JPH0441937B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Industrial Application Field This invention is a method of arranging a light projector and a light receiver with an optical coupling path gap in between, and determining the presence or absence and position of a specimen brought into the optical coupling path gap. , or detect the phase etc.
In a so-called photoelectric conversion system that outputs this as an electrical signal, a light emitter is driven in pulses, and the pulse-modulated light from the light emitter is received via an optical coupling path (test object detection section), allowing for highly accurate test object detection. This invention relates to a three-terminal type modulated light receiving photosensor that outputs a signal.

(b) Prior art and its problems As is well known, a photoelectric conversion detector connects a light emitting element 21 and a light receiving element 22 through an optical coupling path gap (LG), as shown in FIGS. 9B and 10B. ) and are often used as a device to optically detect the presence, position, phase, etc. of an object brought into the optical coupling path gap (LG). This photoelectric conversion detector includes a light emitting element 21 and a light receiving element 2.
Depending on the configuration of the optical coupling path (LG) between the two, a transmitted light type which brings the light from the light emitting element 21 directly to the light receiving element 22 via the optical coupling path (LG) as shown in FIG. 9B can be used. There is also a reflected light type, as shown in FIG. Both the transmitted-light type and the reflected-light type are configured with an optical coupling path gap between the light emitting element and the photodiode, so this is especially true when the light from the light emitting element is stationary light. However, it was difficult to eliminate the influence of noise caused by ambient light. In order to solve this problem and improve detection accuracy, a modulated light receiving type photosensor is known, which outputs a light emitting element as pulse modulated light with a constant period, receives this pulse modulated light, and outputs an electrical signal. . Conventional modulated light receiving photosensors for detecting this pulse modulated light have been required to be smaller by reducing the number of components, have high reliability, and be low in price. In response to these demands, photoelectric conversion detectors have conventionally been provided in which a pulse drive circuit, a pulse light detection circuit (including a photodiode section), and the like are fabricated as a semiconductor device using integrated circuit technology. Specifically, they are as follows: () On the light emitter side, a light emitting diode 21 and a pulse drive circuit 23 are integrated into one device, and on the light receiver side, a photodiode 22 and a pulse detection circuit 24 are integrated. (See Fig. 5). () On the photoreceiver side, a light-emitting diode pulse drive circuit 23 and a pulse detection circuit 24 including a photodiode 22 are integrally integrated. A photo sensor configured as a modulated light receiving type photo sensor formed into a circuit (No. 6)
and FIG. 7).

Among these conventional configuration examples, the configuration example () above requires integrated circuits on both the device side of the light emitting diode 21 and the device side of the modulated light receiving type photosensor 22, which requires an integrated circuit for device assembly. This method has the problems of an increase in man-hours and an increase in product cost due to an increase in the number of parts. On the other hand, the configuration example () above has a power supply terminal V _CC , an output terminal
It required four terminals: V _OUT , three terminals (GND), and a light emitting diode drive terminal (LED.T), which was an obstacle to further miniaturization as a modulated light receiving photosensor.

(c) Technical problems of the present invention Therefore, the present invention solves the problem of conventional pulse modulation light projection.
This is intended to eliminate the drawbacks and problems found in light-receiving type photoelectric conversion detection systems, and the circuit is configured to pulse-drive the light emitting diodes combined as the photoelectric conversion detection system, and the power supply terminal V _CC or ground terminal GND
To provide a modulated light-receiving type photosensor which is configured to have a circuit such that either one of the two terminals serves as a terminal for driving a light emitting diode, thereby reducing the number of terminals, downsizing the device, and reducing manufacturing costs. There is a particular thing.

(d) Technical Means of the Invention In order to achieve the above-mentioned object, the present invention specifically arranges a light projector and a light receiver across an optical coupling path gap, and This is a photoelectric conversion system that detects the presence, position, or phase of an object to be inspected and outputs it as an electrical signal.It drives a light emitter in pulses and connects the pulsed converted light from the light emitter to an optical coupling path. A modulated light receiving type photosensor that receives light through a terminal and outputs a detected electric signal, is provided with three terminals: a power supply terminal V _CC , a ground terminal GND, and an output terminal V _OUT , and between the power supply terminal and the ground terminal, A pulse type current consumption circuit including a transistor circuit section and a pulse oscillation circuit section, and a pulsed light detection circuit equipped with a photodiode are connected in parallel, and a light emitting diode element is connected in series to either the power supply terminal or the ground terminal. This is a modulated light receiving type photosensor that can be connected.

(e) Embodiments of the present invention Hereinafter, the modulated light receiving type photosensor according to the present invention will be described in detail based on specific embodiments shown in the drawings. Figure 1A and Figure 1B are
FIG. 2 is a block diagram showing the basic circuit configuration of a modulated light receiving type photosensor according to the present invention, especially the first one.
Figure A shows the light emitting diode element LED connected to the power terminal V _CC
Fig. 1B shows the connection mode in which the wires are connected in series.
Ground terminal for light emitting diode element (LED)
Shows the wiring configuration connected in series to GND. As shown in FIG. 1, a modulated light receiving type photosensor 1 according to the present invention basically comprises a pulse type current consumption circuit transistor circuit section 2, a pulse oscillation circuit section 3, and a photodiode 5. It has a circuit group of the photodetection circuit section 4, and a terminal group of a power supply terminal V _CC , a ground terminal GND, and an output terminal V _OUT . In this invention, the transistor circuit section 2, the pulse oscillation circuit section 3, and the pulse light detection circuit section 4 are connected to the power supply terminal V _CC and the ground terminal.
Connected in parallel with GND. A more detailed circuit configuration of the modulated light receiving photosensor according to the present invention will be explained based on FIG. 2.
The transistor circuit section 2 includes a transistor 6 and a resistance element (R). The collector of the transistor 6 is connected to the power supply terminal V _CC side, and the emitter is connected to the ground element GND through a resistor element (R).
The base is connected to the pulse oscillation circuit section 3. The pulse oscillation circuit section 3 includes a pulse oscillation circuit 7 for causing a light emitting diode (LED) to emit pulsed light, and a constant voltage circuit 8 connected in series to the pulse oscillation circuit 7. The pulse oscillation circuit 7 is directly connected to the base of the pulse type current consumption circuit transistor 6. On the other hand, the pulsed light detection circuit section 4 detects the presence or absence of pulsed light from a light emitting diode (LED), demodulates it, and outputs it.
It has a pulsed light detection circuit 9 and a constant voltage circuit 10 connected in series to the pulsed light detection circuit 9. Next, regarding the detailed circuit configuration of the pulsed light detection circuit 9 and the operation of the pulsed light detection circuit section 4,
This will be explained based on FIGS. 2 and 3. A light emitting diode (LED), when connected as shown in FIG. 2, outputs a steady output pulse e ₁ shown in FIG. 3. The pulsed light e ₁ output from the light emitting diode (LED) outputs a detection signal e ₂ to the photodiode side upon detection of the object. detection signal
e ₂ is converted into a voltage pulse by the photodiode 5, and is linearly amplified by the amplifier A ₁ while containing a DC component. The output of amplifier A ₁ passes through an integrating circuit consisting of resistor element R ₁ and capacitor element C ₁ ,
The signal _e3 is input to the non-inverting input terminal of the differential amplifier _A2 , and is input to the inverting input terminal of the differential amplifier _A2 after being voltage-effected by the resistor _R2 . As shown in FIG. 3, the differential amplifier _A2 amplifies only the pulse component and outputs it as a signal _e4 . The output _e4 of the differential amplifier _A2 is input to the comparator A3 via an integrating circuit consisting of a resistor _R4 and a capacitor _C2 , and _a resistor _R5 . Said comparator
Every time a pulse is input, A ₃ uses its output e ₅ to drive a current mirror circuit (CM) consisting of transistors Q ₁ and Q ₂ to charge a capacitor C ₃ . The capacitor _C3 is also discharged by a constant current source (I). As a result, when a pulse train is input, the + side potential e ₆ of capacitor C ₃
increases in a stepwise manner as shown in FIG. 3, and remains at a high potential while the pulse train is input to the differential amplifier _A3 . Furthermore, when the pulse train is no longer input to the differential amplifier A ₃ , the capacitor C ₃ is only discharged, and the potential drops. The positive potential e ₆ of the capacitor C ₃ is compared with a potential obtained by dividing the set value of the constant voltage circuit by resistors R ₆ and R ₇ in a comparator A ₄ . This potential is the signal (i.e. pulse train)
This is the threshold potential for determining the presence or absence of If the + side potential of capacitor _C3 exceeds the threshold potential, the comparator
_A4 determines that there is a signal, and its output _e7 turns on the output transistor _Q3 . On the other hand, when the + side potential of the capacitor C ₃ falls below the threshold potential, the comparator A ₄ determines that there is no signal and makes the output transistor Q ₃ non-conductive. The output of comparator A _{4 is}
By feeding back to the inverting input of the capacitor
Hysteresis can be added between the + side potential of _C3 and the output of comparator _A4 . This is effective in preventing chattering at the output terminal V _OUT .

In short, in the modulated light receiving photosensor according to the present invention, the light emitting diode element (LED) constantly emits light due to the current consumption of the circuit connected in parallel between the power supply terminal V _CC and the ground terminal GND. However, the current consumption of the circuit connected in parallel between the power supply terminal V _CC and the ground terminal GND is a combination of the pulse component flowing through the transistor 6 and the DC component flowing through the pulse oscillation circuit 7 and pulse light detection circuit 9. and a pulse light detection circuit section 4
As shown in Figure 2, for AC amplifier A ₂
By combining A2 and _A2 , the DC component is cut out, and only the pulse component is detected, as shown by the _A2 output and _A3 output in FIG. Therefore, even if the light emitting diode always emits light as described above, as is clear from the reasons described above, this does not prevent the device from functioning as a modulated light receiving photosensor.

As is clear from the circuit configuration shown in FIG. 2, the modulated light receiving type photosensor according to the present invention connects all capacitors C ₁ , C ₂ and C ₃ to the ground terminal GND side at one pole. Therefore, a polar junction capacitance can be applied. Since the area per unit capacitance of this junction capacitor is about 1/20 that of a MOS capacitor, the chip area when integrated into an integrated circuit can be reduced.

FIG. 4 shows an embodiment of the modulated light receiving type photosensor according to the present invention, which is mounted on a three-terminal type resin molded package 11. According to this embodiment, the photodiode 5 is arranged at the center of the integrated circuit chip 13 so as to be located at the focal point of the light receiving lens 12 in the photo sensor. The pulse oscillation circuit 7 and the pulse detection circuit 9 are arranged at positions separated by constant voltage circuits 8 and 10, respectively, provided individually for the purpose of preventing mutual interference. Further, the ground lines do not intersect with each other on the chip, but have separate ground electrode pads G ₁ and G ₂ and are connected to the lead frame. This design prevents common impedance.

(f) Effects of the present invention The modulated light receiving photosensor of the present invention having the above configuration has a power supply terminal V _CC or a ground terminal.
Since the circuit is configured such that one of the GND terminals is also used as a pulse drive terminal for the light emitting diode, the number of terminals for the modulated light receiving photosensor device is limited to the power supply terminal V _CC , the output terminal V _OUT , and the ground terminal. It can have three terminals: terminal GND. Furthermore, in this device, the circuit is configured such that all of the capacitors applied in the circuit are grounded on one side, so that polar junction capacitance can be used, and the chip area can be reduced. According to such a configuration, it is possible to reduce the size of the device, and in addition, it is possible to eliminate at least one connection to the light emitting diode, which is extremely effective in improving operability and reducing costs by adapting to mass production. It can be said that there is.

Furthermore, the modulated light receiving type photosensor according to the present invention drives a light emitting diode in pulses, and has the advantage of increasing the detection accuracy of the object to be detected and the ability to set a long optical coupling path. It can be said that this is extremely advantageous as a wide photo sensor.

[Brief explanation of drawings]

1A and 1B show the basic configuration of a modulated light receiving photosensor according to the present invention, and FIG. 1A shows a light emitting diode connected to a power terminal V _CC
FIG. 1B is a circuit diagram showing an example in which the light emitting diode is connected to the ground terminal GND, and FIG. 2 shows details of the circuit of the modulated light receiving photosensor according to the present invention. 3 is a waveform diagram showing the signals of each part in the circuit configuration example shown in FIG. 2; FIG. FIG. 5 is a schematic block diagram of a configuration example of a conventional photoelectric conversion detection system, FIG. 6 is a schematic block diagram of a transmission type device in a configuration example of a conventional photoelectric conversion detection system, and FIG. 7 is a schematic block diagram of a configuration example of a conventional photoelectric conversion detection system. FIGS. 8A and 8B, which are schematic block diagrams of a reflective device in a configuration example of a conventional photoelectric conversion detection system, show the appearance of the modulated light receiving photosensor of the present invention and the conventional modulated light receiving photosensor. 9A and 9B are schematic perspective views that compare and show examples of transmission type connections between a modulated light receiving photosensor of the present invention and a conventional modulated light receiving photosensor. ,
FIG. 10A and FIG. 10B are schematic perspective views illustrating a comparison of reflective connection examples of a modulated light receiving type photosensor of the present invention and a conventional modulated light receiving type photosensor. 1... Modulated light receiving type photosensor, 2... Transistor circuit section, 3... Pulse oscillation circuit section, 4...
Pulse light detection circuit section, 5... Photodiode, 6
...Transistor, 7...Pulse oscillation circuit, 8,
10... Constant voltage circuit, 9... Pulse light detection circuit,
V _CC ...Power supply terminal, V _OUT ...Output terminal, GND...
Ground terminal.

Claims (1)

[Claims] 1. A light emitter and a light receiver are placed across an optical coupling path gap, and the existence, position, phase, etc. of the object brought into the optical coupling path gap are detected, and this is detected by electrical signals. In a modulated light receiving type photosensor that outputs a detected electric signal by driving the light emitting device in pulses and receiving pulse modulated light from the light emitting device via an optical coupling path, the photoelectric conversion system outputs an output at a power source. A pulse type current consumption circuit comprising three terminals, a terminal V _CC , a ground terminal _GND , and an output terminal V _OUT , and including a transistor circuit section and a pulse oscillation circuit section between the power supply terminal V CC and the ground terminal GND; A modulated light receiving type photosensor, characterized in that a pulsed light detection circuit equipped with a photodiode is connected in parallel, and a light emitting diode element can be connected in series to either the power supply terminal V _CC or the ground terminal GND. . 2. The modulated light receiving type photosensor according to claim 1, wherein a constant voltage circuit is individually connected in series to the pulsed current consumption circuit and the pulsed light detection circuit. 3 the transistor for the pulse type current consumption circuit;
an integrated circuit element in which a pulse oscillation circuit, a pulse light detection circuit, a constant voltage circuit, and a photodiode are integrated into one chip; a power supply terminal V _CC of the integrated circuit element;
Claim 1 or 2, characterized in that the invention comprises three external electrodes connected to the output terminal V _OUT and the ground terminal GND by leads, respectively.
The modulated light receiving type photosensor described in 2.