JP2006078713A - Work identification information reading device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a work identification information reading device and method with which the individual identification information of a work, such as an MR head, can be efficiently read through an image via a camera. <P>SOLUTION: The reading device includes: an objective lens disposed opposite to a face on which individual work identification information is carved; an image forming lens for forming a video of a slider onto the image forming face of a camera by receiving light from the objective lens; and a glass plate having a prescribed thickness, which is inserted/pulled in/from an optical path between the camera and the image forming lens. By the inserting/pulling of the glass plate, the imaged position in the direction of the focus depth of the objective lens is moved so that the image of the work is positioned within a focal range that allows imaging by the camera. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a workpiece identification information reading apparatus and reading method, and more specifically, a magnetic that can efficiently read individual identification information such as a serial number engraved on a head slider of an MR head via an image. The present invention relates to a head identification information reading device and a reading method.

In recent years, a composite magnetic head in which an MR head, a GMR head, a TMR head or the like is incorporated on the reading side is used as a magnetic head of a hard disk device. The recording density is steadily increasing to more than a dozen giga / inch, and the number of tracks becomes 10,000 / inch or more. Moreover, the number of tracks is increasing and the width is becoming narrower. For this reason, the head slider of the MR head has also become smaller, and its width has become 1 mm or less (Patent Document 1).
In an inspection apparatus for inspecting a magnetic head, inspection data must be managed in correspondence with the magnetic head, and therefore an individual identification number is required for the magnetic head to be inspected.
Conventionally, the serial number engraved on the side surface of the slider in the width direction is formed by edging or the like, and relatively large point characters (numbers and symbols) are used. Is read by a camera through a large optical system, and a manufacturing number is obtained from the read image by image processing, and the manufacturing number is converted into data.
Patent Document 2 is known as an example of an autofocus device used in this type of inspection.
JP 2000-90617 A JP 2003-66341 A

In the GMR head, since the pad for connecting the signal line is provided on the side surface of the slider on which the production number is written, the width of the production number region is about several hundred μm, even if the magnification of the optical system is increased. However, due to mounting variation and size variation of the magnetic head with respect to the reading device, it has become difficult to read an image with a conventional fixed focus optical system that exceeds the focus range.
Although it is possible to read the serial number carved on the side of the slider with an autofocus device, it takes time to complete the focusing process, and it immediately enters identification number analysis (serial number analysis). Therefore, there is a problem that the reading efficiency is lowered. In addition, when an autofocus device is introduced, there is a drawback that the price of the inspection device increases and the size of the device increases.
SUMMARY OF THE INVENTION An object of the present invention is to solve such problems of the prior art, and identification information of a work that can efficiently read individual identification information of a work such as an MR head with an image via a camera. To provide a reading device and a reading method.

In order to achieve such an object, the feature of the workpiece identification information reading apparatus and reading method of the present invention is that the identification information of the workpiece for reading the individual identification information engraved on the workpiece such as the head slider as an image through the camera. In the reading device,
An objective lens facing the surface on which the individual identification information of the workpiece is engraved, an imaging lens that receives light from the objective lens and forms an image of the slider on the imaging surface of the camera, a camera and an imaging lens, And a glass plate of a predetermined thickness inserted into and removed from the optical path between the two, and imaged in the direction of the depth of focus of the objective lens by inserting and removing the glass plate so that the image of the work enters the focal range that can be imaged by the camera The position of the image is moved.

As described above, according to the present invention, the glass plate is inserted into the optical path between the camera (imaging unit) and the imaging lens, or the inserted glass plate is removed, so that the camera can take a focus range. By moving the position of the workpiece image back and forth in the direction of the focal depth of the objective lens so that it enters the camera, the focus range of the camera is equivalent to the direction of the focal depth of the objective lens without changing the focal length of the camera. Selectively enlarge. As a result, even if there is a variation in the attachment or size of the work (magnetic head) with respect to the reading device and the position is slightly displaced, the image can be read by inserting and removing the glass plate.
As a result, individual identification information such as a minute serial number engraved on a work such as a head slider can be read as an image via a camera without introducing an autofocus device. In particular, individual identification information of a magnetic head such as an MR head (including a GMR head and a TMR head) can be efficiently read as an image via a camera.

FIG. 1 is an explanatory diagram of a head serial number reading stage of a magnetic head according to an embodiment to which a workpiece identification information reader of the present invention is applied, FIG. 2 is an explanatory diagram of a head slider, and FIG. It is explanatory drawing of the relationship between the insertion / extraction state and the movement position of the focus range of an imaging system.
In FIG. 1, 10 is a head manufacturing number reading stage, and 11 is a magnetic head (work) to be read.
Reference numeral 1 denotes a base of a head manufacturing number reading stage 10, and the imaging optical system 2 is entirely cylindrical, and has an objective lens tube 3 and an illumination prism tube 4 in front of the magnetic head 11. The imaging tube 5 having a camera mounting block at the rear is attached.
The imaging optical system 2 is fixed on the base 1 via a bracket 2 a provided on the illumination prism tube 4. The objective lens tube 3 includes an objective lens 3a having a magnification of about 10 to 20 times and a diaphragm mechanism 3b. The illumination prism tube 4 reflects illumination light in the direction of the objective lens to slide the slider 12a of the magnetic head 11. An illumination prism (or half mirror) 4a that transmits reflected light (image) from (see FIG. 2B) to the imaging tube 5 is mounted.
The imaging tube 5 has an imaging lens 5a inside, and loading windows 5b and 5c in which two glass plates 71 and 72 (see FIG. 3A) are loaded are provided behind the illumination tube 5 and an illumination prism. The tube 4 is fitted and fixed in the fitting cylinder 4 b and is fixed to the base 2 via the illumination prism tube 4.
The CCD camera 6 is coupled and fixed to the rear part of the imaging tube 5.

Reference numeral 7 denotes a focal range switching mechanism, which includes glass plates 71 and 72, advance / retreat drive cylinders 71 a and 72 a that advance and retract these glass plates with respect to the optical path of the imaging optical system 2, and a drive circuit 73. The advancing / retreating cylinders 71a and 72a advance or retract the glass plates 71 and 72 in the optical path behind the imaging lens 5a of the imaging optical system 2 through the loading windows 5b and 5c, respectively, and load or retract from the optical path. . These are provided adjacent to the imaging optical system 2 and drive the glass plates 71 and 72 forward and backward according to the drive of the drive circuit 73, respectively. The drive circuit 73 is controlled by the image processing / control device 74.
The image processing / control device 74 includes an MPU 75, a memory 76, an image memory 77, an interface 78, etc., which are connected to each other by a bus, and are connected to the CCD camera 6 through the binarization circuit 79 with a predetermined fixed threshold. The image for the frame is collected in a binarized state and stored in the image memory 77.
An illumination light source 8 is coupled to the illumination prism tube 4.
Reference numeral 9 denotes a magnetic head fixing base that detachably attaches and fixes a magnetic head (work) 11 to be read with a screw, and a foot portion 9 a thereof is fixed to the base 1. The magnetic head fixing base 9 is disposed at a predetermined distance, for example, about 45 mm away from the objective lens tube 3 with the slider side surface 12a (see FIG. 2B) facing the objective lens 3a.

FIG. 2 is an explanatory diagram of the head slider, and FIG. 2A is an explanatory diagram of the magnetic head 11 to be inspected. The magnetic head 11 from which the production number is read has a slider 12 attached to a gimbal spring 13 and a wiring provided to a pad 12b (see FIG. 2A) to form a head assembly.
Reference numeral 14 denotes a flexible lead wiring connected to the pad 12b.
FIG. 2B is an explanatory diagram of the slider 12. The slider 12 has a magnetic head main body (head element portion) 11a and an air bearing surface 12c. The slider side surface 12a is provided with four pads 12b for establishing electrical connection between the magnetic head body (head element portion) 11a and the outside.
FIG. 2 (c) is a partial explanatory view of the slider side surface 12a. Manufacturing number marking regions 12d are provided in two stages at the ends of the four pads 12b. In this area, the serial number is stamped by edging with alphanumeric characters or symbols. The width of one step area is about 100 μm, the height is about 25 μm, 5 to 6 characters are formed by edging in one step area, and the number of characters is 10 to 12 characters in two steps. .

FIG. 3 is an explanatory diagram of the relationship between the insertion / extraction state of the glass plate and the movement position of the focus range of the camera.
The glass plates 71 and 72 are rectangular glass plates having different thicknesses. As shown in FIG. 3A, the glass plate 71 has a thickness of 10 mm and the glass plate 72 has a thickness of 20 mm. Each of these is loaded into the imaging tube 5 portion of the imaging optical system 2 via the loading windows 5b and 5c of FIG.
The optical path on which the glass plates 71 and 72 are loaded is between the CCD camera 6 and the rear side of the imaging lens 5a. At a position behind the imaging lens 5a, the imaging lens 5a causes the light beam to become oblique toward the imaging surface of the CCD camera 6 and is focused on the imaging surface. Therefore, when a glass plate having a refractive index of 1.5 with respect to the refractive index of air 1 enters here, the inclination angle of the light beam increases, and the position of the image entering the CCD camera 6 from the objective lens 3a moves forward. As a result, the position of the image that falls within the focus range (focus range) of the CCD camera 6 is shifted forward. The amount of deviation is determined according to the thickness of the glass plates 71 and 72.

Therefore, the position S shown in FIG. 3B is set as a reference position (position of the slider side surface 12a) of the magnetic head 11 attached to the magnetic head fixing base 9. Here, the focus range of the image with respect to the imaging surface of the CCD camera 6 is set at a position behind the reference position S when the glass plate is not loaded in the optical path. That is, the CCD camera 6 has a focus range of A in the direction of the focal depth of the objective lens 3a when there is no glass plate in the optical path because of the relationship with the objective lens 3a and the imaging lens 5a of the imaging optical system 2. It is set to correspond to the position.
Here, as shown in FIG. 3A, when a glass plate 71 having a thickness of 10 mm is loaded in the optical path of the imaging optical system 2, oblique light that converges on the imaging plane passes through the glass plate 71. In order to be refracted, the position of the image entering the focus range of the CCD camera 6 is shifted forward, and the image of the image of the magnetic head 11 (its slider side surface 12a) from the objective lens 3a in the direction of the focal depth of the objective lens 3a. By moving the position, the focus range of the CCD camera 6 is equivalently moved to the position of the focus range B including the reference position S.
The amount of deviation is determined by the relationship between the objective lens 3a and the imaging lens 5a of the imaging optical system 2, and is about 33 μm here. Similarly, when the glass plate 71 is removed from the optical path of the imaging optical system 2 and the glass plate 72 having a thickness of 20 mm is loaded into the optical path of the imaging optical system 2, the light passes through the thicker glass plate 72. Therefore, the position of the image of the magnetic head 11 (its slider side surface 12a) from the objective lens 3a that falls within the focus range of the CCD camera 6 further moves. Thus, the focus range of the CCD camera 6 is equivalently moved to the position of the focus range C. The amount of deviation at this time is about 66 μm.

As a result, the imaging range of the work that can be captured by the CCD camera 6 is the entire D range, and the focus range that can be selected by the CCD camera 6 is expanded from the focus range A to the focus D. The depth of focus of the objective lens 3a itself corresponds to the range of D or is larger than this.
The mounting position of the magnetic head 11 (its slider side surface 12a) on the base 1 of the magnetic head fixing base 9 corresponds to the reference position S of the focus range B with the glass plate 71 inserted in the optical path. Further, the mounting variation and size variation of the magnetic head 11 are currently about 20 μm before and after. Therefore, even if the magnetic head (workpiece) 11 (the slider side surface 12a) to be imaged is shifted back and forth from the position of the reference position S, the slider side surface 12a can be imaged in any of the focus ranges A to C. It is.

Therefore, the image processing / control device 74 controls the focal range switching mechanism 7 via the interface 78 to collect three images. First, the first image of the slider side surface 12a is sampled in the state of the focus range A in which the glass plates 71 and 72 are not loaded in the optical path of the imaging optical system 2, and then the glass plate 71 is removed from the imaging optical system 2. A second image is taken with respect to the slider side surface 12a in the state of the focus range B after loading in the optical path. Further, the glass plate 71 is retracted from the optical path of the imaging optical system 2 and the glass plate 72 is loaded into the optical path of the imaging optical system 2, and a third image is taken for the slider side surface 12 a in the focus range C.
Then, the manufacturing number is analyzed from the three collected images, and the manufacturing number read as a predetermined number of digits is stored in the memory 76 as the manufacturing number of the magnetic head 11 (see FIG. 3A). The magnetic head 11 from which the serial number has been read is stored and managed at a predetermined position on the pallet, and is sent to a magnetic head inspection device or the like.

The memory 76 of the image processing / control device 74 stores an image collection program 76a, a serial number analysis program 76b, and the like.
The image acquisition program 76a is executed by the MPU 75, and the MPU 75 drives the backward and forward drive cylinders 71a and 72a backward to retract the glass plates 71 and 72 from the optical path of the imaging optical system 2 and in the focus range A state, the CCD camera. 6 is driven to collect the first image of the slider side surface 12 a and store it in the first area of the image memory 77. Next, the forward / backward drive cylinder 7 a is driven forward to load the glass plate 71 into the optical path of the image pickup optical system 2, and a second image is taken for the slider side surface 12 a in the focus range B, and the image memory 77 is next. Store in the area. Further, the forward / backward drive cylinder 71a is driven backward to retract the glass plate 71 from the optical path of the imaging optical system 2, and at the same time, the forward / backward drive cylinder 72a is driven forward to load the glass plate 72 into the optical path of the imaging optical system 2 for focusing. In the state of the range C, the third image of the slider side surface 12 a is sampled and stored in the next area of the image memory 77.

When the image acquisition program 76a is executed, the MPU 74 further calls the serial number analysis program 76b when the three images are stored in the image memory 77, and causes the MPU 75 to execute them. The manufacturing number analysis program 76b is executed by the MPU 75. The MPU 75 analyzes some of the numbers or any of the alphabetic characters by the pattern matching process of alphanumeric characters, and stores each manufacturing number marking area from the image data of each area of the image memory 77. A 12-digit five-digit character is obtained, and when there are five-digit characters in these areas, they are used as read data, and production number data is generated and stored as an analysis result in a predetermined storage area.
As a specific example of this analysis processing, for example, among the three binarized images of the focus ranges A, B, and C, an image in the focus range B that is an intermediate focus is first subjected to some numbers by alphanumeric pattern matching processing. Or any of the alphabetic characters, and when the matching rate is greater than or equal to a predetermined matching threshold value for each data (analyzed character), serial number data is generated. When the matching rate of any of the five characters in the image of each character in the focus range B is equal to or less than the threshold value, an alphanumeric pattern matching process is performed for either the focus range A or the focus range C. When the matching rate for each character is equal to or greater than a predetermined matching threshold value, the serial number data is generated.
When the matching rate of the image of each character in one of the focus range A and the focus range C is equal to or less than the threshold value, an alphanumeric pattern matching process is performed on the image of each character in the other of the focus range A and the focus range C. As described above, when the matching rate for each character is equal to or higher than a predetermined matching threshold value, serial number data is generated.
When the matching rate of the image of each other character in the focus range A and the focus range C is equal to or less than the threshold value, the focus range A to C that shows the highest matching rate for each character is selected as the analysis result. Remember. In this case, a flag indicating that the matching rate is less than or equal to the threshold for the image in each focus range is set.

As another embodiment, although not shown, an A / D conversion image processing board is provided in place of the binarization circuit 79, and 8-bit 256-gradation data is generated by this image board, and the memory The data is transferred to 76 as it is. For example, in the case of a 640 × 480 VGA image, about three images can be stored in the memory 76 as they are. Therefore, the image memory 77 is deleted.
A program for performing binarization processing of a fixed threshold value on the image data collected in the memory 76 is provided in the memory 76, whereby image data subjected to binarization processing is obtained, and an alphanumeric character is obtained by the manufacturing number analysis program 76b. The production number data is analyzed by pattern matching processing or the like.

As described above, in the embodiment, three images are collected in a state in which a glass plate is not inserted and one glass having a different thickness is inserted. Each state may be confirmed by a monitor or the like, and one of the focus ranges A, B, and C may be selected to collect one image.
Further, in the embodiment, the glass plates 71 and 72 are inserted one by one, but it goes without saying that these two glass plates may be inserted simultaneously.
Moreover, the thickness of the glass plate in an Example is an example, Comprising: This invention is not limited to the thickness of an Example.
Furthermore, in the embodiment, when there is no glass plate in the optical path, the glass plate is used with respect to the focus range of the CCD camera 6 determined by the relationship with the lens system such as the objective lens 3a and the imaging lens 5a of the imaging optical system 2. The position of the image of the workpiece is moved to the near side in the direction of the depth of focus of the objective lens. Depending on the number of stages of the lens system of the imaging optical system 2 and the way of configuration, the camera captures the image by inserting the glass plate. It is also possible to move the focus range for a possible image backward (backward) in the direction of the depth of focus. In such a case, the focus range of the CCD camera 6 when the glass plate is not inserted is set to the near side of the reference position S in the direction of the depth of focus.

FIG. 1 is an explanatory diagram of a head serial number reading stage of a magnetic head according to an embodiment to which a workpiece identification information reading apparatus of the present invention is applied. 2A and 2B are explanatory diagrams of the head slider. FIG. 2A is an explanatory diagram of a magnetic head to be inspected, FIG. 2B is an explanatory diagram of the slider, and FIG. It is a partial explanatory view of a slider side. FIG. 3 is an explanatory diagram of the relationship between the insertion / extraction state of the glass plate and the moving position of the focus range of the imaging system. FIG. 3 (a) is an explanatory diagram of the insertion / extraction state of the glass plate, and FIG. It is explanatory drawing of the movement position of the focus range of an imaging system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base, 2 ... Imaging optical system, 3 ... Objective lens tube,
3a ... objective lens, 3b ... stop mechanism, 4 ... illumination prism tube,
6 ... CCD camera, 7 ... Focus range switching mechanism,
8 ... Illumination light source, 9 ... Magnetic head fixing base,
10: Head production number reading stage, 11: Magnetic head,
11a: magnetic head body (head element portion),
12 ... Slider, 12a ... Slider side surface,
12b ... Air bearing surface, 12b ... Pad,
13 ... Gimbal spring, 14 ... Flexible lead wiring,
71, 72 ... glass plate,
73 ... Drive circuit, 74 ... Image processing / control device,
75 ... MPU, 76 ... memory,
76a ... Image collection program,
76b ... Production number analysis program,
77 ... Image memory, 78 ... Interface,
77: A binarization circuit.

Claims (7)

In a workpiece identification information reading device that reads individual identification information such as a manufacturing number engraved on a workpiece with an image through a camera,
An objective lens facing the surface on which the individual identification information of the workpiece is engraved;
An imaging lens that receives light from the objective lens and forms an image of the workpiece on the imaging surface of the camera;
A glass plate having a predetermined thickness inserted into and extracted from an optical path between the camera and the imaging lens;
A workpiece identification information reading device that moves a position of an image to be imaged in a direction of a focal depth of the objective lens by inserting and removing the glass plate so that an image of the workpiece is within a focus range that can be imaged by the camera.   2. The workpiece identification information reader according to claim 1, wherein the workpiece is a head slider, and the individual identification information is a manufacturing number of a magnetic head.   3. The head slider according to claim 2, further comprising an advancing / retreating mechanism for inserting / removing the glass plate with respect to the optical path, wherein the image of the head slider is sampled in each of a state in which the glass plate is inserted into and removed from the optical path. Device identification information reader.   The glass plate is composed of a plurality of sheets having different thicknesses, and the advance / retreat mechanism inserts / removes each of the plurality of glass plates into / from the optical path, and includes at least three of the inserted state and the removed state. 4. The workpiece identification information reading device according to claim 3, wherein an image of the head slider is collected, the three or more images are analyzed, and an optimum one is used as reading information of the manufacturing number.   And an image processing device that controls the advance / retreat mechanism to continuously collect the three or more images and sequentially analyzes the individual identification information of the three or more images. 5. The workpiece identification information reading device according to claim 4, wherein the workpiece identification number is optimum when the manufacturing number having a predetermined number of digits is obtained. In a workpiece identification information reading device that reads individual identification information such as a manufacturing number engraved on a workpiece with an image through a camera,
The imaging lens receives light from the objective lens facing the workpiece and forms an image of the workpiece on the imaging plane of the camera, and a predetermined thickness is formed in the optical path between the camera and the imaging lens. A workpiece identification information reading method for inserting and removing a glass plate and reading the individual identification information as an image through the camera.   7. The work identification information reading method according to claim 6, wherein the work is a head slider, and the individual identification information is a manufacturing number of a magnetic head.

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