JPH07264037A - Multiple optical axes photoelectric switch - Google Patents

Abstract

PURPOSE:To obtain a signal deciding a light shielding state when the time lag from a point of time when the optical axis of the light projected by a light projecting element is shielded is little by discriminating the light shielding state by the output of a logical means determining AND. CONSTITUTION:This switch is provided with a logical means determining the AND of the stored data of a memory M every time the memory M stores and is composed so that a light shielding state may be discriminated by the output of the logical means. Light is successively projected from plural light projecting elements 7a to 7d and the projected light is individually received by plural light receiving elements 8a to 8d. The presence or absence of the output of each of the light receiving elements 8a to 8d is discriminated and the data of the discrimination result is stored in the memory corresponded to the light receiving elements 8a to 8d. Every time the stored data of each memory M is inputted in the logical means and the data of the discrimination result is stored in the memory M, an AND is determined. When the light projected by the light projecting elements 7a to 7d are shielded, the logic of the logical means is not established. Thus, at the point of time when the projected light is shielded, a state can be decided as the light shielding state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-optical axis photoelectric switch for sequentially projecting light from a plurality of light projecting elements and individually projecting light to a plurality of light receiving elements.

[0002]

2. Description of the Related Art A multi-optical axis photoelectric switch is used, for example, as a safety device for a press machine because it can detect the presence or absence of an object in a wide area. A multi-optical axis photoelectric switch of this type is disclosed in, for example, Japanese Utility Model Laid-Open No. 4-19830, and this multi-optical axis photoelectric switch projects light from a plurality of light emitting elements in sequence to obtain a plurality of light receiving elements. The projection scanning for sequentially projecting light is repeated. And, depending on the presence or absence of the output of the light receiving element,
The presence / absence of an object blocking the light from the light projecting element is detected between the light projecting element and the light receiving element. Then, at the time point when one scanning of the light projecting scanning is completed, whether the optical axis of the light projected by the light projecting element is shielded based on the output of each light receiving element within the period of one scanning of the light projecting till then. It is determined whether or not.

[0003]

As described above, in the conventional multi-optical axis photoelectric switch, each time one scan of the light projection is completed,
It is determined whether the light projecting element blocks the optical axis of the projected light. Therefore, for example, even if the optical axis of the first projected light is blocked, the light blocking state of the optical axis is kept until it is detected whether or not each of the optical axes of the subsequently projected light is blocked. The judged signal cannot be obtained. Therefore, there is a time difference between the time when the optical axis is shielded and the time when a signal that determines whether the optical axis is shielded is obtained. As a result, there is a problem that a signal for determining that the optical axis is shielded cannot be obtained when the optical axis is shielded. In view of such a problem, the present invention provides a multi-optical axis photoelectric switch capable of obtaining a signal for determining a light blocking state at a time when there is little time delay from the time when the light projecting element blocks light on the optical axis of the projected light. The purpose is to

[0004]

A multi-optical axis photoelectric switch according to a first aspect of the present invention sequentially projects light from a plurality of light projecting elements and a plurality of light receiving elements individually receives the light, and the order of projecting the light is determined. In the multi-optical axis photoelectric switch that selects the output of the light receiving element according to the selected output and detects the light blocking state between the light emitting element and the light receiving element based on the selected output, it is possible to determine whether the output of the light receiving element is present or not. Means, a plurality of storage means for storing data based on the determination result of the determination means in association with the light receiving element, and a logic means for obtaining a logical product of the storage data of the storage means each time the storage means stores the data. It is characterized in that it is configured to discriminate the light-shielded state by the output of the logic means.

In the multi-optical axis photoelectric switch according to the second aspect of the present invention, light is sequentially projected from a plurality of light projecting elements to be individually received by a plurality of light receiving elements, and the outputs of the light receiving elements are output according to the order of light projection. In the multi-optical axis photoelectric switch for detecting the light blocking state between the light emitting element and the light receiving element by the selected output,
A binarization circuit for discriminating the presence / absence of the output of the light receiving element,
A plurality of flip-flop circuits provided corresponding to the light receiving elements, to which the binarized signal output from the binarized circuit should be input;
Each time the flip-flop circuit latches a binarized signal, a logic circuit that obtains a logical product of the outputs of the flip-flop circuit is provided, and the light-shielded state is determined by the output of the logic circuit. And

[0006]

In the first aspect of the invention, light is sequentially projected from a plurality of light projecting elements, and the plurality of light receiving elements individually receive the projected light. The presence or absence of the output of each light receiving element is determined, and the data of the determination result is stored in the storage means corresponding to the light receiving element.
The storage data of each storage means is input to the logic means, and the logical product is obtained each time the data of the discrimination result is stored in the storage means. When the light projected by the light projecting element is blocked, the logic of the logic means is not established. Thus, when the light projected by the light projecting element is shielded, it can be determined that the light is in the shielded state.

In the second invention, a plurality of light projecting elements are sequentially arranged.
Light is projected, and the plurality of light receiving elements individually receive the projected light. The output of each light receiving element is binarized, and the binarized signal is sequentially latched by the flip-flop circuit corresponding to the light receiving element. Each time the output of the flip-flop circuit is input to the logic circuit and the binarized signal is latched, the logical product of them is obtained. When the light projected by the light projecting element is blocked, the logic of the logic circuit is not established. This makes it possible to determine that the light is blocked when the light projected by the light projecting element is blocked.

[0008]

The present invention will be described in detail below with reference to the drawings showing the embodiments thereof. FIG. 1 is a block diagram showing the configuration of a multi-optical axis photoelectric switch according to the present invention implemented by software. The light projecting elements 7a, 7b, 7c, 7d are adapted to sequentially project light signals. The output signals of the light receiving elements 8a, 8b, 8c, 8d that receive the optical signals from the light projecting elements 7a, 7b, 7c, 7d are individually input to the amplifier circuits 9a, 9b, 9c, 9d. Amplifier circuits 9a, 9b,
The output signals of 9c and 9d are input to the light receiving element switching circuit 10.
The output signal of the amplification circuit selected by the switching operation of the light receiving element switching circuit 10 is input to the main amplification circuit 11, and the output signal thereof is input to the binarization circuit 12.

The binarized signal output from the binarization circuit 12 is input to the CPU 20 having the memory M and the counter C built therein. The signal output from the CPU 20 is output via the output circuit 15. The output current monitor signal OVC output from the output circuit 15 is input to the CPU 20. The clock CLK output from the clock generation circuit 17 is input to the CPU 20. CP
The control signal CON output from U 20 is the amplification circuit 9a, 9b, 9c, 9
It is given to the control terminal of d and the light receiving element switching circuit 10. CP
In the memory M built in U 20, the light receiving elements 8a, 8b, 8c, 8
There are four storage areas associated with d. Further, the counter C performs a counting operation that repeats counting from "1" to "4". The storage area of the memory M is designated by the count value of the counter C.

Next, the operation of the multi-optical axis photoelectric switch configured as described above will be described with reference to the flowchart of FIG. 2 showing the control contents of the CPU. Now, when light signals are emitted from the light projecting elements 7a, 7b, 7c, 7d in this order, the light receiving elements 8a, 8a
b, 8c, 8d receive the optical signals emitted by the light projecting elements 7a, 7b, 7c, 7d in that order, and the output signals of the light receiving elements 8a, 8b, 8c, 8d are amplified by the amplifier circuits 9a, 9b, 9c, Input to 9d. Control signal from CPU 20
When CON is given to the amplifier circuits 9a, 9b, 9c, 9d and the light receiving element switching circuit 10, the amplifier circuits 9a, 9b, 9c, 9d start the amplifying operation. Then, the output signals of the light receiving elements 8a, 8b, 8c, 8d are amplified by the amplifier circuit 9
It is amplified by a, 9b, 9c and 9d, and the output signal is input to the light receiving element switching circuit 10.

The light receiving element switching circuit 10 synchronizes with the light signal projected by the light projecting elements 7a, 7b, 7c, 7d by the control signal supplied from the CPU 20, and outputs light from the amplifier circuits 9a, 9b, 9c, 9d. The output signal is selected and input to the main amplifier circuit 11. And the main amplifier circuit
The output signal amplified by 11 is input to the binarization circuit 12
It is digitized and the binarized signal is input to the CPU 20. That is, the light signals projected from the light projecting elements are amplified in the order of the light projecting elements 7a, 7b, 7c, 7d, and the binarized signal is input to the CPU 20 in time series.

Therefore, the CPU 20 first writes "0" in all the storage areas of the memory M (S0). Then, the count value of the counter C is reset to "1" (S1). Then CPU 20
Check the binarized signal output by the binarization circuit 12 and, for example, the binarized signal corresponding to the output signal of the light receiving element 8a is "1".
It is determined whether or not (S2). Here, the binarized signal is "1" when the light axis of the light projected by the light projecting element 7a is not shielded, and is "0" when the light is shielded. If it is determined here that the optical axis of the light receiving element 8a is shielded and the binary signal is "0", the binary signal "0" is stored in the storage area designated by the count value "1" of the counter C. Write (S
3). That is, the data of the output signal of the light receiving element 8a is written in the storage area.

Then, the logical product of the storage data in each storage area of the memory M is obtained (S4). And the result of the logical product is "1"
It is determined whether or not (S5). Here, only the data is written in one storage area, and the logical product with “0”, “0”, “0” written in the other memory is obtained, and the result of the logical product is “ If it is judged as "0", the output circuit from the CPU 20
Output "0" signal to 15 (S6), and output circuit 15 outputs "0"
Output the detection signal S of. Then, it is determined whether the count value of the counter C is "4" or more (S7). If it is determined that the count value is "4" or more, the process returns to step (S1) to reset the counter C. .

However, since the count value is "1" here, it is determined that the count value is less than "4", the count value is incremented (S8), and the count value becomes "2". Subsequently, the CPU 20 checks the binarized signal and detects the light receiving element.
It is determined whether the binarized signal which is the output signal of 8b is "1" (S2). Here, when the optical axis of the light projecting element 7b is not shielded, the binarized signal becomes "1". When it is determined that the binarized signal is "1", the binarized signal "1" is stored in the storage area designated by the count value "2" of the counter C.
Write the data of (S9). That is, the data of the output signal of the light receiving element 8b is written in the storage area. Then, the logical product of the storage data in each storage area is obtained (S4). Then, it is determined whether or not the result of the logical product is "1" (S5). The data respectively written in the two storage areas are "0" and "1", and the logical product with "0" and "0" written in another memory is obtained.

When the result of the logical product is judged to be "0",
The CPU 20 outputs a "0" signal to the output circuit 15 (S6), and the output circuit 15 outputs a "0" detection signal S. Subsequently, when it is determined that the count value is less than "4" (S7), the count value is incremented (S8), and the count value is set to "3". Similarly to the above, it is determined whether the binarized signal which is the output signal of the light receiving element 8c is "1", and the determined data is written in the storage area corresponding to the count value. Then, the logical product of the stored data is calculated, and the detection signal S corresponding to the result of the logical product is output. Then, the count value is incremented to set the count value to "4". Then, it is determined whether the binarized signal which is the output signal of the light receiving element 8c is "1", the determined data is written in the storage area corresponding to the count value, and the logic of the storage data in each storage area is determined. The product is obtained, and the detection signal S corresponding to the result of the logical product is output. Then, when one scanning of the light-projecting scanning is completed and only the optical axis of the light-projecting element 7a is shielded in the period of the one scanning, the data written in the storage area corresponding to the count value is "0", "1", "1", "1", and the detection signal S becomes "0", "0", "0", "0".

As described above, the optical axis of the light projecting element 7a is shielded during the first one scanning period of the light projecting scanning for projecting light in the order of the light receiving elements 8a, 8b, 8c, 8d. At that time, the detection signal S becomes "0", and it is determined that the optical axis is in the light-shielded state. Then, as described above, when the data of the output signals of the light receiving elements 8a, 8b, 8c, 8d is written in each storage area by one scanning of the light projecting scanning, the counter C is incremented and the counter C is incremented.
When it is determined that the count value of is 4 or more (S7), the count value of the counter C is reset and the count value becomes 1 (S1).

Next, in the second scanning of the light projecting scanning, when the optical axis of the light projecting element 7a is not blocked, the light receiving element 8a receives the optical signal from the light projecting element 7a, The binarized signal which is the output signal becomes "1". Therefore, it is determined whether or not the binarized signal is "1" (S2), and when it is determined that it is "1", "1" of the binarized signal is stored in the storage area designated by the count value "1". Write "(S9). As a result, the storage data in the storage area changes from "0", "1", "1", "1" to "1", "1", "1", "1". Then, the logical product of the storage data of each storage area is obtained (S4), and it is determined whether the logical product result is "1" (S5). If the stored data is changed and it is determined that the logical product result is “1”, CP
The output signal of “1” is output from U 20 to the output circuit 15 (S1
0). Then, the output circuit 15 outputs the detection signal S of "1". Subsequently, as described above, it is determined whether or not the count value of the counter C is equal to or greater than "4", and if it is determined to be less than "4" (S7), the count value is incremented (S7).
8), the count value becomes "2". As a result, when the optical axis is no longer shielded, the detection signal S becomes "1", and it is determined that the optical axis is not in the shielded state. As described above, it is determined whether the binarized signal which is the output signal of the light receiving elements 8a, 8b, 8c, 8d is "1" and the data of the determination result is written in the storage area. .

When the optical axis of the light projecting element 7c is shielded, the binarized signal becomes "0", the data is written in the storage area, and the logical product result of the data in each storage area is obtained. Is determined to be "0", and the detection signal S becomes "0". In this way, the latest determination of each optical axis including the previous scan is made without waiting for the determination result of whether or not each optical axis of the light projecting elements 7a, 7b, 7c, 7d in the same scan is shielded. Since the determination is based on the result, it is possible to reduce the delay in the determination result with respect to the actual light-shielded state.

FIG. 3 is a block diagram showing the configuration of a multi-optical axis photoelectric switch according to the present invention implemented by hardware. The light receiving elements 8a, 8b, 8c, 8d individually receive the light pulse signals which the light projecting elements 7a, 7b, 7c, 7d sequentially and repeatedly project. The outputs of the light receiving elements 8a, 8b, 8c, 8d are individually input to the amplifier circuits 9a, 9b, 9c, 9d, and the respective outputs are input to the light receiving element switching circuit 10 for selecting the light receiving elements. The signal output from the light receiving element switching circuit 10 is input to the main amplification circuit 11, and the output signal of the main amplification circuit 11 is input to the binarization circuit 12.

The binarized signal S1 output from the binarization circuit 12
Is input to the input terminal D of the first-stage D flip-flop circuit (hereinafter referred to as flip-flop) 30, and the output of the output terminal Q of the flip-flop 30 is the second-stage flip-flop.
It is input to the input terminal D of 31 and the output of its output terminal Q is 3
It is input to the input terminal D of the flip-flop 32 of the stage.
The output terminal Q of the flip-flop 32 is input to the input terminal D of the fourth-stage flip-flop 33. The output terminals Q of the flip-flops 30, 31, 32 and 33 are input to the 4-input AND circuit 34. , Its output is input to the input terminal D of the flip-flop 35.

The control signal CON output from the detection timing control circuit 36 is applied to the control terminals of the amplifier circuits 9a, 9b, 9c and 9d and the light receiving element switching circuit 10. The reset signal RST output from the detection timing control circuit 36 is given to each reset terminal R of the flip-flops 30, 31, 32, 33, 35,
The timing signal TM ₁ is given to the clock terminals CL of the flip-flops 30, 31, 32, 33. Also the timing signal TM ₂
Is applied to the clock terminal CL of the flip-flop 35.
The detection signal S is output from the output terminal Q of the flip-flop 35. The clock CLK output from the clock generation circuit 17 is input to the detection timing control circuit 36. The flip-flops 30, 31, 32, and 33 are light receiving elements 8a, 8b, 8c, and 8d.
The same number is provided corresponding to.

Next, the operation of the multi-optical axis photoelectric switch configured as described above will be described with reference to FIG.
Will be explained together. First, the detection timing control circuit 36 outputs a reset signal RST as shown in FIG. As a result, the flip-flops 30, 31, 32, 33 and 35 are all reset. Now, when the light emitting elements 7a, 7b, 7c, 7d sequentially and repeatedly emit light pulse signals, the light receiving elements 8a, 8b, 8c, 8d
Each d receives the optical pulse signal. The pulse signal received from the optical pulse signal is input to the amplifier circuits 9a, 9b, 9c, 9d. The amplification circuits 9a, 9b, 9c, 9d perform amplification operation according to the control signal CON provided from the detection timing control circuit 36,
The pulse signals input to the amplifier circuits 9a, 9b, 9c, 9d are amplified and input to the light receiving element switching circuit 10. Light receiving element switching circuit 10
Is synchronized with the amplification operation of the amplification circuits 9a, 9b, 9c, and 9d by the control signal CON from the detection timing control circuit 36.
The pulse signals from a, 9b, 9c and 9d are sequentially selected and input to the main amplifier circuit 11 in time series.

The pulse further amplified by the main amplifier circuit 11
The binary signal is input to the binarization circuit 12 and binarized.
The binarized signal S1 is sequentially flipped as shown in FIG. 4 (c).
Input to the flop 30. This gives the result shown in Figure 4 (b).
Timing signal TM₁Rise time t₁Flip flip
Latches the first binarized signal S1 input to
The force terminal Q is inverted to "1" as shown in FIG. Continued
And the second binary signal S1 is input to the flip-flop 30.
Timing signal TM₁Rise time t ₂Pretend
The flip-flop 30 latches the binarized signal S1 and
The output terminal Q remains "1" and the flip-flop
31 latches the output signal of flip-flop 30 and
Output terminal Q is inverted to "1" as shown in Fig. 4 (e).
It

Similarly, the third and fourth binarized signals S1
Is input to the flip-flop 30, the flip-flop 3 is turned on at the rising times t ₃ and t ₄ of the timing signal TM _1.
The output terminals Q of 2, 33 are inverted to "1" as shown in FIGS. 4 (f) and 4 (g). As a result, each output terminal Q of the flip-flops 30, 31, 32, 33 becomes "1", the logic of the AND circuit 34 is established, its output becomes "1", and it is input to the flip-flop 35. Then, following the rising fulcrum t ₄ of the timing signal TM ₁ , as shown in FIG.
At the time t ₅ when ₂ rises, the output terminal Q of the flip-flop 35 is inverted to "1" as shown in FIG. 4 (i), and the flip-flop 35 outputs the detection signal S of "1". This makes it possible to determine that the light emitted from the light projecting elements 7a, 7b, 7c, 7d is not blocked. Then, the binarized signal continues until the 7th shot.
If S1 is input, the output terminals Q of the flip-flops 30, 31, 32, 33 remain inverted to "1" as described above.

By the way, when the light pulse signals for projecting the light projecting elements 7a, 7b, 7c, 7d in this order are shielded in the second scanning of the light projecting elements 7a, 7b, 7c, 7d, Light receiving element 8a, 8
b, 8c, 8d no longer receive the optical pulse signal from the light projecting element 7d, whereby the binarized signal S1 after the seventh binarized signal S1 disappears as shown in FIG. 4 (c). . Thereby,
The rising time t ₆ of the timing signal TM _1, the output terminal Q of the flip-flop 30 will be inverted to "0" as shown in FIG. 4 (d). Then flip-flops 30, 31,
Output terminals Q of 32 and 33 are "0", "1", "1", "1"
The logic of the AND circuit 34 is not established, and its output is inverted to "0".

Then, the rising time t of the timing signal TM _1
4 at the timing t ₇ when the timing signal TM ₂ rises, following ₆
As shown in (i), the output terminal Q of the flip-flop 35 is inverted to "0" and the flip-flop 35 outputs the detection signal S of "0". As a result, it can be determined that the light projected from the light projecting elements 7a, 7b, 7c, 7d is blocked. In this way, when the optical axis of the light projecting element 7d is shielded, it is possible to detect that the light shielding state has been entered.

When the outputs of the flip-flops 30, 31, 32, 33 are "0", "1", "1", "1",
After that, until the "1" signal of the binarized signal S1 is continuously input to the flip-flop 30 four times, the logic of the AND circuit 34 remains unsatisfied and the fourth binarized signal is input. Then, the logic is established and the flip-flop 35 outputs the detection signal S of "1". Therefore, when the light blocking of the optical axis is released, it cannot be detected that the light blocking is released at that time, but the determination can be made on the safe side and the determination of the light blocking state is not hindered. In this embodiment, four light emitting elements and four light receiving elements are provided, but this is merely an example, and the number is not limited at all.

[0028]

As described in detail above, in the first aspect of the invention, the plurality of light projecting elements sequentially determine whether or not the output of the light receiving element for receiving the projected light is determined by the determining means. Store the data based on the storage means corresponding to the light receiving element,
Each time it is stored, the logical product of the data stored in each storage means is obtained, and the light shielding state is determined by the output of the logical means for which the logical product is obtained. Therefore, when the light from the light projecting element is shielded, the light is received. When the output of the element disappears and the logic of the logic means is not established, it can be determined that the light is shielded when the light is shielded. Thus, it is possible to provide a multi-optical axis photoelectric switch that can output a signal determined to be in a light-shielded state with a small time delay from the time of light-shielding.

According to a second aspect of the invention, a flip-flop circuit in which the output of a light receiving element for receiving light projected by a plurality of light emitting elements is converted into a binarized signal and the binarized signal is associated with the light receiving element. Each time, the output of each flip-flop circuit is input to the logic circuit, and each time the binarized signal is latched, the logical product of them is calculated to determine the light blocking state of the light projected by the light projecting element. Therefore, when the light from the light projecting element is shielded, the output of the light receiving element disappears, the logic of the logic circuit becomes unsatisfied, and when the light is shielded, it can be determined that it is in the light shielding state. This makes it possible to provide a multi-optical axis photoelectric switch that outputs a signal for determining the light-shielded state with a small time delay from the time of light-shielding.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a multi-optical axis photoelectric switch according to the present invention.

FIG. 2 is a flowchart showing the control contents of the CPU.

FIG. 3 is a block diagram showing a configuration of a multi-optical axis photoelectric switch according to the present invention.

FIG. 4 is a timing chart of signals of respective parts.

[Explanation of symbols] 7a to 7d Light emitting element 8a to 8d Light receiving element 20 CPU 30 to 33 Flip-flop circuit 34 AND circuit 35 Flip-flop circuit M memory C counter

Claims (2)

[Claims] 1. A plurality of light emitting elements sequentially emit light, and a plurality of light receiving elements individually receive the light. The output of the light receiving element is selected according to the order of the light emission, and the output is selected by the selected output. In a multi-optical axis photoelectric switch that detects a light blocking state between an optical element and a light receiving element, a determining unit that determines whether the output of the light receiving element is present or not, and data based on the determination result of the determining unit to the light receiving element. A plurality of storage means correspondingly stored, and a logic means for obtaining a logical product of the storage data of the storage means each time the storage means stores the storage means are configured to determine the light shielding state by the output of the logic means. A multi-optical axis photoelectric switch, which is characterized in that 2. A plurality of light emitting elements sequentially emit light, and a plurality of light receiving elements individually receive the light. The output of the light receiving element is selected according to the order of light emission, and the selected output is used. In a multi-optical axis photoelectric switch for detecting a light blocking state between an optical element and a light receiving element, a binarizing circuit for discriminating presence / absence of an output of the light receiving element, and a binarizing circuit output by the binarizing circuit A plurality of flip-flop circuits, which are provided corresponding to the light receiving elements, to which a signal is to be input, and a logic circuit that obtains a logical product of the outputs of the flip-flop circuits each time the flip-flop circuit latches the binarized signal are provided. A multi-optical axis photoelectric switch, characterized in that the multi-optical axis photoelectric switch is provided so as to determine a light-shielding state by an output of the logic circuit.