JP2004333173A - Multi-optical axis photoelectric sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-optical axis photoelectric sensor for avoiding an increase in the size of a light source or a light receiving unit, and for detecting incident light/shielded light with optimum detection sensitivity for each light axis. <P>SOLUTION: The multi-optical axis photoelectric sensor has an output means for outputting a digital output signal D' to an external equipment 10 according to the quantity of received light by respective light receiving elements 12a-12d detected by a light reception operation. Accordingly, a user can adjust a reference value for detecting incident light/shielded light for each of respective light axes N1-N4 in the external equipment 10 by operating the external equipment 10 and can detect incident light/shielded light. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention has a plurality of light emitting elements and a plurality of light receiving elements, and detects light entering / shading of each optical axis formed by each of the light emitting elements and the light receiving elements based on the amount of light received by each light receiving element. The present invention relates to an axial photoelectric sensor.
[0002]
[Prior art]
This type of multi-optical axis photoelectric sensor is, for example, a light emitter having a plurality of light emitting elements, and a light receiver having a plurality of light receiving elements that are arranged to face each other with the light emitting element and the detection area interposed therebetween and form a pair with each light emitting element. It has. The multi-optical axis photoelectric sensor sequentially emits light from each of the light emitting elements, sequentially activates light receiving signals from the light receiving elements forming a pair with the light emitting elements, and, for example, compares the activated light receiving signals with a comparator. By comparing with a predetermined reference value, light incident / shielding of each optical axis formed by the light emitting element and the light receiving element forming a pair is detected. Then, a signal corresponding to the detection result of the light incident / shielding is output to an external device such as a control device or the like, or an operation indicator light provided in the light receiver performs a lighting operation. .
[0003]
By the way, the characteristics of the light projecting element and the light receiving element vary, and in the configuration in which the detection of light incidence / shielding is performed on the basis of the same reference value for each optical axis, the detection sensitivity varies for each optical axis. Detection may be caused.
[0004]
To cope with this problem, a predetermined reference value that satisfies the optimum detection sensitivity is provided for each optical axis, and a detection signal corresponding to the result of detection of light input / shielding for each optical axis is output to the outside. There is a configuration (see Patent Document 1 below).
[0005]
[Patent Document 1]
Published Japanese Utility Model Application No. Hei 3-60005
[Problems to be solved by the invention]
However, the cause of the variation in detection sensitivity for each optical axis is not limited to the above-described variation in element characteristics. That is, for example, the environment in which the multi-optical axis photoelectric sensor is used may be a cause. Specifically, for example, a case in which light that is brighter than other light receiving elements enters some of the plurality of light receiving elements from the surroundings, or a case in which some of the plurality of optical axes This is the case where water or the like is sprayed on. In such a case, with the above-described configuration in which a fixed reference value is provided for each optical axis, an optimum detection sensitivity cannot be obtained.
[0007]
Therefore, for example, a configuration is conceivable in which an adjusting means such as a volume is provided on the light receiving device side, and a user who actually uses the multi-optical axis photoelectric sensor adjusts a reference value corresponding to each optical axis according to a use environment. . However, in such a configuration, a component such as a volume, which constitutes an adjusting unit, is required, which may hinder the increase in the number of components and the miniaturization of the multi-optical axis photoelectric sensor. Also, for example, some multi-optical axis photoelectric sensors are required to have water resistance depending on the use environment. For such a case, if a configuration using a volume as an adjusting means is used, the volume and the light receiver main body are used. There is a danger that water will be immersed in the space between them, and it is not desirable because more parts are required to deal with the water.
[0008]
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to make it possible to detect incident / shielded light with optimal detection sensitivity for each optical axis while suppressing an increase in the size of a projector or a receiver. To provide a multi-optical axis photoelectric sensor.
[0009]
[Means for Solving the Problems]
As a means for achieving the above object, a multi-optical axis photoelectric sensor according to the invention of claim 1 includes a light emitter and a light receiver that are arranged to face each other, and the light emitter includes a plurality of light emitting elements, Light-projecting control means for sequentially causing the plurality of light-projecting elements to perform a light-projecting operation; and the light-receiving device includes a plurality of light-receiving elements forming a pair with each of the plurality of light-projecting elements, and A multi-axis photoelectric sensor comprising: a light receiving control means for performing a light receiving operation for sequentially detecting a light receiving amount of each of the light receiving elements in a predetermined order in synchronization with the operation. It is characterized in that it comprises an output means capable of outputting an output signal corresponding to the amount of light received by each of the light receiving elements to an external device.
[0010]
A multi-optical axis photoelectric sensor according to a second aspect of the present invention is characterized in that, in the first aspect, the output means outputs the output signal as a digital signal.
[0011]
A multi-optical axis photoelectric sensor according to a third aspect of the present invention is the multi-optical axis photoelectric sensor according to the first or second aspect, wherein the output means outputs an output signal corresponding to each of the light receiving elements via a common output terminal. It has the feature that it outputs sequentially.
[0012]
A multi-optical axis photoelectric sensor according to a fourth aspect of the present invention is the multi-optical axis photoelectric sensor according to any one of the first to third aspects, wherein the output means are set to different reference levels and detected by the light receiving control means. A plurality of comparing means for comparing the amount of received light with the respective reference levels, and the light receiving amount of each light receiving element based on a comparison result of the plurality of comparing means becomes any of predetermined multi-level levels And a level determining means for outputting an output signal corresponding to the determination.
[0013]
Function and effect of the present invention
<Invention of claim 1>
According to this configuration, an output signal corresponding to the amount of light received by each light receiving element is output to the external device. Therefore, the user side captures these output signals into an external device such as a personal computer, and adjusts the reference value for detecting the light input / shielding for each optical axis in the external device, while controlling the light input / output. It is possible to detect light shielding.
[0014]
<Invention of Claim 2>
According to this configuration, since the output signal output from the output unit is a digital signal, it has higher noise resistance than an analog signal, and an accurate output signal corresponding to the amount of light received by each light receiving element. Can be given to an external device.
[0015]
<Invention of Claim 3>
According to this configuration, output signals corresponding to the respective light receiving elements are sequentially output via the common output terminal. Therefore, it is possible to output a plurality of output signals corresponding to each of the light receiving elements to an external device via one signal line, thereby reducing the number of wirings, reducing costs and simplifying wiring work. Can be achieved.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, a multi-optical axis photoelectric sensor according to the present invention is connected to a light projector 11 in which, for example, four light emitting elements (for example, LEDs) 11a to 11d are arranged in a line, and is connected to the light projector 11 by a cable L1. Then, the light receiving device 12 in which, for example, four light receiving devices (for example, photodiodes) 12a to 12d are paired with each of the four light emitting devices 11a to 11d of the light emitting device 11 with a predetermined detection area interposed therebetween. It is configured to be opposed.
[0017]
(1) Electrical configuration of multi-optical axis photoelectric sensor FIG. 2 shows the electrical configuration of the multi-optical axis photoelectric sensor.
The projector 11 is provided with driving circuits 13a to 13d for lighting the above-described light projecting elements 11a to 11d, respectively. When the driving circuits 13a to 13d receive the ON signals P1 to P4 from the AND circuits 14a to 14d, the driving circuits 13a to 13d A drive current is supplied to each of the continuous light emitting elements 11a to 11d. Each of the AND circuits 14a to 14d has one input terminal connected to the light-emitting side CPU 15, and receives a light-emitting timing signal P0 sequentially output from the light-emitting side CPU 15 at a predetermined timing. The other input terminals are connected to four output terminals of the shift register 16, respectively. Each time the shift register 16 receives the shift signal S0 from the light emitting side CPU 15, the shift register 16 switches the output terminal for outputting the signal, and operates so as to sequentially apply the shift output signals S1 to S4 to the AND circuits 14a to 14d.
[0018]
With the above configuration, when both input terminals of each of the AND circuits 14a to 14d receive the light emitting timing signal P0 and the shift output signals S1 to S4 at the same time, the corresponding drive circuits 13a to 13d send the ON signal P1 To P4 to cause the light emitting elements 11a to 11d connected thereto to perform the light emitting operation.
[0019]
On the other hand, the light receiver 12 is provided with light receiving circuits 17a to 17d that amplify the respective signals from the light receiving elements 12a to 12d and output analog light receiving signals A1 to A4 corresponding to the amounts of received light. The outputs of the light receiving circuits 17a to 17d are commonly connected to signal lines via switch elements 18a to 18d, and the signal lines are connected to the input side of the A / D converter 19. Each of the switch elements 18a to 18d performs an ON operation by receiving ON signals G1 to G4 from the AND circuits 21a to 21d, respectively, and sequentially activates the analog light receiving signals A1 to A4 from the light receiving circuits 17a to 17d.
[0020]
One of the input terminals of the AND circuits 21a to 21d is connected to the light receiving side CPU 22, and the light receiving side sequentially output from the light receiving side CPU 22 at a predetermined timing (timing synchronized with the above light emitting timing; hereinafter, referred to as "light receiving timing"). The timing signal G0 is input. The other input terminals are connected to four output terminals of the shift register 23, respectively. Each time the shift register 23 receives the shift signal T0 from the light receiving side CPU 22, the shift register 23 operates to switch the output terminal for outputting the signal, and to sequentially apply the shift output signals T1 to T4 to the AND circuits 21a to 21d.
[0021]
With the above configuration, when both input terminals of the AND circuits 21a to 21d simultaneously receive the light receiving timing signal G0 and the shift output signals T1 to T4, the analog light receiving signals from the corresponding light receiving circuits 17a to 17d. A1 to A4 are sequentially supplied to the A / D converter 19. The A / D converter 19 converts the received analog light receiving signals A1 to A4 into a digital light receiving signal D, and outputs the converted digital light receiving signal D to the light receiving side CPU 22.
[0022]
<Processing operation of light emitting CPU and light receiving CPU>
When the multi-optical axis photoelectric sensor is activated, the light emitting side CPU 15 outputs a synchronization signal D0 to the light receiving side CPU 22 via the cable L1, and subsequently, sequentially transmits the light emitting timing signal P0 to the AND circuits 14a to 14d. Output. In synchronization with this, the light emitting side CPU 15 sequentially outputs the shift signal S0 to the shift register 16. As a result, the shift register 16 operates so as to switch the four output terminals and sequentially apply the shift output signals S1 to S4 to the AND circuits 14a to 14d. When the drive signals output from the AND circuits 14a to 14d are applied to the corresponding drive circuits 13a to 13d, the light emitting elements 11a to 11d sequentially emit light at the above light emitting timing.
[0023]
On the other hand, when receiving the synchronization signal D0 from the light-emitting side CPU 15, the light-receiving side CPU 22 sequentially outputs a light-receiving timing signal G0 to the AND circuits 21a to 21d. In synchronization with this, the light receiving side CPU 22 sequentially outputs the shift signal T0 to the shift register 23. Thus, the shift register 23 switches the four output terminals, sequentially applies the shift output signals T1 to T4 to the AND circuits 21a to 21d, and turns on the switch elements 18a to 18d. The light received from the light receiving elements 12a to 12d is enabled by the ON operation of the switch elements 18a to 18d, and is sequentially input to the A / D converter 19.
[0024]
Here, the light-receiving-side CPU 22 includes a plurality of comparing means for comparing the amount of light detected by the light-receiving control means with different reference levels. It functions as an “output unit” of the present invention including a level determination unit that determines which level the amount will be in a predetermined multi-level level (for example, 16 levels) and outputs an output signal according to the determined level. .
Specifically, the digital light receiving signals D, which are sequentially A / D converted from the analog light receiving signals A1 to A4 by the A / D converter 19, are inputted, and for each of the digital light receiving signals D, FIG. It is determined which of the 16 levels it corresponds to, and converted into a 4-bit digital output signal D 'according to the result of the determination. Then, the light receiving side CPU 22 first outputs a start pulse signal and then sequentially outputs a 4-bit digital output signal D 'corresponding to the light receiving elements 12a to 12d as shown in FIG. E (corresponding to the “common output terminal” of the present invention).
[0025]
(2) Detection Method of Detection Target W and Detection Sensitivity Adjustment Method of Multi-Optical-Axis Photoelectric Sensor In the following description, reference numerals are used for optical axes formed by light receiving elements 12a to 12d that form a pair with each of light projecting elements 11a to 11d. A description will be given with reference to N1 to N4.
[0026]
Here, for example, water is applied to the upper two optical axes N1 and N2 of the four optical axes N1 to N4 of the multi-optical axis photoelectric sensor, and the light receiving elements 12a and 12b of the two optical axes N1 and N2 receive light. The case where the amount is reduced will be described.
First, the user connects the external device 10 such as a personal computer to the external output terminal E of the light receiver 12 via the cable L2.
[0027]
<At the time of detection sensitivity adjustment>
The user activates the external device 10 and the multi-optical axis photoelectric sensor without disposing the detection target W. Then, the digital output signal D ′ output from the external output terminal E of the multi-optical axis photoelectric sensor is taken into the external device 10, and the detection sensitivity adjustment screen 25 is displayed on the display 10a of the external device 10.
[0028]
The detection sensitivity adjustment screen 25 displays the light reception level in each of the light receiving elements 12a to 12d, and displays a changeable reference value serving as a reference for detecting light input / shielding in each of the light receiving elements 12a to 12d. It is set in advance. Specifically, as shown in FIG. 4A, a graph of the received light amount level (divided into 16 stages) for each of the light receiving elements 12a to 12d and a graph of the received light amount are displayed. The preset reference value is, for example, an intermediate value between the light receiving amount level 12 when the optical axes N1 to N4 are not affected by others and the level 0 when the detection target object W exists and is shielded. The received light level 6 which is a level is set as the reference value.
[0029]
Here, the upper two optical axes N1 and N2 of the four optical axes N1 to N4 of this multi-optical axis photoelectric sensor are covered with water, and accordingly, the light receiving amounts of the upper two light receiving elements 12a and 12b. Is decreasing. Therefore, the lower two light receiving elements 12c and 12d have the light receiving amount level 12, whereas the upper two light receiving elements 12a and 12b have the light receiving amount level 8, and the light receiving amount is affected by the influence of the water. The level has decreased. When an object is to be detected with the reference value as it is, the light receiving level 6 of the reference value is not an intermediate value of the light receiving level 8 of the upper two light receiving elements 12a and 12b. The light receiving sensitivity of 12a, 12b becomes worse than the light receiving sensitivity of the other light receiving elements 12c, 12d. In this case, for example, when noise or the like is received, the detection sensitivity of the detection target W varies among the light receiving elements 12a to 12d.
[0030]
In such a case, the detection sensitivity is adjusted by changing a reference value serving as a reference in order to detect light entry / shielding. For example, when the decreased light reception amount is the light reception amount level 8, the light reception amount level 4 in the middle of the light reception amount is set as a new reference value for the two light receiving elements 12a and 12b whose light reception amount levels have decreased. . Then, the detection sensitivity does not vary for each of the light receiving elements 12a to 12d, and the detection of the presence / absence of the detection target W can be performed with no variation even for each of the light receiving elements 12a to 12d even when noise is received. Will be able to
[0031]
<During object detection>
Next, as shown by the dotted line in FIG. 1, the user arranges the detection target W so as to cross the optical axis of the multi-optical axis photoelectric sensor (here, the detection object W is arranged to cross the optical axes N2 and N3). ), The multi-optical axis photoelectric sensor and the external device 10 are activated. Then, the digital output signal D ′ output from the external output terminal E of the multi-optical axis photoelectric sensor is taken into the external device 10, and the object detection screen 26 is displayed on the display 10a of the external device 10.
[0032]
On the object detection screen 26, as shown in FIG. 4 (b), the light reception level of each of the light receiving elements 12a to 12d and its graph are displayed, and the reference value set on the detection sensitivity adjustment screen 25 is displayed. . In addition, the detection result of light input / shielding is displayed for each of the light receiving elements 12a to 12d.
[0033]
Specifically, for this detection, for each of the light receiving elements 12a to 12d, the light reception level of the reference value already set and the light reception level of the light received in the state where the detection target W is arranged are compared. If the level of the amount of light received while the detection target W is disposed is larger than the set reference value, it is determined that the detection target W does not exist on the optical axes N1 to N4. ("None" is displayed on the object detection screen 26). On the other hand, if the level of the amount of light received while the detection target W is disposed is smaller than the set reference value, it is detected that the optical axes N1 to N4 are in the light-shielded state ( "Yes" is displayed on the object detection screen 26).
[0034]
As described above, since the digital output signal D ′ corresponding to the amount of light received by each of the light receiving elements 12a to 12d is output to the external device 10, the user can use the external device 10 for each of the optical axes N1 to N4. It is possible to perform light-in / light-out detection while adjusting the reference value for light-in / light-out detection by operating the external device 10.
Further, since the signal output from the external output terminal E to the external device 10 is a digital output signal D ′, the noise resistance is higher than in the case where the signal is output as an analog signal, and the light received by each of the light receiving elements 12 a to 12 d is received. An accurate output signal corresponding to the amount can be provided to the external device 10. Further, by sequentially outputting a plurality of output signals to the external device 10 through one common cable L2 (signal line) via the common external output terminal E, the number of wirings can be reduced by that much, and cost reduction and wiring can be suppressed. Work can be simplified.
[0035]
<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention, and furthermore, besides the following, within the scope not departing from the gist. Can be implemented with various modifications.
(1) In the present embodiment, the analog light receiving signals A1 to A4 are output from the light receiving circuits 17a to 17d. However, digital signals may be output from the light receiving circuits 17a to 17d including A / D converters. . At this time, the A / D converter 19 becomes unnecessary.
(2) In this embodiment, the digital light receiving signal D output from the A / D converter 19 is input to the light receiving CPU 22. However, the digital light receiving signal D is output from the A / D converter 19 without passing through the light receiving CPU 22. The digital light receiving signal D may be output to the external device 10 as it is.
[0036]
(3) In this embodiment, the analog light receiving signals A1 to A4 output from the light receiving circuits 17a to 17d are converted into digital signals and then output to the external device 10, but the analog light receiving signals A1 to A4 are directly output to the external device 10. May be output directly. However, as in the present embodiment, the output after conversion into a digital signal has a stronger effect on noise than outputting the analog light reception signals A1 to A4 as they are.
(4) In the present embodiment, a CPU is provided for each of the light projector 11 and the light receiver 12, but a CPU may be provided for only one of the light projector 11 and the light receiver 12. In this case, it is desirable that the A / D converter 19 be provided in the light projector 11 or the light receiver 12 on the side where the CPU is provided.
[0037]
(5) A comparator for comparing the amount of light received by each of the light receiving elements 12a to 12d with a predetermined reference value may be separately provided, and a configuration for comparing the amount of light received by each of the light receiving elements 12a to 12d with a predetermined reference value may be added.
(6) In the present embodiment, the output signals corresponding to the respective light receiving elements 12a to 12d are sequentially output by the cable L2. However, a plurality of signal lines are provided, and the output signals corresponding to the respective light receiving elements 12a to 12d are provided. May be output separately.
[0038]
(7) In the present embodiment, the personal computer is exemplified as the external device 10, but the present invention is not limited to this, and a general-purpose device other than the personal computer may be used. Further, the device is not limited to a general-purpose device, and may be a dedicated device such as a dedicated control box for operating the multi-optical axis photoelectric sensor. That is, a display unit that displays the amount of light received by each of the light receiving elements 12a to 12d based on each output signal from the output unit, and a comparison that compares the amount of light received by each of the light receiving elements 12a to 12d with a reference value based on the output signal. And a reference value changing means capable of changing and setting the reference value of the comparing means for each of the light receiving elements 12a to 12d.
(8) In this embodiment, the four light projecting elements 11a to 11d and the four light receiving elements 12a to 12d are arranged to face each other. It is good also as a structure to arrange.
[Brief description of the drawings]
FIG. 1 is an overall view showing a multi-optical axis photoelectric sensor of this embodiment and an external device. FIG. 2 is a diagram showing an electrical configuration of the multi-optical axis photoelectric sensor of this embodiment. FIG. 3 (a) Digital output signal FIG. 4B is a diagram showing a waveform of a digital output signal. FIG. 4A is a diagram of a detection sensitivity adjustment screen. FIG. 4B is a diagram of an object detection screen.
DESCRIPTION OF SYMBOLS 10 ... External apparatus 11 ... Light projector 11a-11d ... Light emitting element 12 ... Light receiver 12a-12d ... Light receiving element 15 ... Light emitting side CPU
19 A / D converter 22 CPU on the light receiving side
25 detection sensitivity adjustment screen 26 object detection screens A1 to A4 analog light reception signal D digital light reception signal D 'digital output signal E external output terminals L1 and L2 cable W detection target

Claims (4)

Having a light emitter and a light receiver that are arranged to face each other,
The light projector is provided with a plurality of light emitting elements, and light emitting control means for sequentially performing the light emitting operation to the plurality of light emitting elements,
The light receiver, a plurality of light receiving elements paired with each of the plurality of light emitting elements,
A multi-optical axis photoelectric sensor, comprising: a light receiving control unit that performs a light receiving operation for sequentially detecting a light receiving amount in each of the light receiving elements in a predetermined order in synchronization with each of the light projecting operations.
A multi-optical axis photoelectric sensor, comprising: output means capable of outputting an output signal corresponding to an amount of light received by each of the light receiving elements detected in each of the light receiving operations to an external device. 2. The multi-optical axis photoelectric sensor according to claim 1, wherein said output means outputs said output signal as a digital signal. 3. The multi-optical axis photoelectric sensor according to claim 1, wherein the output unit sequentially outputs output signals corresponding to the respective light receiving elements via a common output terminal. The output unit is set to different reference levels from each other, a plurality of comparison units that compares the amount of light received by the light reception control unit with each reference level,
Level determining means for determining which one of predetermined multi-levels the amount of light received by each light receiving element is based on a comparison result of the plurality of comparing means, and outputting an output signal corresponding thereto. The multi-optical axis photoelectric sensor according to any one of claims 1 to 3, further comprising:

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