JP2007003221A - Inspection method of carved letter and inspection device therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection method of a carved letter capable of certainly detecting a carved letter regardless of its region in a case that the carved letter is inspected by detecting the light reflected from an inspection target, and also to provide an inspection device. <P>SOLUTION: Circular polarized light rotated in its azimuth with the advance of the light emitted from a floodlight projection means 6 is thrown on a frame, in which the letter of a car body number is carved, to be reflected from the frame 1 and the circular polarized light, which is regularly reflected from a part including no letters carved and held to a polarized state, in the reflected light is cut off by a polarizing plate 15. The greater part of the light, which is reflected from a part of which the surface is modified by carving the letter to be brought to a partially polarized state, is transmitted through the polarizing plate 15 and the intensity of the transmitted light is measured to recognize the carved letter based on the measured intensity of the transmitted light. The recognized letter is compared with the letter set to a control unit 9 to inspect that the set letter is accurately carved in the frame 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a stamped character inspection method and an inspection apparatus for inspecting that a predetermined character is accurately stamped on an inspection object.

  The body number is stamped on the frame of the body of the automobile, for example, at a position below the front wiper in the engine room or below the driver seed. In an automobile assembly factory, as shown in FIG. 8, an articulated robot 102 having a cutting machine 101 mounted on the tip 100 is installed. The stamping machine 101 and the articulated robot 102 are remotely controlled by a control device (not shown) provided on the operator side, and the vehicle body number is imprinted on the frame 103 based on the vehicle body number set in the control device. It is supposed to be.

  When the vehicle body number is engraved on the frame 103, an inspection is performed by the operator to confirm that the characters of the vehicle body number set in the control device are accurately imprinted. Conventionally, for example, as shown in FIG. 9, when a car body number is engraved on the frame 103 by the stamping machine 101, a roll-shaped paper tape 104 is sandwiched between the stamping machine 101 and the frame 103. The car body number is also engraved on the paper tape 104 at the time of engraving, and the character of the car body number imprinted on the paper tape 104 is confirmed. The characters of the vehicle body numbers of the plurality of frames 103 are engraved on one roll-shaped paper tape 104. By storing the paper tape 104, the vehicle number of the vehicle frames of the plurality of frames 103 manufactured is stored. Management was done.

  However, such a paper tape type inspection method requires a dedicated device for winding up the paper tape 104 and a dedicated device for inspecting the characters of the vehicle number engraved on the paper tape 104, and these devices are expensive. However, there is a problem that the maintenance is costly. In addition, replacement work of the paper tape 104 is necessary, which causes a problem that work efficiency is lowered.

  Therefore, recently, in place of the paper tape type inspected character inspection method, an optical type inspected character inspection method has been introduced. FIG. 10 shows an outline of a method for inspecting stamped characters by an optical method. In this method of inspecting a stamped character by an optical method, first, as light, for example, light emitted from a fluorescent lamp 105 is irradiated and reflected in the vicinity of a character of a car body number stamped on the frame 103, and this reflected light is reflected by a lens 106. Condensate. Then, the collected light is received by each light receiving element of the area sensor 107 in which a plurality of light receiving elements are arranged in a plane, and the intensity of the light received by each light receiving element is measured.

Next, an inspection unit (not shown) performs binarization processing based on the measured light intensity, generates a character image for recognizing the character of the vehicle body number, and stores it as character image data. Then, based on the character image data, character recognition processing is performed to detect the character with the car body number stamped. Next, the character of the detected vehicle number is compared with the character of the vehicle number set in the control device, and an inspection is performed to confirm that they match. These character image data and the inspection result are displayed on a monitor (not shown). In this way, a test is performed to confirm that the character set in the control device as a predetermined character is correctly stamped on the frame 103.
Japanese Patent Laid-Open No. 2002-5843

  However, in this method for inspecting a stamped character by an optical method, the reflected light from the frame 103 is too strong or too weak depending on the amount of light radiated from the fluorescent lamp 105 to the frame 103. In some cases, it was impossible to accurately distinguish between the carved part and the carton number. In addition, during the assembly process of the frame 103, an oil film or water may adhere to the surface of the frame 103. Such oil film or water causes fluctuations in the intensity of reflected light from the frame 103, and the vehicle number In some cases, the accuracy of character recognition was reduced. Furthermore, depending on the shape of the frame 103, there may be a concavo-convex surface in the vicinity of the stamped character, and the recognition accuracy of the character of the vehicle body number may be lowered due to fluctuations in the intensity of reflected light on the concavo-convex surface. As described above, the conventional optically inspected character inspection method has a drawback that the accuracy of recognizing the character inscribed on the inspection object is low.

  Therefore, the applicant of the present application first applied for the one of Patent Document 1 paying attention to the fact that the polarization state of the light reflected by the engraved letters changes. This application was made by paying attention to the fact that linearly polarized light is irradiated on the stamped character, and its polarization state changes with the stamped character to become a non-polarized state, and the light of the non-polarized state changed with the stamped character is detected. By doing so, the stamped character is detected.

  However, as a result of detecting the stamped character with an actual inspection device, the stamped character is caused by the light reflection when the S-polarized light component that is orthogonal to the incident surface and the P-polarized light component in the incident surface are reflected by the stamped material. It has been found that the detection of is uncertain. In other words, when the linearly polarized light is reflected by the engraved letter, if the linearly polarized light is reflected because of the S-polarized light, it is specularly reflected and the polarization state of the S-polarized light is maintained. It becomes difficult. Further, when the linearly polarized light is reflected due to the P-polarized light and the Brewster angle is obtained, the reflectivity is greatly reduced, so that it is difficult to detect the portion where the P-polarized light is reflected at the Brewster angle.

  Specifically, when the polarization direction of the linearly polarized light is the direction A shown in FIG. 11, the portion where the linearly polarized light becomes S-polarized with respect to the stamped character (“O” character in the figure) (B in the figure). ) And a portion (indicated by C in the figure) that becomes P-polarized light is greatly attenuated, making it difficult to detect a stamped character.

  The present invention has been made in view of the above-described circumstances, and therefore, the object thereof is to inspect a stamped character by detecting light that has been irradiated with light and reflected to change the polarization state. Another object of the present invention is to provide an inspection method and an inspection device for a stamped character that can be reliably detected regardless of the portion of the stamped character.

  The inspected character inspection method according to claim 1, wherein the character imprinted on the inspection object is reflected by irradiating the circularly polarized light or the elliptically polarized light whose azimuth angle rotates with the progress of light, and the character out of the reflected light. A portion that is changed from the polarization state of the irradiated circularly polarized light or elliptically polarized light by blocking the circularly polarized light or elliptically polarized light whose polarization state is maintained by regular reflection at the non-marked portion of Transmit most of the polarized light, measure the intensity of the transmitted light, recognize the stamped character based on the measured transmitted light intensity, and recognize the recognized character and a predetermined It is characterized by inspecting that the predetermined character is accurately imprinted on the inspection object by comparison with the character.

  3. The inspected character inspection apparatus according to claim 2, wherein the character imprinted on the inspection object is irradiated with circularly polarized light or elliptically polarized light whose azimuth angle is rotated as light travels, and reflected, and the inspection object The circularly polarized light or the elliptically polarized light whose polarization state is maintained is blocked by regular reflection at the non-marked portion of the character among the reflected light reflected at, and the circularly polarized light irradiated by irregularly reflecting at the stamped portion of the character. Alternatively, a measuring means for transmitting most of the light in the partially polarized state changed from the polarization state of elliptically polarized light and measuring the intensity of the transmitted light, and the marking based on the intensity of the transmitted light measured by the measuring means An inspection means for recognizing the recognized character and inspecting that the predetermined character is accurately imprinted on the inspection object by comparing the recognized character with the predetermined character. Characteristic To.

  The inspected character inspection apparatus according to claim 3, wherein the light projecting means includes a coherence light source that emits linearly polarized light, a collimator lens that makes light emitted from the coherence light source substantially parallel light, and linearly polarized light from the collimator lens. And a phase difference plate that converts circularly polarized light or elliptically polarized light whose azimuth angle rotates with the progress of light, and the measuring means regularly reflects the non-engraved part of the letter of the reflected light from the inspection object. A phase difference plate that converts circularly or elliptically polarized light whose polarization state is maintained by the linearly polarized light, a polarizing plate that blocks the linearly polarized light converted by the phase difference plate, and light that passes through the polarizing plate is collected. And a light receiving unit for measuring the intensity of light transmitted through the lens.

  The inspected character inspection method according to claim 4, wherein the character imprinted on the inspection object is reflected by irradiating the circularly polarized light or the elliptically polarized light whose azimuth angle rotates with the progress of light, and the character out of the reflected light. The intensity ratio of linearly polarized light between the first polarized light component and the second polarized light component of circularly polarized light or elliptically polarized light whose polarization state is maintained by regular reflection at the non-marked portion of 1 is 1, and at the stamped portion of the character By reflecting, the intensity ratio of the linearly polarized light of the first polarization component and the second polarization component of the light in the partial polarization state changed from the irradiation state of the circularly polarized light or the elliptically polarized light is different from 1. The reflected light is separated into linearly polarized light of the first polarized light component and the second polarized light component, the intensity of the linearly polarized light of each of the separated polarized light components is measured, and the linearly polarized light of each of the measured polarized light components is measured. Before stamped, based on strength Recognizes characters, by comparison with the recognized the character and a predetermined character, the predetermined character is characterized by inspecting that is stamped exactly the inspection target.

  The inspected character inspection apparatus according to claim 5, wherein the character imprinted on the inspection object is irradiated with circularly polarized light or elliptically polarized light whose azimuth angle is rotated as light travels, and reflected, and the inspection object Of the reflected light reflected at, the intensity ratio of the light of the first polarization component and the second polarization component of circularly polarized light or elliptically polarized light whose polarization state is maintained by regular reflection at the non-marked portion of the character is: The intensity ratio of the light of the first polarization component and the second polarization component of the partially polarized light changed from the polarized state of the circularly polarized light or elliptically polarized light irradiated by being reflected at the engraved portion of the character. Is different from 1, and separates the reflected light into linearly polarized light of the first polarization component and the second polarization component, and measuring means for measuring the intensity of the linearly polarized light of each of the separated polarization components, Each polarization component measured by the measurement means Based on the intensity of the linearly polarized light, the imprinted character is recognized, and by comparing the recognized character with the predetermined character, it is confirmed that the predetermined character is accurately imprinted on the inspection object. And inspecting means for inspecting.

  The inspected character inspection apparatus according to claim 6, wherein the light projecting means includes a coherence light source that emits linearly polarized light, a collimator lens that makes light emitted from the coherence light source substantially parallel, and linearly polarized light from the collimator lens. A phase difference plate that converts circularly polarized light or elliptically polarized light whose azimuth angle rotates as the light travels, and the measuring means collects the reflected light from the object to be inspected and the light transmitted through this lens. A beam splitter that separates the P-polarized component and the S-polarized component into linearly polarized light, and a light receiving unit that measures the intensity of the linearly polarized light of the P-polarized component and the S-polarized component that pass through the beam splitter. Of the transmitted light of the lens that collects the reflected light, the intensity ratio of the linearly polarized light of the P-polarized component and the S-polarized component of the light that is regularly reflected by the non-marked portion of the character is 1, The polarization azimuth angle of the P-polarized component and the S-polarized component of the beam splitter is adjusted so that the intensity ratio of the linearly polarized light of the P-polarized component and the S-polarized component of the light irregularly reflected at the stamped portion is different from 1. Features.

  The inspected character inspection apparatus according to claim 7, wherein the light projecting means and the measuring means are mounted on the measurement position control means so as to measure the reflected light from the stamped character while moving in a predetermined direction at a predetermined speed. It is comprised by these.

  The inspected character inspection apparatus according to claim 8 is characterized in that the inspection means includes data storage means for storing the recognized characters.

  According to the first or second aspect of the invention, the reflected light from the object to be inspected is regularly reflected at the non-marked portion of the character, thereby blocking the light whose polarization state is maintained and reflected at the stamped portion of the character. By measuring the intensity of the light transmitted through most of the partially polarized light, it is possible to accurately distinguish between the stamped portion and the non-printed portion of the character of the inspection object. Therefore, the accuracy of inspecting that the predetermined character is accurately stamped on the inspection object can be improved. Moreover, since the polarization state of the light reflected by the marking portion of the inspection object is not affected by the azimuth angle, it is possible to accurately detect the characters stamped on the inspection object and maintain a high inspection accuracy. be able to.

  According to the third aspect of the present invention, by measuring the intensity of the light transmitted through the polarizing plate, it is possible to accurately distinguish the stamped portion and the non-marked portion of the character of the inspection object. This simplifies the configuration of the inspection device and reduces the number of parts, thereby reducing the manufacturing cost of the inspection device for engraved characters.

  According to the fourth or fifth aspect of the invention, the first polarization component of each of the light reflected from the inspection object that is regularly reflected by the non-marked portion of the character and the light that is reflected by the stamped portion of the character. Since the reflected light is separated into the light of the first polarization component and the second polarization component so that the intensity ratio of the linearly polarized light of the second polarization component changes, the first polarization component and the second polarization component are separated. By measuring the intensity of the linearly polarized light of the component, it is possible to accurately distinguish the stamped portion and the non-marked portion of the character of the inspection object.

  According to the sixth aspect of the present invention, by obtaining the intensity ratio of the linearly polarized light of the P-polarized component and the S-polarized component separated by the beam splitter, the character marking portion and the non-marking portion of the inspection object can be accurately determined. Can be classified.

  According to the seventh aspect of the invention, for example, the light projecting means and the measuring means are accommodated in one sensor head, and the reflected light from the inspection object is measured while moving the sensor head by the measurement position control means. Thus, the light projecting means and the measuring means can be brought close to the inspection object to inspect the characters imprinted on the inspection object, thereby making the recognition of the imprinted characters accurate, The accuracy of inspecting that the characters are accurately stamped on the inspection object can be increased. Moreover, it is not necessary to increase the amount of light emitted from the light projecting means by bringing the light projecting means and the measuring means closer to the inspection object. Further, since the sensor head (light projecting means and measuring means) may be moved according to the number of predetermined characters, it is possible to inspect the stamped characters efficiently.

  According to the invention described in claim 8, it is possible to easily manage the characters imprinted on the plurality of inspection objects simply by providing the data storage means. For example, a special device for managing the imprinted characters There is no need for a management place.

(First embodiment)
A first embodiment of the present invention will be described below with reference to FIGS.
First, FIG. 2 shows an outline of installation of a stamping machine 2 for marking a vehicle body number on a frame 1 of a body of an automobile, and a stamped character inspection device 3 (described later) for inspecting a character of a vehicle body number stamped on the frame 1. Is shown. In an automobile factory, an articulated robot 5 capable of controlling the position of the tip 4 is installed at the assembly site of the frame 1. The tip end 4 is equipped with a stamping machine 2, a light projecting means 6, a measuring means 7 and a precision stage base 8a which will be described later. A control device 9 that controls the operation of the articulated robot 5 and a personal computer 19 that will be described later are installed in the vicinity of the place where the articulated robot 5 is installed.

  The stamping machine 2 and the articulated robot 5 are controlled remotely by a control device 9 (see FIG. 1) provided on the operator side, and perform a predetermined operation according to a program input to the control device 9. It has become. For example, when a program for imprinting the vehicle body number on the frame 1 is executed, the articulated robot 5 can set the character of the vehicle body number imprinted on the frame 1 in the control device 9 to The tip 4 is moved to a position below the part where the front wiper of the engine room is mounted, and the stamping machine 2 stamps the character of the set vehicle number at this position of the frame 1.

Next, FIG. 1 shows a configuration of the inspection apparatus 3.
The sensor head 10 is formed in a rectangular parallelepiped shape with a metal plate. A rectangular opening 11 is formed on one side wall surface of the sensor head 10, and a colored glass plate 12 capable of transmitting irradiated light is attached to the opening 11. Further, the light projecting means 6 and the measuring means 7 are mounted in the sensor head 10.

  The light projecting means 6 includes a semiconductor laser 13 that is a coherence light source, a lens 14 that is installed in the vicinity of the emission end of the semiconductor laser 13, and a phase difference plate (¼ wavelength plate) 6a. The laser light emitted from the semiconductor laser 13 is linearly polarized light whose polarization azimuth is aligned to a predetermined azimuth, and this laser light is incident on the phase difference plate 6a in a state of being made almost parallel by the lens 14. The phase difference plate 6a is installed so that the azimuth angle where the linearly polarized light that has passed through the lens 14 is incident is 45 degrees between the high-speed axis and the low-speed axis (tilted by 90 degrees with respect to the high-speed axis). Yes. As a result, the linearly polarized light is converted into circularly polarized light (see FIG. 5) whose azimuth angle rotates as the light travels when passing through the phase difference plate 6a. When the distance from the frame 1 reaches a predetermined distance, a predetermined area of the frame 1 (around the engraved characters) is irradiated.

  Since the frame 1 is galvanized, the surface of the frame 1 is uniformly smooth. Therefore, the light reflected from the light projecting means 6 when the laser beam is applied to the frame 1 is circularly polarized light whose polarization state is maintained and whose polarization azimuth angle rotates as the light travels. However, the portion of the frame 1 on which the characters are engraved has an extremely concave portion at the time of engraving, and further, fine scratches are generated on the surface. Therefore, the shape and surface of this portion are modified. For this reason, when laser light is irradiated from the light projecting means 6 to the portion marked with this character, the laser light is changed from the circularly polarized state and scattered due to the concave shape and fine scratches generated on the surface. While diffusely reflecting. Therefore, the light reflected from the portion marked with this letter becomes light having an irregular polarization azimuth including light in a partial circular polarization state changed from the circular polarization state, that is, light in a partial polarization state. Accordingly, when laser light is irradiated from the light projecting means 6 around the character marked on the frame 1, the partially polarized light is reflected from the portion where the character is stamped (the stamped portion), and the character is stamped. Circularly polarized light is reflected from an unmarked portion (non-marked portion).

  The measuring means 7 is configured as follows. The phase difference plate 7a is arranged so that the polarization direction of the polarizing plate 15 is 45 ° between the high speed axis and the low speed axis of the phase difference plate 6a, and the circularly polarized light regularly reflected by the frame 1 is the phase difference plate. When passing through 15a, it is converted into linearly polarized light and passes through the polarizing plate 15 in this state. Since the polarizing plate 15 is at an angle of 90 ° with respect to the linear direction coming out of the retardation plate, the light transmitted through the polarizing plate 15 is only partially polarized light that is irregularly reflected at the stamped portion of the character, and the non-character of the character. Circularly polarized light that is regularly reflected at the stamped portion is blocked. In addition, even if the light quantity fluctuation of the laser beam, the adhesion of oil film or water to the surface of the frame 1 and the uneven shape of the frame 1 occur, the circularly polarized state that is regularly reflected by the non-marked portion of the character does not change. Circularly polarized light that is regularly reflected at the non-engraved portion of the character is blocked.

  In the vicinity of the polarizing plate 15, a lens 16 for collecting the light transmitted through the polarizing plate 15 is installed. A line sensor 17 is installed in the vicinity of the lens 16, and the light condensed by the lens 16 is irradiated. The line sensor 17 is configured by arranging a predetermined number of light receiving elements (not shown) in a straight line, and the light received by each light receiving element has a predetermined voltage amplitude corresponding to the intensity of the light. It is converted into an analog signal and is sequentially output for each light receiving element. This analog signal is output to an amplifier 18 installed in the sensor head 10. The amplifier 18 amplifies the analog signal to a predetermined voltage amplitude and outputs it to a personal computer 19 as an inspection means via a signal line (not shown) passing through the arm of the articulated robot 5 (see FIG. 2). The phase difference plate 7a, the polarizing plate 15, the lens 16, the line sensor 17 and the amplifier 18 constitute the measuring means 7.

  FIG. 3 shows the configuration of the measurement position control means 8. The pedestal 20 is formed in a concave shape by a steel plate. Circular holes are formed in the central lower portions of the opposing side wall surfaces 21a and 22a of the convex portions 21 and 22 at both ends of the base 20, and the upper surface of the central concave portion 23 passes through these holes. A screw shaft 24 is mounted above 23a. Further, a screw receiver having a ball (not shown) is attached to the bottom surface of the stage 25 formed in a rectangular parallelepiped shape, and the screw shaft 24 is attached so as to engage with the screw receiver. It is mounted on the upper part of the shaft 24. The screw shaft 24 and the stage 25 constitute a ball screw mechanism. By rotating the screw shaft 24, the stage 25 moves in the direction of the convex portions 21 or 22 at both ends of the pedestal 20.

  Further, a convex portion 21 on one end of the pedestal 20 incorporates a stepping motor and power transmission means (not shown) for rotating the screw shaft 24, and commands from a controller 26 (see FIG. 1) described later. Thus, the rotation of the screw shaft 24 is controlled, and the position of the stage 25 is controlled.

  Further, an L-shaped support member 27 is attached to the stage 25, and the sensor head 10 is attached to the upper portion of the support member 27. The pedestal 20, the screw shaft 24, the stage 25, the support member 27, a stepping motor (not shown) and power transmission means constitute a precision stage base 8a. The light projecting means 6, the measuring means 7 and the precision stage base 8a are attached to the tip 4 of the articulated robot 5, as shown in FIG.

  Further, as shown in FIG. 1, a controller 26 and a driver 28 for controlling the position of the stage 25 are installed on the personal computer 19 side, and the personal computer 19 and the controller 26 communicate speed control signals. The drive signal generated by the controller 26 is output to the driver 28. The drive signal output from the driver 28 is connected to a stepping motor provided in the pedestal 20 via a signal line (not shown) passing through the arm of the articulated robot 5 (see FIG. 2). The precision stage base 8a, the controller 26 and the driver 28 constitute the measurement position control means 8.

  The power sources of the light projecting means 6, the measuring means 7 and the precision stage base 8a are generated by a control power supply circuit (not shown), and the generated power supply passes through the arm of the articulated robot 5 (see FIG. 2). The power is supplied to the light projecting means 6, the measuring means 7, and the precision stage base 8a through the power line that is not.

  The personal computer 19 is installed with an inspected character inspection program, and is connected to a monitor 29 for setting inspection conditions to be described later and displaying inspection results. The personal computer 19 is connected to the control device 9 through a signal line so that two-way communication is performed. Furthermore, a hard disk (not shown) built in the personal computer 19 is used as data storage means. The light projecting means 6, the measuring means 7, the measuring position control means 8, and the personal computer 19 constitute the inspection device 3.

Next, the operation of the inspection apparatus 3 will be described with reference to FIG.
FIG. 4 shows a flowchart of the inspection program installed in the personal computer 19. When the inspection program is started, inspection conditions are first set in step S1. As inspection conditions, the moving speed of the stage 25 of the precision stage stage 8a and the measurement interval at the time of line scanning measurement described later are set. If no setting is made, the default value is used. When the setting of the inspection condition is completed, the process proceeds to step S2.

  In step S2, a request for, for example, an ASCII code (hereinafter, this ASCII code is referred to as character information) of the character of the vehicle body number set in the control device 9 is made to the control device 9, and control is performed in response thereto. The character information transmitted from the device 9 is received and recorded in a memory (not shown) provided in the personal computer 19. When this communication is completed, the process proceeds to step S3.

  In step S <b> 3, the controller 9 is requested to notify the controller 9 of the completion of marking on the frame 1 of the character set in the controller 9. In response to this request, the control device 9 transmits a signal notifying completion of marking if the marking has already been completed. If the marking has not been completed, the marking is completed when the request has been completed. Is transmitted. When the personal computer 19 receives a signal for notifying the completion of the marking from the control device 9, it determines that the inspection of the stamped character may be started, and proceeds to step S4.

  In step S <b> 4, a signal for notifying the control device 9 of the start of inspection of the stamped character is transmitted. When the control device 9 receives the signal for notifying the start of the inspection, the light projecting means 6 and the measuring means 7 attached to the tip portion 4 are arranged at a position for measuring the first character of the stamped character. In addition, drive control of the articulated robot 5 is performed. When the arrangement is completed, the control device 9 transmits a signal notifying completion of arrangement. In the personal computer 19, the line scanning measurement is started by receiving a signal notifying completion of arrangement from the control device 9.

  In the line scanning measurement, first, a speed control signal is generated based on the moving speed of the stage 25 set in step S 1, and this speed control signal is output to the controller 26. The controller 26 generates a drive signal based on this speed control signal, and this drive signal is output to the precision stage base 8a via the driver 28. In the precision stage base 8a, the stage 25 moves at a speed based on this speed control signal.

  The line sensor 17 measures the reflected light from the frame 1 based on the measurement interval set in step S1 while the stage 25 moves at a predetermined speed. By this measurement, the light detected by each light receiving element of the line sensor 17 is converted into an analog signal. The analog signal is output at predetermined time intervals sequentially from one end of all the light receiving elements arranged in a straight line, amplified to a predetermined voltage amplitude by the amplifier 18, and digital signal by A / D conversion by the personal computer 19. And sequentially recorded in a memory (not shown) in the personal computer 19. In this way, all digital signals corresponding to the light detected by all the light receiving elements of the line sensor 17 are recorded.

  Thus, the line scanning measurement is performed by measuring the reflected light from the frame 1 at the set measurement interval while moving the stage 25 at the set moving speed. This line scanning measurement is performed until the reflected light measurement of all the stamped character portions is completed. When the line scan measurement is completed, the process proceeds to step S5.

  In step S5, binarization processing is performed on all digital signals recorded in the memory. In this binarization processing, for example, the value of the digital signal is compared with a predetermined threshold value, and when the digital signal is equal to or larger than the predetermined threshold value, it is set to “1”. When the value is smaller than the predetermined threshold value, it is set to “0”. As a result, it is clearly distinguished whether the all digital signal corresponds to the light specularly reflected at the non-marked portion of the character or the light corresponding to the light irregularly reflected at the stamped portion of the character. That is, the digital signal generated by the binarization process represents the character image of the measured vehicle body number. Hereinafter, this digital signal is referred to as character image data. When this binarization processing is completed, the process proceeds to step S6.

In step S6, the character image data is recorded on the hard disk. Further, the character of the measured vehicle body number is displayed on the monitor 29 based on the character image data. Then, the process proceeds to step S7.
In step S7, the character of the vehicle body number measured by the character recognition process is detected based on the character image data, and the ASCII code corresponding to the character is extracted. Then, the process proceeds to step S8.

  In step S8, the ASCII code of the character of the vehicle body number set in the control device 9 is compared with the ASCII code extracted in step S7. If the two ASCII codes match, it is determined that the character of the vehicle body number set in the control device 9 is correctly engraved on the frame 1, and if both ASCII codes do not match. Then, it is determined that the frame 1 does not have the car body number characters set in the control device 9 correctly stamped. Then, the process proceeds to step S9.

In step S9, the result determined in step S8 is displayed on the monitor 29. Further, the characters set in the control device 9 and the characters corresponding to the ASCII code estimated in step S7 are also displayed on the monitor 29. Then, the process proceeds to step S10.
In step S10, it is confirmed whether or not the body number is newly stamped on another frame with respect to the control device 9. When the control device 9 notifies that the body number is newly stamped on another frame, the process proceeds to step S2, and when the notification that the stamping is completed is completed, the inspection is completed. .

  As described above, in this embodiment, the polarization azimuth emitted from the light projecting means 6 is reflected by irradiating the circularly polarized light whose azimuth angle rotates with the progress of the light on the engraved characters of the frame 1 to reflect the phase difference plate 15a and the polarizing plate. At 15, the light whose circular polarization state is maintained by being regularly reflected by the non-marked portion of the character is cut off from the reflected light, and the light is partially reflected by changing from the circular polarization state and irregularly reflecting at the stamped portion of the character. Most of the polarized light was transmitted, and the measuring means 7 measured the intensity of this transmitted light. Then, character image data corresponding to the intensity of the transmitted light is generated, the character image data is subjected to character recognition processing to detect the character of the measured vehicle body number, and the character of the vehicle body number set in the control device 9 The inspection to confirm that it is consistent with was done. Further, the generated character image data is stored in the hard disk, so that the characters of the vehicle body number stamped on the plurality of frames 1 are managed.

By the way, the state when the circularly polarized light emitted from the light projecting means 6 is reflected by the stamped character in the state described in the conventional example will be described in detail.
As shown in FIG. 5, the circularly polarized light is composed of two linearly polarized light X and Y whose azimuth angle is inclined by 90 degrees and whose phase is shifted by 90 degrees. Even if the light is reflected at the B portion shown in FIG. 11 and is regularly reflected, the polarization state of the linearly polarized light Y changes when reflected by the stamped character, so that the B portion in the stamped character shown in FIG. 11 is reliably detected. be able to. Further, even if the reflectivity is greatly reduced due to the Brewster's angle when the linearly polarized light Y becomes the P-polarized light and reflected by the portion C shown in FIG. 11, the polarization state of the linearly polarized light X is imprinted. Since it changes when reflected by a character, the C portion in the stamped character shown in FIG. 11 can be reliably detected.

  According to such a configuration, it is possible to accurately distinguish a portion whose surface has been modified by imprinting the characters of the frame 1 (an engraved portion) and a portion where the surface is not modified (a non-engraved portion). Therefore, the accuracy of checking that the character set in the control device 9 is correctly imprinted on the frame 1 can be improved. Moreover, the polarization state of the light regularly reflected at the non-marked portion of the character does not change depending on the light amount fluctuation of the laser light, the adhesion of an oil film or water on the surface of the frame 1, the uneven shape of the frame 1, and so on. Even if it occurs, the engraved characters can be recognized accurately, and the inspection accuracy can be maintained at a high level.

Further, the light projecting means 6 and the measuring means 7 are simple in configuration and require a small number of parts, so that the manufacturing cost of the inspection apparatus 3 can be reduced.
Further, the light projecting means 6 and the measuring means 7 are accommodated in one sensor head 10, and the reflected light from the frame 1 is measured by line scanning while moving the measurement position by the measurement position control means 8. The means 6 and the measuring means 7 can be brought close to the frame 1 to inspect the imprinted characters, whereby the imprinted characters can be accurately recognized and the inspection accuracy can be increased. Moreover, it is not necessary to increase the output light power of the semiconductor laser 13. Further, since the sensor head 10 (light projecting means 6 and measuring means 7) may be moved according to the number of characters set in the control device 9, it is possible to inspect the stamped characters efficiently.
In addition, since the character image data is recorded and stored in the hard disk built in the personal computer 19, it becomes easy to manage the characters of the car body number stamped on the plurality of frames 1 and manage the stamped characters. There is no need to provide a special device or management place for this purpose.

(Second embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. The same parts as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted, and only different parts will be described below.
First, the configuration of the inspection apparatus 30 will be described with reference to FIG. The measuring means 31 is configured as follows. A lens 32 for collecting the light reflected by the frame 1 is installed. A beam splitter 33 is installed in the vicinity of the lens 32, and the light collected by the lens 32 is transmitted through the beam splitter 33, so that the P-polarized component and the second polarized light as the light in the first polarization state are transmitted. It is separated into linearly polarized light of the S-polarized component that is light in the polarization state.

  Two line sensors 34 and 35 are installed in the vicinity of the beam splitter 33, and each of the line sensors 34 and 35 receives the linearly polarized light of the P-polarized component and the S-polarized component separated by the beam splitter 33. Are arranged as follows. In the vicinity of the line sensors 34 and 35, a P-polarization amplifier 36 and an S-polarization amplifier 37 are installed. In each of the line sensors 34 and 35, an analog signal generated according to the intensity of light received by each light receiving element is amplified by the P polarization amplifier 36 and the S polarization amplifier 37 and output to the personal computer 19. . The lens 32, the beam splitter 33, the line sensors 34 and 35, the P-polarization amplifier 36, and the S-polarization amplifier 37 constitute a measuring means 31.

Next, the operation of the inspection apparatus 30 will be described with reference to FIG.
FIG. 7 shows a flowchart of the inspection program installed in the personal computer 19. The same steps as those in FIG. 4 are denoted by the same step numbers and the description thereof is omitted. Only different portions will be described below.
In step S11, in the same manner as in step S4 shown in the first embodiment, the measurement means 31 is arranged at a position for measuring the first character of the engraved character by communication with the control device 9, and line scanning is performed. Measurement starts.

  In the line scanning measurement, the reflected light from the frame 1 in the line sensors 34 and 35 is measured as follows. The linearly polarized light of the P-polarized component and the S-polarized component detected by the light receiving elements of the respective line sensors 34 and 35 is converted into an analog signal. These analog signals are amplified to a predetermined voltage amplitude by the P-polarization amplifier 36 and the S-polarization amplifier 37, converted to digital signals by A / D conversion by the personal computer 19, and a memory (not shown) in the personal computer 19. To be recorded. In this way, all digital signals corresponding to the light detected by all the light receiving elements of the respective line sensors 34 and 35 are recorded in the memory. And while moving the stage 25, the reflected light measurement of all the stamped character parts is performed. When this reflected light measurement is completed, the process proceeds to step S12.

  In step S12, the ratio of the respective digital signals corresponding to the linearly polarized light of the P-polarized component and the S-polarized component detected at the same time in the respective light receiving elements of the respective line sensors 34 and 35 is, for example, the digital of the S-polarized component. Calculated by dividing the signal by the digital signal of the P-polarized component. Hereinafter, the calculated digital signal is referred to as a PS ratio digital signal.

  At this time, the polarization azimuth angle of the circularly polarized light whose polarization state is maintained by regular reflection at the non-marked portion of the character is rotated with the progress of light, so the light intensity of the P polarization component (digital Signal) and the light intensity of the S-polarized component (digital signal) are substantially the same. Therefore, the intensity of the linearly polarized light of the P-polarized component and the S-polarized component separated by the beam splitter 33 is almost the same. Therefore, the PS ratio digital signal of the light regularly reflected at the non-marked portion of the character is a value close to ‘1’.

  In addition, the light whose partial polarization state has changed due to the polarization state changing at the stamped portion of the character and diffusely reflected is biased in a certain direction, so the light intensity of the P-polarization component and S-polarization component (digital signal) ) Is a different value. Therefore, the intensity of the linearly polarized light of the P polarization component and the S polarization component separated by the beam splitter 33 is different. Therefore, the PS ratio digital signal of the light that is irregularly reflected at the stamped portion of the character has a value different from “1”. The PS ratio digital signal calculated in this way is recorded in a memory (not shown) in the personal computer 19, and the process proceeds to step S13.

In step S13, binarization processing is performed on all PS ratio digital signals recorded in the memory. This binarization processing is the same as that shown in step S5 of the first embodiment.
According to such a configuration, the beam splitter 33 is installed, and the intensity ratio of the linearly polarized light of the P-polarized component and the S-polarized component separated by the beam splitter 33 is obtained, so that regular reflection is performed at the non-marked portion of the character. The intensity of light is almost the same, the polarization state changes at the stamped portion of the character, and the intensity of the light that is irregularly reflected is different, so that it is easy to distinguish between the stamped portion and the non-printed portion of the character. Therefore, the recognition accuracy of the character of the vehicle body number stamped on the frame 1 is improved, and the accuracy of checking that the character set in the control device 9 is correctly stamped on the frame 1 can be increased.

The present invention is not limited to the embodiments described above and shown in the drawings, and the following modifications and expansions are possible.
Instead of circularly polarized light, elliptically polarized light may be projected, and the stamped character may be detected by detecting light having a polarization state different from that of the elliptically polarized light.
In this embodiment, the present invention is applied to inspecting the character of the car body number stamped by the stamping machine on the frame of the automobile body that is the inspection object, but the present invention is not limited to this. It can be applied to all materials whose surface is modified by engraving. For the same reason, it is not limited to stamping by a stamping machine, but may be stamped by a laser.

In this embodiment, the measurement position control means is provided, but it may be provided if necessary. In this embodiment, the measurement position control means is constituted by a precision stage base, a controller and a driver. However, the measurement position control means is not limited to this. For example, the articulated robot itself is moved. The measurement position control means may be configured.
In this embodiment, the data storage means is provided, but it may be provided if necessary. In this embodiment, the hard disk built in the personal computer is used as the data storage means. However, the present invention is not limited to this. For example, the data is recorded on a recording medium such as a floppy (registered trademark) disk, CD, or DVD. May be saved.

The block diagram of the inspection apparatus which shows 1st Example of this invention Inspection equipment layout Configuration diagram of measurement position control means Flow chart of inspection program Diagram showing circularly polarized light FIG. 1 equivalent view showing a second embodiment of the present invention Flow chart of inspection program FIG. 2 equivalent diagram showing a conventional example Diagram showing paper tape type inspection method Diagram showing optical inspection method Diagram showing detected stamp characters

Explanation of symbols

  In the drawings, 1 is a frame, 2 is an engraving machine, 3 and 30 are stamped character inspection devices, 5 is an articulated robot, 6 is a light projecting means, 6a is a phase difference plate, 7 and 31 are measuring means, and 7a is a measuring means. Phase plate, 8 is a measurement position control means, 9 is a control device, 13 is a semiconductor laser (coherence light source), 14, 16 and 32 are lenses, 15 is a polarizing plate, 17, 34 and 35 are line sensors, and 18 is an amplifier. , 19 is a personal computer (inspection means), 33 is a beam splitter, 36 is a P-polarization amplifier, and 37 is an S-polarization amplifier.

Claims (8)

  Polarization state is achieved by irradiating and reflecting circularly or elliptically polarized light whose azimuth angle rotates as the light travels on the character stamped on the inspection object, and regularly reflecting it at the non-marked portion of the character. The circularly polarized light or the elliptically polarized light that is held is blocked and reflected by the engraved portion of the character, so that most of the light in the partially polarized state changed from the polarized state of the irradiated circularly polarized light or elliptically polarized light is transmitted. Measuring the intensity of transmitted light, recognizing the engraved character based on the measured intensity of transmitted light, and comparing the recognized character with the predetermined character to inspect the predetermined character. A method for inspecting engraved characters, characterized by inspecting that an object is accurately engraved. A light projecting means for irradiating and reflecting circularly polarized light or elliptically polarized light whose azimuth angle rotates with the progress of light on the character stamped on the inspection object;
Of the reflected light reflected by the object to be inspected, the circularly polarized light or the elliptically polarized light whose polarization state is maintained by being regularly reflected by the non-marked portion of the character, and reflected by the stamped portion of the character, A measuring means for transmitting most of the light in the partially polarized state changed from the polarized state of the irradiated circularly polarized light or elliptically polarized light, and measuring the intensity of the transmitted light;
Based on the intensity of the transmitted light measured by the measuring means, the imprinted character is recognized, and by comparing the recognized character with the predetermined character, the predetermined character is accurately applied to the inspection object. An inspection device for inspecting stamped characters, comprising: inspection means for inspecting that the characters are stamped on the surface. The light projecting means includes a coherence light source that emits linearly polarized light, a collimator lens that makes light emitted from the coherence light source substantially parallel, and a circularly polarized light whose azimuth angle rotates with the linearly polarized light that has passed through the collimator lens. It consists of a phase difference plate that converts to polarized light or elliptically polarized light,
The measuring means includes a phase difference plate that converts circularly polarized light or elliptically polarized light, which is maintained in the polarization state by regular reflection at the non-marked portion of the character, from the reflected light from the inspection object, and this phase difference. A polarizing plate that blocks the linearly polarized light converted by the plate, a lens that collects the light that passes through the polarizing plate, and a light receiving unit that measures the intensity of the light that passes through the lens. The inspection apparatus for engraved characters according to claim 2. Polarization state is achieved by irradiating and reflecting circularly or elliptically polarized light whose azimuth angle rotates as the light travels on the character stamped on the inspection object, and regularly reflecting it at the non-marked portion of the character. The intensity ratio of the linearly polarized light of the first polarized light component and the second polarized light component is 1 among the circularly polarized light or elliptically polarized light in which is held, and the reflected circularly polarized light or elliptically polarized light is reflected by being reflected by the stamped portion of the character. The reflected light is divided into the first polarization component and the second polarization component so that the linearly polarized light intensity ratio of the first polarization component and the second polarization component among the light in the partial polarization state changed from the polarization state is different from 1. The polarized light component is separated into linearly polarized light, the intensity of the linearly polarized light of each of the separated polarized light components is measured, and the stamped character is recognized based on the measured linearly polarized light intensity of each of the polarized light components. And this recognized sentence And by comparison with the predetermined character, the inspection method of marking characters, characterized in that the predetermined characters are examined that is stamped exactly the inspection target. A light projecting means for irradiating and reflecting circularly polarized light or elliptically polarized light whose azimuth angle rotates with the progress of light on the character stamped on the inspection object;
Of the reflected light reflected by the inspection object, a straight line between the first polarization component and the second polarization component of circularly polarized light or elliptically polarized light whose polarization state is maintained by regular reflection at the non-marked portion of the character. The intensity ratio of polarized light is 1, and the first polarized light component and the second polarized light component of the light in the partially polarized state changed from the polarized state of the circularly polarized light or the elliptically polarized light irradiated by being reflected at the engraved portion of the character. The reflected light is separated into linearly polarized light of the first polarized light component and the second polarized light component so that the intensity ratio of the linearly polarized light is different from 1, and the intensity of the linearly polarized light of each of the separated polarized light components is measured. Measuring means to
Based on the linearly polarized light intensity of each polarization component measured by the measuring means, the imprinted character is recognized, and the predetermined character is inspected by comparing the recognized character with the predetermined character. An inspection device for engraved characters, comprising: inspection means for inspecting that an object is accurately engraved. The light projecting means includes a coherence light source that emits linearly polarized light, a collimator lens that makes light emitted from the coherence light source substantially parallel, and a circularly polarized light whose azimuth angle rotates with the linearly polarized light that has passed through the collimator lens. It consists of a phase difference plate that converts to polarized light or elliptically polarized light,
The measurement means includes a lens that collects the reflected light from the inspection object, a beam splitter that separates the transmitted light of the lens into a linearly polarized light of a P-polarized component and an S-polarized component, and a P-polarized component that is transmitted through the beam splitter. And a light receiving unit that measures the intensity of linearly polarized light of the S-polarized component,
The measurement means has an intensity ratio of linearly polarized light of P-polarized light component and S-polarized light component of the light regularly reflected by the non-marked portion of the character out of the transmitted light of the lens that collects the reflected light, and The polarization azimuth angle of the P-polarized component and the S-polarized component of the beam splitter is adjusted so that the intensity ratio of the linearly polarized light of the P-polarized component and the S-polarized component of the light reflected at the marking portion is different from 1. An inspection apparatus for engraved characters according to claim 5. The light projection means and the measurement means are configured to measure reflected light from a stamped character while being moved in a predetermined direction at a predetermined speed by being mounted on the measurement position control means. An inspection apparatus for engraved characters according to 2 or 5. 6. The inspected character inspection apparatus according to claim 2, wherein the inspection unit includes a data storage unit for storing the recognized character.

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