Photoelectric sensor ICs and photoelectric sensors

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 a photoelectric sensor IC and a photoelectric sensor including the same. [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 an object to be detected 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 so that the light receiving position of the light receiving element changes from a reference point (the light receiving position when the object to be detected is at a predetermined position) depending on the relative distance to the object to be detected based on a predetermined position, and detect the relative distance to the object to be detected based on the light receiving position (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-014360 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-226851 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 an object to be detected or the relative distance to the object to be detected, and therefore the integrated circuit (ASIC) has also been forced to be designed according to the type of photoelectric sensor.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention 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 can be used in common with at least one of a transmission-type, reflection-type, and mirror-reflection-type photoelectric sensor that detects the presence or absence of a detectable object, and a distance-setting reflection-type photoelectric sensor that detects the relative distance to a detectable object based on a predetermined position, and includes a first light-receiving element, a second light-receiving element, a subtraction circuit, a switching circuit, and a control unit. Here, the subtraction circuit outputs a differential signal that is the difference between a first light-receiving signal that changes in accordance with the amount of light received by the first light-receiving element and a second light-receiving signal that changes in accordance with 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 switchable between a setting to output 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 to output 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] With the photoelectric sensor IC, a circuit suitable for the type of photoelectric sensor can be constructed simply by switching the setting of the switching circuit. That is, when the photoelectric sensor IC is installed in at least one of a transmissive, reflective, and mirror-reflective photoelectric sensor, a circuit for detecting the presence or absence of a detectable 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 the first input terminal is output from the output terminal. On the other hand, when the photoelectric sensor IC is installed in a distance-setting reflective photoelectric sensor, a circuit for detecting the relative distance to a detectable 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 the second input terminal is output from the 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 and second light receiving signals. The composite signal may be input to the first input terminal. With this configuration, when the switching circuit is set to output a signal input to the first input terminal from the output terminal, both light incident on the first and second light receiving elements are used to determine whether or not a detectable object is present. On the other hand, when only one of the first and second light receiving signals is input to the first input terminal, only light incident on the first or second light receiving element connected to the first input terminal is used to determine whether or not a detectable object is present. Therefore, the above configuration allows for a larger light receiving area.

[0009] The photoelectric sensor IC may further include an amplifier circuit that amplifies the output signal from the switching circuit. The control unit may then 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, thereby simplifying the circuitry compared to when amplification is performed on the input side of the switching circuit (i.e., when two amplifier circuits are required).

[0010] The photoelectric sensor IC may further include an integration circuit that integrates the amplitude of the output signal amplified by the amplifier circuit over time, and a comparison circuit that compares the integration value obtained by the integration 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 comparison circuit. With this configuration, the integration circuit calculates the integration value per cycle, thereby enabling accurate detection results for each cycle to be obtained. This improves 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 if 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 in which a signal input to the first input terminal is output from the output terminal, and if 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 in which a signal input to the second input terminal is output from the output terminal. [Effects of the Invention]

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

[0013] [Figure 1] 1 is a cutaway perspective view conceptually showing a photoelectric sensor according to an embodiment; [Figure 2] 1 is a conceptual diagram showing the configuration of a photoelectric sensor IC according to an embodiment of the present invention. [Figure 3] FIG. 10 is an explanatory diagram of a detection method using the principle of triangulation. [Figure 4] 1A and 1B are conceptual diagrams showing two examples of pulsed light used as light for detection. [Figure 5] FIG. 10 is a conceptual diagram showing the configuration of a photoelectric sensor IC according to a first modified example. DETAILED DESCRIPTION OF THE INVENTION

[0014] [1] Implementation [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-emitting 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, such as an LED or a semiconductor laser, that emits light (detection light) for detecting a detectable object. The photoelectric sensor IC 4 has a light-receiving unit 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 light emitted by the light-projecting element 3 passes through the light-projecting / receiving window 11, and that part of the light reflected by the detectable object or the reflector passes through the light-projecting / receiving window 11 again to enter the light-receiving unit 41.

[0016] As described above, the photoelectric sensor of this embodiment is a photoelectric sensor that emits detection light from its own light-emitting element 3, and is a reflective or mirror-reflection photoelectric sensor that detects the presence or absence of a detectable object, or a distance-setting reflective photoelectric sensor that detects the relative distance to the detectable object with reference to 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-emitting element 3, but detects light emitted by a light-emitting device provided separately from the photoelectric sensor with the light-receiving unit 41.

[0017] Conventionally, the circuit configuration for making a 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 an object to be detected or the relative distance to the object to be detected, and the photoelectric sensor IC 4 has also been forced to be designed according to the type of photoelectric sensor.

[0018] Therefore, in this embodiment, the photoelectric sensor IC 4 is configured so that it can be used in common with at least one of a transmission type, a reflection type, and a mirror reflection type photoelectric sensor and a 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 2 is a conceptual diagram showing the configuration of a 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. The photoelectric sensor IC 4 further 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 formed of, for example, a photodiode, and converts light incident on its light receiving surface into an electrical signal and outputs the electrical signal, thereby outputting a first light receiving signal S1 that varies depending on the amount of light received at that time. Similarly, the second light receiving element 41B is formed of, for example, a photodiode, and converts light incident on its light receiving surface into an electrical signal and outputs a second light receiving signal S2 that varies depending on 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 from the light emitting element 3. The first light receiving signal S1 and the second light receiving signal S2 output by these elements 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 an object to be detected 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 object to be detected 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) via 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 diameter of the light spot imaged on the light-receiving surface is within the light-receiving surface. However, the diameter of the light spot imaged on the light-receiving surface may extend beyond the light-receiving surface, as long as 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.

[0026] With 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, based on a predetermined position P0, 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.

[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 predetermined 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 received light signal S1 and the second received light signal S2, and outputs a differential 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 that can switch between a setting (hereinafter referred to as the "first setting") in which a signal input to the first input terminal 43A is output from the output terminal 43C, and a setting (hereinafter referred to as the "second setting") in which a signal input to the second input terminal 43B is output from the output terminal 43C. In this embodiment, a first received light 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 received light signal S1) required for a transmission-type, reflection-type, or 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 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 amplifies the output signal Sr from the switching circuit 43. By performing amplification on the output side of the switching circuit 43 in this way, only one amplifier circuit is required for the photoelectric sensor IC 4, and therefore the circuit can be simplified compared to when amplification is performed on the input side of the switching circuit 43 (i.e., when 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 over time. In this embodiment, the detection light is pulsed light repeatedly emitted from the light-projecting element 3 at a predetermined period under the control of the control unit 49. The pulsed light may be composed of one pulse per period (see FIG. 4A) or may be composed of multiple pulses grouped together (e.g., four pulses, see FIG. 4B). In this way, by using multiple pulsed lights grouped together as the detection light and calculating the integral value per period in the integration circuit 45, it is possible to obtain accurate detection results for each period. Furthermore, by combining a band-pass filter (not shown), it is possible to reduce light outside the frequency band included in the multiple pulsed lights (e.g., the influence of an external modulated light source).

[0033] The comparison circuit 46 is a circuit that compares the integrated 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 of 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., whether or not the detectable object is present) based on the comparison result of 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 of 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 integrated 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, which detects a detectable object when the integrated value Qr increases (i.e., when the amount of light received by the light-receiving unit 41 increases), is called light-on control. In contrast, control, which detects a detectable object when the integrated value Qr decreases (i.e., when the amount of light received by the light-receiving unit 41 decreases), is called dark-on control. When the switching circuit 43 is used in the first setting, the control unit 49 may determine the presence or absence of a detectable object using dark-on control. Furthermore, the photoelectric sensor of this embodiment may be capable of switching between light-on control and dark-on control 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 the 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 where the switching circuit 43 is used in the first setting.

[0037] With this photoelectric sensor IC4, a circuit suitable for the type of photoelectric sensor can be configured simply by switching the setting of the switching circuit 43. That is, when the photoelectric sensor IC4 is installed in at least one of a transmission-type, reflection-type, and mirror-reflection-type photoelectric sensor, a circuit for detecting the presence or absence of a detection target can be configured by switching the setting of the switching circuit 43 in the photoelectric sensor IC4 to the first setting (a setting in which a signal input to the first input terminal 43A is output from the output terminal 43C). On the other hand, when the photoelectric sensor IC4 is installed in 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 configured by switching the setting of the switching circuit 43 in the photoelectric sensor IC4 to the second setting (a setting in which a signal input to the second input terminal 43B is output from the output terminal 43C). Therefore, the photoelectric sensor IC4 can be used in common with at least one of a transmission-type, reflection-type, and mirror-reflection-type photoelectric sensor and a distance-setting reflection-type photoelectric sensor.

[0038] [2] Variation [2-1] First modified example Fig. 5 is a conceptual diagram showing the configuration of a photoelectric sensor IC4 according to a first modification. 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 combination of the first light receiving signal S1 and the second light receiving signal S2, and outputs a combined signal Se (=S1+S2) obtained by the combination. The combined signal Se may be input to a first input terminal 43A.

[0039] According to this configuration, when the switching circuit 43 is set to the first setting, both the light incident on the first light receiving element 41A and the second light receiving element 41B are used to determine the presence or absence of a detectable object. 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 the presence or absence of a detectable object. Therefore, according to the configuration of this modified example, the light receiving area of ​​the light receiving unit 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 photoelectric sensor IC 4 described above, the reference value Q0 may be set to a negative value by the comparison circuit 46. When the switching circuit 43 is used in the second setting and 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] Alternatively, the comparison circuit 46 may provide two types of reference value Q0, a positive value and a negative value, and the control unit 49 may determine, based on the comparison result of 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 whether the position is farther from the photoelectric sensor than the predetermined position P0.

[0043] The above-described embodiments should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined not by the above-described embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications that are equivalent to the scope of the claims and fall within the scope thereof. [Explanation of symbols]

[0044] 1 case 2 boards 3 Light-emitting element 4 Photoelectric sensor ICs 5. Code 11 Light-emitting and 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 standard 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 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 detection target, and a distance setting reflection type photoelectric sensor that detects the 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 differential signal that is the difference between a first light receiving signal that varies in accordance with the amount of light received by the first light receiving element and a second light receiving signal that varies in accordance with the 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 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 both the first light receiving signal and the second light receiving signal are input to the first input terminal as the composite signal via the adder circuit.

3. further comprising an amplifier circuit for amplifying an output signal from the switching circuit; 3. The photoelectric sensor IC according to claim 1, wherein the control unit determines a detection state of the object to be detected 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 over time; a comparison circuit that compares the integral value obtained by the integration circuit with a reference value; Further provided with 4. The photoelectric sensor IC according to claim 3, wherein the control unit determines the detection state of the object to be detected based on the comparison result of 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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