JPH0430552Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial application field> The present invention is used to control the opening and closing of automatic doors and the operation of security alarm devices by detecting the presence or absence of a human body, etc., within a predetermined detection area, for example. The present invention relates to a photoelectric sensor for object detection that can be applied to a starting sensor.

<Prior art> Conventionally, various types of non-contact photoelectric sensors have been used to detect objects such as human bodies and to activate security alarm systems and start switches to control the opening and closing of automatic doors. Something has been devised and is already in practical use. Among these, reflective object detection photoelectric sensors that receive reflected light of visible light, infrared light, etc. projected from a projector include those that detect changes in the amount of reflected light from an object, and those that detect changes in the amount of light reflected from an object. There is a device that detects the absolute amount of reflected light.

<Problems to be solved by the invention> However, devices that detect changes in light intensity have the disadvantage that they cannot be detected when the human body is stationary because there is no change in light intensity. This poses a safety problem, as there is a risk that if a person stops in the vicinity of the door, the door will close and the person will be trapped.
On the other hand, devices that detect the amount of light received are extremely difficult to adjust during installation because they are affected by the magnitude of the light amount due to differences in the reflectance of the background and the sensing object. Moreover, when the detection sensitivity is increased to detect objects at a relatively long distance, a detection signal is erroneously output even though there is no human body when there is a background with high reflectance at a short distance. Therefore, since it is necessary to lower the detection sensitivity, there is a drawback that the detection distance becomes short. Therefore, if both of the above-mentioned detection mechanisms are incorporated into one device, the entire device becomes large, and the configuration becomes complicated and expensive.

<Purpose of the invention> The present invention was devised in view of these conventional problems.With a simple configuration, it is possible to reliably detect a human body even when it is stationary, and it does not require complicated adjustments for installation. Furthermore, it is an object of the present invention to provide a photoelectric sensor for detecting an object that can detect objects at a relatively long distance without being affected by the background.

<Means for Solving the Problems> In order to achieve the above object, the photoelectric sensor for object detection of the present invention emits light beams such as visible light and infrared light from a light projecting means toward a predetermined detection area at regular intervals. Reflection-type object detection that projects the light beam as pulse-modulated light, receives the reflected light from the object to be detected by a light receiving means, photoelectrically converts it, and detects the presence or absence of the object to be detected within the detection area based on this electrical signal. In the photoelectric sensor for use, a received light amount detection circuit includes a pair of the light emitting means and the light receiving means arranged in parallel, and samples a received light signal of the light receiving means in synchronization with the fixed period and converts it into a signal corresponding to the amount of received light. , a received light fluctuation amount detection circuit that converts the output signal of the received light amount detection circuit into an amplified signal corresponding to the increase/decrease thereof, and a received light amount detection circuit that compares the output signal level of the received light amount detection circuit with a set level and determines that the level is equal to or higher than the set level. a first comparison circuit that outputs a signal when the received light fluctuation amount detection circuit is compared with the upper and lower limit set levels, and a second comparison circuit that outputs a signal when it is determined that the output signal is outside the range between the two set levels. The present invention is characterized by a configuration including a circuit and an OR circuit that outputs an object detection signal when a signal is input from at least one of the comparison circuits.

<Operation> Although the configuration is simple, with only one set of light emitting means and one set of light receiving means, two types of signals can be generated by inputting the received light signal of the light receiving means to the received light fluctuation amount detection circuit and the received light amount detection circuit. Because it is decomposed into two parts, it is possible to detect both changes in the amount of received light and the absolute amount of received light at the same time. Therefore, when applied to a start switch for an automatic opening/closing door, if the first comparison circuit is set to a high setting level and the detection sensitivity of object detection based on the amount of received light is set to a low value, the influence of differences in background reflectance can be minimized. Since it does not receive any damage, adjustment at the time of installation becomes easy. In addition, even if the detection sensitivity is set low as described above, the object detection means based on the amount of received light has no problem in detecting objects at a short distance right near the door, and can detect a stationary human body or the like near the door.
Objects that are relatively far away can be detected by the light reception fluctuation amount detection circuit and the second comparison circuit.

<Embodiments> Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

In FIG. 1, an oscillator 1 that generates a synchronization signal that sets the light projection timing, a light emitting element 2 that is driven to emit light based on this synchronizing signal, and a light emitting element 2 that detects a detected object 4 by using the light emitted from the light emitting element 2. Optical system 3 consisting of a projection lens that projects light toward the detection area of
The light projecting means is constituted by the above. On the other hand, the light receiving means for receiving and photoelectrically converting the reflected light from the detected object 4 of the light beam from the light projecting means includes an optical system 5 consisting of a convex lens for condensing the reflected light from the detected object 4, and this optical system. The light-receiving element 6 is disposed on the light-converging surface of the light-receiving element 5 and converts the amount of received light into an electric signal corresponding to the amount of light received, and an amplifying section 7 that amplifies the output electric signal of the light-receiving element 6. This amplification section 7
The output signal is input to a received light amount detection circuit 8 consisting of a sample and hold circuit, and a first comparison circuit 9 compares and determines the magnitude of the signal corresponding to the received light amount output from the received light amount detection circuit 8.

On the other hand, the output signal of the received light amount detection circuit 8 is input to a received light fluctuation amount detection circuit 12 consisting of a differential capacitor 10 and an AC amplifier 11, and the change in the output signal of this received light fluctuation amount detection circuit 12 is used as a second comparison. The circuit 13 compares and discriminates. Both comparison circuits 9, 13
The output is output as an object detection signal via the OR circuit 14, and the output section 15 outputs, for example, a door opening/closing signal.

Next, the operation of the above-mentioned embodiment device will be explained in FIGS. 2 to 4.
This will be explained with reference to the figures.

FIGS. 3 and 4 are explanatory diagrams of the case where the activation switch S is applied to an automatic opening/closing door. As shown in FIG. The sensor is installed facing a predetermined detection area E in front of the sensor. Furthermore, as shown in Fig. 4, a light projector A as a light projecting means and a light receiver B as a light receiving means are arranged close to each other in parallel. It is set not to project directly onto the floor surface of light receiving area B'. The reason for this is that when the projected light beam A' is projected while matching the light receiving area B', the light reflected by the floor surface of the light receiving area B' is always received by the light receiver B.

In the projector A, the light emitting element 2 is driven to emit light by a synchronizing signal whose waveform is shown in FIG. has been done.
Now, as shown in FIG. 3, the human body H approaches the automatic opening/closing door D as shown by the arrow, and in FIG.
During the time period, the vehicle enters the detection area E and approaches the automatic door D, stops within the detection area E during the time period T3, and then walks away from the automatic door D during the time period T4. , T5, the case will be explained assuming that the detection area E is outside the detection area E. Since there is no human body within the detection area E during the time period T1, the light receiving element 6 detects the light receiving area as shown in FIG. 2b.
A minute pulse signal is output by photoelectrically converting the reflected light from the background, which is the floor surface of B', and T2, T3, T
In each of the four time periods, a pulse signal corresponding to the amount of reflected light from the human body H is output from the light receiving element 6, as shown in FIG. 2b. This light receiving element 6
After the output pulse signal of A sample-and-hold signal with a waveform corresponding to the amount is output.

This sample hold signal is sent to the first comparator circuit 9.
and output to the received light fluctuation amount detection circuit 12, respectively. First, in the first comparator circuit 9, the sample-and-hold signal is compared with the set level shown by the broken line in FIG. 2c, and as shown in FIG. A level determination signal is output to the OR circuit 14. On the other hand, in the received light fluctuation amount detection circuit 12, the sample and hold signal is differentiated by the capacitor 10 to extract the increase/decrease amount, and the extracted signal is
The AC amplifier 11 amplifies and outputs a signal with a waveform corresponding to the change in the amount of received light as shown in FIG. , and the lower limit setting level, and a high level determination signal is output only when the input signal is outside the upper and lower limit setting level ranges, as shown in FIG. 2(f). The judgment signals from both comparison circuits 9 and 13 are logically summed by an OR circuit 14, and an object detection signal having a waveform as shown in FIG. 2g is outputted to an output section 15. As is clear from the positional relationship between the human body and the detection area E in each time period T1 to T5 shown in FIG. This serves as a detection signal for the presence within E.

As is clear from a comparison between FIG. 2b and FIG. 2f, the presence of a human body within the detection area E can be detected by the light receiving fluctuation detection circuit 12 unless the human body H stands still. To explain this in detail with reference to FIG. 3, the movement of the human body H can be detected by the human body H blocking most of the light rays L1 indicated by L1. In other words, when the human body H moves within the range indicated by E1, this can be detected by the light reception fluctuation amount detection circuit 12. In this way, the human body H that is relatively far away from the door D can be detected by the light receiving fluctuation amount detection circuit 12.
With the detection means based on the amount of received light that can also detect a stationary state, it is only necessary to detect the presence or absence of the human body H near the door D. Therefore, Figure 2c
The detection sensitivity of the human body H is set low by increasing the setting level of the first comparison circuit 9, which is indicated by a broken line. Therefore, the means for detecting the amount of received light using the received light amount detection circuit 8 and the first comparison circuit 9 detects only when the human body H blocks the light ray at a short distance indicated by L2 of the light ray L shown in FIG. can. That is, door D indicated by E2
Only the presence of the human body H in the vicinity of is detected. In this way, by setting the detection sensitivity of the amount of received light to a low level, it is almost unaffected by differences in the reflectance of the background, so there is no need to make complicated adjustments during installation, and there is no need to make complicated adjustments at the time of installation. Due to the light, it is possible to prevent a malfunction in which a detection signal is output even though the human body H is not present. In particular, malfunctions caused by high reflectance of the background at a relatively long distance from the door D are completely eliminated.

When this photoelectric sensor is applied as a starting switch for an automatic opening/closing door D, the light reception variation detection circuit 12 detects a human body H that is relatively far away from the door D, and the human body H is detected to be in front of the door D. The door D can be opened in advance before reaching the door D, and even if the human body H stops right next to the door D, the amount of received light detection circuit 8 and the first comparison circuit 9 can be used. The human body H can be detected by the detection means, and there is no problem of being caught between the door D when it is closed, and it is safe.

In the above embodiment, the case where one set of light projecting means and one set of light receiving means was provided was explained as an example, but the present invention is not limited to this. Of course, it is possible to include various modifications such as setting detection areas, or combining the light reception signals from multiple sets of light receiving means corresponding to the plurality of detection areas, and then decomposing them into two types of signals. be.

<Effects of the invention> As described above, the photoelectric switch for object detection of the present invention is configured such that the light receiving signal of a single light receiving means is divided into two types of signals by the light receiving amount detection circuit and the light receiving fluctuation amount detection circuit, and each of these signals is compared and judged with a set level by an individual comparison circuit, and the output of both comparison circuits is passed through an OR circuit to generate an object detection signal by at least one of the signal outputs, so that a human body at a long distance can be detected by the light receiving fluctuation amount, and the detection sensitivity of the object detection means based on the light receiving amount can be set low, which eliminates the need for complicated adjustments during installation and prevents malfunctions due to a background with good reflectivity. In addition, the object detection means based on the light receiving amount with the above-mentioned detection sensitivity set low can detect objects at a short distance even when they are stationary, and when applied to the start switch of an automatic door opening and closing, it prevents troubles such as being caught in the door, making it safe. Moreover, since only one pair of light projecting means and light receiving means are provided, it has the advantage of being small and inexpensive.

[Brief explanation of the drawing]

Fig. 1 is a block configuration diagram of one embodiment of the photoelectric sensor for object detection of the present invention, Fig. 2 is a timing chart showing signal waveforms of each part in Fig. 1, and Figs. 3 and 4 are respectively for an automatic opening/closing door. FIG. 2 is an explanatory diagram when applied to a start switch. 2... Light emitting element, 4... Object to be detected, 6... Light receiving element, 8... Received light amount detection circuit, 9... First comparison circuit, 12... Received light variation amount detection circuit, 13...
Second comparison circuit, 14...OR circuit.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A light beam such as visible light or infrared light is projected from a light projecting means toward a predetermined detection area as pulse-modulated light with a constant period, and the light reflected by the object to be detected In a reflective object detection photoelectric sensor that receives and photoelectrically converts the detected object with a light receiving means and detects the presence or absence of a detected object within a detection area based on the electric signal, a pair of the light emitting means and the light receiving means are arranged in parallel. a received light amount detection circuit that samples the received light signal of the light receiving means in synchronization with the predetermined period and converts it into a signal corresponding to the amount of received light; and an amplified signal for the increase/decrease of the output signal of the received light amount detection circuit. a first comparison circuit that compares the output signal level of the received light amount detection circuit with a set level and outputs a signal when it is determined to be equal to or higher than the set level; and the received light fluctuation amount detection circuit. a second comparison circuit that compares the output signal of the output signal with upper and lower limit setting levels and outputs a signal when it is determined that the output signal is outside the range between the two setting levels; and a signal is input from at least one of the two comparison circuits. A photoelectric sensor for object detection, comprising an OR circuit that outputs an object detection signal. (2) The received light amount detection circuit is configured to sample and hold the light reception signal of the light receiving means in synchronization with the light projection timing of the light projecting means at a constant period, and the light reception fluctuation amount detection circuit is configured to sample and hold the light reception signal of the light receiving means in synchronization with the light projection timing of the light projecting means at a constant period. A photoelectric sensor for detecting an object according to claim 1, characterized in that the output signal of the quantity detection circuit is differentiated to extract an increase or decrease in the output signal, and the extracted signal is amplified.