JP2023060155A - Film thickness distribution measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an accurate film thickness distribution with high efficiency on the basis of intensity of interference light.

SOLUTION: A film thickness distribution measurement device 1 for measuring a film thickness distribution of a lubricant that lubricates a contact portion of objects in an EHL state comprises: a substrate 2 that has light permeability; a contact piece 3 that contacts the substrate 2 through a lubricant LB; a light source section 7 that emits light including at least three kinds of wavelengths toward a contact portion SP between the substrate 2 and the contact piece 3; an interference light imaging section 8 that takes an image of light reflected from the contact portion SP between the substrate 2 and the contact piece 3, through the substrate 2, and obtains a colored fringe as an interference color image; and a computer section 9. The computer section 9 comprises: an image recording part 11 that records the interference color image taken by the interference color imaging section 8; and a film thickness distribution estimation part 12 that performs color separation for each light having at least three kinds of wavelengths from color information at each point included in the selected interference color image among the interference color images recorded in the image recording part 11, obtains intensity for each of the wavelengths and calculates the film thickness distribution of the lubricant LB at the contact portion SP between the substrate 2 and the contact piece 3 on the basis of the intensity.

SELECTED DRAWING: Figure 3

COPYRIGHT: (C)2023,JPO&INPIT

Description

Applied for application of Article 30, Paragraph 2 of the Patent Act Published in Tripology Conference 2018 Autumn Proceedings of Ise on October 29, 2018 [Publications] Tripology Conference 2018 Autumn from November 7 to 9, 2018 Released at Ise

The present invention relates to a film thickness distribution measuring apparatus for measuring the film thickness distribution of a lubricant at a contact portion of a rotating rotating body or a sliding object with respect to a substrate that rotates or reciprocates through the lubricant.

For example, in a bearing, a ball (one object) lubricated with lubricating oil and an outer ring or an inner ring (the other object) are in line contact or point contact. At this time, since the load is concentrated on the contact portion of the objects, the objects elastically deform and the lubricating oil enters an elasto-hydrodynamic lubrication state (EHL state) in which the lubricating oil has high pressure and high viscosity.

As a conventional film thickness distribution measuring apparatus for observing the EHL state of such a bearing, an image recording unit for recording an interference color image captured by an interference color imaging unit, and an interference color image recorded in the image recording unit , from the color information of each point included in the selected interference color image, color separation is performed for each light of at least three wavelengths to calculate the luminance value, the phase for each wavelength, and a plurality of film thickness candidates, and the calculated There is one that includes a film thickness distribution estimating unit that estimates the film thickness distribution of the lubricant at the contact portion between the substrate and the contact pieces from a plurality of film thickness candidates (see Patent Document 1).

JP 2017-44587 A

The conventional technique is a method of measuring the film thickness distribution solely from the relationship between the film thickness of the lubricant and basic elements of color such as hue and brightness. Such a method can acquire the film thickness distribution in a certain area by one observation, and it is a method that can obtain results quickly, but the accuracy of the obtained film thickness is not necessarily high. I can not say.

TECHNICAL FIELD The present invention relates to a technique capable of obtaining a film thickness distribution with high efficiency and good accuracy.

A film thickness distribution measuring apparatus according to the present invention is a film thickness distribution measuring apparatus for measuring the film thickness distribution of a lubricant that lubricates contact portions between objects in an EHL state, comprising: a substrate having light transmittance; a contact piece that comes into contact with the above through the lubricant, a light source unit that irradiates light containing at least three wavelengths toward the contact portion between the substrate and the contact piece, and the contact piece between the substrate and the contact piece. An interference color imaging unit for capturing an image of the light reflected from the contact portion through the substrate and acquiring color interference fringes as an interference color image, and a computer unit, wherein the computer unit includes the interference color imaging. an image recording unit for recording the interference color image captured by the image recording unit; a film thickness distribution estimating unit that separates colors for each wavelength of light, acquires the intensity for each wavelength, and calculates the film thickness distribution of the lubricant at the contact portion between the substrate and the contact piece based on the intensity. Prepare.

According to the present invention, highly efficient and accurate film thickness distribution can be obtained based on the intensity of interference light.

Schematic diagram showing the overall configuration of a film thickness distribution measuring apparatus according to an embodiment of the present invention. FIG. 4 is a partial enlarged view showing an enlarged part of the film thickness distribution measuring apparatus of the embodiment, (a) an enlarged view of the substrate and the contact pieces, (b) an example of the measurement target region R in (a). Enlarged view of . (a) is a schematic diagram showing the overall configuration of a film thickness distribution measuring apparatus according to another embodiment of the present invention, and (b) is an enlarged view of an example of a measurement target region R in (a). 4 is a graph showing changes in various physical properties of Sample 1 over time. 4 is a graph showing the film thickness distribution in the radial direction X for Sample 1. FIG. Observed images obtained by various methods, including (a) image of sample 2 by spectroscopic method, (b) image of sample 3 by spectroscopic method, (c) interference image of sample 2 by SLIM method, and (d) SLIM method. Interference image of sample 3, (e) Interference image of sample 2 using the film thickness distribution measuring device of FIG. interference image. 2 is a graph showing the reflectance in the radial direction X when irradiated with blue wavelength (470 nm) light for (a) sample 2 and (b) sample 3. FIG. 2 is a graph showing the reflectance in the radial direction X when irradiated with light having a green wavelength (560 nm), (a) sample 2 and (b) sample 3. FIG. 2 is a graph showing the reflectance in the radial direction X when irradiated with red wavelength (645 nm) light for (a) sample 2 and (b) sample 3. FIG. 2 is a graph showing the reflectance with respect to the wavelength of irradiation light, (a) sample 2, (b) sample 3. FIG. 4 is a graph showing the film thickness distribution in the radial direction X for (a) sample 2 and (b) sample 3;

EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated, using a figure. In each figure, the horizontal directions are expressed as the x direction and the y direction, and the direction perpendicular to the xy plane (that is, the gravitational direction) is expressed as the z direction. Also, the direction against gravity is expressed as up, and the direction in which gravity works is expressed as down.

FIG. 1 is a schematic diagram showing the overall configuration of one embodiment embodying the present invention. FIG. 2 is a partial enlarged view showing an enlarged part of an example of an embodiment embodying the present invention.

A film thickness distribution measuring apparatus 1 according to the present invention measures the film thickness distribution of a lubricant LB that lubricates a contact portion SP between a substrate 2 and a contact piece 3 in an EHL state. Specifically, the film thickness distribution measuring apparatus 1 captures an interference color image, and measures the film thickness distribution of the lubricant LB based on this interference color image. More specifically, the film thickness distribution measuring apparatus 1 includes a substrate 2, a contact piece 3, a moving mechanism 4, a rotating body rotating mechanism 5, a load applying mechanism 6, a light source section 7, an interference color imaging section 8, and a computer section 9. , a display unit 10, and the like.

The substrate 2 is made of a material having optical transparency. Specifically, the substrate 2 can be exemplified by a transparent glass disk 20 that is flat in the xy direction and has a predetermined thickness in the z direction. More specifically, a metal thin film (semi-reflective film) 21 such as chromium (Cr) is formed on the lower surface of the disc 20, and a lubricant such as silicon oxide (SiO ₂ ) is applied to the lower surface. A transparent film 22 having a refractive index similar to that of the agent LB is formed.

The contact piece 3 rotates while being in contact with the substrate 2 via the lubricant LB. Specifically, as the contact piece 3, a steel ball 30, which is one type of rotating body, is exemplified. A shaft 31 is connected to the steel ball 30 . The shaft 31 has a predetermined length in a direction parallel to the xy plane (x direction in FIG. 1), and is connected to the rotating body rotating mechanism 5, which will be described later.

Steel ball 30 is in contact with transparent film 22 on the lower surface of disc 20 via lubricant LB. An oil pan P is provided below the steel balls 30 to store the lubricant LB. When the steel ball 30 rotates, the lubricant LB accumulated in the oil pan P moves upward due to its own viscosity, and excess lubricant falls downward. Therefore, an appropriate amount of lubricant LB is supplied to the contact portion SP between the disc 20 and the steel ball 30 . Steel ball 30 has a radius of gyration RB.

The moving mechanism 4 relatively moves the substrate 2 and the contact pieces 3 . Specifically, the moving mechanism 4 can be configured by a rotary motor 40 . The rotary motor 40 rotates the disk 20 about an axis perpendicular to the xy direction at a predetermined speed in the direction indicated by the arrow 2d, stops it, or rotates the disk 20 at a predetermined speed in the direction opposite to the arrow 2d. It rotates. More specifically, the rotary motor 40 includes a main body and a rotor (not shown) incorporated inside the main body. The rotary motor 40 is connected to the computer section 9, which will be described later in detail, via a motor amplifier unit (not shown), and the rotation direction and rotation speed of the disk 20 are appropriately controlled.

The rotating body rotating mechanism 5 rotates a steel ball 30 which is a rotating body. Specifically, the rotating body rotating mechanism 5 rotates the steel ball 30 and the shaft 31 at a predetermined speed in the direction of the arrow 3d, stops them, or rotates them at a predetermined speed in the direction opposite to the arrow 3d. It is something that makes More specifically, the rotating body rotating mechanism 5 includes a rotating motor 50 and a shaft 51 connected to the rotor of the rotating motor 50 .

The rotary motor 50 is connected to the computer section 9, which will be described later in detail, via a motor amplifier unit (not shown), and the rotation direction and rotation speed of the shaft 51 are appropriately controlled.

The load application mechanism 6 applies a load when the steel ball 30 is brought into contact with the disc 20 . Specifically, the load applying mechanism 6 pushes up the steel ball 30 arranged below the disc 20 . More specifically, the load applying mechanism 6 is configured with an actuator 60 and a holder 63 . The actuator 60 has a mover 61 that moves up and down by air, hydraulic pressure, or electric power.

The rotational speed of the disk 20, the rotational speed of the steel ball 30, the pressing load of the actuator 60 of the load applying mechanism 6, and the like are set or assumed so as to reproduce the state in which the bearing is actually used. Set according to usage conditions. By doing so, the environmental conditions of the contact area in the bearing rotating in the EHL state can be set.

The light source unit 7 irradiates the contact portion SP between the substrate 2 and the contact piece 3 with light L1 including at least three wavelengths. Specifically, the light source section 7 includes an illumination unit 70 and an illumination power source 75 .

The lighting unit 70 emits light containing at least three wavelengths necessary for capturing an interference color image. Specifically, the lighting unit 70 includes a white lamp 72 , a reflector 71 , and a three-wavelength bandpass filter 73 . The white lamp 72 emits light in a wide band including blue: 470 nm, green: 560 nm, and red: 600 nm (so-called broad wavelength band), and a specific example is a halogen lamp. The reflector 71 reflects the visible light emitted from the white lamp 72 and increases the amount of the light L1 emitted to the outside. The three-wavelength band filter 73 passes at least three wavelength components (here, red, green, and blue are exemplified) in the light emitted from the white lamp 72, and attenuates other wavelength components. is. More specifically, the three-wavelength bandpass filter 73 is a so-called three-wavelength bandpass filter in which a plurality of thin films are formed on the surface of a glass or quartz substrate. Note that the three-wavelength band filter 73 only has to play the role of extracting at least three wavelength components from the light emitted from the white lamp 72 , and does not necessarily have to be arranged in the light source section 7 . That is, the three-wavelength band filter 73 may be arranged at any position on the optical path from the light source unit 7 to the interference color imaging unit 8, and the arrangement position is not particularly limited.

Also, if it is possible to apply light of at least three wavelength components, the three-wavelength bandpass filter 73 is not necessarily required. For example, if three different wavelength laser sources are applied in place of the light source unit 7, particularly its white lamp 72, no filtering is required, ie, the three-wavelength bandpass filter 73 is not required. That is, the above-mentioned "the light source unit 7 (or the lighting unit 70) emits light containing at least three wavelengths" means only when the light from a single light source such as the white lamp 72 contains three wavelengths. However, it also means that there are three wavelengths of light emitted from three light sources such as three laser sources.

The lighting power supply 75 supplies power necessary for light emission to the white lamp 72 of the lighting unit 70 .

The interference color imaging section 8 captures the light L3 reflected from the contact portion SP between the substrate 2 and the contact piece 3 as an interference color image through the substrate 2 with the imaging camera 80 . Specifically, the interference color imaging unit 8 includes an imaging camera 80 and a lens unit 81 . Here, the light L3 reflected from the contact portion SP between the substrate 2 and the contact piece 3 includes the light reflected at the interface between the disk 20 and the metal thin film 21 (so-called surface reflected light) and the lubricant The light reflected at the interface between the LB and the steel ball 30 (so-called rear surface reflected light) is synthesized.

The imaging camera 80 outputs a video signal (analog signal) and video data (digital signal) corresponding to a captured color image to the outside, and includes a color filter 85 and an imaging device 86 .

The lens unit 81 forms an image of the contact portion SP between the substrate 2 and the contact piece 3 on the imaging element 86 of the imaging camera 80 . In addition, the lens unit 81 in this embodiment also has the role of irradiating the imaging target with the light emitted from the light source unit 7, and makes the illumination light the same as the imaging optical axis (that is, coaxial oblique method). be able to. Specifically, the lens unit 81 includes a half mirror 82 , an objective lens 83 and an imaging lens 84 . Therefore, the lens unit 81 reflects the light L1 emitted from the light source unit 7 by the half mirror 82 and irradiates the film thickness measurement target region R as the illumination light L2, so that the contact portion between the substrate 2 and the contact piece 3 Of the light L3 reflected from the SP, the light L4 that has passed through the objective lens 83 and the half mirror 82 can be imaged on the imaging device 86 of the imaging camera 80 by the imaging lens 84 .

The computer unit 9 performs input and output of signals and data, storage of data, arithmetic processing on input or stored data, input and storage of images, image processing on these images, determination processing and image conversion based on image processing. It performs processing, determination results, output of images after image processing, and the like. Specifically, the computer section 9 includes an input section, an information recording section, a numerical calculation processing section, an image processing section, and an output section. More specifically, the computer unit 9 is composed of a computer (hardware) having an image processing function and its execution program (software). The computer unit 9 also includes information input devices such as a keyboard, mouse, and trackpad, and is connected to the display unit 10, which will be described later.

The computer section 9 includes an image recording section 11 and a film thickness distribution estimation section 12 . The image recording section 11 records the interference color image captured by the interference color imaging section 8 . Specifically, the image recording section 11 is composed of an information recording section (for example, a magnetic recording medium such as a hard disk, a semiconductor memory, etc.) of the computer section 9 .

The film thickness distribution estimating unit 12 performs color separation for each light of at least three wavelengths from the color information of each point included in the selected interference color image among the interference color images recorded in the image recording unit 11. , obtain the intensity for each wavelength, and further, for example, the reflectance corresponding to the intensity, and estimate the film thickness distribution of the lubricant LB at the contact portion SP between the substrate 2 and the contact piece 3 from the reflectance. . Specifically, the film thickness distribution estimating section 12 is composed of an image processing section and a numerical calculation processing section (hardware) of the computer section 9 and their execution programs (software).

Therefore, when the video signal (analog signal) or the video data (digital signal) output from the interference color imaging unit 8 is input, the computer unit 9 performs predetermined image processing or image processing based on the execution program. The film thickness distribution can be estimated by storing the image in the recording unit 11, reading the image from the image recording unit 11, and performing predetermined image processing and numerical calculation processing in the film thickness distribution estimation unit 12. can.

Furthermore, in this embodiment, a configuration including the pressing load measuring section 65 and the torque measuring section 14 is illustrated.

The pressing load measuring section 65 measures the load when the steel ball 30 is pressed against the disc 20 . Specifically, the pressing load measuring section 65 includes a load cell and an amplifier section (not shown). The load cell is arranged between the mover 61 and the holder 63 of the load applying mechanism 6, measures the amount of strain in the load cell caused by the load when the steel ball 30 is pressed against the disk 20, and measures the amount of strain. This signal is output to the amplifier section. When the signal output from the load cell is input, the amplifier unit converts the amount of strain into a load value (or stress value), displays the load value, and transmits signals and data corresponding to the load value to the computer unit 9 or the It outputs to an external device such as the pressing load control unit 17, which will be described later.

The torque measuring section 14 measures the transmission torque T during rotation of the steel ball 30, which is a body of rotation. Specifically, the torque measuring unit 14 is provided with a torque meter 55 arranged between the shaft 31 connected to the steel ball 30 and the shaft 51 of the rotary body rotating mechanism 5 . The torque meter 55 comprises a main body 56 and a shaft 57 and measures the transmission torque T acting on the shaft 57 . Specifically, since the shaft 57 twists when it rotates, the torque meter 55 measures the strain amount of the shaft 57 caused by this twist, converts it into a transmission torque T transmitted through the shaft 57, and outputs the torque. . One end of the shaft 57 is connected to the shaft 51 via the coupling 52, and the other end is connected to the shaft 31 via the coupling 53, so no slip occurs. Therefore, by measuring the transmission torque T of the shaft 57, the torque meter 55 can measure the transmission torque T during rotation of the steel ball 30, which is a rotating body. Further, the torque meter 55 can output a signal or data corresponding to the measured transmission torque T to the computer section 9 directly or via another device.

The display section 10 is also called an information display or a display monitor, and when a video signal output from the computer section 9 is input, it displays characters, graphic information, etc. corresponding to the video signal. Specifically, the display unit 10 displays the selected interference color image from among the interference color images recorded in the image recording unit 11 and the film thickness distribution of the lubricant LB estimated by the film thickness distribution estimation unit 12. It displays an image or the like in the form of a two-dimensional distribution or graph.

FIG. 2(b) shows an enlarged view of the film thickness measurement target region R in FIG. 2(a), showing an example of an optical model of the contact surface. The illumination light L2 irradiates the film thickness measurement target region R, and light (reflected light) L3 reflected from the contact portion SP is obtained. Here, the reflected light L3 is divided into a reflected light L31 at the interface between the disk 20 and the Cr film of the metal thin film 21 and a reflected light L32 at the interface between the lubricant LB and the steel ball 30 to form interference fringes. Of the lights L31 and L32, the light L4 that has passed through the objective lens 83 and the half mirror 82 can be imaged by the imaging lens 84 on the imaging device 86 of the imaging camera 80. FIG. At this time, by photographing the interference fringe image obtained through the light L4 with the imaging camera 80, the RGB intensity of each pixel in the film thickness analysis target image, that is, the light intensity I(λ) can be obtained. The light intensity I(λ) can be converted into reflectance, for example.

In the film thickness distribution measuring apparatus 1 of the embodiment described above, a static load is applied to the steel ball 30 and the disc 20 by the load applying mechanism 6 . On the other hand, the film thickness distribution measuring apparatus 1 according to another embodiment shown in FIG. to take an image of the contact surface.

In the embodiment of FIG. 3( a ), the steel balls 30 are housed in the container 101 and positioned below the disk 20 , and between the lubricant LB and the steel balls 30 , the lubricant LB exists. The disc 20 is housed in an arm of a lever 120 having a fulcrum 123 and an accelerometer 121 on the other arm of the lever 120 .

A small steel ball 112 and a coil spring 110 are arranged on the opposite side of the disc 20 and the steel ball 30 with the fulcrum 123 of the lever 120 as the center. The restoring force of the coil spring 110 shoots a small steel ball 112 to collide with the arm (in the direction of arrow A), and the acting force can be applied as an impact force to the contact portion between the disk 20 and the steel ball 30 ( arrow B direction). At this time, the accelerometer 121 detects the timing of impulsive force application, and the contact surface image is acquired by the imaging camera 80 (interference color imaging unit 8) composed of a high-speed camera. That is, the coil spring 110, the small steel ball 112, and the lever 120 cause the substrate 2 (disk 20) and the steel ball 30, which is the piece of contact, to collide with each other, and the contact portion between the substrate 2 (disk 20) and the steel ball 30 It functions as an impact force application mechanism that applies an impact force to.

Next, Experiment 1 performed using the film thickness distribution measuring apparatus 1 shown in FIG. 3(a) will be described. A flat plate (material: BK-7, diameter: 25 mm, thickness: 2 mm), which is a glass main body as the disk 20, is brought into contact with the steel ball 30 (material: SUJ2, diameter: 19.1 mm), and the contact portion is Lubricant LB was injected into and held by the meniscus. A small steel ball 112 (diameter: 19.1 mm, mass: 3.0 g) was shot by the restoring force of the coil spring 110 to collide with the arm of the lever 120, and the acting force was applied to the contact surface as an impact force. The timing of impulsive force application was detected by the accelerometer 121, and the image of the contact surface was acquired by the imaging camera 80 composed of a high-speed camera. Then, the buffering characteristics were evaluated from the time change of the film thickness identified by the film thickness analysis described below.

In order to measure the film thickness of the lubricant LB at a high speed and also to measure its distribution state, the present experiment using a unique optical interference film thickness measurement method using three wavelengths (RGB) light showed clear interference fringes A metal thin film 21, which is a semi-reflecting film, was formed from a Cr film. In addition, a spacer layer was provided to increase the optical path in order to measure with high accuracy even when the lubricating film thickness is small. In Sample 1, which will be described later, as shown in FIG. 1(b), a transparent film 22 was formed from a SiO ₂ film as a spacer layer.

Also in the embodiment of FIG. 3(a), there is a measurement target area R as shown in FIG. 2(b). The reflected light L3 is divided into a reflected light L31 at the interface between the disk 20 and the metal thin film 21 and a reflected light L32 at the interface between the lubricant LB and the steel ball 30 to form interference fringes. An interference fringe image obtained through the light L4 as a medium was captured by the imaging camera 80 to obtain the RGB intensity of each pixel in the film thickness analysis target image, that is, the light intensity I(λ). The light intensity I(λ) is obtained, for example, in the form of reflectance.

Here, the incoming irradiation light L2 contains three types of three-wavelength components (λ=420 nm, 515 nm, and 650 nm) by the three-wavelength bandpass filter 73, and the reflected light L31 and the reflected light L32 are respectively reflected at the two interfaces described above. to form interference fringes. An imaging camera 80 (maximum imaging speed: 540 kHz), which is a high-speed camera, captured an interference fringe image obtained using the light L4 as a medium to obtain the RGB intensity of each pixel in the film thickness analysis target image. This RGB intensity was taken as light intensity I(λ). Also, for reference, I _ref (λ) was obtained from an observed image of the Si wafer taken under the same shooting conditions. Furthermore, considering the influence of the light sensitivity characteristics of the camera, crosstalk correction was performed on I(λ) and I _ref (λ) to obtain I′(λ) and I′ _ref (λ).

Using the known Si wafer reflectance R _ref (λ), the reflectance R(λ)=R _ref (λ)/I′ _ref (λ)×I′(λ) was calculated. In each pixel _, assuming the multi-layer optical model _{of FIG} . The film thickness distribution estimator 12 calculated the film thickness h by theoretically calculating the reflectance R _num (λ) and minimizing the error from R(λ). This film thickness measurement method can be applied to the film thickness distribution measurement of various multilayer films by correcting the optical model.

The sample 1 used in this experiment consists of a substrate 2 (disk 20) on which a Cr film (thickness: 5 nm) as the metal thin film 21 and a SiO ₂ film (thickness: 580 nm) as the transparent film 22 are formed, and an untreated is a combination of steel balls 30 of This SiO ₂ film serves as a spacer layer.

For this sample, the disk 20 was brought into contact with the steel ball 30 under a static load of 10 N, and an impact force was applied while the lubricating agent LB was held by the meniscus, and changes over time in the acceleration a and the film thickness h were measured. The sampling frequency of the accelerometer 121 was set to 1 MHz, and the imaging speed of the imaging camera 80 was set to 10 kHz. The experiment was carried out at room temperature of 25° C. and humidity of 40%.

FIG. 4 shows temporal changes in profiles of acceleration a, contact circle diameter φ, and film thickness h as experimental results of sample 1. In FIG. The time at which the accelerometer 121 detected the application of the impact force was t=0 ms. Also, the film thickness h is shown in the form of a value in the radial direction X with the center of the measurement target region R being 0. As shown in FIG. In the graph at the bottom of FIG. 4, the value of the film thickness h is small and values close to 570 nm are distributed from 0 μm at the center to around ±110 μm above and below in the radial direction X. FIG. The value of the film thickness h fluctuates around ±110 μm in the radial direction X, and increases to around 700 nm further outside in the radial direction X.

FIG. 5 shows the profile of film thickness h at t=0 ms. Here, the film thickness h is the total film thickness of the lubricant LB film thickness and the spacer layer layer (the SiO ₂ film as the transparent film 22 or the CPB film on the surface of the steel ball 30). The osculating circle diameter φ is the diameter of the outermost circumference circle of the minimum film thickness _hmin , and is within the range indicated by the arrow in FIG.

The osculating circle diameter φ was φ=214 μm for sample 1 at t=0 ms. Before the impact force was applied (t<0 ms), no change in contact circle diameter φ was observed.

Immediately after the impact force was applied, sample 1 increased to φ = 223 µm at t = 1.7 ms, decreased to φ = 133 µm at t = 4.2 ms, and the contact circle diameter changed while repeating increases and decreases until t = 40 ms. It did not converge even at the time point. The frequency of the damped oscillation that appeared at φ was 266 Hz.

When calculating the contact surface diameter φ with a static load of 10 N using Hertz's contact theory, φ=216 mm, which matches the contact circle diameter at t=0 ms. The natural frequency fn of the experimental system is 2.1×10 ⁴ Nm/rad in contact stiffness (spring constant) between the steel ball 30 and the substrate 2 (disk 20) and 2.0 in stiffness (spring constant) of the glass flat plate. Assuming a series connection of ×10 ⁴ Nm/rad (combined spring constant 1.0×10 ⁴ Nm/rad), fn=270 Hz is calculated from the moment of inertia of the lever mechanism of 3.6×10 ⁻³ kgm ² . Since the value of the natural frequency fn substantially matches the vibration frequency of the contact surface diameter φ that appeared in the experiment, the change in film thickness depends on the contact stiffness between the steel ball 30 and the substrate 2 (disk 20) and the substrate 2 ( It is considered that this is caused by the rigidity of the disk 20).

As described above, many types of information can be obtained by obtaining the intensity (reflectance) of light of at least three wavelengths using the film thickness distribution measuring apparatus 1 of the embodiment. In particular, according to the experiment using the impact force generated by the film thickness distribution measuring apparatus 1 shown in FIG. 3(a), it is possible to obtain many types of information in a short time compared to the experiment in which a static load is applied. Also, it is possible to conduct the experiment while rotating the steel ball 30, in which case information including the effect of the fluid film can be obtained.

Next, Experiment 2 performed using the film thickness distribution measuring apparatus 1 shown in FIG. 3(a) will be described. The following two types of samples, Sample 2 and Sample 3, were used in this experiment. Sample 2 corresponds to the model diagram of FIG _. A plate 20) was used.

On the other hand, Sample 3 corresponds to the model diagram of FIG. 3(b). In FIG. 3B, the metal thin film 21 on the disk 20 made of glass is the first metal thin film 21, and the transparent film 22 is further provided on the transparent film 22, which is the second metal thin film. of metal thin film 23 is used. For example, the first metal thin film 21 is a Cr film, and the second metal thin film 23 is an Fe film.

Here, the second metal thin film 23 corresponds to an object with which the steel ball 30 comes into contact under the environment in which the steel ball 30 is actually used. By forming the second metal thin film 23 from the Fe film, the experiment can be conducted in a situation closer to the actual use environment in which there is a member made of Fe with which the steel ball 30 comes into contact. Improves usability. In sample 3, a Cr film (film thickness: 7 nm) was formed as the first metal thin film 21, a SiO ₂ film (film thickness: 500 nm) as the transparent film 22, and an Fe film (film thickness: 500 nm) as the second metal thin film 23. : 10 nm) was used. However, the wavelengths of the irradiation light in Experiment 2 were 470 nm (blue), 560 nm (green), and 645 nm (red). Other conditions are the same as Experiment 1.

FIG. 6 shows observation images of the measurement target regions R of samples 2 and 3, including (a) an image of sample 2 obtained by spectroscopy, (b) an image of sample 3 obtained by spectroscopy, and (c) SLIM (Spacer Layer Imaging Method) method, (d) an interference image of sample 3 used in the SLIM method, (e) an interference image of sample 2 using the film thickness distribution measuring apparatus 1 of the present embodiment, ( f) Interference images of Sample 3 using the film thickness distribution measuring apparatus 1 of the present embodiment are respectively shown.

FIGS. 6(a) and (b) show images of samples 2 and 3 by spectroscopy. Spectroscopy is a method that has been practiced in the past, and a line having a predetermined width in the measurement target region R, for example, a line in a direction perpendicular to the paper surface in the middle part of the measurement target region R in FIG. It is a method of spectrally separating incoming light for each wavelength λ using a prism or the like, and is a highly accurate measurement method. In FIGS. 6A and 6B, the horizontal axis corresponds to the wavelength λ (wavelength increases from left to right). On the other hand, the vertical axis represents spatial information, that is, the direction of one row. This is the portion where the film thickness is the thinnest. In this image, the band-like portion in the center expands in the vertical direction as it goes to the right of the horizontal axis. 2(a) (in the middle part of the measurement target region R in FIG. 2A). A longer wavelength means a thicker film thickness, meaning that the film thickness increases toward the outside.

6(c) and (d) show images of samples 2 and 3 used in the SLIM method. The SLIM method is also a method that has been conventionally practiced, and is a method that can calculate the film thickness based on the relationship between the tint (RGB hue) of the obtained image and the film thickness, and is disclosed in Patent Document 1. is a similar method. In this image, the circular portion in the center corresponds to the portion where the film thickness of the lubricant LB is the thinnest, and the film thickness increases toward the outside from that portion.

FIGS. 6(e) and 6(f) show images of samples 2 and 3 using the film thickness distribution measuring apparatus 1 of the present embodiment, and the photographing method is as described above. Similar to FIGS. 6(c) and (d), in this image, the circular portion in the center corresponds to the portion where the film thickness of the lubricant LB is the thinnest, and the film thickness increases outward from that portion. It shows that it is thicker.

Then, the film thickness distribution estimating unit 12 of the computer unit 9 acquires the intensity and reflectance for each pixel of the irradiation light of the three wavelengths based on each image of FIG. 6 recorded in the image recording unit 11. , the film thickness distribution of the lubricant LB at the contact portion SP between the substrate 2 and the contact piece 3 was calculated from the reflectance. A display 10 can display these values in the form of a graph. 7 to 11 are graphs displayed by the display unit 10. FIG.

7A and 7B are graphs showing reflectance in the radial direction X when irradiated with blue wavelength (470 nm) light, where (a) is the graph for sample 2 and (b) is the graph for sample 3. FIG. FIG. 8 is a graph showing the reflectance in the radial direction X at the time of irradiation with green wavelength (560 nm) light, where (a) is the graph for sample 2 and (b) is the graph for sample 3. 9A and 9B are graphs showing the reflectance in the radial direction X when irradiated with red wavelength (645 nm) light, where (a) is the graph for sample 2 and (b) is the graph for sample 3. It is understood that the reflectance obtained by the film thickness distribution measuring apparatus 1 of the present embodiment and the reflectance obtained by spectroscopy are in good agreement.

10A and 10B are graphs showing the reflectance with respect to the wavelength of the interference light at the central position of the measurement target region R, where (a) is the graph for sample 2 and (b) is the graph for sample 3. FIG. It is understood that the reflectance obtained by the film thickness distribution measuring apparatus 1 of the present embodiment and the reflectance spectrum (frequency characteristics dependent on the wavelength λ) obtained by spectroscopy are in good agreement. In this experiment, in this embodiment, only the reflectance at the wavelengths of three points (blue wavelength 470 nm, green wavelength 560 nm, red wavelength 645 nm) was obtained, but the reflectance at these three points was obtained by spectroscopy. It agrees well with the reflectance spectrum, and it is possible to obtain the film thickness with only three points of information.

11A and 11B are graphs showing the film thickness distribution in the radial direction X, where (a) is the graph for sample 2 and (b) is the graph for sample 3. FIG. The film thickness h can be calculated based on the reflectances shown in FIGS. FIG. 11A shows that the film thickness obtained by the film thickness distribution measuring apparatus 1 of this embodiment, the film thickness obtained by the spectroscopic method, and the film thickness obtained by the SLIM method are in good agreement. is shown.

On the other hand, FIG. 11B shows that the film thickness obtained by the film thickness distribution measuring apparatus 1 of the present embodiment and the film thickness obtained by the spectroscopic method are relatively consistent, whereas the film thickness obtained by the SLIM method is relatively consistent. The obtained film thicknesses are inconsistent, indicating the low precision of the SLIM method. That is, when the first metal thin film 21 (Cr) film and the second metal thin film 23 (Fe film) exist as shown in FIG. Although the film thickness can be obtained with high accuracy, the precision of the film thickness obtained by the SLIM method is not good.

That is, the SLIM method utilizes the relationship between the hue and the film thickness, and it is difficult to say that it is effective for such a minute change in film thickness that the color does not change much. For example, in the case of the first metal thin film 21 (Cr) film and the second metal thin film 23 (Fe film), the light interference generated between the first metal thin film 21 and the second metal thin film 23 causes the lubricant LB to Since the image is always emphasized regardless of the film thickness, there is little change in color tone, and the SLIM method is not effective.

On the other hand, according to the film thickness distribution measuring apparatus 1 of the present embodiment, even in the case of the first metal thin film 21 (Cr) film and the second metal thin film 23 (Fe film), the reflectance is used, it is possible to measure the film thickness with high accuracy.

In this embodiment, an optical interference image generated by three kinds of wavelengths is captured, and the intensity (for example, reflectance) of the three wavelengths is obtained from the image corresponding to the three kinds of wavelengths, that is, the RGB image, and the optical interference multilayer structure is obtained. The spatial distribution of the film thickness of the lubricant can be measured by performing identification analysis of the film thickness using the multi-beam model.

It should be noted that the present invention is not limited to the above-described embodiments, and can be modified, improved, etc. as appropriate. In addition, the material, shape, size, numerical value, form, number, location, etc. of each component in the above-described embodiment are arbitrary and not limited as long as the present invention can be achieved.

1 film thickness distribution measuring device 2 substrate 3 contact piece 4 moving mechanism 5 rotating body rotating mechanism 6 load applying mechanism 7 light source unit 8 interference color imaging unit 9 computer unit 10 display unit 11 image recording unit 12 film thickness distribution estimating unit 14 torque Measurement unit 20 disk (one type of substrate)
21 Metal thin film 22 Transparent film 30 Steel ball (contact piece/one type of rotating body)
31 Shaft 40 Rotating motor 41 Connecting member 50 Rotating motor 51 Shaft 55 Torque meter 56 Body 57 Shaft 60 Actuator 61 Mover 63 Holder 65 Pressing load measuring unit (load cell)
70 Lighting unit 72 White lamp 75 Lighting power supply 80 Imaging camera 81 Lens unit 82 Half mirror 83 Objective lens 84 Imaging lens 85 Color filter 86 Imaging element LB Lubricant SP Contact portion RB between substrate and steel ball Rotation radius R of steel ball Film thickness measurement target area L1 Light L2 irradiated from the light source section Light L3 irradiated to the film thickness measurement target area Light reflected from the film thickness measurement target area (interference light)
Light passing through the L4 half mirror (interference light captured)
T transmission torque

Claims (5)

A film thickness distribution measuring device for measuring the film thickness distribution of a lubricant that lubricates contact portions between objects in an EHL state,
a substrate having optical transparency;
a contact piece that contacts the substrate via the lubricant;
a light source unit that irradiates light containing at least three wavelengths toward a contact portion between the substrate and the contact piece;
an interference color imaging unit that captures an image of the light reflected from the contact portion between the substrate and the contact piece through the substrate and acquires color interference fringes as an interference color image;
Equipped with a computer section,
The computer section includes
an image recording unit for recording the interference color image captured by the interference color imaging unit;
From the interference color images recorded in the image recording unit, the color information of each point included in the selected interference color image is color-separated for each of the at least three wavelengths of light, and the intensity of each wavelength is obtained. and calculating the film thickness distribution of the lubricant at the contact portion between the substrate and the contact piece based on the intensity. The film thickness distribution measuring device according to claim 1,
The film thickness distribution estimation unit calculates the reflectance from the intensity, and calculates the film thickness distribution based on the reflectance.
Film thickness distribution measuring device. The film thickness distribution measuring device according to claim 1,
further comprising an impact force applying mechanism for causing the substrate and the contact piece to collide with each other and applying an impact force to the contact portion between the substrate and the contact piece;
The interference color imaging unit is composed of a high-speed camera,
Film thickness distribution measuring device. The film thickness distribution measuring device according to claim 1,
The substrate comprises a main body made of glass, a first metal thin film on the main body, a transparent film formed on the first metal thin film, and a second metal film formed on the transparent film. a thin film;
Film thickness distribution measuring device. The film thickness distribution measuring device according to claim 4,
wherein the first metal thin film is a Cr film and the second metal thin film is an Fe film;
Film thickness distribution measuring device.

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