JPH0626832A - Method and apparatus for measuring surface shape - Google Patents

Abstract

PURPOSE:To make it possible to measure the shape of a surface under the contact condition close to the actual using state by correcting the length of a light path so that optical interference is generated with the reflected light from the surface of a material to be measured and the reflected light from a reference surface, and masuring the surface shape. CONSTITUTION:A material to be measured 1 is supported on a reare contact 2. A light transmitting contact body 4 is brought into contact with the front surface of the material. Liquid-state filler 5 is filled between the contact body 4 and the surface of irregularities. A reference surface and a lens 19 are moved in the direction of an optical axis with a light-path-length correcting mechanism 24. Adjustment is performed so that the light-path length from a lens 18 to the surface of the material to be measured 1 becomes equal to the light-path length from an objective lens 19 on the reference surface side to a reference surface 20. The reflected light, which is reflected from a beam splitter 17 of an interferometer and advances upward, is overlapped and made to interfere with the reflected light, which is reflected from the surface of the material to be measured 1, transmitted through the splitter 17 and advances upward. The interference fringes corresponding to the irregularities of the surface of the material to be measured are generated. The result of the analysis of the interference fringes with an interference-fringe analyzer 32 is transmitted to a measurement controller 33. A piezoelectric element 22 is driven so as to generate the interference fringes accurately, and the light-path-correting mechanism 24 is operated. Therefore, the surface shape of the material to be measured 1 can be measured under the contact condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for measuring the surface shape of soft materials such as magnetic tapes, floppy disks, plastic films, polishing sheets and the like, and composite materials thereof, and more specifically, The present invention relates to a method and an apparatus for measuring the surface shape of these materials used in sliding contact with a magnetic head or the like under contact conditions close to a practical state while contacting an abutting body.

[0002]

2. Description of the Related Art In a high density magnetic recording medium such as a magnetic tape or a floppy disk, the recording / reproducing output is improved and the S / N ratio is increased.
For this reason, it is desirable to make the surface of the magnetic layer as smooth as possible. However, if the surface of the magnetic layer is too smooth, sliding noise may be increased, or the friction and wear characteristics of the magnetic head and the guide member may be deteriorated.

For this reason, attempts have been made to precisely measure and analyze the shape of the surface of the magnetic layer and control it so that it has a smooth and fine uneven shape. As a method, for example, Tactile Step and Talysurf manufactured by Rank-Tera-Hobson, Tokyo Seimitsu Co., Ltd., a stylus type surface profile measuring instrument such as Surfcom, WYKO
Manufactured by the company; optical interference type surface profile measuring instrument such as TOPO-3D,
Optical focus error detection type surface profile measuring instrument such as ET-30HK, scanning tunnel microscope such as Nanoscope II, electron microscope such as ERA-3000, manufactured by Kosaka Laboratory; Is being used.

[0004]

However, all of these conventional surface profile measuring machines are designed to perform measurement after fixing the magnetic layer surface in a non-contact state in the atmosphere or vacuum, Since the surface shape when the magnetic layer surface comes into contact with the magnetic head, etc. cannot be measured and the magnetic layer surface during practical use is in contact with the magnetic head etc., it is measured by these conventional surface shape measuring machines. Elastic deformation due to the contact force, as compared with the case of In a soft material such as a magnetic tape or a floppy disk, or a composite material thereof, deformation of the convex portion is particularly large among the surface irregularities due to the contact force. Therefore, according to the conventional surface shape measurement result, various characteristics of the magnetic recording medium are obtained. There was a problem that could not be fully clarified.

[0005]

The present invention has been made as a result of various studies for improving such a drawback, and a light beam is applied to the surface of an object to be measured, and the reflected light is used to make a Linic interferometer. In the measurement method for measuring the surface shape of the measured object with, the change of the optical path length from the focusing point of the measured object side objective lens of the lnic interferometer to the measured object side objective lens The reference surface and the reference surface side objective lens are simultaneously moved in the optical axis direction, and the optical path length is corrected so that the reflected light from the surface of the DUT and the reflected light from the reference surface cause optical interference, and the DUT is measured. The surface shape of the object to be measured can be measured under the contact condition close to the practical state by measuring the surface shape of.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the surface shape measuring apparatus according to the present invention will be described below with reference to FIG. In FIG.
An object to be measured 1 is supported on a backing 2, and a light-transmitting contact body 4 supported by a sample holder 3 so as not to be raised is in contact with the surface thereof. The liquid filler 5 is filled between the light-transmitting contact member 4 and the surface of the DUT 1 having irregularities.

The backing 2 is supported by an elastic body 9 on a load cell 8 installed on a swing support plate 7 of a fine movement table 6,
The fine movement table 6 is arranged on the sample stage 10. 11
Is an adjustment photograph attached to the fine movement table 6, and the rotation of the adjustment photograph 11 causes the rocking support plate 7 pivotally supported by the pin 12 to swing, and the load cell 8 and the elastic body. 9. Any contact force is applied to the surface of the DUT 1 that is in contact with the light transmissive contact member 4 via the backing 2. Then, this contact force is detected by the load cell 8.

Reference numeral 13 denotes a light emitting body 13a, a lens 13b, a lens 13c, an aperture stop 13d, and a lens 13.
e, a field stop 13f and a lens 13g, the light from the light source 13 is transmitted through the spectral filter 14 and then the light source beam splitter 1
It is reflected by 5 and goes downward.

A part of the downward reflected light is transmitted through the interferometer beam splitter 17 of the linic interferometer 16 to reach the object-to-be-measured side objective lens 18, and by this object-to-be-measured side objective lens 18. The light-transmitting contact member 4 and the liquid filler 5 are focused on the uneven surface of the DUT 1. Then, the light reflected by the surface of the DUT 1 returns to the DUT objective lens 18 through the liquid filler 5 and the light-transmitting contact body 4 again, and further passes through the interferometer beam splitter 17. It penetrates and goes upward.

Further, a part of the light incident on the lnic interferometer 16 is reflected by the interferometer beam splitter 17 and reaches the reference surface side objective lens 19, and the reference surface side objective lens 19 directs the reference surface 20. Focused. Then, the reflected light from the reference surface 20 returns to the reference surface side objective lens 19, is further reflected by the interferometer beam splitter 17, and travels upward.

Here, the reference surface side objective lens 19 is an optical path length correction mechanism 24 constructed by inserting a bottomed inner cylindrical body 23 with a piezo element 22 interposed in a horizontally arranged bottomed outer cylindrical body 21. It is fitted and fixed in the bottomed inner cylindrical body 23, and is finely moved and adjusted by the piezo element 22 in the optical axis direction. In addition, the optical path length correction mechanism 2
4 is movably supported in the optical axis direction by a moving carriage 26 on the stage 25, and is precisely moved and adjusted in the optical axis direction.

The reference surface 20 is fixed to a reference surface focus adjusting mechanism 27 attached to the bottom wall of the bottomed inner cylindrical body 23,
When the reference surface side objective lens 19 moves in the optical axis direction due to the movement of the bottomed outer cylindrical body 21, the reference surface side objective lens 19 moves at the same time.
The focus of the reference surface is adjusted by the adjusting knob 29 of the reference surface focus adjusting mechanism 27 protruding from the through hole 28 in the bottom wall.

Thus, when the light incident on the linic interferometer 16 passes through the light-transmissive abutting body 4 via the object-side objective lens 18, the contact surface between the light-transmissive abutting body 4 and the air. The focal length becomes deeper due to the refraction of light at 1, and the optical path length from the object-side objective lens 18 to the surface of the object to be measured 1 is equal to the refractive index of the light-transmitting contact member 4 being larger than that of air. When the length is increased, the reference surface 20 and the reference surface side objective lens 19 are simultaneously moved in the optical axis direction by the optical path length correction mechanism 24 in accordance with the change of the optical path length, and the object side objective lens 18 is measured.
To the surface of the DUT 1 and the optical path length from the reference surface side objective lens 19 to the reference surface 20 are adjusted to be equal.

As a result, the reflected light which is reflected by the interferometer beam splitter 17 and goes upward, and the reflected light which is reflected by the surface of the DUT 1 and passes through the interferometer beam splitter 17 and goes upward. The reflected lights are overlapped and interfere with each other to generate interference fringes corresponding to the unevenness of the surface of the DUT 1. Then, this interference fringe reaches the camera 31 via the camera-side objective lens 30, and is converted into an electric image signal by the camera 31.

Next, the electric image signal converted by the camera 31 is transmitted to and analyzed by the interference fringe analyzer 32.
Based on this analysis, for example, Katerine
Cream: COMPARISON OF PHAS
E-MEASUREMENTAL GORITHMS, S
The surface shape of the DUT 1 is obtained by the stripe scanning method described in PIE Vol (1986), and the surface of the DUT 1 is contacted with the light-transmissive abutting body 4, and The surface shape is measured.

The analysis result of the interference fringes by the interference fringe analyzer 32 is transmitted to the measurement controller 33 connected to the interference fringe analyzer 32, and the measurement controller 33 causes the interference fringes to always be generated accurately. The piezoelectric element 22 is voltage-driven by the command, and the optical path length correction mechanism 24 is operated.

Therefore, according to this method and apparatus, when the DUT 1 is used in a contact state such as a magnetic recording medium used in sliding contact with a magnetic head or the like, contact conditions close to a practical state are used. The surface shape of the DUT 1 can be measured.

Further, according to this method and apparatus, in addition to the surface shape of the DUT 1 in contact with the light-transmissive contact body 4, the shape of an appropriate light-reflecting surface inside the light-transmissive contact body. Can be measured nondestructively, for example, the adhesive surface between the magnetic layer of the magnetic tape and the base film can be measured by passing through the base film, and the inner surface of the hollow glass can be measured. It can also be applied to measurement, optical disc media, display devices, and the like.

On the other hand, if the optical interferometer 16 is not provided with the optical path length correction mechanism 24, the light incident on the linear interferometer 16 is transmitted through the sample-side objective lens 18 to the light-transmitting contact member 4. When the light is transmitted, the focal length becomes deep due to the refraction of light at the contact surface between the light-transmitting contact member 4 and air
Even if the optical path length from the sample-side objective lens 18 to the surface of the DUT 1 is lengthened by the refractive index of the light-transmitting contact member 4 being larger than that of air, the reference surface-side objective lens 19 to the reference surface Since the optical path length up to 20 does not change, an optical path difference occurs,
The coherence of light is lost and the surface shape of the DUT 1 cannot be measured.

Here, as the light-transmitting contact member 4, various shapes and materials that give the surface of the object to be measured 1 a contact condition close to a practical state can be used. It is necessary to select the one that transmits the measurement light beam for surface shape measurement to the minimum. Further, the light-transmitting contact member 4 is used by being brought into contact with the surface of the DUT 1 as well as non-contact,
In order to enable comparative measurement with a stress-free state, it is preferable to be able to leave it at an appropriate distance. In this case,
It is preferable that the distance from the surface of the DUT 1 is 0.1 mm or less because the measurement will be inconvenient if bubbles are generated in the liquid filler 5.

The liquid filler 5 is used as the light-transmitting contact member 4.
The surface facing the surface of the DUT 1 reflects the measuring light beam, and is provided to prevent noise, error, error, etc. from occurring at the time of measuring the surface shape. Therefore, it is preferable that the refractive index of the light-transmitting contact member 4 is as close as possible, and the difference in refractive index between the light-transmitting contact member 4 and the light-transmitting contact member 4 is preferably 0.3 or less. Specific examples include, for example, water and liquids used for observation by a liquid immersion microscope, and are not particularly limited as long as they have chemical properties that do not change the surface shape of the DUT 1. Can be used.

Further, in order to correct the optical path difference, the stage 2 which allows the bottomed outer cylindrical body 21 of the optical path length correction mechanism 24 to move.
It is desirable to move the movable carriage 26 on the carriage 5 as accurately as possible. Even if the material and the shape of the light-transmissive abutting body 4 are arbitrarily set, the optical path difference caused thereby can be corrected. It is desirable to have a sufficient amount of movement so that For example, in order to secure the thickness of the light-transmitting contact member 4 that can sufficiently withstand the contact force, at least 1
It is desirable to have a movement amount of mm or more.

A test example in which the surface shape of the magnetic layer surface of the video tape is measured by using the surface shape measuring apparatus shown in FIG. 1 will be described below. Test Example 1 Ferromagnetic iron metal powder (coercive force 1600 oersted, saturation magnetic 100 parts by weight 120 emu / g, major axis diameter 0.18 μm, axial ratio 10) Hydroxyl group-containing vinyl chloride resin 10〃 Thermoplastic polyurethane resin 7〃 Alumina (Particle size 0.2 μm) 8 〃 myristic acid 2 〃 red iron oxide (particle size 0.8 μm) 2 〃 cast 5H (Tokai Carbon Co., Ltd .; carbon black, particles 2 〃 diameter 20 mμ) cyclohexanone 70 〃 toluene 70 〃

This composition was mixed and dispersed in a ball mill for 96 hours, and then 5 parts by weight of a trifunctional polyisocyanate compound was added, followed by stirring for 5 minutes to prepare a magnetic paint. This magnetic coating was applied onto a biaxially oriented polyethylene terephthalate film with a thickness of 10 μm and the thickness after drying was 2.5 μm.
m after coating, drying and calendering
A video tape was made by cutting it into a predetermined width. In order to make it easier to confirm the effect of the surface profile measuring device, the calendering process was adjusted weakly, and the surface of the magnetic layer was rougher than that of a commercially available metal video tape.

Then, in the surface shape measuring apparatus shown in FIG. 1, each member corresponding to the following: Backing 2: Polyethylene terephthalate film (length 1 mm × width 1 mm × thickness 0.075 mm) Light transmitting contact member 4 : Cover glass for microscope (refractive index 1.52) Liquid filler 5: Water (refractive index 1.33) Micro table 6: Chuo Seiki Co., Ltd .; TS-201 load cell 8: TMI Co .; T7 elastic body 9: Silicon Rubber plate (length 1 mm x width 1 mm x thickness 2 mm) Sample stage 10: manufactured by Chuo Seiki Co., Ltd .; X-axis stage LS-641- (C ₂ ) CL is combined at right angles and further inclined stage T Combined with D-601 Object side objective lens: Nikon; microscope objective lens (40x, long-distance type 18) Reference plane side objective lens: Nikon; microscope objective (40x) Long-distance type) turtle La 31: 256 × 256 μm element was used to measure the surface shape of the video tape when the load read from the output voltage of the load cell 8 was 0 g and 25 g, and the surface roughness Ra (center line) was measured. Average roughness)
And PV (Peak to Valley) were calculated. In this test example, since the surface shape of the DUT 1 was optically measured in water, the refractive index of water is twice as large as that in the atmosphere. Therefore, the surface roughness was calculated by multiplying the measured value by 1 / 1.33.

Test Example 2 The video tape used in Test Example 1 was adhered to an optical flat surface by wetting the back surface with water so that wrinkles did not occur, and the reference surface objective lens 19 and the reference surface 20 were indicated by dotted lines in FIG. The surface shape was measured in the atmosphere at the indicated position to determine the surface roughness Ra and PV. Table 1 below shows the results.

[0027]

As is clear from Table 1 above, in the surface profile measuring method (Test Example 1) according to the present invention, when the load indicating the contact force is 0 g, the result obtained in Test Example 2 of the normal surface profile measuring method is as follows. Almost the same results were obtained. Further, when the load indicating the contact force is set to 25 g, the PV is reduced particularly as compared with the load of 0 g, which shows that the convex portion on the surface of the video tape is elastically deformed and collapsed by the contact force. .

[0029]

As described above, according to the surface shape measuring method and the surface shape measuring apparatus of the present invention, the surface shape of the material to be used in sliding contact with the magnetic head or the like is set to a contact condition close to a practical state. It can be measured below.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an embodiment of a surface shape measuring apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Object to be measured 13 Light source 14 Spectral filter 15 Light source beam splitter 16 Linic interferometer 17 Interferometer beam splitter 18 Object to be measured side objective lens 19 Reference surface side objective lens 20 Reference surface 21 Bottomed outer cylinder 22 Piezo Element 23 Bottomed inner cylindrical body 24 Optical path length correction mechanism 25 Stage 26 Truck 27 Reference plane focus adjustment mechanism 28 Through hole 29 Adjustment knob

Claims (2)

[Claims] 1. A measuring method for measuring a surface shape of an object to be measured by a linic interferometer using reflected light of a light beam irradiating the surface of the object to be measured, wherein the object lens of the object to be measured of the linic interferometer is combined. In response to changes in the optical path length from the focus position to the DUT-side objective lens, the reference surface of the Linic interferometer and the reference-plane-side objective lens are simultaneously moved in the optical axis direction to reflect the light reflected from the DUT surface. Shape measuring method characterized by measuring the surface shape of an object to be measured by correcting the optical path length so that the reflected light from the reference surface and the reference surface cause optical interference. 2. A surface shape measuring apparatus having a linic interferometer for measuring the surface shape of an object to be measured using reflected light of a light beam applied to the surface of the object to be measured. It is equipped with moving means that moves the surface-side objective lens in the optical axis direction at the same time, and responds to changes in the optical path length from the focusing point of the object-side objective lens of the Linic interferometer to the object-side objective lens. Then, the reference surface of the Linic interferometer and the reference surface side objective lens are simultaneously moved in the optical axis direction, and the optical path length is corrected so that the reflected light from the DUT surface and the reflected light from the reference surface cause optical interference. To measure the surface shape of the object to be measured