Light detection system, discharge probability calculating method, and received light quantity measuring method

A light detection system comprising:

• an optical sensor configured to detect light emitted from a first light source;
• an application voltage generating portion configured to periodically apply a drive pulse voltage to an electrode of the optical sensor;
• a current detecting portion configured to detect a discharge current of the optical sensor;
• a discharge determining portion configured to detect a discharge of the optical sensor based on the discharge current detected by the current detecting portion;
• a first discharge probability calculating portion configured to calculate a discharge probability based on the number of times of application of the drive pulse voltage applied by the application voltage generating portion and the number of times of discharge detected by the discharge determining portion during the application of the drive pulse voltage for each of a first state in which the optical sensor is shielded from the light, a second state in which the optical sensor is shielded from the light and a pulse width of the drive pulse voltage is different from that of the first state, and a third state in which the optical sensor is shielded from the light and a pulse width of the drive pulse voltage is the same as that of either the first or second state or different from those of the first and second states;
• a storing portion configured to store, in advance as a known sensitivity parameter of the optical sensor, a reference pulse width of the drive pulse voltage;
• and
• a second discharge probability calculating portion configured to calculate a discharge probability of a first type irregular discharge caused by a noise component other than a discharge occurring due to a photoelectric effect of the optical sensor, which occurs depending on the pulse width of the drive pulse voltage and which occurs without depending on a received light quantity received by the optical sensor, and a discharge probability of a second type irregular discharge caused by the noise component, which occurs without depending on the pulse width of the drive pulse voltage and the received light quantity received by the optical sensor, based on the sensitivity parameter stored in the storing portion, the discharge probabilities calculated by the first discharge probability calculating portion in the first, second, and third states, and the pulse widths of the drive pulse voltage in the first, second, and third states.

A discharge probability calculating method of a light detection system, the method comprising:

• a first step of periodically applying a drive pulse voltage to an electrode of an optical sensor that detects light emitted from a light source in a first state in which the optical sensor is shielded from the light;
• a second step of detecting a discharge current of the optical sensor in the first state;
• a third step of detecting a discharge of the optical sensor based on the discharge current in the first state;
• a fourth step of calculating a discharge probability in the first state based on the number of times of application of the drive pulse voltage applied in the first step and the number of times of discharge detected in the third step during the application of the drive pulse voltage;
• a fifth step of periodically applying the drive pulse voltage to the electrode of the optical sensor in a second state in which the optical sensor is shielded from the light and a pulse width of the drive pulse voltage is different from that of the first state;
• a sixth step of detecting a discharge current of the optical sensor in the second state;
• a seventh step of detecting a discharge of the optical sensor based on the discharge current in the second state;
• an eighth step of calculating a discharge probability in the second state based on the number of times of application of the drive pulse voltage applied in the fifth step and the number of times of discharge detected in the seventh step during the application of the drive pulse voltage;
• and
• a ninth step of referring to a storing portion that stores, in advance as a known sensitivity parameter of the optical sensor, a reference pulse width of the drive pulse voltage, and calculating a discharge probability of a first type irregular discharge caused by a noise component other than a discharge occurring due to a photoelectric effect of the optical sensor, which occurs depending on the pulse width of the drive pulse voltage and which occurs without depending on a received light quantity received by the optical sensor, and a discharge probability of a second type irregular discharge caused by the noise component, which occurs without depending on the pulse width of the drive pulse voltage and the received light quantity received by the optical sensor, based on the sensitivity parameter stored in the storing portion, the discharge probabilities calculated in the fourth and eighth steps, and the pulse widths of the drive pulse voltage in the first and second states.

A discharge probability calculating method of a light detection system, the method comprising:

• a first step of periodically applying a drive pulse voltage to an electrode of an optical sensor that detects light emitted from a light source in a first state in which the optical sensor is shielded from the light;
• a second step of detecting a discharge current of the optical sensor in the first state;
• a third step of detecting a discharge of the optical sensor based on the discharge current in the first state;
• a fourth step of calculating a discharge probability in the first state based on the number of times of application of the drive pulse voltage applied in the first step and the number of times of discharge detected in the third step during the application of the drive pulse voltage;
• a fifth step of periodically applying the drive pulse voltage to the electrode of the optical sensor in a second state in which the optical sensor is shielded from the light and a pulse width of the drive pulse voltage is different from that of the first state;
• a sixth step of detecting a discharge current of the optical sensor in the second state;
• a seventh step of detecting a discharge of the optical sensor based on the discharge current in the second state;
• an eighth step of calculating a discharge probability in the second state based on the number of times of application of the drive pulse voltage applied in the fifth step and the number of times of discharge detected in the seventh step during the application of the drive pulse voltage;
• a ninth step of periodically applying the drive pulse voltage to the electrode of the optical sensor in a third state in which the optical sensor is shielded from the light and a pulse width of the drive pulse voltage is the same as that of either the first or second state or different from those of the first and second states;
• a tenth step of detecting a discharge current of the optical sensor in the third state;
• an eleventh step of detecting a discharge of the optical sensor based on the discharge current in the third state;
• a twelfth step of calculating a discharge probability in the third state based on the number of times of application of the drive pulse voltage applied in the ninth step and the number of times of discharge detected in the eleventh step during the application of the drive pulse voltage;
• and
• a thirteenth step of referring to a storing portion that stores, in advance as a known sensitivity parameter of the optical sensor, a reference pulse width of the drive pulse voltage, and calculating a discharge probability of a first type irregular discharge caused by a noise component other than a discharge occurring due to a photoelectric effect of the optical sensor, which occurs depending on the pulse width of the drive pulse voltage and which occurs without depending on a received light quantity received by the optical sensor, and a discharge probability of a second type irregular discharge caused by the noise component, which occurs without depending on the pulse width of the drive pulse voltage and the received light quantity received by the optical sensor, based on the sensitivity parameter stored in the storing portion, the discharge probabilities calculated in the fourth, eighth, and twelfth steps, and the pulse widths of the drive pulse voltage in the first, second, and third states.

A received light quantity measuring method of a light detection system, the method comprising:

• a first step of periodically applying a drive pulse voltage to an electrode of an optical sensor that detects light emitted from a first light source in a first state in which the optical sensor is shielded from the light;
• a second step of detecting a discharge current of the optical sensor in the first state;
• a third step of detecting a discharge of the optical sensor based on the discharge current in the first state;
• a fourth step of calculating a discharge probability in the first state based on the number of times of application of the drive pulse voltage applied in the first step and the number of times of discharge detected in the third step during the application of the drive pulse voltage;
• a fifth step of periodically applying the drive pulse voltage to the electrode of the optical sensor in a second state in which the optical sensor is shielded from the light and a pulse width of the drive pulse voltage is different from that of the first state;
• a sixth step of detecting a discharge current of the optical sensor in the second state;
• a seventh step of detecting a discharge of the optical sensor based on the discharge current in the second state;
• an eighth step of calculating a discharge probability in the second state based on the number of times of application of the drive pulse voltage applied in the fifth step and the number of times of discharge detected in the seventh step during the application of the drive pulse voltage;
• a ninth step of referring to a storing portion that stores, in advance as a known sensitivity parameter of the optical sensor, a reference pulse width of the drive pulse voltage, and calculating a discharge probability of a first type irregular discharge caused by a noise component other than a discharge occurring due to a photoelectric effect of the optical sensor, which occurs depending on the pulse width of the drive pulse voltage and which occurs without depending on a received light quantity received by the optical sensor, and a discharge probability of a second type irregular discharge caused by the noise component, which occurs without depending on the pulse width of the drive pulse voltage and the received light quantity received by the optical sensor, based on the sensitivity parameter stored in the storing portion, the discharge probabilities calculated in the fourth and eighth steps, and the pulse widths of the drive pulse voltage in the first and second states;
• a tenth step of periodically applying the drive pulse voltage to the electrode of the optical sensor in a third state in which light from a second light source having a known light quantity is incident on the optical sensor or the second light source is turned off;
• an eleventh step of detecting a discharge current of the optical sensor in the third state;
• a twelfth step of detecting a discharge of the optical sensor based on the discharge current in the third state;
• a thirteenth step of calculating a discharge probability in the third state based on the number of times of application of the drive pulse voltage applied in the tenth step and the number of times of discharge detected in the twelfth step during the application of the drive pulse voltage;
• a fourteenth step of periodically applying the drive pulse voltage to the electrode of the optical sensor in a fourth state in which a turning-on/turning-off state of the second light source is different from that of the third state and a pulse width of the drive pulse voltage is the same as that of the third state;
• a fifteenth step of detecting a discharge current of the optical sensor in the fourth state;
• a sixteenth step of detecting a discharge of the optical sensor based on the discharge current in the fourth state;
• a seventeenth step of calculating a discharge probability in the fourth state based on the number of times of application of the drive pulse voltage applied in the fourteenth step and the number of times of discharge detected in the sixteenth step during the application of the drive pulse voltage;
• and
• an eighteenth step of referring to the storing portion that stores, in advance as known sensitivity parameters of the optical sensor, a difference in received light quantity received by the optical sensor between the third state and the fourth state in addition to the reference pulse width of the drive pulse voltage, and calculating the received light quantities received by the optical sensor in the third and fourth states, based on the sensitivity parameters stored in the storing portion, the discharge probabilities calculated in the thirteenth and seventeenth steps, the pulse widths of the drive pulse voltage in the third and fourth states, and the discharge probabilities calculated in the ninth step.

A received light quantity measuring method of a light detection system, the method comprising:

• a first step of periodically applying a drive pulse voltage to an electrode of an optical sensor that detects light emitted from a first light source in a first state in which the optical sensor is shielded from the light;
• a second step of detecting a discharge current of the optical sensor in the first state;
• a third step of detecting a discharge of the optical sensor based on the discharge current in the first state;
• a fourth step of calculating a discharge probability in the first state based on the number of times of application of the drive pulse voltage applied in the first step and the number of times of discharge detected in the third step during the application of the drive pulse voltage;
• a fifth step of periodically applying the drive pulse voltage to the electrode of the optical sensor in a second state in which the optical sensor is shielded from the light and a pulse width of the drive pulse voltage is different from that of the first state;
• a sixth step of detecting a discharge current of the optical sensor in the second state;
• a seventh step of detecting a discharge of the optical sensor based on the discharge current in the second state;
• an eighth step of calculating a discharge probability in the second state based on the number of times of application of the drive pulse voltage applied in the fifth step and the number of times of discharge detected in the seventh step during the application of the drive pulse voltage;
• a ninth step of referring to a storing portion that stores, in advance as a known sensitivity parameter of the optical sensor, a reference pulse width of the drive pulse voltage, and calculating a discharge probability of a first type irregular discharge caused by a noise component other than a discharge occurring due to a photoelectric effect of the optical sensor, which occurs depending on the pulse width of the drive pulse voltage and which occurs without depending on a received light quantity received by the optical sensor, and a discharge probability of a second type irregular discharge caused by the noise component, which occurs without depending on the pulse width of the drive pulse voltage and the received light quantity received by the optical sensor, based on the sensitivity parameter stored in the storing portion, the discharge probabilities calculated in the fourth and eighth steps, and the pulse widths of the drive pulse voltage in the first and second states;
• a tenth step of periodically applying the drive pulse voltage to the electrode of the optical sensor in a third state in which light from a second light source having a known light quantity is incident on the optical sensor or the second light source is turned off;
• an eleventh step of detecting a discharge current of the optical sensor in the third state;
• a twelfth step of detecting a discharge of the optical sensor based on the discharge current in the third state;
• a thirteenth step of calculating a discharge probability in the third state based on the number of times of application of the drive pulse voltage applied in the tenth step and the number of times of discharge detected in the twelfth step during the application of the drive pulse voltage;
• a fourteenth step of periodically applying the drive pulse voltage to the electrode of the optical sensor in a fourth state in which a turning-on/turning-off state of the second light source is different from that of the third state and a pulse width of the drive pulse voltage is the same as that of the third state;
• a fifteenth step of detecting a discharge current of the optical sensor in the fourth state;
• a sixteenth step of detecting a discharge of the optical sensor based on the discharge current in the fourth state;
• a seventeenth step of calculating a discharge probability in the fourth state based on the number of times of application of the drive pulse voltage applied in the fourteenth step and the number of times of discharge detected in the sixteenth step during the application of the drive pulse voltage;
• an eighteenth step of periodically applying the drive pulse voltage to the electrode of the optical sensor in a fifth state in which the second light source is turned off and a pulse width of the drive pulse voltage is the same as that of the third and fourth states;
• a nineteenth step of detecting a discharge current of the optical sensor in the fifth state;
• a twentieth step of detecting a discharge of the optical sensor based on the discharge current in the fifth state;
• a twenty-first step of calculating a discharge probability in the fifth state based on the number of times of application of the drive pulse voltage applied in the eighteenth step and the number of times of discharge detected in the twentieth step during the application of the drive pulse voltage;
• and
• a twenty-second step of referring to the storing portion that stores, in advance as known sensitivity parameters of the optical sensor, a difference in received light quantity received by the optical sensor between the third state and the fourth state in addition to the reference pulse width of the drive pulse voltage, and calculating received light quantities received by the optical sensor in the third, fourth, and fifth states, based on the sensitivity parameters stored in the storing portion, the discharge probabilities calculated in the thirteenth, seventeenth, and twenty-first steps, the pulse widths of the drive pulse voltage in the third, fourth, and fifth states, and the discharge probabilities calculated in the ninth step.

A received light quantity measuring method of a light detection system, the method comprising:

• a first step of periodically applying a drive pulse voltage to an electrode of an optical sensor that detects light emitted from a first light source in a first state in which the optical sensor is shielded from the light;
• a second step of detecting a discharge current of the optical sensor in the first state;
• a third step of detecting a discharge of the optical sensor based on the discharge current in the first state;
• a fourth step of calculating a discharge probability in the first state based on the number of times of application of the drive pulse voltage applied in the first step and the number of times of discharge detected in the third step during the application of the drive pulse voltage;
• a fifth step of periodically applying the drive pulse voltage to the electrode of the optical sensor in a second state in which the optical sensor is shielded from the light and a pulse width of the drive pulse voltage is different from that of the first state;
• a sixth step of detecting a discharge current of the optical sensor in the second state;
• a seventh step of detecting a discharge of the optical sensor based on the discharge current in the second state;
• an eighth step of calculating a discharge probability in the second state based on the number of times of application of the drive pulse voltage applied in the fifth step and the number of times of discharge detected in the seventh step during the application of the drive pulse voltage;
• a ninth step of periodically applying the drive pulse voltage to the electrode of the optical sensor in a third state in which the optical sensor is shielded from the light and a pulse width of the drive pulse voltage is the same as that of either the first or second state or different from those of the first and second states;
• a tenth step of detecting a discharge current of the optical sensor in the third state;
• an eleventh step of detecting a discharge of the optical sensor based on the discharge current in the third state;
• a twelfth step of calculating a discharge probability in the third state based on the number of times of application of the drive pulse voltage applied in the ninth step and the number of times of discharge detected in the eleventh step during the application of the drive pulse voltage;
• a thirteenth step of referring to a storing portion that stores, in advance as a known sensitivity parameter of the optical sensor, a reference pulse width of the drive pulse voltage, and calculating a discharge probability of a first type irregular discharge caused by a noise component other than a discharge occurring due to a photoelectric effect of the optical sensor, which occurs depending on the pulse width of the drive pulse voltage and which occurs without depending on a received light quantity received by the optical sensor, and a discharge probability of a second type irregular discharge caused by the noise component, which occurs without depending on the pulse width of the drive pulse voltage and the received light quantity received by the optical sensor, based on the sensitivity parameter stored in the storing portion, the discharge probabilities calculated in the fourth, eighth, and twelfth steps, and the pulse widths of the drive pulse voltage in the first, second, and third states;
• a fourteenth step of periodically applying the drive pulse voltage to the electrode of the optical sensor in a fourth state in which light from a second light source having a known light quantity is incident on the optical sensor or the second light source is turned off;
• a fifteenth step of detecting a discharge current of the optical sensor in the fourth state;
• a sixteenth step of detecting a discharge of the optical sensor based on the discharge current in the fourth state;
• a seventeenth step of calculating a discharge probability in the fourth state based on the number of times of application of the drive pulse voltage applied in the fourteenth step and the number of times of discharge detected in the sixteenth step during the application of the drive pulse voltage;
• an eighteenth step of periodically applying the drive pulse voltage to the electrode of the optical sensor in a fifth state in which a turning-on/turning-off state of the second light source is different from that of the fourth state and a pulse width of the drive pulse voltage is the same as that of the fourth state;
• a nineteenth step of detecting a discharge current of the optical sensor in the fifth state;
• a twentieth step of detecting a discharge of the optical sensor based on the discharge current in the fifth state;
• a twenty-first step of calculating a discharge probability in the fifth state based on the number of times of application of the drive pulse voltage applied in the eighteenth step and the number of times of discharge detected in the twentieth step during the application of the drive pulse voltage;
• and
• a twenty-second step of referring to the storing portion that stores, in advance as known sensitivity parameters of the optical sensor, a difference in received light quantity received by the optical sensor between the fourth state and the fifth state in addition to the reference pulse width of the drive pulse voltage, and calculating the received light quantities received by the optical sensor in the fourth and fifth states, based on the sensitivity parameters stored in the storing portion, the discharge probabilities calculated in the seventeenth and twenty-first steps, the pulse widths of the drive pulse voltage in the fourth and fifth states, and the discharge probabilities calculated in the thirteenth step.

A received light quantity measuring method of a light detection system, the method comprising:

• a first step of periodically applying a drive pulse voltage to an electrode of an optical sensor that detects light emitted from a first light source in a first state in which the optical sensor is shielded from the light;
• a second step of detecting a discharge current of the optical sensor in the first state;
• a third step of detecting a discharge of the optical sensor based on the discharge current in the first state;
• a fourth step of calculating a discharge probability in the first state based on the number of times of application of the drive pulse voltage applied in the first step and the number of times of discharge detected in the third step during the application of the drive pulse voltage;
• a fifth step of periodically applying the drive pulse voltage to the electrode of the optical sensor in a second state in which the optical sensor is shielded from the light and a pulse width of the drive pulse voltage is different from that of the first state;
• a sixth step of detecting a discharge current of the optical sensor in the second state;
• a seventh step of detecting a discharge of the optical sensor based on the discharge current in the second state;
• an eighth step of calculating a discharge probability in the second state based on the number of times of application of the drive pulse voltage applied in the fifth step and the number of times of discharge detected in the seventh step during the application of the drive pulse voltage;
• a ninth step of periodically applying the drive pulse voltage to the electrode of the optical sensor in a third state in which the optical sensor is shielded from the light and a pulse width of the drive pulse voltage is the same as that of either the first or second state or different from those of the first and second states;
• a tenth step of detecting a discharge current of the optical sensor in the third state;
• an eleventh step of detecting a discharge of the optical sensor based on the discharge current in the third state;
• a twelfth step of calculating a discharge probability in the third state based on the number of times of application of the drive pulse voltage applied in the ninth step and the number of times of discharge detected in the eleventh step during the application of the drive pulse voltage;
• a thirteenth step of referring to a storing portion that stores, in advance as a known sensitivity parameter of the optical sensor, a reference pulse width of the drive pulse voltage, and calculating a discharge probability of a first type irregular discharge caused by a noise component other than a discharge occurring due to a photoelectric effect of the optical sensor, which occurs depending on the pulse width of the drive pulse voltage and which occurs without depending on a received light quantity received by the optical sensor, and a discharge probability of a second type irregular discharge caused by the noise component, which occurs without depending on the pulse width of the drive pulse voltage and the received light quantity received by the optical sensor, based on the sensitivity parameter stored in the storing portion, the discharge probabilities calculated in the fourth, eighth, and twelfth steps, and the pulse widths of the drive pulse voltage in the first, second, and third states;
• a fourteenth step of periodically applying the drive pulse voltage to the electrode of the optical sensor in a fourth state in which light from a second light source having a known light quantity is incident on the optical sensor or the second light source is turned off;
• a fifteenth step of detecting a discharge current of the optical sensor in the fourth state;
• a sixteenth step of detecting a discharge of the optical sensor based on the discharge current in the fourth state;
• a seventeenth step of calculating a discharge probability in the fourth state based on the number of times of application of the drive pulse voltage applied in the fourteenth step and the number of times of discharge detected in the sixteenth step during the application of the drive pulse voltage;
• an eighteenth step of periodically applying the drive pulse voltage to the electrode of the optical sensor in a fifth state in which a turning-on/turning-off state of the second light source is different from that of the fourth state and a pulse width of the drive pulse voltage is the same as that of the fourth state;
• a nineteenth step of detecting a discharge current of the optical sensor in the fifth state;
• a twentieth step of detecting a discharge of the optical sensor based on the discharge current in the fifth state;
• a twenty-first step of calculating a discharge probability in the fifth state based on the number of times of application of the drive pulse voltage applied in the eighteenth step and the number of times of discharge detected in the twentieth step during the application of the drive pulse voltage;
• a twenty-second step of periodically applying the drive pulse voltage to the electrode of the optical sensor in a sixth state in which the second light source is turned off and a pulse width of the drive pulse voltage is the same as that of the fourth and fifth states;
• a twenty-third step of detecting a discharge current of the optical sensor in the sixth state;
• a twenty-fourth step of detecting a discharge of the optical sensor based on the discharge current in the sixth state;
• a twenty-fifth step of calculating a discharge probability in the sixth state based on the number of times of application of the drive pulse voltage applied in the twenty-second step and the number of times of discharge detected in the twenty-fourth step during the application of the drive pulse voltage;
• and
• a twenty-sixth step of referring to the storing portion that stores, in advance as known sensitivity parameters of the optical sensor, a difference in received light quantity received by the optical sensor between the fourth state and the fifth state in addition to the reference pulse width of the drive pulse voltage, and calculating received light quantities received by the optical sensor in the fourth, fifth, and sixth states, based on the sensitivity parameters stored in the storing portion, the discharge probabilities calculated in the seventeenth, twenty-first, and twenty-fifth steps, the pulse widths of the drive pulse voltage in the fourth, fifth, and sixth states, and the discharge probabilities calculated in the thirteenth step.