JP2005227018A - Object detection sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an object detection sensor capable of stable operation while preferably detecting the object without receiving affection of external light disturbance, reducing power consumption, without fluctuation of detection performance against the voltage fluctuation of a power source. <P>SOLUTION: The object detection sensor comprises a light projection means for irradiating the object with infrared rays; a light receiving means for receiving the reflected infrared rays from the irradiated object, and outputting the detection signal by photoelectrically transducing the reflected light; and a control means for controlling the light projection means and the light receiving means. Herein, the first decision interval T1 for confirming the detection pulse of the detection signal outputted by receiving the reflected light, and the object detection decision interval T8 provided successively with the first decision interval T1, and a second decision interval T28 for confirming no pulse of the detection signal by the reflected light. Thereby, the detection of the object is determined. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an object detection sensor, a light projecting means for irradiating a detected object with infrared light, a reflected light of the infrared light reflected by the detected object, and a photoelectric conversion of the reflected light. The present invention relates to an object detection sensor including a light receiving unit that outputs a detection signal of the object to be detected, a light projecting unit, and a control unit that controls the light receiving unit.

  An object detection sensor configured by combining a projector and a light receiver is used in various applications. For example, an automatic flush toilet that allows water to flow when leaving the urinal, an automatic faucet that allows water to flow from a faucet when the hand is held over, an automatic door that opens when a person approaches, or lights when entering a room It is widely used for object detection for controlling lighting devices and the like. In particular, in recent years, awareness of environmental issues has increased, and there has been a further movement toward saving labor in the use of resources such as electricity and water by control using object detection sensors.

  However, in a place where such an apparatus is used, a light source is usually present in addition to the projector of the object detection sensor. There are various light sources such as sunlight, indoor fluorescent lamps, and incandescent lamps. These sometimes enter the light receiver of the object detection sensor as disturbance light and cause the object detection sensor to react. This erroneous detection causes the controlled device to malfunction, causing unnecessary water to flow or turning on unnecessary illumination. Thus, conventionally, erroneous detection due to ambient light has been a problem for object detection sensors.

In addition, the object detection sensor needs to always detect an object continuously or intermittently depending on its application. Since the object detection sensor is electrically driven, the electric energy is consumed for the continuous operation. Therefore, it is an important issue to save power in the object detection sensor itself.
In addition, object detection sensors are often installed at a location remote from the device being controlled. For example, in an automatic door, a sensor that detects the presence of a person may be disposed above the door, and a door drive device or control device may be installed under the floor.
A battery is often used as a power source for such an object detection sensor. And since the capacity | capacitance of a battery is limited, considering maintenance, such as running out of a battery or battery replacement, power saving is important. In addition, the battery has a characteristic that its output voltage drops over time or fluctuates depending on the environment such as temperature. Therefore, it is important to save power in order to configure the object detection sensor so as to continue to operate stably over a long period of time.

In view of such a problem, there is an object detection sensor which is strong against disturbance light and has low power consumption as described in Patent Document 1 (Japanese Patent Laid-Open No. 2002-48877). In this object detection device, when the light projector is not projecting light (first light reception timing) and when it is performing light projection (second light reception timing), the light receiver is in a driving state, respectively. There has been proposed an object detection device that detects an object based on a combination of a light reception result at one light reception timing and a light reception result at a second light reception timing. Specifically, even if light is received at the second light receiving timing, if there is light received at the first light receiving timing, it is determined that there is an influence of disturbance light, and the object detection device outputs that there is no object. It is comprised as follows.
In addition, it has been proposed to reduce power consumption by providing a period in which the optical receiver is in a driving state (turning on the power) and a period in which the light receiver is not in a driving state (not turning on the power).

JP 2002-48877 A (paragraph numbers [0006] to [0010], [0041], [0055], FIGS. 4 and 5)

  However, in the configuration proposed in Patent Document 1, there is no disturbance light at the first light reception timing and no disturbance light is incident at the second light reception timing in the state where there is no object at the detection position. It will be detected. That is, it can be said that it is difficult to distinguish between regular reflected light and disturbance light only by having two kinds of light reception timings. In addition, although the power consumption can be reduced by providing a driving state and a non-driving state, a decrease in detection performance caused by a change in power supply voltage due to battery consumption during long-term use cannot be eliminated. Accordingly, it cannot be said that the sensitivity of the object detection sensor, for example, stability such as a constant detection distance is secured over a long period of time.

  In view of the above problems, the object of the present invention is to detect an object satisfactorily without being affected by ambient light, reduce power consumption, and the detection performance does not fluctuate even when the power supply voltage fluctuates. Therefore, it is an object to provide an object detection sensor capable of operating in the same manner.

[First feature configuration]
In order to achieve the above object, a first characteristic configuration according to the present invention is provided continuously with a first determination section for receiving a reflected light and confirming a pulse of a detection signal output and the first determination section. The detection of the detected object is determined by an object detection determination section including a second determination section for confirming that there is no pulse of the detection signal due to the reflected light.

[Effects of first feature configuration]
According to the first characteristic configuration of the present invention, an object detection determination section is provided in which a first determination section for obtaining a detection signal by light projection and reception and a second determination section continuous thereto are provided, and the first determination section In the second judgment section, it is confirmed that there is no pulse of the detection signal due to the reflected light from the object to be detected, and it is confirmed that there is no pulse of the detection signal due to the reflected light. Since the detection determination of the detected object is performed, an effect that an object detection sensor that can detect an object satisfactorily without being affected by disturbance light can be obtained. In addition, since the energization to the light projecting means can be stopped in the second determination section in which the infrared light is not irradiated, an effect that the power consumption can be reduced is also obtained.

During the infrared light irradiation period in the first determination section, the lighting period / light-out period are mixed, not the always-on state. That is, when the detected object exists, a period in which reflected light from the irradiated infrared light exists and a period in which there is no light exist in the first determination section. If there is no reflected light, the detection signal is output in the initial state. If there is reflected light, the reflected light is received and the detection signal is output in an effective state. When the reflected light disappears again, the detection signal returns to the initial state, so that the detection signal in the valid state is output as a pulse. During the first determination interval, the presence of this pulse is confirmed, and it is also confirmed that the detection signal is in the initial state during the infrared light extinguishing period. If it is not the initial state, it can be determined that it is caused by disturbance light. In this way, the initial state and the presence of the detection pulse are confirmed in the first determination section.
In the second determination section, no infrared light is irradiated, so there is no reflected light. Therefore, if light is received during the second determination section and a pulse of the detection signal is output, it can be determined that it is caused by disturbance light. Here, if the time in the second determination section is made longer than the turn-off period in the first determination section, it is possible to increase the probability of detecting a detection signal caused by disturbance light.

[Second feature configuration]
In the second feature configuration according to the present invention, in addition to the first feature configuration described above, there are a plurality of pulses of the detection signal in the first determination section, and the detection of the detected object is determined by the arrangement of the plurality of pulses. It is in.

[Effects of the second feature configuration]
According to the second feature configuration of the present invention, in addition to the first feature configuration described above, the object is detected by having a plurality of pulses of the detection signal in the first determination section. An object detection sensor that can detect an object satisfactorily without being affected can be obtained.
By making the transition of the lighting period / extinguishing period multiple times during the infrared light irradiation period in the first judgment section, the detection signal pulse in the first judgment section is output multiple times, so that more disturbance Can be strong against light. That is, the plurality of detection signal pulses and the initial state between the pulses are confirmed during the first determination interval, and the detection signal initial state during the second determination interval is further confirmed. It becomes possible to judge. Therefore, it is possible to provide an object detection sensor that eliminates the influence of disturbance light and dramatically reduces false detections.

[Third feature configuration]
In addition to the first feature configuration and the second feature configuration described above, the third feature configuration according to the present invention includes at least one of the first judgment section and the second judgment section, and includes object detection. It is in the point which comprises the judgment area.

[Effects of third feature configuration]
According to the third feature configuration according to the present invention, in addition to the first feature configuration and the second feature configuration described above, at least one of the first determination section and the second determination section includes two or more, Since the object detection determination section is configured, it is possible to obtain an object detection sensor that can eliminate the influence of disturbance light and can detect an object satisfactorily.
For example, by providing two first judgment sections and a second judgment section between them to form the object detection judgment section, disturbance light can be detected well even if regular disturbance light exists. It is possible to judge more accurately. Therefore, it is possible to provide an object detection sensor that dramatically reduces false detections.

[Fourth feature configuration]
The fourth feature configuration according to the present invention includes a constant current control unit for keeping the intensity of infrared light irradiated by the light projecting means constant in addition to the first feature configuration to the third feature configuration described above. In the point.

[Effects of fourth feature configuration]
According to the fourth feature configuration of the present invention, in addition to the first feature configuration to the third feature configuration described above, the constant current control unit for keeping the luminous intensity of the infrared light irradiated by the light projecting means constant. Thus, even when the power supply voltage fluctuates, it is possible to keep the intensity of the infrared rays to be irradiated constant and to provide an object detection sensor that operates stably. Further, when it is desired to change the detection distance of the object detection sensor according to the application, it can be dealt with only by changing the resistance constant of the constant current control unit, and stable operation is possible even after the change.

Furthermore, in the object detection sensor according to the present invention, the light projecting unit and the light receiving unit are operated by the control means only when actual operation is required. In addition, when both the light projecting unit and the light receiving unit are inactive and the control unit is not performing processing such as determination of detection data, the control unit itself stops operation with only a minimum function. ing. For example, measures such as shifting to a sleep state in which only the timer circuit is left and the clock is stopped are taken. Therefore, the effect that low power consumption can be realized as the whole object detection sensor is also obtained.
As described above, according to the present invention, an object can be detected satisfactorily without being affected by ambient light, power consumption can be reduced, and the detection performance does not fluctuate even when the power supply voltage fluctuates. It is possible to provide an object detection sensor that can be used.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a schematic circuit configuration diagram of an object detection sensor according to the present invention. The object detection sensor 100 includes a control unit 2, a light projecting unit 3, a light receiving unit 4, and optical system parts (not shown), housing parts, and the like. And the light projection part 3 and the light-receiving part 4 are controlled by the control part 2, and a detection signal is obtained. The control unit 2 determines the obtained detection signal and detects the presence or absence of the detected object 1.

  The main component of the control unit 2 is a control device CPU1. The control device CPU1 may be composed of a logic circuit such as an ASIC, but in this embodiment, a microcomputer (hereinafter referred to as a microcomputer) is used. The main component of the light projecting unit 3 is a light emitting element LED1, and in this example, an infrared light emitting diode (hereinafter referred to as infrared LED) is used. The main component of the light receiving unit 4 is a light receiving element IC1. In this example, a photo IC including a photodiode is used as the photoelectric conversion element. The control device CPU1 controls the light emitting element LED1 and the light receiving element IC1 by signals output from the port terminals P0, P1, and P3, takes in the obtained detection signal from the port terminal P2, and determines the presence or absence of the detected object 1. Detect.

The detailed operation of each part will be described below.
When the detected object 1 is present at the detection position 10, the infrared light 5 projected from the light emitting element LED 1 controlled by a signal output from the port terminals P 0 and P 1 of the control device CPU 1 irradiates the detected object 1. To do. The projected infrared light 5 strikes the object to be detected 1 and is reflected, becomes reflected light 6 and enters the light receiving element IC1. In the case of the present embodiment, the optical system (not shown) is designed so that the reflected light is the main optical axis of the regular reflection (specular reflection) light. Of course, the optical axis may be designed so that diffusely reflected light is used according to the application of the object detection sensor, or a configuration using both is also possible. The light receiving element IC1 is driven by a signal output from the port terminal P3 of the control device CPU1 in accordance with the light receiving timing. The reflected light 6 incident on the light receiving element IC1 is photoelectrically converted by a PIN photodiode (a kind of photodiode) that is built in the light receiving element IC1 and capable of high speed operation. Thereafter, signal processing such as current-voltage conversion, amplification, and binarization by a comparator is performed, and the detection signal is output as an effective pulse (for example, a pulse in a low state). When there is no object 1 to be detected at the detection position 10, since there is no reflected light 6, the detection signal is output from the light receiving element IC1 in an invalid state (for example, a high state). The detection signal is input to the port terminal P2 of the control device CPU1, and the presence or absence of the detected object 1 is determined in the control device CPU1.

Hereinafter, the operation will be described in more detail with reference to the timing chart of FIG.
A continuous pulse signal (burst wave) shown in the waveform 21 of FIG. 2 is output from the port terminal P0 of the control device CPU1. The burst wave of the waveform 21 is preferably 33 kHz to 40 kHz, which is a frequency used for a remote control. In this embodiment, the signal is output in the period T1 with 38 kHz and a duty of 50%. In the period T2, the output is controlled to be in a low state (hereinafter referred to as an L state). Here, the period T1 is referred to as a light projection period or a first determination section, and the period T2 is referred to as a non-light projection period.

  The burst wave of the waveform 21 output from the port terminal P0 of the control device CPU1 is input to the base of the transistor TR1 via the resistor R1 that limits the base current. The transistor TR1 is a switching element that controls light projection of the light emitting element LED1 that is an infrared LED. When the burst wave of the waveform 21 is in a high state (hereinafter referred to as an H state) and a waveform 22 described later is in an L state, the transistor TR1 is turned on and the light emitting element LED1 is lit.

  The anode terminal of the light emitting element LED1 is connected to the power supply line Vcc, and the cathode terminal is connected to the collector terminal of the transistor TR1. The emitter terminal of the transistor TR1 is connected to the port terminal P1 of the control device CPU1 via a resistor R2 that controls the current flowing through the infrared LED. That is, a series path is formed from the power supply line Vcc to the light emitting element LED1, the transistor TR1, the resistor R2, and the port terminal P1 of the control device CPU1. When the transistor TR1 is on and the port terminal P1 is in the L state, a current controlled by the resistor R2 flows through the series path, and the light emitting element LED1 is lit. Even if the transistor TR1 is on, if the port P1 terminal is in the H state, no current flows and the light emitting element LED1 is not lit.

  As described above, the light projecting unit 3 is controlled by managing lighting / extinguishing of the light emitting element LED1 by the output of the port terminals P0 and P1 of the control device CPU1. A signal as shown by the waveform 22 is output from the port terminal P1 of the control unit CPU1. That is, the port terminal P1 is in the L state active state during each of the periods T3, T5, and T7 provided during the light projection period (first determination section) T1. This period is called an actual light projection period. The periods T4 and T6 are inactive in the H state. This period is called a light projection suspension period. In the present embodiment, the periods T3, T4, T5, T6, and T7 are each controlled by 600 μs.

  Therefore, the control device CPU1 controls the light emitting element LED1 to emit light three times with a burst wave having a frequency of about 38 kHz and a duty of 50% for 600 μs with an interval of 600 μs. A waveform 23 is a waveform showing a light projection state of the light emitting element LED1, where the light emitting element LED1 is in the H state and the light emitting element LED1 is in the L state. That is, in the periods T13, T15, and T17 that are almost simultaneously with the periods T3, T5, and T7, the infrared light 5 is pulsed toward the detection position 10 and in the periods T14 and T16 that are almost simultaneously with the periods T4 and T6. Is not irradiated with infrared light 5.

  The light emitting diode emits light by passing a forward current. In addition, the intensity of light to be irradiated is determined by the magnitude of the forward current. When the forward current increases, the intensity of the irradiated infrared light also increases. Conversely, when the forward current decreases, the intensity decreases. The resistor R2 is a resistor for determining a forward current that flows through the light emitting element LED1 that is an infrared LED. However, the voltage of the power supply line Vcc may fluctuate when the specification of the power supply is changed or when a battery is used as the power supply and deterioration or environmental change occurs. As a result, the forward current determined by the resistor R2 also changes accordingly. When the luminous intensity of the light emitting element LED1 changes, the luminous intensity of the reflected light 6 also changes. As a result, the light receiving sensitivity of the light receiving element IC1 is also affected. For example, the detection distance 11 at the initial stage of the design increases due to the increase in luminous intensity and reacts excessively, and conversely, the detection distance 11 contracts due to the decrease in luminous intensity and stops responding. As a result, the possibility of inducing false detection or non-detection as an object detection sensor increases.

Therefore, in this embodiment, the constant current circuit 7 is configured by using the transistor TR2 so that the forward current determined by the resistor R2 is constant without depending on the voltage change of the power supply line Vcc. The transistor TR2 keeps the base-emitter potential _VBE constant, thereby keeping the potential at both ends of the resistor R2 constant. Therefore, the forward current I flowing through the resistor R2 is kept at a constant value expressed by Equation 1. Be drunk.
I = V _BE / R2 (Formula 1)

  Thus, the forward current I can be set depending only on the resistor R2. Therefore, not only the stability of the forward current with respect to the power supply voltage is improved, but also the case where the detection distance of the object detection sensor is to be changed according to the installation location can be easily handled. Even when manufacturing object detection sensors with different detection distances as a product lineup, the basic structure can be shared. Of course, a variable resistor may be mounted and the movable part may be fixed after adjustment. In this way, since it can be configured to be flexible with respect to changes in the detection distance and to be resistant to environmental fluctuations, it is possible to broaden the usage of the object detection sensor.

  Next, the operation of the light receiving unit 4 will be described. Driving of the light receiving element IC1, which is a main component of the light receiving unit 4, is controlled by switching the transistor TR3 with an output signal from the port terminal P3 of the control device CPU1. The control method will be described later. The light receiving element IC1 includes a PIN photodiode as a photoelectric conversion element, an amplifier that amplifies the photocurrent from the photodiode by current-voltage conversion, a bandpass filter (hereinafter referred to as BPF), a demodulator, an integrator, It has an internal circuit consisting of a comparator for binary output. BPF has frequency characteristics with a center frequency of 38 kHz. From the object detection signal photoelectrically converted by the reflected light 6 of the light projected by the 38 kHz burst wave, noise components and the like are removed by the BPF and input to the integrator at the subsequent stage. After being integrated by the integrator, it is pulsed into a binarized signal at a constant threshold by the comparator and output from the light receiving element IC1.

  When the detected object 1 exists at the detection position 10, the reflected light 6 of the infrared light 5 projected in the periods T13, T15, and T17 is incident on the light receiving element IC1 and subjected to the signal processing described above. Thereafter, a pulse as shown in the waveform 24 is output. That is, the L state pulses d0, d2, and d4 output in the periods T23, T25, and T27 indicate that the detected object 1 is detected by the infrared light 5 projected in the periods T13, T15, and T17. ing. The detection signal indicated by the waveform 24 is connected to the port terminal P2 of the control device CPU1, and is in the H state in the non-detection state. The control device CPU1 knows the detection state from the state of the signal input to the port terminal P2.

On the other hand, the H state (initial state) appears at light receiving periods T24 and T26 corresponding to the light emission suspension periods T14 (T4) and T16 (T6), and before and after the light projection period T1. Including this H state, at the port terminal P2, six types of signal states d0, d1, d2, d3, d4, and d5 can be recognized as shown by the waveform 24. In the control unit CPU1, since the signal waveforms from d0 to d4 are input to the port terminal P2 in the planned H state and L state as shown by the waveform 24, normal reflected light data corresponding to the light projection signal is input. Can be determined to be detected. In this determination, the change point of each pulse may be detected at the edge, or the period of each pulse may be measured in the control unit CPU1 and determined by both the pulse shape and the period.
Here, when disturbance light such as sunlight, incandescent lamp, fluorescent lamp, etc. has been detected, the L state is detected in d1 and d3, which should be originally in the H state, and the detection is normal due to the disturbance light. It can be distinguished from data by reflected light. As a result, it is possible to exclude erroneous detection as an object detection sensor.

  A case where the period of each pulse is measured in the control unit CPU1 will be described below. The control unit CPU1 observes whether the port terminal P2 is in the H state or the L state every 10 μs, for example. For example, when the L state is detected 40 times or more, it is determined that a pulse such as d0 (d2, d4) has been output. In this embodiment, burst waves are continuously output and projected for a period of 600 μs (waveform 23). Since the time required for 40 detections is 400 μs, the output corresponding to this period can be observed well. Similarly, d1 (d3) is observed every 10 μs, and it may be determined that the H state is 40 times or more. On the contrary, if the L state is observed more than the determined number, the disturbance You may determine with the noise by light.

  More preferably, in addition to the signal waveforms from d0 to d4, if d5 is in the H state for a period of time T28 or longer, it is more resistant to noise (disturbance light), and false detection can be reduced. it can. In other words, by taking a long period of d5, even disturbance light that matches d0, d2, and d4 can be excluded due to a mismatch in d5. In order to distinguish this period T28 from the previous first determination section (corresponding to the period T1), it will be referred to as a second determination section. As an actual detection method, in the period T28 (second determination section), it may be observed that the state is in the H state similarly to the first determination section, or conversely, it may be observed that the state is not in the L state. For example, the port terminal P2 may be observed every 10 μs and the H state may be observed 80 times or more, or may be observed every 20 μs and the H state may be observed 40 times or more. The timing and period of observation can be set arbitrarily.

Thus, more reliable detection is possible by making a determination based on a plurality of signal patterns. That is, the control device CPU1 determines the detection based on the following.
1. The first determination section (period T1) and the second determination section (period T28) constitute an object detection determination section (period T8).
2. The first judgment section and the second judgment section are provided continuously.
3. The light reception data d0, d1, d2, d3, d4 at the light reception timing synchronized with the first determination section is detected in a predetermined pattern.
4). No noise component due to ambient light is detected in the second judgment interval.

Next, a drive control method for the light receiving element IC1 will be described.
The light receiving element IC1 only needs to be driven during the object detection determination section (period T8). Accordingly, the power may be turned off without driving during a period when the control unit CPU1 is performing a determination calculation or between the end of the second determination section and the next first determination section (in a period T9). Equivalent).
This control is executed by switching the transistor TR3 with the output of the port terminal P3 of the control device CPU1. That is, in the period T8 when the waveform 25 of the port terminal P3 is in the L state, the PNP junction transistor TR3 is turned on, and power is supplied from the power supply line Vcc to the light receiving element IC1. On the other hand, in the period T9 in the H state, the transistor TR3 is turned off and the supply of power is stopped. A resistor R4 in FIG. 1 is a pull-up resistor for keeping the base voltage at the level of the power supply line Vcc and surely turning off the transistor TR3 when the output of the port terminal P3 is not in the L state. The resistor R5 is a limiting resistor for limiting the base current, and the resistor R3 is a load resistor. The capacitor C1 is a bypass capacitor for stabilizing the power supply of the light receiving element IC1.

  On the other hand, the control unit CPU1 receives the output from the object detection determination section T8, the light receiving element IC1 and performs an internal process, and the period during which other internal processes are performed (the above period is combined as an operation period T12). During a period T10 (sleep period) other than (), only the internal timer is enabled and a transition is made to a dormant state (waveform 26). After the initialization process after the power supply to the control device CPU1, the sleep period T10 and the operation period T12 are repeatedly performed so that continuous object detection can be performed. The periods T10 and T12 can be arbitrarily determined depending on the detection target of the object detection sensor, the installation location, the control target, and the like. By controlling in this way, the object detection is continuously performed, and the power consumption during the non-detection period is made as close to zero as possible. As for the entire object detection sensor, in addition to the control unit CPU1, the light emitting element LED1 is turned off during the non-light projection period T2, and the light receiving element IC1 is turned off during the period T9 outside the light reception waiting period. Thus, power consumption is generated only during a necessary period, so that low power consumption can be realized.

[Another embodiment]
In the above description, in the first determination section T1, the actual light projection period (L state) by the port terminal P1 is provided three times, and object detection is determined by the signal determination pattern based on the received light signal corresponding thereto. I made it. It is also possible to increase the number of actual light projection periods and increase the detection signal patterns appearing at the port terminal P0 as d0, d1,..., D8,. By increasing the number of detection signal patterns, the probability of catching erroneous reactions due to accidental disturbance light is increased, and noise resistance can be improved. If the effective light projection period described as 600 μs is shortened and the number of times is increased, the number of detection signal patterns can be increased without affecting the total detection time.

  In this example, as a determination criterion in the object detection determination section, it is exemplified that noise components due to disturbance light are not detected in the second determination section T28 that is provided continuously to the first determination section T1. In other words, the description has been given using the signal determination pattern in which the pulse is observed at regular intervals (corresponding to d0 to d4 of the waveform 24) and then the H state (corresponding to d5 of the waveform 24) is observed for a certain period. Other patterns can be used without being limited to the above. For example, the determination pattern in the object detection determination section may be composed of two first determination sections and one second determination section. Specifically, as shown in FIG. 3, pulses at regular intervals are observed (corresponding to d0 to d2 of the waveform 30), and then the H state for a certain period is observed (corresponding to d3 of the waveform 30), and thereafter It is also possible to use a signal determination pattern that observes pulses at regular intervals (corresponding to d4, d5, and d6 of the waveform 30).

  Further, it is not necessary to limit the signal determination pattern to one type, and detection may be performed using a plurality of signal determination patterns. The light emission pulse control is performed by the control unit CPU1, and it is only necessary to use a detection signal determination pattern corresponding to the light projection pulse control. A determination pattern can be used.

  As described above, it is possible to detect an object satisfactorily without being affected by ambient light, reduce power consumption, and operate stably without fluctuation in detection performance even with respect to power supply voltage fluctuations, etc. An object detection sensor can be provided.

Schematic showing the circuit configuration of the object detection sensor of the present invention Schematic timing chart showing the circuit operation of the object detection sensor of the present invention Example of another embodiment of the object detection signal pattern of the present invention

Explanation of symbols

CPU 1 Control device LED 1 Light emitting element IC 1 Light receiving element 1 Object to be detected 2 Control unit 3 Light projecting unit 4 Light receiving unit 5 Projected infrared light 6 Reflected light 7 Constant current circuit 10 Detection position 11 Detection distance 100 Object detection sensor T1 First One judgment section T8 Object detection judgment section T28 Second judgment section

Claims (4)

A light projecting means for irradiating the detected object with infrared light;
A light receiving means for receiving reflected light of the infrared light reflected upon the object to be detected, photoelectrically converting the reflected light and outputting a detection signal of the object to be detected;
In the object detection sensor comprising the light projecting means and the control means for controlling the light receiving means,
A first determination section for receiving the reflected light and confirming a pulse of the detection signal output;
By the object detection determination section, which is provided continuously with the first determination section, and which includes a second determination section for confirming that there is no pulse of the detection signal due to the reflected light,
An object detection sensor for determining detection of the detection object. There are a plurality of pulses of the detection signal in the first determination section,
The object detection sensor according to claim 1, wherein the detection of the detection object is determined based on the arrangement of the plurality of pulses.   The object detection sensor according to claim 1 or 2, wherein at least one of the first determination section and the second determination section is included to constitute the object detection determination section.   The object detection sensor according to any one of claims 1 to 3, further comprising a constant current control unit configured to maintain a constant luminous intensity of the infrared light irradiated by the light projecting unit.

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