JP4550298B2 - Transmission type photoelectric switch - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transmissive photoelectric switch.
[0002]
[Prior art and problems to be solved by the invention]
This type of photoelectric switch has a plurality of pairs of light projectors and light receivers facing each other, projects pulsed light of a predetermined cycle from the light projecting elements on each projector side, and receives the light with the light receiving elements of the corresponding light receivers. Thus, it is detected whether or not each optical axis is in a light shielding state. In this case, there are two types of operation of the transmissive photoelectric switch, a synchronous type and an asynchronous type.
The synchronous transmission type photoelectric switch discriminates and detects only the light from the corresponding projector by opening the gate circuit of the light receiving circuit at the same period as the light emitting period of the light projecting element.
This means that in the synchronous system, a pulse signal is sent from the light projector side to the light receiver side, so that a synchronization cable must be wired from the light projector to the light receiver. Such wiring work is not only troublesome, but also has a problem that the circuit structure on the light receiver side becomes complicated. Also, depending on the installation location, it may not be possible to route the cable between the projector and the receiver, and the projector and the receiver must be operated with separate power supplies. In this case, the synchronous system cannot be adopted. There are also restrictions.
[0003]
On the other hand, the asynchronous type integrates the received light signal from the light receiving element, and discriminates whether or not the light from the corresponding projector is based on the fact that this integrated output reaches a predetermined level. A cable is unnecessary.
However, in such a transmission type photoelectric switch adopting the conventional asynchronous type, in order to increase the S / N ratio, an integration circuit having a relatively large time constant is required, and the response time is probably delayed. There was a problem that high-speed response could not be performed. In particular, when a plurality of such asynchronous transmission type photoelectric switches are used adjacent to each other, an interference phenomenon occurs in which not only the corresponding projector but also light from other projectors adjacent thereto is received. Therefore, there was a problem that normal detection could not be performed.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a transmissive photoelectric switch capable of high-speed response while being asynchronous.
[0004]
[Means for Solving the Problems]
To achieve the above object, a transmissive photoelectric switch according to the invention of claim 1 includes a plurality of pairs of light projectors and light receivers arranged in pairs, and the light projector includes a light projecting element and the light projecting element. The light receiving circuit includes a light receiving element that receives light from a light projecting element disposed opposite to the light receiving element, and a signal from the light receiving element. A light receiving circuit that outputs a light reception signal based on the gate, a gate unit that selectively activates the light reception signal by performing an opening and closing operation at a predetermined period, and a light incident state or a light shielding based on the signal validated by the gate unit In a transmissive photoelectric switch equipped with a detection means for detecting a state, the projector selects one of a plurality of different light projection periods and emits light projecting elements at different periods for each light projector Projection period setting for Means are provided, a gate means is provided with a plurality each of the respective photodetectors, each gate means by each of these gate means is controlled by a gate control means so as to perform the following operations (a) (e) To perform a synchronous light receiving operation corresponding to each projection cycle of each projector,
(A) Each gate means closes the gate when receiving a light reception signal from the light receiving circuit in the standby state, and then opens the gate at a different period corresponding to one of the light projection periods of each projector (b) When the light receiving signal is received at the timing when the gate is opened in (a), the means performs a synchronous light receiving operation that repeatedly opens and closes the gate in that cycle. (C) Each gate means performs the gate operation in (a). When the light receiving signal is not received at the timing of opening, the gate is opened to return to the standby state of (a). (D) Each gate means is pre-ranked, and the lower-ranked gate means is The upper gate means enters the standby state of (a) on the condition that the synchronous light receiving operation of (b) has been reached, and is stopped when the upper gate means is in the standby state of (a). (E) Each gate means opens the gate at a period other than the period of the synchronous light receiving operation of the upper gate means in (a) above. The projector set as a corresponding one of the gate means for performing the synchronous light receiving operation. It is characterized in that the detection means performs the detection operation based on the signal from the gate means taken out by the synchronization extraction means that validates only what is synchronized with the light projection period.
[0005]
According to a second aspect of the present invention, in the transmission type photoelectric switch according to the first aspect, the detection means integrates the output signal from the gate means validated by the synchronous extraction means, and the value is preset. When the reference level is reached, there is provided an integration determination means that operates so as to invert the output, and an interference detection means that detects that the synchronous light receiving operation is performed simultaneously with the other gate means in each gate means. The determination means is characterized in that, out of the output signals from the gate means, the output signal when the detection operation is performed by the interference detection means is invalidated.
[0006]
[Action and effect of the invention]
<Invention of Claim 1>
According to the structure of Claim 1, each light projector makes each light projection element light-emit with a mutually different period set by the light projection period setting means. Therefore, the light receiving element of each light receiver receives light with various periods of pulsed light from the projectors, and a plurality of types of pulses are mixed from the light receiving circuit based on the signal from the light receiving element. Received light signal is output.
At this time, by the gate control means, each gate means closes the gate when receiving a light reception signal from the light receiving circuit in the standby state, and then opens the gate at a different period corresponding to one of the light projection periods of each projector. (The operation of claim 1 (a)). For this reason, if a light receiving signal (pulse) is obtained when a certain gate means receives a certain pulse, closes the gate, and then opens the gate at a period corresponding to one of the light projecting periods of each projector, Then, a synchronous light receiving operation for repeatedly opening and closing the gate is performed in the cycle (operation (b) of claim 1).
Note that the gate means for which no light reception signal is obtained when the gate is opened again returns to the initial standby state (operation (c) of claim 1). The gate means that has returned to the standby state again receives the received light-receiving signal pulse, closes the gate, and then opens the gate at a period corresponding to one of the light projecting periods of each projector. Then, a light reception signal having a different light projection period different from that already found is found, and the process proceeds to the synchronous light reception operation.
[0007]
Here, each gate means is pre-ranked, and the lower-order gate means waits for the above (a) on condition that the higher-order gate means has reached the synchronous light receiving operation of (b). When the upper gate means enters the state and is in the standby state in (a) above, it is set so as to be stopped (operation (d) of claim 1), and each gate means is ) Is set so as to open the gate at a period other than the period of the synchronous light receiving operation of the upper gate means (operation (e) of claim 1), and eventually from one of the projectors in order from the upper gate means. The projected light reception signal is found.
And only the signal which synchronizes with the light projection period set beforehand as a corresponding thing among the signals from each gate means is validated, and detection operation is performed based on the signal.
[0008]
By the way, if only one gate means that synchronizes only with the light projection period set in advance is provided, the following problem occurs. That is, even if the gate is closed upon receiving a pulse in a standby state, and then the gate is opened at a preset light projection period, the next pulse may not be received at the timing when the gate is opened. This is because pulses of various periods are mixed in the light reception signal, and the pulses received when in the standby state are not necessarily of the set period. Therefore, when the next pulse is not received at the timing when the gate is opened, the gate is opened again to return to the “standby state”, and this operation must be repeated until a pulse having a set cycle is found. Although it is possible to find a pulse having a set period with a certain probability, it is necessary to repeat the above-described operation until it is found, and it takes time to establish synchronization with the projector.
On the other hand, in the present invention, as described above, a plurality of gate means are provided, and the light projection period of each light projecting element is found in parallel, so the time for establishing synchronization with the light projecting element is increased. The time can be drastically shortened, and high-speed operation can be achieved accordingly.
[0009]
<Invention of Claim 2>
According to the configuration of the second aspect, the integration determination unit integrates the output signal from the gate unit validated by the synchronization extraction unit, and inverts the output when the value reaches a preset reference level. . As a result, the output operation can be performed with the influence of noise removed, so that the S / N ratio can be improved.
Moreover, the light emission timing of each projector that emits light at different periods may coincide. In such a case, even when light from a projector corresponding to a certain light receiver is blocked, light from a light projector different from the light projector enters the light receiving element of the light receiver at the same timing. Interference will occur. Regardless of whether or not it is such instantaneous interference, in the case of a conventional one provided with an integration circuit, if an inverted signal is received during integration, the previous integration value is reset and restarted from the beginning. It was the composition which performs integral calculation. However, in the present invention, in each gate means, it is detected that the synchronous light-receiving operation is performed simultaneously with the other gate means by the interference detection means, that is, the light emission timings of the projectors corresponding thereto are coincident. And the integration is continued from the next output signal in which no interference occurs. As a result, high-speed response is possible without reducing the accuracy of the detection operation due to the interference.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
The transmissive photoelectric switch 10 according to the present embodiment has a projector V and a photoreceiver U arranged to face each other, and projects pulse light of a predetermined period from the light projecting element 11 on each projector V side. Asynchronous light received by the U light receiving element 13, integrated with the light reception signal from the light receiving element 13, and discriminating whether the light is from the corresponding projector V based on the integration output reaching a predetermined level. This is a transmission type photoelectric switch 10 of the type.
As shown in FIG. 1, the transmissive photoelectric switch 10 includes, for example, four sets of projectors V (reference numerals V1, V2, V3, and V4 in FIG. 1) and light receivers U (reference numerals U1, U2, and FIG. 1). U3, U4) are arranged in pairs. Each projector V includes a light projecting element 11, a light projecting circuit 12 that causes the light projecting element 11 to emit light with a pulse light having a predetermined period, and a light projecting circuit selected from a plurality of different light projecting periods. And a light projection period control means 1 (corresponding to “light projection period setting means” in claim 1). In the present embodiment, each projector 12 is configured so that each projector circuit 12 has a different projection cycle (cycle T [0], cycle T [1], cycle T [2], cycle T [3]). Adjustment is performed by the light projection cycle control means 1. In this embodiment, the cycle T [0] is set for the projector V1, the cycle T [1] is set for the projector V2, the cycle T [2] is set for the projector V3, and the cycle T [3] is set for the projector V4. Further, the length of each cycle has a relationship of cycle T [0] <cycle T [1] <cycle T [2] <cycle T [3].
[0011]
On the other hand, each light receiver U includes a light receiving element 13 that receives pulsed light from the light projecting element 11, a light receiving circuit 14 that outputs a light receiving signal corresponding to the amount of light received by the light receiving element 13, and
And a light receiving control means 2. The light receiving control means 2 receives a light receiving signal from the light receiving circuit 14 and makes a “synchronous light receiving operation routine” (“(a)-(e ) ”,“ Synchronization extraction routine ”(corresponding to“ synchronization extraction means ”in claim 1) and“ detection routine ”(“ integration determination means ”and“ interference detection means ”in claim 2). Corresponding).
[0012]
Next, the light receiver U1 will be described as an example with reference to a block diagram (FIG. 2) functionally showing the processing executed by the light reception control means 2.
As shown in the figure, each of the four gate means G (symbols G1, G2, G3, and G4 in the figure) receives light from the light receiving circuit 14 based on an operation shown in a “synchronous light receiving operation routine” to be described later. Enable the signal. Each gate means G is ranked in order from the gate means G1 to the gate means G4, and gives a stop signal to the lower gate means until the upper gate means reaches a “synchronous light receiving operation” described later, When "Synchronous light reception operation" is reached, the set cycle information (CH [X] X = 0,1,2,3) set to itself is given to the lower gate means and synchronized with the "Synchronous light reception operation". Then, a synchronous light reception notification signal is given to the synchronization extraction means 21 and the interference detection means 22 described below. Then, the synchronization extracting means 21 validates only the light receiving signals validated by the respective gate means G that are synchronized with a preset set period based on the operation shown in the “synchronous extraction routine” described later. This is given to the integral judgment means 23. In the present embodiment, the set period is a period set for the projector V arranged opposite to each light receiver U. For example, in the case of the light receiver U1, the period T [0] set for the projector V1. It is.
[0013]
The interference detection means 22 synchronizes with the set cycle T [0] set in the synchronization extraction means 21 based on the synchronous light reception operation notification signal output in synchronization with the “synchronous light reception operation” of each gate means G. Then, it is detected that the operation timing of the gate means for performing the “synchronous light receiving operation” coincides with the operation timing of the other gate means, and the interference detection signal is given to the integral determination means 23. Next, the integral determination unit 23 executes a “detection routine” described later based on the output signal from the synchronization extraction unit 21 and the interference detection unit 22 from the interference detection unit 22. The detection operation unit 24 performs a predetermined detection operation based on the output signal from the integration determination unit 23.
[0014]
The operational effect of this embodiment is shown in the flowchart of the program executed by the light reception control means 2 (in the functional block diagram of FIG. 2, the gate means G, the synchronous extraction means 21 and the integral determination means 23) (FIG. 3). This will be described with reference to FIGS. 4, 5, and 6) and timing charts (FIGS. 7 and 8).
First, when the respective power sources on the light projector V side and the light receiver U side of the transmissive photoelectric switch 10 in the present embodiment are turned on, the light projectors V have different periods (period T [0], period T [ 1], a cycle T [2], and a cycle T [3]), each light projecting element 11 is caused to emit light. Therefore, as shown in FIG. 1, the light receiving elements 13 of the respective light receiving devices U are received in a form in which pulse light having various periods from the projectors V are mixed, and based on the signals from the light receiving elements 13. The light receiving circuit 14 outputs a light receiving signal in which pulses having four periods are mixed.
[0015]
Here, for example, when the light reception control means 2 of the light receiver U1 receives a light reception signal from the light reception circuit 14, the "processing flow of the light reception control means 2" shown in FIG. 3 starts. In step S1, each gate means G executes a “synchronous light receiving operation routine” shown in FIG. In step S21, each gate means G determines whether or not it has received a stop signal from a higher-order gate means G, and if there is no stop signal, it opens the gate from “stop state” to “standby state”. enter. In step S22, when the light receiving signal is received from the light receiving circuit 14, the gate is closed and it is determined whether or not the set cycle information CH [0] is received from the higher gate means G. If not received, the gate is first opened with the shortest period T [0] (steps S23 and S24). When the light receiving signal is received from the light receiving circuit 14 in step S25, the lower period gate means G receives the set period information CH [ 0], and thereafter, a “synchronous light receiving operation” is performed in which the gate is repeatedly opened and closed at the period T [0], and the synchronous extraction unit 21 and the interference detection unit 22 perform synchronous light reception in synchronization with the “synchronous light reception operation”. A motion notification signal is given as needed (step S26).
In this embodiment, the “stop state” means that each gate means G receives a stop signal from the upper gate means G and closes the gate. However, the present invention is not limited to this. The state where the function of the gate means itself is stopped regardless of the open / closed state of the gate in response to the stop signal is included in the “stop state” according to claim 1.
[0016]
On the other hand, when the set cycle information CH [0] is received from the upper gate means G in step S24, or when the light reception signal is not received in step S25, the set cycle is received from the upper gate means G in steps S27 and S28. It is determined whether or not information CH [1] has been received. If not, the gate is opened at the next short cycle T [1] (after T [1] −T [0] has elapsed), and in step S29. When a light reception signal is received from the light receiving circuit 14, the set period information CH [1] is given to the lower gate means G, and thereafter, "synchronous light reception operation" is performed to repeatedly open and close the gate at the period T [1]. In synchronization with the “synchronous light reception operation”, a synchronous light reception motion notification signal is given to the synchronization extraction means 21 and the interference detection means 22 as needed (step S30).
[0017]
On the other hand, when the set cycle information CH [1] is received from the upper gate means in step S28, or when no light reception signal is received in step S29, the set cycle information CH [2] is updated in steps S31 and S32. If it is received, the gate is opened at the next short cycle T [2] (after T [2] −T [1] has elapsed), and when a light reception signal is received in step S33, the lower cycle gate means G receives the set cycle information. Then, CH [2] is given, and thereafter, the same processing as the above is performed, such as “synchronous light receiving operation” in which the gate is repeatedly opened and closed at the cycle T [2] (step S34).
Further, when the set cycle information CH [2] is received in step S32 or when the light reception signal is not received in step S33, if the set cycle information CH [3] is received in steps S35 and S36, When the gate is opened at the longest period T [3] (after T [3] −T [2] has elapsed) and a light reception signal is received in step S37, the gate is repeatedly opened and closed at that period T [2]. Processes similar to the above, such as “synchronous light reception operation”, are performed (step S38).
If the “synchronous light receiving / receiving operation” in any cycle is not reached in the above series of operations (steps S21 to S38), the initial “standby state” is restored.
[0018]
Each gate means G executes the above-mentioned “synchronous light receiving operation routine”, so that the light emitting period (period T [0], period T [1] from one of the projectors in order from the upper gate means G1 is finally obtained. , Period T [2], period T [3]) is performed in synchronization with each other, whereby each gate means finds a received light signal projected at a different period from each projector. Referring to the timing chart shown in FIG. 7, a light reception signal in which a plurality of cycles of pulses are mixed is output from the light receiving circuit 14 of the light receiver U <b> 1 due to light emission of the light projecting element 11 of each projector V (in FIG. 7, “Timing chart of output signal of light receiving circuit”). Here, for example, when the light receiving element 13 of the light receiver U1 receives light from the light projector V2, only the uppermost gate means G1 opens the gate as shown in “Operation of the gate G1” in FIG. In the “standby state”, the light receiving signal from the light receiving circuit 14 is received to close the gate. Then, the gate opening / closing operation is sequentially performed in order from the shortest cycle T [0]. The light reception signal is received again at the timing of the cycle T [1], and thereafter, the “synchronous light reception operation” is performed in the cycle T [1]. Next, the gate means G2 enters the “standby state” as shown in “Operation of the gate G2” in the figure, and when the light reception signal by the light emission of the projector V3 is received, the gate is closed and the gate means G1 is set. The gates are sequentially opened and closed with a period other than the period T [1]. At this time, the light receiving signal is received again at the timing of the cycle T [2], and thereafter, the “synchronous light receiving operation” is performed at the cycle T [2]. Similarly, for the gate means G3 and G4, the "synchronous light receiving operation" is sequentially performed in the cycle T [0] and the cycle T [3], respectively.
[0019]
Thus, in the present embodiment, as described above, the four gate means G find out the light projection period of each projector V in parallel, so that the time for establishing synchronization with the opposing projector V is set. The time can be drastically shortened, and high-speed operation can be achieved accordingly.
[0020]
Next, when the received light signal validated by each gate means G is given to the synchronization extraction means 21, the "synchronization extraction routine" shown in FIG. 5 is executed in step S2 of FIG. In step S41, whether or not the received light reception signal has the same cycle as the set cycle T [0] is determined based on the synchronous light reception motion notification signal given from each gate means G, and the same cycle. Only the received light signal is processed by the “detection routine” described below. In the present embodiment, in order to increase the accuracy of determining the “synchronous light reception operation”, the light reception signals from the respective gate means G are received at the same cycle as that of the “synchronous light reception synchronization”. (Steps S43, S44), and if not received, the period of the "synchronous light receiving operation" of the corresponding gate means G is cleared (step S45), and the original "standby state" again. It is configured to return to
[0021]
Further, in order to improve the accuracy of the synchronization extracting means 21, when a light reception signal having the same period as the set period is received, “1” is set in the integration counter (step S42), and the same as the light reception signals of other periods. Steps S43, S44, and S45 are executed at the same time, and the received light signals are counted (Steps S46 and S47), and the output signal is inverted when, for example, a predetermined count is reached eight times in succession (Step S48). , S49).
[0022]
Then, when the output signal is given from the synchronous extraction means 21 to the integration determination means 23, the “detection routine” shown in FIG. 6 is executed in step S3 of FIG.
In step S51, "0" is set in the integration counter, and the signal level of the received light signal is detected in synchronization with the set period T [0]. If the signal level is equal to or higher than the predetermined level, "YES" is determined, and the process returns to step S5. On the other hand, when the received light signal level is lower than the predetermined level, “NO” is counted (step S55), and when the received light signal is lower than the predetermined level, for example, 8 times continuously, the output is inverted. Then, the detection operation means 24 is provided and the period of the gate means for which the set period T [0] is set is cleared (steps S56, S57, S58).
With such a configuration, the influence of noise can be removed and the output operation can be performed, so that the S / N ratio can be improved.
[0023]
For example, as shown in FIG. 8, the light emission timing of the light projector V1 facing the light receiver U1 may coincide with the light emission timing of another light projector V3, for example. In such a case, the light from the projector V3 enters the light receiving element 13 of the light receiver V1 at the same timing even when the light from the normal projector V1 is blocked. Interference will occur. However, in this embodiment, when an interference detection signal is received from the interference detection means 22 in step S53, the counting is temporarily stopped, and the counting is continued from the light reception signal when the interference detection signal is not received. As a result, high-speed response is possible without reducing the accuracy of the detection operation due to the interference.
[0024]
<Other embodiments>
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.
[0025]
(1) In the above embodiment, four projectors V and four light receivers U are used. However, if there are a plurality of projectors V and light receivers U, more projectors V and light receivers U may be arranged. However, in this case, the number of setting cycles is required in accordance with the number of the projectors V.
(2) The light reception control means 2 of the above embodiment may be configured by a logic circuit or may be configured to be executed by a computer by a computer program.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a transmissive photoelectric switch according to an embodiment of the present invention. FIG. 2 is a functional block diagram for explaining processing of a light reception control unit. FIG. FIG. 5 is a flowchart showing a synchronous extraction routine. FIG. 6 is a flowchart showing a detection routine. FIG. 7 is a timing chart for explaining a synchronous light receiving operation routine. FIG. Timing chart [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Light projection period control means 2 ... Light reception control means 10 ... Transmission type photoelectric switch 11 ... Light projection element 12 ... Light projection circuit 13 ... Light reception element 14 ... Light reception circuit 21 ... Synchronization extraction means 22 ... Interference detection means 23 ... Integration determination Means 24 ... detection operation means G (G1, G2, G3, G4) ... gate means U (U1, U2, U3, U4) ... light receiver V (V1, V2, V3, V4) ... projector

Claims (2)

A plurality of pairs of light projectors and light receivers arranged in pairs,
The light projector includes a light projecting element and a light projecting circuit that emits the light projecting element at a predetermined light projecting cycle.
The light receiver has a light receiving element that receives light from the light projecting element disposed opposite thereto, a light receiving circuit that outputs a light receiving signal based on a signal from the light receiving element, and opens and closes at a predetermined cycle. Transmission means comprising a gate means for selectively enabling the light reception signal by performing an operation, and a detection means for performing an operation of detecting a light incident state or a light shielding state based on the signal enabled by the gate means Type photoelectric switch,
The light projector is provided with a light projection period setting means for selecting one of a plurality of different light projection periods and causing the light projecting element to emit light at a different period for each light projector.
Each of the light receivers is provided with a plurality of the gate means, and each of the gate means is controlled by the gate control means so as to perform the following operations (a) to (e). Synchronous light reception operation corresponding to each projection cycle of each projector is performed,
(A) Each gate means closes the gate when receiving the light reception signal from the light receiving circuit in a standby state, and then opens the gate at a different period corresponding to one of the light projection periods of the light projectors (b) ) When each gate means receives the light reception signal at the timing when the gate is opened in (a), the gate means performs a synchronous light receiving operation that repeatedly opens and closes the gate in that period. (C) Each gate means performs the above ( When the light reception signal is not received at the timing when the gate is opened in a), the gate is opened and the process returns to the standby state of (a). (d) Each gate means is pre-ranked and the rank is lower. The gate means enters the standby state of (a) on the condition that the upper gate means has reached the synchronous light receiving operation of (b), and the upper gate means enters the standby state of (a). (E) Each gate means opens the gate at a period other than the period of the synchronous light receiving operation of the upper gate means in (a) above. Transmission type characterized in that the detection means performs the detection operation based on the signal from the gate means taken out by the synchronization extraction means that validates only those that are synchronized with the light projection period of the projector set as Photoelectric switch. The detection means integrates the output signal from the gate means validated by the synchronization extraction means, and when the value reaches a preset reference level, the integration judgment means operates to invert the output. When,
In each of the gate means, interference detection means for detecting that the synchronous light receiving operation has been performed simultaneously with other gate means is provided,
The transmission type photoelectric switch according to claim 1, wherein the integration determination unit invalidates an output signal when a detection operation is performed by the interference detection unit, out of output signals from the gate unit.

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