by substituting the discharge probability P ₁ and the amount of light received Q ₁ when measuring in the state of FIG. Equation (23) is obtained by substituting the discharge probability P ₃ and the amount of received light Q ₃ measured in the state of the battery into equation (21).

Dividing equation (22) by (23) yields equation (24).

Further, when the photodetection system is shipped from the factory, the focal length of the lens mechanism 21 is set to an arbitrary value, and the amount of received light _{Qre when} the discharge probability is _Pre is calculated. Assume that the amount of received light Q _re is known. Since the discharge probabilities P _aB and P _bB are known, the equation (21) when the discharge probability is P _re and the amount of received light is Q _re is modified to obtain the equation (25).

Substituting equation (24) into equation (25) and transforming it yields equation (26).

Substituting Q ₁ =r ₁ Q ₂ and Q ₃ =r ₂ Q ₂ into equation (26) yields equation (27).

Substituting Q ₂ =(ES _l )/(E ₀ S _l ) and Q _re =(E _re S _l )/(E ₀ S _l ) into equation (27), E/E You can ask for _re .

Therefore, the known values P ₁ , P ₃ , r ₁ , r ₃ after field installation of the photodetection system and the factory known values P _aB , P _bB , T ₀ , P _re , Q _re It becomes possible to calculate the photon number ratio E/E _re after shipment and after field installation.

The operation of the photodetection system of this embodiment will be described in more detail below. In this embodiment, the operation flow of the photodetection system at the time of shipment from the factory is the same as that of the first embodiment, so the operation at the time of shipment from the factory will be described with reference to FIG.
For example, at the inspection stage at the time of shipment from the factory, the focal length of the lens mechanism 21 is set to an arbitrary value by manual control or control by the received light amount ratio setting unit 208, as in the first embodiment (step S100).

The applied voltage generation circuit 12 applies a drive pulse voltage PM having a pulse width T between the pair of terminals 1a and 1b of the photosensor 1 (step S101).
The discharge determination unit 201 determines that the optical sensor 1 has discharged when the detected voltage Vpv from the current detection circuit 15 exceeds the threshold voltage Vth, and increases the number of discharges n by 1 (step S102).

When the number of times N of application of the drive pulse voltage PM having the pulse width T in step S101 has exceeded a predetermined number Nth (YES in step S103), the discharge probability calculation unit 202 Based on the number of times N of application of the drive pulse voltage PM and the number of times of discharge n detected by the discharge determination unit 201, the discharge probability P _re is calculated by the equation (17) (step S104).

When the discharge probability P _re calculated by the discharge probability calculation unit 202 is greater than 0 and less than 1 (YES in step S105), the received light amount calculation unit 206 obtains the discharge probability P _re and the discharge probability P _re and the parameters Q ₀ , T ₀ , and P _aA stored in the sensitivity parameter storage unit 19, the amount of received light Q=Q _re is calculated by equation (9) ( step S106).

When the discharge probability P _re is 0 or 1, the processing of steps S101 to S105 is repeated until the discharge probability P _re becomes greater than 0 and less than 1, and is terminated when the amount of received light Q _re is calculated. Become. The discharge probability calculation unit 202 stores the value of the discharge probability P _re that is greater than 0 and less than 1 in the sensitivity parameter storage unit 19 .

Next, the operation of the photodetection system after being installed on site will be described with reference to FIG. After the on-site installation of the photodetection system, the received light amount ratio setting unit 208 initializes the number i to 1 (step S200). The received light amount _ratio setting unit _{208 sets} the received light amount to _Q1 in the state shown in _FIG . 4A with respect to the reference received light amount Q2 in the state shown in FIG. so that the focal length of the lens mechanism 21 is controlled to a predetermined first value (step S201).

The applied voltage generation circuit 12 applies the driving pulse voltage PM with the pulse width T between the pair of terminals 1a and 1b of the photosensor 1 (step S202).
The discharge determination unit 201 determines that the optical sensor 1 has discharged when the detected voltage Vpv from the current detection circuit 15 exceeds the threshold voltage Vth, and increases the number of times of discharge n _i =n ₁ by 1 (step S203).

When the number of times of application of the driving pulse voltage PM having the pulse width T in step S202, N _i =N ₁ , exceeds a predetermined number Nth (YES in step S204). , based on the number of times of application of the drive pulse voltage PM at this time, N _i =N ₁ , and the number of times of discharge, n _i =n ₁ , detected by the discharge determination unit 201, the discharge probability P _i =P ₁ is calculated by equation (18). Calculate (step S205). When the calculated discharge probability P ₁ is greater than 0 and less than 1 (YES in step S206), discharge probability calculation unit 202 increases number i by 2 (step S207).

When the discharge probability P ₁ is greater than 0 and less than 1 and the number i is less than 5, the received light amount ratio setting unit 208 sets the reference received light amount Q _{2 ,} the amount of light received _{becomes Q3} in the state shown in _FIG . step S201).

The applied voltage generation circuit 12 applies the driving pulse voltage PM with the pulse width T between the pair of terminals 1a and 1b of the photosensor 1 (step S202).
The discharge determination unit 201 determines that the optical sensor 1 has discharged when the detected voltage Vpv from the current detection circuit 15 exceeds the threshold voltage Vth, and increases the number of times of discharge n _i =n ₃ by 1 (step S203).

When the number of times of application of the drive pulse voltage PM having the pulse width T in step S202, Ni ₌ N3, exceeds a predetermined number Nth ₍ YES in step S204). , based on the number of times of application of the drive pulse voltage PM at this time, N _i =N ₃ , and the number of times of discharge, n _i =n ₃ , detected by the discharge determination unit 201, the discharge probability of P _i =P ₃ is calculated by equation (19). Calculate (step S205). When the calculated discharge probability P ₃ is greater than 0 and less than 1 (YES in step S206), discharge probability calculation unit 202 increases number i by 2 (step S207).

In the sensitivity parameter storage unit 19 of the present embodiment, in addition to the discharge probability P _re and the light receiving area S _re at the time of shipment from the factory, the light receiving amount Q ₀ of the optical sensor 1 and the drive The reference pulse width T ₀ of the pulse voltage PM, the light receiving area S ₂ , and the discharge probabilities P _aB and P _bB of irregular discharge are stored in advance.

The discharge probability P _aB is generated depending on the pulse width of the drive pulse voltage PM and independent of the amount of light received by the optical sensor 1 as described above, and is due to noise components other than the discharge due to the photoelectric effect of the optical sensor 1. is the discharge probability. The discharge probability _PbB is the probability of discharge due to noise components other than the discharge due to the photoelectric effect of the photosensor 1, which occurs independently of the pulse width of the drive pulse voltage PM and the amount of light received by the photosensor 1, as described above. .

When the number i reaches 5 (NO in step S208), the photon number calculation unit 205 of the present embodiment sets the discharge probabilities P ₁ and P ₃ calculated by the discharge probability calculation unit 202 and the received light amount ratio setting unit 208 and the pulse width T of the drive pulse voltage PM when the discharge probabilities P ₁ and P _{3 are} obtained, and the factory default stored in the sensitivity parameter storage unit ₁₉ . Based on the discharge probability P _re , the reference pulse width T ₀ , and the discharge probabilities P _aB and P _bB of the irregular discharge, the ratio of the number of photons E/E _re is calculated (step S209).

Based on the photon number ratio E/E _re calculated by the photon number calculation unit 205 and the light receiving area S ₂ stored in the sensitivity parameter storage unit 19, the received light amount calculation unit 206 uses Equation (20) to obtain A light receiving amount Q is calculated (step S210).

The received light amount determination unit 207 compares the received light amount Q calculated by the received light amount calculation unit 206 with the received light amount threshold Qth (step S211), and if the received light amount Q exceeds the received light amount threshold Qth (YES in step S211 ), it is determined that there is a flame (step S212). Further, when the received light amount Q is equal to or smaller than the received light amount threshold value Qth (NO in step S211), the received light amount determination unit 207 determines that there is no flame (step S213).

Thus, in this embodiment, the same effect as in the first embodiment can be obtained. Further, in this embodiment, the photon number ratio E/E _re excluding noise components other than the normal discharge of the optical sensor 1 can be calculated.

In the first and second embodiments, the light source 100 is a flame.

The sensitivity parameter storage unit 19 and the central processing unit 20 described in the first and second embodiments are a computer having a CPU (Central Processing Unit), a storage device, and an interface, and a program that controls these hardware resources. It can be realized by

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 I/F 302 is connected to the applied voltage generator 12, the rectangular pulse generator 17, the A/D converter 18, and the like. In such a computer, a program for realizing the method of calculating the number of photons of the present invention is stored in the storage device 301 . The CPU 300 executes the processes described in the first and second embodiments according to programs stored in the storage device 301 .

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

Reference Signs List 1 optical sensor 2 external power supply 3 arithmetic unit 11 power supply circuit 12 applied voltage generation circuit 13 trigger circuit 14 voltage dividing resistor 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 Lens mechanism 201 Discharge determination unit 202 Discharge probability calculation unit 203 Pulse application number Integrating unit 204 Application number determination unit 205 Photon number calculation unit 206 Received light amount calculation unit 207 Received light amount determination unit 208 Received light amount ratio setting unit.

Claims (11)

a light sensor configured to detect light emitted from the light source;
a lens mechanism provided between the light source and the optical sensor and configured to be able to adjust the focal length;
an applied voltage generator configured to periodically apply a driving pulse voltage to the electrodes of the photosensor;
a current detection unit configured to detect the discharge current of the optical sensor;
a discharge determination unit configured to detect discharge of the optical sensor based on the discharge current detected by the current detection unit;
For each of a first state in which the focal length of the lens mechanism is a first predetermined value and a second state in which the focal length is a second predetermined value different from the first value, the applied A discharge probability calculation unit configured to calculate a discharge probability based on the number of times the driving pulse voltage is applied by the voltage generation unit and the number of discharges detected by the discharge determination unit during the application of the driving pulse voltage. When,
a storage unit configured to pre-store a factory discharge probability of a light detection system as a known sensitivity parameter of the light sensor;
Sensitivity parameters stored in the storage unit, discharge probabilities calculated by the discharge probability calculation unit in the first and second states, a reference amount of light received by the optical sensor, and the first state Factory shipment of the photodetection system based on a predetermined first ratio between the received light amount in the case of and a predetermined second ratio between the reference received light amount and the received light amount in the second state and a photon number calculator configured to calculate a ratio of the number of photons reaching the light receiving surface of the optical sensor at time and after installation on site. The photodetection system of claim 1, wherein
The photon number calculator calculates the ratio of the number of photons E/E _re between when the photodetection system is shipped from the factory and after it is installed on site, and is calculated by the discharge probability calculator in the first and second states. P ₁ and P ₃ are the discharge probabilities, r 1 is a predetermined first ratio between the reference amount of received light and the amount of received light in the first state, and r ₁ is the ratio of the reference amount of received light to the amount of received light in the second state. When r ₃ is a predetermined second ratio with the amount of light received at the time, and _Pre is the discharge probability at the time of shipment from the factory stored in the storage unit,

A photodetection system, wherein the photon number ratio E/E _re is calculated by: a light sensor configured to detect light emitted from the light source;
a lens mechanism provided between the light source and the optical sensor and configured to be able to adjust the focal length;
an applied voltage generator configured to periodically apply a driving pulse voltage to the electrodes of the photosensor;
a current detection unit configured to detect the discharge current of the optical sensor;
a discharge determination unit configured to detect discharge of the optical sensor based on the discharge current detected by the current detection unit;
For each of a first state in which the focal length of the lens mechanism is a first predetermined value and a second state in which the focal length is a second predetermined value different from the first value, the applied A discharge probability calculation unit configured to calculate a discharge probability based on the number of times the driving pulse voltage is applied by the voltage generation unit and the number of discharges detected by the discharge determination unit during the application of the driving pulse voltage. When,
The known sensitivity parameters of the optical sensor include the factory discharge probability of the optical detection system, the reference pulse width of the drive pulse voltage, and the pulse width of the drive pulse voltage and the sensitivity of the optical sensor. Discharge probability of first type irregular discharge due to noise components other than discharge due to photoelectric effect of the photosensor, pulse width of the driving pulse voltage, and the amount of light received by the photosensor, which occurs independently of the amount of light received a storage unit configured to store in advance the discharge probability of the second type of irregular discharge due to the noise component, which occurs independently of the
Sensitivity parameters stored in the storage unit, discharge probabilities calculated by the discharge probability calculation unit in the first and second states, a reference amount of light received by the optical sensor, and the first state a predetermined first ratio between the amount of light received in the case of and a predetermined second ratio between the reference amount of light received and the amount of light received in the second state; The number of photons configured to calculate the ratio of the number of photons reaching the light receiving surface of the optical sensor at the time of shipment from the factory and after installation at the site based on the pulse width of the driving pulse voltage at the time and a calculator. The photodetection system of claim 3, wherein
The photon number calculator calculates the ratio of the number of photons E/E _re between when the photodetection system is shipped from the factory and after it is installed on site, and is calculated by the discharge probability calculator in the first and second states. P ₁ and P ₃ are the discharge probabilities, r 1 is a predetermined first ratio between the reference amount of received light and the amount of received light in the first state, and r ₁ is the ratio of the reference amount of received light to the amount of received light in the second state. Predetermined second ratio with the amount of light received at time is r ₃ , discharge probability at factory shipment stored in the storage unit is _Pre , reference pulse width of the drive pulse voltage is T ₀ , the first type P _aB is the discharge probability of irregular discharge, P _bB is the discharge probability of the second kind of irregular discharge, and T is the pulse width of the drive pulse voltage in the first and second states. when

A photodetection system, wherein the photon number ratio E/E _re is calculated by: The photodetection system according to any one of claims 1 to 4,
controlling the focal length of the lens mechanism to the first value so that the ratio of the reference amount of light received and the amount of light received in the first state becomes the first ratio, thereby operating the light detection system; The first state is set, and the focal length of the lens mechanism is set to the second value so that the ratio between the reference amount of light received and the amount of light received in the second state becomes the second ratio. A light detection system, further comprising: a received light amount ratio setting section configured to control and bring the light detection system into the second state. The photodetection system according to any one of claims 1 to 5,
The discharge probability calculation unit calculates the number of times the drive pulse voltage is applied by the applied voltage generation unit and the number of times the discharge determination unit detects the number of times the drive pulse voltage is applied during the application of the drive pulse voltage when the photodetection system is shipped from the factory before being installed on site. and calculating a discharge probability based on the number of discharges, and storing the calculated discharge probability in the storage unit. The photodetection system according to any one of claims 1 to 6,
The method further comprises a received light amount calculation unit configured to calculate a received light amount of the optical sensor after installation of the light detection system on site, based on the ratio of the number of photons calculated by the photon number calculation unit. and a light detection system. In a first state in which a focal length of a lens mechanism provided between a light source and a photosensor is a predetermined first value, a first driving pulse voltage is periodically applied to the electrodes of the photosensor. a step of
a second step of detecting the discharge current of the photosensor when in the first state;
a third step of detecting discharge of the photosensor based on the discharge current in the first state;
A discharge probability in the first state is calculated based on the number of times the driving pulse voltage is applied in the first step and the number of discharges detected in the third step during the application of the driving pulse voltage. a fourth step of
a fifth step of periodically applying a driving pulse voltage to the electrodes of the photosensor when the focal length of the lens mechanism is in a second state of a predetermined second value different from the first value; ,
a sixth step of detecting the discharge current of the photosensor when in the second state;
a seventh step of detecting discharge of the photosensor based on the discharge current in the second state;
The discharge probability in the second state is calculated based on the number of times the driving pulse voltage is applied in the fifth step and the number of discharges detected in the seventh step during the application of the driving pulse voltage. an eighth step of
By referring to a storage section that pre-stores the discharge probability at the time of factory shipment of the photodetection system as the known sensitivity parameter of the optical sensor, the sensitivity parameter stored in the storage section and the first and second states are obtained. the discharge probability calculated in the fourth and eighth steps at the time of , a predetermined first ratio between the reference amount of light received by the optical sensor and the amount of light received in the first state, and the reference Number of photons reaching the light receiving surface of the optical sensor at the time of factory shipment of the light detection system and after installation at the site, based on the amount of light received and the predetermined second ratio of the amount of light received in the second state. and a ninth step of calculating the ratio of the number of photons. In a first state in which a focal length of a lens mechanism provided between a light source and a photosensor is a predetermined first value, a first driving pulse voltage is periodically applied to the electrodes of the photosensor. a step of
a second step of detecting the discharge current of the photosensor when in the first state;
a third step of detecting discharge of the photosensor based on the discharge current in the first state;
A discharge probability in the first state is calculated based on the number of times the driving pulse voltage is applied in the first step and the number of discharges detected in the third step during the application of the driving pulse voltage. a fourth step of
a fifth step of periodically applying a driving pulse voltage to the electrodes of the photosensor when the focal length of the lens mechanism is in a second state of a predetermined second value different from the first value; ,
a sixth step of detecting the discharge current of the photosensor when in the second state;
a seventh step of detecting discharge of the photosensor based on the discharge current in the second state;
The discharge probability in the second state is calculated based on the number of times the driving pulse voltage is applied in the fifth step and the number of discharges detected in the seventh step during the application of the driving pulse voltage. an eighth step of
The known sensitivity parameters of the optical sensor include the factory discharge probability of the optical detection system, the reference pulse width of the drive pulse voltage, and the pulse width of the drive pulse voltage and the sensitivity of the optical sensor. Discharge probability of first type irregular discharge due to noise components other than discharge due to photoelectric effect of the photosensor, pulse width of the driving pulse voltage, and the amount of light received by the photosensor, which occurs independently of the amount of light received By referring to a storage unit that stores in advance the discharge probability of the second type of irregular discharge due to the noise component that occurs independently of the above, the sensitivity parameter stored in the storage unit and the first , the discharge probability calculated in the fourth and eighth steps in the second state, and a predetermined first ratio between the reference amount of light received by the optical sensor and the amount of light received in the first state. and a predetermined second ratio between the reference amount of received light and the amount of received light in the second state, and the pulse width of the drive pulse voltage in the first and second states. and a ninth step of calculating the ratio of the number of photons reaching the light-receiving surface of the optical sensor when the photodetection system is shipped from the factory and after it is installed on site. In the photon number calculation method according to claim 8 or 9,
controlling the focal length of the lens mechanism to the first value so that the ratio of the reference amount of light received and the amount of light received in the first state becomes the first ratio, thereby operating the light detection system; a tenth step of setting the first state;
The light detection system is operated by controlling the focal length of the lens mechanism to the second value so that the ratio of the reference amount of light received and the amount of light received in the second state becomes the second ratio. and an eleventh step of setting the second state. In the photon number calculation method according to any one of claims 8 to 10,
a twelfth step of periodically applying a driving pulse voltage to the electrodes of the photosensor at factory shipment prior to on-site installation of the photodetection system;
a thirteenth step of detecting the discharge current of the photosensor;
a fourteenth step of detecting discharge of the photosensor based on the discharge current;
A discharge probability is calculated based on the number of times the drive pulse voltage is applied in the twelfth step and the number of discharges detected in the fourteenth step during the application of the drive pulse voltage, and the calculated discharge probability is calculated. and a fifteenth step of storing in the storage unit.

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