JP2017131931A - Laser marking device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser marking device using a semiconductor laser, capable of accurately positioning a focal position of a laser beam on a surface of an object.SOLUTION: A laser marking device using a semiconductor laser: performs a spatial filtering using a differential filter to an original image, to create an output image; calculates a maximum luminance value of an output image for each of the output images; determines peak output images on the basis of the maximum luminance values of respective output images; calculates the number of peak output images associated with peak original images; calculate a sum of the number of the peak output images associated with the original images in which positions of an optical unit are included within a range of a position of the optical unit at the peak original image capturing ± E; and if the sum is equal to or more than a predetermined value, moves the optical unit to a position where the peak original image is captured, on the basis of positional information of the optical unit associated with the peak original image; and then performs marking on an object W.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laser marking device for marking a surface of an object with laser light.

  Recently, in addition to the date and place of manufacture, various data related to materials used and quality, etc., are converted into barcodes and two-dimensional codes, etc., and this is marked on the surface of the goods so that the goods are distributed on the market. There is an increasing demand for traceability that allows the history of an article to be tracked after it has been posted. Conventionally, when printing such a marking pattern on, for example, a glass epoxy substrate or a flexible substrate, a laser beam is emitted from a YAG laser, a carbon dioxide gas laser, or the like and irradiated onto the substrate by a galvanometer scanner to perform marking. Marking devices are frequently used. However, since many YAG lasers, carbon dioxide lasers, and the like have a relatively high output, they consume a large amount of energy and use a galvanometer scanner, resulting in a complicated structure. In addition, the load on the object to be marked for high output is large, and when the object is a substrate, there is a possibility of penetrating the protective layer (resist) on the surface.

  In contrast to such a conventional laser marking device, the present inventors have provided a laser marking device comprising a semiconductor laser and a lens driving unit that moves the objective lens within the beam diameter of the laser light emitted from the semiconductor laser. It has been proposed (see Patent Document 1). According to this laser marking device, there are advantages that the energy consumption is small and the structure is simpler than the conventional device. Further, since the output is not so high, there is little possibility of penetrating the resist on the substrate, and residues (fumes) at the time of marking can be suppressed.

Japanese Patent Laid-Open No. 2015-1000080

  By the way, in a laser marking device using a semiconductor laser, marking is performed by condensing laser light on the surface of an object to increase the energy density. For this reason, in order to perform marking under optimum conditions, it is necessary to accurately match the focal position of the laser beam to the surface of the object. However, when the type of the object is changed, the material, color, transmittance, and the like are also changed, and even if the surface state of the object is the same type, there are individual differences, so that adjustment is difficult at present.

  An object of the present invention is to solve such a point, and an object of the present invention is to accurately align the focal position of a laser beam on the surface of an object in a laser marking apparatus using a semiconductor laser. A laser marking device with a possible autofocus function is proposed.

The present invention is a laser marking device comprising a semiconductor laser and an optical unit for condensing the laser light from the semiconductor laser on the surface of the object, and marking the object with the condensed laser light. A drive unit that moves the optical unit relative to the object between a position in front of the position where the laser beam is expected to be collected and a position beyond the position, and the drive unit. An imaging unit that captures an image of the laser beam reflected by the object while moving the optical unit relatively, and acquires an original image; and the driving unit connected to the driving unit and the imaging unit; A control unit that operates the imaging unit in a predetermined process, and the control unit is a laser marking device that performs marking on the object after performing the following steps (a) to (g).
(A) associating each of the plurality of original images acquired by the imaging unit with relative positional information of the optical unit with respect to the object at the time of capturing each original image;
(B) calculating an original image maximum luminance value which is a maximum luminance value for each original image;
(C) When the original images are arranged in the order of the relative position of the optical unit with respect to the object at the time of capturing the original image, the maximum luminance value of the original image is larger than the previous and subsequent original images. Setting the original image as the peak original image,
(D) creating an output image associated with each original image by subjecting the original image to a spatial filtering process using a differential filter;
(E) calculating an output image maximum luminance value which is a maximum luminance value for each output image;
(F) When the output image is arranged in the order of the relative position of the optical unit with respect to the object at the time of capturing the original image, the maximum luminance value of the output image is larger than the previous and subsequent output images. Setting the output image as the peak output image,
(G) The number of the peak output images linked to the peak original image is calculated, and the position of the optical unit is ± E around the position of the optical unit at the time of capturing the peak original image. For the original images included in the range, the sum of the numbers of the peak output images linked to these original images is calculated, and if the sum of the numbers is equal to or greater than a predetermined number, the peak original image is Based on the position information of the optical unit linked to the peak original image, the driving unit is operated to determine that the peak original image is the image captured at the condensing position. A step of moving the image relative to the imaged position (where E is the depth of focus of the laser beam).

Further, when there are a plurality of the peak original images, it is preferable to perform the following step (h) instead of the step (g).
(H) When there are a plurality of the peak original images, the maximum value of the original image maximum luminance value in these peak original images is calculated, and the original image included in a predetermined value range with respect to the maximum value If there is one peak original image having the maximum luminance value, it is determined that this peak original image is an image picked up at a position where the laser beam is condensed, and the peak original image is associated with the peak original image. A step of operating the drive unit based on position information of the optical unit to move the optical unit to a position where the original peak image is captured;

  In addition, for the step (h), a plurality of peak original images exist, and the maximum original image luminance value included in a predetermined value range with respect to the largest original image maximum luminance value in these peak original images When there are a plurality of peak original images having a position of the optical unit at the time of capturing the peak original image, the original image is included in a range of ± E around the position of the optical unit. The sum of the numbers of the peak output images associated with the peak output image is calculated, and it is determined that the peak original image with the larger sum is the image captured at the position where the laser beam is condensed, It is preferable to perform a step of moving the optical unit to a position where the peak original image is picked up by operating the driving unit based on position information of the optical unit linked to the original image.

  In the step (d), the output image has an upward filter for extracting a portion having a gradation difference from bottom to top with respect to the vertical and horizontal directions in the peak original image, and from the top to the bottom. Extract a part with a gradation difference, a right filter to extract a part with a gradation difference from left to right, and a part with a gradation difference from right to left It is preferable that the filter is generated by performing spatial filtering processing with at least one of the leftward filters.

  First, when condensing the laser beam on the surface of the object, the present inventors imaged the laser beam irradiated to the object while moving the laser light source in the vertical direction with respect to the object, and the maximum in the captured image. We examined the method using the image with the highest luminance value as the focal position of the laser beam. However, depending on the type of object and the surface condition, the maximum luminance value often varies, and even for images with the largest maximum luminance value, it is often seen that the position where this image was captured is not the focal position of the laser beam. It was. Further examination is made, and in addition to the maximum luminance value (original image maximum luminance value) in the image (original image) obtained by imaging the laser beam, the image (output image) obtained by subjecting the original image to spatial filtering processing with a differential filter Focusing on the maximum luminance value (maximum luminance value of the output image), a peak original image whose original image maximum luminance value is larger than that of the surrounding original image, and a peak output image whose output image maximum luminance value is larger than that of the surrounding output image, It was found that the focal position of the laser beam can be accurately adjusted to the surface of the object by utilizing the correlation of the above.

  That is, in the laser marking device of the present invention, when condensing the laser beam on the surface of the object, the optical unit is placed between a position before the position where the laser beam is expected to be collected and a position beyond this position. In the meantime, the reflected light from the object is imaged to acquire a plurality of original images, and the maximum luminance value (original image maximum luminance value) in each original image is calculated. Then, for the original image, select the peak original image whose maximum luminance value is larger than that of the surrounding original images, and further create the output image associated with each original image by spatial filtering the original image with the differential filter At the same time, paying attention to the output image maximum brightness value which is the maximum brightness value of the output image, the peak output image having the output image maximum brightness value larger than the surrounding output images is selected. Through various studies by the inventors, the original image in which the position of the optical unit is within the range of ± E around the position of the optical unit at the time when the peak original image was captured is linked to these original images. It was found that if the sum of the number of peak output images obtained is equal to or greater than a predetermined number, it can be determined that the peak original image is an image captured at the focal position of the laser beam. Based on the position information of the optical unit, marking can be performed by moving the optical unit to the position where the peak original image is captured, thereby performing highly accurate marking with little variation. The aforementioned E is the depth of focus of the laser beam.

It is a figure explaining the structure of an optical unit about one Embodiment of the laser marking apparatus according to this invention. It is a figure explaining that the condensing point of a laser beam is displaced according to the movement of an objective lens. It is a figure explaining the structure of other embodiment about the optical unit shown in FIG. It is the schematic explaining one Embodiment of the laser marking apparatus according to this invention. It is a figure explaining the relationship between the position which a laser beam condenses, and the relative position of the target object with respect to an optical unit. It is a figure which shows an example of the captured original image and an original image maximum luminance value in each original image. FIG. 7A is a diagram for describing spatial filtering processing, and FIG. 7B is a diagram for describing four types of differential filters. It is a figure which shows the original image maximum luminance value linked | related with the original image, and an output image maximum luminance value. It is a figure which shows an example of the captured original image, the original image maximum luminance value in each original image, a white spot area size, and an output image maximum luminance value.

  Hereinafter, the present invention will be described more specifically with reference to the drawings. First, with reference to FIG. 1, a part related to laser light irradiation in the laser marking device according to the present invention will be described.

  In FIG. 1, the code | symbol 1 shows the semiconductor laser attached to the optical unit mentioned later. The semiconductor laser 1 can emit blue-violet laser light having a wavelength of 405 nm by continuous wave oscillation.

  Reference numeral 2 denotes an optical unit. The optical unit 2 performs marking by condensing the laser light from the semiconductor laser 1 on the surface of the object W. In the present embodiment, the collimating lens 3, the beam sampler 4, and the objective lens 5 are provided on the path from the semiconductor laser 1 to the object W.

  Laser light emitted from the semiconductor laser 1 first passes through the collimating lens 3. Laser light immediately after being emitted from the semiconductor laser 1 is diffused light, but can be converted into parallel light by passing through the collimating lens 3. When attaching the collimating lens 3 to the optical unit 2, the wavefront aberration of the laser beam that has passed through the collimating lens 3 is measured, and the defocus aberration is adjusted by adjusting the position of the collimating lens 3 on the Z axis (adjusting the focal position). The astigmatism is adjusted by tilting the collimating lens 3, and the tilt aberration is adjusted by adjusting the position of the collimating lens 3 in the XY plane. Each aberration is preferably adjusted to λ / 4 or less.

  The beam sampler 4 transmits the laser light that has passed through the collimating lens 3 toward the objective lens 5, and reflects the laser light reflected by the object W toward an imaging unit that will be described later.

  The objective lens 5 focuses the laser light that has passed through the beam sampler 4 on the surface of the object W. The beam diameter of the laser light converted into parallel light by the collimating lens 3 is about 3 mm in this embodiment, but is adjusted by the objective lens 5 so that the condensed light diameter is about 10 μm on the surface of the object W. doing.

  Further, the optical unit 2 has an objective lens 5 within a plane perpendicular to the optical axis A of the laser beam and within a range in which the optical center of the objective lens 5 is within the beam diameter of the laser beam (about 3 mm in the present embodiment). A lens driving unit 6 is provided for moving the lens with respect to the laser beam. In this embodiment, as shown in FIG. 1, the direction of the optical axis A coincides with the Z direction, and the lens driving unit 6 has an X direction orthogonal to each other on a plane (XY plane) perpendicular to the Z direction. An X-direction drive unit 6a and a Y-direction drive unit 6b that are movable in the respective directions with respect to the Y direction are provided. Here, the X direction drive unit 6a is configured to move in the X direction while holding the Y direction drive unit 6b, and the Y direction drive unit 6b moves in the Y direction while holding the objective lens 5. It is configured as follows.

  As shown in FIG. 2, if the objective lens 5 is moved in the X direction (distance X1) within the range where the optical center is within the beam diameter D of the laser beam, the focal point p is also in the same direction and the same distance. Can only be displaced. That is, when the objective lens 5 is moved by a predetermined distance in the X direction and the Y direction by the X direction driving unit 6a and the Y direction driving unit 6b, the condensing point p on the surface of the object W is set in the same direction. Since it can be displaced by the same distance, the required marking can be applied by moving the objective lens 5.

  Further, the optical unit 2 is provided with a mirror 7, an imaging lens 8, a low cut filter 9, and an imaging unit 10 such as a CCD camera. A part of the laser light condensed by the objective lens 5 is reflected by the object W, passes through the objective lens 5 again, and reaches the beam sampler 4. Since the beam sampler 4 is inclined by 45 degrees with respect to the XY plane, the laser light reflected by the beam sampler 4 travels in the −X direction, and the path is also set by the mirror 7 which is also inclined by 45 degrees with respect to the XY plane. It is changed in the + Z direction. Thereafter, light of a blue-violet component can be imaged on the light receiving surface of the imaging unit 10 by the imaging lens 8 and the low cut filter 9. That is, according to the optical unit 2 of the present embodiment, it is possible to observe the laser beam focused on the object W on the same axis.

  The optical unit 2 described above can also be configured as shown in FIG. Reference numeral 11 denotes a light emitter that emits light having a different wavelength with respect to the laser light of the semiconductor laser 1. In the present embodiment, a red LED having a wavelength of 630 nm is used. A collimating lens 12 is provided in front of the light emitter 11 and can convert red light from the light emitter 11 into parallel light. Further, in front of the collimating lens 12, a half mirror 13 provided at an inclination of 45 degrees with respect to the XY plane is provided. As a result, the parallel light from the collimating lens 12 travels in the −Z direction, and the path is changed in the + X direction by the above-described mirror 7 to reach the dichroic mirror 14. The dichroic mirror of this embodiment has a characteristic of transmitting laser light (wavelength 405 nm) while reflecting red light (wavelength 630 nm), and is inclined by 45 degrees with respect to the XY plane. Thereby, the light of the light emitter 11 reflected by the dichroic mirror 14 is applied to the object W and reflected by the object W, and the reflected light is reflected by the dichroic mirror 14 again. Thereafter, the light passes through the mirror 7 and the imaging lens 8, passes through the half mirror 13, and forms an image on the light receiving surface of the imaging unit 10. Since the reflectivity of the beam sampler 4 shown in FIG. 1 is about 4%, the dichroic mirror 14 has a reflectivity of 90 for red light, although the amount of light is insufficient to observe the marking of the object W with the imaging unit 10. Therefore, a sufficient amount of light reaches the imaging unit 10 and the marking of the object W can be observed. Since the transmittance of light having a wavelength of 405 nm to the dichroic mirror 14 is about 90%, the marking on the object W is hardly affected.

  Next, a laser marking device according to the present invention including the semiconductor laser 1 and the optical unit 2 described above will be described with reference to FIG. Reference numeral 20 denotes the laser marking device of the present embodiment. The laser marking device 20 includes an XY stage 21 on which an object W to be marked is placed. The XY stage 21 can move the object W in the X direction and the Y direction. For example, when the desired marking size exceeds the movement range of the lens driving unit 6, the lens driving unit 6. After marking according to the above, by moving the object on the XY stage 21, marking of a large size can be performed. The XY stage 21 may be a fixed stage, and the entire optical unit 2 may be moved in the X direction and the Y direction. Further, the laser marking device 20 has a drive unit 22 (hereinafter referred to as “Z-direction drive unit 22”) capable of moving the optical unit 2 in a direction perpendicular to the object W (in this embodiment, the Z direction). And a control unit 23 connected to at least the imaging unit 10 and the Z-direction driving unit 22. The control unit 23 of the present embodiment controls the entire operation of the laser marking device 20, and switches between light emission and non-light emission of the semiconductor laser 1 according to a desired marking pattern, or the X direction of the lens driving unit 6. It is possible to drive the drive unit 6a and the Y-direction drive unit 6b.

  Next, a procedure for condensing the laser light from the semiconductor laser 1 on the surface of the object W by the laser marking device 20 of the present embodiment will be described.

  In the present embodiment, it is assumed that the laser light emitted from the semiconductor laser 1 is condensed at P5 shown in FIG. 5 through the center of the objective lens 5 shown in FIG. Then, the optical unit 2 is moved relative to the object W in the vertical direction by the Z-direction drive unit 22 driven by the control unit 23. Here, the optical unit 2 has a position closer to the object W than the position where the laser light is expected to be condensed (the position where the distance between the optical unit 2 and the object W is wide and the laser light is condensed). From the position on the front side of the object W) to a position beyond this (position where the distance between the optical unit 2 and the object W is narrow and the position where the laser beam is focused is located on the back side of the object W) It is movable. In the present embodiment, the position where the distance between the optical unit 2 and the object W is wide from the position where the distance between the optical unit 2 and the object W is narrow (the position where the object W is positioned at P1) (the object W becomes P7). The optical unit 2 is moved relative to the object W until the position of the object W is reached.

  Further, the imaging unit 10 can acquire an image (original image) of the laser beam reflected by the surface of the object W at an arbitrary position while moving the optical unit 2. In this embodiment, an original image is acquired every time the optical unit 2 is moved by 0.05 mm. Here, FIG. 6 shows a part of the acquired original image, and in the original image (I1, I2, I3... I7), the object W is set to P1, P2, P3. An example of the original image at the position to be positioned is shown. In addition, about P1, P2 ... P7, the distance between each point shall be 0.2 mm. The original image acquired in this embodiment is a black and white image.

  And each acquired original image is linked | related with the relative positional information of the optical unit 2 with respect to the target object W at the time of imaging each original image. In the present embodiment, information that the object W was captured at the time when the object W was positioned at P1... P7 is associated with each of the original images I1.

  Further, for each original image, a maximum luminance value (original image maximum luminance value) which is the highest luminance value in the image is calculated. The original image of this embodiment is composed of a large number of pixels represented by luminance values from 0 to 255, and the luminance value of the brightest pixel (close to white) in each image is the original image maximum luminance value. FIG. 6 illustrates an original image maximum luminance value corresponding to the above-described original image.

  Then, when these original images are arranged in the order of the relative position of the optical unit with respect to the object at the time of capturing the original image, the original image having a maximum original image maximum luminance value larger than the previous and subsequent original images Set as image. In the example shown in FIG. 6, the original image maximum luminance value of the original image I5 is larger than the original image maximum luminance value of the previous original image I4 and is larger than the original image maximum luminance value of the subsequent original image I6. Therefore, the original image I5 is set as the peak original image.

  Furthermore, an output image associated with each original image is created by subjecting the original image to a spatial filtering process using a differential filter. In the present embodiment, as shown in FIG. 7A, for each pixel of the original image, a sum of products is calculated by superimposing a differential filter on the luminance value in the 3 × 3 region centered on this pixel, and the output Assuming that the value is a luminance value subjected to spatial filtering, it is applied as a pixel of the output image to a portion corresponding to the original pixel. Then, this process is performed on all the pixels of the original image to create an output image. It is assumed that the original image and the output image obtained by performing spatial filtering processing are associated with each other.

  Here, the differential filter of the present embodiment includes an upward filter F1 that extracts a portion having a gradation difference from the bottom to the top as shown in FIG. A downward filter F2 that extracts a portion with a gradation difference from the bottom, a right filter F3 that extracts a portion with a gradation difference from the left to the right, and a gradation difference from the right to the left It is represented as a left direction filter F4 that extracts a certain part. Then, a spatial filtering process is performed using these four filters to create four output images for one original image.

  Further, for each output image, a maximum luminance value (output image maximum luminance value) which is the highest luminance value in the image is calculated. In FIG. 8, the output image maximum luminance value of the output image obtained by the upper filter F1, the output image maximum luminance value of the output image obtained by the lower filter F2, and the output of the output image obtained by the right filter F3. The image maximum brightness value and the output image maximum brightness value of the output image obtained by the left direction filter F4 are illustrated together with the original image maximum brightness value in the above-described original images I1 to I7.

  When the output image is arranged in the order of the relative position of the optical unit with respect to the object at the time of capturing the original image, the original image whose output image maximum luminance value is larger than the previous and subsequent output images is defined as the peak output image. Set. In the example shown in FIG. 8, paying attention to the output image maximum luminance value of the output image obtained by the upward filter F1, the output image maximum luminance value corresponding to the original image I5 is the output corresponding to the previous original image I4. Since it is larger than the image maximum luminance value and larger than the output image maximum luminance value corresponding to the subsequent original image I6, the output image corresponding to the original image I5 is output among the output images obtained by the upward filter F1. Set as peak output image. The peak output image is selected in the same manner for the down filter F2, the right filter F3, and the left filter F4. In FIG. 8, the maximum luminance value of the original image marked with a star is a value in the peak original image, and similarly, the maximum luminance value of the output image marked with a star is a value in the peak output image.

  Then, the number of peak output images associated with the peak original image is calculated, and an original image in which the position of the optical unit is included in a range of ± E around the position of the optical unit at the time of capturing the peak original image The sum of the number of peak output images associated with these original images is calculated, and if the sum of the numbers is equal to or greater than a predetermined number, the peak original image is captured at a position where the laser beam is condensed. Processing to determine that the image is an image is performed. Here, E is the depth of focus of the laser light, and is 0.2 mm in this embodiment. Further, as the predetermined number, for example, a predetermined number can be used according to the type of the object W, and the predetermined number is set to 4 in the present embodiment. The predetermined number is not determined in advance, and the sum of the number of peak output images in the original image in which the position of the optical unit is included in the range of ± E around the position of the optical unit, and the range of the optical unit is in the range of ± E. The sum of the number of peak output images in the original images not included in (if the number of original images not included in the range of ± E is different from the number of original images included in the range of ± E, The sum of the number of peak output images in the original image included in the range is greater than the sum of the number of peak output images in the original image not included in the range. If larger, the peak original image that is the center of the range may be determined to be an image captured at a position where the laser beam is condensed.

  If the sum of the numbers is equal to or greater than a predetermined number, the Z-direction driving unit 22 is operated based on the position information of the optical unit 2 associated with the peak original image, and the optical unit 2 is Move to the imaged position. In the present embodiment, as shown in FIG. 8, the original image in which the position of the optical unit is within the range of ± E (± 0.2 mm) around the peak original image (original image I5) is P1 as described above. , P2... P7, the distance between each point is 0.2 mm, so there are three original images I4 to I6. The sum of the number of peak output images associated with the original images I4 to I6 is four. Since this is equal to or greater than a predetermined number (4 in the present embodiment) and satisfies the condition, the Z-direction drive unit 22 is operated to move the optical unit 2 to a position where the surface of the object W is positioned at P5. The object W is marked at this position. In the laser marking device 20 of this embodiment, if the sum of the number of peak output images linked to the peak original image is less than a predetermined number, the XY stage 21 is driven (the XY stage 21 is fixed to the fixed stage). In the case of a configuration in which the entire optical unit 2 is moved in the X and Y directions, a retry processing function is provided for acquiring the original image from the beginning by moving the entire optical unit 2 in the X and Y directions.

  By the way, when there are a plurality of peak original images, the maximum value of the original image maximum luminance value in these peak original images is calculated, and the maximum original image luminance included within a predetermined value range with respect to the maximum value. If there is one peak original image having a value, it is determined that this peak original image is an image captured at a position where the laser beam is condensed. In other words, if the difference between the largest value and the next value among the maximum values of the original image in the peak original image is larger than the predetermined value, the peak original image having the largest original image maximum luminance value is focused on the laser beam. It is determined that the image is captured at the position where the light shines. This process will be described with reference to FIG. The predetermined value is set to 10 here. In the example shown in FIG. 9, there are two peak original images (original image J2 and original image J5). Here, the original image maximum luminance values of the original image J2 and the original image J5 are both 202 and do not meet the above-described conditions. In this case, the following processing is performed.

  As shown in FIG. 9, when a plurality of peak original images exist even if attention is paid to the original image maximum luminance value included in the range of the predetermined value with respect to the largest original image maximum luminance value, in the present embodiment, The sum of the number of peak output images associated with the original image is calculated for the original image in which the position of the optical unit is within the range of ± E centered on the position of the optical unit at the time of capturing the peak original image. Then, it is determined that the peak original image having the larger sum is an image captured at a position where the laser beam is condensed.

  The above process will be described with reference to FIG. The original images J1 to J7 are a part of the original image picked up by moving the optical unit 2 at a pitch of 0.05 mm. Here, the original images are selected every 0.2 mm. ing. The focal depth E of the laser light is 0.2 mm. First, regarding the original image J2, there are three original images J1 to J3 in which the position of the optical unit 2 is included in a range of ± E around the position of the optical unit 2 at the time of capturing the image. . The sum of the number of peak output images associated with the original images J1 to J3 is one. Next, with respect to the original image J5, there are three original images J4 to J6 in which the position of the optical unit 2 is included in the range of ± E around the position of the optical unit 2 at the time of capturing the image. . The sum of the number of peak output images associated with the original images J4 to J6 is four. In this case, since the one with the larger sum is the original image J5, it is determined that the original image J5 is an image captured at a position where the laser beam is condensed, and the surface of the object W is positioned at P5. The optical unit 2 is moved to the position, and the object W is marked at this position. If the sum of the above numbers is the same, the retry process described above is performed.

  In the present embodiment, when there are a plurality of peak original images, attention is first paid to the peak original image having the maximum original image luminance value included in the predetermined value range with respect to the largest original image maximum luminance value, and then Focusing on the sum of the number of peak output images associated with this original image for the original image in which the position of the optical unit is within the range of ± E, the determination was made based on the sum of the number of peak output images first. Then, attention may be paid to the peak original image having the original image maximum luminance value included in the predetermined value range with respect to the next largest original image maximum luminance value.

  As mentioned above, although one Embodiment of the laser marking apparatus according to this invention was described, this invention is not limited to the above-mentioned embodiment, A various change is included in the range according to a claim. For example, when determining that the selected peak original image is an image picked up at a position where the laser beam is condensed, a range (white point area) of a predetermined luminance value or more for pixels included in the original images J1 to J7. Size) (see FIG. 9), and a function of determining that the original image with the small white area size (original image J5 in FIG. 9) is an image captured at the position where the laser beam is focused, Or you may replace the function demonstrated so far. In the above-described embodiment, the optical unit 2 is moved in the Z direction with respect to the object W. However, the optical unit 2 may be fixed and the object W may be moved in the Z direction.

1: Semiconductor laser 2: Optical unit 3: Collimating lens 4: Beam sampler 5: Objective lens 6: Lens driving unit 6a: X direction driving unit 6b: Y direction driving unit 7: Mirror 8: Imaging lens 9: Low cut filter 10 : Imaging unit 11: Luminescent body 12: Collimating lens 13: Half mirror 14: Dichroic mirror 20: Laser marking device 21: XY stage 22: Drive unit (Z direction drive unit)
23: Control unit F1: Upward filter F2: Downward filter F3: Rightward filter F4: Leftward filters I1 to I7: Original images J1 to J7: Original image W: Object

Claims (4)

A laser marking device comprising a semiconductor laser and an optical unit for condensing laser light from the semiconductor laser on the surface of the object, and marking the object with the condensed laser light,
A drive unit that moves the optical unit relative to the object between a position in front of and beyond the position where the laser beam is expected to be collected; and An imaging unit that captures an image of a laser beam reflected by the object while relatively moving the optical unit to acquire an original image; and the driving unit and the imaging unit connected to the driving unit and the imaging unit A control unit that operates the imaging unit in a predetermined process,
The control unit is a laser marking device that performs marking on the object after performing the following steps (a) to (g).
(A) associating each of the plurality of original images acquired by the imaging unit with relative positional information of the optical unit with respect to the object at the time of capturing each original image;
(B) calculating an original image maximum luminance value which is a maximum luminance value for each original image;
(C) When the original images are arranged in the order of the relative position of the optical unit with respect to the object at the time of capturing the original image, the maximum luminance value of the original image is larger than the previous and subsequent original images. Setting the original image as the peak original image,
(D) creating an output image associated with each original image by subjecting the original image to a spatial filtering process using a differential filter;
(E) calculating an output image maximum luminance value which is a maximum luminance value for each output image;
(F) When the output image is arranged in the order of the relative position of the optical unit with respect to the object at the time of capturing the original image, the maximum luminance value of the output image is larger than the previous and subsequent output images. Setting the output image as the peak output image,
(G) The number of the peak output images linked to the peak original image is calculated, and the position of the optical unit is ± E around the position of the optical unit at the time of capturing the peak original image. For the original images included in the range, the sum of the numbers of the peak output images linked to these original images is calculated, and if the sum of the numbers is equal to or greater than a predetermined number, the peak original image is Based on the position information of the optical unit linked to the peak original image, the driving unit is operated to determine that the peak original image is the image captured at the condensing position. A step of moving the image relative to the imaged position (where E is the depth of focus of the laser beam). The laser marking device according to claim 1, wherein when a plurality of the peak original images are present, the following step (h) is performed instead of the step (g).
(H) When there are a plurality of the peak original images, the maximum value of the original image maximum luminance value in these peak original images is calculated, and the original image included in a predetermined value range with respect to the maximum value If there is one peak original image having the maximum luminance value, it is determined that this peak original image is an image picked up at a position where the laser beam is condensed, and the peak original image is associated with the peak original image. A step of operating the drive unit based on position information of the optical unit to move the optical unit to a position where the original peak image is captured;   For the step (h), there are a plurality of peak original images, and the maximum original image maximum luminance value included in the range of a predetermined value with respect to the largest original image maximum luminance value in these peak original images is provided. When there are a plurality of peak original images, an original image in which the position of the optical unit is included in a range of ± E around the position of the optical unit at the time of capturing the peak original image is linked to the original image. The sum of the number of the attached peak output images is calculated, and it is determined that the peak original image with the larger sum is the image captured at the position where the laser beam is condensed, and the peak original image The laser marking device according to claim 2, wherein the step of moving the optical unit to a position where the peak original image is captured is performed by operating the driving unit based on position information of the optical unit linked to the laser beam.   In the step (d), the output image includes an upward filter that extracts a portion having a gradation difference from the bottom to the top in the vertical and horizontal directions in the peak original image, and a floor from the top to the bottom. Downward filter to extract the part with tonal difference, rightward filter to extract the part with gradation difference from left to right, and leftward direction to extract the part with gradation difference from right to left The laser marking device according to any one of claims 1 to 3, wherein the laser marking device is generated by performing spatial filtering processing with at least one of the filters.