JP3388126B2 - Inspection method in apparatus having optical system and imaging means - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection method in an apparatus having an optical system and an image pickup means, and more particularly to an inspection method for a perpendicularity of an image pickup target surface to an optical axis of the optical system and the image pickup means. is there.

[0002]

2. Description of the Related Art In recent years, as the processing precision required at the manufacturing site has increased, very high precision has also been required for the processing apparatus and inspection apparatus for manufactured products.

For example, an inspection apparatus for inspecting a magnetic recording track pattern on a magnetic tape recorded by a magnetic recording / reproducing apparatus such as a VTR will be described. The magnetic recording / reproducing apparatus is formed on a magnetic tape. Since a signal is recorded in a very narrow area called a track, it is important to keep the linearity of the track at a high level in order to ensure compatibility between individual VTR devices. Therefore, it is an important technical subject to improve the accuracy of the device for measuring the linearity of the track.

Consumer digital VTRs currently on the market
In case of DVC, the required track linearity is 3
It is about μm. Therefore, an apparatus for measuring and inspecting the linearity of the track requires measurement accuracy of submicron level. Japanese Unexamined Patent Publication No. 3-222102 discloses a device for performing such highly accurate measurement, in which the magnetic recording track pattern is imaged by using an imaging means and the obtained image is analyzed to determine the track displacement state. A method of obtaining is described.

In such an apparatus which requires high accuracy, high accuracy is required also in assembling the apparatus itself, and the optical system of the apparatus or the optical axis of the image pickup means and the perpendicularity of the image pickup target surface are set. In order to make the adjustment, in the conventional method, the level is installed on the installation surface of the magnetic tape and the horizontal surface of the support member of the imaging means, that is, the surface which should be kept horizontal after the device is assembled, and the level is set on each surface. The method of doing was adopted.

As another example of a method for measuring the perpendicularity between the optical axis of another optical system or image pickup means and the surface to be imaged, Japanese Patent Laid-Open No. 142346/1995 measures the tilt amount of a wafer in a semiconductor exposure apparatus. As a method, there is a description regarding a measurement method using focus position detection by an AF (autofocus) sensor using projection of a slit pattern.

FIG. 17 is a block diagram of an apparatus used in the above-mentioned measuring method, in which 20 is a wafer to be exposed, B is an optical axis of wafer exposure light, 21 is a light source, 22 is an opening pattern consisting of a slit pattern, and 23. Is an objective lens, and the light transmitting system 24 includes a light source 21, an aperture pattern 22, and an objective lens 23.

Further, 25 is an objective lens, 26 is a mirror with a variable tilt angle used for adjusting the initial focus position, 27 is an imaging lens, 28 is a vibration slit having a slit similar to the aperture pattern 22, and 29 is a vibration slit 28. A photoelectric detector that detects the passing light in synchronization with the drive signal of the vibration slit 28,
The light receiving system 30 includes an objective lens 25, a mirror 26, an imaging lens 27, a vibration slit 28, and a photoelectric detector 29.

A measuring method having the above-mentioned configuration will be described. A slit pattern is projected obliquely with respect to the optical axis B on the exposure area on the wafer 20 using the light sending system 24. The projected slit pattern is received by using the light receiving system 30. If the position of the wafer 20 coincides with the focal positions of the light transmitting system 24 and the light receiving system 30, the light emitted from the light transmitting system 24 can be received by the light receiving system 30. However, if the position of the wafer 20 shifts in the direction of the optical axis B, the position of the slit pattern imaged by the light receiving system 30 shifts, so that the signal level detected by the photoelectric detector 29 decreases. Focus position detection is performed by utilizing this change in signal level.

Then, by performing such focus position detection at several points within the wafer 20, the amount of tilt of the wafer 20 with respect to the optical axis B has been measured.

[0011]

However, in the conventional measuring method, the method using the level, which was used for adjusting the verticality of the magnetic recording track pattern inspection apparatus, was not sufficient in resolution. In addition, JP-A-3-222102
In the method described in the publication, no consideration is given to the perpendicularity between the optical system or the optical axis of the image pickup means and the image pickup target surface. Further, the tilt amount measuring method disclosed in Japanese Patent Laid-Open No. 7-142346 requires a device for detecting the position of the imaging target surface, which is an AF sensor, which causes a problem of increasing the cost of the entire device. .

In view of the conventional problems described above, the present invention detects the position of the optical system or the image pickup target surface in the optical axis direction of the image pickup unit in an apparatus having an optical system to be inspected for verticality and an image pickup unit. It is an object of the present invention to provide an inspection method capable of accurately inspecting the perpendicularity of an image pickup target surface with respect to the optical axis of an optical system or an image pickup means without adding a device for the above.

[0013]

In order to achieve the above object, an inspection method in an apparatus having an optical system and an imaging means according to the present invention according to claim 1 has at least three points which are not on the same straight line on an imaging target surface. A plurality of lattice images including only the lattice pattern are obtained by individually capturing the lattice pattern having a constant lattice pitch and a constant lattice direction without changing the focus and magnification of the image capturing unit. By comparing the number of grids in the plurality of grid images obtained in the second step with the step, a second step of counting the number of grids included in the plurality of grid images in a predetermined direction, A third step of inspecting the perpendicularity of the surface to be imaged with respect to the optical axis of the imaging means.

According to the present invention, in the first aspect of the present invention, the first step is performed by using the image pickup means to image a lattice pattern installed on the image pickup target surface and having a constant lattice pitch and lattice direction. It is also possible to replace the step with the step of cutting out at least three grid images which are not on the same straight line in the image obtained in this step but have the same size and shape.

According to the present invention, in the invention described in claim 1, in the second step, Fourier transform is performed in a direction in which the number of grids is counted in the plurality of grid images, and 1 is obtained from a frequency spectrum obtained. It is also possible to replace with the step of counting the number of grids included in the grid image by detecting the peak of the next frequency component.

According to the present invention, in the invention described in claim 1, in the second step, Fourier transform is performed in a direction in which the number of grids is counted in the plurality of grid images, and 1 is obtained from a frequency spectrum obtained. Extracting a next frequency component, performing an inverse Fourier transform on the extracted first frequency component, and calculating a phase value distribution in the lattice image from a ratio of a real part and an imaginary part of the result, It may be replaced with the step of counting the number of grids included in the grid image using the phase value distribution.

Further, according to another aspect of the present invention, there is provided an inspection method for an apparatus having an optical system and an image pickup means, wherein the inspection method is installed in at least three positions which are not on the same straight line on the image pickup target surface. By individually capturing a lattice pattern with a constant lattice pitch and lattice direction without changing the focus and magnification of the image capturing means,
A first step of obtaining a plurality of grid images including only the grid pattern; a second step of counting the number of grids included in the plurality of grid images in a predetermined direction; By performing the step 2 by setting the image pickup target surface at a plurality of positions in the optical axis direction of the image pickup means, a change in the number of lattices with respect to a position change of the image pickup target surface in the optical axis direction of the image pickup means. Of the number of lattices obtained in the third step of obtaining the magnification and the second step, it was obtained from all the lattice images when the position of the image pickup target surface in the optical axis direction of the image pickup means was constant. From the difference in the number of grids,
A fourth step of quantitatively inspecting the perpendicularity of the image pickup target surface with respect to the optical axis of the image pickup means by using the change rate obtained in the third step.

According to the present invention, in the fifth aspect of the present invention, in the first step, an image of a lattice pattern having a constant lattice pitch and a constant lattice direction set on the image pickup target surface is picked up by the image pickup means. It is also possible to replace the step with a step of cutting out at least three grid images which are not on the same straight line in the image obtained in this step but have the same size and shape.

According to the present invention, in the invention described in claim 5, in the second step, Fourier transform is performed in a direction in which the number of grids is counted in the plurality of grid images, and 1 is obtained from a frequency spectrum obtained. It is also possible to replace with the step of counting the number of grids included in the grid image by detecting the peak of the next frequency component.

Further, in the present invention according to claim 5, in the second step, Fourier transform is performed in the direction in which the number of grids is counted in the plurality of grid images, and 1 is obtained from a frequency spectrum obtained. Extracting a next frequency component, performing an inverse Fourier transform on the extracted first frequency component, and calculating a phase value distribution in the lattice image from a ratio of a real part and an imaginary part of the result, The phase value distribution may be used to replace the step of counting the number of grids included in the grid image.

Further, according to another aspect of the present invention, there is provided an inspection method for an apparatus having another optical system and an image pickup means, wherein the magnetic field recorded by the magnetic recording / reproducing apparatus and subjected to the visualization processing. What is claimed is: 1. An inspection method in an apparatus having an optical system for imaging and inspecting a magnetic recording track pattern on a tape, and an imaging means, wherein a grating pattern having a constant grating pitch and a uniform grating direction is formed on the imaging surface of the magnetic tape. The first step of installing in at least three positions in the same plane and not on the same straight line, and by individually imaging the grating pattern without changing the focus and magnification of the imaging means, The second step of obtaining a plurality of grid images including only the pattern and the number of grids included in the plurality of grid images are controlled in a predetermined direction. And a fourth step of inspecting the perpendicularity of the image pickup surface of the magnetic tape to the optical axis of the image pickup means by comparing the number of grids obtained in the third step, respectively. Have.

According to the present invention, in the invention described in claim 9, the second step is a step of picking up the image of the lattice pattern by the image pick-up means, and the same line in the image obtained in this step. Alternatively, it may be replaced with a step of cutting out at least three grid images having the same size and shape.

Further, in the present invention according to claim 9, in the third step, Fourier transform is performed in the direction in which the number of grids is counted in the plurality of grid images, and 1 is obtained from a frequency spectrum obtained. It is also possible to replace with the step of counting the number of grids included in the grid image by detecting the peak of the next frequency component.

According to the present invention, in the invention described in claim 9, in the third step, Fourier transform is performed in a direction in which the number of grids is counted in the plurality of grid images, and 1 is obtained from a frequency spectrum obtained. Extracting a next frequency component, performing an inverse Fourier transform on the extracted first frequency component, and calculating a phase value distribution in the lattice image from a ratio of a real part and an imaginary part of the result, The phase value distribution may be used to replace the step of counting the number of grids included in the grid image.

Further, according to the present invention, there is provided an inspection method in an apparatus having another optical system and an image pickup means, wherein a magnetic tape recorded by a magnetic recording / reproducing apparatus and subjected to a visualization process is used. Of the magnetic recording track pattern, the inspection method in an apparatus having an optical system and an image pickup means, wherein a lattice pattern having a constant lattice pitch and a lattice direction is substantially the same as the image pickup surface of the magnetic tape. A first step of installing in at least three positions that are not on the same straight line in the plane, and by individually imaging the grid pattern without changing the focus and magnification of the imaging means, only the grid pattern is obtained. A second step of obtaining a plurality of grid images including
The third step of counting the number of grids included in the plurality of grid images in a predetermined direction, the second step and the third step, and the grid pattern at a plurality of positions in the optical axis direction of the imaging means. Of the number of grids obtained in the third step and a fourth step of obtaining the rate of change of the number of grids with respect to the position change of the grid pattern in the optical axis direction of the imaging means The change rate obtained in the fourth step is used from the difference in the number of lattices obtained from all the lattice images when the position of the image pickup target surface in the optical axis direction of the image pickup means is constant. A fifth step of quantitatively inspecting the perpendicularity of the image pickup surface of the magnetic tape with respect to the optical axis of the image pickup means.

According to the invention of claim 13, in the second step, the step of picking up the image of the lattice pattern using the image pick-up means and the same straight line in the image obtained in this step Alternatively, it may be replaced with a step of cutting out at least three grid images having the same size and shape.

Further, in the invention according to claim 13, in the third step, Fourier transform is performed in a direction in which the number of grids is counted in the plurality of grid images, and 1 is obtained from a frequency spectrum obtained. It is also possible to replace with the step of counting the number of grids included in the grid image by detecting the peak of the next frequency component.

According to the invention of claim 13, in the third step, Fourier transform is performed in the direction in which the number of grids is counted in the plurality of grid images, and 1 is obtained from a frequency spectrum obtained. Extracting a next frequency component, performing an inverse Fourier transform on the extracted first frequency component, and calculating a phase value distribution in the lattice image from a ratio of a real part and an imaginary part of the result, The phase value distribution may be used to replace the step of counting the number of grids included in the grid image.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings. It should be noted that the present invention can be applied to inspection in an apparatus having an optical system capable of drawing a lattice pattern on an image pickup target surface and an image pickup means, and the present invention is implemented by taking a lens unit inspection apparatus as an example. The form will be described.

FIG. 1 is a block diagram of a lens unit inspection apparatus for explaining the first embodiment of the inspection method of the present invention, in which 1 is a CDD camera as an image pickup means, 2 is a CCD camera 1 and an optical axis A. The lens unit 3 as an optical system installed so as to share the same is a chart used for performance evaluation of the lens unit 2. In this example, the chart 3 is an imaging target. Further, 4a to 4c are lattice patterns drawn on the surface of the chart 3 (described in detail later), 5 is an XYZθ stage for adjusting the position of the chart 3, and 6 is for storing an image from the CCD camera 1. The image memory 7 is an arithmetic unit for processing the image stored in the image memory 6.

FIG. 2 is an explanatory view showing the state of the surface of the chart 3, on the surface of which the lens unit evaluation pattern 15 which is various patterns for evaluating the lens unit is drawn. Lattice patterns 4a to 4c having a constant lattice pitch and lattice direction are drawn in three areas where the lens unit evaluation pattern 15 is not drawn and not on the same straight line.

The grid patterns 4a to 4c may be drawn at four or more places, and at least three places are not on the same straight line, and the grid pitch and the grid direction are constant. If satisfied, it may also be used as the lens unit evaluation pattern 15.

FIG. 3 is a flowchart showing a processing procedure in the lens unit inspection apparatus according to the first embodiment, and FIG.
FIG. 8 is a schematic diagram of lattice images 8a to 8c described later.

The operation of the lens unit inspection device configured as described above will be described below with reference to FIGS. 1, 3 and 4.

First, the first step of FIG. 3 will be described with reference to FIG. First, the focus of the lens unit 2 is substantially aligned with the surface of the chart 3 (focus adjustment 1
01). Next, the magnification of the lens unit 2 is set to the lattice pattern 4a.
Adjust to be suitable for individually imaging ~ 4c
(Magnification adjustment 102). At this time, the magnification and the lattice pattern 4a are set so that the lattice lines of the lattice patterns 4a to 4c can be captured as much as possible within the range that can be resolved by the CCD camera 1.
Set the size of ~ 4c and the number of included grid lines.

In this example, the number of grids included in a plurality of grid images 8a to 8c (see FIG. 4) obtained in the steps described later is counted, and the grid pattern 4a in the optical axis A direction is calculated by the difference between them. Judge the position difference of ~ 4c. Therefore, the grid images 8a to 8c need to be in focus so that the number of grids can be calculated. That is, this example is applicable to the case where the maximum value of the difference in position between the grating patterns 4a to 4c in the optical axis A direction is equal to or less than the depth of focus of the lens unit 2.

The number of grids included in the grid images 8a to 8c is related to the resolution of the positions of the grid patterns 4a to 4c, and the smaller the grid pitch, the higher the resolution of verticality detection. Therefore, the higher the number of grids to be imaged, the higher the resolution. From this fact, it is desirable that each grid line is imaged in a larger number within the resolution of the CCD camera 1 when the grid patterns 4a to 4c are imaged. For example, when the number of pixels in the direction perpendicular to the lattice lines of the lattice images 8a to 8c is 512, the number of lattices is theoretically 256.
The book can be disassembled. Actually, it is desirable that the resolution is about 128 to 170, which has a little margin.

The XYZθ stage 5 is used to move the chart 3 in a direction substantially perpendicular to the optical axis A, and the three grid patterns 4a to 4c are individually imaged to obtain three grid images as shown in FIG. 8a to 8c are obtained (grid image capturing 1
03). After that, the focus and the magnification of the lens unit 2 are kept constant until the image capturing is completed. The obtained lattice images 8a to 8c are stored in the image memory 6. Although the chart 3 is moved here, CC
The D camera 1 may be moved.

Next, the second step of FIG. 3 will be described with reference to FIGS. In the same step, the arithmetic unit 7 calculates the number of grids in a direction substantially perpendicular to the grid lines in the three grid images 8a to 8c stored in the image memory 6. The arithmetic unit 7 calculates the number of grids, for example, by the method described below.

First, the following binarization processing is performed on the lattice images 8a to 8c (binarization processing 104). That is, the threshold value of the brightness distribution is determined in the grid images 8a to 8c.
The threshold may be the average value of the brightness distribution of the lattice images 8a to 8c. Pixels higher than the threshold are bright areas, and pixels lower than the threshold are dark areas.

Through the above processing, the lattice images 8a to 8c are made into binary images of bright and dark areas. When the binarization process is performed, the luminance distribution becomes a perfect rectangular wave. The number of grids is calculated by counting the number of the rectangular waves (rectangular wave count 105).

Next, the third step of FIG. 3 will be described with reference to FIGS. In the arithmetic unit 7,
By comparing the number of grids included in the three grid images 8a to 8c obtained in the previous step, each grid image 8a
To 8c, the relative positional relationship of the lattice patterns 4a to 4c in the optical axis A direction is determined (comparison of the number of lattices 10
6). For example, the number of grids in the grid images 8a and 8b corresponding to the grid patterns 4a and 4b is 128,
If the number is 129, it is determined that the lattice pattern 4a is closer to the CCD camera 1 than the lattice pattern 4b.

As described above, according to the lens unit inspecting apparatus of the first embodiment, the apparatus having the optical system and the image pickup apparatus detects the position of the image pickup target surface in the optical axis direction of the optical system or the image pickup means. It is possible to detect the perpendicularity of the image pickup target surface with respect to the optical axis of the optical system or the image pickup means without adding the above device.

Further, in the lens unit inspection apparatus according to the first embodiment, the vertical direction including the inclination of the apparent image pickup target surface due to the shake of the stage movement in the optical axis A direction at the time of picking up the lattice images 8a to 8c. The degree can be detected. Therefore, even when the stage is moved during the image pickup due to the large image pickup target, the image pickup target surface with respect to the optical axis of the optical system or the image pickup means in consideration of the apparent inclination of the image pickup target surface due to the stage movement. The verticality of can be detected.

The verticality of the imaging target surface obtained by the inspection method of the first embodiment may be used to adjust the verticality of the imaging target surface by means such as adjusting the inclination of the XYZθ stage 5. It is possible.

Next, a second embodiment of the present invention will be described by taking the lens unit inspection device shown in FIG. 1 as an example as in the first embodiment. The configuration of the inspection device used in the second embodiment is the same as that used in the first embodiment.

FIG. 5 is a flow chart showing the processing procedure of the second embodiment, FIG. 6 is an explanatory diagram of a whole image 9 and lattice images 8a to 8c cut out from the whole image 9 described later, and FIG.
Is a waveform diagram showing an example of the waveform of the luminance distribution of one line in the direction substantially perpendicular to the lattice lines in the lattice images 8a to 8c, and FIG. 8 is obtained when Fourier transform is applied to the luminance distribution of FIG. FIG. 3 is a schematic diagram of a power spectrum which is a sum of squares of a real part and an imaginary part of a frequency spectrum.

The operation of the inspection apparatus used in the second embodiment will be described below with reference to FIGS. 1 and 5 to 8.

First, the first step in FIG. 5 will be described with reference to FIG. First, focus the lens unit 2 on the surface of the chart 3 (focus adjustment 2
01). As in the case of the first embodiment, the maximum value of the difference in the positions of the grating patterns 4a to 4c applicable to this embodiment in the optical axis A direction is equal to or less than the depth of focus of the lens unit 2. Next, the magnification of the lens unit 2 is adjusted to be appropriate for simultaneously capturing images of the lattice patterns 4a to 4c (magnification adjustment 202). Also in this case, as in the first embodiment, the resolution of the verticality detection becomes higher if the grid lines of the grid patterns 4a to 4c can be captured as much as possible within the range where the CCD camera 1 can resolve them. The grating patterns 4a to 4 are simultaneously imaged using the CCD camera 1 (entire image imaging 203). The obtained whole image 9 (see FIG. 6) is stored in the image memory 6.

Next, referring to FIGS. 1 and 6, the second of FIG.
The steps will be described. In the arithmetic unit 7, the lattice pattern 4 is calculated from the entire image 9 stored in the image memory 6.
Regions a to 4c are individually cut out in the same size and in the same shape to obtain grid images 8a to 8c (see FIG. 6) (grid image cutout 204). FIG. 6 shows an example in which the grid images 8a to 8c are obtained by cutting out into rectangular areas.
The shape of the region is not limited to the rectangle.
The obtained lattice images 8a to 8c are stored in the image memory 6.

Next, referring to FIG. 1 and FIG. 6, the third of FIG.
The steps will be described. First, in each of the three lattice images 8a to 8c stored in the image memory 6, the number of lattices in the direction substantially perpendicular to the lattice line is calculated by the arithmetic unit 7. As described in the second step of the first embodiment, the arithmetic unit 7 may use the binarization process to count the number of grids.

Here, as another method, the grid images 8a ...
A method using each power spectrum of 8c will be described. Lattice image 8a stored in the image memory 6
The processing to be described later is performed in the arithmetic unit 7 with respect to each of 8c.

That is, FIG. 7 shows an example of the waveform of the luminance distribution of one line in the direction substantially perpendicular to the grid lines in the grid images 8a to 8c. When a Fourier transform is applied to this luminance distribution, a frequency spectrum is obtained (Fourier transform processing 205). 8 is a schematic diagram of a power spectrum which is a sum of squares of a real part and an imaginary part of a frequency spectrum obtained when a Fourier transform is applied to the luminance distribution of FIG. The shaded component of the spectrum is the primary frequency component representing the primary harmonic component of the original waveform. The coordinates of the peak position of the primary frequency component, that is, the distance from the origin O to the peak position P corresponds to the number of grids included in the original grid images 8a to 8c. This origin O
The number of grids is calculated by detecting the distance from to the peak position P (peak position detection of primary frequency component 20
6).

Next, referring to FIGS. 1 and 6, the fourth line of FIG.
The steps will be described. The first in the fourth step
Similar to the third step of the embodiment, the three lattice images 8a obtained in the third step are calculated in the arithmetic unit 7.
By comparing the number of grids included in 8a to 8c, the grid patterns 4a to 4c corresponding to the grid images 8a to 8c are compared.
The relative positional relationship in the optical axis A direction is determined (comparison of the number of grids 207). For example, the number of grids in the grid images 8a and 8b corresponding to the grid patterns 4a and 4b is 12 respectively.
When there are 8 and 129, it is determined that the lattice pattern 4a is closer to the CCD camera 1 than the lattice pattern 4b.

As described above, according to the lens unit inspecting apparatus of the second embodiment, the apparatus having the optical system and the image pickup means detects the position of the image pickup target surface in the optical axis direction of the optical system or the image pickup means. It is possible to detect the perpendicularity of the image pickup target surface with respect to the optical axis of the optical system or the image pickup means without adding the above device. In addition, the processing time can be shortened because there is no movement of the stage or the like when capturing the lattice image.

It should be noted that the verticality of the imaging target surface is adjusted by means such as adjusting the inclination of the XYZθ stage 5 using the verticality of the imaging target surface obtained by the inspection method of the second embodiment. Is also possible.

Next, a third embodiment of the present invention will be described by taking the lens unit inspecting apparatus shown in FIG. 1 as an example as in the first embodiment. FIG. 9 is a flowchart showing a processing procedure in the lens unit inspection device of the third embodiment. The operation of the device used in the third embodiment will be described below with reference to FIGS. 1, 4, and 6 to 9.

First, the first step of FIG. 9 will be described with reference to FIGS. 1 and 4. In the first step, the grid patterns 4a to 4c on the chart 3 are transferred to the CCD camera 1
Are imaged using the grid images 8a to 8c as shown in FIG.
To get Specifically, as described in the first step of the first embodiment, first, the focus of the lens unit 2 is adjusted to substantially the surface of the chart 3 (focus adjustment 301).
Next, the magnification of the lens unit 2 is set to the lattice patterns 4a to 4c.
Is adjusted so as to be appropriate for individual image pickup (magnification adjustment 302).

Furthermore, the respective grid patterns 4a-4
Lattice images 8a to 8c are obtained by individually picking up images of c, and are stored in the image memory 6 (imaging of lattice image 303).
Alternatively, as described in the first and second steps of the second embodiment, first, the focus of the lens unit 2 is substantially adjusted to the surface of the chart 3 (focus adjustment 301). Next, the magnification of the lens unit 2 is adjusted to be appropriate for simultaneously capturing images of the grating patterns 4a to 4c (magnification adjustment 30
2). Next, the lattice patterns 4a to 4c are simultaneously imaged (entire image imaging 304). Lattice images 8a to 8c are obtained by cutting out the portions including the respective lattice patterns 4a to 4c from the obtained whole image 9 (see FIG. 6), and the lattice images 8a to 8c are stored in the image memory 6 (grid image cutout 305).

As in the case of the first and second embodiments, the grid pattern 4 to which the present embodiment can be applied.
The maximum value of the difference between the positions of a to 4c in the optical axis A direction is equal to or less than the depth of focus of the lens unit 2.

Next, referring to FIG. 1 and FIG.
The steps will be described. First, in each of the three lattice images 8a to 8c stored in the image memory 6, the number of lattices in the direction substantially perpendicular to the lattice line is calculated by the arithmetic unit 7. As described in the second step of the first embodiment, the arithmetic unit 7 may use the binarization process to count the number of grids, and as described in the third step of the second embodiment. Alternatively, the number of grids may be counted by using the power spectrum of each of the grid images 8a to 8c. Here, as another method, a method using phase information processing using Fourier transform on the lattice images 8a to 8c will be described.

That is, with respect to each of the lattice images 8a to 8c stored in the image memory 6, the arithmetic unit 7 performs the processing described later. FIG. 7 is an example of the waveform of the luminance distribution of one line in the direction substantially perpendicular to the grid lines in the grid images 8a to 8c. When a Fourier transform is applied to this, a frequency spectrum is obtained (Fourier transform processing 306). FIG. 8 is a schematic diagram of a power spectrum which is a sum of squares of a real part and an imaginary part of a frequency spectrum obtained when Fourier transform is applied to the luminance distribution of FIG. Of these, only the first-order frequency component (corresponding to the shaded area in FIG. 8) that represents the first-order harmonic component of the original waveform is extracted (first-order frequency component extraction 307), and the inverse Fourier transform is performed. A primary harmonic waveform of the original waveform and a waveform having a π / 2 phase shift from the real part waveform are obtained in the imaginary part (inverse Fourier transform processing 308). By taking the arctangent of the imaginary part divided by the real part, the phase value of the first-order harmonic wave of the original waveform at each pixel is obtained (phase value calculation 309).

Next, the amount of change in the phase value in each of the grid images 8a to 8c is calculated (calculation of the amount of change in the phase value 31
0). If the phase value change amount is divided by 2π, the lattice images 8a to 8
The number of grids included in c can be calculated with a precision below the decimal point (grid number calculation 311), and a more accurate value can be obtained as compared with the method using the binarization process.

Next, referring to FIG. 1 and FIG.
The steps will be described. First, the XYZθ stage 5 is used to move the chart 3 in a direction approaching the CCD camera 1 on the optical axis A. The moving distance is C within the range of the depth of focus.
It is assumed that the number of grids included in the imaging range of the CD camera 1 changes (chart movement 312). Next, with respect to the chart 3 after moving in the direction of the optical axis A, the focus and the magnification of the lens unit 2 remain constant, and again the grid images 8a to 8c are processed in the same manner as in the first step and the second step. Acquisition (grid image imaging 313, or whole image imaging 314 and grid image cutout 315), and calculation of the number of grids
(Fourier transform processing 316, primary frequency component extraction 317, inverse Fourier transform processing 318, phase value calculation 319, phase value change amount calculation 320, lattice number calculation 321) are performed.

When calculating the number of grids, the method of calculating the number of grids by the binarization processing described in the first embodiment or the method of calculating the number of grids using the peak position of the power spectrum described in the second embodiment. When using, the grid image 8a
It is necessary to move the chart 3 so that the amount of change in the number of lattices included in 8c is 1 or more. However,
When the method for calculating the number of grids using phase information processing described in the third embodiment is used, even if the amount of change in the number of grids included in the grid images 8a to 8c is less than one, it can be detected. The movement distance can be reduced.

Here, the number of grids corresponding to each grid pattern 4a to 4c calculated from the image obtained after the movement of the chart 3 is set to H1a to H1c, and calculated from the image obtained before the movement of the chart 3. Each lattice pattern 4a-4c
The number of grids corresponding to is set to H0a to H0c, and the chart 3
The moving distance of L is set to L, and in the arithmetic unit 7, the change rates Ra to Rc of the number of grids corresponding to the respective grid patterns 4a to 4c with respect to the position change of the chart 3 in the optical axis A direction according to the following equation (Equation 1), and The average R of Ra to Rc is calculated (lattice number change rate calculation 322).

[0067]

## EQU1 ## Ra = (H1a-H0a) / L Rb = (H1b-H0b) / L Rc = (H1c-H0c) / L R = (Ra + Rb + Rc) / 3 Here, for all lattice patterns 4a to 4c Processing was performed and the average was taken, but the grid patterns 4a-4
It suffices to only perform the process for at least one of c. The chart 3 may be moved away from the CCD camera 1, and the chart 3 may be moved a plurality of times to calculate the number of grids Hna, Hnb, and Hnc corresponding to the grid patterns 4a to 4c (n: integer). Then, R may be obtained by applying the least square method to the relationship of the moving distance Ln (n: integer) of the chart 3 at that time and calculating an average slope.

Next, referring to FIG. 1 and FIG.
The steps will be described. In the arithmetic unit 7, the number of grids included in the three grid images 8a to 8c of the chart 3 before the movement obtained in the second step is set to H0a to H0.
Let be c. In this example, consider the case where H0a is used as a reference.
Of course, either of the other two may be used as the reference. The relative positions Pb and Pc in the optical axis A direction in other lattice patterns with respect to the reference lattice patterns 4a to 4c are calculated by
Calculation is performed according to (Equation 2) (calculation of relative position 323).

[0069]

## EQU2 ## Pb = (H0b-H0a) / R Pc = (H0c-H0a) / R By calculating Pb and Pc in this way, the grid patterns 4a-4c corresponding to the grid images 8a-8c The relative positional relationship in the optical axis A direction is quantitatively determined.

As described above, according to the lens unit inspecting apparatus of the third embodiment, the apparatus having the optical system and the image pickup means can detect the position of the image pickup target surface in the optical axis direction of the optical system or the image pickup means. It is possible to quantitatively detect the perpendicularity of the image pickup target surface with respect to the optical axis of the optical system or the image pickup means without adding a device.

The XYZθ stage 5 is used by utilizing the perpendicularity of the image pickup target surface obtained by the inspection method of the third embodiment.
It is also possible to adjust the verticality of the imaging target surface by means such as adjusting the inclination of.

The fourth embodiment of the present invention will be described below. FIG. 10 is a block diagram of a magnetic recording track inspection apparatus for explaining the fourth embodiment, in which 1 is a CCD camera as an image pickup means, and 12 is an optical axis A shared with the CCD camera 1. A microscope as an optical system, 13 is a reference gauge on which a predetermined pattern to be described later is drawn, 14 is a sample setting table on which the reference gauge 13 and a magnetic tape (not shown) are installed, and 4a to 4c are the surfaces of the reference gauge 13 5 is an XYZθ stage for adjusting the position of the reference gauge 13, 6 is an image memory for storing an image from the CCD camera 1, and 7 is an image memory 6. It is an arithmetic unit that performs processing on an existing image.

FIG. 11 is an explanatory view showing the state of the surface of the reference gauge 13, and lattice patterns 4a to 4c having a constant lattice pitch and lattice direction are drawn at three positions on the surface of the reference gauge 13 which are not on the same straight line. Has been. The lattice pattern 4a
4c may be drawn in four or more places. Further, when the reference gauge 13 is installed on the sample installation table 14, it is installed so that the surface thereof is substantially at the same position as the surface of the magnetic tape when the magnetic tape is installed on the sample installation table 14. Specifically, the reference gauge 13 is a glass plate on which the lattice patterns 4a to 4c are drawn. Also, when installing the magnetic tape, install a glass plate with nothing drawn on the surface on the sample installation base 14,
A structure in which a magnetic tape is installed on top of it is adopted.
By managing the thickness of the glass plate for installing the reference gauge 13 glass plate and the magnetic tape, and the flatness,
The surface of the reference gauge 13 and the surface of the magnetic tape are substantially aligned.
Of course, the Z stage of the XYZθ stage 5 may be used and the position adjustment in the optical axis A direction may be performed so that the surface positions of both the reference gauge 13 and the magnetic tape match.

FIG. 12 is a flow chart showing a processing procedure in the magnetic recording track inspecting apparatus according to the fourth embodiment. The magnetic recording track inspecting apparatus configured as described above will be described below with reference to FIGS. The operation will be described with reference to FIGS.

First, the first step in FIG. 12 will be described with reference to FIG. As described above, by installing the reference gauge 13 on the sample installation table 14, the grid pattern 4a
4c are installed in a plane that substantially matches the installation plane of the magnetic tape (reference gauge installation 401). The range considered to be substantially coincident is a range in which the amount of influence on the inspection accuracy in the magnetic recording track due to the difference between the position of the surface of the reference gauge 13 in the optical axis A direction and the surface of the magnetic tape when the magnetic tape is installed can be ignored. And it is sufficient.

Next, the second step of FIG. 12 will be described with reference to FIG. Reference gauge for focus of microscope 12
The surface of 13 is roughly adjusted (focus adjustment 402), and the magnification of the microscope 12 is adjusted so as to be appropriate for individually imaging the lattice patterns 4a to 4c (magnification adjustment 403). At this time, the magnification is set so that the lattice lines of the lattice patterns 4a to 4c can be captured as much as possible within the range where the CCD camera 1 can resolve. In this example, the number of grids included in the grid images 8a to 8c (see FIG. 4) obtained in the steps described below is counted, and the difference between the positions of the grid patterns 4a to 4c in the optical axis A direction is counted by the difference. To judge. Therefore, the grid images 8a to 8c need to be in focus so that the number of grids can be calculated.

That is, in this example, each lattice pattern 4a
The maximum value of the position difference in the optical axis A direction of 4c is a microscope.
It is applicable when the depth of focus is 12 or less.
For example, when the depth of focus of the microscope 12 used is 0.32 mm, the optical axis A of the grating patterns 4a to 4c applicable in this example is used.
The maximum position difference in the direction is 0.32 mm. Also,
The number of grids included in the grid images 8a to 8c is related to the resolution of the positions of the grid patterns 4a to 4c, and the smaller the grid pitch, the higher the resolution of verticality detection. Therefore, the higher the number of grids to be imaged, the higher the resolution.

From this, it is desirable to pick up a large number of grid lines within the resolution of the CCD camera 1 for each grid line when the grid patterns 4a to 4c are picked up. For example, when the number of pixels in the direction perpendicular to the grid lines of the grid images 8a to 8c is 512 pixels, theoretically, the number of grids can be decomposed into 256. Actually, 128 to 170 lines, which has a little margin in resolution, is desirable.

A reference gauge 13 using the XYZθ stage 5
Is moved in a direction substantially perpendicular to the optical axis A, and three lattice patterns 4a to 4c are individually imaged to obtain three lattice images 8a to 8c as shown in FIG. ). After that, use the microscope 12 until the image capture is complete.
The focus and magnification are constant. The obtained lattice images 8a to 8c are stored in the image memory 6. Although the reference pattern 13 is moved here, the CCD camera 1 may be moved.

Next, referring to FIGS. 10 and 4, the third part of FIG.
The steps will be described. First, in the three lattice images 8a to 8c stored in the image memory 6, the arithmetic unit 7 calculates the number of lattices in the direction substantially perpendicular to the lattice lines. The arithmetic unit 7 calculates the number of grids, for example, by the method described below. First, binarization processing is performed on the lattice images 8a to 8c (binarization processing 405).

The binarization process is performed as follows. That is, the threshold value of the brightness distribution is determined in the grid images 8a to 8c. The threshold may be the average value of the brightness distribution of the lattice images 8a to 8c. Pixels higher than the threshold are bright areas, and pixels lower than the threshold are dark areas. Through the above processing, the lattice images 8a to 8c are made into binary images of a bright portion and a dark portion.

By performing this binarization process, the luminance distribution becomes a perfect rectangular wave. Then, the number of grids is calculated by counting the number of rectangular waves (count of rectangular wave number 406).

Next, the fourth step of FIG. 12 will be described with reference to FIGS. 10 and 4. In the arithmetic unit 7,
By comparing the number of grids included in the three grid images 8a to 8c obtained in the third step, the optical axes A of the grid patterns 4a to 4c corresponding to the grid images 8a to 8c are compared.
The relative positional relationship in the directions is judged (comparison of the number of grids 407).
For example, the numbers of grids in the grid images 8a and 8b corresponding to the grid patterns 4a and 4b are 128 and 129, respectively.
If it is a book, it is determined that the lattice pattern 4a is closer to the CCD camera 1 than the lattice pattern 4b.

As described above, according to the magnetic recording track inspection apparatus of the fourth embodiment, the lattice pattern has the image pickup target surface as in the apparatus having the optical system and the image pickup means for picking up and inspecting the magnetic recording track pattern. Even if it is not possible to draw the image above, by using the reference gauge, the optical system or the image pickup means can be detected without adding a device for detecting the position of the image pickup target surface in the direction of the optical axis of the optical system or the image pickup means. It is possible to detect the perpendicularity of the imaging target surface with respect to the optical axis.

Further, in the magnetic recording track inspection apparatus according to the fourth embodiment, the inclination of the apparent imaging target surface due to the shake in the optical axis A direction due to the stage movement during the imaging of the lattice images 8a to 8c is included. The verticality can be detected. Therefore, even when the stage moves during imaging due to the large image pickup target surface, the image pickup target with respect to the optical axis of the optical system or the image pickup means in consideration of the apparent inclination of the image pickup target surface due to the stage movement. The perpendicularity of the surface can be detected.

The verticality of the image pickup target surface obtained by the inspection method of the fourth embodiment is used to adjust the tilt of the XYZθ stage 5 and the sample installation table 14 to adjust the image pickup target surface. It is also possible to adjust the verticality.

Next, a fifth embodiment of the present invention will be described. FIG. 13 is a flowchart showing a processing procedure in the magnetic recording track inspection apparatus according to the fifth embodiment, and FIG. 14 is an explanatory diagram of an overall image 9 and lattice images 8a to 8c cut out from the overall image 9 described later.

The structure of the apparatus used in the fifth embodiment is the same as that used in the fourth embodiment. The operation will be described below with reference to FIGS. 7, 8, 10, 13, and 14.

First, the first step in FIG. 13 will be described with reference to FIG. Similar to the first step of the fourth embodiment, by installing the reference gauge 13 on the sample installation table 14, the lattice patterns 4a to 4c are installed in the plane substantially matching the installation surface of the magnetic tape (the reference gauge Installation 501).

Next, the second step in FIG. 13 will be described with reference to FIG. Reference gauge for focus of microscope 12
Approximately match the surface of 13 (focus adjustment 502). As in the case of the fourth embodiment, the maximum value of the positional difference in the optical axis A direction of the grating patterns 4a to 4c applicable in this embodiment is equal to or less than the focal depth of the microscope 12. Then the microscope
The 12 magnifications are adjusted so as to be appropriate for simultaneously imaging the lattice patterns 4a to 4c (magnification adjustment 503). Also in this case, as in the case of the fourth embodiment, the grid pattern 4a is formed.
The resolution of the verticality detection is higher when the lattice line of 4c can be captured by the CCD camera 1 as much as possible. Then, the lattice patterns 4a to 4c are simultaneously imaged by using the CCD camera 1 (entire image imaging 504).
The obtained whole image 9 (see FIG. 14) is stored in the image memory 6.

Next, referring to FIGS. 10 and 14, the third part of FIG.
The steps will be described. In the arithmetic unit 7, the lattice pattern 4 is calculated from the entire image 9 stored in the image memory 6.
Regions a to 4c are individually cut out with the same size and the same shape to obtain lattice images 8a to 8c (grid image segmentation 505). FIG. 14 shows an example in which the grid images 8a to 8c are obtained by cutting out into rectangular areas. The shape of the region is not limited to the rectangle. The obtained lattice images 8a to 8c are stored in the image memory 6.

Next, referring to FIGS. 10 and 14, the fourth part of FIG.
The steps will be described. First, in each of the three lattice images 8a to 8c stored in the image memory 6,
The arithmetic unit 7 calculates the number of grids substantially perpendicular to the grid lines. In the arithmetic unit 7, as shown in the second step of the first embodiment, the number of grids may be counted by using the binarization process.

Here, as another method, grid images 8a-8
c A method using each power spectrum will be described. That is, the processing to be described later is performed in the arithmetic unit 7 for each of the lattice images 8a to 8c stored in the image memory 6. FIG. 7 is an example of the waveform of the luminance distribution of one line in the direction substantially perpendicular to the grid lines in the grid images 8a to 8c. When a Fourier transform is applied to this, a frequency spectrum is obtained (Fourier transform processing 506). FIG. 8 is a schematic diagram of a power spectrum which is the sum of squares of the real part and the imaginary part of the frequency spectrum obtained when Fourier transform is applied to the luminance distribution of FIG. The shaded component of the power spectrum in FIG. 8 is the primary frequency component representing the component of the primary harmonic wave of the original waveform. The coordinates of the peak position of the primary frequency component, that is, the distance from the origin O to the peak position P corresponds to the number of grids included in the original grid images 8a to 8c. The number of grids is calculated by detecting the distance from the origin O to the peak position P (peak position detection 507 of primary frequency component).

Next, referring to FIGS. 10 and 14, the fifth part of FIG.
The steps will be described. 4th in the 5th step
Similar to the fourth step of the embodiment, the arithmetic device 7 corresponds to each of the lattice images 8a to 8c by comparing the number of lattices included in the three lattice images 8a to 8c obtained in the previous step. Optical axis A of the lattice patterns 4a-4c
Judge relative positional relationship in the direction (comparison of the number of grids 5
08). For example, the number of grids in the grid images 8a and 8b corresponding to the grid patterns 4a and 4b is 128, respectively.
If the number is 129, it is determined that the lattice pattern 4a is closer to the CCD camera 1 than the lattice pattern 4b.

In the description of the fifth embodiment, the case where the same reference gauge 13 as that in the fourth embodiment is used is shown. However, as shown in FIG. 15, a lattice pattern is formed in a wide area on the surface of the reference gauge 13. You may use what was drawn.

As described above, according to the magnetic recording track inspecting apparatus of the fifth embodiment, the grating pattern is an object to be imaged, as in an apparatus having an optical system and an imaging means for imaging and inspecting the pattern of the magnetic recording track. Even if the image cannot be drawn on the surface, the optical system or the image pickup means can be obtained by using the reference gauge without adding a device for detecting the position of the image pickup target surface in the direction of the optical axis of the optical system or the image pickup means. It is possible to detect the perpendicularity of the image pickup target surface with respect to the optical axis of. Further, the processing time can be shortened because the stage or the like does not move when the lattice image is captured.

It should be noted that by using the perpendicularity of the image pickup target surface obtained by the inspection method of the fifth embodiment, the image pickup target surface is adjusted by means such as adjusting the inclination of the XYZθ stage 5 and the inclination of the sample mounting table 14. It is also possible to adjust the verticality of.

Next, a sixth embodiment will be described. Fig. 16
9 is a flowchart showing a processing procedure of a magnetic recording track inspection apparatus according to a sixth embodiment. The configuration of the device used in the sixth embodiment is the same as that used in the fifth embodiment. The operation will be described below with reference to FIGS. 4, 7, 8, 10, 14, and 16.

First, the first step in FIG. 16 will be described with reference to FIG. By installing the reference gauge 13 on the sample installation base 14 as in the first step of the fourth embodiment, the grid patterns 4a to 4c are installed in a plane substantially matching the installation surface of the magnetic tape (of the reference gauge). Installation 601).

Next, the second step of FIG. 16 will be described with reference to FIG. Focus the microscope 12 to the reference gauge 13
The lattice patterns 4a to 4c on the above are imaged using the CCD camera 1 to obtain lattice images 8a to 8c as shown in FIG. Specifically, as described in the second step of the fourth embodiment, first, the focus of the microscope 12 is approximately adjusted to the surface of the reference gauge 13 (focus adjustment 602). Then the microscope 12
Is adjusted so that it is appropriate for individually imaging the lattice patterns 4a to 4c (magnification adjustment 603). Next, the lattice patterns 8a to 8c are individually imaged to obtain lattice images 8a to 8c, which are stored in the image memory 6.
(Grating image 604).

Alternatively, as described in the second and third steps of the fifth embodiment, the focus of the microscope 12 is first adjusted to the surface of the reference gauge 13 (focus adjustment 602). Next, the magnification of the microscope 12 is adjusted so as to be appropriate for simultaneously imaging the lattice patterns 4a to 4c (magnification adjustment 603).
Next, the lattice patterns 4a to 4c are simultaneously imaged (entire image 605). Lattice images 8a to 8c are obtained by cutting out the portion including the lattice patterns 4a to 4c from the obtained whole image 9 (see FIG. 14) and stored in the image memory 6.
(Cut out the grid image 606).

As in the case of the fourth or fifth embodiment, the maximum value of the positional difference in the optical axis A direction of the grating patterns 4a to 4c applicable to this embodiment is the maximum depth of focus of the microscope 12. It is the following.

Next, referring to FIG. 10 and FIG.
The steps will be described. First, in each of the three lattice images 8a to 8c stored in the image memory 6,
The arithmetic unit 7 calculates the number of grids substantially perpendicular to the grid lines. In the arithmetic unit 7, as shown in the third step of the fourth embodiment, the number of grids may be counted by using the binarization process. Further, as shown in the fourth step of the fifth embodiment, the number of grids may be counted by using the power spectrum of each of the grid images 8a to 8c.

Here, as another method, the grid images 8a to 8 are used.
A method using phase information processing using Fourier transform for c will be described. First, for each of the lattice images 8a to 8c stored in the image memory 6, the arithmetic unit 7
The processing described later is performed. FIG. 7 shows lattice images 8a-8.
It is an example of the waveform of the luminance distribution of one line in a direction substantially perpendicular to the grid line in c. If a Fourier transform is applied to this, a frequency spectrum is obtained (Fourier transform processing 6
07). FIG. 8 is a schematic diagram of a power spectrum which is the sum of squares of the real part and the imaginary part of the frequency spectrum obtained when Fourier transform is applied to the luminance distribution of FIG. Only the primary frequency component (corresponding to the shaded area in FIG. 8) representing the primary harmonic component of the original waveform is extracted from this frequency spectrum (extraction of primary frequency component 608). When the inverse Fourier transform is performed, a primary harmonic waveform of the original waveform is obtained in the real part, and a waveform having a π / 2 phase shift from the real part waveform is obtained in the imaginary part (inverse Fourier transform processing 609). When the arctangent of the imaginary part divided by the real part is taken, the phase value of the first-order harmonic wave of the original waveform at each pixel is obtained (phase value calculation 610).

Next, the amount of change in the phase value in each of the lattice images 8a to 8c is calculated (calculation of the amount of change in the phase value 61
1). Since the amount of change in phase value is 2π, which corresponds to one lattice, the number of lattices included in the lattice images 8a to 8c can be calculated with a precision below the decimal point by dividing the amount of phase change by 2π (the number of lattices calculation 612). ). Therefore, it is possible to obtain a more accurate value than the method using the binarization processing.

Next, referring to FIG. 10 and FIG.
The steps will be described. First, XYZθ stage 5
Is used to move the reference gauge 13 in the direction approaching the CCD camera 1 in the direction of the optical axis A (reference gauge movement 613). The movement distance is such that the number of grids included in the imaging range of the CCD camera 1 changes within the range of the depth of focus. Specifically, it may be about several tens of microns. Next, with respect to the reference gauge 13 after moving in the direction of the optical axis A, the focus and magnification of the microscope 12 remain constant, and again, the grid images 8a to 8c are acquired in the same manner as in the second step and the third step ( The image 614 of the lattice image, or the image 615 of the whole image and the segmentation 616 of the lattice image. And calculation of the number of grids (Fourier transform processing 61
7, primary frequency component extraction 618, inverse Fourier transform processing 61
9, phase value calculation 620, phase value change amount calculation 621, number of grids calculation 622) are performed.

When calculating the number of grids, the method of calculating the number of grids by the binarization processing shown in the fourth embodiment or the method of calculating the number of grids using the peak position of the power spectrum described in the fifth embodiment is used. If used, grid image 8a
It is necessary to move the reference gauge 13 so that the amount of change in the number of lattices included in 8c is 1 or more.

However, when the method of calculating the number of grids using the phase information processing described in the sixth embodiment is used, the amount of change in the number of grids included in the grid images 8a to 8c can be detected even if it is less than one. Becomes Therefore, the moving distance of the reference gauge 13 is reduced.

Here, the number of grids corresponding to the respective grid patterns 4a to 4c calculated from the image obtained after the movement of the reference gauge 13 is set to H1a to H1c, and calculated from the image obtained before the movement of the reference gauge 13. Each grid pattern 4a-4
The number of grids corresponding to c is H0a to H0c, and the moving distance of the reference gauge 13 is L. In the arithmetic unit 7, the change rate Ra of the number of grids corresponding to each grid pattern 4a to 4c with respect to the position change of the reference gauge 13 in the optical axis A direction.
~ Rc, and the average R of Ra to Rc is calculated according to the formula (Equation 3) (calculation rate of the number of lattice lines 623).

[0110]

## EQU3 ## Ra = (H1a-H0a) / L Rb = (H1b-H0b) / L Rc = (H1c-H0c) / L R = (Ra + Rb + Rc) / 3 Here, for all the lattice patterns 4a to 4c. Processing was performed and the average was taken, but the grid patterns 4a-4
It suffices to only perform the process for at least one of c. The moving direction of the reference gauge 13 may be a direction away from the CCD camera 1. Alternatively, the reference gauge 13 is moved a plurality of times to calculate the number of grids corresponding to the grid patterns 4a to 4c Hna, Hnb, Hnc (n: integer)
And the moving distance Ln (n: integer) of the reference gauge 13 at that time
The above R may be obtained by applying the least squares method to the relationship to calculate the average slope.

Next, referring to FIG. 10 and FIG.
The steps will be described. In the arithmetic unit 7, the number of grids included in the three grid images 8a to 8c of the reference gauge 13 before movement obtained in the third step is set to H0a to H0.
0c. Consider the case where H0a is used as a reference. Of course, either of the other two may be used as the reference. Relative positions Pb and Pc in the optical axis A direction of the other lattice patterns with respect to the reference lattice patterns 4a to 4c are calculated according to the equation (4) (calculation of relative position 624).

[0112]

## EQU00004 ## Pb = (H0b-H0a) / R Pc = (H0c-H0a) / R By calculating Pb and Pc in this way, the grid patterns 4a-4c corresponding to the grid images 8a-8c The relative positional relationship in the optical axis A direction is quantitatively determined.

As described above, according to the magnetic recording track inspection apparatus of the sixth embodiment, in the apparatus having the optical system and the image pickup means for picking up and inspecting the magnetic recording track pattern, the grating pattern is formed on the image pickup target surface. Even when it is not possible to draw, by using the reference gauge, it is possible to detect the position of the imaging target surface in the optical axis direction of the optical system or the imaging means without adding a device for detecting the position of the optical system or the optical axis of the imaging means. It is possible to quantitatively detect the verticality of the imaging target surface.

The verticality of the image pickup target surface obtained by the inspection method of the sixth embodiment is used to adjust the tilt of the XYZθ stage 5 and the sample installation table 14 to adjust the image pickup target surface. It is also possible to adjust the verticality.

[0115]

As described above, according to the inspection method for the apparatus having the optical system and the image pickup means according to the present invention, the apparatus having the optical system and the image pickup means is provided in the optical system or the optical axis direction of the image pickup means. It is possible to detect the perpendicularity of the image pickup target surface with respect to the optical axis of the optical system or the image pickup means without adding a device for detecting the position of the image pickup target surface.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a lens unit inspection device for explaining an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an example of a chart in the present embodiment.

FIG. 3 is a flowchart showing a processing procedure in the first embodiment of the present invention.

FIG. 4 is a schematic diagram of a lattice image in this embodiment.

FIG. 5 is a flowchart showing a processing procedure in the second embodiment of the present invention.

FIG. 6 is an explanatory diagram of cutting out a lattice image in the present embodiment.

FIG. 7 is a diagram showing an example of a luminance distribution of one line with a lattice image in the present embodiment.

FIG. 8 is a diagram showing an example of a power spectrum as a result of performing a Fourier transform on a one-line luminance distribution of a grid image in the present embodiment.

FIG. 9 is a flowchart of a processing procedure according to the third embodiment of the present invention.

FIG. 10 is a configuration diagram of a magnetic recording track inspection apparatus for explaining an embodiment of the present invention.

FIG. 11 is a diagram showing a pattern example on a reference gauge in the present embodiment.

FIG. 12 is a flowchart showing a processing procedure in the fourth embodiment of the present invention.

FIG. 13 is a flowchart showing a processing procedure in the fifth embodiment of the present invention.

FIG. 14 is an explanatory diagram of clipping a lattice image according to the present embodiment.

FIG. 15 is a diagram showing a pattern example on a reference gauge in the present embodiment.

FIG. 16 is a flowchart showing a processing procedure in the sixth embodiment of the present invention.

FIG. 17 is a configuration diagram of an apparatus used in a conventional tilt amount measuring method.

[Explanation of symbols]

1 ... CCD camera, 2 ... Lens unit, 3 ... Chart, 4a, 4b, 4c ... Lattice pattern, 5 ... XY
Zθ stage, 6 ... Image memory, 7 ... Arithmetic unit,
8a, 8b, 8c ... Lattice image, 9 ... Whole image, 12 ...
Microscope, 13 ... Reference gauge, 14 ... Specimen mount, 15 ...
Lens unit evaluation pattern.

Continuation of the front page (56) References JP-A-4-177110 (JP, A) JP-A-8-313230 (JP, A) JP-A-58-169010 (JP, A) JP-A-4-148814 (JP , A) JP-A-9-69973 (JP, A) JP-A-8-213797 (JP, A) JP-A-3-123292 (JP, A) JP-A-4-65993 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01B 11/26 H04N 5/232

Claims (16)

(57) [Claims] 1. A method of individually imaging a grating pattern having a constant grating pitch and a fixed grating direction, which is installed on at least three positions that are not on the same straight line on the imaging target surface, without changing the focus and magnification of the imaging means. A first step of obtaining a plurality of grid images including only the grid pattern, a second step of counting the number of grids included in the plurality of grid images in a predetermined direction, and the second step A third step of inspecting the perpendicularity of the image pickup target surface with respect to the optical axis of the image pickup means by comparing the number of lattices in the plurality of lattice images obtained in An inspection method in an apparatus having an imaging means. 2. A first step of capturing an image of a lattice pattern having a constant lattice pitch and lattice direction, which is installed on an image pickup target surface, by using an image pickup means, and an image obtained in the first step. Not on the same line,
The second step of cutting out at least three lattice images having the same size and shape, the third step of counting the number of lattices included in the lattice image in a predetermined direction, and the third step A fourth step of inspecting the perpendicularity of the image pickup target surface with respect to the optical axis of the image pickup means by comparing the number of lattices of the respective lattice images with each other, and the optical system and the image pickup means. Inspection method in equipment. 3. An individual image of a lattice pattern having a constant lattice pitch and a constant lattice direction, which is installed on at least three positions which are not on the same straight line on the image pickup target surface, without changing the focus and magnification of the image pickup means. According to the first step of obtaining a plurality of lattice images including only the lattice pattern, Fourier transform is performed in the direction in which the number of lattices is counted in the plurality of lattice images, and a primary frequency is obtained from the obtained frequency spectrum. The second step of counting the number of grids included in the grid image by detecting the peak of the component and the number of grids in the plurality of grid images obtained in the second step are respectively compared to obtain the image. A third step of inspecting the perpendicularity of the surface to be imaged with respect to the optical axis of the means, and an optical system and an imaging means. Inspection method for equipment. 4. An individual image of a lattice pattern having a constant lattice pitch and a constant lattice direction, which is installed on at least three positions which are not on the same straight line on the image pickup target surface, without changing the focus and magnification of the image pickup means. According to the first step of obtaining a plurality of lattice images including only the lattice pattern, Fourier transform is performed in the direction in which the number of lattices is counted in the plurality of lattice images, and a primary frequency is obtained from the obtained frequency spectrum. A second step of extracting the component, and a third step of performing an inverse Fourier transform on the extracted first-order frequency component and calculating a phase value distribution in the lattice image from the ratio of the real part and the imaginary part of the result. And a fourth step of counting the number of grids included in the grid image using the phase value distribution, and the number of grids in the plurality of grid images obtained in the fourth step. By people comparison, inspection method in an apparatus having an optical system and an imaging device characterized by having a fifth step of inspecting the perpendicularity of the imaging target surface with respect to the optical axis of the imaging means. 5. An individual image of a lattice pattern having a constant lattice pitch and a constant lattice direction, which is installed on at least three positions which are not on the same straight line on the image pickup target surface, without changing the focus and magnification of the image pickup means. The first step of obtaining a plurality of grid images including only the grid pattern, the second step of counting the number of grids included in the plurality of grid images in a predetermined direction, and the first step and By performing the second step by setting the image pickup target surface at a plurality of positions in the image pickup unit in the optical axis direction, it is possible to adjust the number of the lattices with respect to a position change of the image pickup target surface in the optical axis direction of the image pickup unit. Of the number of grids in the plurality of grid images obtained in the third step of obtaining the change rate and the second step, the installation position of the image pickup target surface in the image pickup means in the optical axis direction is From the difference in the number of grids obtained from all of the plurality of grid images when it is constant, the degree of perpendicularity of the imaging target surface with respect to the optical axis of the imaging means is calculated using the change rate obtained in the third step. A fourth step of quantitatively inspecting; and an inspecting method in an apparatus having an optical system and an imaging means. 6. A first step of capturing an image of a lattice pattern having a constant lattice pitch and a constant lattice direction, which is installed on an imaging target surface, by using an image capturing means, and within the image obtained in the first step. Not on the same line,
A second step of cutting out at least three lattice images having the same size and shape; a third step of counting the number of lattices included in the lattice image in a predetermined direction; and the first to third aspects. By performing the step of (1) by setting the image pickup target surface at a plurality of optical axis direction positions in the image pickup means, the rate of change of the number of lattices with respect to the position change of the image pickup target surface in the optical axis direction of the image pickup means. Of the lattice images of the fourth step of obtaining the image and all of the lattice images in the case where the installation position in the optical axis direction on the image pickup means of the image pickup target surface is constant among the number of lattice images of the lattice image obtained in the third step. A fifth step of quantitatively inspecting the perpendicularity of the image pickup target surface with respect to the optical axis of the image pickup means using the change rate obtained in the fourth step from the difference in the number of lattices obtained in the above; Have An inspection method in an apparatus having an optical system and an image pickup means characterized by the above. 7. An individual image of a lattice pattern having a constant lattice pitch and a constant lattice direction, which is installed on at least three positions which are not on the same straight line on the image pickup target surface, without changing the focus and magnification of the image pickup means. According to the first step of obtaining a plurality of lattice images including only the lattice pattern, Fourier transform is performed in the direction in which the number of lattices is counted in the plurality of lattice images, and a primary frequency is obtained from the obtained frequency spectrum. The second step of counting the number of grids included in the grid image by detecting the peak of the component; the first step and the second step; By arranging the image pickup device at an axial position and performing it, the rate of change of the number of lattices with respect to the position change of the image pickup means in the optical axis direction of the image pickup target surface is obtained. Of the number of grids obtained in the third step and the second step, the grids obtained from all the grid images when the installation position of the imaging target surface in the optical axis direction in the imaging means is constant. A fourth step of quantitatively inspecting the perpendicularity of the image pickup target surface with respect to the optical axis of the image pickup means by using the change rate obtained in the third step from the difference in the number. And an inspection method in an apparatus having an imaging unit. 8. An individual image is taken of a grating pattern having a constant grating pitch and a fixed grating direction, which is installed on at least three positions that are not on the same straight line on the image pickup target surface, without changing the focus and magnification of the image pickup means. According to the first step of obtaining a plurality of lattice images including only the lattice pattern, Fourier transform is performed in the direction in which the number of lattices is counted in the plurality of lattice images, and a primary frequency is obtained from the obtained frequency spectrum. A second step of extracting a component, and performing an inverse Fourier transform on the extracted primary frequency component,
A third step of calculating a phase value distribution in the lattice image based on the ratio of the real part and the imaginary part of the result, and a fourth step of counting the number of lattices included in the lattice image using the phase value distribution. And the first to fourth steps are performed by installing the image pickup target surface at a plurality of positions in the optical axis direction of the image pickup means, thereby performing the optical axis of the image pickup means of the image pickup target surface. A fifth step of obtaining a rate of change of the number of lattices with respect to a position change in a direction, and a number of lattices of a plurality of lattice images obtained in the fourth step, in the optical axis direction of the image pickup means of the image pickup target surface. From the difference in the number of lattices obtained from all the lattice images when the installation position is constant, the degree of perpendicularity of the image pickup target surface with respect to the optical axis of the image pickup means is calculated using the change rate obtained in the fifth step. Sixth step to quantitatively inspect The inspection method in an apparatus having an optical system and an imaging means and having a. 9. An inspection method in an apparatus having an optical system and an image pickup means for picking up and inspecting a magnetic recording track pattern on a magnetic tape recorded by a magnetic recording / reproducing apparatus and subjected to visualization processing. A first step of providing a grid pattern having a constant pitch and a constant grid direction in at least three positions substantially in the same plane as the imaging surface of the magnetic tape and not on the same straight line; Secondly, a plurality of lattice images including only the lattice pattern are obtained by individually capturing images without changing the focus and magnification of the image capturing unit.
And the third step of counting the number of grids included in the plurality of grid images in a predetermined direction, and the number of grids obtained in the third step, respectively, are compared to obtain the light of the image pickup means. A fourth step of inspecting the perpendicularity of the image pickup surface of the magnetic tape with respect to the axis, and an inspection method in an apparatus having an optical system and image pickup means. 10. Recorded by a magnetic recording and reproducing device,
A method for inspecting an apparatus having an optical system and an imaging means for imaging and inspecting a magnetic recording track pattern on a magnetic tape that has been subjected to visualization processing, wherein a grid pattern having a constant grid pitch and grid direction A first step of installing in at least three positions that are substantially in the same plane as the imaging surface of the tape and not on the same straight line; and a second step of imaging the lattice pattern using the imaging means , Not on the same straight line in the image obtained in the second step,
A third step of cutting out at least three lattice images having the same size and shape, a fourth step of counting the number of lattices included in the lattice image in a predetermined direction, and a fourth step A fifth step of inspecting the perpendicularity of the image pickup surface of the magnetic tape with respect to the optical axis of the image pickup means by comparing the respective numbers of the gratings, and an apparatus having the optical system and the image pickup means. Inspection method. 11. Recorded by a magnetic recording and reproducing device,
A method for inspecting an apparatus having an optical system and an imaging means for imaging and inspecting a magnetic recording track pattern on a magnetic tape that has been subjected to visualization processing, wherein a grid pattern having a constant grid pitch and grid direction A first step of installing in at least three positions that are substantially not on the same straight line as the image pickup surface of the tape, and the grid pattern is individually provided without changing the focus and magnification of the image pickup means. A plurality of lattice images including only the lattice pattern by capturing the second image.
And the number of grids included in the grid image by performing Fourier transform in the direction of counting the number of grids in the plurality of grid images and detecting the peak of the primary frequency component from the obtained frequency spectrum. And a fourth step of inspecting the perpendicularity of the image pickup surface of the magnetic tape with respect to the optical axis of the image pickup means by comparing the number of lattices obtained in the third step, respectively. An inspection method in an apparatus having an optical system and an image pickup means. 12. Recorded by a magnetic recording and reproducing device,
A method for inspecting an apparatus having an optical system and an imaging means for imaging and inspecting a magnetic recording track pattern on a magnetic tape that has been subjected to visualization processing, wherein a grid pattern having a constant grid pitch and grid direction A first step of installing in at least three positions that are substantially not on the same straight line as the image pickup surface of the tape, and the grid pattern is individually provided without changing the focus and magnification of the image pickup means. A plurality of lattice images including only the lattice pattern by capturing the second image.
And a third step of performing a Fourier transform in the direction in which the number of grids is counted in the plurality of grid images and extracting a primary frequency component from the obtained frequency spectrum, and the extracted primary frequency component Inverse Fourier transform to
A fourth step of calculating a phase value distribution in the grid image based on the ratio of the real part and the imaginary part of the result, and a fifth step of counting the number of grid lines included in the grid image using the phase value distribution. And a sixth step of inspecting the perpendicularity of the image pickup surface of the magnetic tape with respect to the optical axis of the image pickup means by comparing the number of lattices obtained in the fifth step, respectively. An inspection method in an apparatus having a characteristic optical system and imaging means. 13. An inspection method in an apparatus having an optical system and an image pickup means for picking up and inspecting a magnetic recording track pattern on a magnetic tape recorded by a magnetic recording / reproducing apparatus and subjected to visualization processing, the grating pitch and A first step of installing a lattice pattern having a constant lattice direction in at least three positions substantially in the same plane as the imaging surface of the magnetic tape and not on the same straight line; A plurality of lattice images including only the lattice pattern is obtained by individually capturing the images without changing the focus and magnification of the means;
And a third step of counting the number of grids included in the plurality of grid images in a predetermined direction, the second step and the third step, and the grid pattern of a plurality of grids of the imaging means. It is determined in the fourth step and the third step of determining the rate of change of the number of gratings with respect to the positional change of the image pickup means in the optical axis direction of the grating pattern by setting the grating pattern at a position in the optical axis direction. Among the number of lattices, the change rate obtained in the fourth step is calculated from the difference in the number of lattices obtained from all the lattice images when the position of the lattice pattern in the optical axis direction of the image pickup means is constant. A fifth step of quantitatively inspecting the perpendicularity of the image pickup surface of the magnetic tape with respect to the optical axis of the image pickup means, and an inspection method in an apparatus having the optical system and the image pickup means. 14. An inspection method in an apparatus having an optical system and an image pickup means for picking up and inspecting a magnetic recording track pattern on a magnetic tape recorded by a magnetic recording / reproducing apparatus and subjected to visualization processing, the method comprising: A first step of installing a lattice pattern having a constant lattice direction in at least three positions substantially in the same plane as the imaging surface of the magnetic tape and not on the same straight line; A second step of imaging using the means, and not on the same straight line in the image obtained in the second step,
A third step of cutting out at least three lattice images having the same size and shape; a fourth step of counting the number of lattices included in the lattice image in a predetermined direction; and the second to fourth steps. By performing the step of (1) by setting the lattice pattern at a plurality of positions in the optical axis direction of the image pickup means, the rate of change of the number of the lattices with respect to the position change of the lattice pattern in the optical axis direction of the image pickup means is obtained. Of the number of lattices obtained in the fifth step and the fourth step, the difference in the number of lattices obtained from all the lattice images when the position of the lattice pattern in the optical axis direction of the image pickup means is constant. From the above, a sixth step of quantitatively inspecting the perpendicularity of the image pickup surface of the magnetic tape with respect to the optical axis of the image pickup means using the change rate obtained in the fifth step is included. Inspection method in an apparatus having an optical system and an image pickup means. 15. An inspection method in an apparatus having an optical system and an imaging means for imaging and inspecting a magnetic recording track pattern on a magnetic tape recorded and visualized by a magnetic recording / reproducing apparatus, the method comprising: A first step of installing a lattice pattern having a constant lattice direction in at least three positions substantially in the same plane as the imaging surface of the magnetic tape and not on the same straight line; A plurality of lattice images including only the lattice pattern is obtained by individually capturing the images without changing the focus and magnification of the means;
And the number of grids included in the grid image by performing Fourier transform in the direction of counting the number of grids in the plurality of grid images and detecting the peak of the primary frequency component from the obtained frequency spectrum. By performing a third step of counting, and the second step and the third step by installing the lattice pattern at a plurality of positions in the optical axis direction of the image capturing means, thereby performing the image capturing of the lattice pattern. A fourth step of obtaining a change rate of the number of gratings with respect to a position change of the means in the optical axis direction; Based on the difference in the number of grids obtained from all the grid images when it is constant, the change rate obtained in the fourth step is used to take an image of the magnetic tape with respect to the optical axis of the image pickup means. Inspection method in an apparatus having an optical system and an imaging means and having a fifth step of quantitatively inspected perpendicularity of the plane. 16. An inspection method in an apparatus having an optical system and an imaging means for imaging and inspecting a magnetic recording track pattern on a magnetic tape recorded and visualized by a magnetic recording / reproducing apparatus, the method comprising: A first step of installing a lattice pattern having a constant lattice direction in at least three positions substantially in the same plane as the imaging surface of the magnetic tape and not on the same straight line; A plurality of lattice images including only the lattice pattern is obtained by individually capturing the images without changing the focus and magnification of the means;
And a third step of performing a Fourier transform in the direction in which the number of grids is counted in the plurality of grid images and extracting a primary frequency component from the obtained frequency spectrum, and the extracted primary frequency component Inverse Fourier transform to
A fourth step of calculating a phase value distribution in said grid image than the ratio between the real part and the imaginary part of the result, by using the phase value distribution, fifth counting the grid number included in the lattice image And the second to fifth steps are performed by installing the lattice pattern at a plurality of positions in the optical axis direction of the image pickup means, thereby performing the lattice pattern in the optical axis direction of the image pickup means. First to obtain the rate of change of the number of grids with respect to position change
From the difference in the number of lattices obtained from all the lattice images when the position of the lattice pattern in the optical axis direction of the image pickup means is constant among the number of lattices obtained in the step 6 and the fifth step. And a seventh step of quantitatively inspecting the perpendicularity of the image pickup surface of the magnetic tape with respect to the optical axis of the image pickup means using the change rate obtained in the sixth step. An inspection method in an apparatus having an optical system and an imaging means.