JPH048352Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an optical foreign object detection device suitable for use in detecting foreign objects on and around work tables in industrial machines such as NC equipment. .

[Conventional technology]

Conventionally, in some automation equipment such as NC equipment, in order to detect foreign objects on the work table, a plurality of light emitting elements and light receiving elements are placed facing each other with the work table in between to form a foreign object detection device. are doing.

[Problem that the invention attempts to solve]

However, according to such a foreign object detection device, the foreign object detection performance is determined by the spacing between a pair of adjacent light emitting elements and light receiving elements, and in order to improve this foreign object detection performance, it is necessary to arrange a large number of light emitting and light receiving elements at small intervals. This resulted in an extremely expensive detection device.

[Means for solving problems]

The present invention was developed in view of these problems, and it changes the reflection direction of the light that passes through the half mirror while rotating the rotating mirror, and also provides a foreign object detection plate adjacent to the surface of the foreign object detection plate. Reflection surfaces are arranged intermittently to guide the reflected light from the rotating mirror that is irradiated across the plate surface to the mirror surface of the half mirror via the rotating mirror, and the reflected light from the rotating mirror is directed to the mirror surface of the half mirror. The number of times of indirect irradiation through the reflective surface is counted, and foreign matter on the plate surface is detected based on this count value.

[Effect]

Therefore, according to this invention, it is possible to detect foreign matter based on the number of times that the mirror surface of the half mirror is indirectly irradiated with the reflected light from the rotating mirror.

〔Example〕

Hereinafter, the optical foreign object detection device according to the present invention will be explained in detail. FIG. 1 is a block diagram showing one embodiment of this optical foreign object detection device. In the same figure, 1
is a work table for industrial machinery such as NC equipment,
2 is a light projection source; 3 is a convex lens that focuses the light emitted from the light projection source 2; 4 is a half mirror that transmits the light focused by lens 3 (hereinafter referred to as a spot beam); 6 is a pulse motor that rotates the rotating mirror 5 and rotates the direction of reflection of the spot beam reflected by this mirror in a counterclockwise direction; This is a reflective plate placed so as to surround the piece. The reflecting plate 7 is composed of partial mirrors 7 _-1 , 7 _-2 , ...7 _-o arranged intermittently at predetermined intervals,
These partial mirrors 7 _-1 to 7 _-o are constructed by collecting prisms or glass beads, and are configured so that the spot beam reflected while rotating by the rotating mirror 5 is irradiated onto the reflecting plate 7 at an angle of θ. It's getting old. Then, the spot beam that is rotated and irradiated onto the reflecting plate 7 is transmitted to the partial mirrors 7 _-1 to _{7 -o.}
The light is reflected by the mirror surface of the rotating mirror 5, is guided to the mirror surface of the half mirror 4, is reflected, and is received by the light receiving element 9 via the convex lens 8. The light received by the light-receiving element 9 is converted into a voltage value corresponding to the intensity of the light in this element, and is input to the foreign object detection circuit 10 at the subsequent stage.

The foreign object detection circuit 10 is composed of comparators 11 and 12, a counter 13, a first latch circuit 14, a reference count number setter 15, a comparator 16, a second latch circuit 17, and delay circuits 18 and 19. The electrical signal sent out via the light receiving element 9 is input to the non-inverting input terminals of the comparators 11 and 12. Comparison reference voltages V ₁ and V ₂ (V ₁ > V ₂ ) are set at the inverting input terminals of comparators 11 and 12, and the output of comparator 1 input rises from the “H” level to the “L” level. The count value in the counter 13 increases by 1 at the time when the value decreases. Then, the count value in this counter 13 is latched in a latch circuit 14 when the output of the comparator 11 becomes "H" level, and the count value Na latched in this latch circuit 14 and the reference count number setter A comparator 16 compares the count value N set to 15. Therefore, since the comparison result in the comparator 16 indicates that the output of the comparator 11 becomes "H" level, the delay circuit 19
After a predetermined time has elapsed, the latch circuit 17 latches, and when the latched comparison result is Na<N, the latch circuit 17 continues to send out a foreign object detection signal from its output to notify the presence of a foreign object. There is. The count value in the counter 13 is reset after a predetermined time has elapsed in the delay circuit 18 after the output of the comparator 11 becomes "H" level, and the delay time in the delay circuit 19 is This is set to be slightly longer than the comparison operation time in the device 16.

Next, the operation of the optical foreign object detection device configured as described above will be explained. That is, the light emitted from the light projecting source 2 is focused by the lens 3 to become a spot beam, passes through the half mirror 4, and is irradiated onto the rotating mirror 5. Assuming that the rotating mirror 5 is rotationally driven by the pulse motor 6, the spot beam reflected by the rotating mirror 5 rotates counterclockwise while changing its reflection direction every moment. FIG. 2 is a waveform diagram showing the intensity of light received by the light receiving element 9 as the rotating mirror 5 rotates. That is, at the point when the reflective surface of the rotating mirror 5 becomes approximately perpendicular to the incident spot beam as shown in FIG. (point a in FIG. 2), and then as the rotating mirror 5 rotates, the light irradiated onto the light receiving element 9 is temporarily interrupted (point b in FIG. 2). And rotating mirror 5
When rotated to the position shown in FIG. 3b, the spot beam reflected by the rotating mirror 5 hits the reflecting surface 7.
The light begins to be irradiated onto the partial mirror 7 _-1 , and this light is reflected and is received by the light receiving element 9 via the mirror surfaces of the rotating mirror 5 and the half mirror 4 (point c in FIG. 2). At this time, the intensity of the light received by the light receiving element 9 is such that the spot beam reflected by the rotating mirror 5 is indirectly reflected via the partial mirror _7-1 , so the intensity of the light is not directly reflected by the rotating mirror 5. This light is weaker than the received light (Fig. 3a), and disappears once the rotating mirror 5 rotates further and its spot beam moves to the end of the partial mirror _7-1 as shown in Fig. 3c. (point d in Figure 2).
Then, as the rotating mirror 5 continues to rotate,
This time, the spot beam begins to be irradiated onto the adjacent partial mirror _7-2 as shown in FIG. (point e in Figure 2). Similarly below,
As the spot beam reflected by the rotating mirror 5 rotates, this light is intermittently reflected by each partial mirror, and is received by the light receiving element 9 via the mirror surfaces of the rotating mirror 5 and the half mirror 4. . When the spot beam reflected by the rotating mirror 5 reaches the end surface of the partial mirror 7 _-o (Fig. 3e), the last weak light received by the light receiving element 9 disappears (Fig. 2). As the rotating mirror 5 continues to rotate, strong light will again enter the light receiving element 9 at the next origin position (point g in Figure 2).
point).

In other words, as the rotating mirror 5 rotates, the light receiving element 9
A voltage signal having substantially the same waveform as that in FIG. 2 is input to comparators 11 and 12 of the foreign object detection circuit 10 through the voltage signal. Comparators 11 and 12 both send out "H" level signals when a high level voltage signal (hereinafter referred to as the origin signal) is input at the origin position, and when a low level voltage signal is input. "L" and "H"
Sends a level signal. That is, the voltage _V1 set at the inverting input terminal of the comparator 11 is set lower than the voltage value inputted at point a in FIG. 2 and higher than the voltage value inputted at point c, and The voltage V ₂ set at the inverting input terminal of No. 12 is set lower than the voltage value input at point c in FIG.

Now, suppose that strong light is received by the light receiving element 9 at point a in FIG. At this time, comparator 11
The outputs of and 12 go to the "H" level, and after a predetermined time has elapsed in the delay circuit 18, the count value in the counter 13 is reset.
That is, the delay time τ of the delay circuit 18 is set shorter than the time from when strong light is received at point a to when weak light is received at point c in FIG. The number of falls of the "H" level signal sent from 12 is counted. When the output of the comparator 11 becomes "H" level again at point g in FIG. A comparator 16 compares the count value N set to . The count value Na latched in the latch circuit 14 at this time is the number of intermittent periods of weak light incident on the light receiving element 9 from point a to point g in FIG. 2 (during one cycle of the origin position). If some foreign matter acts on the spot beam reflected by the rotating mirror 5, the number of interruptions will be smaller than the number of partial mirrors 7 _-1 to 7 _-o . That is, when a foreign object acts on the spot beam reflected by the rotating mirror 5, the partial mirrors 7 _-1 to 7
_-o is no longer irradiated with the spot beam, and the number of interruptions in the weak light guided to the light receiving element 9 via the mirror surfaces of the rotating mirror 5 and the half mirror 4 is reduced. In other words, when no foreign matter acts on the spot beam reflected by the rotating mirror 5, the number of intermittent periods of weak light guided to the light receiving element 9 is equal to the number of partial mirrors _7-1 to _7-o , and the reference count number The count value N set in the setting device 15 is set equal to the number of partial mirrors 7 _-1 to 7 _-o . Therefore, if any foreign matter acts on the spot beam reflected by the rotating mirror 5,
The comparison result in the comparator 16 is Na<N,
A foreign object detection signal is now sent from the latch circuit 17, and from this foreign object detection signal, the work table 1
It becomes possible to recognize the presence of foreign matter on the surface.

In this embodiment, not only the top of the work table 1 but also the surrounding area thereof within the range angle θ is the foreign object detection plate surface, and the foreign object detection plate surface is Needless to say, their existence will be recognized. Further, in this embodiment, the configuration is such that only the presence of foreign matter is known, but it is also possible to configure the configuration so that information on which position of the partial mirror is blocked is known from the count value. By doing so, it becomes possible to recognize not only the presence of a foreign object but also the area where the foreign object exists. Also, the count value set in the reference count number setting device 15 is the partial mirror 7 _-1
Since the number of partial mirrors 7 -1 to 7 _-o is known in advance, it can be set using a digital switch, but it is also possible to search for the number of partial mirrors 7 _-1 to 7 _-o using the spot beam of the rotating mirror 5 and set it automatically. It may also be a configuration. moreover,
In this embodiment, the point in time when the mirror surface of the half mirror 4 is directly irradiated with the reflected light from the rotating mirror 5 is defined as the origin position, and during one cycle of this origin position, the reflected light from the rotating mirror 5 is reflected on the mirror surface of the half mirror 4. Face 7
Although the number of times of indirect irradiation via the irradiation is counted, it is not necessarily necessary to count based on the origin position, and the count value may be reset every time the rotating mirror 5 rotates. good.

[Effect of idea]

As explained above, according to the optical foreign object detection device according to the present invention, the reflection direction of the light transmitted through the half mirror is varied while rotating the rotary mirror, and the Reflecting surfaces are arranged intermittently to guide the reflected light from the rotating mirror that is irradiated across the plate surface to the mirror surface of the half mirror via the rotating mirror, so that the reflected light from the rotating mirror is directed to the mirror surface of the half mirror. The number of times of indirect irradiation through the reflective surface is counted, and the foreign matter on the plate surface is detected based on this count value, so that the foreign matter can be detected depending on the size of the count value. This makes it possible to detect foreign objects on the surface of the foreign object detection plate in a simple manner and with high accuracy without arranging a large number of light emitting/receiving elements at close intervals as in the conventional method.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an embodiment of the optical foreign object detection device according to the present invention, Fig. 2 is a waveform diagram showing the intensity of light received by the light receiving element of this foreign object detection device, and Fig. 3 1 is a plan view showing the relationship between the rotational position of a rotating mirror and the direction of reflection of a spot beam reflected on this rotating mirror; FIG. DESCRIPTION OF SYMBOLS 1...Work table, 2...Light source, 4...Half mirror, 5...Rotating mirror, 6...Pulse motor, 7...Reflector, 7 _-1 to 7 _-o ...Partial mirror, 9... ...Light receiving element, 10... Foreign object detection circuit.

Claims (1)

[Claims for Utility Model Registration] A rotating mirror that changes the reflection direction of light transmitted through the half mirror while rotating; a reflecting surface that reflects the reflected light of the rotating mirror that is irradiated across the surface and guides the reflected light of the rotating mirror to the mirror surface of the half mirror via the rotating mirror; What is claimed is: 1. An optical foreign object detection device comprising foreign object detection means for counting the number of times of indirect irradiation through a surface and detecting foreign objects on the plate surface based on the counted value.