JP4453920B2 - Touch probe contact detection method and apparatus - Google Patents

Touch probe contact detection method and apparatus Download PDF

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JP4453920B2
JP4453920B2 JP2005328555A JP2005328555A JP4453920B2 JP 4453920 B2 JP4453920 B2 JP 4453920B2 JP 2005328555 A JP2005328555 A JP 2005328555A JP 2005328555 A JP2005328555 A JP 2005328555A JP 4453920 B2 JP4453920 B2 JP 4453920B2
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touch probe
excitation frequency
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JP2007132890A (en
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洋 水本
誠 薮谷
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Nachi Fujikoshi Corp
Tottori University
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Tottori University
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本発明は、精密、超精密計測分野で使用される３次元測定機や超精密変位測定器、形状測定器における触針部と測定対象との接触を検出するタッチプローブの接触検出方法及び装置に関する。   The present invention relates to a touch probe contact detection method and apparatus for detecting contact between a stylus part and a measurement object in a three-dimensional measuring instrument, an ultra-precise displacement measuring instrument, and a shape measuring instrument used in the fields of precision and ultra-precision measurement. .

従来、接触式変位測定器において、タッチプローブが使用されている。タッチプローブの接触検出方法は、例えば測定対象とプローブの先端との接触によって生じる変位を測定したり、変位により接点を機械的に開閉したものがある。しかし、これ等のものは、検出分解能と接点開閉に必要な力すなわち測定圧とが互いに関係しあうものであるので、測定対象への損傷を和らげるために測定圧を下げようとする検出が不安定になり、それを避けるために測定圧を上げると測定対象物に損傷を与えるという問題があった。また、測定方向毎検出機構が一組必要なことが多く、プローブ形状が大きくなる。このような短所は被測定物が小さくなるほど顕著に測定結果に影響することとなる。また、原則的に触針部は測定対象物の測定面に垂直に接触するように設計されており、測定面の傾きが増加すると測定誤差を生じたり、測定不能に陥るなどの問題がある。   Conventionally, touch probes are used in contact displacement measuring instruments. As a touch probe contact detection method, for example, there is a method in which a displacement caused by contact between a measurement object and a probe tip is measured, or a contact is mechanically opened and closed by the displacement. However, in these cases, since the detection resolution and the force required for opening and closing the contact, that is, the measurement pressure, are related to each other, the detection to lower the measurement pressure to reduce the damage to the measurement object is not possible. There is a problem that if the measurement pressure is increased in order to avoid the problem, the measurement object is damaged. In addition, a set of detection mechanisms for each measurement direction is often required, which increases the probe shape. Such disadvantages significantly affect the measurement results as the object to be measured becomes smaller. Further, in principle, the stylus part is designed so as to be in contact with the measurement surface of the measurement object perpendicularly, and there is a problem that when the inclination of the measurement surface increases, a measurement error occurs or measurement becomes impossible.

そこで、特許文献１等においては、タッチプローブの触針を振動させ、その振動波形を検出するようにし、触針が被測定物に接触したときの振動波形の変化を検出することにより、接触したと判断している。振動波形の変化は共振周波数の変化や、振幅の変化をとらえている。また、特許文献２においては、触針の加振を触針の固有振動数で振動させ振幅を大きくして感度をあげ、ハウジング等の固有振動数（基本周波数及びその高調波成分）と異ならせることにより外乱の影響を減少させている。   Therefore, in Patent Document 1, etc., the stylus of the touch probe is vibrated and the vibration waveform is detected, and the contact is made by detecting the change in the vibration waveform when the stylus contacts the object to be measured. Judging. The change in the vibration waveform captures the change in the resonance frequency and the change in the amplitude. Further, in Patent Document 2, the stylus is vibrated at the natural frequency of the stylus and the amplitude is increased to increase the sensitivity, which is different from the natural frequency (basic frequency and its harmonic components) of the housing. This reduces the influence of disturbance.

一方、特許文献３においては、触針の先端と被測定側との間に交流電圧を印加し、その結果生ずる触針の二倍高調波振動を検出して、表面電位、電荷、誘電率等の電気情報を得て、非接触による電気力プローブ顕微鏡操作方法が提案されている。このものは、試料−探針間の距離と板バネの二倍高調波振動振幅との関係をあらかじめ計測し、これにより適当な試料−探針間の距離となる板バネの二倍高調波振動振幅の設定値を定め、探針を試料上の測定点に近づけてこの設定値になったところで、幾種類かの電気的情報を収集した後、探針を試料から離し、次の試料上の測定点に移動させ、同様な操作で電気的情報を収集して、試料の形状を測定するものである。
特開昭４８−６０６５３号公報 特許第２６２５３６４号公報 特開平８−２２０１１０号公報 On the other hand, in Patent Document 3, an alternating voltage is applied between the tip of the stylus and the measured side, and the resulting second harmonic vibration of the stylus is detected to detect surface potential, charge, dielectric constant, etc. A non-contact electric force probe microscope operating method has been proposed. This pre-measures the relationship between the distance between the sample and the probe and the second harmonic vibration amplitude of the leaf spring, and thereby the second harmonic vibration of the leaf spring that becomes the appropriate distance between the sample and the probe. After setting the amplitude setting value and bringing the probe close to the measurement point on the sample and reaching this setting value, after collecting several types of electrical information, the probe is moved away from the sample and the next sample on the sample is collected. It moves to a measurement point, collects electrical information by the same operation, and measures the shape of the sample.
Japanese Patent Laid-Open No. 48-60653 Japanese Patent No. 2625364 JP-A-8-220110

しかし、特許文献１，２のものでは、振幅の変化の感度を上げようとすると、接触圧を大きくする必要がある。また、触針と被測定物との接触角度によっても振幅が変化するので、接触角度が小さくなると感度が低下してしまい、大きな角度範囲にわたって安定して振幅変化をとらえることはできないという問題が依然として残る。また、ノイズの影響を下げたり感度を上げるためには励起周波数をプローブの固有振動数にするのがよいが、固有振動数では振幅が大きくなり接触圧を減じることは困難となり、いわんや接触圧を任意に設定するのは困難であるという問題があった。   However, in Patent Documents 1 and 2, it is necessary to increase the contact pressure in order to increase the sensitivity of the amplitude change. In addition, since the amplitude changes depending on the contact angle between the stylus and the object to be measured, the sensitivity decreases when the contact angle decreases, and the problem that the amplitude change cannot be stably captured over a large angle range still remains. Remain. In order to reduce the influence of noise and increase sensitivity, it is better to set the excitation frequency to the natural frequency of the probe. However, it becomes difficult to reduce the contact pressure at the natural frequency, so it is difficult to reduce the contact pressure. There was a problem that it was difficult to set arbitrarily.

また、特許文献３のものは、被測定物と探針との間に生ずる電気的な高調波の値を非接触で測定するものであるが、被測定物と探針との距離と高調波の振幅とをあらかじめ測定しなければならず、非常に調整が面倒であり、接触タイプのような簡便さに欠けるという問題があった。   Patent Document 3 measures the value of electrical harmonics generated between the object to be measured and the probe in a non-contact manner. The distance between the object to be measured and the probe and the harmonics are measured. Therefore, there is a problem that adjustment is very troublesome and lacks in convenience as in a contact type.

本発明の課題は、かかる従来の問題点に鑑みて、測定圧が低く測定対象が光学面であっても有害な損傷を与えず、さらには測定対象面が水平な場合のみならず、相当な角度で傾いている場合においても、触針部と測定対象物との接触が確実に検出できるタッチプローブの接触検出方法及び装置を提供することである。   In view of such conventional problems, the problem of the present invention is not to cause harmful damage even when the measurement pressure is low and the measurement target is an optical surface. To provide a touch probe contact detection method and apparatus capable of reliably detecting contact between a stylus part and a measurement object even when tilted at an angle.

本発明においては、一定の励起周波数（ｆ）で正弦波振動させられた触針部と、前記触針部の振動波形を測定出力するセンサユニットと、を有するタッチプローブの接触検出方法であって、前記センサユニットによって出力された振動波形を周波数分布に変換し、前記励起周波数の整数（ｎ）倍の所定の高調波（ｎ×ｆ）の値があらかじめ定められた閾値以上となった時に、前記タッチプローブが被測定対象物に接触したと判定するタッチプローブの接触検出方法を提供することにより前述した課題を解決した。   In the present invention, there is provided a touch probe contact detection method comprising a stylus portion that is sine-wave vibrated at a constant excitation frequency (f), and a sensor unit that measures and outputs a vibration waveform of the stylus portion. When the vibration waveform output by the sensor unit is converted into a frequency distribution, and a value of a predetermined harmonic (n × f) that is an integer (n) times the excitation frequency is equal to or greater than a predetermined threshold value, The above-described problem has been solved by providing a touch probe contact detection method for determining that the touch probe has come into contact with an object to be measured.

即ち、周波数ｆの正しい正弦波で振動している触針の周波数特性は、周波数成分がｆのみの線スペクトルとなる。この触針が測定対象物（被測定物）に接触した場合、振幅に目立った変化が現れる前に、周波数特性には顕著な高調波成分ｎ×ｆが現れる。本発明は、この性質を利用したものである。従来の振幅の変化をとらえるものでは、接触した時の振幅の変化量はゼロからスタートして徐々に大きくなるので、検出すべき振幅変化の度合いが緩やかであり検出誤差を生じやすい。しかし、本発明においては高調波の発生という全く振動数の異なる振動の発生を検出するので、検出しやすく誤差も少ない。さらに、被測定物と触針の接触角度の制約が緩いため、傾斜した面に対しても検出感度を保つことができる。なお、ノイズ等の影響を避けるため、あらかじめ定められた閾値を設けて振動の発生を検出するようにした。   That is, the frequency characteristic of the stylus that vibrates with a correct sine wave having the frequency f is a line spectrum having only the frequency component f. When the stylus comes into contact with the measurement object (object to be measured), a significant harmonic component n × f appears in the frequency characteristics before a noticeable change in amplitude appears. The present invention utilizes this property. In the conventional device that detects changes in amplitude, the amount of change in amplitude at the time of contact starts from zero and gradually increases. Therefore, the degree of amplitude change to be detected is gradual and a detection error is likely to occur. However, in the present invention, since the occurrence of vibrations with completely different frequencies, ie, the generation of harmonics, is detected, it is easy to detect and there are few errors. Further, since the restriction on the contact angle between the object to be measured and the stylus is loose, the detection sensitivity can be maintained even on an inclined surface. In order to avoid the influence of noise or the like, a predetermined threshold is provided to detect the occurrence of vibration.

また、請求項２に記載の発明においては、前記所定の高調波は前記励起周波数（ｆ）の二倍の高調波（２×ｆ）とした。二倍の高調波の振幅がもっとも大きくなるからである。さらに、請求項３に記載の発明においては、前記励起周波数（ｆ）は触針部の固有振動数とは異なるようにした。固有振動数と同じであると、触針の振幅が大きくなり、感度は高くなるが、接触圧が大きくなるとともに、外乱として高調波が発生しやすいからである。さらに、固有振動数に限定されることなく励起周波数が任意に選べるので所望の測定圧を得ることができる。   In the invention described in claim 2, the predetermined harmonic is a harmonic (2 × f) that is twice the excitation frequency (f). This is because the amplitude of the double harmonic becomes the largest. Furthermore, in the invention described in claim 3, the excitation frequency (f) is different from the natural frequency of the stylus part. This is because when the frequency is the same as the natural frequency, the amplitude of the stylus increases and the sensitivity increases, but the contact pressure increases and harmonics are easily generated as disturbance. Further, since the excitation frequency can be arbitrarily selected without being limited to the natural frequency, a desired measurement pressure can be obtained.

かかるタッチプローブの検出方法は、次のような装置にて実施できる。すなわち、請求項４に記載の発明においては、被測定物に接触可能にされた触針と、前記触針を一定の励起周波数（ｆ）で振動させる振動子と、前記触針部の振動波形を測定出力するセンサユニットと、を有するタッチプローブの接触検出装置であって、前記センサユニットによって出力された振動波形から周波数分布を求める周波数解析器と、前記周波数分析の励起周波数の整数（ｎ）倍の所定の高調波（ｎ×ｆ）を出力する出力器と、前記出力器からの出力をあらかじめ定めた閾値と比較しＯＮ−ＯＦＦ信号を出力する比較器と、を有するタッチプローブの接触検出装置を提供する。   Such a touch probe detection method can be implemented by the following apparatus. That is, in the invention described in claim 4, the stylus that can contact the object to be measured, the vibrator that vibrates the stylus at a constant excitation frequency (f), and the vibration waveform of the stylus part. A touch probe contact detection device comprising: a frequency analyzer for obtaining a frequency distribution from a vibration waveform output by the sensor unit; and an integer (n) of excitation frequencies of the frequency analysis. Touch probe contact detection comprising: an output device that outputs a predetermined double harmonic (n × f); and a comparator that outputs an ON-OFF signal by comparing an output from the output device with a predetermined threshold value Providing equipment.

また、請求項５に記載の発明においては、前記所定の高調波は前記励起周波数（ｆ）の二倍の高調波（２×ｆ）であるタッチプローブの接触検出装置とするのがよい。さらに、請求項６に記載の発明においては、前記励起周波数（ｆ）は触針部の固有振動数とは異なるようにされているタッチプローブの接触検出装置とするのが好ましい。   In a fifth aspect of the invention, the touch probe contact detection device may be configured such that the predetermined harmonic is a harmonic (2 × f) that is twice the excitation frequency (f). Furthermore, in the invention described in claim 6, it is preferable that the excitation frequency (f) is a touch probe contact detection device in which the natural frequency of the stylus part is different.

本発明においては、高調波の発生を検出することにより、触針の被測定物への接触を判断するようにしたので、感度が良好なものとなった。また、傾斜した面に対しても検出感度を保つことができるので、半球面のほぼ全領域が測定可能となり、マイクロレンズ等のような小型で、湾曲した部分の測定等が可能になった。さらに、閾値により高調波の発生を検出するのでノイズの影響も少なく、接触を確実に検出できるものとなった。   In the present invention, since the generation of harmonics is detected to determine the contact of the stylus with the object to be measured, the sensitivity is improved. In addition, since the detection sensitivity can be maintained even on an inclined surface, it is possible to measure almost the entire area of the hemisphere, and it is possible to measure a curved portion that is small, such as a microlens. Furthermore, since the generation of harmonics is detected by the threshold value, the influence of noise is small, and contact can be reliably detected.

また、請求項２、５に記載の発明においては、高調波を励起周波数（ｆ）の二倍の高調波（２×ｆ）として感度を向上させた。さらに、請求項３、６に記載の発明においては、励起周波数（ｆ）を触針部の固有振動数とは異ならせ、接触圧を小さくすることができるので、被測定面の損傷を少なくできるものとなった。   In the inventions according to claims 2 and 5, the sensitivity is improved by setting the harmonic to a harmonic (2 × f) that is twice the excitation frequency (f). Further, in the inventions according to claims 3 and 6, the excitation frequency (f) can be made different from the natural frequency of the stylus part and the contact pressure can be reduced, so that the surface to be measured can be less damaged. It became a thing.

本発明の実施の形態について図を参照して説明する。図１は本発明の実施の形態を示すタッチプローブの接触検出装置のシステムの概念図である。図１に示すように、本発明タッチプローブ接触検出装置１は、被測定物２に対して進退可能にされた移動体３に垂直に板バネ４が固定されている。また、板バネ４の板面４ａ，４ｂは移動体の移動方向に向けられ、板バネが移動体の移動方向に振動するように取り付けられている。先端５ａが鋭利にされた棒状のプローブ（触針）５が板バネの被測定物２側の板面４ｂに対し垂直に固定され所謂カンチレバー４′を形成している。板バネ４を挟んでプローブ５の反対側に圧電素子（振動子）６がその変位方向が板バネの板面４ａに対して垂直方向となるように取り付けられている。さらに、プローブ５又は圧電素子６の近傍に板バネ４の振動波形を測定出力するセンサユニット７が板バネの板面４ｂに取り付けられている。圧電素子６には増幅器８を介して正弦波関数発生器（ＦＦＴアナライザ等でもよい）９が接続され、正弦波関数発生器より与えられる正弦波信号（励起周波数（ｆ））により圧電素子を介してプローブ５が正弦波振動するようにされている。   Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram of a system of a touch probe contact detection device according to an embodiment of the present invention. As shown in FIG. 1, in the touch probe contact detection device 1 of the present invention, a leaf spring 4 is fixed perpendicularly to a moving body 3 that can be moved back and forth with respect to an object 2 to be measured. The plate surfaces 4a and 4b of the plate spring 4 are directed in the moving direction of the moving body, and the plate spring is attached so as to vibrate in the moving direction of the moving body. A rod-like probe (stylus) 5 having a sharpened tip 5a is fixed perpendicularly to a plate surface 4b on the measured object 2 side of a plate spring to form a so-called cantilever 4 '. A piezoelectric element (vibrator) 6 is attached to the opposite side of the probe 5 with the leaf spring 4 interposed therebetween so that the displacement direction is perpendicular to the plate surface 4a of the leaf spring. Further, a sensor unit 7 that measures and outputs the vibration waveform of the leaf spring 4 is attached to the leaf surface 4 b of the leaf spring in the vicinity of the probe 5 or the piezoelectric element 6. A sine wave function generator (FFT analyzer or the like) 9 is connected to the piezoelectric element 6 via an amplifier 8, and a sine wave signal (excitation frequency (f)) given from the sine wave function generator is passed through the piezoelectric element. Thus, the probe 5 is configured to vibrate sinusoidally.

センサユニット７からの出力信号は増幅器１０、アナログデジタル変換器（以下「Ａ／Ｄ変換器」という）１１を介してパーソナルコンピュータ（以下「ＰＣ」という）１２に入力される。ＰＣに入力されたセンサユニット７からの出力信号はプログラムにより周波数解析（フーリエ変換）され、周波数分析によって励起周波数ｆの２倍の高調波（２×ｆ）の強度を出力し、この出力とあらかじめ設定された閾値と比較しＯＮ−ＯＦＦ信号を内部出力するようにされている。なお、ＰＣに代えて、センサユニットによって出力された振動波形を周波数分布に変換する周波数解析器と、周波数分析の励起周波数の２倍の所定の高調波（２×ｆ）の強度を出力する出力器と、出力器からの出力をあらかじめ定めた閾値と比較しＯＮ−ＯＦＦ信号を出力する比較器を設けるようにしてもよいことは言うまでもない。   An output signal from the sensor unit 7 is input to a personal computer (hereinafter referred to as “PC”) 12 via an amplifier 10 and an analog-digital converter (hereinafter referred to as “A / D converter”) 11. The output signal from the sensor unit 7 input to the PC is subjected to frequency analysis (Fourier transform) by the program, and the intensity of the harmonic (2 × f) twice the excitation frequency f is output by frequency analysis. An ON-OFF signal is internally output in comparison with a set threshold value. Instead of the PC, a frequency analyzer that converts the vibration waveform output by the sensor unit into a frequency distribution, and an output that outputs the intensity of a predetermined harmonic (2 × f) that is twice the excitation frequency of the frequency analysis. It goes without saying that a comparator and a comparator that outputs an ON-OFF signal by comparing the output from the output device with a predetermined threshold value may be provided.

移動台３は基台２０の案内面２０ａを移動するようにされ、基台と移動台間に移動台移動装置２１が取り付けられている。また、移動台３と基台２０との間にリニアスケール２２が取り付けられ移動台と基台との距離を測定可能にされている。移動装置２１は圧電素子にされ、ＰＣからデジタルアナログ変換器（以下「Ｄ／Ａ変換器」という）２３、増幅器２４を介して電圧が印可され数μｍ〜数百μｍの変位が可能にされている。さらに、リニアスケール２２からの出力信号は増幅器２５、Ａ／Ｄ変換器２６を介してＰＣにフィードバック入力され、ＰＣ内で、移動装置のリニアスケールによるフィードバック制御を行うようにされている。   The moving table 3 moves on the guide surface 20a of the base 20, and a moving table moving device 21 is attached between the base and the moving table. In addition, a linear scale 22 is attached between the moving table 3 and the base 20 so that the distance between the moving table and the base can be measured. The moving device 21 is made into a piezoelectric element, and a voltage is applied from a PC through a digital / analog converter (hereinafter referred to as “D / A converter”) 23 and an amplifier 24 to enable displacement of several μm to several hundred μm. Yes. Further, an output signal from the linear scale 22 is fed back to the PC via an amplifier 25 and an A / D converter 26, and feedback control using the linear scale of the mobile device is performed in the PC.

かかるタッチプローブ接触検出装置の使用方法は例えば、次にようにされる。正弦波関数発生器９から出力された正弦波信号を増幅器８を通して、振動子６に入力し板バネ４を片持ち梁振動させる。板バネ４の振動をセンサユニット７で読み取り、増幅器１０、Ａ／Ｄ変換器１１を介してＰＣ１２内に取り込み、ＰＣ内で周波数解析を行い、励起周波数ｆの２倍高調波の値が所定の閾値以上であるかどうか監視する。一方、ＰＣ１２よりステップ信号を出力し、Ｄ／Ａ変換器２３、増幅器２４を通して、移動装置（圧電素子）２１に印可し、移動台３を被測定物２側に近づける。同時に移動台３の変位をリニアスケール２２で読み取り、増幅器２５、Ａ／Ｄ変換器２６を介してＰＣにフィードバック入力される。励起周波数ｆの２倍高調波の値が所定の閾値以上となった時に、プローブ５が被測定物２と接触していると判断し、その時のリニアスケール２２の値を読み取ることにより位置測定を行う。   For example, the method of using such a touch probe contact detection device is as follows. The sine wave signal output from the sine wave function generator 9 is input to the vibrator 6 through the amplifier 8 to vibrate the leaf spring 4 in a cantilever manner. The vibration of the leaf spring 4 is read by the sensor unit 7 and taken into the PC 12 via the amplifier 10 and the A / D converter 11, and the frequency analysis is performed in the PC. The value of the second harmonic of the excitation frequency f is a predetermined value. Monitor if it is above threshold. On the other hand, a step signal is output from the PC 12, applied to the moving device (piezoelectric element) 21 through the D / A converter 23 and the amplifier 24, and the moving table 3 is brought closer to the measured object 2 side. At the same time, the displacement of the moving table 3 is read by the linear scale 22 and fed back to the PC via the amplifier 25 and the A / D converter 26. When the value of the second harmonic of the excitation frequency f becomes a predetermined threshold value or more, it is determined that the probe 5 is in contact with the DUT 2, and the position is measured by reading the value of the linear scale 22 at that time. Do.

本実施の形態では、接触したときの高調波について詳述する。図２は前述した装置を用いて、振動子６の励起周波数を２００Ｈｚとしたときの未接触状態での周波数解析結果、図３は接触状態での周波数解析結果である。図２に示すように、全体の周波数に渡りノイズがあるものの、未接触状態では、周波数が２００Ｈｚでピークが現れているが、その他の周波数では特にピークはない。これに対し図３に示すように、接触状態では、周波数が２００Ｈｚでピークがあり、さらに励起周波数の２倍高調波である４００Ｈｚで小さなピークが発生していることがわかる。ノイズが無ければ、この４００Ｈｚでのピークの有無のみを判定するだけで良いが、実際にはノイズがあるので、閾値を設けて、接触・非接触を判定するのがよいことがわかる。   In the present embodiment, harmonics when touched will be described in detail. 2 shows a frequency analysis result in a non-contact state when the excitation frequency of the vibrator 6 is set to 200 Hz using the above-described apparatus, and FIG. 3 shows a frequency analysis result in a contact state. As shown in FIG. 2, although there is noise over the entire frequency, a peak appears at a frequency of 200 Hz in a non-contact state, but there is no particular peak at other frequencies. In contrast, as shown in FIG. 3, it can be seen that in the contact state, there is a peak at a frequency of 200 Hz, and a small peak is generated at 400 Hz, which is a second harmonic of the excitation frequency. If there is no noise, it is only necessary to determine whether or not there is a peak at 400 Hz. However, since there is actually noise, it can be seen that it is preferable to determine a contact / non-contact by setting a threshold value.

また、接触角を４５度斜め方向で接触するようにして、同様な測定を行った。図４は４５度の接触角での接触状態での周波数解析結果である。図４に示すように、前述した図３よりノイズが若干大きくなるも、接触時にはほぼ同程度の高調波が発生していることがわかる。このように、本発明によれば、接触角の影響も非常に少なくできることがわかる。   In addition, the same measurement was performed with a contact angle of 45 degrees in an oblique direction. FIG. 4 shows a frequency analysis result in a contact state at a contact angle of 45 degrees. As shown in FIG. 4, although the noise is slightly larger than in FIG. 3 described above, it can be seen that almost the same harmonics are generated at the time of contact. Thus, according to this invention, it turns out that the influence of a contact angle can also be made very small.

このように、本実施の形態によれば、測定波形の振幅の変位等の常に発生している測定値の変化を測定して、接触・非接触を判定するのではなく、高調波の発生という質的な変化をとらえて接触・非接触を判定するので、ノイズの影響が少なく、誤差もすくない高精度の判定ができ、接触角も広い範囲でカバーできることがわかる。   As described above, according to the present embodiment, it is referred to as the generation of harmonics, not to determine contact / non-contact by measuring a change in a measurement value that is constantly generated, such as a displacement of the amplitude of a measurement waveform. Since contact / non-contact is determined based on qualitative changes, it can be seen that the determination with high accuracy with little influence of noise and less error can be made, and the contact angle can be covered in a wide range.

次に、本発明の測定圧について述べる。前述したような片持ち梁による振動においては、振動振幅ａ、振動周波数ｆ、振動質量ｍ、測定圧Ｎとすると、
Ｎ＝ａ・（２πｆ）2・ｍ となる。したがって、振動周波数ｆにより測定圧Ｎを調節できることになる。
また、振動数が固有振動数ｆｎであれば、板バネのバネ常数ｋとして、
（２πｆｎ）2＝ｋ／ｍ であるので、
Ｎ＝ａ・ｋ となる。 Next, the measurement pressure of the present invention will be described. In the vibration caused by the cantilever as described above, when the vibration amplitude a, the vibration frequency f, the vibration mass m, and the measurement pressure N are given,
N = a · (2πf) 2 · m Therefore, the measurement pressure N can be adjusted by the vibration frequency f.
If the frequency is the natural frequency fn, the spring constant k of the leaf spring is
Since (2πfn) 2 = k / m,
N = a · k.

このように、固有振動数を用いた際は、振動振幅及び板バネのバネ常数で測定圧が決まってしまう。請求項３，６のように、本発明においては励起周波数を固有振動数に限定することなく、任意の周波数を選んでも容易に接触・非接触の判定が可能であるので、所望の測低圧、より低い測低圧で接触・非接触の判定が可能である。   Thus, when the natural frequency is used, the measurement pressure is determined by the vibration amplitude and the spring constant of the leaf spring. As described in claims 3 and 6, in the present invention, the excitation frequency is not limited to the natural frequency, and it is possible to easily determine contact / non-contact even if any frequency is selected. Contact / non-contact can be determined at a lower measured pressure.

なお、本発明の実施の形態においては、板バネ等を用いた例で説明したが、その他の振動体、振動方向でもよい。また、関数発生器、振動子、測定素子等、種々のものが使用、適用できることは言うまでもない。   In the embodiment of the present invention, an example using a leaf spring or the like has been described, but other vibration bodies and vibration directions may be used. Needless to say, various functions such as a function generator, a vibrator, and a measuring element can be used and applied.

本発明の実施の形態を示すタッチプローブの接触検出装置のシステムの概念図である。It is a conceptual diagram of the system of the contact detection apparatus of the touch probe which shows embodiment of this invention. 振動子の励起周波数を２００Ｈｚとしたときの未接触状態での周波数解析結果である。It is a frequency analysis result in a non-contact state when the excitation frequency of the vibrator is 200 Hz. 振動子の励起周波数を２００Ｈｚとしたときの接触状態での周波数解析結果である。It is a frequency analysis result in a contact state when the excitation frequency of the vibrator is 200 Hz. 振動子の励起周波数を２００Ｈｚとし、接触角を４５度としたときの接触状態での周波数解析結果である。It is a frequency analysis result in a contact state when the excitation frequency of the vibrator is 200 Hz and the contact angle is 45 degrees.

符号の説明Explanation of symbols

１ タッチプローブの接触検出装置
２ 被測定対象物
５ タッチプローブ
５ａ 触針部
６ 振動子
７ センサユニット
１２ ＰＣ、周波数解析器、出力器、比較器
ｆ 励起周波数
DESCRIPTION OF SYMBOLS 1 Touch probe contact detection apparatus 2 Object to be measured 5 Touch probe 5a Touch probe 6 Vibrator 7 Sensor unit 12 PC, frequency analyzer, output device, comparator f Excitation frequency

Claims (6)

一定の励起周波数（ｆ）で正弦波振動させられた触針部と、前記触針部の振動波形を測定出力するセンサユニットと、を有するタッチプローブの接触検出方法であって、前記センサユニットによって出力された振動波形の周波数分布を求め、前記励起周波数の整数（ｎ）倍の所定の高調波（ｎ×ｆ）の値があらかじめ定められた閾値以上となった時に、前記タッチプローブが被測定対象物に接触したと判定することを特徴とするタッチプローブの接触検出方法。 A touch probe contact detection method comprising: a stylus portion that is sine-wave vibrated at a constant excitation frequency (f); and a sensor unit that measures and outputs a vibration waveform of the stylus portion. The frequency distribution of the output vibration waveform is obtained, and the touch probe is measured when the value of a predetermined harmonic (n × f) that is an integer (n) times the excitation frequency exceeds a predetermined threshold value. A method for detecting contact of a touch probe, comprising: determining that the object has been touched. 前記所定の高調波は前記励起周波数（ｆ）の二倍の高調波（２×ｆ）であることを特徴とする請求項１記載のタッチプローブの接触検出方法。 The touch detection method according to claim 1, wherein the predetermined harmonic is a harmonic (2 × f) that is twice the excitation frequency (f). 前記励起周波数（ｆ）は触針部の固有振動数とは異なるようにされていることを特徴とする請求項１又は２に記載のタッチプローブの接触検出方法。 The touch probe contact detection method according to claim 1, wherein the excitation frequency (f) is different from a natural frequency of the stylus part. 被測定物に接触可能にされた触針と、前記触針を一定の励起周波数（ｆ）で正弦波振動させる振動子と、前記触針部の振動波形を測定出力するセンサユニットと、を有するタッチプローブの接触検出装置であって、前記センサユニットによって出力された振動波形の周波数分布を求める周波数解析器と、前記周波数分析の励起周波数の整数（ｎ）倍の所定の高調波（ｎ×ｆ）を出力する出力器と、前記出力器からの出力をあらかじめ定めた閾値と比較しＯＮ−ＯＦＦ信号を出力する比較器と、を有することを特徴とするタッチプローブの接触検出装置。 A stylus capable of contacting the object to be measured; a vibrator that vibrates the stylus with a sine wave at a constant excitation frequency (f); and a sensor unit that measures and outputs a vibration waveform of the stylus part. A touch probe contact detection device comprising: a frequency analyzer for obtaining a frequency distribution of a vibration waveform output by the sensor unit; and a predetermined harmonic (n × f) that is an integer (n) times the excitation frequency of the frequency analysis. ), And a comparator that compares the output from the output device with a predetermined threshold value and outputs an ON-OFF signal. 前記所定の高調波は前記励起周波数（ｆ）の二倍の高調波（２×ｆ）であることを特徴とする請求項４記載のタッチプローブの接触検出装置。 The touch detection device according to claim 4, wherein the predetermined harmonic is a harmonic (2 × f) that is twice the excitation frequency (f). 前記励起周波数（ｆ）は触針部の固有振動数とは異なるようにされていることを特徴とする請求項４又は５に記載のタッチプローブの接触検出装置。
6. The touch probe contact detection device according to claim 4, wherein the excitation frequency (f) is different from the natural frequency of the stylus part.
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