IC for photoelectronic sensor and photoelectronic sensor

Abstract

To commonalize ICs for a large variety of types of photoelectronic sensors.SOLUTION: An IC for a photoelectronic sensor includes: a first light reception element and a second light reception element; a subtraction circuit; a switch circuit; and a control unit. The subtraction circuit outputs a differential signal as the difference between a first light reception signal which changes according to the amount of light reception of the first light reception element and a second light reception signal which changes according to the amount of light reception of the second light reception element. The switch circuit is a circuit which has a first input terminal in which at least one of the first light reception signal and the second light reception signal is input, a second input terminal in which the differential signal is input, and an output terminal and can switch between a setting of outputting a signal input to the first input terminal from the output terminal and a setting of outputting a signal input to the second input terminal from the output terminal according to the manner of usage of the IC for the photoelectronic sensor. The control unit switches the setting of the switch circuit according to a switch signal input from the outside to switch the manner of usage of the IC for the photoelectronic sensor.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an IC for a photoelectric sensor and a photoelectric sensor including the IC. [Background technology]

[0002] Photoelectric sensors include transmission type, reflection type, mirror reflection type, and distance setting reflection type. Transmission type, reflection type, and mirror reflection type photoelectric sensors detect the presence or absence of a detectable object based on the amount of light received by a light receiving element (see, for example, Patent Document 1). On the other hand, distance setting reflection type photoelectric sensors are configured such that the light receiving position of the light receiving element changes from a reference point (light receiving position when the detectable object is at a predetermined position) depending on the relative distance to the detectable object based on a predetermined position, and detect the relative distance to the detectable object based on the light receiving position (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-014360 A [Patent Document 2] JP 2006-226851 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, in these photoelectric sensors, various circuits (including light receiving elements) for making the photoelectric sensor function are often integrated into a single integrated circuit (ASIC). However, the circuit configuration (including the configuration of the light receiving element) for making the photoelectric sensor function differs between transmission type, reflection type, and mirror reflection type photoelectric sensors and distance setting reflection type photoelectric sensors depending on whether the detection target is the presence or absence of a detectable object or the relative distance to the detectable object, and therefore the integrated circuit (ASIC) must also be designed according to the type of photoelectric sensor.

[0005] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to standardize a photoelectric sensor IC for various types of photoelectric sensors. [Means for solving the problem]

[0006] The photoelectric sensor IC according to the present invention is an IC that can be used in common for at least one of a transmission type, a reflection type, and a mirror reflection type photoelectric sensor that detects the presence or absence of a detected object, and a distance setting reflection type photoelectric sensor that detects the relative distance to a detected object based on a predetermined position, and includes a first light receiving element and a second light receiving element, a subtraction circuit, a switching circuit, and a control unit. Here, the subtraction circuit outputs a difference signal that is the difference between a first light receiving signal that changes according to the amount of light received by the first light receiving element and a second light receiving signal that changes according to the amount of light received by the second light receiving element. The switching circuit has a first input terminal to which at least one of the first light receiving signal and the second light receiving signal is input, a second input terminal to which the differential signal is input, and an output terminal, and is capable of switching between a setting for outputting a signal input to the first input terminal from the output terminal when the IC is used for at least one of a transmission type, a reflection type, and a mirror reflection type photoelectric sensor, and a setting for outputting a signal input to the second input terminal from the output terminal when the IC is used for a distance setting reflection type photoelectric sensor.The control unit switches the setting of the switching circuit in response to a switching signal input from outside the IC to switch between using the IC for at least one of a transmission type, a reflection type, and a mirror reflection type photoelectric sensor and using the IC for a distance setting reflection type photoelectric sensor.

[0007] According to the above-mentioned photoelectric sensor IC, a circuit according to the type of photoelectric sensor can be constructed by simply switching the setting of the switching circuit. That is, when the photoelectric sensor IC is mounted on at least one of a transmission type, a reflection type, and a mirror reflection type photoelectric sensor, a circuit for detecting the presence or absence of a detected object can be constructed by switching the setting of the switching circuit in the photoelectric sensor IC to a setting in which a signal input to a first input terminal is output from an output terminal. On the other hand, when the photoelectric sensor IC is mounted on a distance setting reflection type photoelectric sensor, a circuit for detecting the relative distance to a detected object based on a predetermined position can be constructed by switching the setting of the switching circuit in the photoelectric sensor IC to a setting in which a signal input to a second input terminal is output from an output terminal.

[0008] The photoelectric sensor IC may further include an adder circuit that outputs a composite signal that is a composite of the first light receiving signal and the second light receiving signal. The composite signal may be input to the first input terminal. According to this configuration, when the switching circuit is set to output the signal input to the first input terminal from the output terminal, both of the lights incident on the first light receiving element and the second light receiving element are used to determine whether or not the object to be detected is present. On the other hand, when only one of the first light receiving signal and the second light receiving signal is input to the first input terminal, only the light incident on the first light receiving element or the second light receiving element connected to the first input terminal is used to determine whether or not the object to be detected is present. Therefore, according to the above configuration, the light receiving area can be increased.

[0009] The photoelectric sensor IC may further include an amplifier circuit that amplifies the output signal from the switching circuit. The control unit may determine the detection state of the object to be detected using the output signal amplified by the amplifier circuit. By performing amplification on the output side of the switching circuit in this manner, only one amplifier circuit is required for the photoelectric sensor IC, and therefore the circuit can be simplified compared to the case where amplification is performed on the input side of the switching circuit (i.e., the case where two amplifier circuits are required).

[0010] The photoelectric sensor IC may further include an integrating circuit that integrates the amplitude of the output signal amplified by the amplifier circuit over time, and a comparing circuit that compares the integrated value obtained by the integrating circuit with a reference value. The control unit may then determine the detection state of the object to be detected based on the comparison result of the comparing circuit. With this configuration, the integrating circuit calculates the integrated value per period, thereby making it possible to obtain accurate detection results for each period. This makes it possible to improve the detection accuracy of the photoelectric sensor.

[0011] The photoelectric sensor of the present invention is a photoelectric sensor equipped with a photoelectric sensor IC, and when the photoelectric sensor is any of a transmission type, a reflection type, and a mirror reflection type, the setting of the switching circuit in the photoelectric sensor IC is switched to a setting where a signal input to the first input terminal is output from the output terminal, and when the photoelectric sensor is a distance setting reflection type, the setting of the switching circuit in the photoelectric sensor IC is switched to a setting where a signal input to the second input terminal is output from the output terminal. Effect of the Invention

[0012] According to the present invention, it becomes possible to standardize a photoelectric sensor IC for various types of photoelectric sensors. [Brief description of the drawings]

[0013] [Figure 1] 1 is a cutaway perspective view conceptually showing a photoelectric sensor according to an embodiment; [Diagram 2] 1 is a conceptual diagram showing a configuration of a photoelectric sensor IC according to an embodiment of the present invention. [Diagram 3] 1A and 1B are explanatory diagrams of a detection method using the principle of triangulation. [Figure 4] 1 is a conceptual diagram showing two examples of pulsed light used as light for detection. [Diagram 5] FIG. 13 is a conceptual diagram showing a configuration of a photoelectric sensor IC according to a first modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] [1] Implementation Example [1-1] Photoelectric sensor configuration Fig. 1 is a cutaway perspective view conceptually showing a photoelectric sensor according to an embodiment. As shown in Fig. 1, the photoelectric sensor according to this embodiment includes a case 1, a board 2 installed in the case 1, a light-projecting element 3 and a photoelectric sensor IC 4 mounted on the surface of the board 2, and a cord 5 including a power line and a signal line.

[0015] The light-projecting element 3 is an element that emits light (detection light) for detecting a detected object, such as an LED or a semiconductor laser. The photoelectric sensor IC 4 has a light-receiving section 41. The case 1 is provided with a light-projecting / receiving window 11, and the light-projecting element 3 and the photoelectric sensor IC 4 are arranged so that the light emitted by the light-projecting element 3 passes through the light-projecting / receiving window 11, and part of the light that is reflected by the detected object or the reflector passes through the light-projecting / receiving window 11 again and enters the light-receiving section 41.

[0016] Thus, the photoelectric sensor of this embodiment is a photoelectric sensor that emits detection light from its own light-projecting element 3, and is a reflective or mirror-reflection type photoelectric sensor that detects the presence or absence of a detected object, or a distance-setting reflective type photoelectric sensor that detects the relative distance to a detected object based on a predetermined position P0 (see FIG. 3). Note that the photoelectric sensor of this embodiment may also be used as a transmission type photoelectric sensor that does not emit light from the light-projecting element 3, and detects light emitted by a light-projecting device provided separately from the photoelectric sensor with a light-receiving unit 41.

[0017] Conventionally, the circuit configuration for functioning a photoelectric sensor differed between transmission type, reflection type, and mirror reflection type photoelectric sensors and distance setting reflection type photoelectric sensors depending on whether the detection target was the presence or absence of an object to be detected or the relative distance to the object to be detected, and the photoelectric sensor IC 4 was also forced to be designed according to the type of photoelectric sensor.

[0018] In this embodiment, the photoelectric sensor IC 4 is configured to be common to at least one of the transmission type, reflection type, and mirror reflection type photoelectric sensors and the distance setting reflection type photoelectric sensor. The configuration of the photoelectric sensor IC 4 will be specifically described below.

[0019] [1-2] Structure of photoelectric sensor IC Fig. 2 is a conceptual diagram showing the configuration of the photoelectric sensor IC 4 according to this embodiment. As shown in Fig. 2, the photoelectric sensor IC 4 according to this embodiment includes a first light receiving element 41A and a second light receiving element 41B as a light receiving unit 41. Furthermore, the photoelectric sensor IC 4 includes a subtraction circuit 42, a switching circuit 43, an amplifier circuit 44, an integration circuit 45, a comparison circuit 46, and a control unit 49.

[0020] The first light receiving element 41A is, for example, a photodiode, and converts the light incident on the light receiving surface into an electrical signal and outputs the electrical signal to output a first light receiving signal S1 that changes according to the amount of light received at that time. Similarly, the second light receiving element 41B is, for example, a photodiode, and converts the light incident on the light receiving surface into an electrical signal and outputs a second light receiving signal S2 that changes according to the amount of light received at that time.

[0021] In this embodiment, the first light receiving element 41A and the second light receiving element 41B are disposed adjacent to each other so that their light receiving surfaces are continuous, and the first light receiving element 41A is disposed on the opposite side of the second light receiving element 41B to the light projecting element 3. The first light receiving signal S1 and the second light receiving signal S2 output by them are used as follows for each type of photoelectric sensor.

[0022] In the transmission type, reflection type, and mirror reflection type photoelectric sensors, the presence or absence of a detection target is detected based on at least one of the first light receiving signal S1 and the second light receiving signal S2 (i.e., the amount of light received by at least one of the first light receiving element 41A and the second light receiving element 41B). In this case, the spot diameter of the light incident on the light receiving surface may be within the light receiving surface or may extend beyond the light receiving surface.

[0023] On the other hand, in a distance setting reflective photoelectric sensor, the relative distance to the detection object based on a predetermined position P0 is detected based on the difference between the first light receiving signal S1 and the second light receiving signal S2. Specifically, this is as follows.

[0024] Fig. 3 is an explanatory diagram of a detection method using the principle of triangulation. As shown in Fig. 3, the photoelectric sensor further includes a light projecting lens 51 and a light receiving lens 52. Of the detection light irradiated from the light projecting element 3 to the object to be detected (indicated by the symbol T in Fig. 3) through the light projecting lens 51, the light reflected by the object to be detected and incident on the light receiving lens 52 is imaged on the light receiving surfaces of the first light receiving element 41A and the second light receiving element 41B.

[0025] The position of the light receiving lens 52 is adjusted so that the imaging position (light receiving position) when the object to be detected is at the predetermined position P0 coincides with the boundary line between the first light receiving element 41A and the second light receiving element 41B. In this case, it is preferable that the spot diameter of the light imaged on the light receiving surface is within the light receiving surface. However, if the difference between the amount of light received by the first light receiving element 41A and the amount of light received by the second light receiving element 41B changes depending on the relative position of the object to be detected, the spot diameter of the light imaged on the light receiving surface may extend beyond the light receiving surface.

[0026] According to this configuration, when the object to be detected approaches the photoelectric sensor, the imaging position (light receiving position) moves onto the light receiving surface of the first light receiving element 41A, and conversely, when the object to be detected moves away from the photoelectric sensor, the imaging position (light receiving position) moves onto the light receiving surface of the second light receiving element 41B, based on a predetermined position P0.

[0027] In such a detection method using the principle of triangulation, by deriving the difference between the first light receiving signal S1 and the second light receiving signal S2, the amplitude of the differential signal Sd (=S1-S2) obtained from this difference becomes a value close to zero when the object to be detected is at the specified position P0, becomes a positive value when the object to be detected approaches the photoelectric sensor, and becomes a negative value when the object to be detected moves away from the photoelectric sensor.

[0028] The subtraction circuit 42 is a circuit that derives the difference between the first light receiving signal S1 and the second light receiving signal S2 described above, and outputs a difference signal Sd (=S1-S2) obtained from the difference.

[0029] The switching circuit 43 has a first input terminal 43A, a second input terminal 43B, and an output terminal 43C, and is a circuit capable of switching between a setting in which a signal input to the first input terminal 43A is output from the output terminal 43C (hereinafter referred to as a "first setting") and a setting in which a signal input to the second input terminal 43B is output from the output terminal 43C (hereinafter referred to as a "second setting"). In this embodiment, a first light receiving signal S1 is input to the first input terminal 43A, and a difference signal Sd is input to the second input terminal 43B. That is, in the first setting, a signal (a signal indicating the amount of light received by the light receiving unit 41, here the first light receiving signal S1) required for a transmission type, a reflection type, and a mirror reflection type photoelectric sensor is output from the output terminal 43C, and in the second setting, a difference signal Sd required for a distance setting reflection type photoelectric sensor is output from the output terminal 43C. The second light reception signal S2 may be input to the first input terminal 43A.

[0030] The setting of the switching circuit 43 is switched by the control unit 49 in response to a switching signal Sw input from the outside. That is, when the photoelectric sensor is used as any one of a transmission type, a reflection type, and a mirror reflection type photoelectric sensor, the setting of the switching circuit 43 is switched to the first setting by the switching signal Sw. On the other hand, when the photoelectric sensor is used as a distance setting reflection type photoelectric sensor, the setting of the switching circuit 43 is switched to the second setting by the switching signal Sw.

[0031] The amplifier circuit 44 is provided on the output side of the switching circuit 43, and is a circuit that amplifies the output signal Sr from the switching circuit 43. By performing amplification on the output side of the switching circuit 43 in this manner, only one amplification circuit is required for the photoelectric sensor IC 4, and therefore the circuit can be simplified compared to the case where amplification is performed on the input side of the switching circuit 43 (i.e., the case where two amplifier circuits are required).

[0032] The integration circuit 45 is a circuit that integrates the amplitude of the output signal Sr amplified by the amplifier circuit 44 with respect to time. In this embodiment, the detection light is a pulsed light repeatedly emitted from the light projecting element 3 at a predetermined period under the control of the control unit 49, and the pulsed light may be composed of one pulse per period (see FIG. 4(A)), or may be composed of a plurality of pulses in one cluster (for example, composed of four pulses, see FIG. 4(B)). In this way, by using a plurality of pulsed lights in one cluster as the detection light and obtaining an integral value per period in the integration circuit 45, it is possible to obtain a detection result for each period with high accuracy. In addition, by combining a bandpass filter (not shown), it is possible to reduce light other than the frequency band contained in the plurality of pulsed lights (for example, the influence of an external modulated light source).

[0033] The comparison circuit 46 is a circuit that compares the integral value Qr obtained by the integration circuit 45 with a reference value Q0. Here, the reference value Q0 may be changed according to the setting of the switching circuit 43 (i.e., according to a switching signal Sw input from the outside).

[0034] Then, the control unit 49 determines the detection state of the detectable object based on the comparison result in the comparison circuit 46. Specifically, when the switching circuit 43 is used in the first setting, the control unit 49 determines whether or not the detectable object has been detected (i.e., the presence or absence of the detectable object) based on the comparison result in the comparison circuit 46. When the switching circuit 43 is used in the second setting, the control unit 49 detects the relative distance to the detectable object based on the predetermined position P0 based on the comparison result in the comparison circuit 46.

[0035] More specifically, when the switching circuit 43 is used in the first setting, if the comparison circuit 46 determines that the integral value Qr is greater than the reference value Q0, the control unit 49 determines that a detectable object has been detected. This type of control is a control for detecting a detectable object when the integral value Qr becomes large (i.e., when the amount of light received by the light receiving unit 41 becomes large), and is called light-on control. In contrast, a control for detecting a detectable object when the integral value Qr becomes small (i.e., when the amount of light received by the light receiving unit 41 becomes small) is called dark-on control, and the control unit 49 may determine the presence or absence of a detectable object by dark-on control when the switching circuit 43 is used in the first setting. In addition, the photoelectric sensor of this embodiment may be one in which the light-on control and the dark-on control can be switched by operating a knob provided on the case 1, for example.

[0036] On the other hand, when the switching circuit 43 is used in the second setting, if the comparison circuit 46 determines that "the integrated value Qr is greater than the reference value Q0," the control unit 49 detects an object to be detected and determines that the position of the object to be detected is closer to the photoelectric sensor than the predetermined position P0. Note that even when the switching circuit 43 is used in the second setting, switching between light-on control and dark-on control may be performed by operating a knob provided on the case 1, as in the case when the switching circuit 43 is used in the first setting.

[0037] According to such a photoelectric sensor IC4, a circuit according to the type of photoelectric sensor can be constructed by simply switching the setting of the switching circuit 43. That is, when the photoelectric sensor IC4 is mounted on at least one of the transmission type, reflection type, and mirror reflection type photoelectric sensors, a circuit for detecting the presence or absence of a detection target can be constructed by switching the setting of the switching circuit 43 in the photoelectric sensor IC4 to the first setting (a setting in which a signal inputted to the first input terminal 43A is outputted from the output terminal 43C) in the photoelectric sensor IC4. On the other hand, when the photoelectric sensor IC4 is mounted on a distance setting reflection type photoelectric sensor, a circuit for detecting the relative distance to the detection target based on a predetermined position P0 (see FIG. 3) can be constructed by switching the setting of the switching circuit 43 in the photoelectric sensor IC4 to the second setting (a setting in which a signal inputted to the second input terminal 43B is outputted from the output terminal 43C) in the photoelectric sensor IC4. Thus, according to the photoelectric sensor IC4, it can be used in common with at least one of the transmission type, reflection type, and mirror reflection type photoelectric sensors and with the distance setting reflection type photoelectric sensor.

[0038] [2] Variations [2-1] First modified example Fig. 5 is a conceptual diagram showing the configuration of a photoelectric sensor IC4 according to a first modified example. As shown in Fig. 5, the photoelectric sensor IC4 may further include an adder circuit 47. Here, the adder circuit 47 is a circuit that derives a synthesis of the first light receiving signal S1 and the second light receiving signal S2, and outputs a synthesis signal Se (=S1+S2) obtained by the synthesis. The synthesis signal Se may be input to the first input terminal 43A.

[0039] According to this configuration, when the switching circuit 43 is set to the first setting, both of the lights incident on the first light receiving element 41A and the second light receiving element 41B are used to determine whether or not a detectable object is present. On the other hand, when only one of the first light receiving signal S1 and the second light receiving signal S2 is input to the first input terminal 43A, only the light incident on the first light receiving element 41A or the second light receiving element 41B connected to the first input terminal 43A is used to determine whether or not a detectable object is present. Therefore, according to the configuration of this modification, the light receiving area of ​​the light receiving section 41 can be increased.

[0040] [2-2] Second variant In the above-described photoelectric sensor IC 4, the control unit 49 may perform a process of comparing the integral value Qr obtained by the integration circuit 45 with a reference value Q0, instead of the comparison circuit 46. In this case, the control unit 49 uses the integral value Qr obtained by the integration circuit 45 to determine the detection state of the object to be detected.

[0041] [2-3] Third variant In the above-described photoelectric sensor IC 4, the reference value Q0 may be set to a negative value by the comparison circuit 46. Then, when the switching circuit 43 is used in the second setting, if the comparison circuit 46 determines that "the integrated value Qr is smaller than the reference value Q0", the control unit 49 may detect an object to be detected and determine that the position of the object to be detected is farther from the photoelectric sensor than the predetermined position P0.

[0042] In addition, two types of reference values ​​Q0, a positive value and a negative value, may be prepared in the comparison circuit 46, and the control unit 49 may determine, based on the comparison result in the comparison circuit 46 in this case, whether the position of the object to be detected is closer to the photoelectric sensor than the predetermined position P0, or is farther from the photoelectric sensor than the predetermined position P0.

[0043] The above-mentioned description of the embodiment should be considered as illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims, not by the above-mentioned embodiment. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0044] 1 case 2. Board 3 Light emitting element 4 Photoelectric sensor ICs 5. Code 11 Light-emitting / receiving window 41 Light receiving part 41A First light receiving element 41B Second light receiving element 42 Subtraction Circuit 43 Switching circuit 43A 1st input terminal 43B Second input terminal 43C Output terminal 44 Amplification circuit 45 Integrating circuit 46 Comparison circuit 47 Adding Circuit 49 Control Unit 51 Projection lens 52 Receiving lens P0 Predetermined position Q0 Reference Value Qr integral value S1 First light receiving signal S2 2nd light receiving signal Sd Differential signal Se composite signal Sr Output Signal Sw Switching signal

Claims

1. A photoelectric sensor IC that can be used in common with at least one of a transmission type, a reflection type, and a mirror reflection type photoelectric sensor that detects the presence or absence of a detection target, and a distance setting reflection type photoelectric sensor that detects a relative distance to a detection target based on a predetermined position, A first light receiving element and a second light receiving element, a subtraction circuit that outputs a difference signal that is a difference between a first light receiving signal that changes according to an amount of light received by the first light receiving element and a second light receiving signal that changes according to an amount of light received by the second light receiving element; a switching circuit having a first input terminal to which at least one of the first light receiving signal and the second light receiving signal is input, a second input terminal to which the differential signal is input, and an output terminal, and capable of switching between a setting in which a signal input to the first input terminal is output from the output terminal when the IC is used for at least one of the transmission type, the reflection type, and the mirror reflection type photoelectric sensor, and a setting in which a signal input to the second input terminal is output from the output terminal when the IC is used for the distance setting reflection type photoelectric sensor; a control unit that switches the setting of the switching circuit in response to a switching signal input from outside the IC in order to switch between using the IC for at least one of the transmission type, the reflection type, and the mirror reflection type photoelectric sensor and using the IC for the distance setting reflection type photoelectric sensor; An IC for a photoelectric sensor comprising:

2. an adder circuit that outputs a composite signal that is a composite of the first light receiving signal and the second light receiving signal; 2. The photoelectric sensor IC according to claim 1, wherein the composite signal is input to the first input terminal.

3. An amplifier circuit for amplifying an output signal from the switching circuit is further provided, The photoelectric sensor IC according to claim 1 , wherein the control unit determines a detection state of the object to be detected by using the output signal amplified by the amplifier circuit.

4. an integration circuit that integrates the amplitude of the output signal amplified by the amplifier circuit with respect to time; a comparison circuit for comparing the integral value obtained by the integration circuit with a reference value; Further comprising: The photoelectric sensor IC according to claim 3 , wherein the control unit determines a detection state of the object to be detected based on a comparison result in the comparison circuit.

5. A photoelectric sensor comprising the photoelectric sensor IC according to any one of claims 1 to 4.

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