Light detection system and discharge probability calculating method

Patent metadata

Field	Value
Publication number	US-12153166-B2
Application number	US-202117168667-A
Country	US
Kind code	B2
Filing date	Feb 5, 2021
Priority date	Feb 18, 2020
Publication date	Nov 26, 2024
Grant date	Nov 26, 2024

Abstract

To calculate a probability of an optical sensor's irregular discharge, a light detection system includes an optical sensor, an application voltage generating circuit that applies a drive pulse voltage to the optical sensor, a discharge determining portion that detects the optical sensor's discharge, a discharge probability calculating portion that calculates a discharge probability in a first state in which light from an additional light source having a known light quantity is incident on the optical sensor or the additional light source is turned off, and in a second state in which the additional light source's turning-on/turning-off state is different from the first state and the drive pulse voltage's pulse width is the same as the first state, a sensitivity parameter storing portion that stores the optical sensor's sensitivity parameters, and another discharge probability calculating portion that calculates a discharge probability of the optical sensor's irregular discharge.

First claim

The invention claimed is:

1. A light detection system comprising:
an optical sensor configured to detect light emitted from a first light source;
a second light source having a known light quantity, which is installed such that generated light is incident on the optical sensor together with the light from the first light source;
a light source control portion configured to control turning-on/turning-off of the second 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 second light source is turned on or turned off, and a second state in which a turning-on/turning-off state of the second light source is different from that of the first state and a pulse width of the drive pulse voltage is the same as that of the first state;
a storing portion configured to store, in advance as known sensitivity parameters of the optical sensor, a reference pulse width of the drive pulse voltage, a reference received light quantity received by the optical sensor, a discharge probability of a regular discharge when the pulse width of the drive pulse voltage is the reference pulse width and a received light quantity received by the optical sensor is the reference received light quantity, and a difference in received light quantity received by the optical sensor between the first state and the second state; and
a second discharge probability calculating portion configured to calculate a discharge probability of an irregular discharge caused by a noise component other than a discharge occurring due to a photoelectric effect of the optical sensor, which occurs without depending on the pulse width of the drive pulse voltage and which occurs depending on the received light quantity received by the optical sensor, based on the sensitivity parameters stored in the storing portion, the discharge probabilities calculated by the first discharge probability calculating portion in the first and second states, and the pulse width of the drive pulse voltage in the first and second states.

2. The light detection system according to claim 1 , wherein
the second discharge probability calculating portion is configured to calculate a discharge probability P bA Of the irregular discharge by using

P
bA

=

1
-

(

1
-

1

P

1
-

2

P

)

Q
0

Q
1

-

Q
2

·

(

1
-

P
aA

)

-

T

T
0

where T 0 is the reference pulse width of the drive pulse voltage, Q 0 is the reference received light quantity received by the optical sensor, P aA is the discharge probability of the regular discharge, Q 1 −Q 2 is the difference in received light quantity received by the optical sensor between the first state and the second state, 1 P is the discharge probability calculated by the first discharge probability calculating portion in the first state, 2 P is the discharge probability calculated by the first discharge probability calculating portion in the second state, T is the pulse width of the drive pulse voltage in the first and second states, and P bA is the discharge probability of the irregular discharge.

3. A discharge probability calculating method of a light detection system 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 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 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 a turning-on/turning-off state of the second light source is different from that of the first state and a pulse width of the drive pulse voltage is the same as 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 known sensitivity parameters of the optical sensor, a reference pulse width of the drive pulse voltage, a reference received light quantity received by the optical sensor, a discharge probability of a regular discharge when the pulse width of the drive p

Assignees

• Azbil Corp

Inventors

• Onuma Shun
• Mori Raita

Classifications

• H04N23/60

  Control of cameras or camera modules · CPC title

• G01S17/10

  using transmission of interrupted, pulse-modulated waves (determination of distance by phase measurements G01S17/32) · CPC title

• G01S7/497

  Means for monitoring or calibrating · CPC title

• G01J2001/4242

  Modulated light, e.g. for synchronizing source and detector circuit · CPC title

• G01J2001/4238

  Pulsed light · CPC title