JP3401816B2 - Photoelectric switch - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric switch having an optical axis adjusting function.

[0002]

2. Description of the Related Art In a conventional photoelectric switch, it is necessary to adjust an optical axis in order to accurately detect an object in an object detection area. For example, in the reflective photoelectric switch, the detection object 101 is arranged at a predetermined position as shown in FIG. 5, and the case of the photoelectric switch 102 is rotated along an axis perpendicular to the optical axis as shown in the figure. Then, the object is detected, and the stable operation indicator lamp 103 is rotated so as to have a central angle within a range in which it is lit. Then, while the indicator lamp for stable operation display is lit, the sensitivity adjusting resistor 104 lowers the light receiving sensitivity of the photoelectric switch to sequentially narrow the stable light incident area. Then, the angle is turned by a very small angle to select an angle at which light can be stably received even at a low level, and the optimum point is selected.

[0003]

As described above, in the conventional photoelectric switch, the optical axis adjustment work requires a long time and is a troublesome work. Particularly in a transmissive photoelectric switch, it is necessary to arrange the light receiving section corresponding to the light projecting section, so it is necessary to adjust the optical axes of the light projecting section and the light receiving section to each other, and it takes a long time to adjust the optical axis. There was a drawback.

The present invention has been made in view of such conventional problems, and it is a technical object to shorten the adjustment time and easily adjust the optical axis.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a light projecting unit for irradiating an object detection region with light, a light receiving unit for receiving light from the object detection region, and the presence or absence of an object are determined based on the output of the light receiving unit. And a signal processing means for controlling the output of the light receiving portion at a set threshold level, and comparing the output of the light receiving portion with a peak value of the light receiving signal while the signal exceeding the threshold is obtained from the comparing means. Peak value holding means to hold,
Threshold updating means for calculating a new threshold value between the set threshold value and the peak value held by the peak value holding means and setting it in the comparing means when a signal exceeding the threshold value is no longer obtained from the comparing means And a display unit for displaying a state in which a signal exceeding the threshold value is obtained from the comparison unit.

[0006]

According to the present invention having such a feature, the lowest threshold value is set in the comparing means before the optical axis adjustment, and the photoelectric switch is rotated within the optical axis adjustment range. Then, a signal exceeding the threshold value can be obtained from the comparing means, but the peak value during this period is held. Then, if the received light signal becomes equal to or less than the threshold value, a new threshold value is calculated between the threshold value set by the threshold value updating means and the peak value and set in the comparison means. Further, the display is externally displayed only while the signal exceeding the threshold is obtained from the comparison means. In this way, even if the photoelectric switch is rotated, the lighting range is gradually narrowed, and the optimum optical axis can be automatically set by rotating the photoelectric switch several times.

[0007]

1 is a block diagram showing the overall structure of a photoelectric switch according to an embodiment of the present invention. In the figure, an oscillator circuit 1 is a circuit for periodically generating a light emitting pulse,
The output is given to the drive circuit 2 to drive the light projecting element 3 at a constant cycle. The light projecting element 3 irradiates the object detection area with light, and the light from the object detection area is received by the light receiving element 4. The light receiving element 4, the amplifier 5 for amplifying its output, and the gate circuit 6 for giving the light receiving signal to the amplifier circuit of the next stage only while generating the light emitting pulse are the same as those of a normal photoelectric switch. And this amplified output is the comparator 8
The object detection signal and the signal for stable operation display are output through the signal processing unit 9. The object detection signal is input to the output circuit 10 and output to the outside. The display 11 is a display for displaying object detection, and the display 12 is a display for stable operation display.

In the present embodiment, the output of the amplifier 7 is given to the sample hold circuit 21 and the comparator 22. The sample and hold circuit 21 samples and holds the signal only while the output of the comparator 22 is at the H level, and its output is the A / D converter 24 in the microcomputer 23.
Given to. The microcomputer 23 has a CPU, a memory, an A / D converter, an input / output interface, etc., which are integrally formed, and is provided with a peak value holding means 25, a threshold value updating means 26, and a display means 27 as described later. . The threshold value output from the threshold value updating means 26 in the microcomputer 23 is set in the comparator 22. The comparator 22 is a comparison means that compares the threshold value with the signal from the amplifier 7 and outputs an H level signal when the amplified output exceeds the threshold value. The output of the comparator 22 is displayed on the display unit 28 via the display unit 27 in the microcomputer 23.
The output status is displayed more.

Next, the operation of this embodiment will be described. First, at the time of adjusting the optical axis, the sample hold circuit 21 is operated to put the microcomputer 23 in the adjustment mode. This optical axis setting method will be described with reference to FIGS. FIG. 2 is a flowchart showing the operation of this embodiment. First, when the adjustment mode is started, the case 42 of the photoelectric switch is arranged so as to face the detection object 41 as shown in FIG. 3, and its angle is rotated in the ± θ direction as shown in order to adjust the optical axis. Then the microcomputer 23
Sets the threshold value Th1 in step 31. Then, the routine proceeds to step 32, where it waits for the output of the comparator 22 to become H level. The comparator 22 compares the threshold value Th1 thus set with the output of the amplifier 7. As shown in Figs. 3 and 4, the case of the photoelectric switch is + from the -θ side
When rotated to the θ side, the comparison output becomes H level in the range exceeding the threshold Th1 as shown in FIGS. 4 (a) and 4 (b).
If the threshold value Th1 is exceeded, the peak value of the output of the A / D converter 24 is held in step 33. At this time, since the output is obtained from the comparator 22, the display 28 is turned on in step 34. Then, the routine proceeds to step 35, where it is checked by the comparator 22 whether or not the H level continues, and if it continues, steps 33 to 35 are repeated. In this way, the peak value is held in the memory in the microcomputer 23.

When the output of the comparator 22 becomes L level, the routine proceeds to step 36, where a new threshold Th2 is calculated by the following equation. Th2 = Th1 + (Vpeak−Th1) · α (1) Here, α is an arbitrary constant that satisfies 0 <α <1. In this way, the threshold value is updated to Th2, and Th2 is set in the comparator 22 as a new threshold value. The output from the comparator 22 is L
Since the level is reached, the lighting of the display 28 is stopped in step 37. At this time, the sample hold circuit 21
Is reset, but the peak value held at the same time may be reset.

Next, the case 42 of the photoelectric switch is rotated from the + θ direction to the −θ direction. By doing so, an H level signal can be obtained from the comparator 22 in a narrower range as shown in FIG. Therefore, similarly, the peak value is held during the rotation, and when the comparison output becomes L, the threshold value is updated to a higher threshold value Th3. The new threshold value is generally expressed by the following equation. Thi + 1 = Thi + (Vpeak−Thi) · α (i is an integer of 1 to n) Thus, as shown in FIGS. 4B to 4F, the photoelectric switch is rotated to sequentially increase the threshold value. In this way, the range in which the comparator 22 becomes the H level becomes sufficiently narrow, and θ approaches 0, that is, approaches the optimum optical axis. In this way, when the setting is completed a predetermined number of times, for example, about 5 times, that position becomes the optimum optical axis. Therefore, in the present invention, the optimum optical axis can be easily set only by rotating the case 42 of the photoelectric switch.

Here, the microcomputer 23 achieves the function of the peak value holding means 25 for holding the peak value of the received light signal while the signals exceeding the threshold value are obtained from the comparator 22 in steps 32, 33 and 35. Further, the microcomputer 23 achieves the function of the threshold value updating means 26 which updates the threshold value when the signal exceeding the threshold value is not obtained from the comparing means in step 36, and according to the output of the comparator in steps 34 and 37. The function of the display means 27 that drives the display 28 is achieved.

In this embodiment, the comparator 22 is provided independently of the microcomputer, but all the outputs of the amplifier 7 are sampled and held and taken into the microcomputer, and the function of the comparator is carried out in the microcomputer. It goes without saying that you may do so.

In this embodiment, the comparator 8 for detecting an object, the signal processor 9 and the microcomputer 23 for adjusting the optical axis are independent, but all the outputs of the amplifier 7 are passed through the sample hold circuit 21. Needless to say, the functions of the comparator and the signal processing unit can be simultaneously achieved in the microcomputer by converting the output into a digital signal by the A / D converter 24 and discriminating its output with a predetermined threshold value. Further, the display 28 used for adjusting the optical axis may be used as the display 11 or 12 for operation display or stable operation display. In this case, when a signal exceeding the threshold value is obtained at the time of adjusting the optical axis, it is easy to distinguish the operation display or the stable operation display by blinking the display 11 or 12.

[0015]

As described in detail above, according to the present invention, a threshold value different from the normal object detection signal is set, and the photoelectric switch is rotated to sequentially increase the threshold value. Therefore, the optimum optical axis can be adjusted only by rotating the photoelectric switch several times while confirming the lighting of the display means. Therefore, the optical axis adjustment becomes extremely easy, and the effect that the adjustment work can be shortened is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a photoelectric switch according to an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of this embodiment.

FIG. 3 is a schematic view showing a rotating state of an object of the photoelectric switch according to the present embodiment.

FIG. 4 is a graph showing a rotation state of the photoelectric switch according to the present embodiment, a light receiving output, and an output change.

FIG. 5 is a perspective view showing the operation of the conventional photoelectric switch when adjusting the optical axis.

[Explanation of symbols]

1 oscillator circuit 3 Projection element 4 Light receiving element 8 comparator 9 Signal processing unit 21 Sample and hold circuit 22 Comparator 23 Microcomputer 24 A / D converter 25 Peak value holding means 26 Threshold updating means 27 Display means 28 Display

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H03K 17/78

Claims (3)

(57) [Claims] 1. A light projecting unit for irradiating an object detection region with light, a light receiving unit for receiving light from the object detection region, and signal processing means for determining the presence or absence of an object based on the output of the light receiving unit. In a photoelectric switch including: a comparing unit that compares the output of the light receiving unit at a set threshold level; and a peak value holding unit that holds the peak value of the light receiving signal while a signal exceeding the threshold is obtained from the comparing unit. When the signal exceeding the threshold value is no longer obtained from the comparison means, a new threshold value between the set threshold value and the peak value held by the peak value holding means is calculated and the comparison means is operated. A photoelectric switch, comprising: a threshold updating means to be set; and a display means for displaying a state in which a signal exceeding the threshold is obtained from the comparing means. 2. The photoelectric switch comprises a sample hold circuit for sequentially sampling and holding the received light signal while the signal is obtained from the comparison means, and the peak value holding means holds the output of the sample hold circuit. 2. A memory for holding a peak value is included.
Photoelectric switch described. 3. A display device for displaying an object detection signal,
2. The photoelectric switch according to claim 1, wherein the display unit is configured to blink the display in the optical axis adjustment mode.