JP2008175742A - Photoelectric sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric sensor capable of stably detecting feature amounts of objects to be detected at high speed. <P>SOLUTION: The photoelectric sensor of this invention detects feature amounts of objects to be detected by receiving reflected light of light projected to the objects to be detected of a region to be detected. Processing in RUN mode of this invention is of a light projection and reception system in which white light is projected to an object to be detected, and its reflected light is received in parallel on red, green, and blue colors. Its measuring time is short. In a conventional system, since red, green, and blue light sources are each sequentially lighted up to sequentially receive and process their reflected light, its measuring time has been long. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a photoelectric sensor that detects a feature amount of a detection target by receiving reflected light or transmitted light of light projected on the detection target in a detection target region.

  The photoelectric sensor projects light such as visible light and infrared light as signal light from the light projecting unit, detects light reflected by the detection target object or light transmitted through the detection target by the light receiving unit, and detects the detection target object. An output signal indicating the feature amount is obtained. In this respect, the photoelectric sensor is used in various fields because it can detect an object in a non-contact manner and can also determine a color. In recent years, a fiber-type photoelectric sensor capable of detecting an object with a minute spot is known (Patent Document 1).

  In general, a red LED or an infrared LED is often used as a light projecting element used in a light projecting unit. However, for example, a sufficient amount of reflected light cannot be obtained depending on the material (reflectance) of the object to be detected. Therefore, a plurality of light projecting element groups in which the light projecting elements used in the light projecting unit are changed to, for example, blue or green are provided. The detection method has been adopted.

  However, if a plurality of light projecting elements are used, the number of parts increases and there is a problem in terms of cost increase.

  Further, in a general reflection type or transmission type photoelectric sensor, the height of the detection target is detected in order to detect the presence or absence of the detection target by comparing the amount of light reflected or transmitted from the detection target with a predetermined threshold. If the distance between the object to be detected and the sensor (fiber tip) fluctuates due to variations, vibrations, or the like, detection may not be possible.

On the other hand, a color identification device is known for detecting a detection target based on the color by projecting three colors of light onto the detection target and receiving the reflected or transmitted light (Patent Document). 2).
JP 2004-101445 A JP 2005-291748 A

  However, in the configuration shown in the publication, LEDs of three colors of red (R), green (G), and blue (B) are used, and two dichroic mirrors are used to guide the light to the optical fiber cable. Yes.

  In this configuration, the distance between the fiber LEDs is increased, and the coupling efficiency is reduced. In addition, the intensity of the RGB signal light becomes non-uniform.

  In the photoelectric sensor using the three-color light source disclosed in the above publication, the light sources of each color are sequentially turned on, and the reflected light or transmitted light is sequentially received and processed. There is also the problem that it takes time. In particular, when the detection object is moving at a high speed, the detection object moves while sequentially projecting light, and thus there is a problem that measurement under the same conditions cannot be performed.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a photoelectric sensor capable of detecting a feature amount of a detection target at high speed and stably.

  A photoelectric sensor according to the present invention is a photoelectric sensor that detects a feature amount of a detection target by receiving light in the detection target region, and includes a white light source that projects white light, and a detection target in the detection target region. A light receiving unit that receives light transmitted through or reflected by the light receiving unit, and a detection unit that detects a feature amount of the detection target based on a light reception result of the light receiving unit. The light receiving units are provided in correspondence with each other to receive a plurality of different wavelengths included in the light that has been projected by white light and transmitted or reflected by the detection target in the detection target region. And a plurality of light receiving elements for receiving light of the corresponding wavelengths in parallel.

  Preferably, the plurality of light receiving elements receive the wavelengths of red, green, and blue light included in the light transmitted or reflected through the detection target in parallel.

  In particular, it further includes a determination unit that determines the detection state of the detection target according to the feature amount of the detection target detected by the detection unit, and the light receiving unit projects white light to the reference reference target that is set at the time of setting. The light that has been transmitted or reflected through the detection object in the detection target area is received, and the detection unit projects white light as a feature amount of the detection target object and transmits or reflects the detection target in the detection target area. The ratio of the received light amount of each of red light, green light and blue light included in the total received light amount of each of the red light, green light and blue light for the reference object calculated by the detection unit at the time of setting is calculated. The reference ratio of the received light amount is compared with the ratio of the respective received light amounts of the red light, the green light, and the blue light for the detection object calculated by the detection unit during the detection operation, and the detection object relative to the reference object is compared. Color approximation Calculating a matching score value indicating the degree, the determination unit determines the detection state of the detection target object based on the calculated degree of matching values.

  In particular, the detection unit compares the total received light amount of a plurality of light receiving elements that receive red light, green light, and blue light with the received light amount that is a predetermined threshold value, and based on the comparison result, features of the detection target Perform the action to detect the quantity.

  In particular, the detection unit detects the feature amount of the detection target when the sum of the amounts of light received by the plurality of light receiving elements is within a range that is greater than or equal to the first threshold and less than the second threshold. Perform the action.

  In particular, at the time of setting, the light receiving unit projects white light onto the reference first and second reference objects and receives or transmits the light transmitted or reflected from the detection object in the detection target region. Are the red light, the green light and the blue light included in the light that is transmitted as a feature quantity of the first and second reference objects at the time of setting and transmitted or reflected by the detection object in the detection target area, respectively. Are received and calculated, and based on the comparison result, a light reception result of at least one of red light, green light, and blue light received by the light receiving unit used in the detection operation is selected.

  In particular, at the time of setting, the detection unit calculates a difference in the amount of received light of the corresponding light. If so, the light reception result corresponding to the detection operation is not selected.

  In particular, the detection unit selects a light reception result of at least one of red light, green light, and blue light received by the light receiving unit used during the detection operation.

  In particular, in the light receiving unit, each of the plurality of light receiving elements corresponds to one of red light, green light, and blue light included in light that is emitted from white light and transmitted or reflected from the detection target in the detection target region. An amplifying unit that generates an electric signal indicating the amount of light and amplifies the electric signal is included, and the amplification factor of the amplifying unit is adjusted so that the signal level of the electric signal becomes a value within a predetermined range.

  A photoelectric sensor according to the present invention is a photoelectric sensor that detects a feature amount of a detection target by receiving reflected light of light projected on the detection target in the detection target region, and the light receiving unit is white It is provided corresponding to each of a plurality of different wavelengths included in the light projected and reflected or reflected by the detection target in the detection target region, each receiving light of the corresponding wavelength and Therefore, it is possible to detect the feature quantity of the detection target at a higher speed and more stably than the conventional method.

  Embodiments of the present invention will be described in detail with reference to the drawings. Note that the same or corresponding parts in the drawings are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is an external perspective view of the photoelectric sensor according to the embodiment of the present invention with the upper cover opened.

  Referring to FIG. 1, photoelectric sensor 1 according to the embodiment of the present invention 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 (GND) core wire 41, a power source (Vcc) core wire 42, a detection output core wire 43, an auxiliary output core wire 44, and a remote input core wire 45. Have

  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. A first display 105, a second display 106, a first operation button (UP) 107, and a second operation button are provided on the upper surface of the casing 101 exposed when the upper cover 102 is opened. A (DOWN) 108, a third operation button (MODE) 109, a first slide operator (SET / RUN) 110, and a second slide operator (L / D) 111 are provided.

  FIG. 2 is a diagram illustrating an enlarged view of the operation / display unit of the photoelectric sensor according to the embodiment of the present invention.

  1 and 2, each of the first display 105 and the second display 106 is composed of a 4-digit 7-segment digital display, each of which includes a 4-digit number, an alphabet, The combination can be arbitrarily displayed.

  The first operation button 107, the second operation button 108, and the third operation button 109 all constitute a momentary type push button switch. As shown in FIG. 2, the first operation button Reference numeral 107 denotes an “UP key”, the second operation button 108 functions as a “DOWN key”, and the third operation button 109 functions as a “MODE key”.

  Each of the first slide operator 110 and the second slide operator 111 constitutes a slide switch. As shown in FIG. 2, the first slide operator 110 is a “SET / RUN changeover switch”. As described above, the second slide operator 111 is configured to function as an “L / D switch”.

  Referring again to FIG. 1, the housing 101 includes a light emitting element for detecting an object and a light receiving element for detecting the object, which are not shown. When the light projecting fiber 2 is firmly inserted into the fiber insertion hole, the end face of the light projecting fiber 2 and the light emitting part of the light emitting element for detection are firmly optically coupled, so that the light generated from the light emitting element for detection is Then, the light is projected from a fiber head (not shown) at the tip thereof to the detection region via the light projecting fiber 2. Similarly, when the light-receiving fiber 3 is firmly inserted into the fiber insertion hole, the end face of the light-receiving fiber 3 and the light-receiving element for detection are optically coupled, and thereby introduced into the fiber from the fiber head of the light-receiving fiber 3 (not shown). The emitted light is guided by the light receiving fiber 3 and reaches the light receiving element for detection. The arrangement of the light emitting element for detection and the light receiving element for detection described above is the same as that employed in the conventional fiber type photoelectric switch of this type.

  Next, the electrical hardware configuration of the photoelectric sensor according to the embodiment of the present invention will be described.

FIG. 3 is a schematic block diagram of the photoelectric sensor according to the embodiment of the present invention.
Referring to FIG. 3, this circuit is mainly composed of a signal processing unit 200 mainly composed of a microprocessor. In addition to the microprocessor, the signal processing unit 200 incorporates a ROM storing a system program, a working RAM necessary for executing the program, and an EEPROM for storing various setting data. The EEPROM stores data set by the manufacturer before shipment from the factory and various data set by the user after shipment from the factory. Such a configuration of the signal processing unit 200 is well known in various documents, and thus detailed description thereof will be omitted.

  On the left side of FIG. 3, a light projecting unit 202 having a light emitting element and a light receiving unit 203 having a light receiving element, which will be described in detail later, are illustrated. The light projecting unit 202 includes a light emitting diode (hereinafter referred to as an LED) 202a which is a light emitting element for detection, and an LED driving unit 202b for driving the LED 202a. On the other hand, the light receiving unit 203 includes a photodiode (hereinafter referred to as PD) 203a which is a light receiving element for detection, and an amplifier unit 203c for amplifying the output of the PD 203a. Note that light projecting unit 202 according to the embodiment of the present invention emits white light. Further, the detection light receiving element PD 203a includes three types of light receiving elements that can receive red light, green light, and blue light, respectively.

  Then, the pulsed light generated from the LED 202a which is a light emitting element for detection by the action of the LED driving unit 202b is guided to the detection region via the light projecting fiber 2. The light introduced into the light receiving fiber 3 by being transmitted or reflected in the detection region arrives at the PD 203a which is a light receiving element for detection via the light receiving fiber 3. The detection light receiving element PD203a receives light by three types of light receiving elements that can receive red light, green light, and blue light, respectively, and photoelectrically converts each color.

  An output signal generated by photoelectric conversion by the PD 203a is amplified by the amplifier unit 203c and then taken into the signal processing unit 200 via an A / D converter (not shown). In addition, since the basic structure of these light projection / reception is also well-known in various literature, the detailed description about this point is abbreviate | omitted.

  The display unit 204 is configured by a display for displaying data generated by various operations in the signal processing unit 200. More specifically, the display unit 204 is more specifically illustrated in FIGS. The first display 105 and the second display 106 described with reference to FIG. 2 are included. Various information is displayed on the first and second indicators 105 and 106 by numerical values, alphabets, combinations thereof, and the like.

  The input unit 205 is for inputting various types of information to the signal processing unit 200. The input unit 205 includes a key input unit 205a and a signal input unit 205b. The key input unit 205a is used by an operator to manually input various data. As described above with reference to FIGS. 1 and 2, the input unit 205a includes 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 included.

  On the other hand, the signal input unit 205b is for inputting a remote input signal via the core wire 45 of the electric cord 4 described above with reference to FIG. 1, and through this signal input unit 205b. A control signal input from the outside coming from the core wire 45 is taken into the signal processing unit 200.

  In this example, only one line is provided for the signal input unit 205b. However, it is naturally possible to input two or more lines, that is, a plurality of lines.

  The output unit 206 is for outputting various output signals generated by the signal processing unit 200 to the core wires 43 and 44 included in the electric cord 4. The output unit 206 includes an output unit 206a for outputting an object detection signal and an output unit 206b for an optional auxiliary output signal. That is, the detection signal for object detection generated by the signal processing unit 200 is sent to the core wire 43 in the electric cord 4 via the output unit 206a.

  Similarly, an arbitrary auxiliary output signal generated by the signal processing unit 200 is sent to the core wire 44 included in the electrical cord 4 via the output unit 206b. The core wires 43 and 44 included in these electric cords 4 are generally connected to an external host device such as a PLC or a PC. Similarly, the core wire 45 included in the electric cord 4 is also connected to an external host device such as a PLC or PC.

  The power supply unit 201 includes a power stabilization device that supplies power to each of the light projecting unit 202, the light receiving unit 203, the display unit 204, the input unit 205, and the output unit 206 shown in FIG. The power supply to the power supply unit 201 is performed through core wires 41 and 42 included in the electric cord 4. In this example, the core wire 41 is connected to GND, and the core wire 42 is connected to Vcc.

  Next, on the premise of the mechanical structure and electrical hardware configuration described above, various functions provided in this photoelectric sensor and the configuration of a system program executed by the signal processing unit 200 to realize them. explain.

  Generally, a photoelectric sensor has a plurality of functions that can be selectively executed (ON / OFF). Various options are available for each of these functions. Selection of these functions (ON / OFF) and selection of options can be performed by setting the photoelectric sensor to the SET mode. The operation of realizing the function set to ON according to a specific option can be performed by setting the photoelectric sensor to the RUN mode.

  The designation of whether the operation mode is the SET mode or the RUN mode is determined by whether the first slide operator 110 is set to the “SET” side or the “RUN” side, as shown in FIG. can do. The second slide operator 111 is for setting the logical polarity of the detection output signal of the photoelectric sensor. If the second slide operator 111 is set to the “L” side, the so-called light-on state is set. When the mode is set to “D”, the dark on mode is set.

  FIG. 4 is a diagram illustrating details of light projecting unit 202 and light receiving unit 203 according to the embodiment of the present invention.

  Referring to FIG. 4, light projecting unit 202 according to the embodiment of the present invention includes LED 202 a and LED driving unit 202 b as described above, and further controls LED driving unit 202 b to control the emission power of the LED. An LED drive adjustment unit 202bg for adjustment is included. The LED drive adjustment unit 202bg receives the monitoring result of the output power from the LED 202a from the signal processing unit 200 by an auto power control process described later, instructs the LED drive unit 202b, and supplies the LED drive unit 202b to the LED 202a. It is assumed that power control of the light emission current is performed.

  Light receiving unit 203 according to the embodiment of the present invention includes PD 203a and amplifier unit 203c as described above. The amplifier unit 203c is configured to amplify an electric signal obtained by photoelectrically converting the received signal light in the red, green, and blue wavelength regions output from the PD 203a, and an amplification adjustment that adjusts an amplification factor of the amplification unit. Including rate.

  In this example, as an example, the amplifier unit 203c includes an amplification unit 203r (also referred to as an R amplification unit) for amplifying an electric signal obtained by photoelectric conversion with respect to signal light in the red wavelength region, and an amplification unit 203c in the green wavelength region. An amplifying unit 203g (also referred to as a G amplifying unit) for amplifying an electric signal photoelectrically converted with respect to the signal light, and an amplifying unit 203b for amplifying the electric signal photoelectrically converted with respect to the signal light in the blue wavelength region. (Also referred to as a B amplification unit) is provided corresponding to each of the amplification units 203r, 203g, and 203b, and an amplification adjustment unit 203rg (also referred to as an R amplification adjustment unit) for adjusting the amplification factor of the corresponding amplification unit. , An amplification adjustment unit 203gg (also referred to as a G amplification adjustment unit) and an amplification adjustment unit 203bg (also referred to as a B amplification adjustment unit).

  The amplification adjustment unit 203rg, the amplification adjustment unit 203gg, and the amplification adjustment unit 203bg each adjust the amplification factor of the corresponding amplification unit in response to an instruction from the signal processing unit 200.

  FIG. 5 is a general flowchart schematically showing the entire system program executed by the CPU of the signal processing unit 200.

Referring to FIG. 5, the execution of this system program is started when the power is turned on.
In the figure, when the process is started, an initial setting process (step 401) is first executed. In this initial setting process (step 401), various initial setting processes necessary before starting a routine process to be described later are executed. In this initial setting process, initialization of various memories, indicator lamps, and control outputs, processing for reading necessary items from the EEPROM included in the signal processing unit 200, data checking, and the like are executed.

  When the execution of the initial setting process (step 401) is completed, the routine is shifted to a routine process. First, the setting state of the first slide operator 110 is referred to (step 402). If the first slide operator 110 is set to the “SET” side (step 402 SET), then the SET mode initial setting process (step 403) is executed. In the SET mode initial setting process (step 403), initialization of the measurement values for the SET mode, initialization of the function number (F) (F = 0), and the like are performed.

  When the execution of the SET mode initial setting process (step 403) is completed, as long as the first slide operator 110 is set to the “SET” side (step 405 YES), the SET for various functions (F) is performed. Mode processing (step 404) is executed. In this state, by appropriately operating the first operation button 107, the second operation button 108, and the third operation button 109, the user turns on various functions (F) prepared for the photoelectric sensor. / OFF setting, and further, individual setting processing for each function (F) can be executed.

  On the other hand, as a result of referring to the setting state of the first slide operator 110, if it is determined that the setting is set to the “RUN” side (step 402RUN), then the RUN mode initial setting process (step 406) is executed. The In this RUN mode initial setting process (step 406), initialization of indicator lamps, control output, threshold values and various RUN mode setting values, and the like are performed.

  When the RUN mode initial setting process (step 406) is completed, the RUN mode process (step 407) is executed as long as the first slide operator 110 is set to the “RUN” side (YES in step 408). In the RUN mode process (step 407), various functions selectively set by the user are realized in addition to the basic operation necessary for the photoelectric sensor. The specific contents of the RUN mode processing will be described later in detail as necessary.

  As described above, the system program executed by the signal processing unit 200 includes an initial setting process (step 401) that is an initial process performed immediately after power-on, and two processes that are routine processes, that is, a SET mode process ( Step 404) and RUN mode processing (Step 407).

FIG. 6 is a flowchart showing the entire SET mode processing.
Referring to FIG. 6, when the process is started, a function-specific display process (step 501) is first executed. In this function-specific display process (step 501), various display processes corresponding to the function number F are executed.

  Subsequently, a key input detection process is executed (step 502), and a wait state is made for the presence or absence of a key input operation on the operation buttons 107 to 109 and the slide operators 110 and 111 shown in FIGS. 1 and 2 (NO in step 503). ).

  In this state, it is determined that there is a key input (step 503 YES), and if a key input sequence corresponding to function switching is confirmed (YES in step 504), each time a function switching command is confirmed, the function number (F) The value is incremented by +1 until the total number of functions is reached (steps 505 and 506 NO), reaches the total number of functions (YES in step 506), is reset again to zero (step 507), and the function (F) is cyclically switched. The

  In this state, when selection regarding function F set at that time is instructed (steps 504 NO, 508 YES), the function-specific execution process is executed, and the process corresponding to function number F is performed (step 509). In the function-specific execution process, for example, the function F is switched according to the key operation of the operation button 107 or 108, and the corresponding process corresponding to the function number F is executed according to the switch.

  In addition, since the function number or the code corresponding to the function F is displayed on the above-described display unit 204 according to the switching of the function F, the user can select what function to the sensor according to the contents displayed by the guidance. It is possible to easily visually check whether the realization means is provided.

An example of a function provided as the SET mode process will be described.
FIG. 7 is a flowchart for explaining the setting of the teaching process provided as the SET mode process.

  Referring to FIG. 7, when processing is started, when the function designated by the user's key operation or an external signal is a one-point teaching function, for example, when the one-point teaching function is selected in step 901 ( In the case of YES), a one-point teaching process is executed (step 902). On the other hand, when the two-point teaching function is selected in step 903 (in the case of YES), a two-point teaching process is executed (step 904).

  Here, “one-point teaching process” means sampling the amount of received light of a reference object (also referred to as a reference object), and setting a threshold value to a lower or higher value by a certain value from the received light amount. It is a function. “Two-point teaching process” means sampling the received light amount of one of the two detection objects, sampling the acquired sampling value and the received light amount of the other detection object, and acquiring the acquired sampling value. This is a function for setting a threshold value in the middle of the value. That is, according to the two-point teaching function, the threshold value = (first sampling value + second sampling value) / 2.

FIG. 8 is a flowchart for explaining the flow of teaching processing.
Referring to FIG. 8, when the process is started, gain adjustment is performed (step 601).

  Specifically, the amplification factor of the signal level of each color photoelectrically converted in the light receiving unit at the time of teaching is adjusted. As for the adjustment of the amplification factor, the signal processing unit 200 applies to the R amplification adjustment unit 203 rg, the G amplification adjustment unit 203 gg, and the B amplification adjustment unit 203 bg based on the amplification factor data previously used for teaching stored in the EEPROM, for example. Instruct and adjust.

  Then, sampling for teaching (teaching sampling acquisition) is performed (step 602). After acquiring the teaching sampling, sampling data for teaching is calculated (step 603).

  Then, it is determined whether or not the number of sampling times exceeds a specified value (for example, 1024 times as an example) (step 604). If the specified value is not exceeded, the process returns to step 602 again, and the above-described operation is repeated until the number of samplings reaches the specified value.

  In step 604, if the number of sampling times exceeds the specified value, the average value of the sampling data for teaching is calculated based on the next acquired sampling data (step 605).

  Then, a received light amount ratio for teaching is calculated. (Step 606). Specifically, the total amount of received light is calculated according to the average value of sampling data for teaching in each of the three colors of light (red, green, and blue), and the average value of the amount of received light of each color with respect to the total sum of the received light amount Ratio, that is, the received light amount ratio.

  Then, a normalization coefficient and a threshold value, which will be described later, are calculated in accordance with the total amount of received light (step 607), and the process ends. The normalization coefficient is a coefficient for normalization so that the total amount of received light of three colors (red, green, and blue), which will be described later, becomes a predetermined value.

  In this teaching process, sampling is performed for each of red, green, and blue colors included in the signal light received by the PD 203a to calculate sampling data.

  Referring to FIG. 7 again, after these teaching processes are completed, it is determined whether or not there is a teaching error (step 905). For example, when there is a teaching error, it can be determined by determining a flag by setting a flag or the like.

  If there is a teaching error (in the case of YES), a message to that effect is displayed to the user, or a teaching error process for adjusting the parameters and executing the teaching again is executed (step 906).

FIG. 9 is a flowchart for explaining teaching error processing.
Referring to FIG. 9, it is first determined whether or not an over error has occurred (step 701). If there is an over error, an over error determination process is executed (step 702). If there is no over error, it is next determined whether or not there is an under error (step 703). If there is an under error, an under error determination process is executed (step 704). The over error determination process and the under error determination process determine whether or not the received light amount obtained by teaching is within a predetermined range, and adjust the value of the received light amount detected based on the determination result. is there. In this regard, as described with reference to FIG. 4, the electrical signals in the respective colors photoelectrically converted by the PD 203 a are amplified by the amplification units of the respective colors and output to the signal processing unit. The signal processing unit 200 determines the amount of received light based on the signal level from the amplification unit provided for each color, but the signal level from the amplification unit may be saturated according to the amplification factor of the amplification unit. is there. Therefore, by the over error determination process, the signal processing unit 200 instructs the amplification adjustment unit to adjust the amplification factor so that the signal level from the amplification unit does not become oversaturated. On the other hand, since the amplification factor is too small, it may not be possible to determine the amount of light received based on the signal level from the amplification unit. The amplification adjustment unit is instructed to adjust the amplification factor so as to be secured.

  Referring to FIG. 7 again, when there is no teaching error (in the case of NO), data such as a threshold value obtained by teaching processing is written into the EEPROM (step 907). The data written in the EEPROM is read out in the later RUN mode and used to calculate the feature quantity of the detection target.

Next, returning to FIG. 5 again, the RUN mode processing will be described.
Prior to introduction into the RUN mode, first, an RUN mode initial setting process is executed (step 406). In this RUN mode initial setting process (step 406), initial setting processes of various flags, counters, registers, and the like necessary for executing the RUN mode are performed. Subsequently, when the RUN mode initial setting process (step 406) is completed, the RUN mode process (step 407) is repeatedly executed as long as the first slide operator 110 is set to the “RUN” side (YES in step 408). Is done.

FIG. 10 is a flowchart for explaining the RUN mode processing.
The entire RUN mode process is roughly divided into a normal process and an interrupt process.

  FIG. 10A is a flowchart for explaining a normal process in the RUN mode process, and FIG. 10B is a flowchart for explaining an interrupt process in the RUN mode process.

  The interrupt process (steps 806 to 808) is executed by timer interrupt every time Tsec (for example, every 100 μsec).

  First, normal processing (steps 801 to 805) will be described with reference to FIG.

  When the process is started, an indicator light control process (step 801) is executed. In this indicator lamp control process (step 801), lighting control of the first and second indicators 105 and 106, which are 7-segment digital indicators, is performed according to the designated display contents.

  Subsequently, an auto power control (hereinafter referred to as APC) process (step 802) is executed. In this APC process (step 802), the monitor light reception amount acquired in a measurement light projecting / receiving process (step 806) described later is monitored, and APC correction is performed at regular intervals. In this example, the APC correction is performed by the power control of the projection current as described above.

  Subsequently, key input detection processing (step 803) is executed. In this key input detection process (step 803), a key input is detected at regular intervals. If an input is detected, a setting is made so that the corresponding process can be executed. Subsequently, an input key corresponding process (step 804) is executed, and various processes corresponding to the detected key input are executed.

  When the input key handling process (step 804) is completed, an external input process (step 805) is executed. Note that these RUN mode processes are processes provided in a general photoelectric sensor, and thus detailed description thereof is omitted.

  Next, with reference to FIG. 10B, an interrupt process executed every time Tsec will be described.

  When the interruption process is started, a light projecting / receiving process (step 806) is first executed. In this light projecting / receiving process (step 806), the LED 201a shown in FIG. 3 is pulse-driven through the light projecting drive unit 201b to generate white light, which is then projected through the light projecting fiber 2. (Not shown) and emitted from the projection head to the detection target area. At the same time, the light reflected or transmitted in the detection target region is introduced into the light receiving fiber 3 from the light receiving head provided at the tip of the light receiving fiber 3 and guided to the PD 202b via the light receiving fiber 3. The signal obtained by photoelectric conversion by the PD 202b is amplified by the amplifier unit 203c, and then the amplified output is taken into the signal processing unit 200 via the A / D converter 202c. Thereby, the received light amount including the feature amount corresponding to the state of the detection target region is acquired by the signal processing unit 200.

  Subsequently, an ON / OFF determination process (step 807) is executed. In this ON / OFF determination process (step 807), a so-called coincidence value calculated based on the amount of light received by the detection target is discriminated based on a preset ON / OFF determination light amount threshold value. By determining the value, the presence / absence of an object in the detection target region is determined. That is, if the target object exists in the detection target region, the determination result is ON, and if it does not exist, the determination result is OFF.

  When the execution of the ON / OFF determination process (step 807) is completed in this way, the output control process (step 808) is subsequently executed, and the detection output signal generated by the signal processing unit 200 is electrically connected via the output unit 209. It is sent out to an object detection signal output core wire 43 included in the code 4. The detection output signal thus output to the core wire 43 is sent to a host device such as a PLC or a PC.

FIG. 11 is a flowchart illustrating the light projecting / receiving process according to the embodiment of the present invention.
Referring to FIG. 11, when the process is started, white light is generated by driving the LED 202a shown in FIG. 3 through the LED driving unit 202b as described above as the light projection process. The light is guided to a light projecting head (not shown) through the light projecting fiber 2 and emitted from the light projecting head to the detection target region (step 1000).

  Then, the light reflected or transmitted in the detection target region is introduced into the light receiving fiber 3 from the light receiving head provided at the tip of the light receiving fiber 3. Then, the light is guided to the PD 203a via the light receiving fiber 3, and is subjected to photoelectric conversion by the PD 203a.

  For the signal obtained by the PD 203a, first, the red received light amount is processed (R received light amount processing) (step 1001). Similarly, the green light reception amount is processed (G light reception amount processing) (step 1002). Similarly, the blue light reception amount is processed (B light reception amount processing) (step 1003). In the following description, the amount of red light received is VR, the amount of green light received is VG, and the amount of blue received light is VB.

  FIG. 12 is a flowchart illustrating ON / OFF determination processing according to the embodiment of the present invention.

  Referring to FIG. 12, when the process is started, first, a matching degree calculation process is executed (step 1100).

FIG. 13 is a flowchart illustrating coincidence degree calculation processing according to the embodiment of the present invention.
Referring to FIG. 13, when the process is started, a change amount with respect to comparison with the reference value is calculated for each color. Specifically, first, a red change amount (change light amount) is calculated (R change amount calculation) (step 1200). Similarly, a green change amount is calculated (G change amount calculation) (step 1201). Further, a blue change amount is calculated (B change amount calculation) (step 1202).

Then, the total change amount of red, green and blue is calculated (step 1203).
Then, a coincidence value is calculated based on the total change amount of red, green, and blue (step 1204). The amount of change and the coincidence value will be described later.

  FIG. 14 is a diagram for explaining a case where the reflected light of the workpiece is received and the amount of received light of each color with respect to the workpiece is normalized.

  Specifically, the case where the received light amount of each color is normalized so that the sum of the received light amounts of three colors of light (red, green, blue) becomes a predetermined value (hereinafter referred to as a normalized maximum value) is shown. ing. In this example, a case where the normalized maximum value is 1000 is shown as an example.

  FIG. 14A is a diagram in which the received light amount of each color is normalized when teaching is performed on the workpiece Wr that is the reference object, and the received light amount ratio for each color is shown.

  FIG. 14B is a diagram in the case where the received light amount of each color when the reflected light is received with respect to the workpiece Wp as the detection target is normalized, and the received light amount ratio for each color is shown. .

  Here, by performing the processing of steps 1200 to 1202 in FIG. 13 described above, the difference between the workpiece Wr and the workpiece Wp is the change amount Δ% R = 150 for red, the change amount Δ% G = 150 for green, and the blue color. A case where the difference Δ% B = 100 is calculated is shown as an example.

  In step 1203, the total change amount of RGB is 400, and the degree of coincidence value is calculated by subtracting the total change amount 400 from the normalized maximum value. In this example, a case where 600 is calculated is shown. That is, the coincidence value corresponds to an index indicating the degree of approximation of the detection target with respect to the color of the reference target.

  Referring to FIG. 12 again, after executing the coincidence degree calculation process in step 1100, the threshold value determination process is executed (step 1101).

  Specifically, here, by determining the coincidence value by comparison with a threshold value, it is determined whether or not the workpiece Wr as the reference object has the same color, and the detection object Can be detected.

  FIG. 15 is a diagram illustrating a comparison between the measurement time of the RUN mode process and the measurement time of the conventional method according to the embodiment of the present invention.

  FIG. 15A shows the flow of processing in the RUN mode according to the embodiment of the present invention. FIG. 15B shows the flow of conventional measurement processing.

  As shown in FIG. 15B, in the conventional method, as described above, the light sources of each color are sequentially turned on in order of red, green, and blue, and the reflected light is sequentially received and processed. Takes very long. Here, since it is necessary to sequentially project red, green, and blue, the ON / OFF determination process and the output control process can be executed only once every three times.

  On the other hand, as shown in FIG. 15 (a), the processing in the RUN mode according to the embodiment of the present invention projects white light onto the detection target and parallelly reflects the reflected light for each of red, green, and blue. This is a light receiving / receiving method. Therefore, the measurement time is extremely shortened and the processing speed is improved.

  In order to shorten the measurement time, it is possible to shorten the measurement time by switching the light source that emits light in order of red, green, and blue, and shortening the projection timing. If it becomes, the heat_generation | fever produced with each light source at that time will become large. Therefore, it is necessary to adjust the timing of the light projection so that the heat generation does not become excessive in the light projecting unit, and this has been one of the factors leading to an increase in the measurement time. This is a method of projecting light using a light source, and there is no need to consider the heat generated by switching, and there is also an effect of excellent stability. Moreover, since it is a single white light source and does not sequentially switch the light source to red, green, and blue, there is also an effect of excellent visibility.

  In particular, when the detection object is moving at high speed, the detection object moves while sequentially projecting light according to the conventional method of FIG. 15B. Therefore, there is a problem that measurement under the same condition is not possible. However, since the method of the present application receives light in parallel, measurement under the same condition is possible and stable detection with high accuracy is possible.

  FIG. 16 is a diagram illustrating the relative light emission intensity with respect to the wavelength region of the white light source that can be used in the embodiment of the present invention.

  The white light source shown here is a general light source that emits white light by combining a blue diode and a fluorescent paint.

  As shown in FIG. 16, there is shown a case where steep emission intensity can be obtained at a certain wavelength (around 450 nm), but since a certain emission intensity can be obtained also in other wavelength areas, a signal in a wide wavelength area is obtained. Light can be emitted.

FIG. 17 is a diagram for explaining light emission intensities of conventional blue, green, and red diodes.
As shown in FIG. 17, in blue, green, and red diodes, it is possible to obtain steep emission intensity only in the corresponding wavelength regions, but sufficient emission intensity is obtained in other wavelength regions. It is not possible. Therefore, a dead zone occurs as shown. Therefore, there is a possibility that sufficient accuracy cannot be obtained when detecting a detection object having a high reflection efficiency with respect to the wavelength of the dead zone.

  In contrast, the present application of the white light it is possible to perform also it is possible to ensure a certain degree of reflection efficiency stable detection for any color because there is no dead zone.

(Modification 1 of embodiment)
FIG. 18 is a flowchart illustrating an interrupt process executed every time Tsec according to the first modification of the embodiment of the present invention.

  Referring to FIG. 18, the difference from the flowchart of FIG. 10B is that the ON / OFF determination process (step 807) is the ratio ON / OFF determination process (step 807a) and the sum ON / OFF determination. The difference is that the processing (step 807b) is replaced.

  Specifically, in the ratio ON / OFF determination process (step 807a), the coincidence value is calculated and compared with the threshold value in the same manner as the ON / OFF determination process (step 807) described in the above embodiment. It is a process to determine. The sum ON / OFF determination process (step 807b) is a process for calculating the sum of the received light amounts of the respective colors and determining the threshold value.

  FIG. 19 is a diagram for explaining the ratio ON / OFF determination process and the sum ON / OFF determination process.

  As shown in FIG. 19A, the vertical axis indicates the sum of received light amounts (RGB sum) of each color (red, green, blue). In addition, the horizontal axis indicates the degree of coincidence value of the amount of received light of each color.

  As described above, the detection target can be detected by comparing and determining the coincidence value calculated by the coincidence degree calculation process and the threshold value (threshold value Cth in this example) with respect to the coincidence value. Is possible.

  Further, a threshold value is provided for the sum of received light amounts (RGB sum) of each color (red, green, blue), and the sum of received light amounts here is not less than threshold value Dth1 and less than threshold value Dth2. It is possible to detect the detection object by comparing and determining whether or not.

  On the other hand, the amount of light is proportional to the square of the distance. That is, the amount of received light has a correlation with the distance to the detection target.

  Therefore, as shown in FIG. 19B, the detection area of the detection target can be specified by appropriately adjusting the threshold values Dth1 and Dth2 of the sum of the received light amounts. That is, it is possible to limit the stable detection region of the detection target, and it is possible to perform more stable detection.

(Modification 2 of embodiment)
In the above-described embodiment, the method of projecting white light and acquiring the red, green, and blue received light amounts included in the reflected light in parallel has been described. In particular, it is necessary to process all three colors. For example, it is possible to selectively process only one color or combine two colors in consideration of characteristics such as the reflection efficiency of the detection target.

  Compared to processing all three colors in parallel, the calculation processing is simplified, the measurement time is shortened, and high-speed processing is possible.

  FIG. 20 is a diagram for explaining a comparison of received light amounts of the detection object WA and the detection object WB in each pattern when two-point teaching is executed.

  As shown in FIG. 20, in the case of the pattern PA, for example, the amounts of light received by the detection object WA and the detection object WB are compared, and the difference can be detected for each color. It is possible to obtain the amount of received light for each color and perform calculation processing. That is, it is possible to select all three colors.

  On the other hand, in the case of the pattern PB, when the amounts of light received by the detection target object WA and the detection target object WB are compared, it is considered difficult to detect the difference for red. It is possible to obtain the amounts of received light of two colors of blue, respectively, and perform calculation processing. That is, it is possible to perform calculation processing using two of the three colors. Thereby, the load on the CPU is reduced and high-speed measurement is possible.

  In the case of the pattern PC, it is considered difficult to detect the difference between red and blue when the received light amounts of the detection object WA and the detection object WB are compared, so the difference can be detected sufficiently. It is also possible to obtain a green light reception amount and perform calculation processing. That is, it is possible to perform calculation processing using one of the three colors. As a result, the CPU load is reduced as described above, and high-speed measurement is possible.

  Even in the present embodiment, since the method of projecting white light, that is, a configuration using a single white light source, there is no need to sequentially switch between red, green, and blue, and the effect of excellent visibility. There is also.

  In this example, the case where the light receiving unit receives red, green, and blue light has been described. However, the light receiving unit is not limited to light of three colors, and more than one type of light is received in parallel. It is also possible to adopt a configuration.

  In this embodiment, a reflective photoelectric sensor, that is, a photoelectric sensor that receives reflected light reflected on a detection target in a detection target region and detects a feature amount of the detection target is described. The present invention is not limited to the photoelectric sensor, and can be similarly applied to a transmissive photoelectric sensor, that is, a photoelectric sensor that receives transmitted light that has passed through a detection target with a detection target force and detects a feature amount of the detection target. That is, in this case, the light guided to the light receiving fiber is not reflected light but transmitted light, and the other systems are the same.

  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.

It is an external appearance perspective view in the state where the upper cover of the photoelectric sensor according to the embodiment of the present invention was opened. It is a figure explaining the enlarged view of the operation and the display part of the photoelectric sensor according to embodiment of this invention. 1 is a schematic block diagram of a photoelectric sensor according to an embodiment of the present invention. It is a figure explaining the detail of the light projection part 202 and the light-receiving part 203 according to embodiment of this invention. 3 is a general flowchart schematically showing an entire system program executed by a CPU of a signal processing unit 200. It is a flowchart figure which shows the whole SET mode process. It is a flowchart explaining the setting of the teaching process provided as a SET mode process. It is a flowchart explaining the flow of teaching processing. It is a flowchart explaining a teaching error process. It is a flowchart figure explaining a RUN mode process. It is a flowchart explaining the light projection / reception process according to embodiment of this invention. It is a flowchart explaining the ON / OFF determination process according to an embodiment of the present invention. It is a flowchart explaining the coincidence degree calculation process according to the embodiment of the present invention. It is a figure explaining the case where the reflected light of a workpiece | work is received and the light reception amount of each color with respect to a workpiece | work is normalized. It is a figure explaining the comparison with the measurement time of the RUN mode process according to embodiment of this invention, and the measurement time of a conventional system. It is a figure explaining the relative light emission intensity with respect to the wavelength range of the white light source which can be used in embodiment of this invention. It is a figure explaining the emitted light intensity of the conventional blue, green, and red diode. It is a flowchart figure explaining the interruption process performed every time Tsec according to the modification 1 of embodiment of this invention. It is a figure explaining ratio ON / OFF determination processing and sum ON / OFF determination processing. It is a figure explaining the comparison of the light reception amount of the detection target object WA in each pattern in the case of performing two-point teaching and the detection target object WB.

Explanation of symbols

  1 photoelectric sensor, 2 light emitting fiber, 3 light receiving fiber, 4 electric cord, 41 GND core wire, 42 Vcc core wire, 43 detection output signal core wire, 44 auxiliary output signal core wire, 45 for control signal Core wire, 101 housing, 102 transparent cover, 103 clamp lever, 104 DIN rail fitting groove, 105 first indicator, 106 second indicator, 107 first operation button, 108 second operation button, 109 3rd operation button, 110 1st slide operation element, 111 2nd slide operation element, 200 Signal processing part, 201 Power supply part, 202 Light projection part, 202a LED, 202b Light projection drive part, 203 Light reception part, 203a PD, 203b amplifier unit, 204 display unit, 205 input unit, 205a key input unit, 205b signal input unit, 206 Power unit, an output unit for 206a detection signal, an output unit for 206b auxiliary output signal.

Claims (9)

A photoelectric sensor that detects a feature amount of a detection target by receiving light of a detection target region,
A white light source that projects white light;
A light receiving unit that receives light transmitted or reflected from the detection target in the detection target region;
A detection unit that detects a feature amount of the detection object based on a light reception result of the light receiving unit;
The light receiving unit is provided correspondingly to receive a plurality of different wavelengths included in the light that is projected from the white light and transmitted or reflected from the detection target in the detection target region. A photoelectric sensor including a plurality of light receiving elements that receive light of a wavelength to be received and receive light of each corresponding wavelength in parallel.   The photoelectric sensor according to claim 1, wherein the plurality of light receiving elements receive, in parallel, wavelengths of red, green, and blue light included in light transmitted or reflected from the detection target. A determination unit that determines a detection state of the detection target according to a feature amount of the detection target detected by the detection unit;
The light receiving unit, when set, receives the light transmitted or reflected by the detection target region in the detection target region by projecting the white light to a reference target object serving as a reference,
The detection unit projects the white light as a feature quantity of the detection target object, and includes red light, green light, and green light included in a total amount of received light transmitted or reflected from the detection target area of the detection target area. The ratio of the amount of received light of each blue light is calculated, the reference ratio of the amount of received light of each of the red light, the green light and the blue light related to the reference object calculated by the detection unit at the time of the setting, and the detection operation The ratio of the amount of received light of each of the red light, green light and blue light related to the detection target calculated by the detection unit is compared to indicate the degree of approximation of the color of the detection target relative to the reference target Calculate the match value,
The photoelectric sensor according to claim 2, wherein the determination unit determines the detection state of the detection target based on the calculated coincidence value.   The detection unit compares a total received light amount of the plurality of light receiving elements that receive the red light, green light, and blue light with a received light amount that is a predetermined threshold, and based on a comparison result, the detection target object The photoelectric sensor of Claim 2 which performs the operation | movement which detects the feature-value of this.   The detection unit calculates the feature amount of the detection target when the sum of received light amounts of the plurality of light receiving elements is within a range of a first threshold value or more and less than a second threshold value that is greater than the first threshold value. The photoelectric sensor of Claim 4 which performs the operation | movement to detect. The light receiving unit is configured to project the white light to the first and second reference objects serving as a reference and receive light transmitted or reflected from the detection object in the detection target region at the time of setting,
The detection unit emits the white light as a feature amount of the first and second reference objects at the time of setting, and includes red light included in light transmitted or reflected from the detection object in the detection target region The light receiving amounts of green light and blue light are calculated and compared, and at least one of the red light, green light, and blue light received by the light receiving unit used in the detection operation based on the comparison result The photoelectric sensor according to claim 2, wherein a light reception result of two lights is selected.   The detection unit calculates a difference in received light amount of the corresponding light at the time of the setting, and if the calculation result is equal to or greater than a predetermined threshold, selects the corresponding light reception result at the time of the detection operation, The photoelectric sensor according to claim 6, wherein if it is less than a threshold value, a light reception result of the corresponding light is not selected during the detection operation.   The photoelectric sensor according to claim 2, wherein the detection unit selects a light reception result of at least one of the red light, the green light, and the blue light received by the light receiving unit used during a detection operation. In the light receiving unit, each of the plurality of light receiving elements emits the white light and transmits the red light, the green light, and the blue light included in the light that is transmitted through or reflected from the detection target region. Generate an electrical signal indicating the amount of light
An amplifying unit for amplifying the electric signal;
The photoelectric sensor according to claim 2, wherein an amplification factor of the amplifying unit is adjusted so that a signal level of the electric signal becomes a value within a predetermined range.

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