JP2019220812A - Photoelectronic sensor - Google Patents

Abstract

An object of the present invention is to perform temperature correction of a light emitting diode and prediction of the life of the light emitting diode without using a monitoring photodiode. A light emitting diode emitting light, a temperature / humidity sensor disposed around the light emitting diode and detecting temperature and humidity, and a temperature detected by the temperature / humidity sensor. A temperature correction unit 1052 for performing temperature correction on the light emitting diode 1011, and a life prediction unit 1053 for predicting the life of the light emitting diode 1011 based on the temperature and humidity detected by the temperature and humidity sensor 104. [Selection diagram] Fig. 1

Description

  The present invention relates to a photoelectric sensor having a light source.

  2. Description of the Related Art Conventionally, a photoelectric sensor having an APC (Automatic Power Control) function of automatically controlling the amount of projected light has been known (for example, see Patent Document 1). With this APC function, even when the light source is deteriorated due to the ambient temperature, the amount of emitted light can be controlled to be constant.

JP-A-2002-217702

  However, in the conventional photoelectric sensor having the APC function, a photodiode for monitoring the projected light amount is separately required. The monitor photodiode has a large component size, which hinders miniaturization of the photoelectric sensor. Further, the APC function can correct deterioration due to the temperature of the light source, but cannot predict the life of the light source itself.

  The present invention has been made in order to solve the above-described problems, and has as its object to provide a photoelectric sensor capable of performing light source temperature correction and light source life estimation without using a monitoring photodiode. And

  A photoelectric sensor according to the present invention includes a light source that emits light, a temperature and humidity sensor that is a MEMS sensor that is disposed around the light source and detects temperature and humidity, and a light source based on the temperature detected by the temperature and humidity sensor. And a life prediction unit for predicting the life of the light source based on the temperature and humidity detected by the temperature and humidity sensor.

  According to the present invention, since the configuration is as described above, the temperature correction of the light source and the life expectancy of the light source can be performed without using a photodiode for monitoring.

FIG. 1 is a diagram illustrating a configuration example of a photoelectric sensor according to Embodiment 1 of the present invention. FIG. 3 is a diagram illustrating a configuration example of a processing unit according to the first embodiment of the present invention. 5 is a flowchart illustrating an example of an operation of temperature correction and life estimation by a processing unit according to Embodiment 1 of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration example of a photoelectric sensor according to Embodiment 1 of the present invention.
The photoelectric sensor emits and receives light via the detection area, and performs various processes such as determining the presence or absence of an object in the detection area based on the light reception result. Hereinafter, only the configuration on the light emitting side of the configuration of the photoelectric sensor is shown. As shown in FIG. 1, the photoelectric sensor includes a light projecting unit 101, a switch 102, a reference voltage generating unit 103, a temperature and humidity sensor 104, a processing unit 105, and a notifying unit 106. The type of the photoelectric sensor is not particularly limited, and may be any of a transmission type, a reflection type, and a reflector type.

  The light emitting unit 101 emits light and emits the light to the detection area. As shown in FIG. 1, the light emitting unit 101 includes a light emitting diode (light source) 1011, a transistor 1012, and a resistor 1013.

The light emitting diode 1011 emits light. The light emitting diode 1011 has an anode connected to a constant voltage source (Vcc shown in FIG. 1).
The transistor 1012 has a collector terminal connected to the cathode of the light emitting diode 1011.
The resistor 1013 has one end connected to the emitter terminal of the transistor 1012 and the other end connected to the ground.

The reference voltage generation unit 103 amplifies the signal input from the processing unit 105.
The switch 102 connects the base terminal of the transistor 1012 to the reference voltage generator 103 or the ground.

  The temperature and humidity sensor 104 is arranged around the light emitting diode 1011 and detects temperature and humidity. The temperature and humidity sensor 104 is a MEMS (Micro Electro Mechanical Systems) sensor.

  The processing unit 105 outputs a signal to the reference voltage generation unit 103, and controls the switch 102. In addition, the processing unit 105 has a function of performing temperature correction and life expectancy for the light emitting diode 1011 based on the detection result of the temperature and humidity sensor 104. As shown in FIG. 2, the processing unit 105 includes a recording unit 1051, a temperature correction unit 1052, and a life prediction unit 1053 as a configuration for realizing the above function. The processing unit 105 is realized by a processing circuit such as a system LSI (Large Scale Integration) or a CPU (Central Processing Unit) that executes a program stored in a memory or the like.

  The recording unit 1051 records the detection result of the temperature and humidity sensor 104. Note that the recording unit 1051 is configured by a memory or the like.

  The temperature correction unit 1052 performs temperature correction on the light emitting diode 1011 based on information (temperature) recorded in the recording unit 1051. At this time, the temperature correction unit 1052 performs temperature correction on the light emitting diode 1011 by adding a correction value to a signal output to the reference voltage generation unit 103.

  The life prediction unit 1053 predicts the life of the light emitting diode 1011 based on information (temperature and humidity) recorded in the recording unit 1051. At this time, the life prediction unit 1053 predicts the life of the light emitting diode 1011 using an Eyring model.

  The notification unit 106 notifies the prediction result by the life prediction unit 1053 to the outside. At this time, the notification unit 106 may, for example, notify the lifetime predicted by the lifetime prediction unit 1053 as it is, or may notify when the lifetime becomes shorter than the threshold. Examples of the notification unit 106 include a display unit that displays information on a screen, a voice output unit that notifies information by voice, and a communication unit that transmits information to an external device.

Next, an operation example of temperature correction and life prediction by the processing unit 105 according to the first embodiment will be described with reference to FIG. Note that the temperature and humidity sensor 104 detects the temperature and humidity around the light emitting diode 1011, and the recording unit 1051 records the detection result by the temperature and humidity sensor 104.
In the operation example of the temperature correction and the life prediction by the processing unit 105 according to the first embodiment, as shown in FIG. 3, first, the temperature correction unit 1052 Temperature correction is performed on the light emitting diode 1011 (step ST1). The processing content of the temperature correction by the temperature correction unit 1052 is the same as the processing in the conventional photoelectric sensor, and the detailed description thereof will be omitted.

Further, the life prediction unit 1053 predicts the life of the light emitting diode 1011 based on the information (temperature and humidity) recorded in the recording unit 1051 (step ST2). At this time, the life prediction unit 1053 predicts the life of the light emitting diode 1011 based on the Eyring model shown in the following equation (1). In formula (1), L represents a lifetime of the light-emitting diode 1011, A represents a constant, _{E a} represents an activation energy, _{k b} represents a Boltzmann constant, T represents the temperature (absolute temperature), beta Represents a constant, and RH represents humidity (relative humidity). Note that A, E _a , k _b , and β are known. A and β can be obtained by actually measuring the lifetime while changing the temperature and the humidity after designing the photoelectric sensor.
_{L = A · exp (E a} / k b · T) · exp (β / RH) (1)

  In recent years, the miniaturization and high performance of temperature and humidity sensors have been advanced by MEMS technology. Therefore, in the photoelectric sensor according to the first embodiment, the temperature and humidity sensor 104, which is a MEMS sensor, is arranged around the light emitting diode 1011 instead of the conventional monitoring photodiode. Therefore, the photoelectric sensor according to the first embodiment can perform the temperature correction on the light emitting diode 1011 based on the detection result of the temperature and humidity sensor 104 while satisfying the demand for miniaturization.

  Further, the life of the light emitting diode varies depending on the surrounding temperature and humidity. On the other hand, in the photoelectric sensor according to the first embodiment, the temperature and humidity sensor 104, which is a MEMS sensor, is disposed around the light emitting diode 1011 as described above. Therefore, the photoelectric sensor according to the first embodiment can perform rough life estimation of the light emitting diode 1011 based on the detection result of the temperature and humidity sensor 104 in addition to the temperature correction for the light emitting diode 1011.

  Further, in the photoelectric sensor according to Embodiment 1, the mechanical life of the photoelectric sensor may be predicted using an acceleration sensor (MEMS sensor) that detects acceleration. In this case, the acceleration sensor is provided in a housing in which each part of the photoelectric sensor including the light-emitting diode 1011 is housed. The recording unit 1051 also records the detection result obtained by the acceleration sensor. Then, the life prediction unit 1053 predicts the mechanical life of the photoelectric sensor based on the information (acceleration) recorded in the recording unit 1051. For example, when the acceleration sensor is disposed around the light emitting diode 1011, the life estimation unit 1053 can predict the degree of deterioration of a solder portion or the like between the light emitting diode 1011 and the board on which the light emitting diode 1011 is mounted. Become.

  In addition, when the photoelectric sensor according to the first embodiment is incorporated in a device that has periodic vibration, the photoelectric sensor on the light receiving side is corrected using a vibration sensor (MEMS sensor) that detects vibration. You may.

  Information (temperature, humidity, acceleration, or vibration) obtained by the various MEMS sensors described above is considered to be useful in initiatives such as digital twin or cyber-physical systems that have been actively performed in recent years in the industry. Can be That is, in these approaches, it is indispensable to define a physical model that shows a behavior in accordance with reality for each device. Then, in defining the physical model, by attaching the above-mentioned MEMS sensor in advance to the photoelectric sensor that is a part of the device, it becomes possible to handle local ambient conditions of the device without using a separate sensor. It is.

  As described above, according to the first embodiment, the photoelectric sensor includes the light emitting diode 1011 that emits light and the temperature and humidity sensor 104 that is disposed around the light emitting diode 1011 and is a MEMS sensor that detects temperature and humidity. And a temperature correction unit 1052 that performs temperature correction on the light emitting diode 1011 based on the temperature detected by the temperature and humidity sensor 104, and calculates the lifetime of the light emitting diode 1011 based on the temperature and humidity detected by the temperature and humidity sensor 104. And a life prediction unit 1053 for predicting the life. Accordingly, the photoelectric sensor according to the first embodiment can perform temperature correction of the light emitting diode 1011 and life expectancy of the light emitting diode 1011 without using a monitoring photodiode.

  Note that, in the present invention, within the scope of the invention, any constituent element of the embodiment can be modified or any constituent element of the embodiment can be omitted.

101 Light Projection Unit 102 Switch 103 Reference Voltage Generation Unit 104 Temperature and Humidity Sensor 105 Processing Unit 106 Notification Unit 1011 Light Emitting Diode (Light Source)
1012 Transistor 1013 Resistance 1051 Recording unit 1052 Temperature correction unit 1053 Life expectancy unit

Claims (3)

A light source that emits light,
A temperature / humidity sensor that is a MEMS sensor that is arranged around the light source and detects temperature and humidity;
Based on the temperature detected by the temperature and humidity sensor, a temperature correction unit that performs temperature correction on the light source,
A lifetime prediction unit configured to predict the lifetime of the light source based on the temperature and humidity detected by the temperature and humidity sensor. The photoelectric sensor according to claim 1, wherein the life prediction unit predicts a life of the light source using an Eyring model. A housing in which each unit of the own device including the light source is stored,
An acceleration sensor that is arranged in the housing and is a MEMS sensor that detects acceleration;
3. The photoelectric sensor according to claim 1, wherein the life predicting unit predicts a mechanical life of the own device based on the acceleration detected by the acceleration sensor. 4.

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