WO2015001918A1 - Procédé et dispositif de mesure de brouillage - Google Patents

Procédé et dispositif de mesure de brouillage Download PDF

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Publication number
WO2015001918A1
WO2015001918A1 PCT/JP2014/065282 JP2014065282W WO2015001918A1 WO 2015001918 A1 WO2015001918 A1 WO 2015001918A1 JP 2014065282 W JP2014065282 W JP 2014065282W WO 2015001918 A1 WO2015001918 A1 WO 2015001918A1
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Prior art keywords
interference
wave
interference measurement
distance
measurement method
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PCT/JP2014/065282
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English (en)
Japanese (ja)
Inventor
健二 愛甲
啓 志村
成弥 田中
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株式会社日立ハイテクノロジーズ
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Publication of WO2015001918A1 publication Critical patent/WO2015001918A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
    • G01B11/0608—Height gauges

Definitions

  • the present invention relates to an interference measurement method and apparatus, and more particularly to a technique for measuring the thickness of a substance using millimeter waves and terahertz waves and the height of a specific substance in the substance.
  • One of the methods for measuring displacement using millimeter waves is an in-vehicle radar device that measures the distance by modulating millimeter waves.
  • This on-vehicle radar uses radio waves having frequencies of 60 to 61 GHz and 76 to 77 GHz (wavelengths of 4.9 to 5 mm and 3.8 to 3.9 mm), and has been put into practical use since around 1990.
  • the oscillation frequency is FM-modulated, emitted from the antenna, the signal reflected from the target is multiplied with the original signal, analog processing is performed, and the relative speed of the target and the distance to the target are calculated from the signal processing. ing.
  • the operating distance can be detected from about several meters to several hundreds of meters.
  • SS-OCT Scept-Source-Optical-Coherence-Tomography
  • Patent Document 1 As a prior art document related to an on-vehicle radar, for example, there is Patent Document 1, and as a prior art document related to SS-OCT, there is, for example, Non-Patent Document 1.
  • the above-described in-vehicle radar using millimeter waves is designed for the purpose of detecting a vehicle ahead, and thus the detection accuracy of the measurement distance is about several tens of centimeters.
  • the required accuracy when measuring the height of an object under or in a dielectric material or measuring the thickness unevenness of a dielectric film is on the order of several ⁇ m. Can not be satisfied.
  • the displacement measurement method using optical interference phenomenon has been reported in the past with examples using visible light (wavelength of about 350 nm to about 750 nm) or near infrared light (wavelength of about 1 ⁇ m).
  • this wavelength the displacement of the surface can be measured in order to use the reflected light from the surface of the material to be measured.
  • the use of near-infrared light has been actively used because of the absorptance with respect to the wavelength of a living body.
  • the absorptance of the substance is high and it is difficult to acquire internal displacement information. Therefore, the displacement of an opaque substance inside a substance that cannot be seen through by visible light, the thickness of a thin film that is opaque by visible light, and the unevenness of the thin film substrate are measured by a conventional optical displacement measuring device. I can't.
  • SS-OCT for fundus examination uses red laser light with a wavelength of 800 nm to 900 nm or an infrared laser with a wavelength of 1050 nm, and is used for examination of the retina of the fundus. ing.
  • the wavelength since the wavelength is in the vicinity of 1 ⁇ m, it absorbs relatively less moisture than infrared light and enables ophthalmic observation in a deeper region than a conventional red (near 800 nm) light source.
  • the observation of the underlying choroid is limited. This is because, in the case of light in this region, attenuation due to absorption of a dielectric material is large. For this reason, the conventional SS-OCT method is not suitable for measuring the thickness by transmitting the material, or measuring the height and size of the material in the dielectric. Alternatively, it cannot be used for measuring displacement such as defects.
  • An object of the present invention is to solve the above-described problems and provide a displacement measuring method and apparatus for measuring the thickness of a substance and the height of a specific substance in the substance with high accuracy.
  • an interference measurement method in which an object is irradiated with an irradiation wave composed of millimeter waves or terahertz waves, and the surface of the object and the reflection in the object or the object are reflected.
  • an irradiation wave composed of millimeter waves or terahertz waves
  • the surface of the object and the reflection in the object or the object are reflected.
  • the object is irradiated with an irradiation wave consisting of a millimeter wave or a terahertz wave, and from the surface of the object and the back surface of the object or a reflecting surface in the object.
  • a detection unit that detects the interference wave by causing interference between the reflected wave of the reflected wave and the reflected wave from a predetermined reference surface, and the output of the detection unit, the surface of the object and the back surface of the object or the reflecting surface in the object
  • An interference measurement device having a configuration including a calculation unit that calculates the distance between the two is provided.
  • the frequency modulation using millimeter waves and terahertz waves can be used to obtain the characteristics of interference signals at a plurality of frequencies, so that the calculation of the phase difference between the reference surface and the measurement surface can be facilitated. .
  • FIG. 3 is a diagram illustrating an example of a detailed configuration of an interferometer unit according to the first embodiment.
  • FIG. 3 is a diagram for explaining an operation principle of SS-OCT according to the first embodiment. It is a figure which shows generation
  • FIG. It is a figure which shows an example of the determination sequence based on Example 1 whether it is a convex surface or a concave surface.
  • FIG. 6 is a diagram illustrating a specific example of an SS-OCT interference signal according to Embodiment 1.
  • FIG. It is a figure which shows the measurement principle of plate
  • FIG. It is a figure which shows the principle of the interference measurement which concerns on Example 3, and a foreign material inspection under a film
  • FIG. 10 is a diagram illustrating a specific example of an SS-OCT interference signal according to Embodiment 1.
  • FIG. It is a figure which shows the measurement principle of plate
  • FIG. It is a figure which shows the principle of the interference measurement which concerns on Example 3, and a foreign material inspection under a film
  • FIG. 7 It is a figure which shows the structure which aims at the detection efficiency improvement by the reference surface of a multi-partition mirror shape based on Example 7.
  • FIG. It is a figure for demonstrating the dielectric material transmittance
  • the millimeter wave or terahertz wave used in the present invention refers to an electromagnetic wave having a wavelength of 30 ⁇ m to 10 mm.
  • the technical meaning of using these millimeter waves or terahertz waves will be outlined.
  • Millimeter waves or terahertz waves have the property of transmitting through dielectric materials. According to the present invention, it is possible to measure the thickness of the constituent material, the undulation of the surface, etc. through the material. Furthermore, the state of the lower layer of the dielectric material can be seen. In other words, measure the height and depth that cannot be measured with normal visible light by measuring the shape, unevenness, scratch-like dent, or convex shape when the lower layer is not flat, using the property of transmitting light. Is possible.
  • the Schottky barrier diode which is a millimeter wave transmission source, multiplies the input frequency and outputs it, frequency modulation can be easily realized by changing the input frequency.
  • the Gunn Diodes of the other source is a VCO (Voltage Control Oscillator), so frequency modulation is easy, and distance measurement is easy from the data value of the modulated interference wave. It is.
  • the function of the interferometer can be realized with a simple configuration.
  • Displacement measurement methods using frequency modulation using millimeter waves or terahertz waves can obtain the characteristics of interference signals at multiple frequencies, making it easy to calculate the phase difference between the reference surface and the measurement surface. Compared with a typical OCT calculation method, since the calculation method is simple, an expensive arithmetic processor is unnecessary and high-speed calculation is possible.
  • the first embodiment is a displacement measuring method for measuring a displacement amount and a height of a substance under or in a film formed of a dielectric material that transmits millimeter waves, and a displacement measurement. It is an Example regarding an apparatus.
  • a Gunn diode which is a semiconductor material
  • an oscillation source using a Schottky barrier diode and a nonlinear crystal using a wavelength tunable semiconductor laser (LD) as seed light.
  • An oscillation source by frequency conversion used, an oscillation source by a high frequency circuit using an LC circuit, or the like can be used, and it is easy to vary the oscillation frequency in any case.
  • FIG. 1 Under the control of a personal computer (PC) 100 functioning as a calculation unit and a processing unit, an interface (I / F) 101, a transmitter 102, a synthesizer 103, an SBD (Schottky with an attached waveguide and antenna) Barrier Diode) AMC (Active Multi Chain) 104, beam splitter 105, sensor SBD 106 provided with a waveguide and an antenna, lock-in amplifier 107, measurement surface 108, reference surface 109, and control signal of PC 100 is I / F101 is sent to the synthesizer 103, and a drive frequency scan (12.5 GHz to 20 GHz) is performed. The output of synthesizer 103 is sent to AMC (SBD) 104.
  • I / F101 is sent to the synthesizer 103, and a drive frequency scan (12.5 GHz to 20 GHz) is performed.
  • the output of synthesizer 103 is sent to AMC (SBD) 104.
  • the frequency of the millimeter wave oscillator 103 which is an oscillation unit.
  • the frequency is varied by inputting an instruction from the PC 100 to the synthesizer 103 via the I / F 101.
  • the output of the synthesizer 103 is supplied to the AMC (SBD) 104, and the multiplied millimeter wave is output.
  • the synthesizer 103 assuming that 100 GHz is a center frequency, the output is subjected to frequency modulation between 75 GHz and 120 GHz.
  • a synchronizing signal on the oscillator side and the receiver side is supplied from the transmitter 102 oscillating at 1 kHz.
  • On the receiving side there is a lock-in amplifier 107 for detecting weak signals, and after removing the noise strongly with a synchronized band pass filter, the intensity of the interference wave is output to the PC 100 to perform highly sensitive interference measurement. Is realized.
  • a millimeter wave with frequency modulation is used for interference measurement.
  • 100 GHz is the center frequency
  • 75 GHz to 120 GHz is frequency-modulated and used.
  • AMC products such as 20 GHz to 40 GHz, 40 GHz to 60 GHz, 50 GHz to 75 GHz, 60 GHz to 90 GHz, 90 GHz to 140 GHz, 140 GHz to 220 GHz are sold, and can be supplied to the above interferometer configuration. It is also possible.
  • the object is obtained by sensing the reflected light by forming the millimeter wave from the light source AMC 104 into a desired beam shape using a resin lens that transmits the millimeter wave, and irradiating the object.
  • the displacement, depth, and height of an object can be measured.
  • the configuration of the interferometer and the phenomenon of interference are the same in principle as the configuration of an interferometer using a normal laser. The operation principle for measuring the height and displacement with millimeter waves for realizing the present embodiment will be described below.
  • a coherent electromagnetic wave oscillation source is used in the displacement measurement due to millimeter wave interference in this embodiment.
  • the millimeter wave has a long coherence distance and is an electromagnetic wave source suitable for interference measurement.
  • the beam supplied from this wave source is supplied to the interferometer shown in FIG. In the interferometer part, it is branched into two by a wire grid polarizer or a polarization beam splitter (PBS) 105.
  • PBS polarization beam splitter
  • the direction of polarization is defined using terms in the optical field. That is, a plane parallel to a plane formed by a normal to the reflection surface and an incident wave incident angle is defined as a P-polarization (P-polarization) plane, and a plane perpendicular to the plane is an S-polarization (S-polarization).
  • the polarization plane from the AMC 104 which is an oscillation source provided with a waveguide and an antenna is P-polarized light
  • the emitted electromagnetic wave enters the beam splitter 105 through the lens.
  • the polarization plane of the reflection surface of the beam splitter 105 is installed in a direction rotated by 45 °.
  • the 45-degree component electromagnetic wave transmitted through the beam splitter 105 is reflected by a reference mirror prepared as the reference surface 108 and returns to the oscillation source side.
  • the other reflected 45 ° electromagnetic wave branched by the beam splitter 105 is reflected by the measurement surface 109 whose height is to be measured, and returns to the oscillation source side.
  • the azimuth angle is changed by 90 ° due to the passage of ⁇ / 2, and the electromagnetic wave whose polarization plane has changed from the incident time is reflected by the beam splitter 105, and a waveguide and an antenna are attached. It reaches the sensor SBD106.
  • the azimuth angle is changed by 90 ° due to the passage of ⁇ / 2, and the electromagnetic wave whose polarization plane has changed from the incident time is not reflected by the beam splitter 105 but is transmitted and reaches the sensor SBD 106.
  • the return electromagnetic waves do not interfere with each other because their 90 ° polarization plane directions are different from each other.
  • a polarization component having a direction of 45 ° is selected with respect to the measurement surface and the reference surface.
  • the antenna and waveguide attached to the sensor SBD 106 have a polarization plane selection function. Therefore, the millimeter wave reflected from the reference surface 109 and the millimeter wave reflected from the measurement surface cause interference. If it is installed in the direction of S-polarization so that the plane of polarization is aligned with the angle direction, an interference waveform from both reflected waves can be obtained.
  • the combination of the antenna and the waveguide attached to the sensor SBD 106 has polarization selectivity, it is different from the case of using visible light or infrared light and does not require an external polarizing element.
  • the displacement information of the position of the measurement surface 108 has a measurement scale based on the wavelength of the millimeter wave used for the measurement. That is, as shown in FIG. 2B, the relative displacement difference between the reference surface 109 and the measurement surface 108 is measured.
  • I (r) The intensity I (r) of the interference wave that can be measured with the interferometer is shown in the equation.
  • I (r) Is + Ir + 2 ⁇ ⁇ (Ir + Is ⁇ COS ( ⁇ s ⁇ r))
  • Is intensity of measurement light
  • Ir intensity of reference light
  • ⁇ s phase of measurement light
  • ⁇ r phase of reference light
  • the interference waveform has a period of ⁇ / 2 of the light source wavelength, when there is a phase difference exceeding the phase difference ⁇ / 2, the interference wave is a repetitive waveform so that the displacement from the reference plane is recognized. It is necessary to measure the displacement by counting the number of interference waves with the phase difference at the same time as the reference plane as the origin. Also, with this method, if the reference surface and measurement surface are displaced due to environmental changes, the reference surface must always be re-recognized, that is, an operation approximated to the origin registration operation called calibration is required. And the operation is complicated. Therefore, when a multi-pixel interferometer is realized for industrial use, it is inconvenient.
  • the measurement frequency of the above example is kept constant and the measurement is based on the physical position difference from the reference surface or reference surface, the measured value can be obtained when the reference surface position information is lost. Absent. Therefore, it is necessary to always hold the reference plane information, and if the information is missing, it is necessary to collect it again, which is inconvenient to measure.
  • This method is a method called time domain (TD) -OCT, and has drawbacks such as low speed and origin registration.
  • TD time domain
  • a countermeasure a method has been devised in which the displacement between the interference surfaces is determined by changing the frequency of the electromagnetic wave for measurement and measuring the change in frequency of the interference signal.
  • SD Spectral Domain
  • SS Send-Source
  • this SS-OCT method is adopted, and a method for calculating the distance is devised as described below.
  • FIG. 3 shows a principle configuration of SS-OCT distance calculation using the millimeter wave of this embodiment.
  • the interference wave when the interference wave is obtained by changing the frequency of the light source, the incident wave and the reflected wave are generated between the reference surface (upper surface in the drawing) 301 and the measurement surface (lower surface in the drawing) 302.
  • the interference waves strengthen each other, so that the interference waves have the maximum amplitude.
  • the peaks and valleys of the reflected wave from the upper surface and the reflected wave from the lower surface are exactly the same, the interference waves cancel each other, so that the interference wave has the minimum amplitude.
  • the distance between the upper surface and the lower surface can be calculated by measuring the intensity of the interference wave while changing the frequency.
  • Fig. 4 shows an image representing the difference in the number of gaps and interference fringes in the SS-OCT method. Comparing the case where the gap is narrow and the case where the gap is wide, as indicated by 401 in the upper part of the figure, when the gap is narrow, the frequency of the interference wave expressing light and dark is small, and the interference fringe interval is rough. It can be recognized that as the gap becomes wider as indicated by 402 in the lower stage, the number of the gaps increases and the interference fringe spacing becomes finer.
  • the interference intensity S (k) at this time is obtained by the following equation.
  • S (k) Is (k) + Ir (k) + 2 ⁇ ⁇ ⁇ Is (k) ⁇ Ir (k) ⁇ ⁇ n (an ⁇ cos (k ⁇ Zn + ⁇ (k)) Is (k),
  • a constant lightness level (DC level) of interference intensity, that is, a change component (AC level) of the interference waveform obtained by subtracting Is (k) + Ir (k) indicates the interference intensity. That is, the power spectrum density of only the interference signal has the following relationship.
  • FIG. 5 shows an example of a calculation sequence in the PC 100 that is the calculation unit of the present embodiment.
  • the gap amount is calculated by paying attention to the relationship between the gap amount and the frequency at which the interference signal is maximized.
  • the case is divided from the case where the gap is narrow.
  • the gap may be small if the interference wave does not have a maximum value. Can be assumed.
  • the gap amount is calculated using the interference wave signal values of the f1 frequency and the f2 frequency shown in (b) of the figure (503-508).
  • the maximum value of the interference wave is one (509), and the case where the maximum value is one is divided.
  • the numerical value of the wavelength of the frequency that becomes the maximum value is the gap amount (510, 511).
  • frequencies (wavelengths) of all the maximum values are listed (512), and the least common multiple is calculated (513).
  • FIG. 6 shows a sequence diagram for explaining this determination sequence.
  • the determination sequence 600 in FIG. 6A corresponds to the determination sequence (517) in FIG.
  • the actual measurement state is illustrated.
  • the illumination spot diameter is several mm even when narrowed down, and the vertical step (plate thickness) is the case.
  • the height (thickness) value has displacement data over 2 pixels or more. From this tendency, concave / convex is determined by tracing the change in the maximum frequency. That is, when the measurement surface is above the reference surface, the frequency of the maximum value of the interference wave shifts in a higher direction, but when the measurement surface is below the reference surface, the opposite characteristics are exhibited. From this tendency, it is possible to determine the convex shape or the concave shape by following the change in the maximum frequency.
  • the thickness value is obtained in the convexity determination.
  • This method does not require complicated calculations. Further, the gap amount can be calculated from the characteristics of the interference wave without providing conditions such as setting of the window function.
  • FIG. 7 shows an example in which the phase difference is measured by the interferometer system shown in FIGS. 1 and 2 of the present embodiment.
  • the frequency was varied between 78 GHz and 102 GHz, and the intensity of the interference wave was measured.
  • the maximum value for each frequency was obtained, the values shown in the table below were obtained.
  • the conditions for frequency modulation by the high-frequency signal source have been described as means for changing the oscillation frequency.
  • the wavelength of the laser light emitted from the LD can be changed by changing the injection current.
  • this technology is applied to millimeter wave oscillation, it is necessary to convert visible light or infrared light emitted by visible light LD light into millimeter waves.
  • Nonlinear crystals can be used as parts suitable for such applications. Examples of the nonlinear crystal include KTP (KTiOPO 4 ) and DAST (4-dimethylamino-N-methyl-4-stilbazolium tosylate). Matching according to the frequency of a specific millimeter wave is required from conditions such as the wavelength used, crystal orientation, and phase matching angle, and conditions are set for each crystal.
  • the reference surface (reference surface) is set to the lower surface of the object 120.
  • the reference surface 109 installed in FIG. 2 is not necessary, and the plate thickness can be calculated based on the lower surface of the object 120.
  • the measurement when the defect or foreign matter 111 is present in the inside or bottom of the layer and the foreign matter detection Examples will be described.
  • the measurement of the film thickness of the object 120 is the same as in Example 2 shown in FIG. 8, but when detecting defects due to scattered waves and foreign matter 111 in the film, the reflected light from the surface of the layer is regarded as background noise. Therefore, removal is necessary. Therefore, as shown in (b) of the figure, by adjusting the rotation angle of the ⁇ / 2 plate, the reflected wave from the upper surface of the layer is reduced, and the scattered wave signal from the in-film foreign matter 111 is efficiently generated. It becomes possible to detect with high sensitivity.
  • Example 4 an example in which the surface (upper surface) of a layer by confocal use can be measured with high resolution will be described.
  • a confocal mechanism of optical microscope technology is used.
  • a pinhole plate 112 having a pinhole having a hole diameter of about 0.1 mm is installed in front of the sensor SBD 106, and a measurement surface 108 is installed at a lens conjugate position of this pinhole.
  • a measurement point equivalent to a pinhole of ⁇ 0.1 mm can be installed on the measurement surface 108.
  • the position of the pinhole in front of the sensor SBD 106 is sequentially moved in the plane direction by XY two-dimensional driving, so that the measurement point can be moved sequentially on the measurement surface 108. Then, two-dimensional measurement information can be obtained by arranging desired measurement point information vertically and horizontally. By moving the pinhole plate 112 in the optical axis direction (Z-axis direction) and further moving it in the plane direction and repeating the measurement, the situation in the layer can be measured three-dimensionally with good resolution. That is, according to this embodiment, three-dimensional OCT can be realized by obtaining and acquiring two-dimensional surface information and measuring the height by interference.
  • data indicating the condition of the bottom of the layer can be obtained by installing a pinhole at a conjugate position with the bottom of the layer. Note that when a pinhole is installed and a conjugate relationship is made as in the present embodiment, the lateral resolution is improved, but conversely the measurement range in the vertical direction decreases, so the diameter of the pinhole depends on the requirements. It is necessary to select a shape.
  • an oscillator and a receiver are installed separately and an interference signal is detected.
  • millimeter waves and terawaves which are radio waves, unlike devices in the optical region.
  • One device for transmission and one for reception. Therefore, as a fifth embodiment, an embodiment in which a Schottky barrier diode is configured as a dual function device for transmission and reception will be described.
  • a Schottky barrier diode (SBD) 113 that oscillates radio waves is used for both transmission and reception, but can be used as both functional devices for transmission and reception by changing the bias voltage and current value. It is. For example, since 1 kHz synchronous detection is applied, it is possible to switch between transmission and reception at the detection timing.
  • the oscillation wave from the frequency modulation circuit 117 is applied to the SBD 113, and the radio wave from the SBD 113 provided with a polarizing plate function including a waveguide and an antenna passes through the lens 114, the ⁇ / 2 plate 115, and the lens 116.
  • the radio wave irradiated and reflected on the object 120 for thickness measurement is received by the SBD 113 on the reverse path, and the output is input as a received wave to the signal processing circuit 118 through the signal amplifier, for predetermined signal processing. Is given.
  • the other bias circuits are not shown.
  • the installation angle of the ⁇ / 2 plate 115 installed in the middle of the detection system It is possible to cope with it by adjusting.
  • the dimension measuring apparatus having the configuration of the present embodiment since it also serves as a transmission / reception function device, it can be realized in a small portable type. For example, application to a film thickness inspection device for a coating film on an outer wall that does not transmit light is possible.
  • FIG. 12 illustrates Example 6 using multi-pixel sensing in which receivers (sensors) are arranged on a line.
  • the illumination light for inspection irradiates an illumination wave spread in an elliptical shape in the millimeter wave irradiation region of the thickness measurement object 120 so that it can correspond to a plurality of sensors with a cylindrical lens or the like in the optical path on the way. Since the reflected interference waves are simultaneously received by the plurality of receiver arrays 119 and the outputs can be processed in parallel, the inspection can be performed over a wide area in a short time.
  • each of the divided mirrors of the multi-divided mirror 121 constituting the reference mirror is switched over time.
  • Each mirror position of the multi-partition mirror 121 having the configuration of the present embodiment can be controlled independently.
  • the reflection timing can be controlled by switching these mirrors at high speed, and the information on the measurement target surface 120 can be detected with high resolution. is there. That is, since the reflecting mirror and the object point are in a conjugate relationship and only the reflecting mirror can be detected, it is possible to sense the surface of the object point as surface information by sequentially switching the divided mirrors.
  • the information inside and below the layer can be detected with high resolution.
  • FIG. 14 shows the ratio of the millimeter wave used in the present example through the dielectric material for each frequency.
  • the horizontal axis is the millimeter wave frequency
  • the vertical axis is the relative value of transmittance. Examples of materials include polyester, denim, campus, and leather. It can be seen that the transmittance decreases as the frequency increases. Therefore, when aiming at measurement utilizing the transmission characteristics of a substance, it is a good idea to select a frequency with reference to this graph.
  • FIG. 15 is an enlarged view of the measurement unit.
  • the height measurement method (OCT) using visible light is considered as an application product example.
  • OCT optical coherence tomography
  • the reflected light from the surface is used for interference. It is possible to measure surface irregularities and flatness with high sensitivity without contact.
  • the amount of decrease in film thickness can be calculated from the displacement (AB) in the figure.
  • FIG. 16 illustrates a case where foreign matter in the film, rust and alteration have occurred under the film, and the effect of each example will be described. Also in this case, if the film cannot be permeated, it cannot be grasped that a foreign substance is present and that alteration under the film has occurred. If it is possible to measure the position under the film, as in the case of the previous film thickness measurement, when the change is measured while recognizing the position of the film upper surface and the film lower surface, there is partial variation under the film. If there is a change in the lower side of the film, or if there is a sudden change in the film thickness, it is possible to extract information such as containing foreign substances. Since at least the occurrence of an abnormality can be detected, it is possible to determine the presence of the displacement even before the measurement.
  • the millimeter wave has a length of several millimeters, the outline of the object is not clear, that is, the resolution in the lateral direction is low. For this reason, an object having a small lateral size of 1 mm or less is detected small. That is, the size of a substance (foreign matter) that is k smaller cannot be detected correctly. Although the resolution depends on conditions on the detection side, a large object can be correctly detected from an object size of approximately the wavelength. In the case of application examples such as maintenance of iron bridges and iron pillars, it is assumed that a defect of several mm size becomes a problem rather than a defect of small size. Since the thickness of the coating film is on the order of several hundreds of millimeters, it is expected that the present interferometer can detect defects occurring in the coating film and correctly measure the coating film thickness variation within a few ⁇ m. .
  • FIG. 17 shows the frequency of the millimeter wave and the degree of penetration depth, and the effect of each example will be described. From another data, there is a characteristic that the moisture absorption rate near 100 GHz is low. It can be seen that the use of millimeter waves in this region is effective for internal measurement because of less attenuation in the living body. By using millimeter waves that have a deeper penetration depth than infrared rays, it is possible to expect accurate grasp of the degree of burns.
  • OCT is utilized as an ophthalmic diagnostic apparatus using infrared rays. However, the above-described measurement method and apparatus according to the present invention enables measurement in a deeper region than the present, and performance as an ophthalmic diagnostic instrument. Improvement is expected.
  • this invention is not limited to the above-mentioned Example, Various modifications are included.
  • the above-described embodiments have been described in detail for better understanding of the present invention, and are not necessarily limited to those having all the configurations described.
  • a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment.

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Abstract

Procédé et dispositif de mesure de déplacement permettant de mesurer l'épaisseur d'une substance cible par rapport à un matériau diélectrique qui ne transmet pas la lumière visible, et la hauteur et la profondeur de défauts et de corps étrangers dans la substance. A l'aide des ondes millimétriques et des ondes térahertz formant des ondes de rayonnement se transmettant à travers le matériau diélectrique, par le biais du brouillage des ondes réfléchies par la surface de mesure (108) et des ondes réfléchies par une surface de référence (109), il est possible d'acquérir, avec une grande précision et sans atténuation, des informations sur l'épaisseur, la profondeur et la hauteur des objets à mesurer.
PCT/JP2014/065282 2013-07-04 2014-06-10 Procédé et dispositif de mesure de brouillage WO2015001918A1 (fr)

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Cited By (7)

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WO2017020402A1 (fr) * 2015-08-04 2017-02-09 华讯方舟科技有限公司 Dispositif et procédé de détection de courrier
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WO2020241584A1 (fr) 2019-05-30 2020-12-03 株式会社トプコン Interféromètre optique et procédé d'interférométrie optique
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