JP2018152716A - Object detection sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an object detection sensor capable of adjusting a boundary distance with higher resolution than resolution of a circuit being used.SOLUTION: The object detection sensor includes: a DCVGA for amplifying an analog signal representing intensity of a reception signal to a sensor element; a determination unit for determining presence or absence of a detection object by comparing an output of DCVGA with a threshold value; and an adjustment unit that performs adjustment processing, for adjusting a gain of the DCVGA and the threshold so that a boundary distance at which a determination result of the presence or absence of the detection target by the determination unit is switched is a set distance of a user, obtaining a gain with which the boundary distance becomes the set distance by assuming that the DCVGA is a DCVGA with higher resolution, adjusting to a maximum gain settable to a DCVGA equal to or less than the obtained DCVGA gain, and adjusting to a result of multiplication of a value obtained by dividing a threshold value to be used by the determination unit with the gain obtained after DCVGA adjustment and a reference threshold value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an object detection sensor that determines the presence or absence of an object in a detection region.

  Various sensors such as a photoelectric sensor, a magnetic sensor, a radio wave sensor, a capacitance sensor, and an ultrasonic sensor are used as the object detection sensor. As an example, in the photoelectric sensor, the intensity of the reflected light from the detection target of the light from the light emitting element is measured by the light receiving element, and the measured intensity is amplified by the variable gain amplifier and compared with the threshold value. A device for determining whether or not a detection object exists near an ON / OFF set distance designated by a user is known (for example, see Patent Document 1).

JP 2002-171162 A

  As the object detection sensor as described above, one that adjusts the drive amount (drive current or drive voltage) of the drive element with a digital analog converter (DAC) and amplifies the output of the sensor element with a digital control variable gain amplifier (DCVGA). Are known. Such an object detection sensor can adjust the distance (hereinafter referred to as a boundary distance) at which the determination result of the presence or absence of the detection object is switched with higher accuracy as the resolution of the DAC and DCVGA used is higher. It will be a thing. However, the circuit scale of a DAC or DCVGA having a desired output range increases as the resolution increases. And if the circuit scale of DAC or DCVGA becomes large, it will become difficult to make the control system of a drive element and a sensor element compact. Therefore, a sensor circuit that can adjust the boundary distance satisfactorily with an analog circuit (DAC, DCVGA) having a relatively low resolution is desired.

  Therefore, an object of the present invention is to provide an object detection sensor capable of adjusting the boundary distance with higher resolution than the resolution of the analog circuit (DAC, DCVGA) used.

  In order to solve the above problems, an object detection sensor according to a first aspect of the present invention includes a sensor element and an amplifier that is a digitally controlled variable gain amplifier that amplifies an analog signal representing the intensity of a received signal of the sensor element. The determination unit that determines the presence / absence of the detection target by comparing the output of the amplifier and the threshold value, and the boundary distance at which the determination result of the presence / absence of the detection target by the determination unit switches is set by the user And an adjustment unit that performs an adjustment process for adjusting the gain of the amplifier and the threshold value so that the ON / OFF set distance is obtained. Then, the adjustment unit of the object detection sensor according to the first aspect of the present invention assumes that the amplifier is a digitally controlled variable gain amplifier with higher resolution as the adjustment process, and the boundary distance is set to the ON / OFF setting. The gain of the amplifier as a distance is obtained, the gain of the amplifier is adjusted to the largest gain that can be set in the amplifier that is equal to or less than the obtained gain, and the threshold value is adjusted to the gain after the adjustment of the amplifier. A process of adjusting the value obtained by dividing the obtained gain by the threshold value at the start of the adjustment process is performed.

That is, in the object detection sensor according to the first aspect of the present invention, the digitally controlled variable gain amplifier (hereinafter also referred to as DCVGA) has a higher resolution than that actually used.
Assuming that it is CVGA, a gain is obtained in which the boundary distance becomes the ON / OFF set distance when used in combination with the reference threshold value. Next, the gain of the DCVGA is adjusted to the largest gain that can be set in the DCVGA equal to or less than the obtained gain, and the threshold value is decreased to compensate for the shortage of gain.

  As such, even if the gain and threshold value are adjusted / changed, the boundary distance and the ON / OFF set distance remain the same. According to the above procedure, the adjustment accuracy of the boundary distance is not limited by the resolution of the analog circuit (DCVGA) used. Therefore, according to the object detection sensor of the first aspect of the present invention, the boundary distance can be adjusted with higher resolution than the resolution of the analog circuit, because the adjustment accuracy of the boundary distance is not limited by the resolution of the analog circuit.

  The object detection sensor according to the second aspect of the present invention receives a response signal from a detection element of a drive element, a DA converter for adjusting the drive amount of the drive element, and an output signal of the drive element. A sensor element, an amplifier that amplifies an analog signal representing the intensity of a response signal received by the sensor element, a determination unit that determines the presence or absence of the detection object by comparing the output of the amplifier and a threshold value; An adjustment unit that controls the DA converter and adjusts the threshold value so that a boundary distance at which the determination result of the presence / absence of the detection target by the determination unit is switched becomes an ON / OFF set distance; . The adjustment unit of the object detection sensor according to the second aspect of the present invention assumes that the DA converter is a DA converter with higher resolution as the adjustment process, and the boundary distance is the ON / OFF set distance. The drive amount of the drive element is obtained, the DA converter is controlled so that the drive amount of the drive element is the largest drive amount not more than the obtained drive amount, and the threshold value is adjusted after the adjustment of the DA converter. A process for adjusting the value obtained by dividing the drive amount by the calculated drive amount and the result of multiplying the threshold value at the start of the adjustment process is performed.

  That is, in the object detection sensor according to the second aspect of the present invention, assuming that the DA converter is a DA converter having a higher resolution than that actually used, the boundary distance is the ON / OFF set distance. The drive amount (usually drive voltage or drive current) of the drive element is obtained. Thereafter, the DA converter is controlled so that the drive amount of the drive element becomes the largest drive amount equal to or less than the obtained drive amount. Then, in order to compensate for the shortage of drive amount (shortage of light emission intensity), the threshold value that the determination unit compares with the output of the amplifier is changed (decreased).

  As such, even when the drive current and the threshold value are adjusted / changed, the boundary distance and the ON / OFF set distance remain the same. And according to the said procedure, the adjustment precision of a boundary distance is not restrict | limited by the resolution of the analog circuit (DA converter) used. Therefore, even with the object detection sensor according to the second aspect of the present invention, the boundary distance can be adjusted with higher resolution than the resolution of the analog circuit, because the adjustment accuracy of the boundary distance is not limited by the resolution of the analog circuit.

  The object detection sensor according to the first aspect of the present invention further includes a driving element and a DA converter for adjusting a driving amount of the driving element, and the sensor element is a detection target of an output signal of the driving element. The drive element that receives a response signal from an object, and the adjustment unit assumes that the adjustment process and the DA converter is a DA converter with higher resolution, and the boundary distance is the ON / OFF set distance And the DA converter is controlled so that the drive amount of the drive element is the largest drive amount equal to or less than the determined drive amount, and the threshold value is adjusted to the drive after the DA converter is adjusted. A configuration may be employed in which a value obtained by dividing the amount by the obtained drive amount and a drive amount / threshold adjustment process for adjusting to the multiplication result of the threshold value at the start of processing may be executed. By adopting such a configuration, an object detection sensor that functions as the object detection sensor of the first and second aspects of the present invention can be obtained.

  An object detection sensor according to a third aspect of the present invention includes a drive element, a DA converter for adjusting a drive amount of the drive element, and a sensor element that receives a response signal from a detection target of an output signal of the drive element And an amplifier that is a digitally controlled variable gain amplifier that amplifies an analog signal representing the intensity of the response signal received by the sensor element, and the presence or absence of the detection object is compared by comparing the output of the amplifier with a threshold value. The DA converter is controlled and the gain of the amplifier and the threshold are set such that a boundary distance at which a determination unit and a determination result of the presence / absence of the detection target by the determination unit are switched is an ON / OFF set distance. An adjustment unit that performs an adjustment process for adjusting the value. In the adjustment unit of the object detection sensor according to the third aspect of the present invention, as the adjustment process, the amplifier is a digitally controlled variable gain amplifier with higher resolution, and the DA converter is a DA converter with higher resolution. Assuming that the combination of the drive amount of the drive element, the gain of the amplifier, and the threshold value, where the boundary distance is the ON / OFF set distance, is obtained, and the drive amount of the drive element is in the obtained combination The DA converter is controlled so that the maximum drive amount is less than or equal to the drive amount, and the gain of the amplifier is adjusted to the largest gain that can be set for the amplifier that is less than or equal to the gain in the obtained combination. The threshold value that the unit compares with the output of the amplifier is a value obtained by dividing the adjusted gain of the amplifier by the gain in the obtained combination and the driving element The drive amount of Retighten performs processing for adjusting the multiplication result of the threshold in the combination determined above and divided by the driving amount in the combination determined above.

  According to the object detection sensor of the third aspect of the present invention, similarly to the object detection sensor of the first aspect of the present invention including the adjustment unit capable of executing the adjustment process and the drive amount / threshold value adjustment process. It is possible to prevent the adjustment accuracy of the boundary distance from being limited by the resolution of the two analog circuits (DA converter and DCVGA) used.

  Various elements can be used as the drive element and the sensor element in the object detection sensor of each aspect of the present invention. For example, the object detection sensor of each aspect of the present invention can be realized as a device in which the driving element is a light emitting element and the driving element is a light receiving element, that is, a photoelectric sensor. Note that when the object detection sensor of each aspect of the present invention is realized as a photoelectric sensor, a lens or the like for narrowing the beam direction of light from the light emitting element may be provided.

  As the determination unit in the object detection sensor of each aspect of the present invention, various types having different specific configurations can be employed. For example, a unit including an AD converter that digitizes the output of the digitally controlled variable gain amplifier and a digital comparator that compares the output of the AD converter with the threshold value can be employed as the determination unit.

  Further, based on information received from an external device or user interface means for causing the object detection sensor of each aspect of the present invention to set the ON / OFF set distance to the user, the value of the ON / OFF set distance is set. Setting distance changing means to be changed may be added.

  Even if the adjustment unit in the object detection sensor of each aspect of the present invention periodically performs the adjustment process, the adjustment unit performs the adjustment process when a predetermined adjustment command signal is input from an external device. There may be.

  Further, the drive amount / threshold adjustment processing in the object detection sensor according to the first aspect of the present invention takes into account the state of the drive element-related element in the object detection sensor that affects the output signal strength of the drive element. It is also possible to perform this process. When the drive amount / threshold adjustment process is such a process, in order to automatically correct the change in the output signal intensity of the drive element, the drive element-related element is used as the adjustment unit. It is also possible to employ one that performs the drive amount / threshold value adjustment processing when the index value of the state changes by a predetermined amount or more.

  The adjustment process in the object detection sensor according to each aspect of the present invention may be a process performed in consideration of the state of the component in the object detection sensor that affects the output intensity of the amplifier. When the adjustment process is such a process, in order to automatically correct the change in the output intensity of the amplifier, as an adjustment unit, the index value of the state of the component is a predetermined amount or more. A device that performs the adjustment process when it changes may be adopted.

  ADVANTAGE OF THE INVENTION According to this invention, the object detection sensor which can determine the presence or absence of a detection target with resolution higher than the resolution of the analog circuit (DAC, DCVGA) currently used can be provided.

FIG. 1 is a schematic configuration diagram of an object detection sensor according to the first embodiment of the present invention. FIG. 2 is a diagram illustrating the configuration and functions of the object detection sensor according to the first embodiment. FIG. 3 is a flowchart of adjustment processing executed by the control unit of the object detection sensor according to the first embodiment. FIG. 4 is a flowchart of the adjustment process executed by the control unit of the object detection sensor according to the second embodiment of the present invention. FIG. 5 is a flowchart of the adjustment process executed by the control unit of the object detection sensor according to the third embodiment of the present invention. FIG. 6 is a flowchart of the drive amount / threshold adjustment processing executed by the control unit of the object detection sensor according to the fourth embodiment of the present invention. FIG. 7 is a flowchart of gain / threshold adjustment processing executed by the control unit of the object detection sensor according to the fourth embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the structure of embodiment described below is an illustration and this invention is not limited to the structure of embodiment.

<< First Embodiment >>
First, an outline of the object detection sensor according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic configuration diagram of the object detection sensor according to the first embodiment of the present invention, and FIG. 2 is an explanatory diagram of the function and configuration of the object detection sensor.

  As shown in FIG. 1, the object detection sensor includes a light emitting unit 11, a drive circuit 12, a light receiving unit 13, a digital control variable gain amplifier (DCVGA) 14, a digital / analog converter (DAC) 15, a determination unit 16, and a control. The part 18 is provided.

  The drive circuit 12 is a digital / analog converter (DAC) that outputs a current having a magnitude corresponding to a light emission intensity designation value of M1 (for example, 8) bits input from the control unit 18. The light emitting unit 11 is a unit that outputs light having an intensity corresponding to the current from the drive circuit 12. The light emitting unit 11 includes, for example, a light emitting element such as a light emitting diode or a laser diode, and a circuit (transistor or the like) for causing a driving current corresponding to the current from the driving circuit 12 to flow through the light emitting element.

  The light receiving unit 13 is a unit that outputs an analog voltage signal corresponding to the incident light intensity. The light receiving unit 13 includes, for example, a light receiving element such as a photodiode and a circuit that converts an output current of the light receiving element into a voltage. As schematically shown in FIG. 2, the light emitting unit 11 and the light receiving unit 13 of the object detection sensor allow light reflected from the detection target of the light emitted from the light emitting unit 11 to enter the light receiving unit 13. Is arranged.

  The DCVGA 14 (FIG. 1) is a resistance string type or ladder resistance type VGA in which a gain can be set (selected) with a gain control signal of M2 (for example, 4) bits. The DCVGA 14 receives an analog voltage from the light receiving unit 13 and an M2-bit gain designation value from the control unit 18 as an amplification target and a gain control signal, respectively. Hereinafter, the minimum gain of the DCVGA 14 in dB is expressed as a [dB], and the gain step of the DCVGA 14 is expressed as b [dB].

  The DAC 15 is a unit that converts the output of the DCVGA 14 into an N-bit digital signal. Note that N of the object detection sensor according to the present embodiment is a value (for example, 8) larger than M2.

  The determination unit 16 compares the output of the DAC 15 with an N-bit threshold value from the control unit 18, and indicates an ON / OFF signal indicating whether the output of the DAC 15 is equal to or higher than the threshold value (in FIG. The result is a digital comparator.

  The control unit 18 performs adjustment processing (details will be described later), processing for turning on / off an LED (not shown) connected to the control unit 18 according to the determination result from the determination unit 16, and determination from the determination unit 16. This unit performs processing for outputting a signal representing the result to an external device. The control unit 18 includes a processor (microprocessor, CPU, etc.) and its peripheral circuits.

  Hereinafter, the function of the control unit 18 will be specifically described.

  The controller 18 receives setting / operation state information including the operation state information of the light emitting system, the operation state information of the light receiving system, and the ON / OFF set distance.

  Here, the operation state information of the light emitting system is information indicating the state of a component that affects the light emission intensity of the light emitting element, such as the temperature of the light emitting unit 11 or the drive circuit 12. Similarly, the operation state information of the light receiving system is information indicating the state of the component that affects the output signal intensity of the light receiving unit 13 such as the temperature of the light receiving unit 13 and the DCVGA 14. These pieces of information are input to the control unit 18 from a temperature sensor or the like disposed in the object detection sensor (such as in the light emitting unit 11).

  The ON / OFF set distance (see FIG. 2) is information inputted (set) by the user as the maximum distance to the detection target determined by the determination unit 16 that the detection target exists. The configuration for inputting (setting) the ON / OFF set distance by the user is not particularly limited. For example, a variable resistor that can be operated by the user may be provided in the housing of the object detection sensor, and a value corresponding to the resistance value of the variable resistor may be used as the ON / OFF set distance. Further, the control unit 18 is configured to change the value of the ON / OFF set distance based on the information received from the external device (for example, the ON / OFF set distance itself or the ON / OFF set distance change amount). You can keep it.

  The adjustment processing performed by the control unit 18 is based on the setting / operation state information, and the maximum distance to the detection target (hereinafter referred to as a boundary distance) determined by the determination unit 16 that the detection target is present and ON / OFF setting. This is a process of adjusting the light emission intensity designation value, the gain designation value, and the threshold value so that the distance becomes equal.

In order to be able to adjust the boundary distance with an accuracy equal to or higher than the resolution (gain step) of the DCVGA 14, the control unit 18 is configured (programmed) to perform the adjustment process of the procedure shown in FIG. Even if the specified emission intensity value is kept constant, the intensity of light emitted from the light emitting element changes when the temperature of the light emitting element in the light emitting section 11 changes. The intensity of light emitted from the light emitting element also changes due to deterioration with time of the light emitting element. Similarly, even if the intensity of incident light on the light receiving element in the light receiving unit 13 is constant, the voltage output from the light receiving unit 13 varies depending on the temperature of the light receiving element and deterioration with time. When such a phenomenon occurs, the boundary distance does not coincide with the ON / OFF set distance. Therefore, the control unit 18 is also configured to perform the adjustment process periodically (in other words, to perform the adjustment process even if the ON / OFF set distance is not changed by the user).

As shown in FIG. 3, the control unit 18 that has started this adjustment processing first assumes that the DCVGA 14 is an N-bit DCVGA with higher resolution, and based on the setting / operation state information, the boundary distance A combination of a light emission intensity designation value, a gain designation value, and a threshold value that can be matched with the ON / OFF set distance is obtained (step S101). Here, “N-bit DCVGA with higher resolution” means an N-bit DCVGA whose minimum gain is equal to the minimum gain a of DCVGA14 and whose gain step is 2 ^M2−N times the gain step b of DCVGA14. DCVGA (hereinafter referred to as virtual VGA).

  In this step S101, in addition to the above-mentioned condition that “the boundary distance and the ON / OFF set distance match”, in general, “the threshold value is determined in advance as a range near the upper limit of the input range of the DAC 15. Processing for obtaining a combination of a light emission intensity designation value, a gain designation value, and a threshold value that satisfies the condition “becomes a value within the threshold range” is performed.

  The content (procedure) of the process of step S101 is not particularly limited. For example, the following process can be adopted as the process of step S101.

(1) It is specified which ON / OFF set distance belongs to a predetermined ON / OFF set distance section.
(2) Taking into account the amount of change in light emission intensity of the light emitting element due to temperature change and deterioration over time estimated from the operating state information of the light emitting system, the light emission intensity of the light emitting element falls within the specified ON / OFF set distance category. The specified emission intensity is determined so that it is closest to the associated intensity.
(3) The voltage output from the light receiving unit 13 when the detection target is located at a location separated from the object detection sensor by the ON / OFF set distance under the situation where the determined emission intensity designation value is used, Calculation taking into account the amount of change in output estimated from the operating state information of the light receiving system.
(4) A gain capable of amplifying the calculated voltage to a value within the above-described threshold range is selected from gains that can be taken by the virtual VGA, and an N-bit gain control signal corresponding to the selected gain is designated as a gain. Value.
(5) A voltage obtained by amplifying the calculated voltage with the selected gain is set as a threshold value.

  Hereinafter, the emission intensity designation value, gain designation value, and threshold value in the combination obtained in the process of step S101 are referred to as temporary emission intensity designation value, provisional gain designation value, and provisional threshold value, respectively.

After completing the process in step S101, the control unit 18 calculates a compensation gain that is a gain represented by the lower (N-M2) bits of the provisional gain designation value (step S102). More specifically, if the numerical value · b · 2 ^M2-N represented by the low-order (N-M2) bits of the provisional gain specification value is expressed as X, the control unit 18 uses 10 ^{X / 20} as the compensation gain. calculate. As already described, b is the gain step of the DCVGA 14 in dB units, and b · 2 ^M2-N is the gain step of the virtual VGA in dB units.

In subsequent step S103, the control unit 18 performs the following processing.
The emission intensity designation value output to the drive circuit 12 is set as the temporary emission intensity designation value.
The gain designation value output to the DCVGA 14 is the upper M2 bit of the temporary gain designation value.
The threshold value output to the determination unit 16 is “provisional threshold value / compensation gain” (more precisely, a value obtained by converting the multiplication result of the provisional threshold compensation gain into N bits). .

  And the control part 18 complete | finishes this adjustment process.

  Hereinafter, the reason why the boundary distance can be matched with the ON / OFF set distance by the adjustment processing described above will be described.

The intensity of light incident on the light receiving element in the light receiving unit 13 of the object detection sensor is proportional to the light emission intensity of the light emitting element in the light emitting unit 11 and inversely proportional to the square of the distance to the detection target. The light emission intensity of the light emitting element is substantially proportional to the drive current of the light emitting element (current flowing through the light emitting element). Therefore, when the distance to the detection object matches the ON / OFF set distance L _th , the voltage V _out output from the DCVGA 14 is proportional to the proportional coefficient β, the driving current T of the light emitting element, and the gain G of the DCVGA 14. Can be expressed as follows.

The value of the threshold _{V th} is, if the voltage _{V out,} the boundary distance and ON / OFF setting distance _{L th} match. Therefore, in order to match the boundary distance and ON / OFF setting distance L _th, it is sufficient as shown in (2) is established or less.

When the DCVGA 14 is a virtual VGA (N-bit DCVGA), the provisional emission intensity designation value, provisional gain designation value, and provisional threshold obtained in the process of step S101 are used as the emission intensity designation value and gain designation. The value (2) is satisfied by using the value and the threshold value. However, the DCVGA 14 is a DCVGA of M2 (<N) bits. Therefore, the temporary gain specification value cannot be used as the gain specification value of the DCVGA 14 as it is. However, the gain G represented by the provisional gain designation value, the gain G ₁ represented by the upper M2 bit of the provisional gain designation value, the gain for compensation (the gain represented by the lower (N−M2) bit of the provisional gain designation value) ) is between _{G 2,} the following relationship.
G = G ₁・ G ₂

  If G is deleted from the equation (2) using this relationship, the following equation (3) can be obtained.

Then, (3) the G ₂ of the right side of the equation, when transposed to the left side, the following equation (4) can be obtained.

The (4) the right side of the equation, the gain of DCVGA14, the drive current of the light emitting element, respectively, and the G1, T, if the distance to the detection target is consistent with the ON / OFF setting distance _{L th,} This is a voltage output from the DCVGA 14. Therefore, even if the gain of DCVGA 14 is gain G ₁ and the threshold value is “V _th / G ₂ ” (the left side of expression (4)), equation (4) indicates the boundary distance and the ON / OFF set distance. Means match.

Then, the process of step S102 and S103, the gain of DCVGA14, the gain _{G 1,} the threshold _is a process that the _"V th / _{G 2".} Therefore, the boundary distance matches the ON / OFF set distance by the adjustment process described above.

  As described above, the photoelectric sensor according to the present embodiment has a configuration in which the M2 bit DCVGA 14 is treated as a DCVGA of N bits (the number of bits of the provisional gain designation value) and the boundary distance is adjusted. . Therefore, according to the photoelectric sensor according to the present embodiment, the boundary distance can be adjusted with higher resolution than the resolution of the DCVGA 14 because the adjustment accuracy of the boundary distance is not limited by the resolution of the DCVGA 14.

<< Second Embodiment >>
Hereinafter, the configuration and function of the photoelectric sensor according to the second embodiment of the present invention will be described with a focus on differences from the photoelectric sensor according to the first embodiment described above. In the description of the present embodiment and the photoelectric sensors according to the third and fourth embodiments described later, the photoelectric sensor according to the Kth (K = 1 to 4) embodiment is also referred to as a Kth photoelectric sensor. .

  Similarly to the first photoelectric sensor (FIG. 1), the second photoelectric sensor is a device including the light emitting unit 11, the drive circuit 12, the light receiving unit 13, the DCVGA 14, the ADC 15, the determination unit 16, and the control unit 18. However, in the second photoelectric sensor, M2 matches N. That is, the N-bit DCVGA 14 is used for the second photoelectric sensor. And the control part 18 of a 2nd photoelectric sensor performs the process of the procedure shown in FIG. 4 as an adjustment process.

That is, the control unit 18 that has started the adjustment process first assumes that the DAC 12 is an M3 (> M1) bit DAC with higher resolution, and sets the boundary distance to ON / OFF based on the setting / operation state information. A combination of a drive current value, a gain designation value, and a threshold value that can be matched with the OFF set distance is obtained (step S201). Here, “M3 bit DAC having higher resolution” means that the minimum output change amount (output change amount per 1 LSB) that can convert an M3 bit digital signal into an analog signal is 2 of the minimum output change amount of the DCVGA 14. It is a DAC that is ^M2−M3 times (hereinafter referred to as a virtual DAC).

  In the process of step S201, essentially the same process as the process of step S101 described above is performed except that the drive current value is obtained. Hereinafter, the drive current value, gain specified value, and threshold value in the combination obtained in the process of step S201 are referred to as a temporary drive current value, temporary gain specified value, and temporary threshold value, respectively.

  After completing the process in step S201, the control unit 18 specifies an actual drive current value that is the largest drive current value that is not more than the temporary drive current value that can be realized by the control of the DCA 12 (step S202). In step S202, the control unit 18 also performs a process of calculating a drive current ratio by dividing the actual drive current value by the temporary drive current value.

In subsequent step S203, the control unit 18 performs the following processing.
The emission intensity designation value output to the drive circuit 12 is an emission intensity designation value at which the magnitude of the drive current becomes the actual drive current value.
The gain specification value output to the DAC 12 is set as a temporary gain specification value.
The threshold value output to the determination unit 16 is “temporary threshold value / drive current ratio” (more precisely, a value obtained by multiplying the result of multiplication by the drive current ratio of the temporary threshold value into N bits). .

  And the control part 18 complete | finishes this adjustment process.

  Hereinafter, the reason why the boundary distance can be matched with the ON / OFF set distance by the adjustment processing described above will be described.

Each value obtained in the process of step S201 is expressed by the above equation (2) if the temporary drive current value is expressed as T, the gain corresponding to the temporary gain designation value is expressed as G, and the temporary threshold value is expressed as _Vth. It will be a value. Then, by modifying the equation (2) using the actual drive current value Ta and the drive current ratio k (= T / Ta), the following equation (5) can be obtained.

  Then, when k on the right side of the equation (5) is transferred to the left side, the following equation (6) can be obtained.

In the equation (6), when the equation (2) is established between G, T, and Vth, the drive current value is set to the actual drive current value Ta, and the threshold value is set to “V _th / k”. This means that the boundary distance matches the ON / OFF set distance.

The adjustment process (FIG. 4) is a process for setting the drive current value to the actual drive current value Ta and setting the threshold value to “V _th / k”. Therefore, if the adjustment process described above is executed, the boundary distance matches the ON / OFF set distance.

  As described above, the photoelectric sensor according to the present embodiment has a configuration in which the M2 bit DAC 12 is handled as an M3 bit DAC and the boundary distance is adjusted. Therefore, according to the photoelectric sensor according to the present embodiment, the boundary distance can be adjusted with a resolution higher than the resolution of the DAC 12 because the adjustment accuracy of the boundary distance is not limited by the resolution of the DAC 12.

<< Third Embodiment >>
Hereinafter, the configuration and function of the photoelectric sensor according to the third embodiment of the present invention will be described focusing on differences from the photoelectric sensor according to the first and second embodiments described above.

  The third photoelectric sensor is a device having the same configuration as the first photoelectric sensor (FIG. 1).

  However, the control part 18 of a 3rd photoelectric sensor performs the process of the procedure shown in FIG. 5 as an adjustment process.

That is, the control unit 18 that has started the adjustment processing, based on the setting / operation state information, assumes a drive current value and a gain designation value that can match the boundary distance to the ON / OFF set distance based on the following assumptions: And a threshold value combination are obtained (step S301).
Assumption 1: DAC 12 is an M3 (> M1) bit DAC with higher resolution.
Assumption 2: DCVGA 14 is an N (> M2) bit DAC with higher resolution.

  Note that the M3 bit DAC with higher resolution and the N bit DCVGA with higher resolution are the above-described virtual DAC and virtual DCVGA, respectively.

  In the process of step S301, the same process as the process of step S201 described above is performed except that the number of assumption conditions is increased. Hereinafter, the drive current value, gain specified value, and threshold value in the combination obtained in the process of step S301 will be referred to as a temporary drive current value, temporary gain specified value, and temporary threshold value, respectively.

  The control unit 18 that has finished the process of step S301 identifies the actual drive current value that is the largest drive current value that is not more than the temporary drive current value that can be realized by the control of the DCA 12 (step S202). Further, in step S302, the control unit 18 represents the drive current ratio (= actual drive current value / temporary drive current value) and the compensation gain (the lower (N−M2) bit of the temporary gain designation value). (Gain) is also calculated.

In subsequent step S303, the control unit 18 performs the following processing.
The emission intensity designation value output to the drive circuit 12 is an emission intensity designation value at which the magnitude of the drive current becomes the actual drive current value.
The gain designation value output to the DCVGA 14 is the upper M2 bit of the temporary gain designation value.
The threshold value output to the determination unit 16 is a value obtained by converting “temporary threshold value / (driving current ratio / compensation gain) to N bits.

  And the control part 18 complete | finishes this adjustment process.

In other words, each value obtained in the process of step S301 can be expressed by the above equation (2) by expressing the temporary drive current value as T, the gain corresponding to the temporary gain specified value as G, and the temporary threshold value as _Vth. This is the value that will hold. The actual drive current value Ta, the drive current ratio k (= T / Ta),
The following equation (7) can be obtained by modifying equation (2) using G = G ₁ · G ₂ . G ₁ is a gain represented by the upper M2 bits of the provisional gain designation value, and G ₂ is a compensation gain.

Then, (7) a kG ₂ of the right side of the equation, when transposed to the left side, it is possible to obtain the following equation (8).

The equation (8) is, G, T, if between Vth (2) below is satisfied, the drive current value, and the actual drive current value Ta, the gain and _{G 1,} the threshold, "V _“th / (kG ₂ )” also means that the boundary distance matches the ON / OFF set distance.

Then, adjustment processing (FIG. 5) is a drive current value, and the actual drive current value Ta, the gain and _{G 1,} the threshold _is a process that the _{"V th / (kG 2)} ". Therefore, if the adjustment process described above is executed, the boundary distance matches the ON / OFF set distance.

  As described above, the photoelectric sensor according to the present embodiment treats the M1 bit DAC 12 as an M3 (> M1) bit DAC, and treats the M2 bit DCVGA 14 as an N (> N2) bit DCVGA. Thus, the boundary distance is adjusted. Therefore, according to the photoelectric sensor according to the present embodiment, the boundary distance can be adjusted with high resolution because the adjustment accuracy of the boundary distance is not limited by the resolution of the DAC 12 and the DCVGA 14.

<< 4th Embodiment >>
Hereinafter, the configuration and function of the object detection sensor according to the fourth embodiment of the present invention will be described with a focus on differences from the object detection sensor according to each of the above-described embodiments.

  The fourth object detection sensor (the object detection sensor according to the fourth embodiment) is an apparatus having the same configuration as the first object detection sensor (FIG. 1).

  However, the control unit 18 of the fourth object detection sensor is configured to periodically execute the drive amount / threshold adjustment process and the gain / threshold adjustment process.

  The drive amount / threshold adjustment process and the gain / threshold adjustment process executed by the control unit 18 of the fourth object detection sensor are processes of the procedures shown in FIGS. 6 and 7, respectively.

  That is, the control unit 18 sets the setting / operating state information on the assumption that the DAC 12 is an M3 (> M1) bit DAC with higher resolution during the driving amount / threshold adjustment processing (FIG. 6). Based on the above, a temporary drive current value that can make the boundary distance coincide with the ON / OFF set distance is obtained (step S401). As the processing of step S401, for example, the drive current value associated with the ON / OFF set distance is read from the information indicating the correspondence relationship between the ON / OFF set distance and the drive current value, and the read drive current value is converted into the read drive current value. A process for obtaining a temporary drive current value can be adopted by performing correction according to the operating state information of the light emitting system at that time.

  Next, the control unit 18 specifies an actual drive current value that is the largest drive current value equal to or less than the temporary drive current value that can be realized by the control of the DCA 12 (step S402). Further, in step S402, the control unit 18 also calculates a drive current rate (= actual drive current value / temporary drive current value).

  Thereafter, the control unit 18 sets the emission intensity designation value output to the drive circuit 12 as the emission intensity designation value at which the magnitude of the drive current becomes the actual drive current value, and the threshold value output to the determination unit 16. Is performed as “pre-adjustment threshold value / drive current ratio” (step S403). Here, the pre-adjustment threshold is a threshold at the start of the drive amount / threshold adjustment process.

  Then, the control unit 18 that has completed the process of step S403 ends the drive amount / threshold value adjustment process.

  Further, the control unit 18 uses the setting / operation state information in the gain / threshold adjustment processing (FIG. 7) based on the assumption that the DCVGA 14 is a DCVGA of N (> M2) bits with higher resolution. Based on this, a temporary gain designation value that can make the boundary distance coincide with the ON / OFF set distance is obtained (step S501). As the processing in step S501, for example, the gain designation value associated with the ON / OFF set distance is read from the information indicating the correspondence between the ON / OFF set distance and the gain designation value, and the read gain designation value is set. Then, it is possible to employ a process for obtaining a provisional gain designation value by performing correction according to the operating state information of the light receiving system at that time.

  Next, the control unit 18 calculates a compensation gain that is a gain represented by the lower (N−M2) bits of the provisional gain designation value (step S502).

  Then, the control unit 18 converts the gain designation value output to the DCVGA 14 to the upper M2 bits of the temporary gain designation value, and sets the threshold value output to the determination unit 16 as “the threshold value before adjustment / compensation”. The gain / threshold adjustment processing is terminated after the processing for setting the gain to N bits (step S503).

  As described above, the object detection sensor according to the present embodiment treats the M1 bit DAC 12 as an M3 (> M1) bit DAC and adjusts the boundary distance, and the M2 bit DCVGA 14 includes N (> M2) It is handled as a bit DCVGA and has a function of adjusting the boundary distance. Therefore, the boundary distance can be adjusted with high resolution also by the object detection sensor according to the present embodiment.

<Deformation>
The object detection sensor according to each of the embodiments described above can be variously modified. For example, the portion composed of the ADC 15 and the determination unit 16 can be replaced with an analog comparator and a digital / analog converter (DAC) for generating a determination threshold voltage of the analog comparator. The object detection sensor according to the first to third embodiments is adjusted when an ON / OFF set distance is changed or when a predetermined adjustment command signal (information) is input from an external device. It may be modified to perform processing or to perform adjustment processing when the operating state information of the light emitting system or the light receiving system changes by a predetermined amount or more. The object detection sensor according to the fourth embodiment performs drive amount / threshold adjustment processing when the operating state information of the light emitting system changes by a predetermined amount or more, and the operating state information of the light receiving system changes by a predetermined amount or more. The device changes to a device that performs gain / threshold adjustment processing, and performs either drive amount / threshold adjustment processing or gain / threshold adjustment processing when the ON / OFF set distance is changed. May be. The object detection sensor according to the fourth embodiment may be modified into a device that performs an adjustment process instructed to be executed when a signal (information) instructing the execution of each adjustment process is input from an external device.

  The adjustment process (including drive amount / threshold adjustment process, gain / threshold adjustment process) performed by the object detection sensor according to each embodiment is transformed into a process in which the operating state information of the light emitting system / light receiving system is not considered. Also good. However, the error (difference between the boundary distance and the ON / OFF set distance) may increase unless correction is made for the circuit characteristic variation of the light emitting system / light receiving system. Therefore, as the adjustment process, it is desirable to adopt a process performed in consideration of the operation state information of the light emitting system / light receiving system.

  The object detection sensor of each embodiment may be reduced to a specific circuit configuration different from that described above, or the object detection sensor of each embodiment may be modified to a sensor other than a photoelectric sensor. Of course, it ’s also possible.

DESCRIPTION OF SYMBOLS 11 Light emission part 12 Drive circuit 13 Light reception part 14 Digitally controlled variable gain amplifier (DCVGA)
15 Analog to digital converter (ADC)
16 judgment part 18 control part

Claims (14)

A sensor element;
An amplifier that is a digitally controlled variable gain amplifier that amplifies an analog signal representing the intensity of the received signal of the sensor element;
A determination unit that determines the presence or absence of a detection object by comparing the output of the amplifier and a threshold;
An adjustment process for adjusting the gain of the amplifier and the threshold value so that a boundary distance at which the determination result of the presence / absence of the detection target by the determination unit is switched is an ON / OFF set distance set by a user. An adjustment unit to perform,
With
Assuming that the adjustment process is a digitally controlled variable gain amplifier having a higher resolution, the adjustment process obtains the gain of the amplifier whose boundary distance is the ON / OFF set distance, and determines the gain of the amplifier, The maximum gain that can be set for the amplifier that is equal to or less than the obtained gain is adjusted, and the threshold value is calculated by dividing the gain after the adjustment of the amplifier by the obtained gain and the adjustment process at the start of the adjustment process. It is a process to adjust to the multiplication result of the threshold,
An object detection sensor characterized by that. A drive element; and a DA converter for adjusting the drive amount of the drive element,
The sensor element receives a response signal from the detection target of the output signal of the drive element,
The adjustment unit is
The adjustment process;
Assuming that the DA converter is a DA converter with higher resolution, the drive amount of the drive element whose boundary distance is the ON / OFF set distance is obtained, and the drive amount of the drive element is the obtained drive. The DA converter is controlled so as to be the largest driving amount equal to or less than the amount, and the threshold value is a value obtained by dividing the driving amount after adjustment of the DA converter by the obtained driving amount, and the value at the start of processing. Driving amount / threshold adjustment processing to adjust the result of threshold multiplication,
Is feasible,
The object detection sensor according to claim 1. The drive amount / threshold adjustment process is a process performed in consideration of the state of the drive element-related element in the object detection sensor, which affects the output signal intensity of the drive element.
The object detection sensor according to claim 2. 4. The object detection sensor according to claim 3, wherein the adjustment unit performs the driving amount / threshold adjustment processing when an index value of the state of the driving element-related element changes by a predetermined amount or more. . A driving element;
A DA converter for adjusting the drive amount of the drive element;
A sensor element that receives a response signal from the detection target of the output signal of the drive element;
An amplifier that amplifies an analog signal representing the intensity of the response signal received by the sensor element;
A determination unit that determines the presence or absence of the detection object by comparing the output of the amplifier and a threshold;
An adjustment unit that controls the DA converter and adjusts the threshold value so that a boundary distance at which the determination result of the presence / absence of the detection target by the determination unit is switched becomes an ON / OFF set distance; ,
With
The adjustment process assumes that the DA converter is a DA converter with higher resolution, and obtains the drive amount of the drive element where the boundary distance is the ON / OFF set distance, and the drive amount of the drive element is The DA converter is controlled to be the largest drive amount equal to or less than the determined drive amount, and the threshold value is a value obtained by dividing the adjusted drive amount of the DA converter by the determined drive amount; A process of adjusting the multiplication result of the threshold value at the start of the adjustment process;
An object detection sensor characterized by that. A driving element;
A DA converter for adjusting the drive amount of the drive element;
A sensor element that receives a response signal from the detection target of the output signal of the drive element;
An amplifier that is a digitally controlled variable gain amplifier that amplifies an analog signal representing the intensity of a response signal received by the sensor element;
A determination unit that determines the presence or absence of the detection object by comparing the output of the amplifier and a threshold;
Adjustment for controlling the DA converter and adjusting the gain of the amplifier and the threshold value so that the boundary distance at which the determination result of the presence / absence of the detection target by the determination unit is switched becomes an ON / OFF set distance An adjustment unit for processing;
With
In the adjustment process, assuming that the amplifier is a digitally controlled variable gain amplifier with higher resolution and the DA converter is a DA converter with higher resolution, the boundary distance is the ON / OFF set distance. A combination of the drive amount of the drive element, the gain of the amplifier, and the threshold value is obtained, and the DA converter is adjusted so that the drive amount of the drive element is the largest drive amount equal to or less than the drive amount in the obtained combination. And the gain of the amplifier is adjusted to the largest gain that can be set in the amplifier that is equal to or less than the gain in the obtained combination, and the threshold value that the determination unit compares with the output of the amplifier is set to the amplifier The value obtained by dividing the adjusted gain by the gain in the obtained combination and the value obtained by dividing the adjusted drive amount of the drive element by the drive amount in the obtained combination A process for adjusting the multiplication result of the threshold in the determined combination,
An object detection sensor characterized by that. The adjustment process is a process performed in consideration of the state of components in the object detection sensor that affects the output intensity of the amplifier.
The object detection sensor according to any one of claims 1 to 6, wherein: The object detection sensor according to claim 7, wherein the adjustment unit performs the adjustment process when an index value of the state of the component changes by a predetermined amount or more. The sensor element is a light receiving element, and the driving element is a light emitting element.
The object detection sensor according to claim 2, wherein the object detection sensor is a sensor. The determination unit
An AD converter for digitizing the output of the amplifier;
A digital comparator for comparing the output of the AD converter with the threshold;
The object detection sensor according to any one of claims 1 to 9, wherein the object detection sensor includes: The object detection sensor according to any one of claims 1 to 10, further comprising user interface means for allowing a user to set the ON / OFF set distance. The object detection sensor according to any one of claims 1 to 11, further comprising setting distance changing means for changing a value of the ON / OFF setting distance based on information received from an external device. The adjustment unit periodically performs the adjustment process.
The object detection sensor according to any one of claims 1 to 12, wherein: The adjustment unit performs the adjustment process when a predetermined adjustment command signal is input from an external device.
The object detection sensor according to claim 1, wherein the object detection sensor is an object detection sensor.