(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2011/0080576A1
`Thiel et al.
`(43) Pub. Date:
`Apr. 7, 2011
`
`US 2011 0080576A1
`
`(54) DEVICE AND METHOD FOR OPTICAL 3D
`MEASUREMENT AND FOR COLOR
`MEASUREMENT
`
`(75) Inventors:
`
`Frank Thiel, Ober-Ramstadt (DE):
`Peter Fornoff, Reichelsheim (DE)
`
`(73) Assignee:
`
`SE DENTAL SYSTEMS
`
`(21) Appl. No.:
`
`12/896.435
`9
`
`(22) Filed:
`
`Oct. 1, 2010
`
`Related U.S. Application Data
`(63) Continuation of application No. PCT/EP2009/
`053912, filed on Apr. 2, 2009.
`
`(30)
`
`Foreign Application Priority Data
`
`Apr. 3, 2008 (DE) ...................... 10 2008 O17481.5
`Publication Classification
`
`(51) Int. Cl
`(2006.01)
`GOIN 2L/00
`(52) U.S. Cl. .......................................................... 356/73
`(57)
`ABSTRACT
`
`The invention relates to a device and a method for optical 3D
`measurement, wherein said device can be switched between a
`first mode for optical 3D measurement using a chromatic
`confocal measurement method or the triangulation measure
`ment method and a second mode for colorimetric measure
`ment. In the first mode, a broad-band illuminating beam is
`focused onto a first plane and in the second mode the broad
`band illuminating beam is focused onto a second plane other
`than the first plane at a distanced from the surface of the
`object to be measured.
`
`
`
`33
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`Align Ex. 1013
`U.S. Patent No. 9,962,244
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`US 2011/0080576 A1
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`Apr. 7, 2011
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`DEVICE AND METHOD FOR OPTICAL 3D
`MEASUREMENT AND FOR COLOR
`MEASUREMENT
`
`CROSS REFERENCE TO RELATED
`APPLICATIONS
`0001. This application is a continuation of International
`Application No. PCT/EP2009/053912, filed Apr. 2, 2009, and
`claims priority to German Patent Application No.
`102008017481.5, filed Apr. 3, 2008, each of which is incor
`porated by reference herein in its entirety, as if set forth fully
`herein.
`
`TECHNICAL FIELD
`0002. The invention relates to a device and method for
`optical 3D measurement and for color measurement.
`
`PRIOR ART
`0003) A number of devices for optical 3D measurement
`are known in the prior art. The devices are often based on
`optical measuring methods such as the chromatic confocal
`measuring method or the triangulation measuring method.
`0004 Furthermore, devices used for colorimetric mea
`surement are known in the prior art. In the method for color
`measurement, the object to be measured is illuminated by a
`light beam having a spectrum similar to daylight and the
`reflected light beam is detected by means of a color sensor
`such as a CCD camera or a spectrometer and analyzed spec
`trally. The color of the object to be measured can then be
`determined from this spectrum. In dentistry, color measure
`ment is used in order to ensure that the dental prosthetic items
`match the adjacent natural teeth in terms of color.
`0005. A disadvantage of such devices is that they are either
`suitable only for 3D measurement or only for color measure
`ment. Information obtained from 3D measurement and from
`color measurement is required, particularly in dentistry, for
`designing a dental prosthetic item. Therefore, this informa
`tion is acquired laboriously firstly by means of known devices
`for 3D measurement and secondly by means of known
`devices for color measurement, the two processes being car
`ried out independently of each other.
`0006. It is thus an object of this invention to provide a
`device that makes it possible to carry out both 3D measure
`ment and color measurement of an object to be measured in a
`simple manner.
`
`SUMMARY OF THE INVENTION
`0007. This object is achieved by the present invention.
`0008 According to the invention, a device for optical 3D
`measurement comprises an objective, which device can be
`switched between a first mode for optical 3D measurement
`using the chromatic confocal measuring method, the triangu
`lation measuring method, or any other measuring method and
`a second mode for color measurement in that a broad-band
`illuminating beam can be focused by means of the objective
`onto a first plane of the surface of an object to be measured in
`the first mode, and the broad-band illuminating beam can be
`focused by means of the objective onto a second plane other
`than the first plane at a distanced from the surface of the
`object to be measured in the second mode.
`0009. In 3D measurement, the surface information of an
`object to be measured can be detected using different mea
`Suring methods such as the chromatic confocal measuring
`
`method or the triangulation measuring method. A broad-band
`illuminating beam is directed toward the object to be mea
`sured and the reflected light in the form of a monitoring beam
`is then analyzed.
`0010. In the chromatic confocal measuring method, a
`polychromatic illuminating beam is focused onto the Surface
`of an object to be measured. In optical refraction, the angle of
`refraction is dependent on the wavelength of the refracted
`light so that light of shorter wavelengths is focused to a focal
`point located closer to the objective and light of longer wave
`lengths is focused to a focal point located at a greater distance
`from the objective. A narrow spectral range of the illuminat
`ing beam is focused exactly onto the first plane of the Surface
`of the object to be measured, and the remaining spectral
`ranges only form out-of-focus images in the form of fuZZy
`circles on the object to be measured. The reflected illuminat
`ing beam forms a monitoring beam that is deflected by a beam
`splitter toward the color sensor. Due to the presence of a
`diaphragm disposed confocally between the beam splitter and
`the color sensor, the spectral range of the monitoring beam
`reflected by the object to be measured passes through the
`diaphragm, and the remaining spectral ranges forming out
`of-focus images on the Surface of the object to be measured
`are filtered out. The wavelength of the focused spectral range
`can be determined by means of spectral analysis, and the
`absolute position of the object to be measured in the direction
`of the illuminating beam is derived therefrom.
`0011. In the triangulation measuring method, the illumi
`nating beam is projected onto the object to be measured. The
`reflected monitoring beam is then detected by means of an
`image sensor Such as a CCD camera. The distance from the
`object to be measured can be determined from the position
`and direction of the illuminating beam and the monitoring
`beam by the use of trigonometric methods of calculation. In
`this measuring method, the monitoring beam is detected in an
`unfiltered form by the color sensor so that there is no need for
`a confocally disposed diaphragm.
`0012. The white-light interferometry measuring method
`utilizes the interference of a broad-band light such as that of
`white light. This measuring method compares the delay time
`of the monitoring beam reflected by the object to be measured
`by means of an interferometer, such as a Michelson interfer
`ometer, with the delay time of the illuminating beam having a
`known optical path length as reference. The interference of
`the two light beams results in a pattern from which the relative
`optical path length can be derived.
`0013. In the deflectometry measuring method, the image
`of a light pattern, such as that of a grid, is observed in the
`reflection across the surface of the object to be measured. The
`local gradients of the surface can be determined from the
`deformation of the grid image, and the 3D information of the
`object to be measured can be produced from the local gradi
`ents. A broad-band light beam can also be used for this pur
`pose.
`0014. In the aforementioned methods for optical 3D mea
`Surement, the broad-band monitoring beam scans the object
`to be measured within a measuring area in order to produce
`the Surface information concerning this measuring area. The
`broad-band illuminating beam has a spectrum that advanta
`geously includes the visible spectral range of from 400 nm to
`800 nm. The illuminating beam can represent one or more
`point light beams, one or more stripes of light or any other
`light pattern.
`
`0007
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`US 2011/0080576 A1
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`Apr. 7, 2011
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`0015. In methods employed for color measurement, a
`polychromatic illuminating beam is often deflected toward
`the object to be measured, the spectrum of which is similar to
`the daylight spectrum and which has a color temperature
`ranging from 5000 K to 6000 K. The reflected monitoring
`beam is then analyzed spectrally by means of a color sensor
`Such as a CCD camera or a spectrometer. The color impres
`sion for the human eye can be inferred from the spectrum
`detected, and a color can be assigned to the object being
`measured.
`0016. In the first mode, the illuminating beam is focused
`Such that light of at least one wavelength of the polychromatic
`illuminating beam has its focal point in the first plane of the
`surface of the object to be measured, and the surface of the
`object to be measured is thus reproduced sharply on the color
`sensor for this wavelength. The focal points for the remaining
`wavelengths of the polychromatic illuminating beam are
`located either above or below the first plane of the surface of
`the object to be measured so that the light of these wave
`lengths forms an out-of-focus image on the color sensor. In
`the second mode, the illuminating beam is focused onto a
`second plane other than the first plane of the surface of the
`object to be measured and it thus forms an out-of-focus image
`on the surface. The broad-band illuminating beam is thus not
`bundled to a point but to a fuzzy circle having a wide diameter
`both in the event that the focal point is located above the first
`plane of the surface of the object to be measured and in the
`event that the focal point is located below the first plane of the
`surface of the object to be measured. The illuminating beam
`is reflected by the surface of the object to be measured within
`the fuzzy circle in the form of a monitoring beam and can be
`used for color measurement.
`0017. The focal length of the first objective is adjusted in
`the first mode such that the focal point for one wavelength is
`located in the first plane of the surface of the object to be
`measured. In the second mode, the focal point is adjusted Such
`that the focal point for all wavelengths is located other than
`the first plane of the surface of the object to be measured. For
`the purpose of Switching the device between the first mode
`and the second mode, it is thus not necessary to replace the
`optical system but merely to carry out an adjustment of its
`focal length. The adjustment of the focal length is often
`effected by rotating an adjusting means of the objective that
`adjusts interior mechanics of the objective in order to alter the
`focallength. The adjustment of the focal length can be motor
`controlled or can alternatively be carried out manually by a
`user. In the chromatic confocal measuring method, a confocal
`diaphragm is mounted in front of the color sensor in order to
`transmit exclusively the light of the spectral range that is
`focused onto the surface of the object to be measured. If this
`measuring method is used in the first mode, the diaphragm is
`revolved out of the optical path of the monitoring beam when
`switching the device from the first mode to the second mode
`in order to make it possible to carry out a complete spectral
`analysis of the monitoring beam.
`0018. An advantage is that both 3D measurement and
`color measurement can be carried out by means of the device
`of the invention. The same light Source emitting abroad-band
`illuminating beam and the same color sensor are used for both
`modes. In dentistry, in particular, the 3D measurement and
`color measurement of teeth for the purpose of designing
`dental prosthetic items is made possible by the use of a single
`device of the invention.
`
`0019. A further advantage is that the cost burden and the
`space required are reduced by combining a device used for
`color measurement and a device used for 3D measurement to
`give the device of the invention, which is operable in both
`modes.
`0020 Advantageously, a diaphragm can be revolved into
`the optical path of a monitoring beam Such that the diaphragm
`is confocal to the surface of the object to be measured when
`using the chromatic confocal measuring method in the first
`mode. The diaphragm can be revolved out of the optical path
`of the monitoring beam in the second mode.
`0021. The diaphragm can be mounted for rotation about an
`axis in order to be revolved laterally relatively to the optical
`path. The diaphragm is disposed confocally in the first mode
`when using the chromatic confocal measuring method in
`order to filter out the spectral ranges forming out-of-focus
`images on the Surface of the object to be measured. In the
`triangulation measuring method, there is no more need for a
`confocally disposed diaphragm. In the second mode for color
`measurement, the diaphragm is revolved out of the optical
`path in order to make it possible to detect the full spectrum of
`the monitoring beam by means of the color sensor.
`0022 Advantageously, the illuminating beam can have a
`spectrum that is similar to daylight at least within the visible
`spectral range of from 400 nm to 700 nm.
`0023 Consequently, such an illuminating beam gives the
`optical impression of daylight.
`0024. The color measurement is carried out in the second
`mode by means of an illuminating beam that simulates the
`illumination of the object to be measured in daylight. In
`colorimetric measurement, the monitoring beam reflected by
`the object to be measured is thus analyzed and its color
`corresponding to the optical impression of the object to be
`measured in daylight is determined. In the first mode for 3D
`measurement and in the second mode, the same light source
`having a spectrum that is similar to daylight can be used at a
`color temperature ranging from 5000 to 6000 K.
`0025 Advantageously, using of a light source that can be
`Switched between the two modes, an illuminating beam hav
`ing a broad-band spectrum can be produced in the first mode,
`and an illuminating beam having a spectrum that is similar to
`daylight can be produced in the second mode.
`0026. In the case of a light source that can be switched
`between the two modes, it is possible to use a white light
`Source having a broad spectrum in the first mode, and any
`other light source having a spectrum that is similar to daylight
`in the second mode. When switching between the two modes,
`either the light source is replaced or the spectrum of the light
`Source is altered appropriately. For example, a plurality of
`colored LEDs can be activated such that either a spectrum that
`is similar to daylight or a broad-band white spectrum is pro
`duced by superimposing the spectra of the colored LEDs. The
`intensity curve of the broad-band spectrum plotted against
`wavelength is non-essential for the effectiveness of the chro
`matic confocal measuring method so that the broad-band
`spectrum can have a plurality of maxima and minima at
`various wavelengths.
`0027 Advantageously, the first objective for operation in
`the first mode and a second objective for operation in the
`second mode can be revolved into the optical path of the
`illuminating beam by means of a revolving mechanism.
`0028. The focal length of the first objective is such that the
`illuminating beam is focused onto the first plane of the Surface
`of the object to be measured, and the focal length of the
`
`0008
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`US 2011/0080576 A1
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`Apr. 7, 2011
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`second objective is measured such that the illuminating beam
`is focused onto a second plane other than the first plane of the
`surface of the object to be measured. When switching
`between the two modes, the corresponding objective is
`revolved into the optical path of the illuminating beam by
`means of a revolving mechanism. As a result, the remaining
`optical configuration of the device remains unchanged, and
`the revolving mechanism can be shifted between the two
`modes, for example, by means of an actuator Such as a rotary
`knob or a control lever. The changeover from the first mode to
`the second can be motor-controlled or can be effected manu
`ally by the user.
`0029 Advantageously, a first objective for operating the
`device in the first mode, and a second objective for operating
`the device in the second mode can be inserted by a user into
`the optical path of the illuminating beam.
`0030) Fastening elements such as flexible clamping brack
`ets making it possible to effect exact positioning of the objec
`tive in the optical path of the illuminating beam can be
`mounted in the device. The user can thus switch between the
`two modes of the device by replacing the objectives. An
`advantage of this embodiment is that only one objective of
`fixed focal length has to be accommodated in the housing of
`the device in either of the two modes so that the device can be
`built with smaller dimensions.
`0031 Advantageously, the device can comprise a base
`unit and a handpiece that are interconnected by means of a
`fiber-optic light guide, the base unit containing a light source,
`a beam deflector, and a color sensor, while the handpiece
`contains the objective.
`0032. The base unit of the device is a permanently
`installed structure. The light Source in the base unit emits an
`illuminating beam having a polychromatic spectrum that cor
`responds to the spectrum of daylight or is as similar thereto as
`possible. The illuminating beam passes through the beam
`splitter and is guided by the light guide to the handpiece. In
`the handpiece, the illuminating beam is focused by means of
`the objective onto the first plane of the surface of the object to
`be measured in the first mode, and onto a second plane other
`than the first plane of the surface of the object to be measured
`in the second mode. The monitoring beam reflected by the
`object to be measured travels through the light guide back to
`the base unit and is deflected by the beam splitter toward the
`color sensor. The image data created in the color sensor can
`then be transmitted by means of a data cable or by radio waves
`to an image analyzing unit for image analysis.
`0033. As a result, the handpiece can be moved indepen
`dently of the base unit, which facilitates the use of the device.
`Furthermore, the handpiece can be configured with small
`dimensions since it contains only the objective and possibly
`the deflection mirror, while the remaining optical compo
`nents such as the light source, the beam splitter, and the color
`sensor are installed in the base unit. Particularly when the
`device is used for dental purposes, this arrangement facili
`tates access of the device to an object to be measured such as
`a tooth in a patient's oral cavity.
`0034 Advantageously, the first handpiece comprising the
`first objective can be connected to the base unit by a user for
`operating the device in the first mode, and a second handpiece
`comprising a second objective can be connected to the base
`unit by the user for operating the device in the second mode.
`0035. The mode of the device is thus changed by inter
`changing the handpieces. In the second mode, the orientation
`of the illuminating beam relative to the handpiece remains
`
`unchanged, while in the first mode the illuminating beam
`performs an oscillating scanning movement for the purpose
`of optically scanning a measuring area. This scanning move
`ment can be produced, for example, by a pivoted mirror that
`is Swiveled accordingly. The second handpiece can be
`designed so as to be more compact than the first handpiece
`since there is no necessity, in the second mode for a mecha
`nism Such as a rotating mirror for the purpose of producing a
`Scanning movement.
`0036 Advantageously, a device forming a single unit
`comprising a light source, a beam splitter, a color sensor, and
`an objective can be encased by a housing.
`0037. The device can be constructed as a single unit in that
`all components are mounted within a housing. A data cable
`then connects the device to an image analyzing unit in order
`to make it possible to analyze the data coming from the color
`sensor. The flexible light guide used in the two-piece embodi
`ment comprising the handpiece and the base unit is not used
`in this embodiment.
`0038 Advantageously, the focal length of the objective
`can be selected in the second mode for colorimetric measure
`ment Such that the illuminating beam is focused onto a second
`plane other than the first plane of the surface of the object to
`be measured, and an out-of-focus image of the illuminating
`beam is formed on the surface of the object to be measured as
`a measuring area in the form of a fuZZy circle of homogeneous
`intensity.
`0039. A measuring area of homogeneous intensity and
`having a spectrum that is similar to daylight is thus provided
`as is required for colorimetric measurement.
`0040 Advantageously, the illuminating beam can com
`prise a plurality of component beams extending parallel to
`each other in one plane.
`0041. In the case of a plurality of component beams, a
`plurality of objectives is used in order to focus the component
`beams in the desired manner.
`0042. The duration of 3D measurement can thus be
`reduced considerably in the first mode, since the component
`beams detect the surface of the object to be measured in
`parallel by means of a simultaneous scanning movement. In
`the second mode, the individual component beams form a
`plurality of fuzzy circles on the surface of the object to be
`measured that are Superimposed on each other to form a
`stripe-shaped measuring area. This measuring area has a
`spectrum that is similar to daylight and a homogeneous inten
`sity distribution so that this measuring area is suitable for
`colorimetric measurement.
`0043 Advantageously, the individual component beams
`can be focused in the first mode by means of the objective
`comprising a plurality of Sub-objectives onto focal points
`disposed in a row in the first plane of the surface of the object
`to be measured. In the second mode, the individual compo
`nent beams can be focused onto focal points disposed in a row
`in a second plane other than the first plane so that the com
`ponent beams form out-of-focus images in the form of fuZZy
`circles on the surface of the object to be measured and are
`Superimposed on each other to form a measuring area.
`0044) The first objective comprises a plurality of sub-ob
`jectives for the individual component beams and the mecha
`nisms for controlling the focal lengths of the individual sub
`objectives are coupled to each other by means of a coupling
`mechanism so that the focal lengths of all Sub-objectives is
`adjusted synchronously. The focal points of the individual
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`component beams can thus be shifted by a user simulta
`neously in the desired manner.
`0045 Advantageously, the device can comprise a deflec
`tion mirror that deflects the illuminating beam onto the object
`to be measured.
`0046. The illuminating beam can be deflected, for
`example, at right angles onto the object to be measured. This
`particularly facilitates the imaging of teeth in a patient's oral
`cavity.
`0047 Advantageously, when using a chromatic confocal
`measuring method, the device can comprise a diaphragm
`disposed between the objective and the color sensor in order
`to allow only that spectral range of a monitoring beam
`reflected by the object to pass through the diaphragm toward
`the color sensor that is derived from that spectral range of the
`illuminating beam that is focused onto the first plane of the
`surface of the object to be measured.
`0048. The confocally disposed diaphragm is an essential
`element of the chromatic confocal measuring method. The
`absolute position of the surface of the object to be measured
`in the direction of the illuminating beam is then ascertained
`from the wavelength of the spectral range that has been
`retained by the filter. The remaining two coordinates of the
`position in a direction extending at right angles to the illumi
`nating beam are ascertained from the image data of the color
`SSO.
`0049 Advantageously, the diameter of the diaphragm in
`the first mode for 3D measurement using the chromatic con
`focal measuring method is larger than the diameter of the
`diaphragm in the second mode for colorimetric measurement
`so that the depth of field in the first mode is shorter than the
`depth of field in the second mode.
`0050. In the first mode, the diameter of the diaphragm is
`larger and the depth of field is thus shorter so that the moni
`toring beam is imaged sharply on the color sensor, and the
`measuring depth can be calculated using the chromatic con
`focal measuring method from the sharply focused wave
`length. In the second mode, the diameter of the diaphragm is
`smaller and the depth of field is thus larger so that all the
`wavelengths are imaged almost sharply and are Superimposed
`on each other to form a white light field, none of the wave
`lengths dominating in the monitoring beam. This white light
`field is detected by the color sensor and the image data are
`used for colorimetric measurement.
`0051) Advantageously, the diaphragm can be controlled
`and the diameter of the diaphragm can be varied.
`0052. The diaphragm can be an iris diaphragm, the diam
`eter of which can be adjusted by rotating an outer ring of the
`iris diaphragm.
`0053 Advantageously, the diaphragm having a larger
`diameter in the first mode can be replaced by a diaphragm
`having a smaller diameter in the second mode.
`0054 The first diaphragm having a larger diameter in the
`first mode can be replaced by the second diaphragm having a
`Smaller diameter in the second mode by mechanical means.
`0055 Advantageously, the depth of focus of the device in
`the first mode can range from 0.1 mm to 1 mm, and the depth
`of focus of the device in the second mode can range from 5
`mm to 30 mm.
`0056. The range of the depth of focus between 0.1 mm and
`1 mm in the first mode is particularly suitable for determining
`the coordinates of the surface of the object to be measured
`using the chromatic confocal measuring method. The range
`of the depth of focus from 5 mm to 30 mm in the second mode
`
`for colorimetric measurement is particularly advantageous,
`since the area of illumination projected onto the object, for
`example a tooth having a height of about 20 mm, must have a
`homogeneous intensity distribution and a white spectrum that
`is preferably similar to daylight. Outside of said depth of field
`range, the wavelengths that are sharply imaged dominate.
`0057 Advantageously, the intensity of the light source can
`be adjusted Such that the decrease in the quantity of light in
`the second mode due to a smaller diameter of the diaphragm
`can be compensated for by an increase in the intensity of the
`light source, in order to make colorimetric measurement pos
`sible.
`0.058 A defined intensity of the monitoring beam detected
`is necessary for colorimetric measurement. The intensity of
`the light Source is increased in order to compensate for the
`Smaller quantity of light caused by a smaller diameter of the
`diaphragm and in order to achieve the required intensity of the
`illuminated area.
`0059 Advantageously, a chromatic objective can be
`placed between the main objective and the object to be mea
`sured. The chromatic objective is inserted into the optical path
`of the illuminating beam in the first mode for optical 3D
`measurement using the chromatic confocal measuring
`method, and is revolved out of the optical path of the illumi
`nating beam in the second mode for colorimetric measure
`ment.
`0060. The chromatic objective intensifies the effect of
`chromatic aberrations such that the focal points for the dif
`ferent wavelengths are kept clearly apart. Thus that wave
`length of which the focal point is located exactly on the
`Surface of the object to be measured is the dominating wave
`length in the monitoring beam. The focal points for a wave
`length of 400 nm and for a wavelength of 800 nm for a
`spectrum similar to daylight can be spaced from each other by
`30 mm. This distance covers the height of an object such as a
`tooth. In the second mode, the chromatic objective is revolved
`about a pivot axis so as to leave the optical path of the illu
`minating beam so that the focal points for the different wave
`lengths move closer together and are almost Superimposed on
`each other. The Superimposed wavelengths thus form a homo
`geneous white light area having a spectrum similar to day
`light.
`0061 Advantageously, the chromatic objective can form
`part of the main objective.
`0062. The chromatic objective and the main objective can
`be combined to form an optical unit in its own housing.
`0063 Advantageously, the chromatic objective can be
`revolved about a pivotaxis so as to leave the optical path of the
`monitoring beam.
`0064. The chromatic objective can be separate from the
`main objective so as to be revolvable about the pivotaxis. The
`revolving movement can be produced mechanically by means
`of an electronically activated revolving mechanism.
`0065 Advantageously, the device can have a slim, arcuate
`design in order to make it possible to carry out 3D measure
`ments of teeth inside a patient's oral cavity and colorimetric
`measurements of tooth surfaces.
`0066. The device of the invention can be used especially as
`a dental device for the 3D scanning and colorimetric mea
`Surement of teeth. The results of these measurements such as
`the 3D data of tooth surfaces and gums and the color of tooth
`Surfaces can then be used for designing dental prosthetic
`items.
`
`0010
`
`

`

`US 2011/0080576 A1
`
`Apr. 7, 2011
`
`0067. A further object of the invention is a method for
`optical 3D measurement and for colorimetric measurement,
`in which a device is switched between a first mode for the
`optical 3D measurement, using the chromatic confocal mea
`Suring method, the triangulation measuring method, or any
`other measuring method, and a second mode for colorimetric
`measurement. In the first mode, a broad-band illuminating
`beam is focused onto a first plane of the surface of an object
`to be measured, and in the second mode, the broad-band
`illuminating beam is focused onto a second plane other than
`the first plane at a distanced from the surface of the object to
`be measured.
`0068. In the second mode, the illuminating beam forms an
`out-of-focus image on the Surface of the object to be mea
`sured so that a fuzzy circle is produced that is suitable for
`colorimetric measurement.
`0069. An objective can be used as the optical system for
`focusing the illuminating beam. Its focal length can be
`adjusted Such that the illuminating beam is focused onto the
`first plane of the surface of the object to be measured in the
`first mode, and onto a second plane in the second mode.
`0070 An advantage of the method of the invention is that
`the same illuminating beam is used for both modes, and the
`changeover between the modes is effected by adjusting the
`focal length of an optical system, such as an objective, to
`influence its focal point.
`0071 Advantageously, a diaphragm can be revolved into
`the optical path of a monitoring beam Such that the diaphragm
`is confocal to the surface of the object to be measured in the
`first mode when using the chromatic confocal measuring
`method, and the diaphragm can be revolved out of the optical
`path of the monitoring beam in the second mode.
`0072. In the first mode, the confocally disposed dia
`phragm is a necessary prerequisite for the use of the chro
`matic confocal measuring method. In the second mode, the
`diaphragm is revolved out since it would otherwise unneces
`sarily restrict the monitoring beam.
`0073 Advantageously, by using a switchable light source
`it is possible to produce an illuminating beam having a broad
`band spectrum in the first mode and an illuminating beam
`having a spectrum that is similar to d