JP5958627B1 - Sliding device - Google Patents
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Abstract
【課題】煩雑な作業を行うことなく、摺動面間に存在する透明膜の膜厚を計測することができるようにする。【解決手段】透明摺動材42と反射摺動材48とは、荷重を受けながら相対運動し、液体膜46は、透明摺動材42と反射摺動材48との間に存在し、透明摺動材42及び液体膜46は、光を透過する材質から構成され、反射摺動材48は、光を反射する材質から構成される。白色光源22からの光を、バンドパスフィルタを用いて3波長の単色光から構成される光にし、透明摺動材42と液体膜46とを透過させて反射摺動材48へ照射して光干渉を生じさせ、カメラ32は、生じた光干渉における、波長が異なる2以上の光の各々の輝度を計測する。演算装置60は、カメラ32によって計測された2以上の光の各々の輝度に基づいて、液体膜46の膜厚を計算する。【選択図】図7An object of the present invention is to measure the film thickness of a transparent film existing between sliding surfaces without performing a complicated operation. A transparent sliding member 42 and a reflective sliding member 48 move relative to each other while receiving a load, and a liquid film 46 exists between the transparent sliding member 42 and the reflective sliding member 48 and is transparent. The sliding material 42 and the liquid film 46 are made of a material that transmits light, and the reflective sliding material 48 is made of a material that reflects light. The light from the white light source 22 is converted into light composed of monochromatic light of three wavelengths using a band-pass filter, and is transmitted through the transparent sliding material 42 and the liquid film 46 to irradiate the reflective sliding material 48. The interference is generated, and the camera 32 measures the luminance of each of the two or more lights having different wavelengths in the generated optical interference. The arithmetic device 60 calculates the film thickness of the liquid film 46 based on the brightness of each of the two or more lights measured by the camera 32. [Selection] Figure 7
Description
本発明は、透明膜の膜厚を計測する摺動装置に関する。 The present invention relates to a sliding device that measures the film thickness of a transparent film.
従来より、摺動面の透明膜厚さ計測の中でも油膜厚さ計測に特化した摺動装置が知られている(非特許文献1、2)。膜厚計測の基本原理は光干渉法である。油中において、部分反射膜(クロム)及び保護膜(シリカ)がコートされた透明ディスク(ガラス、サファイア)で鋼球を摩擦し、摺動面間に油膜を形成する。透明ディスク越しに鋼球の摺動面へ白色光を照射する。この白色光はブロードなスペクトルを持っており、波長制御されていない。すると照射した光の一部はクロム膜に反射され、残りはシリカ層内、油膜内を通り鋼球に反射して戻ることで光の光路差が生まれて、光干渉が生じる。この干渉色を、デジタルカラーCCDカメラを用いて撮影し、撮像を、画像集録ボードを用いてコンピュータへRGB輝度分布として取り込む。これらのRGB輝度分布を画像処理によりHSV輝度分布に変換し、その中のH(Hue,色相)の分布を用いる。 Conventionally, a sliding device specialized in oil film thickness measurement is known among the transparent film thickness measurement of a sliding surface (Non-Patent Documents 1 and 2). The basic principle of film thickness measurement is optical interferometry. In oil, a steel ball is rubbed with a transparent disk (glass, sapphire) coated with a partially reflective film (chrome) and a protective film (silica) to form an oil film between sliding surfaces. White light is irradiated to the sliding surface of the steel ball through the transparent disk. This white light has a broad spectrum and is not wavelength-controlled. Then, a part of the irradiated light is reflected by the chromium film, and the remaining light passes through the silica layer and the oil film and reflects back to the steel ball, so that an optical path difference of the light is generated and optical interference occurs. The interference color is photographed using a digital color CCD camera, and the image is captured as an RGB luminance distribution into a computer using an image acquisition board. These RGB luminance distributions are converted into HSV luminance distributions by image processing, and the distribution of H (Hue, hue) is used.
また、事前に膜厚が既知の透明膜試料を用いて実験的に作成した色相−膜厚の較正表を用いて、色相分布を膜厚分布に変換する。 Further, the hue distribution is converted into the film thickness distribution using a hue-film thickness calibration table experimentally created using a transparent film sample whose film thickness is known in advance.
上記の非特許文献1に記載の技術では、干渉色を透明膜厚さへ変換するには、色相−膜厚の較正表を作成しなくてはならない。作成には、膜厚が既知かつ連続的に変化する透明膜を用意し、それを、油膜計測を行いたい試験片と同一の分光反射率、すなわち同様の色と反射率を持つ材料と光干渉用の透明ディスクで挟んで、光干渉を生じさせる必要がある。これを実現するには様々な方法があるが、代表的な方法は油膜計測に用いる試験片と同一の分光反射率を持つ球を用意し、それをディスクに押し当て、透明膜として球とディスク間のすき間(空気膜厚さ)を用いる方法である。接触点ではすき間がゼロであること、また接触点からのすき間分布は球の曲率から算出できることから、膜厚が既知となり干渉色の色相と膜厚を紐付けることができる。しかしながら、非特許文献1にも示されるように色相−膜厚の関係は複雑な曲線であり、ある程度の細かい間隔ですき間値と色相値を計測しなくてはいけないため、非常に煩雑な作業になる。さらに、試験片の色や油の色、また光学系(カメラやレンズ、照明)が変化する度に較正曲線を作成し直さなくてはならない。 In the technique described in Non-Patent Document 1, a hue-film thickness calibration table must be created in order to convert an interference color into a transparent film thickness. For the preparation, a transparent film with a known and continuously changing film thickness is prepared, and this is used for optical interference with a material having the same spectral reflectance, that is, the same color and reflectance as the specimen for which an oil film is to be measured. Therefore, it is necessary to cause optical interference by sandwiching it with a transparent disk. There are various ways to achieve this, but the typical method is to prepare a sphere with the same spectral reflectance as the specimen used for oil film measurement, press it against the disk, and use the sphere and disk as a transparent film. This is a method using a gap (air film thickness). Since the gap at the contact point is zero and the gap distribution from the contact point can be calculated from the curvature of the sphere, the film thickness is known, and the hue of the interference color and the film thickness can be linked. However, as shown in Non-Patent Document 1, the relationship between hue and film thickness is a complicated curve, and it is necessary to measure the gap value and the hue value at a certain fine interval. Become. In addition, the calibration curve must be recreated each time the color of the specimen, the color of the oil, or the optical system (camera, lens, illumination) changes.
本発明は、上記の事情を鑑みてなされたもので、煩雑な作業を行うことなく、透明膜の膜厚を計測することができる摺動装置を得ることが目的である。 The present invention has been made in view of the above circumstances, and an object of the present invention is to obtain a sliding device that can measure the film thickness of a transparent film without performing complicated operations.
第1の発明に係る摺動装置は、第1の摺動材料、第2の摺動材料、透明膜、光検出器、光源、及び演算装置を備えた摺動装置であって、前記第1の摺動材料と前記第2の摺動材料とは、荷重を受けながら相対運動し、前記透明膜は、前記第1の摺動材料と前記第2の摺動材料との間に存在し、前記第1の摺動材料及び前記透明膜は、光を透過する材質から構成され、前記第2の摺動材料は、光を反射する材質から構成され、前記光源からの光を、前記第1の摺動材料と前記透明膜とを透過させて前記第2の摺動材料へ照射して光干渉を生じさせ、前記光検出器は、複数の計測点について、前記生じた光干渉後の光から単色光と見なせる程度に狭い波長幅の光の輝度を計測し、その際に計測する波長数は2以上であり、前記演算装置は、前記光検出器によって前記計測点の各々について計測された前記2以上の光の各々の輝度に基づいて、前記2以上の光の各々の輝度と前記透明膜の膜厚との関係を表す関係式であって、前記計測点の各々における前記透明膜の膜厚、及び前記計測点の各々において同一であると仮定した測定環境由来の未知変数を含む関係式から、前記計測点の各々における前記透明膜の膜厚、及び前記測定環境由来の未知変数を求め、前記透明膜は液体膜である。
第2の発明に係る摺動装置は、第1の摺動材料、第2の摺動材料、透明膜、光検出器、光源、及び演算装置を備えた摺動装置であって、前記第1の摺動材料と前記第2の摺動材料とは、荷重を受けながら相対運動し、前記透明膜は、前記第1の摺動材料と前記第2の摺動材料との間に存在し、前記第1の摺動材料及び前記透明膜は、光を透過する材質から構成され、前記第2の摺動材料は、光を反射する材質から構成され、前記光源からの光を、前記第1の摺動材料と前記透明膜とを透過させて前記第2の摺動材料へ照射して光干渉を生じさせ、前記光検出器は、複数の計測点について、前記生じた光干渉後の光から単色光と見なせる程度に狭い波長幅の光の輝度を計測し、その際に計測する波長数は2以上であり、前記演算装置は、前記光検出器によって前記計測点の各々について計測された前記2以上の光の各々の輝度に基づいて、前記2以上の光の各々の輝度と前記透明膜の膜厚との関係を表す関係式であって、前記計測点の各々における前記透明膜の膜厚、及び前記計測点の各々において同一であると仮定した測定環境由来の未知変数を含む関係式から、前記計測点の各々における前記透明膜の膜厚、及び前記測定環境由来の未知変数を求め、前記測定環境由来の未知変数は、前記透明膜の、前記2以上の光の各々に対する吸光係数、及び前記透明膜の、前記2以上の光の各々に対する屈折率の少なくとも一方を含む。
A sliding device according to a first aspect of the present invention is a sliding device including a first sliding material, a second sliding material, a transparent film, a photodetector, a light source, and an arithmetic device, The sliding material and the second sliding material move relative to each other while receiving a load, and the transparent film exists between the first sliding material and the second sliding material, The first sliding material and the transparent film are made of a material that transmits light, and the second sliding material is made of a material that reflects light, and transmits light from the light source to the first film. The light is transmitted through the transparent film and irradiated to the second sliding material to cause optical interference, and the photodetector detects the light after the generated optical interference at a plurality of measurement points. In this case, the brightness of light having a wavelength range narrow enough to be regarded as monochromatic light is measured, and the number of wavelengths to be measured at that time is two or more. Based on the luminance of each of the two or more light measured for each of the measurement points by the output device, a relational expression representing a relationship between the thickness of the transparent film and the luminance of each of the two or more light Then, from the relational expression including the film thickness of the transparent film at each of the measurement points and the unknown variable derived from the measurement environment assumed to be the same at each of the measurement points, the transparent film at each of the measurement points A film thickness and an unknown variable derived from the measurement environment are obtained, and the transparent film is a liquid film.
A sliding device according to a second invention is a sliding device comprising a first sliding material, a second sliding material, a transparent film, a photodetector, a light source, and an arithmetic device, The sliding material and the second sliding material move relative to each other while receiving a load, and the transparent film exists between the first sliding material and the second sliding material, The first sliding material and the transparent film are made of a material that transmits light, and the second sliding material is made of a material that reflects light, and transmits light from the light source to the first film. The light is transmitted through the transparent film and irradiated to the second sliding material to cause optical interference, and the photodetector detects the light after the generated optical interference at a plurality of measurement points. In this case, the brightness of light having a wavelength range narrow enough to be regarded as monochromatic light is measured, and the number of wavelengths to be measured at that time is two or more. A relational expression representing the relationship between the brightness of each of the two or more lights and the film thickness of the transparent film, based on the brightness of each of the two or more lights measured for each of the measurement points by an output device. Then, from the relational expression including the film thickness of the transparent film at each of the measurement points and the unknown variable derived from the measurement environment assumed to be the same at each of the measurement points, the transparent film at each of the measurement points A film thickness and an unknown variable derived from the measurement environment are obtained, and the unknown variable derived from the measurement environment includes the absorption coefficient of the transparent film for each of the two or more lights, and the two or more lights of the transparent film. At least one of the refractive indices for each of the above.
第1の発明及び第2の発明に係る摺動装置では、前記光源からの光を、前記第1の摺動材料と前記透明膜とを透過させて前記第2の摺動材料へ照射して光干渉を生じさせ、前記光検出器は、複数の計測点について、前記生じた光干渉後の光から単色光と見なせる程度に狭い波長幅の光の輝度を計測し、その際に計測する波長数は2以上である。そして、前記演算装置は、前記光検出器によって前記計測点の各々について計測された前記2以上の光の各々の輝度に基づいて、前記透明膜の膜厚を計算する。 In the sliding device according to the first invention and the second invention , the light from the light source is irradiated to the second sliding material through the first sliding material and the transparent film. The optical detector generates light interference, and the light detector measures the luminance of light having a narrow wavelength width to a degree that can be regarded as monochromatic light from the light after the generated light interference at a plurality of measurement points, and the wavelength to be measured at that time The number is 2 or more. And the said arithmetic unit calculates the film thickness of the said transparent film based on each brightness | luminance of the said 2 or more light measured about each of the said measurement point with the said photodetector.
このように、光源からの光を、前記第1の摺動材料と前記透明膜とを透過させて前記第2の摺動材料へ照射して光干渉を生じさせ、生じた光干渉における、波長が異なる2以上の光の各々の輝度を計測し、前記光検出器によって計測された前記2以上の光の各々の輝度に基づいて、前記透明膜の膜厚を計算することにより、煩雑な作業を行うことなく、透明膜の膜厚を計測することができる。 As described above, the light from the light source is transmitted through the first sliding material and the transparent film and irradiated to the second sliding material to cause optical interference. By measuring the brightness of each of the two or more lights having different values, and calculating the film thickness of the transparent film based on the brightness of each of the two or more lights measured by the photodetector. The film thickness of the transparent film can be measured without performing the above.
本発明に係る光検出器は、複数の計測点について、前記2以上の光の各々の輝度を計測し、前記演算装置は、前記光検出器によって前記計測点の各々について計測された前記2以上の光の各々の輝度に基づいて、前記2以上の光の各々の輝度と前記透明膜の膜厚との関係を表す関係式であって、前記計測点の各々における前記透明膜の膜厚、及び前記計測点の各々において同一であると仮定した測定環境由来の未知変数を含む関係式に対して、連立方程式を解くか、又は最適化手法により、前記計測点の各々における前記透明膜の膜厚、及び前記測定環境由来の未知変数を求めるようにすることができる。 The photodetector according to the present invention measures the luminance of each of the two or more lights at a plurality of measurement points, and the arithmetic unit is configured to measure the two or more of the measurement points measured by the photodetector. A relational expression representing the relationship between the brightness of each of the two or more lights and the film thickness of the transparent film, based on the brightness of each of the light, and the film thickness of the transparent film at each of the measurement points, And a film of the transparent film at each of the measurement points by solving simultaneous equations or an optimization method for a relational expression including unknown variables derived from the measurement environment assumed to be the same at each of the measurement points. Thickness and unknown variables derived from the measurement environment can be obtained.
上記の測定環境由来の未知変数は、前記2以上の光の各々の表面光強度、及び前記2以上の光の各々の、前記透明膜による吸光が生じない場合の裏面光強度を含むようにすることができる。 The unknown variables derived from the measurement environment include the surface light intensity of each of the two or more lights and the back light intensity of each of the two or more lights when no absorption by the transparent film occurs. Can do.
上記の測定環境由来の未知変数は、前記透明膜の、前記2以上の光の各々に対する吸光係数を含むようにすることができる。これにより、透明膜に着色があっても、膜厚を計測することができる。 The unknown variable derived from the measurement environment may include an extinction coefficient for each of the two or more lights of the transparent film. Thereby, even if the transparent film is colored, the film thickness can be measured.
上記の前記測定環境由来の未知変数は、前記透明膜の、前記2以上の光の各々に対する屈折率を含むようにすることができる。これにより、透明膜が、油膜などの屈折率の波長依存性の大きい材質であっても、膜厚を計測することができる。 The unknown variable derived from the measurement environment may include a refractive index for each of the two or more lights of the transparent film. Thereby, even if the transparent film is a material having a large wavelength dependency of the refractive index, such as an oil film, the film thickness can be measured.
上記の関係式は、以下の式で表わされる。 The above relational expression is represented by the following expression.
ただし、jは、前記2以上の光の各々に割り当てた番号を表し、iは、前記複数の計測点の各々に割り当てた番号を表し、I(i,j)は、前記光検出器によってi番目の計測点について計測されたj番目の光の輝度を表し、I1(j)は、j番目の光の表面光強度を表し、I2(j)は、j番目の光の、前記透明膜による吸光が生じない場合の裏面光強度を表し、α(j)は、前記透明膜のj番目の光に対する吸光係数を表し、n(j)は、前記透明膜のj番目の光に対する屈折率を表し、t(i)は、i番目の計測点における前記透明膜の膜厚を表し、λ(j)は、j番目の光の波長を表す。 Here, j represents a number assigned to each of the two or more lights, i represents a number assigned to each of the plurality of measurement points, and I (i, j) is i by the photodetector. Represents the luminance of the j-th light measured at the measurement point, I 1 (j) represents the surface light intensity of the j-th light, and I 2 (j) represents the transparent film of the j-th light. Represents the light intensity of the back surface when no light absorption occurs, α (j) represents the extinction coefficient for the jth light of the transparent film, and n (j) represents the refractive index of the transparent film for the jth light. T (i) represents the film thickness of the transparent film at the i-th measurement point, and λ (j) represents the wavelength of the j-th light.
上記の2以上の光の波長は200nm〜4,000nmである。 The wavelengths of the two or more lights are 200 nm to 4,000 nm.
上記の透明膜は液体膜である。 The transparent film is a liquid film.
上記の演算装置は、前記光検出器によって前記複数の計測点のうちの一部の計測点の各々について計測された前記2以上の光の各々の輝度に基づいて、前記関係式に対して、連立方程式を解くか、又は最適化手法により、前記計測点の各々における前記透明膜の膜厚、及び前記測定環境由来の未知変数を求め、前記光検出器によって前記複数の計測点のうちの残りの計測点の各々について計測された前記2以上の光の各々の輝度、及び前記求められた前記測定環境由来の未知変数に基づいて、前記計測点の各々について、前記2以上の光の各々の波長に対する、前記関係式を満たす前記計測点における前記透明膜の膜厚の候補値を求め、前記2以上の光の各々の波長に対する前記計測点における前記透明膜の膜厚の候補値から、波長間の合致法を用いて前記計測点における前記透明膜の膜厚値を決定することができる。 The above arithmetic device is based on the luminance of each of the two or more lights measured for each of some of the plurality of measurement points by the photodetector, and for the relational expression, Solve the simultaneous equations or optimize the thickness of the transparent film at each of the measurement points and the unknown variable derived from the measurement environment, and use the photodetector to detect the remaining of the plurality of measurement points. Each of the two or more lights for each of the measurement points based on the brightness of each of the two or more lights measured for each of the measurement points and the determined unknown variable derived from the measurement environment. A candidate value for the film thickness of the transparent film at the measurement point satisfying the relational expression with respect to a wavelength is obtained, and the wavelength from the candidate value for the film thickness of the transparent film at the measurement point for each wavelength of the two or more lights. Mate between Can determine the thickness value of said transparent film in the measuring points using.
上記の摺動装置は、前記光源から照射された光の光路上であって、前記光源と前記第1の摺動材料との間に設けられた、前記2以上の光の各々の波長を透過するバンドパスフィルタを更に含むようにすることができる。 The sliding device transmits a wavelength of each of the two or more lights provided on the optical path of the light emitted from the light source and provided between the light source and the first sliding material. It is possible to further include a band pass filter.
上記の摺動装置は、前記光干渉を生じた光の光路上であって、前記光検出器と前記第1の摺動材料との間に設けられた、前記2以上の光の各々の波長を透過するバンドパスフィルタ、又は前記2以上の光の各々に分光する光分光器を更に含むようにすることができる。
上記の光源を、フラッシュランプとすることができる。
第3の発明に係る摺動装置は、第1の摺動材料、第2の摺動材料、液体膜、光検出器、フラッシュランプ、及び演算装置を備えた摺動装置であって、前記第1の摺動材料と前記第2の摺動材料とは、荷重を受けながら相対運動し、前記液体膜は、前記第1の摺動材料と前記第2の摺動材料との間に存在し、前記第1の摺動材料及び前記液体膜は、光を透過する材質から構成され、前記第2の摺動材料は、光を反射する材質から構成され、前記フラッシュランプからの光を、前記第1の摺動材料と前記液体膜とを透過させて前記第2の摺動材料へ照射して光干渉を生じさせ、前記光検出器は、前記生じた光干渉後の光から単色光と見なせる程度に狭い波長幅の光の輝度を計測し、その際に計測する波長数は2以上であり、前記演算装置は、前記光検出器によって計測された前記2以上の光の各々の輝度に基づいて、前記液体膜の膜厚を計算する。
The above-mentioned sliding device is on the optical path of the light causing the optical interference, and is provided between the photodetector and the first sliding material, and each wavelength of the two or more lights. A band pass filter that transmits light, or an optical spectroscope that splits each of the two or more lights.
The light source can be a flash lamp.
A sliding device according to a third invention is a sliding device comprising a first sliding material, a second sliding material, a liquid film, a photodetector, a flash lamp, and an arithmetic device, The first sliding material and the second sliding material move relative to each other while receiving a load, and the liquid film exists between the first sliding material and the second sliding material. The first sliding material and the liquid film are made of a material that transmits light, and the second sliding material is made of a material that reflects light, and the light from the flash lamp is The first sliding material and the liquid film are transmitted to irradiate the second sliding material to cause optical interference, and the photodetector detects monochromatic light from the generated light interference light. The brightness of light having a wavelength width narrow enough to be considered is measured, and the number of wavelengths to be measured at that time is 2 or more, Based on the luminance of each of the measured said two or more light by the detector, to calculate the thickness of the liquid film.
以上説明したように本発明に係る摺動装置は、光源からの光を、前記第1の摺動材料と前記透明膜とを透過させて前記第2の摺動材料へ照射して光干渉を生じさせ、生じた光干渉における、波長が異なる2以上の光の各々の輝度を計測し、前記光検出器によって計測された前記2以上の光の各々の輝度に基づいて、前記透明膜の膜厚を計算することにより、煩雑な作業を行うことなく、透明膜の膜厚を計測することができる、という優れた効果を有する。 As described above, the sliding device according to the present invention transmits light from a light source through the first sliding material and the transparent film to irradiate the second sliding material to cause light interference. And measuring the brightness of each of the two or more lights having different wavelengths in the generated light interference, and based on the brightness of each of the two or more lights measured by the photodetector, the film of the transparent film By calculating the thickness, there is an excellent effect that the film thickness of the transparent film can be measured without performing complicated work.
以下、図面を参照して本発明の実施の形態を詳細に説明する。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
<本実施の形態の原理>
<透明膜の定義>
本実施の形態では、摺動材料の間に存在する透明膜の厚さ分布を計測可能な膜厚計測システムについて説明するが、その前に透明膜の定義を記す。本実施の形態において透明膜とは、水の膜のような透過による光の減衰をほぼ生じない膜のみを意味するのではなく、エンジン油の膜のような透過による光の減衰を生じる膜、すなわち着色透明膜も意味する。さらに、摺動面間に存在する光を透過する領域という意味において、液体や固体が含まれない場合の摺動面間のすき間も意味する。具体例としては、空気中や真空中で表面粗さを持つ表面同士が摺動する場合における表面粗さの谷部などである。本実施の形態では、特に指示の無い場合、透明膜は上記を意味する。
<Principle of this embodiment>
<Definition of transparent film>
In the present embodiment, a film thickness measurement system capable of measuring the thickness distribution of a transparent film existing between sliding materials will be described, but before that, the definition of the transparent film will be described. In the present embodiment, the transparent film does not mean only a film that hardly causes attenuation of light due to transmission such as a water film, but a film that causes attenuation of light due to transmission such as a film of engine oil, That is, it also means a colored transparent film. Furthermore, in the meaning of the area | region which permeate | transmits the light which exists between sliding surfaces, the clearance gap between sliding surfaces when a liquid and solid are not included is also meant. A specific example is a valley portion of surface roughness when surfaces having surface roughness slide in the air or in vacuum. In the present embodiment, the transparent film means the above unless otherwise specified.
<透明膜厚さ分布計測の重要性>
機械要素の摺動部では、多くの場合において摺動面間に透明膜が存在する。例えば、多くの摺動部は油などの液体で潤滑されており、それらの液体は多くの場合に透明であるため、摺動面間には透明膜が存在する。また、摺動材料と周囲の物質の化学反応により摺動材料表面に透明膜が形成されることがある。具体例としては、エンジン油中で鋼を摩擦した場合におけるZnDTPの反応被膜や大気中で鋼を摩擦した場合における酸化膜が挙げられる。これらはいずれも透明である。さらに、摺動面間に物体としての透明膜は存在しないが光を透過する領域が存在する場合がある。具体例としては、空気中や真空中で表面粗さを持つ表面同士が摺動する場合における表面粗さの谷部などである。このような場合においても、その領域の厚さ分布を計測することは有益である。なぜなら膜厚ゼロ点の分布は真実接触点分布を意味するためである。
<Importance of transparent film thickness measurement>
In a sliding portion of a machine element, a transparent film is often present between sliding surfaces. For example, many sliding portions are lubricated with a liquid such as oil, and these liquids are transparent in many cases, so that a transparent film exists between the sliding surfaces. Further, a transparent film may be formed on the surface of the sliding material due to a chemical reaction between the sliding material and surrounding substances. Specific examples include a ZnDTP reaction film when steel is rubbed in engine oil and an oxide film when steel is rubbed in the atmosphere. These are all transparent. Further, there is a case where a transparent film as an object does not exist between the sliding surfaces but there is a region that transmits light. A specific example is a valley portion of surface roughness when surfaces having surface roughness slide in the air or in vacuum. Even in such a case, it is beneficial to measure the thickness distribution of the region. This is because the distribution of zero film thickness means the true contact point distribution.
これらの透明膜厚さ分布は摩擦特性に影響するため、透明膜厚さ分布を計測することは摺動部設計において重要である。 Since these transparent film thickness distributions affect the friction characteristics, measuring the transparent film thickness distribution is important in the sliding part design.
<光干渉法>
透明膜厚さ分布、特に油膜厚さ分布の測定方法として広く普及している手法に「光干渉法」がある。これは光の干渉を用いて透明膜厚さを計測する手法である。
<Optical interference method>
As a method for measuring a transparent film thickness distribution, particularly an oil film thickness distribution, there is a “light interference method”. This is a method for measuring the transparent film thickness using light interference.
光干渉法の原理を図1に示す。摺動材の一方を、光を透過する材質で構成し、もう一方の摺動材の材料を光を反射する材質で構成する。以下、これらの摺動材をそれぞれ“透明摺動材”、“反射摺動材”と記す。光源から透明摺動材を透過させて透明膜越しにもう一方の摺動材へ光を照射する。このとき、透明摺動材と透明膜の屈折率差を適切に設定し、その界面で光を一部反射し一部透過するようにする。屈折率差が小さく反射が十分に生じない場合には、透明摺動材の透明膜と接する表面に部分反射膜を成膜する場合もある。 The principle of optical interferometry is shown in FIG. One of the sliding materials is made of a material that transmits light, and the other sliding material is made of a material that reflects light. Hereinafter, these sliding materials are referred to as “transparent sliding material” and “reflective sliding material”, respectively. The transparent sliding material is transmitted from the light source, and light is irradiated to the other sliding material through the transparent film. At this time, the difference in refractive index between the transparent sliding material and the transparent film is appropriately set so that light is partially reflected and partially transmitted at the interface. When the difference in refractive index is small and sufficient reflection does not occur, a partial reflection film may be formed on the surface of the transparent sliding material in contact with the transparent film.
透明膜を透過した光は反射摺動材で反射され、再び透明膜および透明摺動材を透過して光源方向に戻る。ここで、透明摺動材−透明膜界面で反射された光を“表面光”、反射摺動材で反射された光を“裏面光”と記す。表面波と裏面波は光路差が生じるため光干渉を生じ、反射摺動材表面を透明摺動材側から透明膜越しに光検出器(カメラ等)で観察すると、光干渉が観察される。この光干渉の色(波長と輝度)には光路差、すなわち透明膜厚さが影響するため、干渉色から透明膜厚さに関する情報が得られる。これが光干渉法の原理である。 The light transmitted through the transparent film is reflected by the reflective sliding material, passes through the transparent film and the transparent sliding material again, and returns to the light source direction. Here, the light reflected by the transparent sliding material-transparent film interface is referred to as “front light”, and the light reflected by the reflective sliding material is referred to as “back light”. The surface wave and the back surface wave cause optical interference because of the optical path difference. When the surface of the reflective sliding material is observed from the transparent sliding material side through the transparent film with a photodetector (camera or the like), optical interference is observed. Since the light interference color (wavelength and luminance) is affected by the optical path difference, that is, the transparent film thickness, information on the transparent film thickness can be obtained from the interference color. This is the principle of optical interferometry.
<従来技術の課題>
従来技術の課題は、光干渉法で得た干渉色から膜厚への変換方法である。色と膜厚の較正を事前に実験的に作成しなくてはならないが、それが非常に煩雑である。
<Prior art issues>
The problem of the prior art is a method for converting the interference color obtained by the optical interferometry to the film thickness. Color and film thickness calibration must be experimentally created in advance, which is very cumbersome.
また、事前に膜厚が既知の透明膜試料を用いて実験的に作成した色相−膜厚の較正表を用いて、色相分布を膜厚分布に変換する。上記非特許文献1に記載されているように、色相は膜厚に対して周期関数であり、膜厚増加に対する干渉色の色相は干渉の次数と同じ約250nm周期で同じ色相が現れ(周期250nmの周期関数である)、その周期が約250nmであるため、膜厚の測定範囲の大きさは250nmに限定され、膜厚測定範囲が狭い。 Further, the hue distribution is converted into the film thickness distribution using a hue-film thickness calibration table experimentally created using a transparent film sample whose film thickness is known in advance. As described in Non-Patent Document 1, the hue is a periodic function with respect to the film thickness, and the hue of the interference color with respect to the increase in the film thickness appears in the same hue with a period of about 250 nm as the order of interference (period 250 nm). Since the period is about 250 nm, the size of the film thickness measurement range is limited to 250 nm, and the film thickness measurement range is narrow.
<本発明の実施の形態の概略>
本発明の実施の形態の、摺動面間の透明膜の厚さ分布計測機能を備えた膜厚計測システムは、従来技術の課題を解決すべく「干渉色から透明膜厚さへ変換に用いる較正」を、煩雑な実験による事前作成を要せずに作成することを特徴とする。具体的には、光干渉を記述する光学の数式と計測結果から作成する。このとき、作成した較正は表ではなく数式となる。
<Outline of Embodiment of the Present Invention>
The film thickness measurement system having the function of measuring the thickness distribution of the transparent film between the sliding surfaces according to the embodiment of the present invention is used to convert the interference color to the transparent film thickness in order to solve the problems of the prior art. It is characterized in that the “calibration” is created without the need for pre-creation by a complicated experiment. Specifically, it is created from optical formulas describing optical interference and measurement results. At this time, the created calibration is not a table but a mathematical expression.
この較正数式の作成方法の概略を述べる。まず、単一の波長の光(以下,単色光)において光干渉における輝度と膜厚(光路差)の関係は数式で記述することができる。この数式には測定環境由来の未知変数(照射光の波長、透明膜の光学特性,反射摺動材の色など)が4つ含まれており、較正として用いるにはこれらの未知変数を導出する必要がある。本発明の実施の形態の特徴は、これらの未知変数を計測結果(干渉色分布)から導出することである。このとき、未知変数は干渉色分布内で一定という仮定、すなわち「干渉色分布は各波長での干渉による輝度の強め合い・弱め合いのみに寄る」という仮定をおく。すると未知変数は計測点に依らなくなるので、計測点を複数選択して十分な数の数式を作成すると、連立方程式の解決もしくは誤差を最小化する最適化手法により数式中の未知変数と膜厚を決定できる。 An outline of a method for creating the calibration formula will be described. First, the relationship between the luminance and the film thickness (optical path difference) in light interference in light of a single wavelength (hereinafter referred to as monochromatic light) can be described by a mathematical expression. This formula includes four unknown variables derived from the measurement environment (irradiation light wavelength, transparent film optical properties, reflective sliding material color, etc.), and these unknown variables are derived for use as calibration. There is a need. The feature of the embodiment of the present invention is that these unknown variables are derived from the measurement result (interference color distribution). At this time, an assumption is made that the unknown variable is constant in the interference color distribution, that is, the “interference color distribution depends only on the intensity strengthening / weakening due to interference at each wavelength”. Then, the unknown variable does not depend on the measurement point, so if you select multiple measurement points and create a sufficient number of equations, you can solve the simultaneous equations or optimize the unknown variable and film thickness in the equation by minimizing the error. Can be determined.
さらに先の数式は単色光における輝度と膜厚を記述したものであるため、光検出器は光干渉後の光を単色光と見なせる程度の分解能で分光して、各波長の輝度を独立して計測する必要がある。これには光検出器が分光器を備える、照射光を単色光から構成する等の方法があるが、本実施の形態では後者を採用する。これは、現在の分光器ではカメラ画像のような2次元空間の1点ごとの分光スペクトルを得られるものは存在しなかったためである。そのため、従来技術との相違点として,照射光をブロードなスペクトルの白色光ではなく波長が既知の2つ以上の単色光から構成している。また光検出器は各単色光の輝度を独立して計測する。さらに、未知変数を導出するには計測点1点において2つ以上の波長について数式が必要であるため、照射光は2つ以上の単色光から構成する。 Furthermore, since the previous equation describes the brightness and film thickness of monochromatic light, the photodetector will split the light after optical interference with a resolution that can be regarded as monochromatic light, and the luminance of each wavelength will be independently determined. It is necessary to measure. This includes a method in which the photodetector includes a spectroscope, and the irradiation light is composed of monochromatic light, but the latter is adopted in this embodiment. This is because there is no current spectroscope capable of obtaining a spectral spectrum for each point in a two-dimensional space such as a camera image. Therefore, the difference from the prior art is that the irradiation light is not white light having a broad spectrum but two or more monochromatic lights having known wavelengths. The photodetector measures the brightness of each monochromatic light independently. Furthermore, since an equation is required for two or more wavelengths at one measurement point in order to derive an unknown variable, the irradiation light is composed of two or more monochromatic lights.
本発明の実施の形態の基本構成を図2に示す。従来の光干渉法の構成に加えて「照射光に含まれる各波長の輝度を独立して計測する光学系」および「干渉色を膜厚へ変換する較正を計測結果から生成するアルゴリズムを備えた演算装置」が必要となる。 The basic configuration of the embodiment of the present invention is shown in FIG. In addition to the configuration of the conventional optical interferometry, it is equipped with an “optical system that independently measures the brightness of each wavelength contained in the irradiating light” and an algorithm that generates a calibration that converts the interference color into a film thickness from the measurement results. An “arithmetic unit” is required.
<干渉色を膜厚へ変換する較正を生成する原理>
干渉色の輝度値から膜厚への較正数式の作成は、以下の2ステップで行われる。
<Principle of generating calibration to convert interference color to film thickness>
The creation of the calibration formula from the luminance value of the interference color to the film thickness is performed in the following two steps.
第1ステップでは、干渉色分布において複数計測点を選択し、干渉色理論式と計測値のフィッティングにより未知変数と選択した計測点の膜厚を導出する。第2ステップでは、膜厚候補値の算出と合致法による真値決定を行う。 In the first step, a plurality of measurement points are selected in the interference color distribution, and the unknown variable and the film thickness of the selected measurement point are derived by fitting the interference color theoretical formula and the measurement value. In the second step, the film thickness candidate value is calculated and the true value is determined by the matching method.
<干渉色理論式と測定値のフィッティングによる未知変数導出>
較正を計測結果から自動的に生成するためには、本計測が行われる環境(照明、透明膜の光学特性、反射摺動材の色など)に依存する未知変数を計測結果から導出する必要がある。具体的には、各波長において、表面波の強度、透明膜による減衰が生じない場合の裏面波の強度、透明膜の減衰係数、及び透明膜の屈折率からなる4つの未知変数を導出する必要がある。
<Deriving unknown variables by fitting interference color theory and measured values>
In order to automatically generate calibration from the measurement results, it is necessary to derive unknown variables from the measurement results that depend on the environment in which this measurement is performed (lighting, optical properties of the transparent film, color of the reflective sliding material, etc.). is there. Specifically, at each wavelength, it is necessary to derive four unknown variables including the intensity of the surface wave, the intensity of the back surface wave when attenuation by the transparent film does not occur, the attenuation coefficient of the transparent film, and the refractive index of the transparent film. There is.
本干渉色解析の特徴は、1点での計測結果からこれらを導出するのではなく、これらが干渉色分布内において一定であると仮定して、複数点での計測結果から導出することである。 The feature of this interference color analysis is not to derive these from the measurement results at one point but to derive them from the measurement results at a plurality of points on the assumption that they are constant in the interference color distribution. .
<干渉色理論式>
m個の単色光から構成される照射光を用いて、画像内のp個の測定点(画像のピクセル数に相当する。一般的なカメラを用いた場合には数百万〜数千万のピクセルである)の透明膜厚さを測定する場合を考える。任意の測定点に割り当てた番号をi(i=1〜p)、単色光に割り当てた番号をj(j=1〜m)とすると、測定点iにおいて測定される波長jの干渉後の輝度I(i,j)と、測定点iにおける透明膜厚さt(i)の関係は式(1)で表される。以下、式(1)を“干渉色理論式”と記す。
<Interference color theory>
Using irradiation light composed of m monochromatic lights, p measurement points in the image (corresponding to the number of pixels in the image. When using a general camera, millions to tens of millions Consider the case of measuring the transparent film thickness (which is a pixel). If the number assigned to an arbitrary measurement point is i (i = 1 to p) and the number assigned to monochromatic light is j (j = 1 to m), the luminance after interference of the wavelength j measured at the measurement point i The relationship between I (i, j) and the transparent film thickness t (i) at the measurement point i is expressed by Expression (1). Hereinafter, the expression (1) is referred to as “interference color theoretical expression”.
(1)
(1)
ただし、I1(j)はj番目の単色光の表面光強度、I2(j)はj番目の単色光の透明膜による吸光が生じない場合の裏面光強度、α(j)は透明膜のj番目の単色光に対する吸光係数、n(j)は透明膜のj番目の単色光に対する屈折率、λ(j)は、予め求められたj番目の単色光の波長である。 Where I 1 (j) is the surface light intensity of the j-th monochromatic light, I 2 (j) is the back-surface light intensity when no absorption of the j-th monochromatic light by the transparent film occurs, and α (j) is the transparent film The extinction coefficient for the j-th monochromatic light, n (j) is the refractive index of the transparent film for the j-th monochromatic light, and λ (j) is the wavelength of the j-th monochromatic light determined in advance.
干渉色理論式をI1=I2=1/4、α=0、n=1、λ=470nm,560nm,600nmの条件でプロットした結果を図3に示す。このように、未知変数が導出できれば色(各単色光の輝度値)と膜厚の較正曲線を得ることが出来る。 FIG. 3 shows the result of plotting the theoretical equation of interference color under the conditions of I 1 = I 2 = 1/4, α = 0, n = 1, λ = 470 nm, 560 nm, and 600 nm. Thus, if an unknown variable can be derived, a calibration curve of color (luminance value of each monochromatic light) and film thickness can be obtained.
<干渉色理論式の導出>
干渉色理論式は光学の公式の組み合わせから導出されるものである。まずは、空間の1点における1つの波長の光による干渉について考える。今回の計測のように2つの光路差を持つ光が干渉に対して支配的になる場合は、干渉光の輝度は式(2)で表される(非特許文献3(ヘクト光学II −波動工学- 第4版,丸善,P.157(2002))を参照)。
<Derivation of interference color theory>
The interference color theory formula is derived from a combination of optical formulas. First, consider interference due to light of one wavelength at one point in space. When light having two optical path differences becomes dominant with respect to interference as in this measurement, the brightness of the interference light is expressed by Equation (2) (Non-patent Document 3 (Hect Optics II-Wave Engineering) -See 4th edition, Maruzen, P.157 (2002)).
(2)
(2)
ここで、I1、I2はそれぞれ表面波、裏面波の輝度であり、δは2つの波の位相差[rad.]である。 Here, I 1 and I 2 are the luminances of the surface wave and the back wave, respectively, and δ is the phase difference [rad.] Of the two waves.
2つの波の位相差[rad.]は、光路差[m]を波長[m]で割り2πを掛けたものである。本測定系の場合、光路差は透明膜の光学膜厚の2倍であるから、透明膜の物理膜厚をt、透明膜の屈折率をnとすると、δは以下の式(3)で表される。 The phase difference [rad.] Of the two waves is obtained by dividing the optical path difference [m] by the wavelength [m] and multiplying by 2π. In this measurement system, since the optical path difference is twice the optical film thickness of the transparent film, assuming that the physical film thickness of the transparent film is t and the refractive index of the transparent film is n, δ is expressed by the following equation (3): expressed.
(3)
(3)
式(3)を式(2)に代入すると、式(4)が得られる. Substituting equation (3) into equation (2) yields equation (4).
(4)
(4)
次に、透明膜による干渉光の吸光(輝度減衰)を考慮する。光の減衰は式(5)で表される(非特許文献4(ヘクト光学I −基礎と幾何工学- 第4版,丸善,P.197(2002))を参照)。 Next, the absorption (brightness attenuation) of interference light by the transparent film is considered. The attenuation of light is expressed by Equation (5) (see Non-Patent Document 4 (Hectonics I-Fundamentals and Geometric Engineering-4th Edition, Maruzen, P.197 (2002))).
(5)
(5)
ここで、αは吸光係数、Lは光が透明膜中を通る距離(透過距離)である。式(5)において、透明膜を透過した光はI2であり、その透過距離は物理膜厚の2倍であるから、I2をI2e-α*2tとすればよい。すると式(6)が導出される. Here, α is an extinction coefficient, and L is a distance (transmission distance) through which light passes through the transparent film. In Expression (5), the light transmitted through the transparent film is I 2 , and the transmission distance is twice the physical film thickness, so I 2 may be I 2 e −α * 2t . Then, equation (6) is derived.
(6)
(6)
次に各未知変数が計測点iと波長jのいずれの関数であるかについて述べる。前述したように、本解析手法の特徴として「表面波の強度I1」、「透明膜による減衰が生じない場合の裏面波の強度I2」、「透明膜の減衰係数α」、「透明膜の屈折率n」は面内で一定と仮定している.これは、摺動材料の色ムラがある場合を除き、多くの摺動面において実用上問題ない範囲で成り立つ仮定である。また色ムラがある場合においても、未知変数を求めるために使用する計測点を同一色の中でのみ設定し膜厚分布も同一色の中であれば解析値に問題なく、色ムラがある場合においても本計測手法は有効性は損なわれるものではない。 Next, it will be described which function of each unknown variable is measurement point i or wavelength j. As described above, the characteristics of this analysis method are “surface wave intensity I 1 ”, “back surface wave intensity I 2 when attenuation by the transparent film does not occur”, “transparent film attenuation coefficient α”, “transparent film” The refractive index n of is assumed to be constant in the plane. This is an assumption that holds within a range where there is no practical problem on many sliding surfaces except when there is color unevenness of the sliding material. Even if there is color unevenness, if the measurement points used to determine unknown variables are set only in the same color and the film thickness distribution is also in the same color, there is no problem in the analysis value, and there is color unevenness However, the effectiveness of this measurement method is not impaired.
この仮定より、式(6)においてI1,I2,α,nは計測点iには依存せず波長jに依存するため、jのみの関数となる。一方、膜厚tは波長jに依存せず計測点iに依存するため、iのみの関数となる。計測される干渉輝度はi, jの両方に依存する。これらの考えを式(6)に導入すると、干渉色理論式を得ることが出来る。 From this assumption, in Equation (6), I 1 , I 2 , α, and n do not depend on the measurement point i, but depend on the wavelength j, and thus are functions of only j. On the other hand, since the film thickness t does not depend on the wavelength j but depends on the measurement point i, it is a function of only i. The measured interference brightness depends on both i and j. When these ideas are introduced into the equation (6), an interference color theoretical equation can be obtained.
<未知変数を導出可能な計測点数の条件>
未知変数の数をX(X=1〜4である。上記ケースでは未知変数の数は4だが実験的に未知変数を求めると数は減るためXとした)とする。計測点数をk、波長数をmとすると、未知変数の数はXm + k個となる。1点からm個の輝度値が得られるため、必要条件はX×m + k ≦ m×kとなり、以下の式(8)を満たす測定点数が必要であることがわかる。
<Conditions for the number of measurement points from which unknown variables can be derived>
The number of unknown variables is assumed to be X (X = 1 to 4. In the above case, the number of unknown variables is 4, but if the number of unknown variables is found experimentally, the number decreases, and X is assumed). If the number of measurement points is k and the number of wavelengths is m, the number of unknown variables is Xm + k. Since m luminance values are obtained from one point, the necessary condition is X × m + k ≦ m × k, and it is understood that the number of measurement points satisfying the following equation (8) is necessary.
(8)
(8)
本実施の形態では、測定点に依存しない未知変数X=4、波長数m=3であるから、6点あれば求まることになる。もちろんこれ以上の計測点がある方がより精度高く未知変数を求めることができる。 In the present embodiment, since the unknown variable X = 4 and the number of wavelengths m = 3 that do not depend on the measurement point, 6 points can be obtained. Of course, unknown variables can be obtained with higher accuracy when there are more measurement points.
また、波長数m=1だと未知変数の数Xに関わらず、計測点数kを増やしても条件を満たさないことがわかる。よって、本計測手法を用いる上では波長数2以上が必須となる。 It can also be seen that if the number of wavelengths m = 1, the condition is not satisfied even if the number of measurement points k is increased, regardless of the number X of unknown variables. Therefore, two or more wavelengths are essential for using this measurement method.
<最小二乗法によるフィッティングを用いた計測値と干渉色理論式の誤差を最小にする未知変数の導出>
式(8)を満たす数の計測点を選択した後は、各計測点において干渉色理論式に則って計測輝度値と4つの未知変数および膜厚の関係式を作成する。それらの関係式において計測値と干渉色理論式の誤差の二乗和を最も小さくするように(最小二乗法)フィッティングを行うことで、4つの未知変数と各計測点での膜厚を同時に導出する。最小二乗法を用いた最適化を行う場合、導出したい最適値は大域最小値(global minimum)であるが、初期値の設定によっては局所最小値(local minimum)を選んでしまう。そのため、解析精度を向上すべく、未知変数の導出を行う際には選択した各計測点に対して膜厚の真値に近い初期値を入力する。これらの初期値は摺動面の油膜厚さ分布や周辺の色情報、図3で示したカラーチャート(計測環境が変化しても膜厚増加に伴う色変化の傾向は大きく変化しない)などを考慮すると、おおよそ真値に近い値を入力することができる。経験的には、初期値が真値から±100nm程度異なっていても真値に到達することがわかっており、初期値の設定はそこまでの厳密さを要するものではない。また解析精度を向上させるには膜厚測定範囲を適切に設定する、すなわち必要以上に広く設定しないことも重要である。
<Derivation of unknown variable that minimizes error between measured value and interference color theory using least squares fitting>
After selecting the number of measurement points satisfying the equation (8), a relational expression of the measurement luminance value, the four unknown variables, and the film thickness is created at each measurement point according to the interference color theory equation. By performing fitting so that the square sum of the error between the measured value and the interference color theory formula is minimized in these relational expressions (the least squares method), four unknown variables and the film thickness at each measurement point are derived simultaneously. . When optimization using the least square method is performed, the optimum value to be derived is the global minimum, but the local minimum is selected depending on the initial value setting. Therefore, in order to improve the analysis accuracy, when an unknown variable is derived, an initial value close to the true value of the film thickness is input for each selected measurement point. These initial values include the oil film thickness distribution on the sliding surface and the surrounding color information, and the color chart shown in Fig. 3 (the trend of color change with increasing film thickness does not change significantly even if the measurement environment changes). Considering this, it is possible to input a value approximately close to the true value. Empirically, it has been found that even if the initial value differs from the true value by about ± 100 nm, it reaches the true value, and the setting of the initial value does not require such strictness. In order to improve the analysis accuracy, it is also important to set the film thickness measurement range appropriately, that is, not to set it wider than necessary.
<膜厚候補値の算出と合致法による真値決定(第2ステップ)>
第1ステップの手法は、未知変数の導出に用いる計測点が増えると計算負荷が増すため、画像の全領域(測定点数=カメラ画素数のため,数百万〜数千万)を第1ステップのみで解析するのは不適切である。よって、第1ステップにおいて未知変数の導出に用いる計測点数は数十個程度に留め、第2ステップでは第1ステップで導出した未知変数を用いて、残りの計測点に対し、各波長の輝度から膜厚への変換を行う。具体的には、導出した未知変数と各点・各波長の輝度値から式(1)における膜厚の候補値を各計測点について求め、それを波長間の合致法を用いて真値を決定する手法である。第2ステップでは、第1ステップのように複数計測点の膜厚値を同時に決定するのではなく、各計測点の膜厚値を1点ずつ決定する。
<Calculation of film thickness candidate value and determination of true value by matching method (second step)>
In the first step method, the calculation load increases as the number of measurement points used to derive unknown variables increases. Therefore, the entire area of the image (several millions to tens of millions because the number of measurement points = the number of camera pixels) is the first step. It is unsuitable to analyze only with this. Therefore, the number of measurement points used for derivation of unknown variables in the first step is limited to several tens, and in the second step, the unknown variables derived in the first step are used to calculate the remaining measurement points from the brightness of each wavelength. Conversion to film thickness is performed. Specifically, from the derived unknown variable and the brightness value of each point / wavelength, the film thickness candidate value in Equation (1) is obtained for each measurement point, and the true value is determined using the matching method between wavelengths. It is a technique to do. In the second step, the film thickness values at a plurality of measurement points are not determined simultaneously as in the first step, but the film thickness values at each measurement point are determined one by one.
<膜厚候補値の算出>
ここでは第1ステップによりI1(j),I2(j),α(j),n(j)は既知になっているため、式(1)を用いると膜厚tと輝度Iの関係が既知になる。図4に透明膜による減衰が生じない(α=0)場合の膜厚tと輝度Iの関係を示し、図5に、透明膜による減衰が生じる(α>0)場合の膜厚tと輝度Iの関係を示す。図4、図5中では強度が0.4の場合の波長470nmの膜厚候補値を示してある。減衰が生じない場合には膜厚候補値は式(1)にα=0を代入し変形した式(7)を用いて解析的に求めることができる。一方、減衰が生じる場合には膜厚候補値を解析的に求める式は見つかっておらず、数値計算によって求める必要がある。もちろん解析的に求める式が見つかればそれを用いても良い。
<Calculation of film thickness candidate value>
Here, since I 1 (j), I 2 (j), α (j), and n (j) are already known by the first step, the relationship between film thickness t and luminance I is obtained using equation (1). Becomes known. FIG. 4 shows the relationship between film thickness t and luminance I when attenuation by the transparent film does not occur (α = 0), and FIG. 5 shows film thickness t and luminance when attenuation by the transparent film occurs (α> 0). The relationship of I is shown. 4 and 5 show the film thickness candidate values at a wavelength of 470 nm when the intensity is 0.4. In the case where no attenuation occurs, the film thickness candidate value can be analytically obtained by substituting α = 0 into equation (1) and modifying equation (7). On the other hand, when attenuation occurs, an equation for analytically obtaining a film thickness candidate value has not been found, and must be obtained by numerical calculation. Of course, if an analytically obtained expression is found, it may be used.
(7)
(7)
<各波長間の位相合致法による膜厚推定>
上記のように算出された膜厚候補値から、合致法(非特許文献5(尾藤,産総研計量標準報告, Vol.4, No.1 (2005))を参照)を用いて真値を決定する。合致法とは、図6で示すように、3波長の膜厚候補値の差が最も少ない値を膜厚の真値として選ぶ手法である。合致法においても、周期的に3波長の候補値が近い膜厚が出現するため、解析精度を向上させるには膜厚測定範囲を適切に設定する、すなわち必要以上に広く設定しないことが重要である。また今回は3つの単色光を用いているが、波長数が増えると波長間の候補値が近い膜厚が出現する周期(間隔)が広がるため、解析精度は向上する。
<Estimation of film thickness by phase matching method between wavelengths>
The true value is determined from the film thickness candidate values calculated as described above using the matching method (see Non-Patent Document 5 (Ato, AIST Metrology Standards Report, Vol. 4, No. 1 (2005))). To do. As shown in FIG. 6, the matching method is a method of selecting a value having the smallest difference in film thickness candidate values of three wavelengths as the true value of the film thickness. Even in the coincidence method, since film thicknesses with close candidate values of three wavelengths appear periodically, it is important to set the film thickness measurement range appropriately, that is, not to set it wider than necessary in order to improve the analysis accuracy. is there. In addition, three monochromatic lights are used this time. However, as the number of wavelengths increases, the period (interval) in which the film thicknesses with similar candidate values between wavelengths appear increases, so the analysis accuracy improves.
<システム構成>
本発明の実施形態に係る膜厚計測システム10について、図7〜図10に基づいて説明する。
<System configuration>
A film thickness measurement system 10 according to an embodiment of the present invention will be described with reference to FIGS.
図7に示すように膜厚計測システム10は、光学系20、摺動系40、及び演算装置60を備えている。 As shown in FIG. 7, the film thickness measurement system 10 includes an optical system 20, a sliding system 40, and a calculation device 60.
<光学系>
光学系20は、白色光源22、ライトガイド24、3波長バンドパスフィルタ26、ハーフミラー28、レンズ30、及びカメラ32を備えている。
<Optical system>
The optical system 20 includes a white light source 22, a light guide 24, a three-wavelength band pass filter 26, a half mirror 28, a lens 30, and a camera 32.
白色光源22から照射された白色光が、ライトガイド24に入射され、ライトガイド24の途中に設けられた、3波長を透過する3波長バンドパスフィルタ26を透過した、3波長の単色光から構成される照射光が、ハーフミラー28で反射して、摺動系40へ入射される。 The white light emitted from the white light source 22 is incident on the light guide 24 and is composed of monochromatic light of three wavelengths transmitted through a three-wavelength bandpass filter 26 that is provided in the middle of the light guide 24 and transmits three wavelengths. The irradiated light is reflected by the half mirror 28 and is incident on the sliding system 40.
摺動系40で反射された光が、ハーフミラー28を透過して、カメラ32に入射される。 The light reflected by the sliding system 40 passes through the half mirror 28 and enters the camera 32.
カメラ32は、摺動系40で生じた光干渉における、3波長の光の各々の輝度を計測する。 The camera 32 measures the luminance of each of the three wavelengths of light in the optical interference generated in the sliding system 40.
本発明の実施の形態と従来技術と比較した場合の大きな相違点は、照射光が波長が既知の単色光から構成されることである。本実施の形態では、照射光を構成する単色光として波長が470nm,560nm,600nmの3波長を選択する。これらは一般的なカラーカメラのRGBの分光感度を考慮し、一般的なカラーカメラを光検出器として用いるためである。これらの単色光から構成される照射光はブロードなスペクトルを持つ白色光(キセノンフラッシュランプ)を、3波長バンドパスフィルタ26を用いて特定の波長のみ透過させることにより実現する。図8に、3波長バンドパスフィルタ26の透過スペクトルの一例を示す。各単色光の半値全幅(FWHM)は約10nmである。本計測法を用いるうえでは半値全幅は少ないほどよいが、半値全幅10nmの単色光を用いた場合でも妥当な結果が得られている。なお、本実施の形態では照射光を単色光のみから構成するためにバンドパスフィルタを用いたが、単色光を発する光源、例えばLEDやレーザーを組み合わせることによって実現しても良い。 The major difference between the embodiment of the present invention and the prior art is that the irradiated light is composed of monochromatic light having a known wavelength. In the present embodiment, three wavelengths having wavelengths of 470 nm, 560 nm, and 600 nm are selected as monochromatic light constituting the irradiation light. This is because a general color camera is used as a photodetector in consideration of the RGB spectral sensitivity of a general color camera. Irradiation light composed of these monochromatic lights is realized by transmitting white light (xenon flash lamp) having a broad spectrum only at a specific wavelength using a three-wavelength bandpass filter 26. FIG. 8 shows an example of the transmission spectrum of the three-wavelength bandpass filter 26. The full width at half maximum (FWHM) of each monochromatic light is about 10 nm. When using this measurement method, the smaller the full width at half maximum, the better. However, reasonable results are obtained even when monochromatic light with a full width at half maximum of 10 nm is used. In this embodiment, the bandpass filter is used to configure the irradiation light only from the monochromatic light. However, it may be realized by combining a light source that emits monochromatic light, for example, an LED or a laser.
本実施の形態では、照射する光の波長にこれらの可視光を用いた場合を例に説明するが、本計測原理は可視光に限定されるものではなく、任意の波長を持つ光(電磁波)に対しても本計測原理は成立する。ただし、200nm以下の光は真空紫外光と呼ばれ大気による吸収が生じるため、扱いが難しい。また4000nm以上の光(中赤外〜遠赤外線、電波)は輻射により室温の物体からでも放射されているため、干渉光と輻射光の区別が困難となり、解析する上で障害がある。よって、単色光を構成する波長範囲としては200nm〜4000nmが望ましい。 In this embodiment, the case where these visible lights are used as the wavelength of light to be irradiated will be described as an example, but this measurement principle is not limited to visible lights, and light having an arbitrary wavelength (electromagnetic wave) However, this measurement principle is valid. However, light below 200 nm is called vacuum ultraviolet light and is absorbed by the atmosphere, so it is difficult to handle. In addition, light (middle infrared to far infrared, radio waves) of 4000 nm or more is radiated from an object at room temperature due to radiation, so that it is difficult to distinguish between interference light and radiation light, and there are obstacles to analysis. Therefore, the wavelength range constituting monochromatic light is preferably 200 nm to 4000 nm.
本実施の形態では単色光の数は3を用いているが、後述するように単色光の数は2以上であれば本計測原理は成立する In this embodiment, the number of monochromatic lights is 3, but as will be described later, this measurement principle is valid if the number of monochromatic lights is 2 or more.
また、本実施の形態では、カメラ32として、3CCDデジタルカラーカメラ(JAI社製 AT200-CL)を用いる。これは分光感度の重複、すなわち470nm(Blue)や600nm(Red)の光が560nm(Green)の受光素子に輝度としてカウントされること、を避けるためである。なお、この分光感度の重複は補正可能であり、補正すれば分光感度の重複があるカメラ(1CCDカメラなど)も用いることができる。 In the present embodiment, a 3CCD digital color camera (AT200-CL manufactured by JAI) is used as the camera 32. This is to avoid overlapping of spectral sensitivity, that is, light of 470 nm (Blue) or 600 nm (Red) is counted as luminance by the light receiving element of 560 nm (Green). Note that this overlap of spectral sensitivities can be corrected, and if corrected, cameras with overlapping spectral sensitivities (such as a 1CCD camera) can also be used.
撮像はフレームグラバーを介して演算装置60に取り込んでいる。演算装置60に取り込んだ画像はHSVに変換せず、RGB輝度分布のまま、すなわち波長470nm,560nm,600nmの単色光の輝度分布として解析に供試する。撮像のRGBのビット深度は8ビット(256階調)である。 Imaging is taken into the arithmetic unit 60 via a frame grabber. The image taken in the arithmetic unit 60 is not converted to HSV, but is used for analysis as an RGB luminance distribution, that is, as a luminance distribution of monochromatic light having wavelengths of 470 nm, 560 nm, and 600 nm. The RGB bit depth of imaging is 8 bits (256 gradations).
本実施の形態では光検出器として2次元光検出器であるカメラを用いた場合を例に説明するが、本計測の原理は2次元検出器を用いた場合に限定されるものではない。後述するように、本計測原理を適用するには条件として同一面内で複数計測点のデータが必要であるが、1次元検出器を用いて時間方向に複数点測定しても条件を満たすためである。 In this embodiment, a case where a camera which is a two-dimensional photodetector is used as an example of the photodetector will be described as an example. However, the principle of this measurement is not limited to the case where a two-dimensional detector is used. As will be described later, in order to apply this measurement principle, data of multiple measurement points is required as a condition in the same plane, but even if multiple points are measured in the time direction using a one-dimensional detector, the condition is satisfied. It is.
<摺動系>
摺動系40は、透明摺動材42、部分反射膜44、透明保護膜45、液体膜46、反射摺動材48、摺動試験機50を備えている。
<Sliding system>
The sliding system 40 includes a transparent sliding material 42, a partially reflective film 44, a transparent protective film 45, a liquid film 46, a reflective sliding material 48, and a sliding test machine 50.
液体膜46は、透明摺動材42と反射摺動材48との間に存在し、透明摺動材42の光学系20側と反対側に設けられた透明保護膜45と液体膜46とは接触しており、反射摺動材48と液体膜46とは接触している。 The liquid film 46 exists between the transparent sliding material 42 and the reflective sliding material 48, and the transparent protective film 45 and the liquid film 46 provided on the opposite side of the transparent sliding material 42 from the optical system 20 side are the liquid film 46. The reflective sliding member 48 and the liquid film 46 are in contact with each other.
透明摺動材42及び液体膜46は、3波長の光を透過し、反射摺動材48は3波長の光を反射する。光学系20からの入射された照射光を、透明摺動材42と液体膜46とを透過させて反射摺動材48へ照射して光干渉を生じさせる。 The transparent sliding material 42 and the liquid film 46 transmit light of three wavelengths, and the reflective sliding material 48 reflects light of three wavelengths. The incident irradiation light from the optical system 20 is transmitted through the transparent sliding material 42 and the liquid film 46 and irradiated to the reflective sliding material 48 to cause optical interference.
摺動試験機50は、透明摺動材42を回転させ、透明摺動材42と反射摺動材48とは荷重を受けながら相対運動する。 The sliding tester 50 rotates the transparent sliding member 42, and the transparent sliding member 42 and the reflective sliding member 48 move relative to each other while receiving a load.
本実施の形態では、液体膜46として潤滑油の膜を用いる。潤滑油の種類は炭化水素系の基油(SK Lubricants(R)社製 Yubase4)である。無色透明であり光の吸収は生じない。なお、本実施の形態では、透明膜として液体膜46を用いたが、上述した透明膜の定義に当てはまるものであれば本計測原理は適用可能であり、液体膜に限定されるものではない。 In the present embodiment, a lubricating oil film is used as the liquid film 46. The type of lubricating oil is a hydrocarbon base oil (Yubase4 manufactured by SK Lubricants (R)). It is colorless and transparent and does not absorb light. In the present embodiment, the liquid film 46 is used as the transparent film. However, the present measurement principle can be applied as long as it meets the definition of the transparent film described above, and is not limited to the liquid film.
また、本実施の形態では、透明摺動材42として、可視光に対して透明かつ高強度・高耐摩耗な材質である単結晶サファイアを用いる。本実施の形態では可視光の光を用いているため、サファイアや石英ガラスなど可視光に対する透明体に限定されるが、用いる単色光の波長域が変われば、用いることのできる材料も変化し、本測定手法は可視光に対して透明な材料に限定されるものではない。例えば単色光の波長として赤外光域を用いた場合、シリコンやゲルマニウムを透明摺動材42として用い、光検出器として赤外線カメラを用いることでも本原理は実現できる。本実施の形態では、サファイア−潤滑油間の反射が十分ではなかったため、サファイアである透明摺動材42の表面にクロムの部分反射膜44をコートした。さらに、部分反射膜44の上にシリカ(SiO2)の透明保護膜45を150nm(物理膜厚)コートした。これは摺動中にクロムの部分反射膜44が剥がれるのを防ぐとともに、油膜厚さをプラス方向にオフセット(底上げ)することが目的である。シリカの透明保護膜45は可視光に対して透明であるため、計測される膜厚値は油膜厚に加えてシリカ膜厚が加えられた値となるからである。オフセットさせる狙いを以下に示す。 In the present embodiment, single crystal sapphire, which is a material that is transparent to visible light and has high strength and high wear resistance, is used as the transparent sliding member 42. Since visible light is used in this embodiment, it is limited to a transparent body for visible light such as sapphire or quartz glass, but if the wavelength range of monochromatic light to be used is changed, the usable material is also changed, This measurement method is not limited to a material transparent to visible light. For example, when the infrared light region is used as the wavelength of the monochromatic light, the present principle can also be realized by using silicon or germanium as the transparent sliding material 42 and using an infrared camera as the photodetector. In this embodiment, since the reflection between the sapphire and the lubricating oil was not sufficient, the surface of the transparent sliding member 42 made of sapphire was coated with a chromium partial reflection film 44. Further, a 150 nm (physical film thickness) coating of a transparent protective film 45 of silica (SiO 2 ) was applied on the partial reflection film 44. The purpose of this is to prevent the partial reflection film 44 of chrome from being peeled off during sliding, and to offset the oil film thickness in the plus direction (to raise the bottom). This is because the transparent protective film 45 of silica is transparent to visible light, and thus the measured film thickness value is a value obtained by adding the silica film thickness in addition to the oil film thickness. The aim of offsetting is shown below.
本実施の形態の計測手法は、輝度と膜厚の較正数式を用いて輝度から膜厚への変換を行う。この輝度の変化は式(1)や3に示すようにコサイン曲線になる。すると曲線のピークやボトムでは膜厚の変化に対する輝度の変化が乏しくなり、解析精度(分解能やノイズに対するロバスト性)が低下する。1つの波長の輝度値がピークやボトムであっても他の波長の輝度値がそれ以外(斜面部)であれば問題にならないが3波長ともピークやボトムにあると解析精度の低下が問題となる。このような領域が図3における0nm近傍や120nm近傍に現れるため、このような領域を避けて測定するためにシリカの透明保護膜45をコートし、油膜厚さを150nm(物理膜厚)オフセットしている。 The measurement method of this embodiment performs conversion from luminance to film thickness using a calibration formula for luminance and film thickness. This change in luminance becomes a cosine curve as shown in equations (1) and 3. Then, the change in luminance with respect to the change in film thickness becomes scarce at the peak and bottom of the curve, and the analysis accuracy (robustness against resolution and noise) decreases. Even if the luminance value of one wavelength is peak or bottom, it does not matter if the luminance value of other wavelengths is other than that (slope part), but if all three wavelengths are at the peak or bottom, the analysis accuracy will be lowered. Become. Since such a region appears in the vicinity of 0 nm or 120 nm in FIG. 3, in order to avoid such a region, a transparent protective film 45 of silica is coated, and the oil film thickness is offset by 150 nm (physical film thickness). ing.
また、本実施の形態では、反射摺動材48として、鏡面研磨した炭素鋼を用いる。なお、光干渉を生み出すことができれば、反射摺動材48の表面粗さや材質は限定されるものではない。 In the present embodiment, mirror-polished carbon steel is used as the reflective sliding member 48. The surface roughness and material of the reflective sliding member 48 are not limited as long as optical interference can be generated.
また、本実施の形態では、摺動試験機50として、図7に示すように、ディスク・オン・ディスク型摺動試験機を用いる。ディスク・オン・ディスク型摺動試験機は、回転する透明摺動材42を所定荷重で反射摺動材48である円板試験片に押し付け、面接触形態における連続すべり条件での摩擦を行う試験機である。摺動面の透明膜厚さ分布と同時に摩擦係数や垂直荷重も計測可能である。 In this embodiment, a disk-on-disk type sliding tester is used as the sliding tester 50 as shown in FIG. The disk-on-disk type sliding tester is a test in which a rotating transparent sliding material 42 is pressed against a disk test piece which is a reflective sliding material 48 with a predetermined load, and friction is performed under a continuous sliding condition in a surface contact mode. Machine. The friction coefficient and vertical load can be measured simultaneously with the transparent film thickness distribution on the sliding surface.
<演算装置>
演算装置60は、CPU、後述する膜厚計測処理ルーチンのプログラムを記憶したROM、データ等を記憶するRAM、及びこれらを接続するバスを含んで構成されている。演算装置60は、カメラ32から入力された画像に基づいて、膜厚を計測し、計測結果を出力部70により出力する。
<Calculation device>
The arithmetic unit 60 includes a CPU, a ROM that stores a program for a film thickness measurement processing routine, which will be described later, a RAM that stores data, and a bus that connects these. The arithmetic device 60 measures the film thickness based on the image input from the camera 32 and outputs the measurement result by the output unit 70.
演算装置60をハードウエアとソフトウエアとに基づいて定まる機能実現手段毎に分割した機能ブロックで説明すると、図9に示すように、画像取得部62、未知変数導出部64、及び膜厚値決定部66を備えている。 When the arithmetic device 60 is described with function blocks divided for each function realizing means determined based on hardware and software, as shown in FIG. 9, an image acquisition unit 62, an unknown variable derivation unit 64, and a film thickness value determination A portion 66 is provided.
画像取得部62は、カメラ32から入力された、光干渉分布を表す画像を取得し、3波長の各々についての各計測点(各画素)の輝度を得る。 The image acquisition unit 62 acquires an image representing the light interference distribution input from the camera 32, and obtains the luminance of each measurement point (each pixel) for each of the three wavelengths.
未知変数導出部64は、画像取得部62によって取得された画像に基づいて、一部の計測点の各々について、3波長の光の各々の輝度と液体膜46の膜厚との関係を表す関係式であって、当該計測点における液体膜46の膜厚、及び面内で同一であると仮定した測定環境由来の未知変数を含む関係式である上記式(1)に対して、最小二乗法などの最適化手法により、一部の計測点の各々における液体膜46の膜厚、及び測定環境由来の未知変数を求める。 Based on the image acquired by the image acquisition unit 62, the unknown variable deriving unit 64 represents a relationship between the luminance of each of the three wavelengths and the film thickness of the liquid film 46 for each of some measurement points. For the above equation (1), which is a relational expression including an unknown variable derived from the measurement environment that is assumed to be the same in the thickness and the thickness of the liquid film 46 at the measurement point, the least square method The thickness of the liquid film 46 at each of some measurement points and an unknown variable derived from the measurement environment are obtained by an optimization method such as the above.
膜厚値決定部66は、画像取得部62によって取得された画像、及び求められた測定環境由来の未知変数に基づいて、残りの計測点の各々について、上記式(7)に従って、3波長に対する、上記式(1)の関係式を満たす当該計測点における液体膜46の膜厚の候補値を求め、3波長に対する当該計測点における液体膜46の膜厚の候補値から、波長間の合致法を用いて当該計測点における液体膜46の膜厚値を決定する。 Based on the image acquired by the image acquisition unit 62 and the obtained unknown variable derived from the measurement environment, the film thickness value determination unit 66 applies the three wavelengths according to the above equation (7). Then, a candidate value of the film thickness of the liquid film 46 at the measurement point that satisfies the relational expression of the above equation (1) is obtained, and a matching method between wavelengths is obtained from the candidate value of the film thickness of the liquid film 46 at the measurement point for the three wavelengths. Is used to determine the film thickness value of the liquid film 46 at the measurement point.
<膜厚計測システムの作用>
次に、本実施の形態に係る膜厚計測システム10の作用を説明する。
<Operation of film thickness measurement system>
Next, the operation of the film thickness measurement system 10 according to the present embodiment will be described.
まず、摺動試験機50により、透明摺動材42が回転して、透明摺動材42と反射摺動材48とが荷重を受けながら相対運動しているときに、白色光源22からの白色光が、3波長バンドパスフィルタ26に入射され、3波長バンドパスフィルタ26を透過した3波長の単色光からなる照射光が、ハーフミラー28で反射して、摺動系40に入射される。3波長の単色光からなる照射光の一部は、部分反射膜44と液体膜46との界面で反射し、3波長の単色光からなる照射光の一部は、透明摺動材42と部分反射膜44との界面で反射して、光干渉が生じているとき、カメラ32によって光干渉分布を撮像し、カメラ32によって撮像する毎に、画像が演算装置60に入力される。 First, when the transparent sliding member 42 is rotated by the sliding tester 50 and the transparent sliding member 42 and the reflective sliding member 48 are moving relative to each other while receiving a load, the white light from the white light source 22 is detected. Light is incident on the three-wavelength band-pass filter 26, and the irradiation light composed of monochromatic light of three wavelengths transmitted through the three-wavelength band-pass filter 26 is reflected by the half mirror 28 and incident on the sliding system 40. A part of the irradiation light composed of monochromatic light of three wavelengths is reflected at the interface between the partial reflection film 44 and the liquid film 46, and a part of the irradiation light composed of monochromatic light of three wavelengths is a part of the transparent sliding material 42. When light interference occurs due to reflection at the interface with the reflective film 44, the optical interference distribution is imaged by the camera 32, and an image is input to the arithmetic device 60 each time the camera 32 captures an image.
そして、入力された画像の各々について、演算装置60によって、図10に示す膜厚計測処理ルーチンが実行される。 Then, a film thickness measurement processing routine shown in FIG. 10 is executed by the arithmetic device 60 for each of the input images.
まず、ステップ100において、カメラ32から入力された処理対象の画像から、各測定点(各画素)における3波長の各々の輝度を取得する。 First, in step 100, the brightness of each of the three wavelengths at each measurement point (each pixel) is acquired from the processing target image input from the camera 32.
そして、ステップ102において、一部の計測点の各々について、3波長の各々に対し、上記ステップ100で取得した当該計測点の輝度を用いた上記式(1)の関係式を用意し、最適化手法により、3波長の各々の単色光の表面光強度I1(j)、3波長の各々の単色光の液体膜46による吸光が生じない場合の裏面光強度I2(j)、液体膜46の3波長の各々の単色光に対する吸光係数α(j)、液体膜46の3波長の各々の単色光に対する屈折率n(j)、一部の計測点の各々の液体膜46の膜厚t(i)を求める。 In step 102, for each of some measurement points, for each of the three wavelengths, the relational expression (1) using the brightness of the measurement point acquired in step 100 is prepared and optimized. By the method, the surface light intensity I 1 (j) of each monochromatic light of the three wavelengths, the back surface light intensity I 2 (j) when the liquid film 46 does not absorb the monochromatic light of each of the three wavelengths, The absorption coefficient α (j) for each monochromatic light of three wavelengths, the refractive index n (j) for each monochromatic light of the three wavelengths of the liquid film 46, and the film thickness t ( i) is determined.
次のステップ104では、残りの計測点から、対象の測定点を選択する。ステップ106では、上記ステップ100で取得した当該計測点の3波長の輝度、上記ステップ102で求めた、3波長の各々の単色光の表面光強度I1(j)、3波長の各々の単色光の液体膜46による吸光が生じない場合の裏面光強度I2(j)、液体膜46の3波長の各々の単色光に対する吸光係数α(j)、液体膜46の3波長の各々の単色光に対する屈折率n(j)を用いた上記式(1)の関係式を満たす、対象の測定点における液体膜46の膜厚の候補値を、3波長の各々に対して上記式(7)に従って算出する。 In the next step 104, a target measurement point is selected from the remaining measurement points. In step 106, the luminance of the three wavelengths of the measurement point acquired in step 100, the surface light intensity I 1 (j) of each of the three wavelengths of monochromatic light obtained in step 102, and the monochromatic light of each of the three wavelengths. Back light intensity I 2 (j) when no light absorption by the liquid film 46 occurs, the light absorption coefficient α (j) for each of the monochromatic light of the three wavelengths of the liquid film 46, and each of the monochromatic light of the three wavelengths of the liquid film 46 A candidate value for the film thickness of the liquid film 46 at the target measurement point that satisfies the relational expression of the above expression (1) using the refractive index n (j) is calculated according to the above expression (7) for each of the three wavelengths. To do.
ステップ108では、上記ステップ106で3波長の各々に対して算出した対象の測定点における液体膜46の膜厚の候補値から、対象の測定点における液体膜46の膜厚値を決定する。 In step 108, the film thickness value of the liquid film 46 at the target measurement point is determined from the candidate value of the film thickness of the liquid film 46 at the target measurement point calculated for each of the three wavelengths in step 106.
ステップ110では、上記ステップ104〜ステップ108の処理を、残りの計測点の全てについて終了したか否かを判定する。残りの計測点のうち、上記ステップ104〜ステップ108の処理を実行していない計測点が存在する場合には、上記ステップ104へ戻り、当該計測点を対象の測定点として選択する。一方、上記ステップ104〜ステップ108の処理を、残りの計測点の全てについて終了した場合には、ステップ112へ進む。 In step 110, it is determined whether or not the processing in steps 104 to 108 has been completed for all remaining measurement points. If there is a measurement point that has not been subjected to the processing of step 104 to step 108 among the remaining measurement points, the process returns to step 104 and the measurement point is selected as the target measurement point. On the other hand, when the processing of step 104 to step 108 is completed for all remaining measurement points, the process proceeds to step 112.
ステップ112では、上記ステップ102で算出した、一部の計測点の各々の液体膜46の膜厚、及び上記ステップ108で決定した、一部の計測点の各々の液体膜46の膜厚を、出力部70により出力して、処理を終了する。 In step 112, the film thickness of each liquid film 46 at some measurement points calculated in step 102 and the film thickness of each liquid film 46 at some measurement points determined in step 108 are as follows. The output is performed by the output unit 70, and the process ends.
<実験例>
<静的条件での透明膜厚さの検定>
本実施の形態における計測手法の有効性を示すには、導出された透明膜厚さの妥当性を示す必要がある。そこで、膜厚が既知の試料を、本実施の形態の計測手法で計測し、それらの膜厚値を比較した。
<Experimental example>
<Verification of transparent film thickness under static conditions>
In order to show the effectiveness of the measurement technique in the present embodiment, it is necessary to show the validity of the derived transparent film thickness. Therefore, samples with known film thicknesses were measured by the measurement method of the present embodiment, and their film thickness values were compared.
<試料と干渉象>
膜厚が既知の透明膜は、深さが既知の凹部に基油を入れることで準備した。透明膜が摺動を受けない静的な測定であれば、透明膜厚さは凹部の深さと同一になるからである。この深さが既知の凹部はシリコンウェーハーをエッチングすることで準備した。図11にシリコンウェーハーの模式図を示す。凹みの面方向の形状は一辺が約700μmの正方形であり、深さ水準は数nmオーダ、数十nmオーダ、数百nmオーダの3水準を用いた。このシリコンウェーハーの凹部に基油を入れて透明摺動材に押し付け、その際の干渉像を撮影した。
<Sample and interference elephant>
A transparent film having a known film thickness was prepared by putting a base oil into a recess having a known depth. This is because the transparent film thickness is the same as the depth of the recess if it is a static measurement in which the transparent film is not slid. A recess having a known depth was prepared by etching a silicon wafer. FIG. 11 shows a schematic diagram of a silicon wafer. The shape in the direction of the surface of the dent was a square with a side of about 700 μm, and three levels of depth levels of several nm, several tens of nm, and several hundreds of nm were used. Base oil was put into the concave portion of the silicon wafer and pressed against the transparent sliding material, and an interference image at that time was taken.
一方、凹みの深さ測定には白色干渉式の3次元形状測定機(Zygo(R)社製 Newview)を用いた。測定は大気中で実施した。 On the other hand, a white interference type three-dimensional shape measuring machine (Newview manufactured by Zygo (R)) was used for measuring the depth of the dent. The measurement was performed in the atmosphere.
図12にシリコンウェーハー凹部(深さ数百nmオーダ)の基油膜による干渉像を示す。なお、図12は撮像から凹部周辺のみを切り出した画像である。 FIG. 12 shows an interference image by a base oil film in a silicon wafer recess (depth several hundred nm order). Note that FIG. 12 is an image obtained by cutting out only the periphery of the recess from the imaging.
<未知変数の導出>
未知変数を導出すべく、凹部を含む撮像全体から19点計測点を選定した。ここで本実験で用いた透明膜は基油であり、可視光域で吸収を持たない(減衰係数≒0)ため、減衰係数α(j)は予めゼロ(α(470nm)=α(560nm)=α(600nm)=0)として解析している。また屈折率も波長依存性は大きくないため、全ての波長における透明膜の屈折率n(j)を1.46(n(470nm) = n(560nm) = n(600nm) = 1.46)とした。よって導出する変数はI1(j)とI2(j)の2変数になる。
<Derivation of unknown variable>
In order to derive unknown variables, 19 measurement points were selected from the entire imaging including the recess. Here, since the transparent film used in this experiment is a base oil and has no absorption in the visible light range (attenuation coefficient ≈ 0), the attenuation coefficient α (j) is zero in advance (α (470nm) = α (560nm) = α (600nm) = 0) Also, since the refractive index is not wavelength-dependent, the refractive index n (j) of the transparent film at all wavelengths was set to 1.46 (n (470 nm) = n (560 nm) = n (600 nm) = 1.46). Therefore, the derived variables are two variables I 1 (j) and I 2 (j).
図13に、上記の実施の形態で説明したアルゴリズムを用いてI1(j)とI2(j)を導出した結果を示す。I1、I2の輝度値は8bit(256階調)における輝度値を意味する。このように複数計測点の輝度値から、実験的な較正を必要とせず、変数を導出することができた。これらの変数を用いて数nmオーダ、数十nmオーダの凹部による基油膜も解析した。 FIG. 13 shows the result of deriving I1 (j) and I2 (j) using the algorithm described in the above embodiment. The luminance values of I 1 and I 2 mean luminance values in 8 bits (256 gradations). In this way, variables could be derived from the luminance values at a plurality of measurement points without the need for experimental calibration. Using these variables, the base oil film with the recesses on the order of several nm and several tens of nm was also analyzed.
<比較結果>
図14に数百nmオーダの凹部による基油膜の膜厚分布および3次元形状測定機で測定した深さ分布の断面を比較した結果を示す。両者は良く一致していることがわかる。また図15に数nmオーダ、数十nmオーダ、数百nmオーダの3水準において、凹部の平均膜厚と平均深さをプロットした結果を示す。これらが同値であれば、図15中に示したY=Xの直線上に並ぶ。図15では、3水準において各プロットはY=Xの直線上に並んでおり、白色干渉式の3次元形状計測機を用いて計測した深さと、本実施の形態の計測法を用いて計測した透明膜厚さは良く一致していた。この結果より、本実施の形態の計測手法から算出された透明膜厚さは妥当であることがわかる。
<Comparison result>
FIG. 14 shows the result of comparing the thickness distribution of the base oil film by the recesses on the order of several hundred nm and the cross section of the depth distribution measured by a three-dimensional shape measuring machine. It turns out that both agree well. FIG. 15 shows the results of plotting the average film thickness and the average depth of the recesses at three levels of several nm order, several tens nm order, and several hundred nm order. If these are the same value, they are arranged on a straight line of Y = X shown in FIG. In FIG. 15, the plots are arranged on a straight line of Y = X at three levels, and measured using the white interference type three-dimensional shape measuring instrument and the measurement method of the present embodiment. The transparent film thickness was in good agreement. From this result, it can be seen that the transparent film thickness calculated from the measurement method of the present embodiment is appropriate.
また従来技術では光学膜厚で250nmの範囲しか解析できなかった。光学膜厚250nmを物理膜厚に換算すると、今回用いた潤滑油(屈折率:1.46)ではおよそ170nmになる。数百nmオーダの凹部を用いた計測ではおよそ230nmの膜厚まで計測できているため、本実施の形態の計測手法では従来技術よりも広い膜厚範囲が解析出来ていることが分かる。 In addition, the conventional technique can only analyze the optical film thickness in the range of 250 nm. When the optical film thickness of 250 nm is converted into a physical film thickness, the lubricating oil (refractive index: 1.46) used this time is approximately 170 nm. In the measurement using a recess of the order of several hundred nm, it is possible to measure a film thickness of about 230 nm. Therefore, it can be seen that the measurement method of this embodiment can analyze a wider film thickness range than the conventional technique.
<摺動時の透明膜厚さ計測>
次に、摺動面に存在する透明膜として一般的な潤滑油膜を用いて膜厚を測定した結果について説明する。
<Measurement of transparent film thickness during sliding>
Next, the result of measuring the film thickness using a general lubricating oil film as the transparent film present on the sliding surface will be described.
<試料>
反射摺動材には鏡面研磨した鋼(炭素鋼)を用いた。形状はΦ5mmの円板とした。ただし、摺動面は完全な平面ではなく、特殊な研磨により非常に大きな曲率(SR1000相当)を持った中高形状(球形状)とした。これは、摺動試験として望ましくない試験片端部での片当たりを防ぐためと、後述する弾性流体潤滑計算による透明膜厚の計算をするためである。透明膜としては先ほどと同様に基油膜を用いた。摺動条件はすべり速度3.0m/s、荷重2000N、油温80℃である。
<Sample>
Mirror-polished steel (carbon steel) was used as the reflective sliding material. The shape was a Φ5 mm disk. However, the sliding surface is not a perfect plane, but has a medium-high shape (spherical shape) with a very large curvature (equivalent to SR1000) by special polishing. This is for preventing the contact at the end of the test piece, which is not desirable as a sliding test, and for calculating the transparent film thickness by elastic fluid lubrication calculation described later. As the transparent film, a base oil film was used as before. The sliding conditions are a sliding speed of 3.0 m / s, a load of 2000 N, and an oil temperature of 80 ° C.
図16に鏡面研磨した鋼円板による干渉像を示す。馬の蹄のような模様が観察されるが、これは馬蹄形状と呼ばれる平板と球の間の流体膜厚分布は馬蹄形状と呼ばれ、中央部の膜厚が厚く、左右端および後端が薄くなる形になることが知られている。本実験例では図中の枠で囲った範囲を解析した。 FIG. 16 shows an interference image by a mirror-polished steel disk. A horseshoe-like pattern is observed, but this is a fluid film thickness distribution between a flat plate called a horseshoe shape and a sphere, called a horseshoe shape. It is known to become thinner. In this experimental example, the range enclosed by the frame in the figure was analyzed.
<未知変数の導出>
未知変数の導出に用いた計測点は図17で示す51点である。図17中において左部の部分(光学膜厚が450nm周辺の領域)に多くの計測点を選択しているのは、この膜厚では各波長の輝度値が先述したピーク・ボトムにあたるからである(470nmがピークで560nmと600nmがボトムになっている)。このような場所では適切な未知変数を導出するために多くの計測点を選択する必要がある。
<Derivation of unknown variable>
The measurement points used for derivation of the unknown variable are 51 points shown in FIG. In FIG. 17, the reason why many measurement points are selected in the left part (region where the optical film thickness is around 450 nm) is that the luminance value of each wavelength corresponds to the above-described peak / bottom at this film thickness. (470nm is the peak and 560nm and 600nm is the bottom). In such a place, it is necessary to select many measurement points in order to derive an appropriate unknown variable.
これらの51点の計測点を用いて、先の静的試験同様、吸収係数はゼロ、屈折率も1.46 として I1(j)とI2(j)を求めた。その結果を図18に示す。 Using these 51 measurement points, as in the previous static test, I 1 (j) and I 2 (j) were obtained with an absorption coefficient of zero and a refractive index of 1.46. The result is shown in FIG.
<油膜厚さ分布>
図19に、図18の未知変数を用いて干渉像から膜厚分布に変換した結果を示す。まず定性的な分布形状に着目すると馬蹄形状となっており、摺動面の油膜厚さ分布として妥当な形状であることがわかる。次に定量的な膜厚値に着目する。摺動面において最大となる中央部の平均膜厚は約400nmであり、最小となる左右端部の膜厚は約140nmであった。これより、先述の静的な計測結果と同様に、従来技術よりも広い膜厚範囲で干渉像から膜厚分布への変換が可能であることが分かる。
<Oil film thickness distribution>
FIG. 19 shows the result of conversion from the interference image to the film thickness distribution using the unknown variable of FIG. First, focusing on the qualitative distribution shape, it becomes a horseshoe shape, and it can be seen that this is a reasonable shape as the oil film thickness distribution on the sliding surface. Next, attention is paid to a quantitative film thickness value. The average film thickness at the central portion that is the maximum on the sliding surface was about 400 nm, and the film thickness at the left and right end portions that was the minimum was about 140 nm. From this, it can be seen that, similar to the static measurement result described above, the interference image can be converted into the film thickness distribution in a film thickness range wider than that of the prior art.
<潤滑計算による膜厚との比較>
膜厚値の妥当性を検討すべく、弾性流体潤滑(EHL)計算による中央部平均膜厚と比較をした。EHL計算には、一般的に用いられるChittenden-Dowsonの式を用いた(非特許文献6(Chittenden, R. J., Dowson, D., Dunn, J. F., Taylor, C.M.: Proc. Roy. Soc. London, A397 (1985) 271)を参照)。Chittenden-Dowsonの式を以下の式(9)に示す。
<Comparison with film thickness by lubrication calculation>
In order to examine the validity of the film thickness value, we compared it with the average film thickness at the center by elastohydrodynamic lubrication (EHL) calculation. For the EHL calculation, a commonly used Chittenden-Dowson equation was used (Non-Patent Document 6 (Chittenden, RJ, Dowson, D., Dunn, JF, Taylor, CM: Proc. Roy. Soc. London, A397 (1985) 271)). The Chittenden-Dowson equation is shown in the following equation (9).
(9)
(9)
ただし、Rxは合成曲率半径(摺動方向)[mm]、Ryは、合成曲率半径(摺動直交方向)[mm]、Wは、垂直荷重[N]、uは、平均摺動速度[m/s]、hcは、中央部油膜厚さ[μm]、βは、圧力粘度指数[Pa-1]、η0は、大気圧粘度[Pa・s]、Eは、合成弾性係数[Pa]である。圧力粘度指数は、非特許文献7(畑ら,トライボロジスト,Vol.55 No.9 (2010))の結果を参考に算出した。その際の油温は80℃として計算した。 Where R x is the composite radius of curvature (sliding direction) [mm], R y is the composite radius of curvature (sliding orthogonal direction) [mm], W is the vertical load [N], u is the average sliding speed [m / s], h c is the central oil film thickness [μm], β is the pressure viscosity index [Pa-1], η 0 is the atmospheric pressure viscosity [Pa · s], and E is the synthetic elastic modulus. [Pa]. The pressure viscosity index was calculated with reference to the results of Non-Patent Document 7 (Hata et al., Tribologist, Vol. 55 No. 9 (2010)). The oil temperature at that time was calculated as 80 ° C.
本試験条件を中央部平均油膜厚さは415nmであり、解析結果と概ね一致する。よって、本実施の形態の計測法は摺動時の透明膜厚においても有効であることが分かる。なお実験値が計算値より小さい理由としては、温度の影響が考えられる。計算では設定油温である80℃を用いたが、実験では摺動面における油温は摺動により80℃以上になるからである。 Under this test condition, the average oil film thickness at the center is 415 nm, which is almost consistent with the analysis result. Therefore, it can be seen that the measurement method of the present embodiment is also effective for the transparent film thickness during sliding. Note that the experimental value is smaller than the calculated value because of the influence of temperature. In the calculation, the set oil temperature of 80 ° C. was used, but in the experiment, the oil temperature on the sliding surface was 80 ° C. or higher due to sliding.
以上説明したように、本発明の実施の形態に係る膜厚計測システムによれば、白色光源からの光を、バンドパスフィルタを用いて3波長の単色光から構成される光にし、透明摺動材と液体膜とを透過させて反射摺動材へ照射して光干渉を生じさせ、生じた光干渉における、3波長の光の各々の輝度を計測し、計測された3波長の光の各々の輝度に基づいて、液体膜の膜厚を計算することにより、実験による事前の干渉色・輝度−膜厚のキャリブレーションなどの煩雑な作業を行うことなく、液体膜の膜厚を計測することができる。また、膜厚測定範囲を向上させることができる。 As described above, according to the film thickness measurement system according to the embodiment of the present invention, the light from the white light source is changed to light composed of monochromatic light of three wavelengths using a bandpass filter, and transparent sliding is performed. The light and the liquid film are transmitted and irradiated to the reflective sliding material to cause optical interference. In the generated optical interference, the brightness of each of the three wavelengths of light is measured, and each of the measured three wavelengths of light is measured. By measuring the film thickness of the liquid film based on the brightness of the liquid, it is possible to measure the film thickness of the liquid film without performing complicated work such as prior interference color / brightness-film thickness calibration by experiment Can do. Moreover, the film thickness measurement range can be improved.
また、未知変数として、透明膜の、3波長の光の各々に対する吸光係数を含むことにより、透明膜に着色があっても、膜厚を計測することができる。また、未知変数として、透明膜の、3波長の光の各々に対する屈折率を含むようにすることにより、透明膜が、油膜などの材質であっても、膜厚を計測することができる。 Moreover, even if the transparent film is colored, the film thickness can be measured by including the absorption coefficient for each of the three wavelengths of light of the transparent film as an unknown variable. Moreover, even if the transparent film is made of a material such as an oil film, the film thickness can be measured by including the refractive index of each of the three wavelengths of the transparent film as an unknown variable.
なお、上記の実施の形態では、一部の計測点について、上記式(1)の関係式から、連立方程式を解くか、最適化手法により、膜厚を算出する場合を例に説明したが、これに限定されるものではない。計測点の数が少ない場合には、全ての計測点について、上記式(1)の関係式から、連立方程式を解くか、最適化手法により、膜厚を算出するようにしてもよい。 In the above-described embodiment, the case where the film thickness is calculated by solving the simultaneous equations or calculating the film thickness by the optimization method from the relational expression of the above expression (1) for some measurement points has been described as an example. It is not limited to this. When the number of measurement points is small, the film thickness may be calculated for all measurement points by solving simultaneous equations from the relational expression (1) or by an optimization method.
また、3波長バンドパスフィルタを透過した照射光を、摺動系に入射する場合を例に説明したが、これに限定されるものではない。例えば、白色光源からの白色光を、摺動系に入射し、摺動系からの反射光を、3波長バンドパスフィルタ又は分光器を介してカメラにより撮像してもよい。 Moreover, although the case where the irradiation light which permeate | transmitted the 3 wavelength band pass filter injects into a sliding system was demonstrated to the example, it is not limited to this. For example, white light from a white light source may be incident on a sliding system, and reflected light from the sliding system may be captured by a camera via a three-wavelength bandpass filter or a spectroscope.
10 膜厚計測システム
20 光学系
22 白色光源
26 3波長バンドパスフィルタ
28 ハーフミラー
32 カメラ
40 摺動系
42 透明摺動材
44 部分反射膜
45 透明保護膜
46 液体膜
48 反射摺動材
50 摺動試験機
60 演算装置
62 画像取得部
64 未知変数導出部
66 膜厚値決定部
DESCRIPTION OF SYMBOLS 10 Film thickness measurement system 20 Optical system 22 White light source 26 Three wavelength band pass filter 28 Half mirror 32 Camera 40 Sliding system 42 Transparent sliding material 44 Partial reflection film 45 Transparent protective film 46 Liquid film 48 Reflective sliding material 50 Sliding Testing machine 60 Arithmetic device 62 Image acquisition unit 64 Unknown variable derivation unit 66 Film thickness value determination unit
Claims (11)
前記第1の摺動材料と前記第2の摺動材料とは、荷重を受けながら相対運動し、
前記透明膜は、前記第1の摺動材料と前記第2の摺動材料との間に存在し、
前記第1の摺動材料及び前記透明膜は、光を透過する材質から構成され、
前記第2の摺動材料は、光を反射する材質から構成され、
前記光源からの光を、前記第1の摺動材料と前記透明膜とを透過させて前記第2の摺動材料へ照射して光干渉を生じさせ、
前記光検出器は、複数の計測点について、前記生じた光干渉後の光から単色光と見なせる程度に狭い波長幅の光の輝度を計測し、その際に計測する波長数は2以上であり、
前記演算装置は、前記光検出器によって前記計測点の各々について計測された前記2以上の光の各々の輝度に基づいて、前記2以上の光の各々の輝度と前記透明膜の膜厚との関係を表す関係式であって、前記計測点の各々における前記透明膜の膜厚、及び前記計測点の各々において同一であると仮定した測定環境由来の未知変数を含む関係式から、前記計測点の各々における前記透明膜の膜厚、及び前記測定環境由来の未知変数を求め、
前記透明膜は液体膜である
摺動装置。 A sliding device including a first sliding material, a second sliding material, a transparent film, a photodetector, a light source, and an arithmetic device,
The first sliding material and the second sliding material move relative to each other while receiving a load,
The transparent film exists between the first sliding material and the second sliding material,
The first sliding material and the transparent film are made of a material that transmits light,
The second sliding material is made of a material that reflects light,
Irradiating light from the light source through the first sliding material and the transparent film and irradiating the second sliding material to cause light interference;
The photodetector measures the luminance of light having a wavelength range narrow enough to be regarded as monochromatic light from the generated light-interfered light at a plurality of measurement points, and the number of wavelengths measured at that time is two or more. ,
The arithmetic unit is configured to calculate the brightness of each of the two or more lights and the film thickness of the transparent film based on the brightness of each of the two or more lights measured for each of the measurement points by the photodetector. A relational expression representing a relation, wherein the measurement point is determined from a relational expression including a film thickness of the transparent film at each of the measurement points, and an unknown variable derived from a measurement environment assumed to be the same at each of the measurement points. Determining the film thickness of the transparent film in each of the above , and an unknown variable derived from the measurement environment,
The sliding device , wherein the transparent film is a liquid film .
前記第1の摺動材料と前記第2の摺動材料とは、荷重を受けながら相対運動し、
前記透明膜は、前記第1の摺動材料と前記第2の摺動材料との間に存在し、
前記第1の摺動材料及び前記透明膜は、光を透過する材質から構成され、
前記第2の摺動材料は、光を反射する材質から構成され、
前記光源からの光を、前記第1の摺動材料と前記透明膜とを透過させて前記第2の摺動材料へ照射して光干渉を生じさせ、
前記光検出器は、複数の計測点について、前記生じた光干渉後の光から単色光と見なせる程度に狭い波長幅の光の輝度を計測し、その際に計測する波長数は2以上であり、
前記演算装置は、前記光検出器によって前記計測点の各々について計測された前記2以上の光の各々の輝度に基づいて、前記2以上の光の各々の輝度と前記透明膜の膜厚との関係を表す関係式であって、前記計測点の各々における前記透明膜の膜厚、及び前記計測点の各々において同一であると仮定した測定環境由来の未知変数を含む関係式から、前記計測点の各々における前記透明膜の膜厚、及び前記測定環境由来の未知変数を求め、
前記測定環境由来の未知変数は、前記透明膜の、前記2以上の光の各々に対する吸光係数、及び前記透明膜の、前記2以上の光の各々に対する屈折率の少なくとも一方を含む
摺動装置。 A sliding device including a first sliding material, a second sliding material, a transparent film, a photodetector, a light source, and an arithmetic device,
The first sliding material and the second sliding material move relative to each other while receiving a load,
The transparent film exists between the first sliding material and the second sliding material,
The first sliding material and the transparent film are made of a material that transmits light,
The second sliding material is made of a material that reflects light,
Irradiating light from the light source through the first sliding material and the transparent film and irradiating the second sliding material to cause light interference;
The photodetector measures the luminance of light having a wavelength range narrow enough to be regarded as monochromatic light from the generated light-interfered light at a plurality of measurement points, and the number of wavelengths measured at that time is two or more. ,
The arithmetic unit is configured to calculate the brightness of each of the two or more lights and the film thickness of the transparent film based on the brightness of each of the two or more lights measured for each of the measurement points by the photodetector. A relational expression representing a relation, wherein the measurement point is determined from a relational expression including a film thickness of the transparent film at each of the measurement points, and an unknown variable derived from a measurement environment assumed to be the same at each of the measurement points. Determining the film thickness of the transparent film in each of the above , and an unknown variable derived from the measurement environment ,
The unknown device derived from the measurement environment includes at least one of an absorption coefficient of the transparent film for each of the two or more lights and a refractive index of the transparent film for each of the two or more lights .
ただし、jは、前記2以上の光の各々に割り当てた番号を表し、iは、前記複数の計測点の各々に割り当てた番号を表し、I(i,j)は、前記光検出器によってi番目の計測点について計測されたj番目の光の輝度を表し、I1(j)は、j番目の光の表面光強度を表し、I2(j)は、j番目の光の、前記透明膜による吸光が生じない場合の裏面光強度を表し、α(j)は、前記透明膜のj番目の光に対する吸光係数を表し、n(j)は、前記透明膜のj番目の光に対する屈折率を表し、t(i)は、i番目の計測点における前記透明膜の膜厚を表し、λ(j)は、j番目の光の波長を表す。 The relational expression, the sliding device according to any one of claims 1 to 4 represented by the following formula.
Here, j represents a number assigned to each of the two or more lights, i represents a number assigned to each of the plurality of measurement points, and I (i, j) is i by the photodetector. Represents the luminance of the j-th light measured at the measurement point, I 1 (j) represents the surface light intensity of the j-th light, and I 2 (j) represents the transparent film of the j-th light. Represents the light intensity of the back surface when no light absorption occurs, α (j) represents the extinction coefficient for the jth light of the transparent film, and n (j) represents the refractive index of the transparent film for the jth light. T (i) represents the film thickness of the transparent film at the i-th measurement point, and λ (j) represents the wavelength of the j-th light.
前記光検出器によって前記複数の計測点のうちの残りの計測点の各々について計測された前記2以上の光の各々の輝度、及び前記求められた前記測定環境由来の未知変数に基づいて、前記計測点の各々について、前記2以上の光の各々の波長に対する、前記関係式を満たす前記計測点における前記透明膜の膜厚の候補値を求め、前記2以上の光の各々の波長に対する前記計測点における前記透明膜の膜厚の候補値から、波長間の合致法を用いて前記計測点における前記透明膜の膜厚値を決定する請求項1〜請求項6の何れか1項記載の摺動装置。 The arithmetic unit is configured for the relational expression based on the luminance of each of the two or more lights measured for each of some of the plurality of measurement points by the photodetector. Solve the equation or optimize the thickness of the transparent film at each of the measurement points and determine unknown variables derived from the measurement environment by an optimization method.
Based on the brightness of each of the two or more lights measured for each of the remaining measurement points of the plurality of measurement points by the photodetector, and the obtained unknown variable derived from the measurement environment, For each measurement point, a candidate value for the film thickness of the transparent film at the measurement point satisfying the relational expression for each wavelength of the two or more lights is obtained, and the measurement for each wavelength of the two or more lights is performed. from the membrane candidate value of the thickness of the transparent film at a point, sliding according to any one of claims 1 to 6 for determining the thickness values of the transparent film in the measuring points using the matching method between the wavelengths Moving device.
前記第1の摺動材料と前記第2の摺動材料とは、荷重を受けながら相対運動し、
前記液体膜は、前記第1の摺動材料と前記第2の摺動材料との間に存在し、
前記第1の摺動材料及び前記液体膜は、光を透過する材質から構成され、
前記第2の摺動材料は、光を反射する材質から構成され、
前記フラッシュランプからの光を、前記第1の摺動材料と前記液体膜とを透過させて前記第2の摺動材料へ照射して光干渉を生じさせ、
前記光検出器は、前記生じた光干渉後の光から単色光と見なせる程度に狭い波長幅の光の輝度を計測し、その際に計測する波長数は2以上であり、
前記演算装置は、前記光検出器によって計測された前記2以上の光の各々の輝度に基づいて、前記液体膜の膜厚を計算する
摺動装置。 A sliding device comprising a first sliding material, a second sliding material, a liquid film , a photodetector, a flash lamp , and an arithmetic device,
The first sliding material and the second sliding material move relative to each other while receiving a load,
The liquid film exists between the first sliding material and the second sliding material,
The first sliding material and the liquid film are made of a material that transmits light,
The second sliding material is made of a material that reflects light,
Irradiating the light from the flash lamp through the first sliding material and the liquid film and irradiating the second sliding material to cause light interference;
The photodetector measures the luminance of light having a narrow wavelength width so that it can be regarded as monochromatic light from the generated light after interference, and the number of wavelengths to be measured at that time is two or more,
The arithmetic device calculates the film thickness of the liquid film based on the brightness of each of the two or more lights measured by the photodetector.
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