JP5061319B2 - Optical phase difference detection type object detection sensor - Google Patents

Description

  The present invention relates to an optical phase difference detection type object detection sensor that is installed at one end of a detection region and detects the presence or absence of an object in the detection region.

  Sensors that detect the presence of an object such as a human body or a vehicle within a certain area include ultrasonic sensors that measure the time of reflected waves using ultrasonic waves, triangulation sensors that use light, and the amount of reflected light. And a light quantity detection sensor and an optical phase difference detection sensor.

  In the ultrasonic sensor, there is a problem that the influence by the angle change of the detected object is large, and a problem that the ultrasonic sensor is weak to the influence of the ambient temperature and the wind.

  In the light quantity detection type sensor, since the reflected light quantity is detected, there is a problem that it is vulnerable to a change in the color of the detected object.

  In the triangulation type sensor, in order to measure accurately, it is necessary to reduce the focus of light, and thus a precise optical system is required. Further, since the detection area becomes small, it is easily affected by the angle and unevenness of the detected object. Further, when detecting a wide area, a large number of optical elements are required, which is not practical from the viewpoint of scale and cost.

An optical phase difference detection sensor (for example, refer to Patent Document 1) detects a phase difference between a light projection wave and a light reception wave, and measures a distance to an object to be detected. This utilizes the fact that the phase difference is proportional to the distance to the detected object. Therefore, the optical phase difference detection sensor is strong against the influence of temperature or the like in principle, and is strong against a change in the color of the detected object. In addition, since the detection area is wide, the number of optical system elements may be small, and it is difficult to be affected by the angle and unevenness of the detected object.
JP 2005-325537 A

  However, even in the optical phase difference detection type sensor, the detection sensor S receives light when the angle α between the detection light D and the reflection surface Y of the detected object X greatly exceeds 90 ° as shown in FIG. The amount of reflected light R is zero or extremely small, and accurate object detection cannot be performed. Further, even when excessive reflected light from a mirror or the like is received, accurate object detection cannot be performed.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to accurately detect the presence or absence of an object even when the amount of reflected light received by the light receiving element is too small or too large. An object of the present invention is to provide an optical phase difference detection type object detection sensor.

  In order to solve the above-described problems, the present invention provides (1) a sensor that is installed at one end of a detection area and detects the presence or absence of an object in the detection area, and includes a predetermined number of projections generated every first period. Based on a first light projection signal including a light pulse, a first light projecting element that projects detection light toward the detection region, and first light that is received from the detection light reflected from the detection region. A light-receiving element that generates a light-receiving signal, and measures the amplitude of the first light-receiving signal for each first period, and relates to the amplitude for each second period that is a natural number multiple of the first period. An amplitude average value calculating means for calculating an average value, and an average value related to the amplitude to be calculated when the light receiving element receives reflected light from the other end of the detection region of the detection light as an amplitude reference value First storage means stored in advance and the first cycle And measuring the first phase difference between the first light projection signal and the first light reception signal, and for each third period consisting of a natural number multiple of the first period. A phase difference average value calculating means for calculating an average value relating to a phase difference; and an average relating to the first phase difference to be calculated when the light receiving element receives reflected light from the other end of the detection region of the detection light. A second storage means that stores a value in advance as a phase difference reference value, and a case where the difference between the average value related to the amplitude and the amplitude reference value is outside the first range; Determining means for determining that there is an object in the detection region when the difference between the average value relating to the phase difference of 1 and the phase difference reference value is outside the second range. An optical phase difference detection type object detection sensor is provided. .

  The present invention may further include: (2) initial setting means for automatically storing the amplitude reference value and the phase difference reference value in the first and second storage means in advance in the configuration described above. The setting means stores the average value related to the amplitude calculated by the amplitude average value calculating means in the first storage means as the amplitude reference value in accordance with an initial setting signal from the outside, and the phase difference average value An optical phase difference detection type object detection sensor characterized in that an average value related to the first phase difference calculated by a calculation means is stored in the second storage means as the phase difference reference value. It is to provide.

  Further, in the configuration (2), the present invention provides the (3) the initial setting means according to the amplitude value measured for each of the first periods, the second period, the third period, An object detection sensor of an optical phase difference detection type is provided, wherein the first range and / or the second range are automatically determined.

  In the configuration (2), the present invention provides the configuration (2) in which the initial setting means has the second cycle according to the degree of variation in the first phase difference measured for each first cycle. An object detection sensor of an optical phase difference detection type, wherein the third period, the first range and / or the second range is automatically determined. .

  Further, in the configuration (2), the present invention provides the configuration (2), wherein the initial setting means measures the first period when the amplitude value measured for the first period is within a predetermined range. The second period, the third period, the first range and / or the second range are automatically determined according to the degree of variation in the first phase difference, and otherwise The present invention provides an optical phase difference detection type object detection sensor characterized by generating an error signal.

  Further, in the present invention, in any one of the above configurations (1) to (5), (6) each of the first light projecting element and the light receiving element includes a plurality of the first light projecting signals, The first light projecting elements are respectively generated for the first light projecting elements, and the first light projecting elements sequentially project the detection light based on the first light projecting signals. The first light-receiving signal is generated for each detection light, and the amplitude average value calculating means measures the amplitude of the first light-receiving signal for each of the first periods and the second period. For each of the amplitudes, the first storage means stores in advance the amplitude reference value for the average value for each amplitude, and the phase difference average value calculation means Each of the first light projection signals for each period The first phase difference with each first received light signal is measured, and an average value for each first phase difference is calculated for each third period. The second storage means The phase difference reference value for the average value for each first phase difference is stored in advance, and the determination means determines whether any of the differences between the average value for each amplitude and the amplitude reference value is the first value. In the case of being out of the range of 1, and in the case of being out of the range of the first phase difference and the difference between the average value of each of the first phase differences and the reference value of each of the phase differences is outside the second range, An object detection sensor of an optical phase difference detection type is provided, wherein it is determined that an object is present in the detection region.

  According to the present invention, in any one of the above-described configurations (1) to (6), (7) a second light projecting element fixedly disposed in the immediate vicinity of the light receiving element, wherein the second light projecting element is predetermined for each first period. And a light projecting unit that projects reference light toward the light receiving element based on a second light projecting signal that includes a plurality of light projecting pulses that do not overlap with the first light projecting signal. The light receiving element further receives the reference light to generate a second light receiving signal, and the phase difference average value calculating means further includes the second light projecting signal and the second light emitting signal for each first period. Measuring a second phase difference from the second received light signal, calculating an average value for a subtraction value between the first phase difference and the second phase difference for each third period, and determining the determination The means is an average value related to the amplitude calculated by the amplitude average value calculating means. The difference between the amplitude reference value is outside the first range, and the difference between the average value related to the subtraction value calculated by the phase difference average value calculating unit and the phase difference reference value, which is not the case. An object of the present invention is to provide an optical phase difference detection type object detection sensor that determines that there is an object in the detection region when the difference is outside the second range.

  According to the object detection sensor of the present invention configured as described above, whether or not the difference between the average value related to the amplitude of the received light signal calculated by the amplitude average value calculating means and the amplitude reference value is within a predetermined range. Always judged. Here, the amplitude reference value is an average value to be calculated by the amplitude average value calculation means when there is no object in the detection region. Therefore, if the difference between the amplitude average value and the amplitude reference value is outside the predetermined range, it is recognized that the light receiving element is receiving excessive or too small reflected light due to some object in the detection area. , “There is an object” can be determined. That is, according to the object detection sensor of the present invention, it is possible to accurately detect the presence / absence of an object without erroneous detection even when the light receiving element receives excessive or excessive reflected light. it can.

Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings.
1 is a side view showing an example of an optical phase difference detection type object detection sensor according to the present invention, FIG. 2 is a side sectional view showing a main body of the object detection sensor of FIG. 1, and FIG. 3 is an object detection sensor of FIG. It is a bottom view which shows arrangement | positioning of the optical element in. 4 is a block diagram for showing a circuit configuration of the object detection sensor of FIG. 1, and FIG. 5 is a time chart of a light projection signal generated in the object detection sensor of FIG. FIG. 6 is a diagram for illustrating a phase difference signal generated in the object detection sensor of FIG.

[overall structure]
As shown in FIG. 1, an optical phase difference detection type object detection sensor 1 according to the present embodiment includes a base portion 2 attached to one end of a region where presence / absence of an object is to be detected, and a main body attached to the base portion 2. It is comprised from the part 3 and the translucent cover 4 which covers the main-body part 3. FIG.

  As shown in FIG. 2, the main body 3 mainly includes a frame 31, a substrate 32 attached to one side of the frame 31, and a light projecting element 33 (first light projecting element) connected on the circuit of the substrate 32. ), A light projecting element 34 (second light projecting element) and a light receiving element 35, and a light projecting lens 36 and a light receiving lens 37 held on the other side of the frame 31.

  The frame 31 has a peripheral wall 31a and a central wall 31b. The peripheral wall 31a and the central wall 31b define a light projecting chamber 31c in which the light projecting element 33 is disposed and a light receiving chamber 31d in which the light receiving element 35 and the like are disposed.

  The substrate 32 is disposed so as to close one side (the upper side in FIG. 2) of the light projecting chamber 31c and the light receiving chamber 31d. On the circuit of the substrate 32, seven light projecting elements 33 are connected so as to be accommodated in the light projecting chamber 31c. As shown in FIG. 3, the light projecting element 33 has the light projecting element 33a as a center and other six light projecting elements 33b to 33g arranged around it. The light projecting element 33 projects light (detection light) toward the detection region (lower side in FIG. 2) based on light projection signals 51 to 57 described later.

  On the circuit of the substrate 32, as shown in FIG. 2, one light projecting element 34 is connected so as to be accommodated in the light receiving chamber 31d. The light projecting element 34 projects light (reference light) based on a light projecting signal 50 described later. Since the inclined wall 31e is provided immediately before the light projecting element 34, the reference light projected from the light projecting element 34 is reflected by the inclined wall 31e and travels toward the light receiving element 35. .

  On the circuit of the substrate 32, seven light receiving elements 35 are connected so as to be accommodated in the light receiving chamber 31d. As shown in FIG. 3, the light receiving elements 35 are arranged in the same manner as the light projecting element 33, and the other six light receiving elements 35 are arranged around it. The light receiving element 35 receives the reflected light from the detection region of each detection light projected from the light projecting elements 33a to 33g and the reference light projected from the light projecting element 34, and receives the light accordingly. Generate a signal.

  The light projection lens 36 is disposed so as to close the other side (lower side in FIG. 2) of the light projection chamber 31c. The light projecting lens 36 condenses the detection light projected from the light projecting element 33 and traveling toward the detection area.

  The light receiving lens 37 is disposed so as to close the other side (lower side in FIG. 2) of the light receiving chamber 31d. The light receiving lens 37 collects reflected light of the detection light that travels from the detection region toward the light receiving element 35.

[Circuit configuration]
Next, a configuration of a detection circuit for generating each light projection signal and processing the light reception signal to detect the presence or absence of an object in the detection region will be described. Although not shown in FIGS. 1 to 3, the detection circuit is configured on the substrate 32.

  As shown in FIG. 4, the detection circuit projects light signals 51 to 57 (first light projection signals) for causing the light projecting element 33 to project detection light and the light projecting element 34 to project reference light. Based on the light projection signals 50 and 51 to 57 generated by the light projection signal generation circuit 5 and the light projection signal generation circuit 5 for generating the light projection signal 50 (second light projection signal). 34, and a drive circuit 6 for projecting reference light and detection light to the light projecting element 33.

  As shown in FIG. 5, the light projection signal generation circuit 5 generates a light projection signal 50 including a predetermined number of light projection pulses for the light projecting element 34 every period T1 (first period). The drive circuit 6 causes the light projecting element 34 to project the reference light a predetermined number of times based on the light projecting signal 50.

  In addition, the projection signal generation circuit 5 generates projection signals 51 to 57 each including a predetermined number of projection pulses for the projection elements 33a to 33g for each period T1. The projection signals 51 to 57 are generated so that the timing does not overlap with the projection signal 50. Further, the light projection signals 51 to 57 are sequentially generated so that the timings do not overlap each other. The drive circuit 6 causes each of the light projecting elements 33a to 33g to project detection light a predetermined number of times based on the light projecting signals 51 to 57.

  Further, as shown in FIG. 4, the detection circuit converts the received light signals 71 to 77 and 70 generated by the light receiving element 35 by receiving the reflected light of the detection light and the reference light into signals based on voltages, and amplifies the IV conversion circuit 7. have.

  In addition, the detection circuit performs a beat-down, the local signal generation circuit 8 that generates a local signal, the mixing circuit 9 that mixes each of the light projection signals 50 to 57 with the local signal, and the light reception signal 70 after IV conversion. And a mixing circuit 10 for mixing 77 with a local signal. The detection circuit also has a low-pass filter (LPF) 11 that passes the low-frequency component of the signal obtained by the mixing circuit 9 and a low-pass filter (LPF) 12 that passes the low-frequency component of the signal obtained by the mixing circuit 10. And have.

  The detection circuit also includes a timing adjustment circuit 13 that adjusts the timing of the signal that has passed through the LPF 11, and a comparator 14 that converts the signal that has passed through the LPF 12 into a rectangular wave.

  The local signal generation circuit 8 generates a local signal (not shown) having a period slightly shorter than the light projection signals 50 to 57 (in other words, a frequency slightly higher than the frequency of the light projection signals 50 to 57). Each of the light projection signals 50 to 57 is mixed with a local signal by the mixing circuit 9 and then passed through the LPF 11 to be the light projection signals 50a to 57a. The light projection signals 50a to 57a further pass through the timing adjustment circuit 13 to become the light projection signals 50b to 57b shown in FIG. Similarly, the received light signals 70 to 77 after IV conversion are mixed with local signals by the mixing circuit 10 and then passed through the LPF 12 to become received light signals 70 a to 77 a. The light reception signals 70a to 77a further pass through the comparator 14 to become light reception signals 70b to 77b shown in FIG.

  Further, the detection circuit compares the light projection signals 50b to 57b and the light reception signals 70b to 77b, respectively, and obtains phase difference pulse signals φ0 to φ7 related to the phase difference between the phase comparator 15 and the phase comparator 15 And an integrating circuit 16 that integrates the phase difference pulse signals φ0 to φ7 to obtain the phase difference signals pp0 to pp7 and the phase difference voltage values P0 to P7.

  As shown in FIG. 6A, the phase comparator 15 compares the light projection signal 50b and the light reception signal 70b, and generates a phase difference pulse signal φ0 related to the phase difference (second phase difference) for each period T1. Similarly, as shown in FIG. 6B, the phase comparator 15 sequentially compares the light projection signals 51b to 57b and the light reception signals 71b to 77b, and a phase difference pulse signal φ1 related to the phase difference (first phase difference). .About..phi.7 is generated every period T1.

  As shown in FIG. 6, the integration circuit 16 integrates the phase difference pulse signals φ0 to φ7 and generates phase difference signals pp0 to pp7 every period T1, thereby obtaining phase difference voltage values P0 to P7.

  The detection circuit further cuts the direct current components of the light reception signals 70 a to 77 a from the LPF 12 to obtain the light reception signals 70 c to 77 c, and the positions from the light reception signals 70 c to 77 c from the HPF 17 and the integration circuit 16. CPU 18 to which phase difference voltage values P0 to P7 are input.

  As shown in FIG. 4B, the CPU 18 calculates an average value related to the amplitudes of the received light signals 71c to 77c based on the received light signals 71c to 77c from the HPF 17, and the phase difference voltage values P0 to P7. The phase difference average value calculation unit 18b for calculating the average value regarding the phase difference between the light projection signals 50b to 57b and the light reception signals 70b to 77b.

  The amplitude average value calculation unit 18a obtains the amplitude value of the light reception signals 71c to 77c, that is, the maximum voltage value of each of the light reception signals 71c to 77c, for each period T1. Here, since the light reception signals 71c to 77c are sine waves, in order to obtain the maximum voltage value, it is necessary to sample the voltage value at a timing when the amplitude reaches a peak. However, this requires a detection circuit and a peak hold, which increases the circuit scale. Therefore, in the present embodiment, sampling is performed a plurality of times at a predetermined timing for each light reception signal 71c to 77c period T1, and the maximum absolute value of the obtained voltage values is set as the maximum voltage value.

  Then, the amplitude average value calculation unit 18a calculates average values AA1 to AA7 of the maximum voltage values for each period T2 (second period) that is a natural number multiple of the period T1.

  The phase difference average value calculation unit 18b subtracts the phase difference voltage value P0 from the phase difference voltage values P1 to P7 (DP1 = P1-P0, DP2 = P2-P0,..., DP7 = P7−). P0) and average values PA1 to PA7 of the subtraction values DP1 to DP7 are calculated for each period T3 (third period) that is a natural number multiple of the period T1.

  Further, the CPU 18 further stores an amplitude reference value storage unit (first value) in which the average values AA1 to AA7 to be calculated by the amplitude average value calculation unit 18a when there is no object in the detection area are stored as amplitude reference values AR1 to AR7. 18c and the phase difference reference stored in advance as the phase difference reference values PR1 to PR7 as the average values PA1 to PA7 to be calculated by the phase difference average value calculation unit 18b when there is no object in the detection region. And a value storage unit (third storage means) 18d.

  The CPU 18 also determines the amplitude reference values AR1 to AR7, the phase difference reference values PR1 to PR7, the average values AA1 to AA7 calculated by the amplitude average value calculation unit 18a, and the average value PA1 calculated by the phase difference average value calculation unit 18b. Based on ~ PA7, it has a determination unit 18e that determines the presence or absence of an object in the detection region and outputs a determination signal.

As shown in Table 1, the determination unit 18e is configured such that the difference AA1-AR1, AA2-AR2,... Between the average values AA1 to AA7 related to the amplitude calculated by the amplitude average value calculation unit 18a and the amplitude reference values AR1 to AR7. If any of AA7-AR7 is outside the predetermined range (first range), it is determined that there is some object in the detection area.
On the other hand, when the difference between the average values AA1 to AA7 related to the amplitude and the amplitude reference values AR1 to AR7 are within a predetermined range, the average values PA1 to PA7 related to the phase difference calculated by the phase difference average value calculating unit 18b and When any of the differences PA1-PR1, PA2-PR2,..., PA7-PR7 from the phase difference reference values PR1 to PR7 is outside the predetermined range (second range), the determination unit 18e It is determined that there is an object.
The determination unit 18e determines that there is no object in the detection region in cases other than the above.

That is, when any of the differences between the average values AA1 to AA7 and the amplitude reference values AR1 to AR7 related to the amplitudes of the light reception signals 71c to 77c is outside the first range, the determination unit 18e As a result, it is determined that the light receiving element 35 receives excessive or too small reflected light, and it is determined that “there is an object”.
On the other hand, when the difference between the average values AA1 to AA7 related to the amplitude and the amplitude reference values AR1 to AR7 are all within the first range, the determination unit 18e is similar to the conventional optical phase difference detection type object detection sensor. Detects the presence of an object. That is, the determination unit 18e determines that “there is an object” if any of the differences between the average values PA1 to PA7 related to the phase difference and the phase difference reference values PR1 to PR7 are outside the second range, and otherwise. It is determined that there is no object.

[Action / Effect]
According to the optical phase difference detection type object detection sensor 1 configured as described above, the average values AA1 to AA7 and the amplitude reference values AR1 to AR1 relating to the amplitudes of the light reception signals 71c to 77c calculated by the amplitude average value calculation unit 18a. It is always determined whether or not the difference from AR7 is within a predetermined range (first range). Here, the amplitude reference values AR1 to AR7 are average values AA1 to AA7 to be calculated by the amplitude average value calculation unit 18a when there is no object in the detection region. Therefore, if the difference between the average values AA1 to AA7 related to the amplitude and the amplitude reference values AR1 to AR7 is outside the predetermined range, the light receiving element 35 receives excessive or too small reflected light due to the presence of some object in the detection region. It is possible to determine that the object is present. That is, according to the object detection sensor 1, the presence or absence of an object can be accurately detected without erroneous detection even when the light receiving element 35 receives excessive or excessive reflected light.

Further, the object detection sensor 1 includes a light projecting element 34 fixedly disposed in the immediate vicinity of the light receiving element 35 so that the light projecting element 34 projects reference light directly received by the light receiving element 35. It has become.
Here, since the reference light is directly received by the light receiving element 35, the phase difference voltage value P0 for the reference light should always be constant in principle. However, in reality, since the electronic components on the detection circuit have temperature characteristics, the phase difference voltage value P0 changes due to the influence of the ambient temperature. Similarly, the phase difference voltage values P1 to P7 for the reflected light of the detection light of each light projecting element 33 also vary depending on the ambient temperature.
Therefore, the object detection sensor 1 subtracts the phase difference voltage value P0 for the reference light from the light projecting element 34 from the phase difference voltage values P1 to P7 for the reflected light of the detection light of each light projecting element 33. DP1 to DP7 are calculated, and object detection is performed based on whether or not the difference between the average values PA1 to PA7 of the subtraction values DP1 to DP7 and the phase difference reference values PR1 to PR7 are within a predetermined range. Yes. Even if the phase difference voltage value changes due to the ambient temperature, the subtraction is canceled by this subtraction. Therefore, the object detection sensor 1 can always accurately detect the presence or absence of the object regardless of the ambient temperature. .

  Moreover, since the object detection sensor 1 has the some light projection element 33 and the light receiving element 35, it can detect the presence or absence of an object in a comparatively wide detection area | region.

[Modification]
Although the embodiments of the present invention have been specifically described above, the present invention can be implemented with the following modifications.

  For example, as shown in FIG. 7, an initial setting unit 18f for automatically storing the amplitude reference values AR1 to AR7 and the phase difference reference values PR1 to PR7 in the amplitude reference value storage unit 18c and the phase difference reference value storage unit 18d in advance. You may provide in CPU18.

  The initial setting unit 18f is activated when the object detection sensor 1 is installed at one end of the detection area and when there is no object in the detection area, and performs various initial settings. When receiving the initial setting signal T from the outside, the initial setting unit 18f stores the average values AA1 to AA7 related to the amplitude calculated by the amplitude average value calculation unit 18a as the amplitude reference values AR1 to AR7 in the amplitude reference value storage unit 18c. Let Similarly, when the initial setting unit 18f receives an initial setting signal T from the outside, the phase difference average values PA1 to PA7 calculated by the phase difference average value calculation unit 18b are used as phase difference reference values PR1 to PR7. It is stored in the reference value storage unit 18d.

  The initial setting unit 18f further measures variations of the subtraction values DP1 to DP7 related to the phase difference that is the original data of the average values PA1 to PA7 stored in the phase difference reference value storage unit 18d.

  As shown in Table 2, the initial setting unit 18f determines whether or not the maximum voltage value (amplitude value) related to the amplitude that is the original data of the average values AA1 to AA7 stored in the amplitude reference value storage unit 18c is within a predetermined range. Based on whether or not the variations of the subtraction values DP1 to DP7 are within a predetermined range, the calculation periods T2 and / or T3 of the average values AA1 to AA7 and PA1 to PA7, and the determination unit 18e The first range and / or the second range used for determination are automatically set.

  That is, when any of the amplitude values is outside the predetermined range, the initial setting unit 18f performs initial setting on the assumption that the light receiving element 35 receives excessive or excessive reflected light and is not in an environment for performing each initial setting. Generate an error signal without doing so. If the error signal is generated, the factor that caused the abnormal reflected light is removed by the operator, and then the initial setting signal T is input again, and the initial setting is executed.

  On the other hand, when any of the amplitude values is within the predetermined range and any of the variations of the subtraction values DP1 to DP7 related to the phase difference is outside the predetermined range, the initial setting unit 18f is within the detection region. Is recognized as an environment in which phase difference detection is likely to vary due to some influence. Then, the initial setting unit 18f makes the average value calculation periods T2 and T3 longer than the initial values and makes the first range and the second range wider than the initial values in order to cope with this environment.

  According to the object detection sensor 1 including the initial setting unit 18f as described above, the reference values AR1 to AR7 and PR1 to PR7 can be automatically stored in the reference value storage units 18c and 18d.

  Further, according to the object detection sensor 1 provided with the initial setting unit 18f, the average value calculation periods T2 and T3 and the first for object presence determination are determined according to the reflection state of the other end in the actually installed detection region. The second range and the second range can be set optimally and automatically.

  In the above modification, the average value calculation cycle and the first and second ranges are adjusted according to the amplitude value and the variation in the subtraction value related to the phase difference. However, only the maximum voltage value related to the amplitude is adjusted. The adjustment may be made according to the difference, or the adjustment may be made only according to the variation of the subtraction value related to the phase difference. Further, according to the maximum voltage value related to the amplitude or the variation of the subtraction value related to the phase difference, any one of the average value calculation periods, the first range, and the second range is appropriately selected and adjusted. Also good.

  Further, it is sufficient that at least one of the light projecting element 33 and the light receiving element 35 is sufficient, and the number of the light projecting element 33 and the light receiving element 35 can be appropriately changed according to the width of the detection region.

  Further, the light projecting element 34 that projects the reference light can be omitted when the influence of the ambient temperature can be ignored.

It is a side view which shows an example of the object detection sensor of the optical phase difference detection type concerning this invention. It is a sectional side view which shows the main-body part of the object detection sensor of FIG. It is a bottom view which shows arrangement | positioning of the optical element in the object detection sensor of FIG. It is a block diagram for showing the circuit structure of the object detection sensor of FIG. It is a time chart of the light projection signal produced | generated in the object detection sensor of FIG. It is a figure for showing the phase difference signal generated in the object detection sensor of FIG. It is a block diagram which shows CPU of the optical phase difference detection type object detection sensor concerning a modification. It is a figure for demonstrating the fault of the conventional object detection sensor of an optical phase difference detection type.

Explanation of symbols

AA1 to AA7 Amplitude average values AR1 to AR7 Amplitude reference values PA1 to PA7 Phase difference average values PR1 to PR7 Phase difference reference values 18a Amplitude average value calculation means (amplitude average value calculation unit)
18b Phase difference average value calculation means (phase difference average value calculation unit)
18e Determination means (determination unit)
50b to 57b Light projection signals 70b to 77b, 71c to 77c Light reception signals

Claims (7)

A sensor that is installed at one end of a detection area and detects the presence or absence of an object in the detection area,
A first light projecting element that projects detection light toward the detection region based on a first light projection signal including a predetermined number of light projection pulses generated for each first period;
A light receiving element that receives reflected light from the detection region of the detection light and generates a first light reception signal;
Amplitude average value calculating means for measuring the amplitude of the first received light signal for each first period and calculating an average value for the amplitude for each second period that is a natural number multiple of the first period. When,
A first storage means that stores in advance an average value related to the amplitude to be calculated when the light receiving element receives reflected light from the other end of the detection region of the detection light, and the first storage means The first phase difference between the first light projection signal and the first light reception signal is measured every period, and the first phase is measured every third period consisting of a natural number multiple of the first period. A phase difference average value calculating means for calculating an average value related to the phase difference of
Second memory in which an average value related to the first phase difference to be calculated when the light receiving element receives reflected light from the other end of the detection region of the detection light is stored in advance as a phase difference reference value. Means,
The difference between the average value related to the amplitude and the amplitude reference value is outside the first range, and if not, the difference between the average value related to the first phase difference and the phase difference reference value is the first A determination unit that determines that an object is present in the detection region when the object is outside the range of 2;
An optical phase difference detection type object detection sensor comprising: Initial setting means for automatically storing in advance the amplitude reference value and the phase difference reference value in the first and second storage means;
The initial setting means stores, in the first storage means, an average value related to the amplitude calculated by the average amplitude value calculation means as the amplitude reference value in accordance with an initial setting signal from the outside, and the phase difference 2. The light level according to claim 1, wherein an average value related to the first phase difference calculated by the average value calculating means is stored in the second storage means as the phase difference reference value. Phase detection type object detection sensor. The initial setting means automatically sets the second period, the third period, the first range and / or the second range in accordance with the amplitude value measured for each first period. The optical phase difference detection type object detection sensor according to claim 2, wherein the optical phase difference detection type object detection sensor is determined in a systematic manner. The initial setting means may determine the second period, the third period, the first range, and / or the first period depending on the degree of variation in the first phase difference measured for each first period. 3. The optical phase difference detection type object detection sensor according to claim 2, wherein the second range is automatically determined. The initial setting means, when the amplitude value measured for each first period is within a predetermined range, according to the degree of variation in the first phase difference measured for each first period, The second period, the third period, the first range and / or the second range are automatically determined, and if not, an error signal is generated. The optical phase difference detection type object detection sensor according to claim 2. A plurality of the first light projecting elements and the light receiving elements, respectively,
The first projection signal is generated for each of the first projection elements,
Each of the first light projecting elements sequentially projects the detection light based on the first light projecting signal,
The light receiving element generates the first light receiving signal for each detection light,
The amplitude average value calculating means measures the amplitude of each of the first light receiving signals for each of the first periods, calculates the average value for each of the amplitudes for each of the second periods,
The first storage means stores in advance the amplitude reference value for the average value for each amplitude,
The phase difference average value calculating means measures the first phase difference between each first light projection signal and each first light reception signal for each first period, and An average value for each of the first phase differences is calculated for each period,
The second storage means stores in advance each of the phase difference reference values for an average value related to each of the first phase differences,
The determination means determines whether the difference between the average value for each amplitude and the amplitude reference value is outside the first range, and if not, the average for each first phase difference. When any of the difference between the value and each phase difference reference value is outside the second range, it is determined that there is an object in the detection region,
The optical phase difference detection type object detection sensor according to claim 1, wherein the object detection sensor is configured as described above. A second light projecting element fixedly disposed in the immediate vicinity of the light receiving element, including a plurality of light projecting pulses generated for each first period, and having the first light projecting signal and the light projecting timing. Based on the second light projection signal that does not overlap, further comprising a light projecting reference light toward the light receiving element,
The light receiving element further receives the reference light and generates a second light receiving signal,
The phase difference average value calculating means further measures a second phase difference between the second light projection signal and the second light reception signal for each first period, and the first phase difference and An average value regarding a subtraction value with the second phase difference is calculated for each third period,
The determination means includes a case where a difference between an average value related to the amplitude calculated by the amplitude average value calculation means and the amplitude reference value is outside the first range, and a case where the difference is not, and the phase difference average When the difference between the average value related to the subtraction value calculated by the value calculation means and the phase difference reference value is outside the second range, it is determined that there is an object in the detection region;
The optical phase difference detection type object detection sensor according to any one of claims 1 to 6.

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