JPH0454472Y2 - - 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 an object detection device that can be applied to a sensor.

<Prior art> The Matsuto switch is a device that has been put into practical use as an object detection device that detects an object such as a human body and is used in a start switch to control the activation of a security alarm system or the opening/closing of an automatic door. , ultrasonic rays, microwave Doppler effect rays, infrared rays that utilize fluctuations in the radiated infrared flux based on the temperature difference between the background and the moving object, and rays that emit infrared rays and reflect from the object. There are those that detect changes in the amount of light, and those that detect the absolute amount of reflected light from an object that projects infrared rays.

However, each of the above methods has various drawbacks. In other words, since the detection area is determined by the mat shape, the detection area shape cannot be changed at the installation site, and since it is a mechanical detection method that uses human contact, it is not possible to use a non-contact type. The disadvantage is that it has a short lifespan compared to other products. Furthermore, since the detection area is not clear, it is difficult to set and change the shape of the detection area, and in addition, there is a defect that the detection area cannot be detected when the human body is stationary. Furthermore, the detection area and the detection area are clear, and it is easy to set and change, and since it is a non-contact type, it has a long life.
Although it has been widely used in recent years, there is a problem that it cannot be detected when the human body is stationary because there is no change in the infrared light flux or light amount.
Therefore, when used as a sensor for an automatic opening/closing door, the emitter and receiver should be placed opposite each other on the left and right side walls of the door to prevent the door from closing if a person stops in the vicinity of the door. It is necessary to provide the attached safety beam device separately from the sensor for detecting the detection area, which requires extra equipment. Furthermore, although objects can be detected even when the human body is stationary, the detection distance is limited because the presence of the object is detected at a position where the projected and received beams intersect.

Therefore, as a means to reliably detect a human body even when it is stationary, and also to detect moving objects without being subject to any limitations on light intensity or detection distance, we have developed an object based on the triangulation method as shown in Figure 3. Detection methods are attracting attention. To explain this, a light emitting element 1 such as a light emitting diode or a laser diode, a light emitting lens 2 that forms a light emitting beam P, and an oscillation circuit (not shown) that generates a synchronization signal that sets the light emitting timing. A drive circuit that drives the light emitting element 1 based on this synchronization signal forms a light projecting section 3 that projects a detection beam P made of pulse modulated light onto the objects H1 and H2 to be detected. The light receiving section 4 is arranged side by side with a predetermined distance l from the light projecting section 3 and is arranged in a triangular manner with respect to the light projecting section 3 and the objects H1 and H2 to be detected. includes a light-receiving lens 5 made of a convex lens for condensing the reflected lights R1 and R2 from the objects H1 and H2 to be detected, and a light-receiving lens 5 disposed on the light-converging surface of the light-receiving lens 5 and positioned at the light-converging spots S1 and S2. It is composed of a position detection element 6 that outputs a corresponding position signal. In the figure, the distances from the light emitting lens 2 to each detected object H1 and H2 are D1 and D2, the focal length of the light receiving lens 5 is f, and the distance between each optical axis of the light emitting lens 2 and the light receiving lens 5 is The base line length is l, and the distances from the midpoint of the position detection element 6 to each of the focusing spots S1 and S2 are X.
1, X2, l/D1=X1/f, l/D
2=X2/f, X1=l×f/D1, X2
The relationship: =l×f/D2 holds true. That is, the distance D from the light projection lens 3 to the detected objects H1 and H2
1, D2 is a condensing spot S of the position detection element 6
1, it can be detected by the position of S2. Next, regarding the position detection element 6, FIGS.
This will be explained based on the diagram.

In FIG. 4, as the position detection element 6,
PSD (POSITION−SENSITIVE−
A known semiconductor position detection element called DETECTORS is shown. To explain briefly, there is a P layer 6a on the front surface of a flat silicon plate, an N layer 6b on the back surface,
It is composed of three layers, including the I layer 6c in the middle.
The light P incident thereon is photoelectrically converted, flows as a photocurrent in both directions indicated by arrows in the P layer 6a, and is divided and outputted from the respective electrodes T1 and T2. That is,
When the light P is incident, a charge proportional to the light energy is generated at the incident position, and this generated charge is output as a photocurrent from the electrodes T1 and T2 through the P layer 6a, which is a resistive layer. Here, since the P layer 6a is formed to have a uniform resistance value over the entire surface, the photocurrent is divided in inverse proportion to the distance to the electrodes T1 and T2, that is, the resistance value. For example, both electrodes T1, T2
If the distance between them is 2L, the photocurrent I ₀ and the currents taken out from both electrodes T1 and T2 are I1 and I2, then when the center is the origin, the distance x1 from the origin to the incident position of the light P is: It can be determined from I1/I2=L-x1/L+x1. On the other hand, when one end is set as the origin, the distance x2 from the origin to the incident position of the light P can be found from I1/I2=2L−x2/x2, and this distance x2 and the photocurrent I ₀
The relationship with is shown in FIG. in this case,
The incident position of the light P can be determined regardless of the incident energy.

<Problems to be solved by the invention> By the way, at the downstream of the light receiving section 4 described above, there is an arithmetic circuit that calculates the distance from the output signal of the light receiving section 4 to the objects H1 and H2 to be detected, and the output of this arithmetic circuit. A comparison circuit or the like is provided to compare whether or not the level is above the operating level. Therefore, as shown in Figure 6, 2
A pair of light emitting parts 3A, 3B and light receiving parts 4A, 4B are provided in the upper part of the door 7, and the door 7 of the object to be detected is
When an approach detection area DE1 for detecting the approach to the door 7 and a safety detection area DE2 for detecting the presence of an object near the door 7 are provided, the detection area DE1 corresponds to each of the light receiving sections 4A and 4B. Therefore, it is necessary to provide a circuit configuration such as an arithmetic circuit, which results in a problem that the configuration becomes complicated and the cost increases.

Therefore, some methods have attempted to reduce costs by using a single arithmetic circuit and sequentially inputting the output signals of the light receiving sections 4A and 4B to this arithmetic circuit by switching the output signals of the light receiving sections 4A and 4B. There is a drawback that switching noise is mixed into the output small signal, resulting in easy malfunction. In addition, each light receiving section 4
It is possible to combine the outputs of A and 4B and input them into a single arithmetic circuit, but since the arithmetic circuit outputs a signal that is the average of the outputs of each light receiving section 4A and 4B, Even though objects within the detection areas DE1 and DE2 are being detected, there is a risk of malfunction in which the output level of the arithmetic circuit is averaged and falls below the set operating level of the comparator circuit. This results in very inaccurate detection.
It will never be put into practical use.

<Purpose of the invention> The present invention was devised in view of these problems, and is a simplified and inexpensive method that can calculate the output signals of multiple light receiving sections constituting multiple detection areas with a single calculation circuit. The object of the present invention is to provide an object detection device that can accurately detect the position or presence or absence of an object in each detection area.

<Means for Solving the Problems> In order to achieve the above-mentioned purpose, the object detection device of the present invention detects the reflected light from the detected object of the light beam emitted from the light projector toward a predetermined detection area. ,
The light is received by a light receiving section arranged in a triangular manner with respect to the light projecting section and the object to be detected, and the reflected light is determined by the incident position of the reflected light derived from two types of light receiving outputs from both output terminals of the light receiving section. In an object detection device that detects a distance from a distance to a detected object and detects the position or presence or absence of the detected object within a detection area based on this detected distance, a plurality of sets of the projections that set a plurality of detection areas are used. A light section and a light receiving section, a drive circuit that outputs a drive signal to selectively and sequentially drive each of the light projecting sections, and one output terminal of each of the light receiving sections and the other output terminals of each of the light receiving sections are common to each other. a single arithmetic circuit that sequentially calculates the incident position of reflected light based on two types of output currents of each of the light receiving sections corresponding to each of the light projecting sections connected to both input ends and sequentially driven; sample and hold circuits having the same number of light receiving sections, each input terminal of which is commonly connected to the output terminal of the arithmetic circuit, and selectively and sequentially driven in synchronization with the drive signal of the drive circuit; The gist is the structure consisting of the following.

<Operation> In the object detection device of the present invention configured as described above, since each light emitting section is selectively and sequentially driven by the drive circuit, each light receiving section paired with each light emitting section is also selectively and sequentially driven. Two types of currents that are received and output from both output terminals of each light receiving section are sequentially input to a single arithmetic circuit, and in the arithmetic circuit, the two types of input currents that are sequentially input are sent to each light receiving section. The incident positions of each reflected light are calculated and output in the order of input, and this output signal is synchronized to individual sample and hold circuits that are sequentially driven in synchronization with the signal output of the drum circuit that drives each light projector. Detected.
As a result, the operation is equivalent to when each pair of light emitter and light receiver that sets each detection area is driven individually and sequentially, and the object to be detected can be accurately detected in any detection area. I can do it.

<Example> Hereinafter, a preferred example of the present invention will be described in detail based on the drawings.

In FIG. 1, for example, two light projecting units 3A and 3B, which are equivalent to those shown in FIG. Ru. Each light receiving section 4A, 4 corresponding to each light emitting section 3A, 3B
A reverse bias is applied to the midpoint of B from a bias power supply _VB , and one end and the other end of each light receiving section 4A, 4B are commonly connected to each other and connected to individual amplifiers 10, 11. There is. The output terminals of the amplifiers 10 and 11 are each connected to a single arithmetic circuit 12, and the output terminal of the arithmetic circuit 12 has a
Two sample and hold circuits 13 and 14 that are individually driven in synchronization with the signal output of a drive circuit 9 that sequentially drives each of the light projecting sections 3A and 3B are connected, and both sample and hold circuits 13 and 14 are connected to each other.
The output sides of are led out as distance detection signal output terminals 15 and 16, respectively, which are connected to a comparison circuit (not shown).

Next, the operation of the apparatus of the embodiment will be explained with reference to FIG.

The oscillator 8 outputs a timing signal with a constant period as shown in FIG. 2a. Both output terminals 9a and 9b of the drive circuit 9 to which this timing signal is input output drive signals that are synchronized with every other pulse of the timing signal, as shown in Figures b and c, respectively. is,
By these drive signals, the light projecting section 3A,
3B are driven alternately to emit a projected beam, and the reflected light is received by the corresponding light receiving sections 4A, 4B, so the light is alternately received by each light receiving section 4A, 4B, and both The output signals of the light receiving sections 4A and 4B are amplified by amplifiers 10 and 11, respectively, and then calculated by an arithmetic circuit 12 and output. The output signal of this arithmetic circuit 12 has a waveform in which the detection signal Sa from one light receiving section 4A and the detection signal Sb from the other light receiving section 4B are output alternately, as shown in Fig. d. The sample and hold circuits 13 and 14 are output to the sample and hold circuits 13 and 14, but since each sample and hold circuit 13 and 14 is driven alternately in synchronization with the drive signal from each output terminal 9a and 9b of the drive circuit 9, one sample The hold circuit 13 synchronously detects only the detection signal Sa of the output signals of the arithmetic circuit 12, and outputs a distance detection signal as shown in FIG. Similarly, the other sample and hold circuit 14 synchronously detects only the detection signal Sb of the output signals of the arithmetic circuit 12,
It outputs a distance detection signal as shown in the figure f.

<Effects of the invention> As detailed above, according to the object detection device of the present invention, in a device provided with multiple sets of light emitting parts and light receiving parts constituting a plurality of detection areas, each light emitting part can be driven by a drive circuit. The two types of current that are selectively driven sequentially and sequentially received by each light receiving unit paired with each light emitting unit and output from each light receiving unit are processed through a single calculation through two types of common connection lines. The structure is such that the signals that are input to the circuit and output in time series from this arithmetic circuit according to the input are sequentially input to each sample and hold circuit that is selectively driven sequentially in synchronization with the drive circuit. For multiple sets of emitters and receivers, signals output in time series from a single arithmetic circuit can be distributed to individual sample hold circuits driven at the drive timing of the emitter and sampled. , only a single arithmetic circuit needs to be provided, and since the output signal level of the light-receiving element used in this type of light-receiving section is low, the amplifier that is inevitably provided is also required depending on the number of pairs of light-emitting section and light-receiving section. Regardless, only two pieces are required, which greatly simplifies the configuration and achieves significant cost reductions.

Additionally, by selectively and sequentially driving each light emitter with a drive circuit, there is no need for a switch or the like to switch and input the output of the light receiver to a single arithmetic circuit, and switching noise is completely eliminated. Become. Furthermore, the output signals of each light receiving section are calculated individually and output individually without being combined.
Even though a single calculation circuit is used for multiple detection areas, signal processing can be performed for each detection area.
The object to be detected can be accurately detected in each detection area.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the object detection device of the present invention, Fig. 2 a to f is a timing chart showing the operating voltage of each part in Fig. 1, and Fig. 3 is a part of Fig. 1. An optical diagram showing the configuration, FIG. 4 is a partially schematic front view of FIG. 3, FIG. 5 is a diagram of the relationship between photocurrent I ₀ and distance X2 in FIG. 4, and FIG. be. 3, 3A, 3B... Light projecting section, 4, 4A, 4B...
...Light receiving section, 9...Drive circuit, 12...Arithmetic circuit, 13, 14...Sample hold circuit, DE
1, DE2...detection area, P...projection beam,
R, R1, R2...Reflected light, H1, H2... Object to be detected.

Claims (1)

[Scope of utility model registration request] The light reflected by the object to be detected of the projection beam emitted from the projection part towards a predetermined detection area is received by the light receiving part which is arranged in a triangular manner with respect to the projection part and the object to be detected. The distance from the light emitter to the object to be detected is detected based on the incident position of the reflected light derived from the two types of light reception outputs from both output terminals of the unit, and based on this detected distance, the distance of the object to be detected within the detection area is detected. In an object detection device that detects a position or the presence or absence of an object, a plurality of sets of the light projecting section and the light receiving section that set a plurality of detection areas, and a drive signal that selectively sequentially drives each of the light projecting sections are output. A drive circuit, and each of the light receiving sections corresponding to each of the light emitting sections connected to both input terminals and sequentially driven by commonly connecting one output terminal and the other output terminal of each of the light receiving sections to each other. a single arithmetic circuit that sequentially calculates the incident position of the reflected light using two types of output current of the section, and a single arithmetic circuit having the same number of light receiving sections as the light receiving section, each of which has an input terminal commonly connected to an output terminal of the arithmetic circuit. An object detection device comprising: a sample and hold circuit that is selectively driven sequentially in synchronization with the drive signal of the drive circuit.