JP2008103969A - Reflection sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflection sensor which is more applicable to multi-use and more accurate than conventional one, while being capable of certainly detecting whether the reflective light volume from an object to be detected increases or decreases for the reflective light volume from background, even in the case of the object to be detected having the same reflective light as the background. <P>SOLUTION: The reflection sensor 1 is constituted of light receiving parts R1-R4 in two or more positions where distance from a light projection part differs with respect to one light projection part P1. The respective light receiving parts comprise a window comparator function for emitting an ON or OFF signal as an output concerning existence or nonexistence of an object to be detected responding to the increase or decrease of light receiving volume to a threshold, and furthermore are constituted so as to cover mutually malfunction regions which may exist respectively by carrying out the logical adding (OR) of at least two decision outputs concerning the two or more light receiving parts. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a reflective sensor that can be applied not only to the FA industry but also to various consumer industries.

  First, the current situation surrounding the reflection type sensors will be described in order.

[First example]
FIG. 15 shows a circuit block diagram of a reflective sensor according to a conventional example.
As shown in FIG. 15, at least a light projecting / receiving system 10 ″, a signal conversion circuit system 20 ″, and an output circuit 30 are housed in the case of the reflective sensor 100 according to the conventional example. On the outer surface of the case, a lens L is provided on the front surface of each light projecting / receiving element of the 4-channel light projecting / receiving system 10 ″.
Each channel of the four-channel light emitting / receiving system 10 ″ shown in FIG. 15 includes light emitting / receiving elements (P11 to P41, R11 to R41) and their drive or amplifier circuits (P12 to P42, R12 to R42). It has become. In general, the light projecting elements P11 to P41 are made of LEDs.
Similarly, the signal conversion circuit system 20 ″ shown in FIG. 15 includes comparators R13 to R43 connected to the light receiving circuits R12 to R42, and an and circuit unit 24 connected to the outputs of the comparators R13 to R43 and the scanning circuit 27. (241 to 244), the or circuit unit 25 connected to the outputs of the and circuit units 241 to 244, the output of the or circuit unit 25 and the counter 26 connected to the scanning circuit 27, and the LED drive circuits P12 to Each of the inputs of P42 and AND sections 241 to 244 and a scanning circuit 27 connected to the counter 26 are included. An output circuit 30 is also connected to the counter 26. Adjustment of the threshold values of the comparators R13 to R43 is appropriately performed when the sensor is installed.

In this example, the LEDs are sequentially driven and projected by a scanning circuit 27 composed of a CPU or the like, and at this time, a signal of a light receiving circuit corresponding thereto is read by a counter 26 via an and circuit unit 24 and an or circuit unit 25.
For example, in the case of a reflector-type reflective sensor using a reflector as a background, the counter 26 sequentially counts every lighting cycle, and i) if there are four signals, it is regarded as all incident light, and the detected object Is not present between the sensor and the background (referred to as an “OFF” state for the sake of convenience), and conversely ii) if less than four, the detected object is present between the sensor and the background (for convenience) , Which is referred to as “ON” state).

First, the received light signals reflected from the reflector and incident on any of the light receiving elements R11 to R41 are amplified by the light receiving circuits R12 to R42, respectively.
Here, since the amount of received light reflected from the reflector is higher than a predetermined threshold value of each of the comparators R13 to R43, the waveform is shaped by the comparator and a comparator output signal is obtained. If the detected object does not exist between the sensor and the background, the output of the counter 26 is 4 counts. Based on this, the output circuit 30 determines that there is no detected object between the sensor and the background (OFF).

  On the other hand, when an object to be detected (such as a hand or a black object that absorbs light) is inserted between the reflector as the background and the sensor, the light receiving elements R11 to R41 that are shielded by the object to be detected are received. Since the amount of light decreases and the received light level becomes lower than the threshold value of the comparators R13 to R43, there is no output from the comparators R13 to R43. It is determined that it is inserted between them (ON) ", and an ON signal is output from the sensor.

  As described above, in general, in the case of the reflector type, the detection is performed when the light reception signal reflected from the object entering between the reflector and the sensor is smaller than the light reception signal reflected from the reflector and incident on the light receiving unit. A signal (ON signal from the sensor) is output.

Therefore, when the object to be detected is a mirror body such as a mirror or a SUS plate, the amount of reflection from the mirror body may be larger than the amount of reflection from the reflector. However, the counter 26 outputs 4 counts even though it is inserted. As a result, there is a problem that the detected object cannot always be detected reliably.
Also, even when a white object such as white paper is used instead of a specular body, the density of reflected light is high when it is very close to the sensor. At this time, the amount of light received is greater than the amount reflected from the reflector. May be obtained. Therefore, even in this case, like the mirror body, there is a problem that the detected object cannot always be reliably detected.

  FIG. 16 shows the distance output characteristic in the light receiving part of the reflection type sensor according to the conventional example, that is, the distance output characteristic of one optical axis. A in the graph shows the amount of light received (received light output) with respect to the distance between the sensor and the reflector when a reflector is used as the background. B shows the distance between the sensor and the white paper using white paper as the background. It represents the amount of light received.

  If a reflector is installed at a position 2 m from the sensor, and the light reception output shown on the vertical axis in FIG. 16 is 100, the detection threshold of the sensor output is inserted, and the detected object is inserted between the sensor and the reflector. When the light reception level at 100 becomes 100 or less, an ON signal is output from the sensor.

Here, if the detected object inserted between the sensor and the reflector is white paper, the amount of light received by the light receiving unit is 100 or more when the position of the white paper is within 15 cm from the sensor as shown in FIG.
Then, although the detected object is inserted, the above determination condition is not satisfied, and therefore there is a problem that white paper cannot be detected within 15 cm from the sensor, that is, it cannot be determined that there is a detected object. (So-called dead band problem).

  Therefore, in order to distinguish between the reflected light from such white paper and the reflected light from the usual reflector (as a background), for example, a polarizing filter is provided on the lens L surface of the sensor 100, and i) Reflected light (Ex. Transverse wave) from the reflector (ex. Polarization type that converts longitudinal wave to transverse wave) passes through the polarizing filter, while ii) reflected light from other objects (longitudinal wave if longitudinal wave) The method of blocking with a polarizing filter is also used (polarization reflector type sensor).

  However, for example, in an object coated with a transparent film, the original polarization characteristics of the object may be lost depending on the characteristics of the coated film. Therefore, the reflected light from the object should be blocked by the polarizing filter, but when coated with a film, the reflected light from the detected object may pass through the polarizing filter. However, there is a problem that the detected object cannot always be detected reliably.

  In addition, the polarization reflector type sensor has a problem in that since the light emitting side and the light receiving side are provided with the polarizing filter, the amount of light attenuation by the polarizing filter is large, and the distance between the sensor and the background (reflector) cannot be made long.

  Generally, a single polarizing filter has a transmittance of about 50%. If this is provided on both the light projecting side and the light receiving side, the amount of light that can finally be received is when the polarizing filter is not used. Compared to 0.5 × 0.5 = 0.25, that is, 25%. When this is converted into distance, the detection distance is 50% compared to the case where no polarizing filter is used (the amount of light is inversely proportional to the square of the distance).

In addition, when the reflective sensor is configured as a polarizing reflector using, for example, a polarizing filter and a reflector (polarization type) as described above, the reflected light from a glossy surface reflecting object such as a stainless steel plate is the above. Therefore, there is a problem in that it is impossible in principle to use the reflection type sensor of this configuration not only as a reflector type but also as a diffuse reflection type.
As described above, when the polarizing filter is used, not only the problem of attenuation but also the problem that the reflective sensor cannot be shared as the (polarized) reflector type and the diffuse reflection type.

[Second example]
Next, in the case of a diffuse reflection type reflective sensor that captures the amount of light reflected directly from the object to be detected, either the increase in the amount of light from the object to be detected or the decrease in the amount of light with respect to the amount of light reflected from the background. Object detection is performed.

  Therefore, in the case of a device having a structure that detects an object by increasing the amount of reflected light from the object to be detected with respect to the amount of reflected light from the background (light incident ON operation), the object having a reflected light amount lower than the amount of reflected light from the background For example, a black object could not be detected.

  On the other hand, in the case of a device with a structure that detects an object by reducing the amount of reflected light from the object to be detected (light-shielding ON operation) with respect to the amount of reflected light from the background, an object having a reflected light amount higher than the reflected light amount from the background For example, white objects and polished SUS plates could not be detected.

  In addition, in the case of the diffuse reflection type reflection type sensor, since it is operated by the direct reflected light from the object to be detected, there is a drawback that the detection distance cannot be made long. The detection distance of the conventional diffuse reflection type is about 50 cm.

[Third example]
In addition, as a conventionally known reflection type sensor, there is one using a position detection element (PSD element) or a two-divided photodiode in a light receiving part.
However, these circuits are complicated and expensive. Further, since the operation is performed with the directly reflected light from the object to be detected, there is a drawback that the detection distance cannot be made long as in the case of the diffuse reflection type. Furthermore, there are directions that cannot be detected depending on the passing direction of the object, which may cause restrictions on the mounting direction and cause malfunctions.

By the way, in picking (work instruction) systems that are frequently used in recent production lines, work instruction sensors (picking sensors) are often used to prevent mistakes in parts removal and to replace a confirmation switch that detects a hand and picks up the parts. Has been.
However, the current picking sensor is a transmission type in which a projector is installed on one side of the component shelf and a light receiver is installed on the opposite side, and a plurality of sensors must be installed on many component shelves. There was a problem that had to be done. For this reason, due to the large number of wirings and high installation costs, it was difficult to employ only some major companies with economic power and limited production processes.
JP 62-261221 A JP-A-62-38614 JP 59-158029 A

As described above, the conventional reflective sensor detects an object by detecting either an increase in received light amount or a decrease in received light amount. Therefore, the detected object that can be detected by the sensor is restricted by the surface state. If the amount of light reflected from the detected object is the same as the amount of light reflected from the background, the object could not be detected at this time.
Therefore, if the sensor is i) used for counting passing objects, an error occurs in the count value, or if the sensor is used for detecting the passage of objects in an automated line, a signal indicating that there is an object is issued even if there is an object. As a result, there was a possibility that trouble would occur in the automated line. Further, iii) If it is a work instruction sensor for picking up a component (commonly called a picking sensor), there is a possibility that the operator's hand cannot be detected or it is determined that the component is taken twice by chattering.

  Therefore, the present invention solves the above-mentioned problem, even in the case of a detected object having the same reflected light as the background, and also in the case where the reflected light amount from the detected object is both increased and decreased with respect to the reflected light amount from the background. It is an object of the present invention to provide a reflective sensor that can be reliably detected and can be applied to more applications with higher detection accuracy than conventional ones.

  As a result of various studies to solve the above problems, the inventor of the present application is configured with a pair of light projecting portions and light receiving portions (1: 1) in the same case as a conventional general reflection type sensor. On the other hand, the reflection type sensor is newly combined with a combination of i) a light projecting unit 1: a plurality of light receiving units, and ii) a light receiving unit at a position where the distance from the light projecting unit is different from each other centering on the light projecting unit. Arrangement, that is, by arranging the light receiving elements with a single eye and different angles of incident light with respect to one light projecting unit, the peak point of the amount of light received incident on each light receiving element, Eventually, these malfunctioning areas are shifted, and finally, at least two judgment outputs relating to the plurality of light receiving sections are taken or so that the malfunctioning areas are covered with each other. To raise the above issues It found that it is possible decisions, which resulted in the completion of the present invention.

  The reflection type sensor of the present invention capable of solving the above problems is (1) a reflection type sensor, wherein light receiving parts are arranged at a plurality of positions at different distances from the light projecting part with respect to one light projecting part. Each of the light receiving units is provided with a window comparator function for generating an ON or OFF signal related to the presence or absence of a detected object at the output by increasing or decreasing the amount of received light with respect to a threshold, and further, the plurality of light receiving units It is characterized in that it is configured to cover malfunction areas that can exist by taking or of at least two judgment outputs according to the above.

  The reflection type sensor according to the present invention is (2) a reflection type multi-optical axis sensor having a plurality of light projecting units and a plurality of light receiving units. A plurality of positions having a window comparator function for generating an ON or OFF signal related to the presence or absence of a detected object in the output and having different linear distances from the light projecting unit other than the light receiving unit opposed to one light projecting unit When the light projecting unit sequentially emits light in a pulse operation using the light receiving unit, the malfunction regions that can exist by taking at least two judgment outputs of the plurality of light receiving units are provided. It is characterized by being configured to cover each other.

  In the description of the present invention, the “light receiving portion” is a light receiving element, a lens provided in front of the light receiving circuit, a light receiving circuit that receives an output from the light receiving element and performs amplification, and receives an output from the light receiving circuit. The A / D converter that sends the output to the CPU according to the A / D converter, the A / D converter that A / D converts the output from the multiplexer, and the output from the A / D converter in the CPU are also stored in advance in the CPU. The window comparator section that performs ON / OFF determination in comparison with the threshold value is generically designated. Some of these components are shared with other light receiving units. However, the determination output (ON / OFF) of each light receiving unit that is finally output from the window comparator unit is unique to each light receiving unit.

According to the present invention, by arranging the light receiving elements with respect to one light projecting unit with different eyes and different angles of incident light, the peak point of the amount of light received incident on each light receiving element. As a result, the respective malfunction areas are shifted, and finally, at least two determination outputs relating to the plurality of light receiving sections are taken or so, the malfunction areas are covered with each other.
Therefore, even if each of the light receiving elements in the plurality of light receiving sections is in a situation where erroneous determination or malfunction may occur, follow-up from another light receiving element can be obtained. In the reflective sensor according to the above, a so-called dead zone in which an object cannot be detected is eliminated.

  Further, according to the present invention, it is possible to reliably detect a detected object having the same reflected light as that of the background, and also when the amount of reflected light from the detected object is both increased and decreased with respect to the amount of reflected light from the background. A reflective sensor is obtained.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram showing an example of the arrangement of the light receiving unit with respect to the light projecting unit. A shows a case where the light receiving unit is arranged concentrically with the light projecting unit as a center, and B shows a case where the light receiving unit is arranged linearly. FIG. 2 is a diagram showing an example of a condensing pattern in a plurality of light receiving elements, and FIG. 3 is a diagram showing distance output characteristics of each light receiving element when white paper is used as a background. FIG. 4 is a diagram showing an example of the configuration of a reflective sensor having a window comparator function, where A is a block diagram and B is a time chart. FIG. 5 is a diagram showing the distance output characteristics of each light receiving element when white paper is used as the background in the same manner as in FIG. 3, and it is assumed that there is a background at a distance of 40 cm from the light projecting portion, and reflection from the background. FIG. 5 is a diagram illustrating an example of a state when the threshold value is adjusted so that the sensor is in an OFF state. FIG. 6 is a diagram illustrating distance output characteristics of each light receiving element when a detected object having a reflectance of 50% with respect to the background is inserted. FIG. 7 is a diagram showing the positional relationship of the optical system and the light density of the light reflected by the reflector when a reflector is used as the background, and FIG. 8 is a distance output of each light receiving element when the reflector is used as the background. It is a figure which shows a characteristic. FIG. 9 is a diagram showing the distance output characteristics of each light receiving element when a reflector is used as a background. Now, the reflector is arranged at a distance of 2 m from the sensor, and the sensor is turned off by reflection from the reflector. It is a figure which shows an example of a mode when a threshold value is adjusted.
In the present specification, the same reference numerals are used for the same components between the drawings.

[First embodiment: When white paper is used for the background]
First, the configuration and various characteristics of the reflective sensor according to the present invention when white paper is used as the background will be described.

FIG. 1 shows an example of how the light receiving parts are arranged with respect to the light projecting part. In the present invention, a plurality of light receiving units having different distances from the light projecting unit are arranged for one light projecting unit. In other words, in the present invention, the light receiving parts are arranged at a plurality of positions having different distances from the light projecting part concentrically (FIG. 1A) or linearly (FIG. 1B) with the light projecting part as the center. As a result, the light receiving area (band) is diffused, and the change in the amount of received light is captured in a wider area than before.
In the following, for easy understanding, description will be made on one optical axis portion (one light projecting portion) of the multi-optical axis sensor. In addition, as an example of a plurality of light receiving units, an example in which there are two light receiving units will be described below. The overall configuration related to the multi-optical axis sensor itself will be described in a later embodiment.

  In addition, as will be described in detail in the description of the modification of the latter stage, normally, a combination in which two light receiving elements having different separation distances with respect to one element of the light projecting unit are arranged as the light receiving unit is preferable. In order to further improve the accuracy of the sensor according to the installation environment and other circumstances, as shown in FIG. 1, a combination in which three or more light receiving elements each having a different separation distance with respect to one light projecting part is arranged as a light receiving part. You can take it.

FIG. 2 shows an example of a condensing pattern in a plurality of light receiving elements. The light emitted from the light projecting element of the light projecting unit P1 is irradiated to the background through the lens L. The light reflected from the background is condensed through the lens L to the light receiving elements R1 and R2.
The angles θ1 and θ2 are incident angles formed by the main component of the reflected light from the light projecting element with respect to the main optical axis of each light receiving element of the light receiving portions R1 and R2. The incident angles θ1 and θ2 themselves do not change even if the light receiving parts are arranged concentrically (FIG. 1A) or linearly (FIG. 1B) with respect to the light projecting part.

FIG. 3 shows the distance output characteristics (the amount of light received with respect to the distance) of the light receiving elements of the light receiving portions R1 and R2 when white paper is used as the background. The vertical axis represents the amount of light received by each light receiving element (light reception output), and the horizontal axis represents the distance from the light projecting element.
Looking at the characteristics of the light receiving portion R1, the light receiving level is generally higher than that of the light receiving portion R2, and the peak position is closer to the light projecting element. On the other hand, looking at the characteristics of the light receiving part R2 far from the light projecting part P1, the light receiving level is generally lower than that of R1, and the peak position is further away from the light projecting element. In both cases of the light receiving portions R1 and R2, when the separation distance becomes longer after the peak point, the amount of received light becomes a characteristic inversely proportional to the square of the distance.

  As described above, in the present embodiment, a plurality of light receiving units are arranged at different positions from the light projecting unit, and a plurality of light receiving units having different distance output characteristics with respect to one light projecting unit are provided.

Next, the conventional reflection type sensor detects either an increase in the amount of received light or a decrease in the amount of received light. In this embodiment, a window comparator is used for processing the received light signal received by the light receiving unit. Made it functional. As a result, the light receiving unit operates by issuing an ON or OFF signal related to the presence / absence of the detected object as a sensor output, regardless of whether the amount of received light increases or decreases with respect to the threshold value.
In order to make this window comparator function easy to understand, a block diagram and a time chart relating to a system of one optical axis having the same function are shown in FIG. 4 and its operation will be described.

  FIG. 4 is a diagram showing an example of the configuration of a reflective sensor having a window comparator function, where A is a block diagram and B is a time chart. In FIG. 4, a system configuration with a light projecting / receiving element = 1: 1 is described as an example so that the explanation of the window comparator function is easy to understand.

In the case of the reflective sensor 1 ′ illustrated in FIG. 4A, at least a light projecting / receiving system 10 ′, a signal conversion circuit system 20 ′, an output circuit 30, and a sensitivity adjustment switch SW1 are housed. A lens L is provided on the front surface of each light projecting / receiving element P11, R11 of the light projecting / receiving system 10 ′.
The light projecting / receiving system 10 'is composed of light projecting / receiving elements P11, R11 and their drive or amplifier circuits P12, R12.
The signal conversion circuit system 20 ′ includes an A / D conversion unit 22 connected to the light receiving circuit R12, and a CPU 23 connected to the A / D conversion unit 22 and the LED driving circuit P12 for light projection.

  In the example shown in FIG. 4, the CPU 23 is connected to at least the A / D conversion unit 22, and also includes a window comparator unit 231 that sends its own determination output to the output circuit 30 outside the CPU 23 as a sensor output, and a window comparator. 231 and a sensitivity adjustment switch SW1 external to the CPU 23, and threshold values Vi, window width V0, upper and lower limit values VHref, VLref, and the like in the light receiving unit R1 input to the CPU 23 using the sensitivity adjustment switch SW1 are stored. A storage unit 232 is included.

  The CPU 23 is also connected to an output circuit 30 and a sensitivity adjustment switch SW1. Regarding the adjustment of the threshold (sensitivity adjustment), this sensitivity adjustment switch SW1 is used to set the sensor at other appropriate timing.

The LED drive circuit P12 is connected to the CPU 23, and drives and emits the LED based on a command sent from the CPU.
The output of the light receiving circuit R12 is sent to the output circuit 30 via the A / D converter 22 and the CPU 23, and finally outputted as a sensor output of “ON” or “OFF”. In the example shown in FIG. 4, the window comparator function is configured to be realized by the CPU 23.

4B is a time chart showing the operation of the reflective sensor having a window comparator function according to the configuration shown in FIG. 4A.
In FIG. 4B, V0 is the window width, R111 and the light receiving level Vi are the amount of light received from the background W when no insert is inserted between the background W and the light projecting / receiving system 10 ′, and R112 and the light receiving level VHref are The amount of light received by the light receiving element R11 when a mirror, a SUS plate or other reflective object is inserted between the background W and the light projecting / receiving system 10 '. The amount of light received by the light receiving element R11 when inserted between the systems 10 ′ is shown.

In the example shown in FIG. 4, the upper limit side and the lower limit are set based on the received light amount Vi from the background W when no object to be detected is inserted between the sensor 1 ′ and the background W by the input of the sensitivity adjustment switch SW1. Thresholds VHref and VLref (= the window width V0) are determined.
When the amount of received light exceeds the upper limit side threshold value VHref, it is determined that the detected object (related to the reflecting object) is inserted between the sensor 1 ′ and the background W, and “ON” for convenience. Sensor output. Similarly, when the amount of received light falls below the lower limit side threshold value VLref, it is determined that the detected object (related to the absorber) is inserted between the sensor 1 ′ and the background W. The sensor output is “ON”.
As described above, in the example shown in FIG. 4, by adopting the window comparator function, the sensor output is performed even if the amount of received light increases or decreases with respect to the threshold value.

In the present embodiment as well, as in the example shown in FIG. 4, a window comparator that outputs an ON or OFF signal related to the presence or absence of a detected object to the output by increasing or decreasing the amount of received light with respect to the threshold value in each of the plurality of light receiving units. By providing the function, the sensor output is made even if the amount of received light increases or decreases with respect to the threshold value.
Further, in the present embodiment, at least two determination outputs related to a plurality of light receiving units are taken to cover the malfunctioning regions that may exist, which will be described next.

  FIG. 5 is a diagram showing the distance output characteristics of each light receiving element when white paper is used as the background in the same manner as in FIG. 3, and it is assumed that there is a background at a distance of 40 cm from the light projecting portion, and reflection from the background. FIG. 5 is a diagram illustrating an example of a state when the threshold value is adjusted so that the sensor is in an OFF state. V01 and V02 are window widths, and Vi1 and Vi2 are the basis for determining that “no detected object is inserted” (for convenience, the sensor output is in the “OFF” state). It is the threshold which becomes. The window widths V01 and V02 are determined by upper limit values VHref1 and VHref2 and lower limit values VLref1 and VLref2.

  In FIG. 5, it is assumed that there is a background at a distance of 40 cm from the light projecting unit, and at this time, the amount of light received by each light receiving element in a state where no object to be detected (reflecting material, absorbing material) is inserted ( In the figure, the threshold value (Vi1, Vi2) is the median light reception level indicated by the shaded lines. The light receiving levels indicated by the shaded lines in the figure correspond to the window widths V01 and V02, but the actual widths are determined from the upper limit values VHref1 and VHref2 and the lower limit values VLref1 and VLref2 that are appropriately selected. .

In the present embodiment, when the amount of light received by each light receiving element exceeds the upper limit values VHref1 and VHref2 or falls below the lower limit values VLref1 and VLref2, the “reflector or absorber” It is determined that any object to be detected is in a state of being inserted between the sensor and the background (for convenience, the sensor output is referred to as being “ON”) ”. When the upper limit value is exceeded, the reflecting material is inserted, and when the lower limit value is not reached, the absorbing material is inserted.
In other words, the threshold adjustment (also referred to as sensitivity adjustment) is performed so that the sensor output is in the “OFF” state only when the reflected light from the background is incident on each light receiving element. This threshold adjustment (sensitivity adjustment) is appropriately performed manually or automatically at other appropriate timings when the sensor is installed.

  Looking at the distance output characteristic curve of each light receiving element, with respect to the light receiving part R1, there is no place where the light receiving level indicated by the shaded line in the drawing is at a distance other than the distance of 40 cm from the light projecting part. Even though the object is inserted between the sensor and the background (the sensor output is in the “ON” state), it is erroneously stated that “the detected object is not inserted”. There is no determination (the sensor output is in the “OFF” state).

However, looking at the distance output characteristic curve related to the light receiving element of the light receiving portion R2, in addition to the distance of 40 cm from the light projecting portion, it is indicated by a shaded line in the drawing at a location near 18 cm from the light projecting portion. There is a place where the light reception level is reached. In this case, since the amount of received light is in the range of the window width V02, the light receiving unit R2 alone is “OFF” even though, for example, white paper similar to the background is in the vicinity of 18 cm from the light projecting unit. It will be judged that it is in a state.
As described above, when only the light receiving unit R2 is used alone, for example, a white paper or a detected object having similar properties and distance output characteristics is located between the sensor and the background, at a position near 18 cm from the light projecting unit. Although the sensor output should be in the “ON” state even if it is in the state of being inserted into the device, it is erroneously stated that “the detected object is in a state in which no object is inserted”. (Sensor output is in an “OFF” state). That is, in the light receiving unit R2 alone, a so-called dead zone in which an object cannot be detected may occur.

  However, according to the present embodiment, the determination output in the plurality of light receiving units R1 and R2 is finally taken to cover the malfunction areas that may exist in each. Therefore, even if the light receiving unit R2 alone is in a situation where erroneous determination or malfunction may occur, follow-up from the light receiving unit R1 can be obtained. Therefore, the reflective sensor according to the present embodiment detects an object. The so-called deadband that cannot be done has been eliminated.

As described above, in the present embodiment, the detected object having various characteristics is detected from the sensor and the background with the distance of 40 cm between the background and the sensor as the center, whether the background is close to the sensor side, away from the sensor, or various characteristics. The light receiving units R1 and R2 are in an “ON” state even if they are inserted between the two.
As the sensor output, if one of the two light receiving units R1 and R2 outputs the “ON” state, the final sensor output also outputs the “ON” state. The determination output in the light receiving unit 2 (R2) is taken or.

FIG. 6 is a diagram illustrating distance output characteristics of the light receiving elements of the light receiving units R1 and R2 when “a detected object having a reflectance of 50% with respect to the background is inserted”.
Since the reflectance is 50%, the light reception amount is 50% over the entire distance with respect to the characteristics shown in FIG.

  Then, for example, when a detected object having white paper or similar properties and distance output characteristics is located at a distance of about 28 cm from the sensor 1, the light receiving unit R1 has an insert in advance between the sensor and the background. The amount of received light is the same level as the threshold value (or window width) when the sensitivity is adjusted when there is not, and “the detected object is in a state where nothing is inserted” even though the detected object is inserted. A so-called dead zone is generated in which the determination is erroneously made (the sensor output is in an “OFF” state).

  On the other hand, since the light receiving level of the light receiving unit R2 is lower than the window width V02 over the entire distance, the output of the light receiving unit R2 is in a state where the detected object is inserted between the sensor and the background over the entire distance range. (Sensor output is in the “ON” state).

As in the prior art, if one light receiving unit (only the light receiving unit R1) is provided for one light projecting unit, the object to be detected having a reflectance of 50% with respect to the background is a distance from the sensor 1 as described above. When it is in the vicinity of 28 cm, the object cannot be detected, and a so-called dead zone occurs.
However, in the present embodiment, the sensor output is obtained by taking the judgment output of the plurality of light receiving units R1 and R2, or the output of R2 covers the vicinity of 28 cm where R1 is in the OFF state as described above. To do. Therefore, there is no so-called dead zone in which no object can be detected under this embodiment.

  As described above, in the present embodiment, the light receiving unit is arranged at a plurality of positions having different distances from the light projecting unit with respect to one light projecting unit, and the sensor includes a plurality of optical systems having different distance output characteristics. As a result, each dead zone becomes an optical system that does not match. For this reason, there is no so-called dead zone in which no object can be detected under this embodiment.

[Second Embodiment: When a reflector is used for the background]
Next, the structure and various characteristics of the reflective sensor according to the present invention when a reflector is used as the background will be described.

FIG. 7 is a diagram showing the arrangement relationship of the optical system and the light density of the light reflected by the reflector when a reflector is used as the background.
As described in the first embodiment, if the background is a diffuse reflection object such as white paper, the reflected light is an averaged diffused light.
On the other hand, the reflector has a characteristic of strongly returning light to the light projecting side irradiated with light. As shown in FIG. 7, the light incident on the reflector attempts to return to the original optical path. . Therefore, the light density is not so wide as shown in FIG. Therefore, even in the same optical system, the amount of light received by the light receiving unit R2 away from the light projecting unit has a characteristic that is logarithmically smaller than that of the light receiving unit R1 (see FIG. 8 described below).

FIG. 8 shows the distance output characteristics of the respective light receiving elements of the light receiving portions R1 and R2 when a reflector is used as the background.
Looking at both characteristics, the positions of the light receiving parts R1 and R2 are different from the light projecting part, so that the positions of the peaks of the light receiving quantities of both are shifted. The amount of received light gradually decreases at a substantially constant rate as the distance from the light projecting unit increases. That is, the light receiving amount at the light receiving portion gradually decreases as the reflector as the background moves away from the sensor.

  FIG. 9 is a diagram showing the distance output characteristics of each light receiving element when the reflector W ′ is used as the background as in FIG. 8. The reflector W ′ is now disposed at a distance of 2 m from the sensor 1, and the reflector W ′. It is a figure which shows an example of a mode when the threshold value with a window width | variety is adjusted so that the sensor 1 may be in an OFF state by reflection from. V01 and V02 are the respective window widths. The window widths V01 and V02 are determined from upper limit values VHref1 and VHref2 and lower limit values VLref1 and VLref2 as in the example shown in FIG.

Vi1 and Vi2 are light receiving levels of the light receiving parts R1 and R2 when the reflector W ′ is placed at a position 2 m from the sensor. Vi1 and Vi2 correspond to threshold values serving as a basis for performing a determination that “no detected object is inserted” (the sensor output is in the “OFF” state).
As described above, the outputs of the light receiving portions R1 and R2 are adjusted to be in the OFF state based on the reflected light reception amounts Vi1 and Vi2 from the reflector W ′ located 2 m from the sensor 1 (threshold or sensitivity adjustment). ).

Here, it is assumed that the white paper is inserted between the sensor 1 and the reflector W ′. FIG. 9 also shows distance output characteristics (both R1 and R2) when white paper is inserted between the sensor 1 and the reflector W ′.
If the conventional light projecting unit and one light receiving unit are used, the light receiving unit is, for example, only R1, so that the distance from the sensor 1 to 2 m is about 13 cm as shown in the lower part of the graph of FIG. The amount of light received is the same as the amount of reflected light Vi1 from the reflector W ′ when the reflector W ′ is arranged, and a white band cannot be detected at this position due to a dead zone.

  On the other hand, when the light receiving unit is only R2, for example, a dead zone is generated as is apparent from the distance output characteristics of the light receiving unit R2 when white paper is inserted between the sensor and the background shown in FIG. Absent.

  According to the present embodiment, the determination output in the plurality of light receiving units R1 and R2 is finally taken to cover the malfunction areas that may exist in each of them. Therefore, even if the light receiving units R1 and R2 alone can cause erroneous determination and malfunction, follow-up from another light receiving unit can be obtained. The so-called dead zone that cannot be detected is eliminated.

  Here, considering that it is preferable to make the distance output characteristics of at least a plurality of light receiving parts different from each other in order to eliminate the dead zone and to eliminate erroneous detection and malfunction, the first embodiment and the second embodiment described above. In the example, i) if the distance from the background is within about 40 cm, it is used as a diffuse reflection type, and ii) if the background is about 40 cm to 2 m (or more), by using a reflector, It is understood that an object can be detected reliably.

As understood from each of the above descriptions, the present invention provides i) arranging a plurality of light receiving units with respect to one light projecting unit, and ii) regarding the plurality of light receiving units relative to the light projecting element. This is characterized in that the distance is changed, thereby changing the condensing pattern appearing on each light receiving element (from the light projecting element) so as to cancel out the dead zones generated from each other.
At this time, the present invention adopts a configuration using a window comparator when processing the output from each light receiving element, and finally taking or of at least two determination outputs related to the plurality of light receiving units, It covers the malfunctioning areas that can exist in each.

In the following, an embodiment of the present invention will be described. FIG. 10 shows the appearance of the reflective sensor according to this embodiment, and FIG. 11 shows a circuit block diagram.
As shown in FIG. 10, in this embodiment, a reflection type multi-optical axis sensor having four optical axes having the same appearance as the conventional example is selected as an object to which the present invention is actually applied.

In the description so far, the structure which has arrange | positioned two light-receiving parts with respect to one light projection part was taken. By the way, since the conventional reflection type multi-optical axis sensor already includes a plurality of light projecting units and light receiving units, the function of the present invention can be realized without specially adding a light receiving unit. .
As described above, the present invention can be realized only by changing the circuit and CPU program without changing the structure of the conventional reflection type multi-optical axis sensor, and is extremely cost effective. It is highly efficient.

As shown in FIGS. 10 and 11, in the case of the reflective sensor 1 according to this embodiment, a light projecting / receiving system 10, a signal conversion circuit system 20, an output circuit 30, an operation indicator lamp M, and a sensitivity adjustment switch SW1 are provided. It is paid. As shown in FIG. 10, a 4-channel (described later) light projecting / receiving system 10 and an operation indicator lamp M appear on the outer surface of the case. A lens L is provided in front of each light projecting / receiving element of the light projecting / receiving system 10. A sensitivity adjustment switch storage part SW1 ′ appears in the lower left part of FIG. 10, and the sensitivity adjustment switch is housed here.
Each channel of the four-channel light emitting / receiving system 10 shown in FIG. 11 is composed of light emitting / receiving elements (P11 to P41, R11 to R41) and their drive or amplifier circuits (P12 to P42, R12 to R42). Yes. In the present embodiment, the light projecting elements P11 to P41 are made of LEDs.
As described above, the “light receiving unit” refers to a light receiving element, a lens provided in front of the light receiving circuit, a light receiving circuit that receives an output from the light receiving element and performs amplification, and receives an output from the light receiving circuit. A multiplexer that sends the output to the CPU side, an A / D conversion unit that performs A / D conversion on the output from the multiplexer, and an output from the A / D conversion unit in the CPU, and a threshold value stored in advance in the CPU In contrast, a window comparator unit that performs ON / OFF determination is generically designated. Some of these components are shared with other light receiving units. However, the determination output (ON / OFF) of each light receiving unit that is finally output from the window comparator unit is unique to each light receiving unit.
Similarly, the signal conversion circuit system 20 shown in FIG. 11 includes a multiplexer 21 connected to each of the light receiving circuits R12 to R42, an A / D conversion unit 22 connected to the multiplexer 21, an A / D conversion unit 22, and each projection circuit. The CPU 23 is connected to the optical circuits P12 to P42.
In the present embodiment, as shown in FIG. 11, the CPU 23 is connected to at least the window comparator unit 231 connected to the A / D conversion unit 22, the window comparator unit 231, and the sensitivity adjustment switch SW 1 outside the CPU 23. A storage unit that is connected to the threshold value storage unit 232 that stores the threshold value, window width, upper and lower limit values, and the like of each light receiving unit input to the CPU 23 using the SW 1 and the window comparator unit 231, and stores a determination output therefrom 233, and an or circuit unit 234 that takes at least two determination outputs of the plurality of light receiving units R1 to R4 stored in the storage unit 233, and sends them as output to the output circuit 30 outside the CPU 23. .
The CPU 23 is connected to an output circuit 30, an operation indicator M, and a sensitivity adjustment switch SW1. Regarding the adjustment of the threshold (sensitivity adjustment), this sensitivity adjustment switch SW1 is used to set the sensor at other appropriate timing.

The LED drive circuits P12 to P42 are connected to the CPU 23, and drive and emit LEDs of each channel based on a command sent from the CPU. Each of the light receiving circuits R12 to R42 is connected to the multiplexer 21 of the signal conversion circuit system 20.
The outputs of the light receiving circuits R12 to R42 are sent to the output circuit 30 via the multiplexer 21, the A / D converter 22 and the CPU 23, and finally output as sensor outputs of “ON” or “OFF”.

The operation, characteristics, and effects of the reflective sensor 1 according to the present embodiment having the above-described configuration are basically the same as those described in the previous embodiments.
That is, the reflective sensor 1 according to the present embodiment is a reflective multi-optical axis sensor having a plurality of light projecting units P1 to P4 and a plurality of light receiving units R1 to R4, and each of the light receiving units R1 to R4, A window comparator function is provided that emits an ON or OFF signal related to the presence or absence of a detected object as an output by increasing or decreasing the amount of received light with respect to the threshold.
At the same time, the reflective sensor 1 according to the present embodiment has a linear distance from the light projecting unit other than the light receiving unit (for example, the light receiving unit R11 corresponding to the light projecting unit P11) opposed to one light projecting unit. When the light receiving units P1 to P4 are sequentially projected in a pulse operation based on a command from the CPU 23 using a plurality of light receiving units at different positions, for example, a plurality of light receiving units R1 in the following manner By taking or of at least two determination outputs related to .about.R4, it is configured to cover each malfunction region that may exist.

An example of detailed operation of the reflective sensor 1 according to the present embodiment will be described. The light projecting units P1 to P4 are sequentially projected by a pulse operation based on a command from the CPU 23.
i) First, the light projecting element P11 is turned on. At this time, the output of the light receiving unit R1 facing each other is selected by the multiplexer 21 and taken into the CPU 23, and the CPU 23 determines ON / OFF. The threshold used in this case corresponds to Vi1 shown in FIG. 5 if the diffuse reflection type is taken as an example. The window width and the upper and lower limit values thereof also correspond to the corresponding V01, VHref1, and VLref1, respectively.
ii) Next, the same light projecting element P11 is turned on, and this time, the output of the light receiving unit R2 at a more distant position is selected by the multiplexer 21 and taken into the CPU 23, and the CPU 23 determines ON / OFF in the same manner as before. Do. Unlike the previous case, the threshold used in this case corresponds to Vi2 shown in FIG. 5 (in the case of the diffuse reflection type). The window width and the upper and lower limit values thereof also correspond to the corresponding V02, VHref2, and VLref2, respectively.
iii) In the CPU 23, i) and ii) or of the two determination outputs is taken as an output from one channel (a combination of the light projecting / receiving units P1, R1; CH1).
iv) Similarly, since it has multiple optical axes, it proceeds to the next channel and turns on the light projecting element P21. At this time, the output of the opposite light receiving unit R2 is selected by the multiplexer 21 and taken into the CPU 23. Determine OFF. Other than the threshold value in that case, it is the same as i).
v) Subsequently, the same light projecting element P21 is turned on, and the output of the light receiving unit R1 at a distant position is selected by the multiplexer 21 and taken into the CPU 23, and the CPU 23 determines ON / OFF. Other than the threshold value in that case, it is the same as ii).
vi) The CPU 23 again takes this iv), v) or of the two determination outputs, and outputs it from the second channel (combination of light projecting / receiving units P2, R2; CH2).
vii) After repeating the above operation for the number of channels (4 channels in this embodiment; CH1 to CH4), the output of each channel CH1 to CH4 is finally taken as an output circuit as a sensor output. 30 is output.

The way of taking out the output from CH3 and CH4 can also be the same as above. For example, the following way is also possible.
i) Regarding 'CH3 (a combination of the light projecting and receiving units P3 and R3), first, the light projecting element P31 is turned on. At this time, the output of the opposing light receiving unit R3 is selected by the multiplexer 21 and taken into the CPU 23. / OFF is determined. In this case, the threshold value and the like are the same as in i).
ii) Next, the same light projecting element P31 is turned on, and this time, the output of the light receiving unit R4 at a further distance is selected by the multiplexer 21 and taken into the CPU 23, and the CPU 23 determines ON / OFF in the same manner as before. I do. Other than the threshold value in that case, it is the same as ii).
iii) 'At CPU 23, i)' and ii) 'take the two judgment outputs or and output them from CH3.
iv) 'In the same manner, the process proceeds to the next channel CH4 (a combination of the light projecting and receiving units P4 and R4) to turn on the light projecting element P41. At this time, the output of the opposing light receiving unit R4 is selected by the multiplexer 21 and taken into the CPU 23 Then, the CPU 23 determines ON / OFF. Other than the threshold value in that case, it is the same as i).
v) 'Subsequently, the same light projecting element P41 is turned on, and the output of the light receiving unit R3 at a distant position is selected by the multiplexer 21 and loaded into the CPU 23, and the CPU 23 determines ON / OFF. Other than the threshold value in that case, it is the same as ii).
vi) 'This time, the CPU 23 again takes iv)' and v) 'or the two judgment outputs or the output from CH4.

As can be seen from the above, in the operating procedure of the reflective sensor according to the present embodiment, there are two threshold values of the light receiving unit in each channel.
One is when a corresponding (relative) light projecting element is turned on for each channel. Taking the diffuse reflection type as an example, the light receiving characteristic (distance output characteristic) of the light receiving unit is the characteristic of R1 in FIG. The threshold used at this time corresponds to Vi1 shown in FIG. The window width and the upper and lower limit values thereof also correspond to the corresponding V01, VHref1, and VLref1, respectively.
The other is when the light emitting element at a distant place is turned on, and the light receiving characteristic of the light receiving unit corresponds to the characteristic of R2 in FIG. 5, and the threshold used at this time corresponds to Vi2 shown in FIG. The window width and the upper and lower limit values thereof also correspond to the corresponding V02, VHref2, and VLref2, respectively.
The concept is the same even in the case of the reflector type.

  The positions of the light projecting parts P1 to P4 are different from each other. By driving the plurality of light projecting parts in this way and taking out the received light output, the reliability of the sensor can be further improved.

  As described above, in the present invention, i) a plurality of light output units having different distance output characteristics including peak points of received light amount by disposing light receiving units at a plurality of positions having different distances from the light projecting unit with respect to one light projecting unit. Since the final sensor output is extracted by using the light receiving section, the so-called dead zone disappears. This makes it possible to reliably detect various detected objects regardless of reflectivity, from high reflectivity objects such as white paper, reflectors, and mirrors to low reflectivity black objects and hands. did it.

Also, in picking applications, chattering and the fact that the operator's hand cannot be detected are eliminated, so there is no error in picking up parts on the sensor side, and work efficiency is improved. Similarly, if it is used for counting parts, erroneous counting has been eliminated.
Further, since the reflective type requires only one sensor, wiring man-hours are reduced as compared with the conventional transmission type picking sensor. Originally, picking sensors are used in the processes required to assemble many parts, but they are not used in only one set, and are used in units of several or tens of units depending on the parts shelf. The reduction effect is very large.
In addition, it does not need to be installed on the left and right (or top and bottom) of the parts shelf unlike the transmission type, which contributes to space saving. This reduction in installation costs due to reduced wiring and space meets the requirements for quality stability by preventing mistakes and improving work efficiency in more production sites and industries.

ii) By the way, the conventional reflective multi-optical axis sensor originally includes a plurality of light projecting units and light receiving units. For this reason, the function of the present invention can be realized only by changing the circuit and the CPU program without modifying the structure of the conventional reflective multi-optical axis sensor. At this time, the design cost and design time of the new structure are not required, and it can be said that adopting the present invention is extremely efficient from the viewpoint of cost effectiveness.
Of course, the configuration of the present invention can be applied not only to an existing reflective multi-optical axis sensor but also to a single optical axis reflective sensor.

iii) Conventionally, when the detection distance is short, a diffuse reflection type that directly detects the reflected light from the sensing object is adopted, and when a long detection distance is required, a reflector type sensor is used. The sensor was selected depending on the application.
However, in the case of the present invention, when configuring the sensor system, as long as there is an object that reflects as a background regardless of the detection distance, it may be anything such as a wall or a reflector. Therefore, by adopting the configuration of the present invention, it becomes possible to meet various needs with a single sensor regardless of the detection distance.
Thus, the configuration of the present invention can be used for both diffuse reflection and mirror (reflector) reflection with a single sensor, and has a wide range of application.

  iv) In the case of an application using a reflector, the reflector type sensor conventionally detects the object by blocking the reflected light from the reflector. For example, the object to be detected is a similar reflector such as a mirror or an SUS board. In some cases, it could not be detected. However, according to the present invention, for example, an operator wearing a work clothes sewn with a reflector tape, or an operator pasting a reflector on a helmet, can be reliably detected. Similarly, the present invention can also be applied to a safety multi-optical axis sensor using a reflector (a sensor used for work applications involving danger such as press work).

v) Further, according to the present invention, it is possible to realize a sensor with a sufficiently low probability of false detection and high accuracy without using a polarizing filter. Therefore, according to the present invention, there is no problem with the attenuation of the amount of light (due to the filter) generated when light passes through the polarizing filter, and the detection distance can be made longer than that of the conventional polarizing reflector type sensor. It becomes possible.
In addition, when the reflective sensor is configured as a polarizing reflector using, for example, a polarizing filter and a reflector (polarization type) as described above, the reflected light from a glossy surface reflecting object such as a stainless steel plate is the above. Therefore, there is a problem in that it is impossible in principle to use the reflection type sensor of this configuration not only as a reflector type but also as a diffuse reflection type. As described above, when the polarizing filter is used, not only the problem of attenuation but also the problem that the reflective sensor cannot be shared as the (polarized) reflector type and the diffuse reflection type.
However, by adopting the configuration of the present invention that does not require the use of a polarizing filter, the reflective sensor can be used as either a reflector type or a diffuse reflection type.

vi) The reflection type sensor according to the present invention having such excellent characteristics can be switched from a conventional transmission type sensor as a picking sensor in the manufacturing industry such as an automobile, an electric machine, or a machine tool, or at a low cost. In addition to the expected new installation, it is expected to be applied in new markets.
In other words, in the logistics, transportation, warehouse industry, etc., it is expected to be installed in a mail order or convenience store distribution center or a sorting workshop in a warehouse.
In the parking management system industry, application as a vehicle presence / absence detection sensor in each parking space is expected.
As described above, the reflective sensor according to the present invention is applicable not only to the FA industry but also to various consumer industries.

[Modification]
As described above, the present invention has been described in detail through one embodiment and the like. However, the present invention is not limited to the above configuration, and various modifications can be made.

[Description of modification using mirror as background]
12 and 13 are diagrams showing the arrangement relationship of the optical system and the light density of the light reflected by the mirror when a mirror is used as the background.
The light incident on the mirror has a characteristic of trying to exit with a reflection angle symmetric with respect to the incident angle, and as shown in FIGS. 12 and 13, the light density is in a fixed region compared to that of the reflector shown in FIG. It is uniform.
Here, in the case where the light receiving unit has a two-element configuration of R1 and R2, if it is determined that a significant difference cannot be expected in the distance output characteristics between them, the light receiving unit has a three-element configuration of R1 to R3 as shown in FIG. Also good. The reliability of the sensor can be further improved by taking or of the determination outputs in these three light receiving sections.

FIG. 14 is a diagram showing the distance output characteristics of each light receiving element in the optical system of FIG. 13 when a mirror is used as the background. Now, the mirror is arranged at a distance of 2 m from the sensor, and reflection from the mirror is performed. FIG. 5 is a diagram illustrating an example of a state when the threshold value is adjusted so that the sensor is in an OFF state.
V01, V02, and V03 are the window widths. Vi1, Vi2, and Vi3 are light receiving levels of the light receiving portions R1, R2, and R3 when the mirror W ″ is placed at a position 2 m from the sensor. Vi1, Vi2, and Vi3 correspond to threshold values that serve as a basis for determining that no object to be detected has been inserted (sensor output is in an “OFF” state).

  Looking at the characteristics of the three parties, first, since the positions from the light projecting units are different from the light receiving units R1 to R3, naturally, the position of the peak of the received light amount is shifted. Further, between R1 and R2 and between R2 and R3, as shown in FIG. 13, the difference in the difference in light density is different, and the difference in the difference in the received light output shown in FIG. Appears. Note that, at a distance far from the peak point of the received light amount, all three persons have a characteristic that the received light amount gradually decreases at a substantially constant rate as the distance from the light projecting unit increases.

[Description of other modifications]
For example, as described in the description with reference to FIG. 1, a combination in which two light receiving elements having different separation distances with respect to one light projecting unit are arranged as a light receiving unit is preferable. Accordingly, in order to further improve the accuracy of the sensor, as shown in FIG. 1, a combination in which three or more light receiving elements each having a different separation distance with respect to one light projecting unit may be arranged as a light receiving unit. . By arranging three or more light receiving units, the probability of erroneous detection is further reduced.

The threshold adjustment (sensitivity adjustment) may also be performed at other appropriate timings when the sensor is installed using a sensitivity adjustment switch SW1 as shown in FIG. A control system that performs automatic adjustment when power is supplied may be adopted. In any case, the adjustment of the threshold value is appropriately performed manually or automatically.
Further, regarding sensitivity adjustment, it is possible not only to use the switch SW1, but also to be input from the outside via a cable as appropriate.
Further, the operation indicator lamp M shown in FIGS. 10 and 11 may be omitted. The lens L provided in each of the light projecting and receiving systems shown in FIG. 11 may also be omitted.
In addition, the driving of the light projecting units P1 to P4 described in the embodiments may be sequential or random.
The sensor output “ON” or “OFF” state is also defined for the convenience of the present specification, and may be reversed.

  In addition to the method disclosed in the above embodiment, the four-channel light receiving unit shown in the embodiment is driven in sequence by the pulse operation based on a command from the CPU 23 in addition to the method disclosed in the above embodiment. I) judgment output in the light receiving parts R1 to R4 when the light projecting part P1 is driven or, ii) judgment output in the light receiving parts R1 to R4 when the light projecting part P2 is driven or, iii) A configuration in which the judgment output or in the light receiving parts R1 to R4 when the light projecting part P3 is driven, or iv) the judgment output or in the light receiving parts R1 to R4 when the light projecting part P4 is driven is sequentially taken. It does not matter.

  As described above, the present invention increases or decreases the amount of reflected light from the detected object even when the detected object has the same reflected light as the background and the amount of reflected light from the background (which is a threshold). In both cases, it is apparent that the present invention is a new and useful sensor that can reliably detect both cases and further provides a reflective sensor that can be applied to more applications with higher detection accuracy than before.

It is a figure which shows an example of the method of arrangement | positioning of the light-receiving part with respect to a light projection part. It is a figure which shows an example of the condensing pattern in a some light receiving element. It is a figure which shows the distance output characteristic of each light receiving element in the case of using white paper as a background. It is a figure which shows one structural example of the reflection type sensor provided with the window comparator function. It is a figure which shows the distance output characteristic of each light receiving element at the time of using white paper as a background, Comprising: It is assumed that there exists a background in the distance of 40 cm from a light projection part, and a sensor will be in an OFF state by the reflection from a background here. It is a figure which shows an example of a mode when adjusting a threshold value. It is a figure which shows the distance output characteristic of each light receiving element when the to-be-detected object with a reflectance of 50% is inserted with respect to the background. It is a figure which shows the mode of the arrangement | positioning relationship of an optical system at the time of using a reflector for a background, and the mode of the light density of the light reflected by the reflector. It is a figure which shows the distance output characteristic of each light receiving element in the case of using a reflector as a background. It is a figure which shows the distance output characteristic of each light receiving element when a reflector is used as a background. The reflector is now arranged at a distance of 2 m from the sensor, and the threshold value is adjusted so that the sensor is in the OFF state in reflection from the reflector. It is a figure which shows an example of the mode when it does. It is a figure which shows the external appearance of the reflection type sensor which concerns on a present Example. It is a circuit block diagram of the reflection type sensor which concerns on a present Example. It is a figure which shows the mode of the optical system arrangement | positioning relationship, and the light density of the light reflected by the mirror at the time of using a mirror for a background. It is a figure which shows the mode of the optical system arrangement | positioning relationship, and the light density of the light reflected by the mirror at the time of using a mirror for a background. It is a figure which shows the distance output characteristic of each light receiving element which concerns on the optical system of FIG. 13 at the time of using a mirror as a background, The mirror is arrange | positioned at a distance of 2 m from a sensor now, and a sensor is OFF by the reflection from a mirror. It is a figure which shows an example of a mode when a threshold value is adjusted so that it may be in a state. It is a circuit block diagram of the reflection type sensor which concerns on a prior art example. It is a figure which shows the distance output characteristic in the light-receiving part of the reflection type sensor which concerns on a prior art example.

Explanation of symbols

L lens M operation indicator lamp P1 to P4 light projecting part P11, P21, P31, P41 light projecting element P12, P22, P32, P42 LED drive circuit R, R1 to R4 light receiving part R11, R21, R31, R41 light receiving element R12, R22, R32, R42 Light receiving circuit R13, R23, R33, R43 Comparator SW1 Sensitivity adjustment switch SW1 'Sensitivity adjustment switch storage part W, W' Background 1, 100 Sensor 10, 10 ', 10 "Light emitting / receiving system 20, 20' , 20 '' signal conversion circuit system 21 multiplexer 22 A / D conversion unit 23 CPU
24, 241, 242, 243, 244 and circuit section 25 or circuit section 26 counter 27 scanning circuit 30 output circuit

Claims (2)

A reflective sensor,
A single light projecting unit consists of light receiving units arranged at a plurality of positions at different distances from the light projecting unit, and
Each of the light receiving units has a window comparator function that emits an ON or OFF signal related to the presence or absence of an object to be detected by an increase or decrease in the amount of received light with respect to a threshold value,
Further, the reflection type sensor is configured so as to cover malfunctioning regions that may exist by taking or of at least two determination outputs related to the plurality of light receiving units. A reflective multi-optical axis sensor having a plurality of light projecting units and a plurality of light receiving units,
Each of the light receiving units has a window comparator function that emits an ON or OFF signal related to the presence or absence of an object to be detected by an increase or decrease in the amount of received light with respect to a threshold value,
In addition to the light receiving unit opposed to one light projecting unit, using light receiving units at a plurality of positions with different linear distances from the light projecting unit,
When the light projecting unit sequentially emits light in a pulse operation, it is configured to cover malfunctioning areas that may exist by taking or of at least two determination outputs related to the plurality of light receiving units. A reflective multi-optical axis sensor.

Images