JP4018515B2 - Multi-optical axis photoelectric switch and interference state canceling method of multi-optical axis photoelectric switch - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, a light projection scanning operation is repeatedly performed at a predetermined cycle between a plurality of light projecting elements and light receiving elements arranged in a state of being opposed so as to constitute a plurality of optical axes, so that the light receiving element is in a light receiving state. The present invention relates to a multi-optical axis photoelectric switch that detects an object to be detected and a method for eliminating an interference state of the multi-optical axis photoelectric switch.
[0002]
[Prior art]
In a multi-optical axis photoelectric switch in which a plurality of light projecting elements and light receiving elements are arranged facing each other to form a plurality of optical axes, for example, periodic pulsed light sequentially projected from each light projecting element side Is received by a corresponding light receiving element, and a synchronous detection method is employed in which a light reception signal from each light receiving element is detected based on a synchronization signal given from the light projecting element side.
[0003]
More specifically, among the light receiving signals output from the plurality of light receiving elements, only those that match the output timing of the synchronization signal output in synchronization with the light projecting timing of each light projecting element are the respective optical axes. For example, when the output of the light reception signal continues for a predetermined number of times or more, the light reception state is determined. Further, when the output is interrupted before the output of the received light signal continues for a predetermined number of times or more, it is determined that the light is blocked. Then, when the light shielding state continues for a predetermined number of times or more, it is determined that the detected object has been detected.
[0004]
According to this method, since only the signal received by the light receiving element at the timing when the synchronization signal is given is handled, it is possible to prevent the photoelectric switch from malfunctioning due to noise light from a lighting fixture or the like.
[0005]
However, even when such a multi-optical axis photoelectric switch of the synchronous detection method is used in combination with a plurality of photoelectric switches (for example, the same model) having a light projection period approximate to each other, there is mutual interference. There was a problem that it was likely to occur. In other words, if the light projection period is approximate, the state is maintained during operation if the light projection timing from both light projecting elements in the adjacent photoelectric switch is close to the start of the operation. This is because it becomes difficult to distinguish light projected from its own light projecting element from light projected from the light projecting element of the adjacent photoelectric switch (noise light).
[0006]
For example, if interference light with strong emission power is incident immediately before the light reception timing of a certain light receiving element, the output signal waveform of the amplifier circuit is affected by the influence of the interference light even if a light projection signal from the light projecting element is received thereafter. Due to the occurrence of a large undershoot, it may be determined as “light blocking” even though it is actually “light incident”.
[0007]
Therefore, in order to solve such a problem, for example, a slit is used to prevent the light from being received by another photoelectric switch by narrowing the range covered by the light projection from the light projecting element. However, since such an arrangement makes the optical axis thin, it becomes difficult to arrange between the light projecting and receiving elements, that is, to adjust the optical axis. Then, when vibration or impact is applied to the photoelectric switch, the optical axis is likely to be shifted, and as a result, malfunction is likely to occur.
[0008]
It is also conceivable to prevent mutual interference by reversing the arrangement relationship of the light projecting / receiving elements in both photoelectric switches so that one light projecting element and the other light receiving element do not face each other. However, even if such an arrangement is adopted, if the reflectance of the object to be detected is high, the light projected from the light projecting element of one photoelectric switch is reflected by the object to be detected and is reflected on the light receiving element of the other photoelectric switch. There is a risk of being received. Accordingly, it is not always possible to prevent the occurrence of interference.
[0009]
In addition, some photoelectric switches are provided with a switch for switching the light projection cycle of the light projecting element so that the light projection cycle is different from that of the adjacent photoelectric switch. There is a drawback that the size of the configuration is increased accordingly.
[0010]
Further, in Patent Documents 1 and 2, for the transmission type single optical axis photoelectric switch, the integration value of the integration circuit that performs the integration operation based on the light reception signal on the light receiving side is set to a predetermined value that is a timing for outputting the light reception detection signal. There is disclosed a configuration in which the influence of disturbance light that is incident at the same timing as other devices is eliminated by changing the light projection period in a transient state until it reaches.
[0011]
[Patent Document 1]
Japanese Patent No. 26005033
[0012]
[Patent Document 2]
Japanese Patent No. 3293044
[0013]
[Problems to be solved by the invention]
However, if the configurations disclosed in Patent Documents 1 and 2 are applied as they are to the multi-optical axis photoelectric switch, the light projection period is changed for each optical axis. In that case, since the response speed changes for each optical axis, there is a problem that the detection performance as a whole deteriorates.
[0014]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a multi-optical axis photoelectric switch that can efficiently eliminate the influence of disturbing light that enters from other devices at the same timing, Another object of the present invention is to provide an interference state elimination method for a multi-optical axis photoelectric switch.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, a multi-optical axis photoelectric switch according to claim 1 comprises a plurality of light projecting elements,
A plurality of light receiving elements arranged to constitute a plurality of optical axes opposite to the plurality of light projecting elements,
A light projection control means for repeating a light projection scanning operation for sequentially lighting the plurality of light projecting elements at a predetermined timing at a predetermined period;
A comparison in which each light receiving signal output from the plurality of light receiving elements is compared with a predetermined reference level, and a binarized signal corresponding to the comparison result is output in synchronization with the light projecting timing of the corresponding light projecting element. Means,
Comparison means for comparing with the reference level in synchronization with the light projection timing of the corresponding light projecting element, and outputting a binarized signal according to the comparison result;
Based on the binarized signal from the comparison means, when the detection state has occurred for a predetermined number of times of two or more consecutive light projection scan operations, the detection according to the presence or absence of the detected object is determined and detected. And a detection means for outputting a signal. When the binarized signal output by the comparison means for any one of the optical axes changes from a non-detection state to a detection state, the detection state is Scanning operation control means for changing the start timing of the light projection scanning operation at least once before reaching the predetermined number of times is provided.
[0016]
With this configuration, if the scanning operation control unit changes the start timing of the light projection scanning operation as described above, the light emission is performed in the vicinity of the multi-optical axis photoelectric switch with the same period as the light projection scanning period. When a noise light source having timing (for example, a multi-optical axis photoelectric switch of the same model) exists, thereafter, the light emission timings of the multi-optical axis photoelectric switch and the noise light source do not match. Therefore, the change of the binarized signal from the non-detection state to the detection state should be only once.
[0017]
In contrast, when the multi-optical axis photoelectric switch actually detects the presence or absence of the object to be detected, even if the scan operation control means changes the start timing of the light projection scan operation as described above. The change of the binarized signal from the non-detection state to the detection state should be continuous. Therefore, it is possible to efficiently and reliably detect the presence / absence of an object to be detected by eliminating the interference caused by the noise light source as described above.
[0018]
In this case, as described in claim 2, the storage unit stores the state of the binarized signal of each optical axis output from the comparison unit over one scan period or more of the projection scan operation,
The scanning operation control unit sequentially compares the binarized signal of each optical axis output from the comparing unit and the state of each binarized signal stored in the storage unit in the previous scan cycle, It may be configured to determine the change in state of the binarized signal.
[0019]
If comprised in this way, the scanning operation control means can change the start timing of a light projection scanning operation immediately after the scanning operation of 1 period is complete | finished. Therefore, the process for eliminating the interference caused by the noise light source can be started earlier.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. In FIG. 2, which shows a schematic electrical configuration of the multi-optical axis photoelectric switch as a functional block, the multi-optical axis photoelectric switch 1 includes a light projecting unit 2 and a light receiving unit disposed so as to face the light projecting unit 2. The unit 3 is constituted.
[0021]
The light projecting unit 2 includes a plurality of light projecting elements 4 and a light projecting control circuit (light projecting control means) 5 for controlling the light projecting timing of each light projecting element 4. On the other hand, the light receiving unit 3 detects a plurality of light receiving elements 6, a signal processing unit 7 for processing a light receiving signal received by each light receiving element 6, and a signal processed by the signal processing unit 7. And a microcomputer (detection means, scan operation control means) 8 for detecting an object.
[0022]
Further, the microcomputer 8 always outputs a start pulse for starting the scanning operation to the light projection control circuit 5 of the light projecting unit 2 at every cycle T. Then, when the start pulse is given, the light projection control circuit 5 serially outputs a light projection signal to each light projecting element 4, and uses the pulse signal having the same timing as the light projection signal as a synchronization signal. 3 is output to the signal processing unit 7.
[0023]
FIG. 3 is a functional block diagram showing a more detailed configuration centered on the signal processing unit 7 for one optical axis of the light receiving unit 3, and FIG. 4 is a diagram showing signal waveforms of each part in the signal processing unit 7. is there. The signal processing unit 7 includes an amplifier circuit 9, a comparison circuit (comparison means) 10, a synchronization circuit (comparison means) 11, and a shift register (comparison means) 12.
[0024]
The amplifier circuit 8 amplifies and outputs a signal received by the light receiving unit 3 (see FIG. 4B). The comparison circuit 10 compares the signal amplified by the amplification circuit 9 with a predetermined reference level and binarizes it, and outputs a pulse signal (binarized signal) to the synchronization circuit 11 (see FIG. 4C). ). The shift register 12 sequentially shifts the light reception timing signal set together with the output of the start pulse in accordance with the synchronization signal given from the light projecting unit 2 and gives it to the synchronization circuit 11 of each optical axis (FIG. 4 ( a)). The synchronization circuit 11 outputs a light reception signal synchronized with the light projection timing by taking the logical product of the pulse signal given from the comparison circuit 10 and the light reception timing signal (see FIG. 4D).
[0025]
Here, when the object to be detected is not located between the light projecting unit 2 and the light receiving unit 3, that is, between the light axis formed between the light projecting element 4 and the light receiving element 6, it is synchronized with the light receiving timing. When the detected light reception signal is output and the detected object is in a state of blocking the optical axis, the light reception signal is not output. Then, the microcomputer 8 performs detection detection of the detection object based on the light reception signal given from the synchronization circuit 11. Further, the microcomputer 8 has a built-in memory (for example, RAM, storage means) 13 for storing the light reception result.
[0026]
Next, the operation of this embodiment will be described with reference to FIGS. FIG. 5 is a flowchart showing the processing contents of the portion related to the scanning processing performed by the microcomputer 8. First, the microcomputer 8 outputs a start pulse to cause the light projection control circuit 5 of the light projection unit 2 to start a scanning operation (step S0). Then, in step S1, initialization necessary for the scanning process is performed. That is, while the optical axis number n being processed is set to “1”, Flags 1 and 2 for storing the transition of the light receiving state from “light incident → light shielding” and “light shielding → light incident” are both “ Reset to “0”.
[0027]
Subsequently, the microcomputer 8 confirms the light receiving state for the first optical axis (1) (step S2). If the light reception signal is output from the synchronization circuit 11, it is determined as “incident light”, and the result indicating “incident light” in the array Dn [0] of the memory 13 indicating the current scan result for the optical axis (n = 1) (for example, , “1”) is stored (step S3). Then, the microcomputer 8 reads and determines the contents of the array Dn [1] indicating the previous scan result from the memory 13 (step S4).
[0028]
In step S4, if the previous scan result is “light shielding”, the microcomputer 8 refers to the flag STATE_N that stores that “light shielding” continues for at least two scanning cycles (step S4a). If the flag STATE_N indicates “shield”, the flag STATE_N is set to “unconfirmed” (clear, step S4b), and “1” is set to Flag1 (step S5). If the flag STATE_N indicates “indeterminate” in step S4a, the process proceeds to step S11.
[0029]
In step S4, if the previous scan result is “incident light”, the microcomputer 8 sets the flag STATE_R, which stores that “incident light” continues for at least two scanning cycles, to “incident light” (step S4). S6). The fact that this flag STATE_R is set to “incident light” indicates that the detected object is in a non-detected state because the incident light state is determined. Note that the initial value of the array Dn [1] is set to “light incident”.
[0030]
On the other hand, when the microcomputer 8 determines that the light reception signal is not output from the synchronization circuit 11 in step S2 and is “shielded”, the result indicating “shielded” (for example, “0”) is stored in the array Dn [0] (step S7). ). Then, similarly, the contents of the array Dn [1] are read from the memory 13 and determined (step S8). If the previous scan result is “light incident”, the microcomputer 8 refers to the flag STATE_R (step S8a).
[0031]
In step S8a, if the flag STATE_R indicates “light incident”, the flag STATE_R is set to “unconfirmed” (step S8b), and “1” is set to Flag2 (step S9). If the flag STATE_R indicates “indeterminate” in step S8a, the process proceeds to step S11.
[0032]
If the previous scan result is “light shielding” in step S8, the microcomputer 8 sets the flag STATE_N “light shielding” (step S10). The fact that this flag STATE_N is set to “light shielding” indicates that the light shielding state is determined and the object to be detected is in the detection state because “light shielding” continues for two or more scanning cycles.
[0033]
After executing steps S5, S6, S9, and S10, the microcomputer 8 increments the optical axis number n (step S11). Then, it is determined whether or not the optical axis number n has reached the total number of optical axes (for example, “8”) (step S12). If not reached (“NO”), the process returns to step S2 to return to the next optical axis. Repeat the above process.
[0034]
On the other hand, when the optical axis number n reaches the total number of optical axes in step S12 (“YES”), the microcomputer 8 determines whether any one of Flags 1 and 2 is set to “1” (step S13). , S14).
[0035]
When both Flag1 and Flag2 are “0” in Step S13 or S14 (“NO”), “Incoming light” or “Light shielding” is confirmed in Step S6 or S10. Is set to “T” (step S15). Then, after waiting for elapse of the scan interval time (step S18, “YES”), the contents of the array Dn [0] in the current light receiving state are replaced with the contents of the array Dn [1] (step S27). The process proceeds to step S0.
[0036]
When Flag1 is set to “1” (step S13, “YES”), the light reception state is changed from “light shielding” to “light incident”, and the scan interval time is set to “T + α”. (Step S17). Then, the process proceeds to step S18. Further, when Flag2 is set to “1” (step S14, “YES”), the light reception state is changed from “light incident” to “light shielding”, and the scan interval time is set to “T-α”. (Step S16). Then, the process proceeds to step S18.
[0037]
The process based on the above flowchart is demonstrated with reference to the timing chart shown in FIG. The number of optical axes is “n = 4” for simplicity. When a start pulse is given from the microcomputer 8 (see FIG. 1A), the light projection control circuit 5 sequentially emits four light projection signals (1) to (4) in order to cause the four light projecting elements 4 to sequentially emit light. (4) Output (refer to FIG. 1B). In the scan (1), the optical axis is not blocked by the object to be detected and the influence of interference light is not present, and all the optical axes are in a light receiving state (see FIG. 1C).
[0038]
From this state, in scan (2), it is assumed that the object to be detected has changed from the light incident state to the light shielding state by actually blocking the second optical axis (see FIGS. 1C and 1E). In this case, the microcomputer 8 determines that the flag STATE_R is “light incident” in step S9a and sets it to Flag2 “1” in step S9. Therefore, the scan until the next scan (3) is started. The interval time is set to “T−α” (step S16), and becomes shorter than the original interval time T. That is, the start timing of the projection scan operation by the projection control circuit 5 is changed.
[0039]
In the scan (2), the interference light incident on the light receiving element 6 on the second optical axis shown in FIG. 1D is generated immediately before the light receiving timing. In such a case, as shown in FIG. 6, if the power (b) of the interference light is strong, even if the light projection signal (a) from the light projecting element 4 is subsequently received, the amplification circuit is affected by the influence of the interference light. A large undershoot occurs in the output signal waveform (c), and it may be determined as “light shielding” even though it is actually “light incident” (d). Note that the pulse amplitude in FIG. 6 does not reflect the power of the optical signal.
Accordingly, it is not possible to determine “light shielding” at the time of the scan (2), and the scan interval time is set to “T-α” and the process of the scan (3) is performed.
[0040]
In the subsequent scan (3), even if the scan interval time is set short, the light shielding state is detected at the second optical axis, so the microcomputer 8 performs the light shielding judgment (detection of the detected object) at that time (FIG. 1 (f) Refer to) Output the detection signal to the outside. At this time, since interference light that may cause undershoot in the signal waveform on the light receiving side is incident on the light receiving element 6 after the light receiving timing of the second optical axis, occurrence of undershoot is avoided. become able to.
[0041]
Then, the microcomputer 8 continuously determines light shielding in the scans (2) and (3) (step S10, STATE_N = “light shielding”), and whether both Flag1 and Flag2 are “0” (step S13, S14, “NO”), the scan interval time to the next scan (4) is set to “T” (step S15).
[0042]
The timing chart shown in FIG. 7 is another example. That is, in the scans (1) to (4), since the object to be detected continues to block the second optical axis, the light blocking state should continue to be determined. (See FIG. 7 (c), (2) optical axis).
[0043]
However, in the scan (2), it is assumed that the timing of the interference light incident on the second optical axis coincides with the light reception timing, so that the second optical axis has changed to the light incident state. (See FIGS. 7D and 7E). In this case, the microcomputer 8 determines in step S4a that the flag STATE_N is “shielded” and sets Flag1 to “1” in step S5. Therefore, the scan until the next scan (3) is started. The interval time is set to “T + α” (step S17), and becomes longer than the original interval time T. At this time, since the flag STATE_N is set to “indeterminate” in step S4b, the light shielding determination output signal is temporarily inactive (see FIG. 7F).
[0044]
In the subsequent scan (3), by setting the scan interval time to be long, the interference light enters the light receiving element 6 before the light receiving timing of the second optical axis, and the second optical axis is again shielded from light. Detected. Then, the microcomputer 8 continuously determines the light shielding in the scans (3) and (4) (step S10), and both of Flags 1 and 2 are “0” (steps S13, S14, “NO”). The scan interval time to the next scan (4) is set to “T” (step S15). At that time, the microcomputer 8 again performs the light shielding determination (detection of an object to be detected) (see FIG. 7F) and outputs a detection signal to the outside.
[0045]
In this case, the light receiving state changes from “incident light” to “light shielding” from scan (2) to (3), but the microcomputer 8 sets Flag1 to “1” in scan (2) as described above. The flag STATE_N is set to “indeterminate” before it is set to “” (step S4b). Accordingly, in the scan (3), Flag2 is not set to “1” because it is determined as “indeterminate” in step S8a.
[0046]
As described above, according to the present embodiment, the microcomputer 8 on the light receiving unit 3 side receives the signal received by the synchronization circuit 11 for any optical axis between the light projecting unit 2 and the light receiving unit 3 as a non-detected object. When the detection state is changed to the detection state, the start timing of the light projection scan operation by the light projection control circuit 5 is changed by changing the output timing of the start pulse.
[0047]
Therefore, even when there is a noise light source in the vicinity of the multi-optical axis photoelectric switch 1 and having a similar light emission timing with the same period as the light projection scanning period, such as a multi-optical axis photoelectric switch of the same model. The object to be detected can be detected efficiently and reliably by eliminating the interference caused by the noise light source.
[0048]
Further, the microcomputer 8 stores the output state of the pulse signal output from the comparison circuit 10 via the synchronization circuit 11 in the memory 13 over one scan period of the light projection scan operation, and the pulse of each optical axis in the current scan operation. The signal and the state of each pulse signal stored in the memory 13 in the previous scan cycle are sequentially compared to determine the change in the state of incident light and light shielding.
[0049]
Therefore, the microcomputer 8 can change the start timing of the light projection scan operation immediately after completing one cycle of the scan operation, and can start the process for eliminating the interference caused by the noise light source earlier.
[0050]
(Second embodiment)
FIG. 8 shows a second embodiment of the present invention. The same parts as those of the first embodiment are denoted by the same reference numerals and the description thereof is omitted. Only different parts will be described below. The configuration of the second embodiment is basically the same as that of the first embodiment, and the software processing by the microcomputer 8 is slightly different.
[0051]
In FIG. 8 showing the flowchart, the microcomputer 8 moves to step S11 when the light incident and light shielding states relating to the scan operation currently being performed are stored in the array Dn [0] in steps S3 and S7. That is, steps S4, S4a, S4b, steps S8, S8a, S8b are deleted (steps S5, S6 have been moved as described later).
[0052]
If “YES” is determined in step S12, the optical axis number n is set to the initial value “1” (step S21), and the contents of the arrays Dn [0] and Dn [1] having the same optical axis number match. Whether or not (step S22). If the two match, the light receiving state is determined by the contents of the array Dn [0].
[0053]
On the other hand, if the two do not match in step S22, the contents of the array Dn [0] are determined (step S24). If “incident”, step S5 is executed, and if “shielded”, step S6 is executed. Then, Steps S25 and S26 having the same contents as Steps S11 and S12 are executed, and if “NO” is determined in Step S26, the process returns to Step S22 and the above processing is repeated. Thereafter, the microcomputer 8 performs processing for all the optical axes, and if “NO” is determined in the step S26, the processing of the steps S13 to S18 and S27 is executed as in the first embodiment.
[0054]
As described above, according to the second embodiment, the light receiving state obtained in the current scanning operation is stored in the array Dn [0] continuously for one scan, and when the processing is completed, the array Dn [0] Since the contents are collectively compared with the array Dn [1] which is the light reception result obtained in the previous scan operation, it is not necessary to manage the flags STATE_R and N as in the first embodiment, and the processing is simplified. be able to.
[0055]
The present invention is not limited to the embodiments described above and illustrated in the drawings, and the following modifications or expansions are possible.
In the first embodiment, when the light shielding changes to the incident light, the scanning interval cycle may be changed to “T + β (a value different from α)”. In this case, the process using the flag STATE_R, N may be omitted.
The light incident and the light shielding may be determined when the light incident and the light shielding are continuously performed three times or more. In this case, the scan interval cycle may be changed twice or more.
In the first embodiment, when a change of “incident light” → “light shielding” is detected, only the process of setting the scan interval time to “T-α” may be performed.
Furthermore, steps S4a, S4b, S8a, and S8b may be deleted and the following processing may be performed. That is, Flag3 is set to “1” after execution of step S15. If “YES” is determined in the step S12, it is determined whether or not Flag3 is set to “1”. If it is not set to “1” (“NO”), the process proceeds to a step S15. If Flag3 is set to “1” (“YES”), the process proceeds to step S13.
That is, Flag3 is a flag for storing that the previous scan interval time was set to “T”. Then, only when the previous scan interval time is set to “T”, it is determined whether Flag 1 and 2 are set to “1” in steps S13 and S14. Flag3 is reset to “0” after the execution of steps S16 and S17. Even in such a case, the same effect as in the first embodiment can be obtained.
A type in which the relationship between incident light, light shielding, non-detection of the object to be detected, and detection is reversed (detection that the object is present between the light emitting and receiving units is in a steady state and no longer exists. It may be applied to a multi-optical axis photoelectric switch.
[0056]
【The invention's effect】
As apparent from the above description, the present invention has the following effects.
According to the multi-optical axis photoelectric switch according to claim 1, the scanning operation control means indicates that the binarization signal output from the comparison means for any one of the optical axes indicates that the presence / absence of the detected object is not detected. When the detection state is changed, the start timing of the light projection scan operation is changed at least once before the detection state reaches a predetermined number of times that detection of the detection object is determined by the detection means.
[0057]
Therefore, even when a noise light source having the same period and the same emission timing as the projection scan period exists in the vicinity of the multi-optical axis photoelectric switch, light emission from the multi-optical axis photoelectric switch and the noise light source thereafter. Timing will not match. Therefore, it is possible to efficiently and reliably detect the presence / absence of an object to be detected by eliminating interference caused by a noise light source.
[0058]
According to the multi-optical axis photoelectric switch according to claim 2, the scanning operation control means includes the binarization signal of each optical axis output from the comparison means and each binary stored in the storage means in the previous scanning cycle. The state of the binarized signal is determined by sequentially comparing the state of the binarized signal. Accordingly, the scan operation control means can change the start timing of the light projection scan operation immediately after the end of one cycle of the scan operation, and can start the process for eliminating the interference caused by the noise light source earlier. Become.
[Brief description of the drawings]
FIG. 1 is a timing chart showing the control contents of a scan cycle in a multi-optical axis photoelectric switch according to a first embodiment of the present invention.
FIG. 2 is a functional block diagram showing a schematic electrical configuration of a multi-optical axis photoelectric switch.
FIG. 3 is a functional block diagram showing a more detailed configuration centered on a signal processing unit for one optical axis of a light receiving unit.
FIG. 4 is a diagram illustrating signal waveforms of respective units in the signal processing unit.
FIG. 5 is a flowchart showing the processing contents of a portion related to scan processing performed by the microcomputer of the light receiving unit.
FIG. 6 is a waveform diagram for explaining the influence on the received light signal waveform when the power of the interference light is strong
FIG. 7 is a diagram corresponding to FIG. 1 showing different generation patterns of interference light.
FIG. 8 is a view corresponding to FIG. 5 showing a second embodiment of the present invention.
[Explanation of symbols]
1 is a multi-optical axis photoelectric switch, 4 is a light projecting element, 5 is a light projecting control circuit (light projecting control means), 6 is a light receiving element, 8 is a microcomputer (detecting means, scanning operation control means), and 10 is a comparison circuit. (Comparison means), 11 is a synchronous circuit (comparison means), 12 is a shift register (comparison means), and 13 is a memory (storage means).

Claims (4)

A plurality of light emitting elements;
A plurality of light receiving elements arranged to constitute a plurality of optical axes opposite to the plurality of light projecting elements,
A light projection control means for repeating a light projection scanning operation for sequentially lighting the plurality of light projecting elements at a predetermined timing at a predetermined period;
A comparison in which each light receiving signal output from the plurality of light receiving elements is compared with a predetermined reference level, and a binarized signal corresponding to the comparison result is output in synchronization with the light projecting timing of the corresponding light projecting element. Means,
Based on the binarized signal from the comparison means, when the detection state has occurred for a predetermined number of times of two or more consecutive light projection scan operations, the detection according to the presence or absence of the detected object is determined and detected. In a multi-optical axis photoelectric switch comprising detection means for outputting a signal,
When the binarization signal output from any of the optical axes by the comparison unit changes from a non-detection state to a detection state, the projection scan is performed until the detection state reaches the predetermined number of times. A multi-optical axis photoelectric switch comprising scan operation control means for changing an operation start timing at least once. Storage means for storing the state of the binarized signal of each optical axis output from the comparison means over one scan period or more of the light projection scan operation;
The scan operation control means sequentially compares the binarized signal of each optical axis output from the comparing means and the state of each binarized signal stored in the storage means in the previous scan cycle, 2. The multi-optical axis photoelectric switch according to claim 1, wherein a state change of the binarized signal is determined. A plurality of light emitting elements;
A plurality of light receiving elements arranged to constitute a plurality of optical axes opposite to the plurality of light projecting elements,
A light projection control means for repeating a light projection scanning operation for sequentially lighting the plurality of light projecting elements at a predetermined timing at a predetermined period;
A comparison in which each light receiving signal output from the plurality of light receiving elements is compared with a predetermined reference level, and a binarized signal corresponding to the comparison result is output in synchronization with the light projecting timing of the corresponding light projecting element. Means,
Based on the binarized signal from the comparison means, when the detection state has occurred for a predetermined number of times of two or more consecutive light projection scan operations, the detection according to the presence or absence of the detected object is determined and detected. A method of eliminating an interference state for a multi-optical axis photoelectric switch comprising a detection means for outputting a signal,
When the binarization signal output from any of the optical axes by the comparison unit changes from a non-detection state to a detection state, the projection scan is performed until the detection state reaches the predetermined number of times. A method of eliminating an interference state of a multi-optical axis photoelectric switch, wherein the operation start timing is changed at least once. The storage means stores the binarized signal of each optical axis output from the comparison means over one scan period of the light projection scan operation,
The binarization signal of each optical axis output from the comparison unit is sequentially compared with the state of the binarization signal output in the previous scan cycle stored in the storage unit, and the binarization signal of 4. The method for eliminating an interference state of a multi-optical axis photoelectric switch according to claim 3, wherein the state change is determined.

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