JP5877766B2 - Beam sensor signal processing circuit - Google Patents

Description

  The present invention includes, for example, a projector and a light receiver, which are installed opposite to each other, receive the light projected from the light projector by the light receiver, and output a warning signal when the beam is interrupted by an intruder. The present invention relates to a signal processing circuit of a sensor.

  Conventionally, as a beam sensor for crime prevention, a linear warning area is formed by an infrared beam, and the distance between a light projector having a light projecting element and a light receiver having a light receiving element is various from short distance to long distance. Various types are used depending on the range. In the case of these beam sensors, adjustment is made so that the optical axes of the light projector and the light receiver coincide with each other, and an electric signal corresponding to the amount of light received by the light receiver is formed in the light receiver, and the beam is blocked based on a predetermined threshold. In other words, it is determined whether or not there is an intruder.

  And at the maximum (rated) distance, no alarm signal is output even if the beam intensity is attenuated to about 1/100 compared to the case when the atmospheric condition in fine weather is good (hereinafter referred to as steady state). It is like that. This is because when it is installed outdoors, it is affected by atmospheric conditions such as the weather, so even if the beam incident on the receiver is attenuated by rain or fog, This is because an alarm is not output unless the beam is interrupted.

  In addition, when used in short distances shorter than the maximum (rated) distance, the amount of light incident on the light receiver (light receiving element) in the steady state increases, but the threshold for outputting an alarm signal is fixed, so the steady state In some cases, the alarm signal is not output even if the value is considerably less than 1/100. Therefore, a method has been devised for adjusting the intensity (light quantity) of the projected beam and the amount of received light incident on the light receiver when installed at a maximum (rated) distance or less. By this adjustment, the ratio of the received light amount of the beam at the time of normal operation and the output of the alarm signal is set to be substantially constant even at a short distance.

  In addition, the amount of light received by the receiver when used at short distances is larger than that used at the maximum (rated) distance under the same atmospheric conditions, and the amount is inversely proportional to the square of the distance, so the distance is half. In the case of, it becomes 4 times. And the shorter the distance, the greater the amount of light received by the receiver. Therefore, when using a long-distance beam sensor for short distances, the intensity of the projected beam depends on the distance. Need to be adjusted. For example, Patent Document 1 discloses a method for adjusting the intensity of light projection and light reception of a security sensor using an infrared beam.

JP 2006-155478 A

  However, in such a beam sensor, it is necessary for the installation operator to manually adjust the light projection amount of the beam projected from the projector according to the warning distance by an adjuster such as a light amount attenuating plate provided in the projector. Therefore, the installation work of the beam sensor becomes complicated, and when the actual distance and the set distance do not match, there is a possibility that a stable warning operation becomes difficult. That is, in the case of the beam sensor shown in Patent Document 1 that adjusts the posture of each light attenuation plate arranged in a plurality of layers, in many cases, the actual warning distance is accurately measured (obtained) at the installation site. It is difficult, and the actual measurement of the distance itself will further complicate the installation work, and there is no guarantee that the work to adjust the beam intensity will be performed reliably, and stable warning operation will be realized It may not be possible.

  Here, the reason why a stable warning operation cannot be performed unless the light projection amount is adjusted when the beam sensor is installed will be described. As described above, the conventional beam sensor does not output an alarm signal even if the beam is reduced to about 1/100 of the steady state so that the alarm operation can be stably performed even in bad weather at the maximum (rated) distance. ing. In order to make this easier to understand, it is assumed that an alarm signal is output when the beam decreases to 1/100 of the steady state at the maximum (rated) distance. And

  In general, a beam sensor is required to be able to perform a warning operation stably from a long distance to a short distance. For example, a beam sensor for 500 m has a maximum (rated) distance of 500 m and can perform a warning operation stably. The intensity of light projection and the amplification factor of the light receiver are provided. Even if outdoor use is considered, even if the beam is attenuated by the influence of the weather, the alarm signal should not be output if there is no intruder. Specifically, even if the received light amount is attenuated to, for example, about 1/100 with respect to the case where there is no optical obstacle when the beam is clear due to rain, fog, etc., The amplification factor and the alert level are adjusted. However, in the case of a beam sensor having a maximum (rated) distance of 500 m, it is sufficiently conceivable to use it at a maximum (rated) distance or less, for example, 100 m.

  In such a case, since the warning distance is 1/5, the amount of received light incident on the light receiver is incident in an inverse proportion to the square of 25 times. In addition, for example, an alarm signal is output when the received light amount becomes 1/100 of 500 m. Therefore, when used at 100 m, (1/25) × in the steady state without optical obstacles. If it does not attenuate to (1/100) = 1/2500, an alarm signal will not be output. In this case, even if an intruder enters between the projector and the receiver and blocks the beam (optical axis), the beam reflected by the ground or the wall of a nearby building is incident on the receiver. Can not output an alarm signal, and is prone to a detection error called a misreport that is not output when an alarm signal should be output.

  Therefore, in order to avoid these situations, some conventional beam sensors adjust the light projection amount of the beam using a volume or the like. However, in the case of such a beam sensor, the actual installation distance is rarely clear at the stage of installation, and it is complicated to adjust the installation distance according to the installation distance. In particular, when a plurality of beam sensors are installed in various places according to various installation distances, the adjustment work of each beam sensor becomes extremely complicated. Also, for example, adjustment to the long distance side may result in misreporting, and conversely if it is set to the short distance side, false alarms may occur when it is attenuated by rain, etc. Sometimes it does not work.

  Moreover, as shown in Patent Document 1, the method of reducing the light projection amount using the light amount attenuation plate is more complicated than the adjustment by the volume described above. Furthermore, an automatic gain adjustment (AGC) circuit is provided, and when the amount of incident light is large, the amplification factor is reduced, and when the amount of incident light is small, the amplification factor is increased to determine the magnitude of the signal input to the comparator. Regardless of the method, there is a method that is almost constant, but in this method, the circuit scale is large because the amplification factor of the amplifier is adjusted by measuring the magnitude of the signal input to the comparator. As a result, the number of parts and the cost increase. In addition, there is a limit to the adjustment range of the amplification factor, and if a signal exceeding the adjustment range of the amplification factor is input, the signal will saturate and the comparator will not be able to make a correct judgment and an intruder cannot be detected. There is.

  The present invention has been made in view of such circumstances, and an object thereof is to issue a notification level by determining the amount of received light based on both the output signal from the amplifier circuit at the final stage and the input signal to the amplifier circuit. Thus, it is an object of the present invention to provide a signal processing circuit for a beam sensor that can stably detect an intruder at a long distance or a short distance without performing complicated adjustment work during installation.

In order to achieve such an object, the invention described in claim 1 of the present invention includes a light receiving element that receives and photoelectrically converts a beam projected from a projector through a light receiving optical system, and the light receiving element performs photoelectric conversion. In the signal processing circuit of the beam sensor for determining whether or not the beam is blocked according to the magnitude of the converted output signal, the signal processing circuit includes at least one amplifier circuit, a final stage amplifier circuit, and the final stage amplifier circuit. A first comparator that compares the input signal of the first stage with a first threshold value, and a second comparator that compares the output signal of the final stage amplifier circuit with a second threshold value . When the input signal is determined to be lower than the first threshold in the first comparator and the time required for the decrease is not equal to or greater than a predetermined value, or the output signal of the final stage amplifier circuit is the second signal Smell in comparator It is judged to be lower than the second threshold value, and when the time taken to decrease is less than the predetermined value, determines that there is an intruder, an output enable control circuit an alarm signal, the control circuit, According to the input signal of the final stage amplifier circuit, the first threshold value is varied so that the difference between the steady state level and the level determined to be an intruder is substantially the same, and the output signal of the final stage amplifier circuit is Accordingly, the second threshold value is varied so that the difference between the steady state and the level at which it is determined that there is an intruder is substantially the same.

The invention according to claim 2 is characterized in that the first threshold value and the second threshold value are combined .

  According to the first aspect of the present invention, the control circuit capable of outputting an alarm signal based on the output signals of the first comparator and the second comparator is used as the input signal of the final stage amplifier circuit. Accordingly, the first threshold value of the first comparator is changed, and the second threshold value of the second comparator is changed in accordance with the output signal of the final stage amplifier circuit. The detection level can be changed by determining the amount of light received based on both the input signal and the input signal of the amplifier circuit, making it easy to perform adjustment work during installation, and stable entry even at long or short distances. Can be detected.

In addition, since the control circuit varies the first threshold value according to the input signal of the final stage amplifier circuit and also varies the second threshold value according to the output signal of the final stage amplifier circuit, the notification level corresponding to the situation Can be accurately performed, and by setting the width of each threshold value to be varied in advance, the control for variation can be simplified.

According to the invention described in claim 2 , in addition to the effect of the invention described in claim 1 , since the first threshold value and the second threshold value are combined, one threshold value is set for two signals. The threshold value can be continuously changed regardless of the amount of received light, and an optimum sensitivity margin can always be set regardless of the installation distance.

The block diagram which shows one Embodiment of the beam sensor using the signal processing circuit concerning this invention The figure which shows the light pulse by the same light projector and the pulse after detection with the light receiver Flow chart showing threshold control at the same optical axis adjustment Flow chart showing threshold control when the alarm occurs Timing chart for threshold change and alarm generation Explanatory drawing in the case of using both the first threshold value and the second threshold value The block diagram which shows the modification of the beam sensor concerning this invention

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 to 5 show an embodiment of a beam sensor using a signal processing circuit according to the present invention. As shown in the block diagram of FIG. 1, the beam sensor 1 includes a projector 2 and a light receiver 3, which are installed so as to face each other on a pole or a wall of a building (not shown) with a predetermined distance, An infrared beam projected from the projector 2 is received by the light receiver 3 to form a linear alert area. At this time, the light projecting unit composed of the light projecting element 6 and the light projecting optical system 7 of the light projector 2 and the light receiving unit composed of the light receiving optical system 8 and the light receiving element 9 of the light receiver 3 are opposed to each other to project and receive the beam. The orientation has been adjusted so that

  The projector 2 includes a pulse generation circuit 4, a light projecting element drive circuit 5, the light projecting element 6 and a light projecting optical system 7, a power supply circuit (not shown), and the like. The light projecting element 6 is generally an infrared light emitting diode (LED), but a laser light emitting diode or visible light can also be used. Further, the projection pulse projected from the projector 2 uses a projection pulse as shown in FIG. 2A, and this projection pulse is transmitted through a projection optical system 7 including a lens, a reflecting mirror, and the like. The light is projected in a predetermined direction.

  The light receiver 3 includes the light receiving optical system 8 and the light receiving element 9, a current / voltage conversion circuit 10, a filter circuit 11, a detection circuit 12, a final stage amplifier circuit 13, and a first comparator 14. And a second comparator 15, a control circuit 16, an alarm signal output circuit 17, a power supply circuit (not shown), and the like. The light receiving element 9 uses a phototransistor or a photodiode, and converts an infrared beam incident through the light receiving optical system 8 including a lens and a reflecting mirror into a current according to the incident amount. The current converted by the light receiving element 9 is converted into a voltage by the current / voltage conversion circuit 10.

  The filter circuit 11 uses a band-pass filter and passes (filters) only the projection pulse from the projector 2, and the filtered projection pulse is detected by the detection circuit 12 and shown in FIG. 2 (b). Such a pulse waveform is generated. An output voltage (referred to as an output signal S1) detected by the detection circuit 12 is input to the first comparator 14 and the control circuit 16, and is also input to the final stage amplifier circuit 13 to be amplified. The final stage amplifier circuit 13 The output voltage amplified in step (referred to as output signal S2) is input to the second comparator 15 and the control circuit 16. At this time, the detection circuit 12 provided in the previous stage of the final stage amplifier circuit 13 has a saturation prevention function for preventing the saturation of the output signal S1 in addition to the detection (waveform shaping) function. The number of stages of the filter circuit 11 and the amplification factor of the final stage amplifier circuit 13 are appropriately set according to the intensity and frequency of the input beam.

  The first comparator 14 and the second comparator 15 include a first threshold value K1 and a second threshold value K2 set by the control circuit 16, and an output signal S1 of the detection circuit 12 (the final stage amplifier circuit 13). And the output signal S2 of the final stage amplifier circuit 13 and the comparison result is output to the control circuit 16.

  The control circuit 16 includes a microcomputer, a storage unit, a setting unit, a timer, and the like (all not shown), and is used in the first comparator 14 and the second comparator 15. The threshold value K1 and the second threshold value K2 are set and stored, and these threshold values K1 and K2 are set according to the output signal S1 of the detection circuit 12 and the output signal S2 from the final stage amplifier circuit 13 as described later. Fluctuate. The control circuit 16 constantly monitors (measures) the output signal S1 of the detection circuit 12 and the output signal S2 of the final stage amplifier circuit 13. When the control circuit 16 determines that there is an intruder based on the two output signals that are the comparison results of the first comparator 14 and the second comparator 15, the control signal 16 outputs the warning signal to the warning signal output circuit 17. Is sent out (output).

  Here, the operation of the beam sensor 1 when the beam projected from the projector 2 (projection pulse) is changed from the state where it is not incident on the light receiver 3 to the state where it is incident on the light receiver 3 will be described. To do. First, when performing the installation work of the beam sensor 1, when the optical axes of the projector 2 and the light receiver 3 do not coincide with each other (when the light projector 2 and the light receiver 3 are installed and the power is turned on), the light reception is performed. The output signal S2 from the final stage amplifier circuit 13 of the device 3 is compared with the second threshold value K2 by the second comparator 15, but since the beam is not incident, the output signal S2 is less than or equal to the second threshold value K2. The alarm signal is sent from the control circuit 16 to the alarm signal output circuit 17. At this time, the output signal S2 from the final stage amplifier circuit 13 is set to 0V, and the value of the second threshold value K2 is set to 0.5V which is the minimum value.

  Then, the control circuit 16 constantly monitors the magnitudes of the output signal S1 from the detection circuit 12 and the output signal S2 from the final stage amplifier circuit 13, that is, how much light is received by the magnitude. The alerting level is changed by changing (changing) the first threshold value K1 and the second threshold value K2. The response speed for changing the first threshold value K1 and the second threshold value K2 is sufficiently slower (approximately several seconds) than the speed at which the intruder blocks the beam (approximately 1 second or less). This is because the threshold values K1 and K2 are not changed when the beam is cut off by an intruder, and the threshold values K1 and K2 are changed to reduce the beam due to rain, fog, or the like, so that the beam sensor 1 operates stably. It is.

Further, the control circuit 16 determines whether or not the output signal S2 is lower than the threshold value K2 when the output signal S1 is lower than the threshold value K1, the descent time T2 is equal to or longer than the predetermined time, and the threshold value K1 is the lowest value (FIG. 4 (see S204 in FIG. 4), and when it is low , a descent required time T2, which will be described later, is also used as an element of determination.

  Then, the optical axis is adjusted after installation, and the optical axes of the projector 2 and the light receiver 3 gradually match (the beam from the projector 2 enters the light receiver 3 little by little). When the output signal S2 from the circuit 13 gradually increases and exceeds the second threshold value K2 of 0.5 V, the control circuit 16 stops sending the alarm signal. Furthermore, when the optical axes are more matched and the amount of light incident on the light receiving element 9 increases, the output signal S1 from the detection circuit 12 input to the first comparator 14 becomes larger than the first threshold K1. At this time, the control circuit 16 monitors the magnitude (analog amount) of the output signal S2 from the final stage amplifier circuit 13, and becomes larger than a predetermined value (predetermined value 2 described later) determined stepwise. As described later, the second threshold value K2 is increased stepwise to the maximum value of 4.5V. Note that the predetermined value set in a stepwise manner to increase the second threshold value K2 is higher than the second threshold value K2 at that time.

  Further, when the optical axis matches and the amount of light input to the light receiving element 9 increases, the output signal S2 from the final stage amplifier circuit 13 further increases and reaches a saturation level of 5V. At this time, if the amplification factor of the final stage amplifier circuit 13 is set to 9 times, for example, the output signal S1 from the detector circuit 12 is about 1/9, which is about 0.6V. Further, the first threshold value K1 is also set to the first threshold value K1 by a predetermined value (predetermined value 1 described later) as the magnitude of the output signal S1 from the detection circuit 12 increases, similarly to the second threshold value K2. , Raise to the maximum value of 4.5V. When the first threshold value K1 and the second threshold value K2 increase (or decrease), a delay time is provided, and the target signals S1 and S2 have a predetermined value for a sufficient predetermined time T1. The threshold values K1 and K2 are increased when the threshold value K1 is exceeded, and the threshold values K1 and K2 are decreased when the predetermined time T2 is exceeded before the signals S1 and S2 fall below the threshold values K1 and K2. Yes.

  FIG. 3 is a flowchart specifically showing these operations. However, portions other than the operations related to these are omitted. Hereinafter, it will be described together with the timing chart of FIG. First, the control circuit 16 determines whether or not the output signal S2 of the final stage amplifier circuit 13 is higher than a predetermined value 2 (S101). If this determination S101 is “YES”, the control circuit 16 continues for the predetermined time T1. Whether or not (S102). If “NO” in this determination S102, the process returns to the determination S101. If “YES” in the determination S102, that is, if the output signal S2 of the final stage amplifier circuit 13 higher than the predetermined value 2 continues for the predetermined time T1. Then, it is determined whether or not the second threshold value K2 is the maximum value (4.5V) (S103).

  In the case of “NO” in this determination S103, that is, when the output signal S2 higher than the predetermined value 2 continues for the predetermined time T1 and the second threshold value K2 is not the maximum value, as shown in FIG. The second threshold value K2 and the predetermined value 2 are increased by one step (S107), and the process returns to step S101. 5A shows the output signal S2, B shows the second threshold value K2, C shows the stepwise predetermined value 2, and the output signal S2 is predetermined as shown in the figure. If the second threshold value K2 and the predetermined value 2 are exceeded for a time longer than the time T1, the second threshold value K2 and the predetermined value 2 are increased by one step when the predetermined time T1 has elapsed. The same applies to an output signal S1, a first threshold value K1, and a predetermined value 1 of the detection circuit 12, which will be described later.

  Next, if “YES” in the determination S103, it is determined whether or not the output signal S1 of the detection circuit 12 (input signal of the final stage amplifier circuit 13) is higher than a predetermined value 1 (S104). If “YES” in this determination S104, that is, if the output signal S1 of the detection circuit 12 is higher than the predetermined value 1, it is determined whether or not the predetermined time T1 continues (S105) as in the determinations S102 and S103. And whether or not the first threshold value K1 is the maximum value (4.5 V) is determined (S106).

  If “YES” in this determination S106, that is, if the first threshold value K1 is the highest value, the process returns to the determination S101, and if “NO” in the determinations S104 and S105, that is, the output of the detection circuit 12 When the signal S1 is not higher than the predetermined value 1 or when the predetermined time T1 does not continue, the process returns to the determination S101. On the other hand, if “NO” in the determination S106, that is, if the output signal S1 higher than the predetermined value 1 continues for the predetermined time T1 and the first threshold value K1 is not the maximum value, as in step S107, FIG. As shown in a), the first threshold value K1 and the predetermined value 1 are increased by one step (S108), and the process returns to the determination S101.

  That is, when the output signal S2 output from the final stage amplifier circuit 13 is continuously higher than the predetermined value 2 for the predetermined time T1 and the second threshold value K2 is not the highest value, the control circuit 16 When the threshold value K2 and the predetermined value 2 itself are increased by one step, and the output signal S1 output from the detection circuit 12 is continuously higher than the predetermined value 1 for a predetermined time T1, and the first threshold value K1 is not the maximum value The first threshold value K1 and the predetermined value 1 itself are increased by one step. As a result, the output signals S2 and S1 output from the final stage amplifier circuit 13 and the detection circuit 12 have predetermined values 1 and 2 set higher than the corresponding threshold values K1 and K2 longer than the predetermined time T1 set in advance. When exceeding, the threshold values K1 and K2 are increased by one step, and the new threshold values K1 and K2 and the output signals S1 and S2 are compared by the comparators 14 and 15, respectively.

Next, the operation when the beam sensor 1 detects an intruder will be described. Whether the amount of received light is sufficiently large is determined by the magnitude (analog amount) of the output signals S1 and S2 .

When the output signal S1 is lower than the threshold value K1, the descent time T2 is equal to or longer than the predetermined time, and the threshold value K1 is the lowest value, the output signal S2 from the final stage amplifier circuit 13 is larger than the second threshold value K2. In this case, it is determined that the intruder has not invaded. Note that 0.5 V, which is the minimum value of the second threshold value K2, corresponds to a level when the amount of received light decreases to 1/100 of the steady state at the maximum (rated) distance. Further, when the output signal S2 from the final stage amplifier circuit 13 is smaller than the second threshold value K2, and when the required descent time T2 is shorter than a predetermined value, it is determined that the beam is blocked by the intruder. Then, an alarm signal is sent from the control circuit 16.

  Further, as described above, the first threshold value K1 varies depending on the magnitude of the output signal S1 of the detection circuit 12, and when the output signal S1 is relatively large, the first threshold value K1 is increased and the absolute amount of the received light amount. If the output signal S1 is relatively small, the first threshold value K1 is lowered. This operation is the same for the relationship between the output signal S2 from the final stage amplifier circuit 13 and the second threshold value K2.

  These specific operations are shown in the flowchart of FIG. However, portions other than the operations related to these are omitted. This will be described below. First, as shown in FIG. 4, the control circuit 16 determines whether or not the output signal S1 of the detection circuit 12 is lower than the first threshold value K1 (S201). This determination S201 is repeated until “YES” is reached, and when “YES” is determined, it is determined whether the required descent time T2 is equal to or greater than a predetermined value (S202). If “YES” in this determination S202, It is determined whether or not the first threshold value K1 is the lowest value (0.5V) (S203).

  On the other hand, if “NO” in the determination S202, that is, if the required descent time T2 is not equal to or greater than the predetermined value, it is determined that there is an intruder and an alarm signal is generated as shown in FIG. 5C (S208). Then, it proceeds to a routine (not shown) such as alarm recovery. That is, as shown in FIG. 5C, since the required time T2 for dropping the output signal S1 is shorter than the predetermined value, the control circuit 16 determines that the beam has been interrupted due to intrusion or the like and issues an alarm. A signal will be sent out.

  If “NO” in the determination S203, that is, if the required time for lowering T2 is not less than a predetermined value and the first threshold value K1 is not the minimum value, as shown in FIG. 5B, the first threshold value K1. Is lowered by one step (S209), and the process returns to S201. 5B shows the output signal S1, and B shows the first threshold value K1, and as shown in the figure, the required time for descent T2 exceeds the predetermined value and the output signal S1 is If it is gradually decreasing, it is determined that the decrease is due to weather or the like, and for example, the first threshold value K1 is lowered by one step. The operation shown in FIG. 5B is similarly performed for an output signal S2 and a second threshold value K2 of the final stage amplifier circuit 13 to be described later.

  On the other hand, if “YES” in the determination S203, it is determined whether or not the output signal S2 of the final stage amplifier circuit 13 is lower than the second threshold K2 (S204). If “YES” in the determination S204, that is, if the output signal S2 of the final stage amplifier circuit 13 is lower than the second threshold K2, whether the required time T2 for the descent is equal to or greater than a predetermined value, as in the determinations S202 and S203. It is judged (S205), and then it is judged (S206) whether or not the second threshold K2 is the lowest value (0.5V). If “YES” in the determination S206, an alarm signal is generated (S207), and the process proceeds to a routine (not shown) such as alarm recovery. If “NO” in the determination S206, the second threshold K2 is lowered by one step (S211) as shown in FIG. 5B, and the process returns to the determination S201. If “NO” in the determination S205, that is, if the output signal S2 is lower than the second threshold K2 and the descent time T2 is not equal to or greater than the predetermined value, an alarm signal is generated (S210) as in the step S208. ) And proceed to a routine (not shown) such as alarm recovery.

  As described above, in the case of the beam sensor 1, the first threshold value K1 of the first comparator 14 is changed in accordance with the output signal S1 from the detection circuit 12, so that the beam of the beam at the normal time and at the time of sending the alarm signal is changed. The ratio of the amount of received light can be made substantially constant, and even when used at a shorter distance than the maximum (rated) distance, a stable warning operation can be performed. In this regard, conventionally, as described above, the amount of light received in the steady state varies greatly depending on the installation distance between the projector and the light receiver, and the alarm level is constant regardless of the distance. The ratio of the received light level, that is, the attenuation amount of the received light amount from the steady state to the alarm level varies depending on the installation distance, and a stable warning operation, that is, the alarm operation cannot be performed.

  Conventionally, the signal output from the final stage amplifier is compared by a comparator to determine whether or not to output an alarm signal. However, when this is used at a short distance, the signal is saturated. I could not make an accurate decision. On the other hand, since the first comparator 14 is provided in front of the final stage amplifier 13 in the present case, even when used at a short distance, the signal is not saturated and an accurate determination can be made.

  Further, in the beam sensor 1, by making the ratio of the received light levels substantially constant regardless of the installation distance, it is possible to prevent the report from being lost due to reflection from the surroundings. Needless to say, even if the beam is attenuated due to rain, fog, or the like, the warning operation can be stably performed. Further, not only the output signal S2 of the final stage amplifier circuit 13 that may be saturated at a short distance, but also the output signal S1 of the detection circuit 12 that is a signal of the previous stage of the final stage amplifier circuit 13 is output to the first comparator 14. Therefore, it is determined whether or not to send an alarm signal as compared with the first threshold value K1, so that the ratio between the steady state and the alert level can be kept constant even at a short distance.

  Here, as described above, when the maximum value of the second threshold value K2 is 4.5V and the minimum value is 0.5V, the ratio is 9 times. In other words, the second comparator 15 can operate stably even if it is used at a distance where there is a difference of 9 times in the amount of received light in the steady state. That there is a difference of 9 times in the amount of received light is 3 times in terms of the facing distance. Similarly, if the threshold value K1 of the first comparator 14 is changed so that a difference of 9 times is generated, a range of 3 times can be covered when converted to the facing distance. If the amplification factor of the final-stage amplifier circuit 13 is set to 9 times, the second threshold value K2 of the second comparator 15 is the highest value, and the first threshold value K1 of the first comparator 14 is the lowest value. The adaptive warning distance is the same. As the facing distance, √ (9 × 9) = 9, and from the rated (maximum) distance to 1/9 of the distance, it is possible to be vigilant. That is, if the maximum (rated) distance of the beam sensor 1 is 500 m, it is possible to perform a warning operation stably from an opposing distance of 500 m to about 1/9 of that distance, which is approximately 56 m.

  In the case of the beam sensor 1, the first comparator 14 and the second comparator 15 are arranged before and after the final stage amplifier circuit 13, and the first threshold value K 1 is set according to the output signal S 1 of the detector circuit 12. By appropriately changing, the ratio of the amount of light received during steady state and when sending an alarm signal (alarm level) can be kept approximately constant, and the watch is stable and alert at short distances than the maximum (rated) distance. An alarm action can be performed. That is, in addition to determining the signal output from the final stage amplifier, the signal input to the final stage amplifier 13, that is, the signal S1 before being amplified by the final stage amplifier 13 is also determined. As a result, it is possible to perform warning and intruder detection stably and reliably over long distances and short distances.

  As described above, according to the beam sensor 1 of the above embodiment, the control circuit 16 that can output the alarm signal based on the output signals of the first comparator 14 and the second comparator 15 outputs the output of the detection circuit 12. The first threshold value K1 of the first comparator 14 is varied according to the signal S1, and the second threshold value K2 of the second comparator 15 is varied according to the output signal S2 of the final stage amplifier circuit 13. Therefore, it is possible to determine the amount of received light and change the alarm level based on both the output signal S2 of the final stage amplifier circuit 13 and the output signal S1 of the detection circuit 12 input to the amplifier circuit 13, and the maximum (rated) A beam sensor 1 capable of stably detecting an intruder at a short distance or a short distance can be obtained.

  Further, since the detection circuit 12 provided in the preceding stage of the final stage amplifier circuit 13 has a saturation prevention function, an excessive signal is not input to the final stage amplifier 13, and the amplification factor of the final stage amplifier circuit 13 is 10 times or less. Therefore, the output signal S1 of the final stage amplifier circuit 13 when used at a short distance shorter than the maximum (rated) distance can be made difficult to saturate, and more stable detection can be achieved even at a short distance. It can be performed.

  In the above description, the control circuit 16 sets the first threshold value K1 and the second threshold value K2 for the first comparator 14 and the second comparator 15, respectively. K2 may be shared (shared). That is, since the saturation level (upper and lower limit values of the signal) of the signal processing circuit is common, when the larger voltage is 5 V, for example, and the smaller voltage is 0 V, the output signal S 1 from the detection circuit 12 is 0 V. Is set so that the output signal S1 is large when the signal (the amount of light received) is large. Further, the output signal S2 is set to be smaller than the output signal S1 and to have a maximum value of 0V when the signal (amount of light received) is large with 5V as a reference.

  In the state where a sufficient beam is incident, that is, in the case shown in FIG. 6A where the beam sensor 1 is installed at a short distance, the output signal S1 from the detection circuit 12 is 5V which is the maximum value. Is output. Also, since the output signal S2 from the final stage amplifier circuit 13 is an amplified signal of the output signal S1 from the detector circuit 12, the maximum value of 0 V (saturated state) is output. At this time, the common threshold value K of the first comparator 14 and the second comparator 15 indicated by a dotted line in FIG. 6 is a threshold value determined based on the output signal S1 because the output signal S1 is sufficiently large. K is 4.5V which is the maximum value.

  Next, in a state where the amount of incident light of the beam is slightly reduced, that is, in the case shown in FIG. 6 (b) used at a longer distance than in FIG. 6 (a), the output signal S1 from the detection circuit 12 is used. A signal slightly less than the maximum value is output. Further, since the output signal S2 from the final stage amplifier circuit 13 is obtained by amplifying the output signal S1 from the detector circuit 12, 0V (saturated state) which is the maximum value is output. At this time, in order to keep the difference (sensitivity margin Y) between the steady state and the alarm generation level constant, the threshold value K is lowered as compared with the case of FIG.

  Also, in the case shown in FIG. 6C, which is installed and used at a longer distance than in the case of FIG. 6B, the threshold value K is lowered than in the case of FIG. Since the amount of light received at this time is small, the output signal S2 from the final stage amplifier circuit 13 is slightly higher than 0V which is the maximum value. Furthermore, in the case shown in FIG. 6 (d) that is installed and used at a longer distance than in FIG. 6 (c), the output signal S1 from the detection circuit 12 is lower than the threshold value K, but the final stage. The output signal S2 from the amplifier circuit 13 does not exceed the threshold value K. The control circuit 16 determines whether the signal to be compared with the threshold value K is the output signal S1 from the detection circuit 12 or the output signal S2 from the final stage amplifier circuit 13 while monitoring the analog amounts of both signals S1 and S2. Yes. In the case shown in FIG. 6C, since the threshold value K and the magnitudes of both signals S1 and S2 are close to each other, the control circuit 16 makes the above determination in this state.

  Furthermore, in the case shown in FIG. 6 (e), which is installed at a longer distance than in the case of FIG. 6 (d), the output signal S1 from the detection circuit 12 becomes a value close to the lowest value 0V, and the final stage The output signal S2 from the amplifier circuit 13 is also slightly smaller (voltage value is higher). Accordingly, the control circuit 16 increases the threshold value K so as to maintain the sensitivity margin Y. According to this example, when the control circuit 16 performs a predetermined operation while sharing the threshold value K, the received light amount (= installation distance) is any value using one threshold value K for the two signals S1 and S2. However, it is possible to continuously change the threshold value K and to obtain an effect that the optimum sensitivity margin Y can always be set for the beam sensor 1 regardless of the installation distance.

  In the beam sensor 1, the detection circuit 12 is provided between the filter circuit 11 and the final stage amplification circuit 13. However, for example, as shown in FIG. 7, an amplification circuit 18 is provided instead of the detection circuit 12. You can do it. Further, the filter circuit 11 or the detection circuit 12 itself has an amplifying function, a limiter such as a diode is added so as not to saturate the output signal, or the amplifier circuit has a plurality of stages as described above. By comparing the input signal S1 and the output signal S2 of the stage amplifier circuit 13 with the two comparators 14 and 15, an appropriate circuit configuration capable of obtaining an equivalent effect can be employed.

  Further, in the beam sensor 1 of the above-described embodiment, the installation form of the light projector 2 and the light receiver 3 arranged opposite to each other, the number of stages (variation width) when the first and second threshold values K1 and K2 fluctuate, and the control circuit 16 The operation (flow chart), the block diagram, the pulse pattern, etc. are examples. For example, the operation can be applied to the beam sensor 1 in which a plurality of pairs of projectors 2 and light receivers 3 are installed, or the number of fluctuation stages of the threshold values K1, K2. Is set to three or more stages, or the control circuit 16 determines which of the comparators 14 and 15 is outputting by processing by software as well as hardware, and the thresholds K1 and K2 are pulsed. When the output is integrated and used as an analog quantity, it is fed back to the control circuit 16 to improve control accuracy, or a pulse pattern having an appropriate form is used. Without departing from the scope of the invention according to the present invention can be modified as appropriate.

  The present invention is applicable not only to an infrared beam but also to a crime prevention beam sensor using various beams such as a visible ray and a laser beam.

1 .... Beam sensor 2 .... Sender 3 .... Receiver 4 .... Pulse generator 5 .... Project Element drive circuit 6 .... Projecting element 7 .... Projecting optical system 8 .... Receiving optical system 9 .... Receiving element 10 .... ··· Current / voltage conversion circuit 11 ··· Filter circuit 12 ··· Detection circuit 13 ··· Final stage amplifier 14 ··· First comparator 15 .... Second comparator 16 .... Control circuit 17 .... Alarm signal output circuit 18 .... Amplifier circuit K1 .... First Threshold K2 ······· Second threshold K ········· Threshold (common)
S1 ······ Output signal of detector circuit (input signal of final stage amplifier circuit)
S2 ········ Output signal of final stage amplifier T1 ·······································································

Claims (2)

A beam sensor that includes a light receiving element that photoelectrically converts a light beam projected from a light projector through a light receiving optical system, and determines whether the beam is blocked by the magnitude of an output signal photoelectrically converted by the light receiving element In the signal processing circuit of
The signal processing circuit includes at least one amplifier circuit, a final stage amplifier circuit, a first comparator that compares an input signal of the final stage amplifier circuit with a first threshold value, and an output of the final stage amplifier circuit. A second comparator for comparing the signal with a second threshold , wherein the input signal of the final stage amplifier circuit is determined to be lower than the first threshold in the first comparator and decreases. When the time required is not equal to or greater than a predetermined value, or the output signal of the final stage amplifier circuit is determined to be lower than the second threshold in the second comparator, and the time required to decrease is equal to or greater than the predetermined value If not , determine that there is an intruder and have a control circuit that can output an alarm signal,
The control circuit varies the first threshold value according to an input signal of the final stage amplifier circuit so that a difference between a steady state level and a level determined to be an intruder is substantially the same, and the final stage amplification A signal processing circuit for a beam sensor, wherein the second threshold value is varied according to an output signal of the circuit so that a difference between a steady state level and a level at which an intruder is determined is substantially the same.   The signal processing circuit of the beam sensor according to claim 1, wherein the first threshold value and the second threshold value are combined.

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