Classifications

• • 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
  • G01B11/0691—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of objects while moving
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F7/00—Other details of machines for making continuous webs of paper
  • D21F7/06—Indicating or regulating the thickness of the layer; Signal devices
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
  • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
  • G01S17/06—Systems determining position data of a target
  • G01S17/46—Indirect determination of position data
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
  • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
  • G01S7/499—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00 using polarisation effects
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B2210/00—Aspects not specifically covered by any group under G01B, e.g. of wheel alignment, caliper-like sensors
  • G01B2210/40—Caliper-like sensors
  • G01B2210/44—Caliper-like sensors with detectors on both sides of the object to be measured
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B2210/00—Aspects not specifically covered by any group under G01B, e.g. of wheel alignment, caliper-like sensors
  • G01B2210/50—Using chromatic effects to achieve wavelength-dependent depth resolution
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/55—Specular reflectivity
  • G01N21/57—Measuring gloss

Definitions

• the invention relates to a method for determining the surface of an object being measured and a method for determining the thickness of an object being measured.
• the invention relates to a measuring device for determining the surface of an object being measured and a measuring device for determining the thickness of an object being measured.
• the thickness of paper is measured from a moving paper web.
• solutions can be used, in which the sensor of the measuring device touches the surface of the paper, or solutions in which the sensor does not touch the surface. Solutions that do not touch the surface include capacitive measurements and optical measurements. The contact of the sensor on the surface being measured may cause surface errors and, therefore, solutions in which the sensor touches the surface of the object being measured are avoided.
• Optical measurements utilise chromatic aberration in determining the surface being measured.
• light is focused on the surface through an optical element whose focal distance is in a known manner dependent on the wavelength of light.
• Light reflected from the surface is collected coaxially to a detector with the same optical element.
• the detector which may be a spectrum analyser, analyses the spectrum of the reflected light.
• the wavelength with which the surface is best in focus is also reflected the most efficiently, and it represents the highest intensity in the spectrum. Because on the basis of the dimensioning of the measuring device, the location of the focal point of this wavelength is known, it helps define the location of the surface. If the surface is determined on both sides of the paper, it is also possible to measure the thickness of the object.
• the measuring device comprises an optical source; an optical radiation processing unit arranged to direct different wavelengths of the optical radiation of the optical source to the object being measured from a direction differing from the normal of the surface being measured in such a manner that the different wavelengths focus on different heights in the direction of the normal of the surface being measured; a detector to which the optical radiation processing unit is arranged to direct the optical radiation that the optical radiation processing unit is arranged to receive from the object being measured at least from the direction of specular reflection that differs from the normal of the surface being measured; a signal processing unit arranged to determine from the detected optical radiation on the basis of the signal provided by the detector the wavelength on which the intensity of the optical radiation is the highest and to determine the location of the surface being measured using the determined wavelength.
• the invention also relates to a measuring device for measuring the thickness of an object being measured.
• the measuring device comprises an optical source; an optical radiation processing unit arranged to direct different wavelengths of the optical radiation of the optical source to the object being measured from a direction differing from the normal of the surface being measured in such a manner that the different wavelengths focus on different heights in the direction of the normal of the surface being measured; a detector to which the optical radiation processing unit is arranged to direct the optical radiation that the radiation processing unit is arranged to receive from the object being measured at least from the direction of specular reflection that differs from the normal of the surface being measured; and a signal processing unit is arranged to determine from the detected optical radiation on the basis of the signal provided by the detector the wavelength on which the intensity of the optical radia- tion is the highest and to determine the location of the surface being measured using the determined wavelength; and for measuring a second side of the object being measured, the measuring device comprises: a second-side optical source; a second-side optical radiation processing unit arranged
• the invention further relates to a method for determining the surface of an object being measured by means of optical radiation.
• the method comprises directing different wavelengths of optical radiation to the object being measured from a direction differing from the normal of the surface being measured in such a manner that the different wavelengths focus on different heights in the direction of the normal of the surface being measured; receiving optical radiation at least from the direction of specular reflection that differs from the normal of the surface being measured; determining from the received optical radiation the wavelength on which the intensity of the received optical radiation is the highest; and determining the location of the surface of the object being measured by means of the determined wavelength.
• the invention also relates to a method for measuring the thickness of an object being measured by using optical radiation.
• the method comprises directing different wavelengths of optical radiation to the object being measured from a direction differing from the normal of a first surface being measured in such a manner that the different wavelengths focus on different heights in the direction of the normal of the first surface being measured; receiving optical radiation at least from the direction of specular reflection that differs from the nor- mal of the first surface being measured; determining from the received optical radiation the wavelength on which the intensity of the received optical radiation is the highest; and determining the location of the first surface being measured by means of the determined wavelength; directing different wavelengths of optical radiation to the object being measured from a direction differing from the normal of a second surface being measured in such a manner that the different wavelengths focus on different heights in the direction of the normal of the second surface being measured; receiving optical radiation at least from the direction of specular reflection that differs from the normal of the second surface being measured; determining from the received optical radiation the wavelength on which the intensity of the optical radiation is the
• the methods and measuring devices of the invention provide several advantages. It is possible to reduce the diffuse reflection coming from inside the object being measured, which disturbs the measurement. The surface and thickness of an object being measured can thus be determined accurately regardless of the diffuse reflection.
• Figure 2 shows a measuring device whose detector receives undis- persed optical radiation
• Figure 3 shows a measuring device with a reflector
• Figure 4 shows an optical radiation processing part
• Figure 5 shows an optical radiation processing part
• Figure 6 shows the normalization of a measurement
• Figure 7 shows the measurement of the thickness of an object
• Figure 8 shows spectrum detection by means of a beam splitter, two different filters, and two detectors
• Figure 9 shows filter permeability
• Figure 10 shows a detected spectrum
• Figure 11 is an example of the modulation of optical radiation
• Figure 12 shows measurement using a focal point line system
• Figure 13 is a flow chart of a surface determination method
• Figure 14 is a flow chart of a thickness measurement method.
• Diffuse materials include paper, textiles, metal coated with a diffuse material, skin, various powders whose surface (or thickness) needs to be determined.
• a measuring device comprises a transmitter part 100 and receiver part 102 that are separate from each other.
• the transmitter part 100 comprises an optical source 104 and a first optical radiation processing part 106.
• optical radiation refers to electromagnetic radiation whose wavelength band is between ultraviolet radiation (wavelength approximately 50 nm) and infrared radiation (wavelength approximately 1 mm).
• the receiver part 102 comprises a detector 108 and a second optical radiation processing part 110.
• the optical radiation processing parts 106 and 110 form an optical radiation processing unit 112 in which the optical radiation processing part 106 directs different wavelengths of optical radiation coming from the optical source to an object 114 being measured from a direction differing from the normal 118 of a surface 116 being measured in such a manner that the different wavelengths are directed to (focused on) different heights in the direction of the normal 118 of the surface 116 being measured. Even though the surface was rough, as it often is, normal refers to a mean normal direction obtained for instance by averaging a large number of representative normals. Some of the wavelengths may focus above the object 114 being measured and some inside it.
• the optical radiation can be dispersed into separate wavelengths by means of a prism or grid in the optical radiation processing part 106. Directing can in turn be done using one or more lenses or mirrors to focus different wavelengths on different focal points 126.
• the measuring device comprises at least one polarizer 120, 122. Because it is possible to work with just one polarizer, the polarizer 122 of the transmitter part 100 is not necessarily needed and polarizer 120 can be used to polarize the optical radiation reflected from the object 114 being measured perpendicular to the normal 118 of the surface 116 being measured. The vibration of the electric field of optical radiation then has a perpendicular component in relation to the normal 118 of the surface 116. When several polarizers are used, the polarization directions of all polarizers are the same. One or more polarizers attenuate the optical radiation coming from inside the object 114 being measured, because inside the object 114 being measured polarization weakens or disappears. Optical radiation reflected from a surface is polarized or maintains its polarization.
• reflection refers to specular reflection and diffuse reflection in which reflection may take place from a smooth or rough surface.
• reflection also refers herein to scattering, refracting and reflecting radiation from inside the object being measured.
• optical radiation can be directed to a surface and received at a Brewster angle, whereby the optical radiation is most effectively polarized as it is reflected from the surface.
• the optical radiation processing part 110 of the optical radiation processing unit 112 can focus received polarized optical radiation to a detector 118 by means of one or more lenses or mirrors.
• the optical radiation processing part 110 and detector 108 are directed and the numerical aperture of the optical radiation processing part 110 and detector 108 is dimensioned in such a manner that polarized optical radiation can be received at least from the direction of specular reflection from the object 114 being measured.
• the focal points of the different wavelengths of dispersed optical radiation are in parallel on the detector 108. For this reason, the different wavelengths in the solution of Figure 1 can be detected with a line detector, for example. Thus, each wavelength is directed to one detector element of the line detector.
• An electric signal generated by the detector 108 from optical radiation can be fed to a signal processing unit 124 that can define from the received optical radiation the wavelength on which the intensity of the received optical radiation is the highest.
• the signal processing unit 124 can determine the location of the surface 116 of the object 114 being measured using the determined wavelength. The definition of the surface 116 being measured is based on knowing in advance at which distance each wavelength is focused, and assuming that the wavelength that is reflected from the focal point is the strongest.
• Figure 2 shows a solution, in which a second optical radiation processing part 110 also comprises a dispersive component, such as a prism or grid, with which the wavelengths of optical radiation propagating along different routes can be assembled. Different wavelengths then arrive at the same focal point at the detector 108, and the detector 108 can be just one element.
• a dispersive component such as a prism or grid
• Figure 3 shows a solution in which a measuring device comprises an optical radiation processing unit 112 with a common transmitter part 100 and receiver part 102.
• a measuring device comprises an optical radiation processing unit 112 with a common transmitter part 100 and receiver part 102.
• the propagation of optical radiation from the optical source 104 to the object 114 being measured and on to the optical radiation processing part 110 takes place in the same manner as in the case of Figure 2.
• the optical radiation reflected once from the object 114 being measured does not, however, propagate directly to the detector 108, but the measuring device comprises a reflector 300 that reflects the optical radiation reflected from the object 114 being measured back to the object 114 being measured to reflect on from the object 114 being measured via a second optical radiation processing part 110 towards the first optical radiation processing part 106 and on towards the optical source 104.
• the measuring device comprises a beam splitter 302 that directs at least part of the optical radiation directed towards the optical source 104 to the detector 108.
• the beam splitter 302 can be a polarizing beam splitter, in which case the beam splitter 302 also polarizes the optical radiation directed to the object 114 being measured and no separate polarizers 120, 122 are required.
• the beam splitter 302 can then also direct all polarized optical radiation from the reception direction to the detector 108.
• the beam splitter 302 may be based on solely distributing the optical power in a desired ratio, whereby separate optical beams usually obtain the same power. In such a case, either of the separate polarizers 120, 122 is needed.
• Figure 4 shows an optical radiation processing part 106.
• the first optical radiation processing part 106 may comprise a chromatically dispersive component 400 that is arranged to disperse non-axially the optical radiation directed to the object 114 being measured.
• Optical radiation is thus dispersed with the dispersive component 400 in a direction differing from the optical axis 402 of the first optical radiation processing part 106, whereby the dispersion, that is, the distribution of the wavelengths, is at least partly directed in the direction of the normal 118 of the surface 116 being measured.
• the direction of the focal points does not need to be parallel to the normal 118 of the surface 116, but the directions have a common vector component (i.e. the focal points are not horizontal nor on an optical axis).
• the dispersive component 400 is located between two focusing lenses 404, 406.
• the lenses 404, 406 form a focusing component 408. Radiation coming from the optical source 104 between the lenses can be colli- mated.
• the dispersive component 400 together with the focusing component 408 may focus the different wavelengths of the optical radiation of the optical source 104 on different heights in the direction of the normal 118 of the surface 116 being measured.
• the dispersing component 400 may be a prism or grid, and instead of lenses or in addition to them, focusing mirrors can be used. Both lenses 404, 406 can be replaced with a lens combination, mirror, mirror combination, or a combination of all these.
• Figure 5 shows an optical radiation processing part 110.
• Optical radiation reflected from the object 114 being measured can be focused on the detector 108 with the focusing component 508 that comprises lenses 504, 506.
• the focal point of the second optical radiation processing part 110 can be on the surface 116 being measured or near it. Without the dispersive component 500, the depth of field should be sufficiently good around the focal point.
• the optical radiation processing part 110 may also comprise a dispersive component 500 that removes dispersion and enables the combination of wavelengths propagated along different optical paths to the same focus.
• the focal points in front of the second optical radiation processing part 110 can be at the same points as those to which the first optical radiation processing part 106 focuses different wavelengths (see Figure 1 , for example).
• the reflection from the surface 116 being measured is then effective.
• the dispersed wavelengths focus behind the second optical radiation processing part 110 at the same focal point, for instance at the detector 108, and the detection can be done with one detector element.
• first 106 and second 110 optical radiation processing parts may be alike, but the strengths and dispersive component 400 of the lenses 404, 406 may also differ from each other.
• the second optical radiation processing part 110 may comprise a second dispersive component 500 that removes dispersion from the optical radiation reflected from the object 114 being measured.
• the second optical radia- tion processing part 110 can focus the optical radiation in an undispersed form to the detector 108.
• the detector 108 may be a line detector and a different wavelength of undispersed optical radiation is directed to each of its elements.
• a single wavelength refers to a narrow wavelength band that is only part of the measuring band.
• a narrow band can be for instance a band that is less than one fifth of the entire measuring band. Often a narrow band is only a nanometre or dozens of nanometres wide.
• a narrow band may be defined on the basis of the desired measuring accuracy, or it may be determined by the measuring accuracy of the measuring devices and components.
• the reflector may reflect optical radiation back to the object 114 being measured through the optical radiation processing part 110.
• the second optical radiation processing part 110 may then focus different wavelengths of optical radiation on different heights in the direction of the normal 118 of the surface 116 being measured.
• both optical radiation processing parts 106 and 110 comprise dispersive components 400 and 500, undispersed optical radiation is directed to the detector 108.
• Figure 6 shows the measurement of a reference. Since the intensities of the different wavelengths of the source 104 are not evenly distributed and different wavelengths may have a different intensity, the intensity distribution of the source 104 may be measured as a function of the wavelength.
• a reference beam splitter 600 that directs part of the optical radiation emitted by the source 104 to a reference detector 602 that transforms the received optical radiation into an electric signal.
• the beam splitter 600 may also be part of the optical radiation processing part 106.
• the signal processing unit 124 receives the electric signal.
• the signal processing unit 124 may normalize the measurement made by the detector 108 with the measurement made by the reference detector 602. Normalization may mean, for instance, the division of the intensities obtained with the detector 108 by the intensities measured by the reference detector 602.
• the reference beam splitter 600 can be the same as the directional beam splitter 302 in Figure 3.
• the directional beam splitter 302 may also act as the reference beam splitter 600.
• Figure 6 also shows an embodiment with which it is possible to compensate for the colour of the object 114 being measured, or generally the reflection response of the object 114 being measured.
• An optical unit 604 may direct optical radiation produced by the source 104 in an undispersed form to the object 114 being measured, and optical radiation reflected therefrom can be received with another optical unit 606 that comprises a detector.
• the optical unit 606 may form a spectrum of the reflected radiation which the signal processing unit 124 may measure.
• the optical unit 606 may feed an electric signal of the measurement to the signal processing unit 124 and the unit 124 may normalize the measuring result obtained with the detector 108 with at least one of the following: the measuring result of the reference detector 124, the measuring result of the optical unit 606.
• Figure 7 shows an embodiment in which both surfaces 116, 116B of the object being measured are measured in the manner described above.
• the optical source then directs optical radiation through the optical radiation processing part 106 to the object 114 being measured in such a manner that the different wavelengths focus at different distances in the direction of the normal 118 of the surface 116 being measured.
• Optical radiation is reflected from the object 114 being measured to the optical radiation processing part 110 through the polarizer 120, for instance. It is also possible to use both polarizers 120, 122.
• the optical radiation processing part 110 directs the reflected optical radiation to the detector 108.
• the detector 108 feeds the measuring signal to the signal processing unit 124 for surface determination.
• the intensity distribution of the optical source 104 in relation to the wavelengths can be measured using the beam splitter 600, reference detector 602, and signal processing unit 124.
• the beam splitter 600 can be a polarizer.
• the second surface 116B of the object 114 being measured can be determined by focusing different wavelengths generated by the optical source 104B and optical radiation processing unit 106B at different distances in the direction of the normal 118B of the surface 116B being measured.
• Optical radiation is reflected from the object 114 being measured to the optical radiation processing part 110B through the polarizer 120B, for instance. It is also possible to use both polarizers 120B, 122B.
• the optical radiation processing part 110 directs the reflected optical radiation to the detector 108B.
• the detector 108 feeds the measuring signal to the signal processing unit 124 for surface determination.
• the intensity distribution of the optical source 104B in relation to the wavelengths can be measured using the beam splitter 600B, reference detector 602B, and signal processing unit 124.
• the beam splitter 600B can be a polarizer.
• Each block 104B to 110B, 120B, 122B, 600B, 602B below the object being measured is the same as blocks depicted by reference numbers 104 to 110, 120, 122, 600, 602 in Figures 1 to 6.
• blocks 104 to 110, 120, 122, 600, 602 in Figure 7 are also similar to those in the previous figures, but the top measuring part in Figure 7 need not be the same as the bottom measuring part.
• Figure 8 shows detecting by means of two detector parts.
• the detector 108 may comprise a detector beam splitter 800 that distributes at a known ratio the optical radiation it receives from the object 114 being measured to two detector parts 802 and 804.
• Filters 806, 808 are located in front of the detector parts 800, 802 to filter the radiation arriving at the detectors as shown in Figure 9.
• the solution can also be applied to the reference detector 602.
• Figure 9 shows pass curves of filters in relation to the wavelength.
• the vertical axis shows the intensity I and the horizontal axis shows the wavelength ⁇ .
• Curve 900 shows the response of filter 806 in relation to the wavelength and curve 902 the response of filter 808 in relation to the wavelength.
• Filter 806 may pass less on a short wavelength than on a long wavelength and conversely, filter 808 may pass less on a long wavelength than on a short one, and the curves may be linear.
• the response of filter 806 is in general different from that of filter 808 on the band used in measurement.
• Figure 10 shows a measured spectrum showing intensity I as a function of wavelength ⁇ .
• Dependency on the wavelength ⁇ ma ⁇ of the highest intensity can also be nonlinear, but for determining the location of the surface, it is sufficient that the dependency is known.
• Figure 11 shows an example of modulating optical radiation.
• Optical radiation emitted by the source 104 can be modulated. Modulation can be performed with a mechanical, electro-optical, magneto-optical, or acousto-optical chopper/modulator, or the modulation can be done electronically (in a diode, for instance).
• the modulation may be time-divided, whereby the optical source 104 emits optical pulses regularly, pseudo-randomly or randomly.
• Regular pulsing may mean repetitive, regular transmission of a predefined pulse pattern 1100, or at its simplest the transmission of pulses at a desired frequency.
• the interval between the pulses of a predefined pulse pattern may be regular or irregular.
• the signal processing unit 124 may control modulation and correspondingly and in a synchronized manner demodulate the signal arriving from the detector 108.
• modulation When using modulation, the impact of interference to the measurement is reduced.
• modulation may be beneficial when measuring an object 114 on both its sides. It is then possible to direct optical radiation to different sides of the object 114 being measured at different times or use a different modulation. This way, the optical radiation from the opposite side does not disturb the measurement.
• Figure 12 shows an embodiment in which the optical radiation processing part 106 together with the focusing optical components 404, 406 and dispersive component 400 can form, instead of focal points, a focal point line system 1200 in which each wavelength is focused on its own line.
• the source is then a dotted or linear source.
• the optical radiation processing part 110 may comprise optical components 504, 506, and a dispersive component 500 that divide the focal point line system 1200 in the direction of the normal of the surface 116 being measured.
• Each wavelength used in the measurement can be directed to the object 114 being measured simultaneously or at different times.
• the wavelengths can be directed to the object 114 being measured in small groups (or bands) or one wavelength at a time.
• Each wavelength or wavelength band can be formed using suitable, replaceable or adjustable filters, or the band of the optical source can be swept over the measuring band.
• a led band may be 20 nm and it can be swept over the measuring band that may be 500 to 650 nm.
• the monochromatic wavelength of a laser can also be swept over dozens or hundreds of nanometers, for instance.
• the optical source 104 may comprise an incandescent lamp, gas-discharge lamp, halogen lamp, led, or a laser with adjustable wavelength, etc.
• the optical source 104 may also comprise an optical fibre, in which case the actual unit generating the optical radiation may be far from the optical radiation processing unit 106 and the object 114 being measured.
• the detector 108 may in turn comprise any device forming a spectrum, for instance a spectrograph.
• the detector may also comprise a PIN diode, APD (avalanche photodiode), LDR (light dependent resistor), photomultiplier tube, CCD (charge coupled device) cell, CMOS (complementary metal oxide semiconductor) cell, pyrodetector, or the like.
• the detector 108 may also comprise a fibre with which optical radiation can be transferred to the actual detecting unit.
• Figure 13 shows a flow chart of a method of determining the surface of an object being measured.
• different wavelengths of optical radiation are directed to an object 114 being measured from a direction differing from the normal 118 of a surface 116 being measured in such a manner that the different wavelengths focus on different heights in the direction of the normal 118 of the surface 116 being measured.
• optical radiation reflected from the object 114 being measured can be polarized to a direction perpendicular to the normal 118 of the surface 116 being measured.
• polarized optical radiation is received at least from the direction of specular reflection that differs from the normal 118 of the surface 116 being measured.
• the wavelength on which the intensity of the received optical radiation is the highest is determined from the received optical radiation.
• the location of the surface 116 of the object 114 being measured is determined by means of the determined wavelength.
• Figure 14 shows a flow chart of a method of determining the thickness of an object being measured.
• step 1400 different wavelengths of optical radiation are directed to an object 114 being measured from a direction differing from the normal 118 of a first surface 116 being measured in such a manner that the different wavelengths focus on different heights in the direction of the normal 118 of the surface 116 being measured.
• step 1402 optical radiation reflected from the object 114 being measured can be polarized to a direction perpendicular to the normal 118 of the first surface 116 being measured.
• step 1304 polarized optical radiation is received at least from the direction of specular reflection that differs from the normal 118 of the first surface 116 being measured.
• step 1406 the wavelength on which the intensity of the received optical radiation is the highest is determined from the received optical radiation.
• step 1408 the location of the surface 116 being measured is determined by means of the determined wavelength.
• step 1410 the different wavelengths of optical radiation are directed to the object 114 being measured from a direction differing from the normal 118B of a second surface 116B being measured in such a manner that the different wavelengths are directed to different heights in the direction of the normal 118B of the second surface 116B being measured.
• step 1412 optical radiation reflected from the object 114 being measured can be polarized to a direction perpendicular to the normal 118B of the second surface 116B being measured.
• step 1414 polarized optical radiation is received at least from the direction of specular reflection that differs from the normal 118B of the second surface 116B being measured.
• step 1416 the wavelength on which the intensity of the received optical radiation is the highest is determined from the received optical radiation.
• step 1418 the location of the second surface 116B being measured is determined by means of the determined wavelength.
• step 1420 the thickness of the object 114 being measured is determined by means of the determined locations of the surfaces 116, 116B.

Landscapes

• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• General Physics & Mathematics (AREA)
• Computer Networks & Wireless Communication (AREA)
• Radar, Positioning & Navigation (AREA)
• Remote Sensing (AREA)
• Electromagnetism (AREA)
• Length Measuring Devices By Optical Means (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (1)

Family

ID=37232275

Family Applications (1)

Country Status (7)

Cited By (6)

Families Citing this family (33)

Citations (6)

Family Cites Families (23)

• 2006
  • 2006-10-18 FI FI20065669A patent/FI119259B/fi active IP Right Grant
• 2007
  • 2007-10-17 CN CN2007800386293A patent/CN101529200B/zh active Active
  • 2007-10-17 WO PCT/FI2007/050561 patent/WO2008046966A1/en not_active Ceased
  • 2007-10-17 EP EP07823198A patent/EP2076733B1/en active Active
  • 2007-10-17 JP JP2009532834A patent/JP5155325B2/ja active Active
  • 2007-10-17 ES ES07823198T patent/ES2400380T3/es active Active
  • 2007-10-17 US US12/446,298 patent/US7936464B2/en active Active

Patent Citations (6)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events