(12) United States Patent
`Engelhardt et al.
`
`I 1111111111111111 11111 lllll lllll lllll 111111111111111 111111111111111 11111111
`US006263234Bl
`US 6,263,234 Bl
`Jul. 17, 2001
`
`(10) Patent No.:
`(45) Date of Patent:
`
`(54) CONFOCAL SURFACE-MEASURING
`DEVICE
`
`(75)
`
`Inventors: Johann Engelhardt, Bad Schonborn;
`Thomas Zapf, Speyer, both of (DE)
`
`(73) Assignee: Leica Microsystems Heidelberg
`GmbH, Mannheim (DE)
`
`6,058,323 * 5/2000 Silverstein et al. .................. 600/473
`6,069,698 * 5/2000 Ozawa et al. ........................ 356/345
`6,095,982 * 8/2000 Richards-Kortum et al. ....... 600/476
`6,129,667 * 10/2000 Dumoulin et al. ................... 600/424
`6,134,003 * 10/2000 Tearney et al. ...................... 356/345
`6,141,577 * 10/2000 Rolland et al. ...................... 600/407
`6,150,666 * 11/2000 Engelhardt et al. ............ 250/559.33
`
`FOREIGN PATENT DOCUMENTS
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by O days.
`
`WO 91/03988
`WO 95/25460
`
`4/1991 (WO) .
`9/1995 (WO) .
`
`OTHER PUBLICATIONS
`
`(21) Appl. No.:
`
`09/147,995
`
`(22) PCT Filed:
`
`Sep.30, 1997
`
`The Confocal System: Leica TCS NT, product brochure
`published Jul. 1998.
`
`(86) PCT No.:
`
`PCT/DE97/02240
`
`* cited by examiner
`
`§ 371 Date: Mar. 24, 1999
`
`§ 102(e) Date: Mar. 24, 1999
`
`(87) PCT Pub. No.: WO98/14132
`
`PCT Pub. Date: Apr. 9, 1998
`
`(30)
`
`Foreign Application Priority Data
`
`Oct. 1, 1996
`
`(DE) .............................................. 196 40 495
`
`Int. Cl.7 ........................................................ A61B 6/00
`(51)
`(52) U.S. Cl. ...................... 600/476; 250/559.22; 356/376
`(58) Field of Search ..................................... 600/473, 476,
`600/478; 356/345, 369, 376; 250/559.22,
`559.4, 216
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5/1974 Elliott .
`3,812,505
`1/1987 Michel .
`4,638,800
`5,383,467 * 1/1995 Auer et al. .
`5,582,171 * 12/1996 Chornenky et al. .
`5,601,087 * 2/1997 Gunderson et al. .
`5,785,704 * 7/1998 Bille et al. ............................. 606/17
`5,804,813 * 9/1998 Wang et al.
`...................... 250/201.3
`6,002,480 * 12/1999 Izatt et al. ............................ 356/345
`6,035,229 * 3/2000 Lemelson ............................. 600/408
`
`Primary Examiner-Marvin M. Lateef
`Assistant Examiner-Shawna J Shaw
`(74) Attorney, Agent, or Firm-Simpson, Simpson &
`Snyder, L.L.P.
`
`(57)
`
`ABSTRACT
`
`The invention concerns a device for the confocal measuring
`of surfaces inside cavities of the body, specially to measure
`the surface profile (1) of teeth (2) in the mouth cavity. Said
`device has a probe (3) that can be introduced into the cavity
`of the body, a light source feeding the probe (3), a detector
`picking up a light signal (5) and a processor (6) to digitalize
`the detected signal transforming it into a tridimensional
`representation. The device is designed using a simple con(cid:173)
`struction and enabling an error free scanning of the surfaces.
`To this end, the probe (3) is designed as a rotary scanner
`having at least one deviating device (7) deflecting the light
`beam (9) in the direction of the surface that is to be measured
`(1 ), the deviating device (7) can be positioned in another
`scanning axis (10) to forward the rotating light beam (9), and
`the detector ( 5) comprises a device for sequential or simul(cid:173)
`taneous scanning of several focal planes, both with regards
`to specular reflection and to weak scattered light or fluores(cid:173)
`cent light of the focal plane concerned.
`
`44 Claims, 4 Drawing Sheets
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`1
`CONFOCAL SURFACE-MEASURING
`DEVICE
`
`BACKGROUND OF THE INVENTION
`
`SUMMARY OF THE INVENTION
`
`2
`in the dental area is mentioned, particularly on page 16.
`However, such a system is too large for use in a patient's oral
`cavity, and too costly to build, and thus too expensive in the
`confines of dental use.
`The invention concerns a device for confocal surface 5
`Ifwe ignore the disadvantages mentioned above, confocal
`measurement in body cavities, especially for measuring the
`microscopy is very specially suited to surface measurement
`surface profile of teeth in the oral cavity, with a probe which
`of tooth surfaces, because this process images only those
`structures which are exactly in the focal plane of the
`can be introduced into the body cavity, a light source
`microscope objective. Thus measurement errors due to the
`supplying the probe, a detector which collects a light signal,
`10 partially transparent tooth material are effectively avoided.
`and a processor which digitizes the detected signal and
`processes it.
`To be sure, the method of reflection measurement with the
`usual confocal microscope fails at steep transitions or flanks
`The invention is based on a method for measuring sur(cid:173)
`if their angle is greater than the aperture angle of the
`faces of any type or contour. Various processes for surface
`objective, because then the reflection no longer enters the
`measurement are known in practice.
`For example, a light sectioning sensor can project a line 15 objective, and is lost for evaluation. (See P. C. Cheng and R.
`G. Summers in Confocal Microscopy Handbook, Chapter
`of light onto the object and observe it at an angle using a
`17.)
`CCD camera. The geometric deformation of the line is
`measured. The height differences on the object can be
`computed from this deformation. By moving the object
`under the sensor-perpendicularly to the light line-and by 20
`repeated measurement of a profile, surface form can be
`measured or determined from a series of profiles.
`The light sectioning sensor is indeed a simply designed
`and robust sensor, but the oblique lighting which it requires 25
`causes unilateral shading of steep surfaces. That causes
`asymmetries in the imaging, or inaccuracies. Furthermore,
`error can be introduced into the measurements because of
`scattering of light from various depths of, for instance, an at
`least partially transparent tooth material.
`Also, a system is already known for measuring the surface
`profile of teeth in the oral cavity. This means consists of the
`principal components camera, monitor, and computer. This
`system is connected directly to a grinding system to produce
`an inlay. (See Dr. Klaus J. Wiedhahn in DENTAL MAGA(cid:173)
`ZIN 1/95, "Cerec 2-a new epoch?".) For the known system
`for measuring the surface profile of teeth, the camera or
`probe is designed so that infrared light is passed though an
`oscillating grooved grating, and is then reflected from the
`tooth surface, which is coated with the white powder, TiO 2 .
`Then the light passes through a symmetric ray path to the
`CCD sensor in the camera. Four individual photographs are
`made at different grating angles in each sequence of photo(cid:173)
`graphs (0.2 second). The four individual images are com(cid:173)
`puted to produce a three-dimensional image of the tooth.
`The three-dimensional "optical impression" obtained with
`the camera is presented on a high-resolution color monitor
`as a pseudoplastic image, and the image and structural data
`are processed in the image-processing computer and the
`built-in processors, and sent to the grinding unit.
`The known process discussed here, and its hardware, have
`problems due to the fact that it is always necessary to coat
`the tooth surface with one or more powders to assure a
`distinct reflection at the tooth surface. Furthermore, the
`construction of the camera with its CCD sensor is expensive. 55
`Finally, it is already known in practice that surfaces can
`be scanned with confocal microscopy so as to generate
`three-dimensional pictures of the surface. In this respect, it
`is only necessary to refer to Johann Engelhardt and Werner
`Knebel, "Konfokale Laserscanning-Mikroskopie" 60
`[Confocal Laser Scanning Microscopy] in 'Physik in unserer
`Zeit', Vol. 24, No. 2, 1993, and to D. K. Hamilton and T.
`Wilson, "Three-dimensional Surface Measurement Using
`the Confocal Scanning Microscope" in Applied Physics,
`B27, 211-213, 1982. With respect to a corresponding 65
`system-Leica TCS NT-we refer to the Leica brochure
`"The Confocal System, Leica TCS NT", where application
`
`Now this invention is based on the objective of presenting
`a system for confocal surface measurement with which
`three-dimensional scanning of surfaces in body cavities,
`such as the surface of a tooth in the oral cavity of a patient,
`is possible. The probe to be introduced into the oral cavity
`should be small enough, and simply designed.
`The surface measurement system according to the inven(cid:173)
`tion achieves the objective stated above by the characteris(cid:173)
`tics of patent claim 1. According to that claim, the system
`under discussion here for confocal surface measurement in
`body cavities, especially for measuring the surface profile of
`teeth in the oral cavity, is designed so that the probe is made
`in the sense of a rotating scanner with at least one deflecting
`means. The deflecting means steers the illuminating beam in
`the direction of the surface to be measured. The deflecting
`means can be moved along another axis to be scanned to
`advance the rotating illuminating beam. The detector com(cid:173)
`prises a system for sequential or simultaneous scanning of
`several focal planes both with respect to specular reflections
`and with respect to weak scattered or fluorescent light from
`the particular focal planes.
`It is quite specially significant for the system according to
`the invention that it is based on the principle of confocal
`microscopy, and that there is sequential or simultaneous
`45 scanning of several focal planes both with respect to specu(cid:173)
`lar reflections and with respect to weak scattered light or
`fluorescent light from the particular focal plane. Now before
`the very particular design embodiments of the system
`according to the invention are explained, the fundamental
`50 functioning will be discussed in relation to confocal surface
`measurement and scanning with respect to specular reflec(cid:173)
`tions and with respect to weak scattered light or fluorescent
`light.
`Here we are concerned with a system for surface mea(cid:173)
`surement using reflection confocal microscopy, particularly
`to measure the surface profile of teeth which are being
`treated or drilled, which is distinguished by confocal imag(cid:173)
`ing with high dynamic response (relative sensitivity) for
`imaging both specular reflections and also weak scattered
`light or fluorescent light from the particular focal plane.
`With respect to the basic process here, it is known that
`confocal microscopy of very specially suited for surface
`measurement of semitransparent materials, as in confocal
`microscopy only those structures exactly in the focal plane
`of the microscope objective are imaged. It is also known that
`the disadvantage of ordinary reflection confocal microscopy,
`with respect to the aperture problem mentioned above, can
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`be eliminated by utilizing scattered light or fluorescent light
`from the particular focal plane for the usual evaluation of the
`reflection.
`The confocal imaging can be accomplished highly
`dynamically, that is, with high relative sensitivity, to carry 5
`out an evaluation of the scattered or fluorescent light, so that
`it is possible both to image highly reflective flat areas and
`also to show the scattered or fluorescent light even on steep
`flanks. Accordingly, imaging is possible even if the light
`reflected from steep flanks misses the objective such that, in 10
`the usual reflection process, no profilometry can be done.
`Finally, the scattered light is always used for evaluation if
`imaging is no longer possible in the absence of specular
`reflections by the usual confocal microscopy.
`As mentioned earlier, the signal detected is digitized at 15
`high resolution, and, as much as possible, at a dynamic range
`considerably greater than 8 bits. For very effective utiliza(cid:173)
`tion of the weak scattered or fluorescent light in the areas
`with steep surface slopes, the relative sensitivity, or dynamic
`range, of confocal imaging can be 16 bits. Finally, in this 20
`way a great brightness difference can be produced by
`evaluating scattered light in the regions with steep flanks.
`An algorithm is provided to evaluate elevations, or to
`produce the surface profile, using weak scattered light. It
`takes into consideration, or tolerates, the high dynamic range
`of the system. This algorithm takes the nearest, or indirectly
`adjacent focal planes into consideration by interpolating,
`with the higher intensities in the local region being relatively
`over-weighted so as to reduce the dependence on the back(cid:173)
`ground signals. Finally, a suitable algorithm is provided, so 30
`that, after detection of the scattered light signal and after
`high-resolution digitizing, an adequate height evaluation can
`be made from the digitized signal.
`It must be emphasized here that the surfaces can also be
`scanned with a dark-field system. Either a point light source
`or a light source appropriately diaphragined can be pro(cid:173)
`vided.
`In the area of application to dentistry, and particularly to
`producing exactly fitted inlays instead of the usual amalgam 40
`fillings, it is very specially advantageous first to scan the
`surface of the untreated tooth and to store the detected
`values, preferably digitized and already processed to give
`the height profile. In the next step the tooth is treated or
`drilled. Then the treated or drilled tooth is scanned again,
`again with storage of the values giving the surface profile of
`the treated tooth. From the difference between the two
`surface profiles, or from the values across the surface profile,
`the surface, or the exact measurements, are calculated for the
`inlay required so as to give optimal occlusion of the treated
`tooth.
`It is highly advantageous, to get particularly high preci(cid:173)
`sion in processing the inlay, if the inlay being produced is
`scanned after an initial processing, and if the further pro(cid:173)
`cessing is done by means of correction values obtained by a
`comparison of the actual and desired values. Correction to
`verify the inlay shape is possible to the extent that, with
`repetition of this process, high precision is possible in
`producing the inlay and optimal occlusion is possible. The
`measures described above also allow consideration of inac- 60
`curacies caused by the equipment or the tools, such as tool
`wear, to be taken into consideration so that optimal fitting of
`the inlay and thus optimal occlusion are possible even with
`a tolerance range at the processing station.
`It is also possible that, in a subsequent step, the cavity 65
`produced in the tooth may be filled with a plastic compo(cid:173)
`sition so that, when the patient bites on it, the contact points
`
`4
`with the opposing teeth are marked in the plastic mass. Then
`the surface profile generated in that way is scanned, the
`measurements obtained with respect to the surface profile
`are stored, and they are taken into consideration in calcu(cid:173)
`lating the surface or dimensions of the inlay to be produced.
`Now it is of very special importance with respect to the
`design of the system according to the invention that the
`probe is designed as a rotating scanner, specifically, that the
`illuminating beam scans over the surface being measured, or
`the tooth, in a rotary manner, so that the "focal plane" being
`scanned by the rotary movement of the illuminating beam is
`developed as a segment of a cylinder. Then, in the subse(cid:173)
`quent data processing, an appropriate transformation of the
`coordinates of the scanned cylinder segment to a true focal
`plane is required. That is, a geometric correction is required.
`This is discussed later.
`The probe, which is made as a rotary scanner, comprises
`a deflecting means with at least one reflective surface, which
`deflects the illuminating beam toward the surface to be
`measured. The deflecting,means, or the reflective surface,
`can be moved so as to advance the illuminating beam, which
`is rotated by the deflecting means, along another axis which
`is to be scanned, so that the rotating illuminating beam, with
`simultaneous linear movement of the deflecting means,
`25 carries out a spiral movement, or a movement similar to a
`screw thread.
`Now, to be able to scan the entire surface profile, with
`varying heights, that is, with: differing focal points, in the
`course of the surface scanning, means is also required for
`sequential or simultaneous sampling of several focal planes.
`This means is preferably part of the detector. It is always
`important in this respect that the object is illuminated or
`scanned by the illuminating beam over a focus region which
`35 can be specified. The light which is reflected back after
`interaction with the object or with the surface of the object
`is focused by a collecting optical system into the image field,
`in which the essentially central portion of the light focused
`there is deflected in the direction of the detection means in
`multiple image planes. Without considering an actual
`embodiment of the means for sequentially or simultaneously
`sampling multiple image planes, it is always important that
`such sampling-sequential or simultaneous-is accom(cid:173)
`plished both for specular reflections and for weak scattered
`45 light or fluorescent light.
`With respect to an actual embodiment of the means
`according to the invention, particularly with respect to an
`actual embodiment of the probe and its internal operation,
`from the viewpoint of simple design, it is quite particularly
`50 advantageous if the deflecting means is made as a simple
`mirror. This simple mirror can be turned or rotated to deflect
`the illuminating beam at an appropriate angle to the illumi(cid:173)
`nating beam. The deflecting means could also be designed as
`a prism or as a polygon with multiple facets to produce
`55 multiple beam deflectors. In the case of an embodiment as
`a polygon with multiple facets, it is possible to attain, by an
`appropriate arrangement, a system with the minimum linear
`movement orthogonal to the plane swept out by the rotating
`illuminating beam. We shall return to that later.
`In the actual case, the probe can comprise a housing to be
`introduced into the oral cavity, with a rotatable rotor making
`up the deflecting means within the housing. Then the
`deflecting means is placed in the vicinity of an illumination
`and detection window of the housing, so that the beam
`directed toward the object to be scanned can arrive, without
`interference, at the surface to be scanned, at least in a region
`established by the illumination and detection window. The
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`miniaturizing all the functional units. That, correspondingly,
`would be a compact system needing only connection to the
`proper power supply. Within the limits of a simple design of
`the probe, though, it is reduced to the essential functional
`5 units, so that the probe is connected by a fiber optic system
`with the units performing further processing and also with
`the light source.
`Finally, it must be noted that the processor can also take
`over several functions, such as control, transformation or
`geometric correction, and digitizing of the signal, serving to
`compute the three-dimensional surface profile or for storing
`the data.
`
`5
`reflected detection beams returns appropriately back through
`the illumination and detection window in the probe, via the
`deflecting means, to a detector which will be explained later.
`An optical system which focuses the illuminating beam
`parallel with the axis of rotation is inside the rotor. This
`optical system turns jointly with the rotor, so that a rota(cid:173)
`tionally symmetric embodiment is required, in which the
`optical system and the deflecting system turn jointly in or on
`the rotor because of their arrangement.
`The rotor is guided, or supported in bearings, within the 10
`housing so that it can rotate freely and so that it can be
`moved linearly, in one particularly advantageous and simple
`embodiment. A special rotor drive is provided for rotation
`and linear advance of the rotor, although two independent
`drives can also be used for the rotation and for the linear 15
`advance of the rotor. In a very particularly advantageous
`embodiment, the rotary movement and the linear advance of
`the rotor are firmly coupled by the rotor having an external
`thread which is guided, so that it can rotate, in an internal
`thread in the housing. In order to be able to scan the surfaces
`with the minimum separations between scans, the threads
`are designed as fine threads with very low pitch. Such fine
`threads then suffice to provide the smallest possible linear
`advance if the deflecting means is a polygon with multiple
`facets, so that the interaction between low pitch and the
`geometric arrangement of the facets can provide a linear
`advance in the vicinity of about 500 micrometers per scan
`line.
`It is also possible to make the thread as a differential
`thread with very low rate of advance, so that it is possible to
`attain an advance in the vicinity of preferably 50 microme(cid:173)
`ters per scan line. It is possible to insert a further means to
`increase or reduce the linear advance.
`The rotor drive which provides the rotary movement 35
`and/or the linear advance is advantageously made part of the
`housing, acting directly between the housing and the rotor.
`For instance, this drive could be solidly mounted in the
`housing and could hold the rotor. In the case of an embodi(cid:173)
`ment of the rotor having an external thread, it could act 40
`directly on the external thread in the sense of a spindle drive.
`Here, again, other drive or force transfer variations can be
`produced.
`The light source used to produce the illuminating beam
`could be a laser light source, and, in particular, a diode laser. 45
`In the illuminating beam path from the light source there can
`be a beam splitter and a means for controlling the focus or
`for changing the focal length of the illuminating beam. To
`the extent that the light source is a polyfocal light source,
`i.e., a light source with different focal lengths, there is no 50
`need for a focus control, so that the system can be simplified.
`Then it would be appropriate for the light source to be
`followed only by the beam splitter in the illuminating beam
`path, and the detector would appropriately be a polyfocal
`detector.
`According to the description above, the probe is defined,
`from the spatial viewpoint, essentially by the housing. The
`light can be introduced into the probe advantageously by an
`optical fiber, and the signal produced by interaction at the
`surface of the object being scanned is carried out of the
`probe advantageously by an optical fiber.
`It would also be conceivable to integrate other functional
`units which are outside the housing in the foregoing descrip(cid:173)
`tion into the housing or to place them within the housing. For
`instance, the light source and/or the beam splitter and/or-if
`necessary-the focusing control and/or the detector and/or
`the processor could be arranged within the housing by
`
`30
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`Now there are various possibilities for applying and
`developing the teaching of the foregoing invention in an
`advantageous way. We refer to the claims subordinate to
`patent claim 1, and to the following explanation of three
`example embodiments of the invention by means of the
`20 drawing. In combination with the explanation of the pre(cid:173)
`ferred example embodiments of the invention, the generally
`preferred embodiments and developments of the teaching
`will also be explained. The drawing shows:
`FIG. 1: a schematic presentation of a first example
`25 embodiment of the system according to the invention;
`FIG. 2: a schematic presentation of a second example
`embodiment of the system according to the invention;
`FIG. 3: a schematic presentation of a third example
`embodiment of the system according to the invention;
`FIG. 4: a schematic presentation of the sampling of an
`object after deflection of the illuminating beam at a polygon,
`where the interaction of the rotating movement and the
`linear advance of the illuminating beam leads to scanning in
`segments of a cylinder; and
`FIG. 5: a schematic presentation of the result of the
`scanning after transformation or geometric correction.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`FIGS. 1 to 3 show three different example embodiments
`of a system according to the invention for confocal surface
`measurement of the surface profile 1 of teeth 2 in an oral
`cavity not shown here.
`The system comprises a probe 3 which can be introduced
`into the oral cavity, a light source 4 which supplies the probe
`3, a detector 5 which picks up a light signal, and a processor
`6 which digitizes the detected signal and processes it into a
`three-dimensional representation.
`According to the invention, the probe 3 is made in the
`sense of a rotary scanner, in which the probe 3 includes a
`deflecting means 7 with a reflective surface 8. The deflecting
`means 7 deflects the illuminating beam 9 toward the surface
`1 which is to be measured, and the deflecting means 7 can
`55 be moved so as to advance the rotating illuminating beam 9
`along the scanning axis 10.
`The detector 5 has a means, not shown in the figures, for
`sequential or simultaneous sampling of several focal planes
`for both spicular reflections or weak scattered light or
`60 fluorescent light from the particular focal plane, so that the
`entire sample or the tooth 2 can be sampled three(cid:173)
`dimensionally.
`According to the representation in FIGS. 1, 2, and 3, the
`deflecting means 7 is made as a simple mirror with a single
`65 reflective surface 8. With respect to further possible
`embodiments, we refer to the general description to avoid
`repetitions.
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`It is a common feature of the example embodiments
`shown in FIGS. 1 to 3 that the probe 3 has a housing 11 with
`a rotor 12 carrying the deflecting means 7 in the housing 11.
`The deflecting means 7 or the reflective area 8 is placed in
`the vicinity of an illumination and detection window 13 of
`the housing 11.
`An optical system 15 to focus the illuminating beam 9
`which runs parallel with the axis of rotation 14 is placed
`within the rotor 12.
`In the first example embodiment shown in FIG. 1, the
`rotor 12 is guided or mounted in bearings so that it can be
`turned freely and advanced linearly within housing 11. A
`common rotor drive 16 is provided for both the rotary
`motion and the linear advance of rotor 12. This drive can act
`on rotor 12 through a special coupling mechanism.
`In the example embodiments shown in FIGS. 2 and 3, the
`rotor 12 has an external thread 17 by which it is guided, so
`that it can rotate, in an internal thread 18 of housing 11. Thus
`the rotary motion of rotor 12 is firmly coupled with its linear
`advance. Threads 17, 18 are designed as fine threads with
`low pitch, so that just one rotor drive 16 is provided to turn
`the rotor and thus, necessarily, to produce the linear advance
`of rotor 12. In all the example embodiments shown here the
`rotor drive 16 is applied directly to housing 11, so that the
`rotor drive 16 acts directly between the housing 11 and the
`rotor 12.
`In the example embodiments shown in FIGS. 1 and 2, the
`light source 4 is designed as a laser light source.
`Correspondingly, light source 4 is followed in the illumi-
`nating light path 19 by a beam splitter 20 and a means 21 for
`controlling the focus or changing the focal length.
`In the example embodiment shown in FIG. 3 the light
`source 4 is a polyfocal light source. Here only one beam
`splitter 20 follows the light source 4 in the illumination beam 35
`path 19, so that detector 5 is a polyfocal detector. Here, no
`means is required for focus control or changing the focal
`length.
`In the example embodiments shown in the figures, the
`light is fed into probe 3 and the light is directed out of probe 40
`3 through a optical fiber not shown in the figures. It acts as
`a flexible connection between the probe 3 and the light
`source 4, and also to the evaluation unit, thus serving to take
`out the signal resulting from the interaction of the light at the
`surface of the tooth 2 being scanned.
`FIGS. 4 and 5 show a schematic representation of the
`scanning process with a rotating light beam and linear
`advance. In this case, a polygon 22 is used as the deflecting
`means 7. The illuminating beam 9 is reflected at a facet 23
`of the polygon 22, going from there to the surface profile 1 50
`of the tooth 2. The surface profile 1 is scanned along the
`cylinder segment 24, one cylinder segment after another, so
`that different focal planes show the individual focal planes
`through sequential or simultaneous sampling and with
`respect to specular reflections as well as with respect to weak 55
`scattered light or fluorescent light from the various focal
`planes.
`The scanning values based on cylinder segments are
`transformed, in a geometric correction, to a "true" focal
`plane, according to the schematic representation of FIG. 5, 60
`so that an undistorted three-dimensional representation of
`the surface profile 1 or of the tooth 2 can be computed from
`the scans.
`Finally, it must be noted that the example embodiments
`explained above are intended only to clarify the teaching 65
`claimed here by actual cases, but the teaching is not limited
`to the example embodiments.
`
`8
`LIST OF REFERENCE NUMBERS
`1 Surface profile, surface
`2 Tooth
`3 Probe
`4 Light source
`5 Detector
`6 Processor
`7 Deflecting means
`8 Reflective surface
`9 Illuminating beam
`10 Axis (for linear movement of the rotor)
`11 Housing
`12 Rotor
`13 Illumination and detection window
`14 Axis of rotation (of the rotor)
`15 Optical system
`16 Rotor drive
`17 External thread ( of the rotor)
`18 Internal thread ( of the housing)
`19 Illuminating beam path
`20 Beam splitter
`21 Means for focus control
`22 Polygon
`23 Facet (of the polygon)
`25 24 Cylindrical segment (of the scan)
`What is claimed is:
`1. A device for confocal surface measurement in body
`cavities comprising:
`a light source for providing an illuminating beam travel(cid:173)
`ing along an illuminating beam path;
`a probe that can be introduced into said body cavity, said
`probe being connected to said light source to receive
`said illuminating beam;
`a light-deflecting means carried by said probe for deflect(cid:173)
`ing said illuminating beam in the direction of a surface
`to be measured;
`means for rotating said light-deflecting means about an
`axis of rotation to generate a profile scan of said
`surface;
`means for linearly advancing said light deflecting means
`along a scanning axis extending parallel to said axis of
`rotation to provide a plurality of said profile scans
`along said scanning axis, said plurality of profile scans
`corresponding to a focal plane of said illuminating
`beam;
`means for changing the focus of said illuminating beam to
`scan said surface at a plurality of different focal planes;
`a detector for receiving specular reflections of said illu(cid:173)
`minating beam, weak scattered light and fluorescent
`light from said surface and generating a sampli