JP5408325B2 - Photoelectric sensor, photoelectric sensor light receiving unit and photoelectric sensor light projecting unit - Google Patents

Description

  The present invention relates to a photoelectric sensor, a photoelectric sensor light receiving unit, and a photoelectric sensor light projecting unit, and more particularly, a photoelectric sensor that detects an object by irradiating pulse light, a photoelectric sensor light receiving unit, and a photoelectric sensor light projecting unit. Related.

A photodiode or the like is generally used as the light receiving element of the photoelectric sensor, and a transimpedance amplifier is used as one means for extracting a signal output from the photodiode. In the transimpedance amplifier, two input terminals of the inverting amplifier are virtually short-circuited by a photodiode, and the output of the photodiode is directly input to the negative input terminal of the inverting amplifier. Since this transimpedance amplifier has a wide dynamic range and very little noise when no light is incident, it can extract a signal with a high S / N ratio (Signal to Noise Ration). In addition, a signal with good linearity can be extracted even from a weak light incident state. Therefore, the transimpedance amplifier is used for detecting DC light. However, the transimpedance amplifier has poor response characteristics from the non-incident light due to the capacitance component of the photodiode, and is not suitable for detecting pulsed light (see Non-Patent Document 1 and Patent Document 1).

  On the other hand, as shown in FIG. 17, a circuit in which a reverse bias voltage is applied to a photodiode (hereinafter referred to as a reverse bias type circuit) is used to improve response characteristics with respect to detection of pulsed light. Such a reverse bias circuit can sufficiently respond even if the optical signal is a pulse with a very short time width of about 1 μs. However, reverse-biased circuits are suitable for detecting DC light because of the relatively large noise when no light is incident due to photodiode shot noise due to reverse bias and thermal noise of current / voltage conversion elements. (See Non-Patent Document 1 and Patent Document 1).

Japanese Patent No. 3254532

"Optical sensor and how to use it (2nd edition)", author: Junji Tanikoshi, publisher: Nikkan Kogyo Shimbun, issue date (2nd edition): March 21, 2000

  By the way, it is convenient if a transimpedance amplifier usually used for detecting DC light can be used as a photoelectric sensor for detecting pulsed light. This is because, for example, a general-purpose photo IC for DC light detection in which a photodiode and a transimpedance amplifier are mounted on one chip is sold, and pulse light can be generated using such a general-purpose photo IC for DC light detection. This is because if a photoelectric sensor to be detected can be constructed, an inexpensive and small photoelectric sensor can be provided.

  Therefore, an object of the present invention is to provide a photoelectric sensor that can detect pulsed light using a circuit that outputs a current from a light receiving element to a voltage without applying a reverse bias voltage to the light receiving element, such as a transimpedance amplifier. It is to provide a sensor, a light receiving unit of a photoelectric sensor, and a light projecting unit of a photoelectric sensor.

In order to solve the above-described problems, the light receiving unit of the photoelectric sensor of the present invention includes a light receiving element that receives light that is incident from a detection region and is biased with pulsed light by DC light, and does not apply a reverse bias to the light receiving element. In addition, a conversion unit that converts the current output from the light receiving element into a voltage and a high-pass filter that removes a direct-current light component from the voltage output from the conversion unit are included, and the conversion unit is a transimpedance amplifier.

Preferably, the light receiving element and the conversion unit are integrated on one chip.
Preferably, the light receiving unit of the photoelectric sensor further includes a light projecting element that projects direct-current light directly toward the light receiving element.

  The present invention is also a light projecting unit of a photoelectric sensor that projects light onto the light receiving unit described above, the first light projecting element that projects pulsed light toward the detection region, and direct light reception. And a second light projecting element that projects toward the element.

  In addition, the present invention is a light projecting unit of a photoelectric sensor that projects light onto the above-described light receiving unit, and includes a light projecting element that projects light obtained by biasing pulsed light with DC light toward a detection region.

  In addition, the photoelectric sensor of the present invention includes a light receiving element that receives light that is incident from a detection region and that is pulsed light biased with DC light, and a current that is output from the light receiving element without applying a reverse bias to the light receiving element. A voltage conversion unit, a high-pass filter that removes a DC light component from the voltage output from the conversion unit, a first light projecting element that projects pulsed light toward a detection region, and DC light And a second light projecting element that projects light directly toward the light receiving element, and the conversion unit is a transimpedance amplifier.

  In addition, the photoelectric sensor of the present invention includes a light receiving element that receives light that is incident from a detection region and that is pulsed light biased with DC light, and a current that is output from the light receiving element without applying a reverse bias to the light receiving element. A voltage conversion unit, a high-pass filter that removes a DC light component from the voltage output from the conversion unit, and a light projecting element that projects light biased with DC light to a detection region. The conversion unit is a transimpedance amplifier.

  In addition, the light receiving unit of the photoelectric sensor of the present invention receives the light that is incident from the detection region and biases the pulsed light with DC light, and extracts the red component of the light, and receives the light. A second light receiving element that extracts a green component of light, a third light receiving element that receives light and extracts a blue component of light, and without applying a reverse bias to the first light receiving element. A first converter that converts a current output from the first light receiving element into a voltage, and a current output from the second light receiving element without applying a reverse bias to the second light receiving element. A second conversion unit for converting, a third conversion unit for converting a current output from the third light receiving element into a voltage without applying a reverse bias to the third light receiving element, and a first conversion unit; A first high-pass filter that removes a direct-current light component from the voltage output from the second converter and a second converter A first high-pass filter that removes a direct-current light component from the output voltage; and a third high-pass filter that removes a direct-current light component from the voltage output from the third converter. The second conversion unit and the third conversion unit are transimpedance amplifiers.

  Preferably, the first conversion unit, the second conversion unit, and the third conversion unit are transimpedance amplifiers.

  Preferably, the first light receiving element, the second light receiving element, the third light receiving element, the first conversion unit, the second conversion unit, and the third conversion unit are integrated on one chip.

  The photoelectric sensor light projecting unit of the present invention is a photoelectric sensor light projecting unit that projects light onto the aforementioned light receiving unit, and is a first light projecting device that projects white pulse light toward the detection region. An optical element, and a second light projecting element that projects white direct-current light directly toward the light receiving element.

  The photoelectric sensor light projecting unit of the present invention is a photoelectric sensor light projecting unit that projects light onto the aforementioned light receiving unit, and is a first light projecting device that projects white pulse light toward the detection region. An optical element; and a second light projecting element that projects infrared direct-current light directly toward the light receiving element.

  The photoelectric sensor light projecting unit of the present invention is a photoelectric sensor light projecting unit that projects light onto the light receiving unit described above, and directs white light biased with DC light to the detection region. A light projecting element for projecting light is provided.

  In addition, the light receiving unit of the photoelectric sensor of the present invention receives the light that is incident from the detection region and biases the pulsed light with DC light, and extracts the red component of the light, and receives the light. A second light receiving element that extracts a green component of light, a third light receiving element that receives light and extracts a blue component of light, and without applying a reverse bias to the first light receiving element. A first converter that converts a current output from the first light receiving element into a voltage, and a current output from the second light receiving element without applying a reverse bias to the second light receiving element. A second conversion unit for converting, a third conversion unit for converting a current output from the third light receiving element into a voltage without applying a reverse bias to the third light receiving element, and a first conversion unit; A first high-pass filter that removes a direct-current light component from the voltage output from the second converter and a second converter The second high-pass filter that removes the DC light component from the output voltage, the third high-pass filter that removes the DC light component from the voltage output from the third converter, and the white DC light directly A light projecting element that projects light toward the light receiving element, and the first conversion unit, the second conversion unit, and the third conversion unit are transimpedance amplifiers.

  In addition, the light receiving unit of the photoelectric sensor of the present invention receives the light that is incident from the detection region and biases the pulsed light with DC light, and extracts the red component of the light, and receives the light. A second light receiving element that extracts a green component of light, a third light receiving element that receives light and extracts a blue component of light, and without applying a reverse bias to the first light receiving element. A first converter that converts a current output from the first light receiving element into a voltage, and a current output from the second light receiving element without applying a reverse bias to the second light receiving element. A second conversion unit for converting, a third conversion unit for converting a current output from the third light receiving element into a voltage without applying a reverse bias to the third light receiving element, and a first conversion unit; A first high-pass filter that removes a direct-current light component from the voltage output from the second converter and a second converter A second high-pass filter that removes a DC light component from the output voltage; a third high-pass filter that removes a DC light component from the voltage output from the third converter; and an infrared DC light A light projecting element that projects light directly toward the light receiving element, and the first conversion unit, the second conversion unit, and the third conversion unit are transimpedance amplifiers.

  According to the present invention, it is possible to detect pulsed light using a circuit that outputs a current from a light receiving element to a voltage without applying a reverse bias voltage to the light receiving element.

It is a figure showing the structure of the photoelectric sensor of the 1st Embodiment of this invention. It is a figure showing the structure of the photodiode and transimpedance amplifier which are contained in general purpose photo IC. It is an external appearance perspective view of the photoelectric sensor of the 1st Embodiment of this invention. It is sectional drawing of the photoelectric sensor of FIG. It is a figure for demonstrating the outline of operation | movement of the conventional photoelectric sensor. It is a figure for demonstrating the outline of operation | movement of the photoelectric sensor of the 1st Embodiment of this invention. It is a figure showing the structure of the photoelectric sensor of the 2nd Embodiment of this invention. It is a figure for demonstrating the outline of operation | movement of the photoelectric sensor of the 2nd Embodiment of this invention. It is a figure showing the structure of the photoelectric sensor of the 3rd Embodiment of this invention. It is a figure which shows the relative sensitivity with respect to the wavelength of the light of a 1st light receiving element, a 2nd light receiving element, and a 3rd light receiving element. It is a figure showing the structure of the photoelectric sensor of the 4th Embodiment of this invention. It is a figure showing the structure of the photoelectric sensor of the 5th Embodiment of this invention. It is a figure showing the modification of the photoelectric sensor of FIG. It is a figure showing the modification of the photoelectric sensor of FIG. It is a figure showing the modification of the photoelectric sensor of FIG. It is an external appearance perspective view in the state where the upper cover of the fiber photoelectric sensor was opened. It is a figure showing the structure of a reverse bias type circuit.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings.
[First Embodiment]
The first embodiment relates to a photoelectric sensor provided with an LED that outputs DC light in addition to an LED (Light Emitting Diode) that outputs pulse light for target object detection.

  The photoelectric sensor emits light such as visible light and infrared rays as signal light from the light projecting unit toward the detection target region, and when a detection target exists in the detection target region, the light receiving unit receives reflected light from the detection target. To obtain an output signal indicating the feature quantity of the detection object.

  In general, the light projecting element used in the light projecting unit of the photoelectric sensor is pulse-driven. The purpose of this is to prevent so-called mutual interference so that light from other photoelectric sensors is not mistakenly detected when, for example, a plurality of photoelectric sensors of the same type are used side by side, in addition to measures against disturbance light such as sunlight. It may be used in.

FIG. 1 is a diagram illustrating a configuration of a photoelectric sensor according to a first embodiment of the present invention.
With reference to FIG. 1, the photoelectric sensor includes a light projecting unit 10 and a light receiving unit 50.

  The light projecting unit 10 includes an LED (A) 11, a drive unit (A) 12, a light projection lens 15, an LED (B) 13, and a drive unit (B) 14. The light receiving unit 50 includes a light receiving lens 51, a general-purpose photo IC 57, a high-pass filter 54, a signal processing unit 55, and a light projection control unit 56.

  The general-purpose photo IC 57 includes a photodiode 52 and a transimpedance amplifier 53. That is, the photodiode 52 and the transimpedance amplifier 53 are integrated on one chip.

LED (A) 11 is a first light projecting element and outputs pulsed light.
The drive unit (A) 12 drives the LED (A) 11 to output pulsed light.

The light projecting lens 15 irradiates the light output from the LED (A) 11 toward the detection region.
The LED (B) 13 is a second light projecting element and outputs direct-current light (DC bias light) directly to the photodiode 57.

  The drive unit (B) 14 drives the LED (B) 13 to output DC light (DC bias light).

  The light receiving lens 51 condenses the light from the detection region (including the pulsed light output from the LED (A) 11) and outputs it to the photodiode 52.

  The photodiode 52 is a light receiving element, receives light in which the light output from the light receiving lens 51 and the direct current light output from the LED (B) 13 are superimposed, and converts the light into an electrical signal.

  The transimpedance amplifier 53 converts the current output from the photodiode 52 into a voltage without applying a reverse bias voltage to the photodiode 52.

  FIG. 2 is a diagram illustrating the configuration of the photodiode 52 and the transimpedance amplifier 53 included in the general-purpose photo IC 57.

  Referring to FIG. 2, the two input terminals of the inverting operational amplifier OP of the transimpedance amplifier 53 are virtually short-circuited by the photodiode 52, and the output of the photodiode is directly input to the negative input terminal of the inverting operational amplifier OP. . A resistor RF and a capacitor C are feedback-connected in parallel between the output terminal and the input terminal of the inverting operational amplifier OP.

  Referring to FIG. 1 again, the high-pass filter 54 removes a DC bias component (low frequency component), that is, a component of DC light, from the signal output from the transimpedance amplifier 53.

The signal processing unit 55 determines whether or not the target object exists in the detection area according to the signal output from the high-pass filter 54 (that is, the signal using pulsed light). That is, the signal processing unit 55 instructs the projection unit 10 to output pulsed light through the projection control unit 56, and immediately after the designated timing, the magnitude of the signal output from the high-pass filter 54 is predetermined. When the threshold value is exceeded, it is determined that the target object exists in the detection area.

  The light projecting control unit 56 instructs the drive unit (A) 12 of the light projecting unit 10 to output pulsed light in accordance with an instruction from the signal processing unit 55.

(Photoelectric sensor structure)
The structure of each function described above will be described in the case where the light projecting unit 10 and the light receiving unit 50 are incorporated in a light receiving and receiving integrated photoelectric sensor (that is, a reflection regression photoelectric sensor) housed in a common housing. .

FIG. 3 is an external perspective view of the photoelectric sensor according to the first embodiment of the present invention.
4 is a cross-sectional view of the photoelectric sensor of FIG.

  Referring to FIGS. 3 and 4, the sensor main body is provided with a light receiving and projecting window 203 on the front surface of case 206. The window 203 is held by a protective member 202 so as not to drop off. An indicator lamp 205 is provided on the upper surface of the case 206 so that the detection result can be understood.

  The light projecting lens 15 is supported by a holder member 301 of the light projecting unit. The light receiving lens 51 is supported by a holder member 302 of the light receiving unit.

  The LED (A) 11 is arranged so that the light emitting portion is located at the focal position of the light projecting lens 15. A photodiode 52 is disposed at the focal position of the light receiving lens 51.

  The light shielding member 303 is provided to prevent the light output from the LED (A) 11 from being directly input to the photodiode 52. A general-purpose photo IC 57, a high-pass filter 54, a signal processing unit 55, and a light projection control unit 56 are mounted on the substrate 304.

  The LED (B) 13 is disposed at a position where the output light is directly input to the photodiode 52.

(Operation comparison)
Next, the operation of the conventional photoelectric sensor according to the first embodiment of the present invention is compared as a reflection type photoelectric sensor.

FIG. 5 is a diagram for explaining the outline of the operation of the conventional photoelectric sensor.
Referring to FIG. 5, the LED outputs a pulsed light having a period T = 10 to 100 μs, a width of 2 to 3 μs, and a size A. This pulsed light is reflected by the detection object and has a size of A ′. Attenuates.

  The photodiode receives the pulsed light output from the LED and reflected by the detection object, converts it into an electrical signal, and sends it to the transimpedance amplifier.

  Since the transimpedance amplifier has poor responsiveness to pulsed light having no DC component, it cannot appropriately amplify the signal output from the photodiode.

  FIG. 6 is a diagram for explaining the outline of the operation of the photoelectric sensor according to the first embodiment of the present invention.

  Referring to FIG. 6, LED (A) outputs a pulsed light having a period T = 10 to 100 μs, a width of 2 to 3 μs, and a size A. This pulsed light is reflected by a detection object and has a size of Decays to A '. The LED (B) outputs DC light having a size B. The pulsed light output from the LED (A) and the direct-current light output from the LED (B) are sent to the photodiode of the light receiving unit through different paths.

  The photodiode is light in which the pulsed light output from the LED (A) and reflected by the detection object and the direct current light output from the LED (B) are superimposed, that is, light obtained by biasing the pulsed light with direct current light. Is received, converted into an electrical signal, and sent to a transimpedance amplifier.

  The transimpedance amplifier has good responsiveness since the input light has a DC component, and can appropriately amplify the signal output from the photodiode.

  Thereafter, the high-pass filter removes a DC component, that is, a direct-current light component, from the signal output from the transimpedance amplifier.

  As described above, according to the photoelectric sensor of the first embodiment, the pulsed light and the direct current light are simultaneously received and amplified, and then the direct current light is removed by the high-pass filter. Therefore, a reverse bias voltage is applied to the photodiode. The pulse light can be detected by using a transimpedance amplifier that converts the current from the photodiode into a voltage. In addition, according to the first embodiment, pulse light can be detected using a general-purpose photo IC designed to detect DC light, so that an inexpensive and small photoelectric sensor can be provided.

[Second Embodiment]
The second embodiment is a modification of the light projecting unit of the first embodiment, and instead of having two LEDs, a photoelectric device having a single LED that projects light biased with DC light from pulsed light. It relates to sensors.

FIG. 7 is a diagram illustrating the configuration of the photoelectric sensor according to the second embodiment of the present invention.
Referring to FIG. 7, this photoelectric sensor is different from the photoelectric sensor of FIG.

The light projecting unit 20 includes an LED 21, a drive unit 22, and a light projecting lens 15.
The LED 21 outputs light in which DC light is biased to pulsed light.

The drive unit 22 drives the LED 21.
The light projecting lens 15 irradiates the light output from the LED 21 toward the detection region.

(Operation)
Next, the operation of the case where the photoelectric sensor of the second embodiment of the present invention is used as a reflective photoelectric sensor will be described.

  FIG. 8 is a diagram for explaining the outline of the operation of the photoelectric sensor according to the second embodiment of the present invention.

Referring to FIG. 8, the LED outputs light in which DC light of magnitude B is biased to pulse light of period T = 10 to 100 μs, width 2 to 3 μs, and magnitude A. This light is reflected by the detection object, the magnitude of the pulse component is attenuated to A ′, and the magnitude of the direct current component is reduced to B ′. That is, in the second embodiment, unlike the first embodiment, pulsed light and DC light are sent to the photodiode of the light receiving unit through the same path.

  The photodiode receives light output from the LED and reflected by the detection object, that is, light obtained by biasing pulsed light with DC light, converts the light into an electric signal, and sends the electric signal to the transimpedance amplifier.

  The transimpedance amplifier has good responsiveness since the input light has a DC component, and can appropriately amplify the signal output from the photodiode.

  Thereafter, the high-pass filter removes a DC component from the signal output from the transimpedance amplifier.

  As described above, according to the photoelectric sensor of the second embodiment, similarly to the first embodiment, a transimpedance amplifier that converts a current from a photodiode into a voltage without applying a reverse bias voltage to the photodiode. Can be used to detect pulsed light. In addition, according to the second embodiment, as in the first embodiment, pulse light can be detected using a general-purpose photo IC designed to receive direct-current light, so that an inexpensive and small photoelectric sensor can be used. Can be provided.

[Third Embodiment]
In the third embodiment, in order to identify the color of the target object, white light is projected on the light projecting unit side, and the color of light received using the light receiving element for each color component is identified on the light receiving unit side. It relates to such a photoelectric sensor.

FIG. 9 is a diagram illustrating a configuration of a photoelectric sensor according to the third embodiment of the present invention.
Referring to FIG. 9, the photoelectric sensor includes a light projecting unit 30 and a light receiving unit 60.

  The light projecting unit 30 includes an LED (A) 31, a drive unit (A) 12, a light projection lens 15, an LED (B) 33, and a drive unit (B) 14.

  The light receiving unit 60 includes a light receiving lens 51, a general-purpose photo IC 77, a high-pass filter (A) 73, a high-pass filter (B) 74, a high-pass filter (C) 75, a signal processing unit 76, and a light projection control unit 56.

  The general-purpose photo IC 77 includes a first light receiving element 61 including a red component filter 62 and a photodiode (A) 63, a second light receiving element 64 including a green component filter 65 and a photodiode (B) 66, and a blue component filter 68. A third light receiving element 67 including a photodiode (C) 69, a transimpedance amplifier (A) 70, a transimpedance amplifier (B) 71, and a transimpedance amplifier (C) 72 are included. . In other words, the first light receiving element 61, the second light receiving element 64, the third light receiving element 67, the transimpedance amplifier (A) 70, the transimpedance amplifier (B) 71, and the transimpedance amplifier (C) 72 are one chip. It is collected in.

  The LED (A) 31 is a first light projecting element and outputs white (that is, including red, blue, and green components) pulsed light.

The drive unit (A) 12 drives the LED (A) 31 to output pulsed light.
The light projecting lens 15 irradiates the light output from the LED (A) 31 toward the detection region.

  The LED (B) 33 is a second light projecting element, and directs white (that is, including red, blue, and green components) DC light (DC bias light) directly to the first light receiving element 61 and the second light receiving element 61. The light is output toward the light receiving element 64 and the third light receiving element 67.

  The drive unit (B) 14 drives the LED (B) 33 to output DC light (DC bias light).

  The light receiving lens 51 receives light from the detection region (including pulse light output from the LED (A) 31), and receives the first light receiving element 61, the second light receiving element 64, and the third light receiving element 67. Output to.

  The red component filter 62 passes only the red component of the light in which the light output from the light receiving lens 51 and the DC light output from the LED (B) 33 are superimposed.

  The photodiode (A) 63 receives the red component light output from the red component filter 62 and converts it into an electrical signal.

  The green component filter 65 passes only the green component of the light in which the light output from the light receiving lens 51 and the DC light output from the LED (B) 33 are superimposed.

  The photodiode (B) 66 receives the green component light output from the green component filter 65 and converts it into an electrical signal.

  The blue component filter 69 passes only the blue component of the light in which the light output from the light receiving lens 51 and the DC light output from the LED (B) 33 are superimposed.

  The photodiode (C) 69 receives the blue component light output from the blue component filter 69 and converts it into an electrical signal.

  FIG. 10 is a diagram showing the relative sensitivity of the first light receiving element 61, the second light receiving element 64, and the third light receiving element 67 with respect to the wavelength of light.

  Referring to FIG. 10, the relative sensitivity S1 of the first light receiving element 61 including the red component filter 62 increases with red light, that is, light with a wavelength of 620 nm to 780 nm. The relative sensitivity S2 of the second light receiving element 64 including the green component filter 65 increases with green light, that is, light with a wavelength of 490 nm to 580 nm. The relative sensitivity S3 of the third light receiving element 67 including the blue component filter 69 is increased by blue light, that is, light having a wavelength of 450 nm to 490 nm. Therefore, red light can be detected by the first light receiving element 61, green light can be detected by the second light receiving element 64, and blue light can be detected by the third light receiving element 67.

  Referring to FIG. 9 again, transimpedance amplifier (A) 70 amplifies the signal output from photodiode (A) 63.

  The transimpedance amplifier (B) 71 amplifies the signal output from the photodiode (B) 66.

  The transimpedance amplifier (C) 72 amplifies the signal output from the photodiode (C) 69.

The high pass filter (A) 73 removes a DC bias component (low frequency component), that is, a component of DC light, from the signal output from the transimpedance amplifier (A) 70.

  The high pass filter (B) 74 removes a DC bias component (low frequency component), that is, a component of direct current light, from the signal output from the transimpedance amplifier (B) 71.

  The high pass filter (C) 75 removes a DC bias component (low frequency component), that is, a component of direct current light, from the signal output from the transimpedance amplifier (C) 72.

  The signal processing unit 76 determines whether or not there is a target object in the detection region and its color according to the signals output from the high-pass filter (A) 73, the high-pass filter (B) 74, and the high-pass filter (C) 75. . That is, the signal processing unit 76 instructs the projection unit 30 to output pulsed light through the projection control unit 56, and immediately after the designated timing, the high-pass filter (A) 73, the high-pass filter (B) 74, and The magnitude of the signal output from the high pass filter (C) 75 is examined. When the signal output from the high-pass filter (A) 73 exceeds a predetermined threshold, the signal processing unit 76 determines that the target object exists in the detection region, and determines that the target object includes a red component. Further, when the signal output from the high pass filter (B) 74 exceeds a predetermined threshold, the signal processing unit 76 determines that the target object exists in the detection region, and determines that the target object includes a green component. In addition, when the signal output from the high-pass filter (C) 75 exceeds a predetermined threshold, the signal processing unit 76 determines that the target object exists in the detection region, and determines that the target object includes a blue component.

  The light projection control unit 56 instructs the drive unit (A) of the light receiving unit to output pulsed light in accordance with an instruction from the signal processing unit.

  As described above, according to the photoelectric sensor of the third embodiment, the red component and the blue component are obtained by using the transimpedance amplifier that converts the current from the photodiode into the voltage without applying the reverse bias voltage to the photodiode. In addition, the pulse light of the green component can be detected. Further, according to the third embodiment, the pulse of the red component, the blue component, and the green component is used by using the general-purpose photo IC that can detect three colors of red, blue, and green designed for correcting the chromaticity of the display. Since light can be detected, an inexpensive and small photoelectric sensor can be provided.

[Fourth Embodiment]
The fourth embodiment is a modification of the light projecting unit of the third embodiment, and relates to a photoelectric sensor including a single LED that projects white light in which DC light is biased to pulse light.

FIG. 11 is a diagram illustrating a configuration of a photoelectric sensor according to the fourth embodiment of the present invention.
Referring to FIG. 11, this photoelectric sensor is different from the photoelectric sensor of FIG.

The light projecting unit 40 includes an LED 41, a drive unit 22, and a light projecting lens 15.
The LED 41 is biased with DC light to pulsed light and outputs white light (that is, including red, blue, and green components).

The drive unit 22 drives the LED 41.
The light projecting lens 15 irradiates the light output from the LED 41 toward the detection region.

As described above, according to the photoelectric sensor of the fourth embodiment, similarly to the third embodiment, the transimpedance amplifier that converts the current from the photodiode into the voltage without applying the reverse bias voltage to the photodiode. Can be used to detect pulsed light of the red, blue and green components. In addition, according to the fourth embodiment, as in the third embodiment, a general-purpose photo IC that can detect three colors of red, blue, and green designed for correcting the chromaticity of a display is used. Since pulse light of the component, the blue component and the green component can be detected, an inexpensive and small photoelectric sensor can be provided.

[Fifth Embodiment]
The fifth embodiment is a modification of the light projecting unit of the third embodiment, and relates to a photoelectric sensor provided with an LED that outputs infrared DC light instead of an LED that outputs white DC light.

  As shown in FIG. 10, each of the first light receiving element, the second light receiving element, and the third light receiving element has high relative sensitivity to infrared light (light having a wavelength of 780 nm to 1 mm). Therefore, bias light can be applied to these light receiving elements by applying infrared light instead of white light as DC light.

FIG. 12 is a diagram illustrating the structure of a photoelectric sensor according to the fifth embodiment of the present invention.
Referring to FIG. 12, this photoelectric sensor is different from the photoelectric sensor of FIG.

  The light projecting unit 70 includes an LED (A) 31, a drive unit (A) 12, a light projection lens 15, an LED (B) 73, and a drive unit (B) 14.

  Similar to the third embodiment, the LED (A) 31 outputs white (that is, including red, blue, and green components) pulsed light.

  The drive unit (A) 12 drives the LED (A) 31 to output pulsed light, as in the third embodiment.

  As in the third embodiment, the light projecting lens 15 irradiates the light output from the LED (A) 31 toward the detection region.

  The LED (B) 73 outputs infrared direct-current light (DC bias light) directly to the first light receiving element 61, the second light receiving element 64, and the third light receiving element 67.

  The drive unit (B) 14 drives the LED (B) 73 to output infrared DC light (DC bias light).

  As described above, according to the photoelectric sensor of the fifth embodiment, similarly to the third embodiment, the transimpedance amplifier that converts the current from the photodiode into the voltage without applying the reverse bias voltage to the photodiode. Can be used to detect pulsed light of the red, blue and green components. In addition, according to the fifth embodiment, as in the third embodiment, a general-purpose photo IC that can detect three colors of red, blue, and green designed for correcting the chromaticity of a display is used. Since pulse light of the component, the blue component and the green component can be detected, an inexpensive and small photoelectric sensor can be provided. Furthermore, according to the fifth embodiment, instead of the LED that outputs white DC light as in the third embodiment, an LED that outputs inexpensive infrared DC light is used. A photoelectric sensor that is less expensive than the embodiment can be provided.

(Modification)
The present invention is not limited to the above-described embodiment, and includes, for example, the following modifications.

(1) LED (B)
In the embodiment of the present invention, the LED (B) and the drive unit (B) for driving the LED (B) are provided on the light projecting unit side. However, the present invention is not limited to this, and may be provided on the light receiving unit side. For example, the present invention is the photoelectric sensor of FIG. 13 modified from the photoelectric sensor of FIG. 1, the photoelectric sensor of FIG. 14 modified of the photoelectric sensor of FIG. 9, and the photoelectric sensor of FIG. 15 modified of the photoelectric sensor of FIG. Also good.

(2) Structure of Photoelectric Sensor In the embodiment of the present invention, the light projecting unit and the light receiving unit are described as an example of a light receiving and receiving integrated photoelectric sensor accommodated in a common housing. However, the present invention is not limited to this. . The configuration described in the embodiment of the present invention can also be applied to a photoelectric sensor in which a light projecting unit and a light receiving unit are housed in separate housings.

  The configuration described in the embodiment of the present invention can also be applied to a fiber-type photoelectric sensor as shown in FIG.

FIG. 16 is an external perspective view of the fiber photoelectric sensor with the upper cover opened.
As shown in the figure, the photoelectric sensor has a multi-package plastic casing 101. The light projecting fiber 2 and the light receiving fiber 3 are inserted into the front portion of the housing 101 and are fixed to be detached by operating the clamp lever 103. The electric cord 4 is drawn out from the rear part of the casing 101. The illustrated electrical cord 4 includes a grounding core wire 141, a positive power source core wire 142, a detection output core wire 143, and a diagnostic output core wire 144. The casing 101 is fixed to a mounting surface such as a control panel via a DIN rail (not shown). What is indicated by reference numeral 104 is a DIN rail fitting groove. A transparent upper cover 102 is attached to the top of the housing 101 so as to be openable and closable. On the upper surface of the casing 101 exposed with the upper cover 102 opened, a first display 105, a second display 106, a first operation button 107, a second operation button 108, A third operation button 109, a first slide operator 110, and a second slide operator 111 are provided. Further, a head portion 120 including a lens and the like that can be attached to and detached from the fiber is provided at the ends of the light projecting fiber 2 and the light receiving fiber 3. Although not shown, the fiber photoelectric sensor includes an amplifier that clamps the fiber and incorporates a light projecting element and a light receiving element.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

2 Light emitting fiber, 3 Light receiving fiber, 4 Power cord, 10, 20, 30, 40, 70, 510, 530, 570 Light projecting unit, 11, 31, 41 LED (A), 12 Drive unit (A) , 13, 33, 73 LED (B), 14 Drive unit (B), 15 Emitting lens, 21 LED, 22 Drive unit, 50, 60, 550, 560 Light receiving unit, 51 Light receiving lens, 52 Photo diode, 53 Transformer Impedance amplifier, 54
High-pass filter, 55, 76 Signal processing unit, 56 Light projection control unit, 57, 77 General-purpose photo IC, 61 First light receiving element, 62 Red component filter, 63 Photodiode (A), 64 Second light receiving element, 65 Green component filter, 66 Photodiode (B), 67 Third light receiving element, 68 Blue component filter, 69 Photodiode (C), 70 Transimpedance amplifier (A), 71 Transimpedance amplifier (B), 72
Transimpedance amplifier (C), 73 High-pass filter (A), 74 High-pass filter (B), 75 High-pass filter (C), 101 Plastic housing, 102 Upper cover, 103 Clamp lever, 104 DIN rail fitting groove, 105 1st display, 106 2nd display, 107 1st operation button, 108 2nd operation button, 109 3rd operation button, 110 1st slide operator, 111 2nd slide operator, 120 Head part, 141 Core wire for ground, 142 Core wire for positive power supply, 143 Core wire for detection output, 144 Core wire for diagnosis output, 202 Protection member, 203 Light receiving window, 205 Indicator lamp, 206 Case, 301 Light projecting unit Holder member, 302 light receiving unit holder member, 303 light shielding member, 304 substrate, PD photo Diode, RF resistor, C capacitor, OP amplifier, Vcc power supply.

Claims (3)

A light receiving lens that receives the pulsed light incident from the detection region;
A photodiode that receives light obtained by biasing the pulsed light with direct current light and converts the light into an electrical signal;
A transimpedance amplifier that converts a current output from the photodiode into a voltage without applying a reverse bias to the photodiode;
A high-pass filter that removes DC light components from the voltage output from the transimpedance amplifier;
A first LED that outputs pulsed light;
A light projection lens for irradiating the detection region with the pulsed light;
A second LED that directly outputs direct-current light toward the photodiode;
The light projection lens is supported by a first holder member,
The light receiving lens is supported by a second holder member;
The first LED is disposed such that a light emitting portion is positioned at a focal position of the light projecting lens,
The photodiode is arranged at the focal position of the light receiving lens,
The photodiode, the transimpedance amplifier, and the high-pass filter are mounted on a substrate,
A light shielding member is provided so that light output from the first LED is not directly input to the photodiode,
The second LED is a photoelectric sensor arranged at a position where light output from the second LED is directly input to the photodiode. A plurality of light receiving elements, each receiving light that is incident from a detection region and biasing pulsed light with direct current light, and extracting a specific component of the light; and
A plurality of converters each for converting a current output from the light receiving element into a voltage without applying a reverse bias to the light receiving element to be connected;
A plurality of high-pass filters each removing DC light components from the voltage output from the converter to which it is connected;
A light projecting element that projects direct infrared light directly toward the plurality of light receiving elements;
The plurality of converters are light-receiving units of a photoelectric sensor, which are transimpedance amplifiers. The plurality of light receiving elements are:
A first light receiving element that receives light biased by direct current light from a detection region and extracts a red component and an infrared component of the light;
A second light receiving element that receives the light and extracts a green component and an infrared component of the light;
A third light receiving element that receives the light and extracts a blue component and an infrared component of the light;
The plurality of conversion units are:
A first converter that converts a current output from the first light receiving element into a voltage without applying a reverse bias to the first light receiving element;
A second converter that converts a current output from the second light receiving element into a voltage without applying a reverse bias to the second light receiving element;
A third converter that converts a current output from the third light receiving element into a voltage without applying a reverse bias to the third light receiving element;
The plurality of high pass filters are:
A first high-pass filter that removes a direct-current light component from the voltage output from the first converter;
A second high-pass filter that removes a direct-current light component from the voltage output from the second converter;
A third high-pass filter that removes a direct-current light component from the voltage output from the third converter,
The light projecting element projects infrared direct-current light directly toward the first light receiving element, the second light receiving element, and the third light receiving element,
The light receiving unit of the photoelectric sensor according to claim 2, wherein the first conversion unit, the second conversion unit, and the third conversion unit are transimpedance amplifiers.

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