JPH02284086A - Photoelectric type object detector - Google Patents

Abstract

PURPOSE:To detect only the object intruding into a set monitoring distance range by providing a finite light receiving body element which is disposed along a light receiving region and receives only the condensed light reflected from the object intruding into the prescribed monitoring distance. CONSTITUTION:A condenser lens 5 is disposed in parallel on the same plane as the plane of a lens 3 disposed in front of a light emitting element 2. The lens 5 condenses the reflected light reflected from the object 4 and images the same onto the specific positions S1 (S2) on the prescribed condensing region. The finite light receiving body element 6 is disposed along the condensing re gion. The element 6 is so disposed that the effective outside end (inside end) thereof coincides with the condensing position S1 (S2) and, therefore, the light reflected from the object 4 existing in the shortest (longest) monitoring distance position L 1 (L 2) is detected by the element 6. Namely, all the reflected light rays from the object 4 existing between the monitoring distance L 1 to L 2 are effectively received by the element 6, by which the intrusion of the object 4 is identified, but the object 4 existing beyond this range is not identified. The generation of the erroneous detection occurring in the reflection by a re mote different object is, therefore, obviated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a photoelectric reflective object detection device that has a light emitting element and a light receiving element and electrically detects light reflected from an object to detect the presence or absence of an object. The present invention relates to a device, and more particularly to a device for detecting an object entering within a predetermined monitoring distance range in the optical axis direction.

[Conventional technology]

Conventionally, a light emitting element and a light receiving element are arranged in parallel on the same surface,
2. Description of the Related Art Photoelectric reflective object detection devices have been known that perform object detection by receiving light reflected from an object that traverses an optical axis extending in a direction perpendicular to several planes.

[Problem that the invention seeks to solve]

However, in conventional photoelectric reflective object detection devices, there is no limit in principle to the distance at which objects can be detected in the optical axis direction, and unrelated objects far away can be detected as long as they are not blocked by a background surface. There was a problem.

In practice, there are many requests to detect only objects that enter within a predetermined distance range, and in response to this, conventional general-purpose reflective object detection devices cannot be used as they are, and some type of incident light reach distance limiting means is additionally required. there was.

[Means for solving problems]

The present invention aims to solve the above-mentioned problems of the prior art. For this reason, the photoelectric reflective object detection device according to the present invention has a light emitting part that generates light, and an optical axis that passes through a monitoring area having a predetermined monitoring distance range and extends in the distance direction. It has an input optical system that inputs light emitted along the optical axis, and a reflection optical system that collects the reflected light from an object that has entered the optical axis and focuses it on a specific position in the light receiving area according to the distance of the object in the optical axis direction. ing. In addition to these, there is a finite photoreceptor element that is placed along the light receiving area and receives only reflected light from an object that has entered within the monitoring distance, and a finite photoreceptor element that sends an object detection signal when the finite photoreceptor element receives reflected light. It has an output circuit section that generates.

Preferably, the finite photoreceptor element has one end coincident with a light collection position corresponding to the shortest monitoring distance and the other end coinciding with a light collection position corresponding to the shortest monitoring distance.

More preferably, the light emitting section includes a light emitting element that emits light intermittently according to the sampling signal, and the output circuit section sequentially creates sampling data according to the intensity of the received reflected light and changes the sampling data back and forth in time. An object detection signal is output by detecting a relative change in sampling data. [Function] According to the present invention, among objects that have entered so as to block the incident optical axis, objects within a predetermined monitoring distance range are detected. Only the condensed light reflected from the object present in the finite photoreceptor element is received by the finite photoreceptor element, and the entry of the object is identified. Even if the light reflected from an object outside the monitoring distance range is focused by the reflective optical system, the focused position is outside the effective light receiving surface of the finite photoreceptor element, so the focused light is not detected.
Objects existing beyond the monitoring distance range are therefore not identified.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1A is a conceptual diagram showing the overall configuration of the photoelectric object detection device according to the present invention, and particularly shows a state in which an object located at the shortest monitoring distance is being detected. The case 1 contains a light emitting section, an incident optical system, a reflective optical system, a photoreceptor element, and an output circuit section, and can be placed at a desired location and in a desired direction.

The light emitting section has a light emitting element 2 made of a light emitting diode or the like for emitting light. The input optical system is composed of a lens 3 placed in front of the light emitting element 2, the optical axis of which is parallel to the set monitoring distance direction, and the lens 3 converts the emitted light into parallel light beams into a beam spot. incident in the direction of the optical axis.

In the state shown in FIG. 1A, the optical axis is blocked by the subject or object 4 present at the shortest monitoring distance position L1, and the incident light beam spot is reflected by the object 4.

The reflective optical system is composed of a condenser lens 5 arranged parallel to the lens 3 on the same plane.

The condensing lens 5 condenses the light reflected from the object 4 and forms an image at a specific position S1 on a predetermined condensing area.

A finite number of photoreceptor elements 6 are arranged along the light collection area. Since the effective outer end of the photoreceptor element 6 is arranged to coincide with the light condensing position S1, the light reflected from the object 4 located at the shortest monitoring distance 1 is detected by the photoreceptor element 6. Since the condensing position of the light reflected from an object closer to the lens 3 side is shifted to the outside of Sl, the light receiving element 6
does not detect light reception.

FIG. 1B shows a state when the object 4 is located at the longest monitoring distance position L2 when the same object detection device as in FIG. 1A is used. As shown in the figure, the light reflected from the object 4 is condensed by a condensing lens 5 and formed into an image at a specific position S2 on a predetermined condensing area. This position S2 is naturally located inside the position S1 due to the arrangement of the optical system. Since the effective inner end of the finite photoreceptor element 6 is arranged to coincide with the light collection position S2, the light reflected from the object 4 located at the longest monitoring distance 2 is detected by the photoreceptor element 6. Figure 1A
As is clear from and B, all reflected light from objects existing between the shortest monitoring distance L1 and the longest monitoring distance L2 is focused between the two extreme focusing positions fa2s1 and 82, so it is more effective for the photoreceptor element 6. The light is received by the

On the other hand, FIG. 1C shows a state in which the object 4 exists beyond the maximum monitoring pressure ML2 when the same detection device is used. The light reflected from the object 4 passes through the condensing lens 5
Although the light is focused by and imaged on the light focusing area, since the imaging position moves further inward than S2, it deviates from the effective light receiving surface of the photoreceptor element 6 and is not detected.

FIG. 2 is a sectional view showing another embodiment of the combination of the reflective optical system and the photoreceptor element used in the photoelectric object detection device according to the present invention. The reflective optical system is composed of a condenser lens 5 that condenses light reflected from an object and forms an image on a predetermined condensing area. The photoreceptor strand 6 has an inner end that coincides with the light focusing position f&s2 corresponding to the longest monitoring distance L2, but its outer end SO is inside the light collecting position S1 corresponding to the shortest monitoring distance MLL. A reflecting mirror 7 is disposed perpendicularly from the outer end SO of the photoreceptor element 6, and as shown in the figure, light reflected from an object located inside the longest monitoring distance ML2 is reflected directly or by the reflecting mirror 7. The light is then focused on the effective light-receiving surface existing between both ends of the photoreceptor element 6.

Therefore, this embodiment can reduce the area of the expensive photoreceptor element by half compared to the embodiments shown in FIGS. . In practice, there are many usage methods in which only the longest monitoring distance is managed, and this embodiment is also effective in this case.

FIG. 3 is a block diagram showing the overall circuit configuration of the photoelectric object detection device according to the present invention. First, the light emitting section oscillates intermittently in response to the sampling signal CTL input manually at predetermined intervals, and activates the oscillation section 8 which outputs a high frequency superimposed sampling signal O8C having a desired set frequency component. Further, the drive section 9 supplies an intermittent frequency-modulated drive current to the light emitting element 2, which is frequency-modulated in accordance with the signal O8C.

The light emitting element 2 is driven by the modulated drive current and emits frequency modulated light intermittently in synchronization with the sampling signal.

The output circuit section includes a photoreceptor element 6 that receives the light focused by the reflective optical system and outputs a detection current having an amplitude corresponding to a change in the light intensity. An amplifier unit 10 is connected to the photoreceptor element 6, which detects and amplifies the detected current and intermittently outputs an alternating current detection signal AC. The amplifying section 10 includes, for example, a narrow band filter circuit that filters a set frequency component and an AC amplifying circuit. For example, a smoothing section 11 consisting of an integrating circuit or the like is connected to the amplifying section 10, rectifies and smoothes the alternating current detection signal AC, and intermittently outputs a direct current detection signal DC having a corresponding peak value. A conversion unit 12 made of an A/D converter is connected to the smoothing unit 11, and sequentially converts the wave height component of the DC detection signal DC into corresponding sampling data DATA in synchronization with the sampling signal CTL. Therefore, each sampling data DATA is a sampling signal CTL that sequentially represents changes in the intensity of the received focused light.
The data will be shown in synchronization with

In addition, the output circuit section includes a memory section 13 and a control calculation section 14. The memory section 13 has at least two memory areas M1 and M2, alternately records the sampling data supplied by the conversion section 12, and updates the recorded data every time new sampling data is input. The control calculation unit 14 is composed of, for example, a CPU, and receives the above-mentioned sampling signal CT.
In addition to outputting L, the memory section 13 is sequentially accessed by the address signal ADS, and the updated sampling data written in the pair of memory areas M1 and M2 is read out.
Calculate these relative ratios. Based on the calculation result, an output signal OUT indicating whether or not an object has entered the monitoring distance range is output to the outside.

Next, the operation of the photoelectric reflective object detection device according to the present invention will be explained based on the timing chart of FIG. First, the control calculation unit 14 generates a sampling signal CTL at predetermined intervals. The signal CTL includes clock pulses arranged chronologically and sequentially at sampling timings TI, T2 .
T3°T4... is defined. The oscillator 8 oscillates for a time corresponding to the pulse width of the clock pulse in synchronization with these sampling timings, and outputs a sampling signal O8C on which a high frequency is superimposed.

Next, the drive unit 9 transmits the frequency-modulated drive current according to the high-frequency superimposed sampling signal O8C at a predetermined timing T.
I, T2, . . . are supplied to the light emitting element 2. The light emitting element 2 emits frequency-modulated light at timings Tl, T2 .
Release in the order of T3...

The photoreceptor element 6 receives all the light components collected by the reflective optical system and continuously outputs a detection current having an amplitude change according to the change in the focused light intensity.

An AC amplifying unit IO detects and amplifies the detected current, and outputs an AC detected current AC. This detection removes all noise components included in the primary detection current, so that the signal component of the alternating current detection current AC substantially includes only the signal component included in the light emission. In other words, the incident light side and the reflected light condensing side completely correspond in terms of signals.

Now, as shown in FIG. 4, it is assumed that the object 4 enters the monitoring distance range at time T between sampling timings T3 and T14. Then, before the approach time T, each sampling timing TI.

At T2 and T3, the alternating current detection signal AC is substantially equal to zero because the light receiving element 6 does not receive reflected light from the object, or it is due to the enclosing of the incident light or the reflection from surrounding reflective objects. Due to its extremely small amplitude. On the other hand, at the sampling timing T4 immediately after the entry time T, the °C1 AC detection signal AC has a large amplitude in response to the fact that the light reflected from the object 4 and then collected is received by the photoreceptor element 6.

Next, 14 smoothing section II smoothes the AC detection signal AC L7
DC detection signal DC having a peak value corresponding to its amplitude value
Convert to The conversion unit 12 is synchronized with the sampling signal CTL at a predetermined timing T1. T2゜T3...
- digitizes the analog DC detection signal DC and sequentially outputs sampling data DATA corresponding to each peak value.

Finally, the sampling data DATA is alternately recorded in a pair of memory areas M1 and M2 of the memory section 13 and updated with the latest data. For example, data generated at timing T1 is written to area M1, and data generated at timing T2 is written to area M2. Next, the data generated at timing T3 is written here after erasing the recorded data in area M1, and the data generated at timing T4 is written here after erasing the recorded data in area M2. The control calculation unit 14 addresses a pair of memory areas M1 and M2 at predetermined intervals and reads a pair of updated data. A relative ratio between the two is calculated. Object entry point T
Since there is no change in the value of the sampling data in the past, the relative ratio is close to the value 1. However, when the sampling data generated at timing T3 immediately before the object entry point and the sampling data generated at timing T4 immediately after are compared, their values are significantly different, so the relative ratio changes greatly from the value 1 and exceeds the set threshold. Accordingly, the output signal OU
T is switched from a low level to a high level as shown to identify the fact of object entry.

In the above example, the presence or absence of an object's entry was determined by relatively comparing the sampling data that came before and after the time, but instead of or in combination with this, it is possible to set the sampling data absolutely at appropriate time intervals. It may be determined whether an object has entered or not by comparing it with the reference value obtained. In particular, in the present invention,
Absolute comparison is also effective because the value of the sampling data increases only when the object enters the monitoring distance range.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to detect only objects that have entered the set monitoring distance range, so that the target object can be detected without causing false detections due to reflections from distant foreign objects, etc. This has the effect of being able to identify only objects.

Furthermore, since intermittent incident light synchronized with the sampling timing is used, there is an effect that the approach of an object can be monitored substantially in real time.

[Brief explanation of drawings]

FIG. 1A is a conceptual diagram showing the overall configuration of a photoelectric object detection device according to the present invention, and shows a state where an object is at the shortest monitoring distance. FIG. 1B also shows the object at the longest monitoring distance. FIG. 1C also shows a state in which an object exists beyond the maximum monitoring distance. FIG. 2 is a partially enlarged view showing another embodiment of the photoelectric object detection device according to the present invention. FIG. 3 is a block diagram showing the overall circuit configuration of the photoelectric object detection device according to the present invention. FIG. 4 is used to explain the operation of the circuit shown in FIG. 3. DESCRIPTION OF SYMBOLS 1...Case, 3...Lens, 5...Condensing lens, 7...Reflector, 9...Drive part, 11...Smooth part, 13...Memory part, Mining chart 2... Light emitting element, 4... Object, 6... Photoreceptor element, 8... Oscillating section, 10... Amplifying section, 12... Conversion section, 14... Control Arithmetic section. Applicant Copal Co., Ltd. Q Figure 2

Claims (1)

[Claims] 1. A light emitting unit that generates light, an optical axis that passes through a monitoring area having a predetermined monitoring distance range and extends in the distance direction, and an incident light that emits light along the optical axis. an optical system, a reflective optical system that collects reflected light from an object that has entered the optical axis and focuses the light on a specific position in the light receiving area according to the distance of the object in the optical axis direction; and a reflective optical system that is arranged along the light receiving area and monitors the light receiving area. a finite photoreceptor element that receives only reflected light from an object that has entered within a distance;
A photoelectric object detection device comprising an output circuit section that generates an object detection signal when the photoreceptor element receives reflected light. 2. The photoelectric object detection device according to claim 1, wherein the finite photoreceptor element is arranged between a light collection position corresponding to the longest monitoring distance and a light collection position corresponding to the shortest monitoring distance. 3. The finite photoreceptor element has a light-receiving surface edge that coincides with the light focusing position corresponding to the maximum monitoring distance, and the reflective optical system directs reflected light from an object within the maximum monitoring distance onto the photoreceptor element. 2. The photoelectric object detection device according to claim 1, further comprising a reflecting mirror for condensing light. 4. The light emitting section includes a light emitting element that emits light intermittently in response to a sampling signal, and the output circuit section sequentially creates sampling data according to the intensity of the received reflected light, and outputs sampling data that comes and goes back and forth in time. The photoelectric object detection device according to claim 1, further comprising an arithmetic processing section that outputs an object detection signal when the relative ratio exceeds a set threshold. 5. The light emitting section includes a light emitting element that generates light modulated at a certain frequency, and the output circuit section includes a circuit that detects a modulated electrical signal corresponding to the intensity of reflected light supplied from the light receiving element. The photoelectric object detection device according to claim 1.