(12) United States Patent
`Durbin et al.
`
`(54) METHOD AND SYSTEM FOR IMAGING
`AND MODELING A THREE DIMENSIONAL
`STRUCTURE
`
`(76)
`
`Inventors: Duane Durbin, 7660 Norcanyon Way,
`San Diego, CA (US) 92126; Dennis
`Durbin, 711 Marsolan, Solana Beach,
`CA (US) 92075
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by O days.
`
`This patent is subject to a terminal dis(cid:173)
`claimer.
`
`(21) Appl. No.: 09/993,110
`
`(22) Filed:
`
`Nov. 6, 2001
`
`( 65)
`
`Prior Publication Data
`
`US 2002/0055082 Al May 9, 2002
`
`I 1111111111111111 11111 lllll 111111111111111 11111 1111111111 111111111111111111
`
`US006592371B2
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 6,592,371 B2
`*Jul. 15, 2003
`
`4,324,546 A
`4,575,805 A
`4,611,288 A
`4,935,635 A
`4,964,770 A
`5,115,307 A
`5,359,511 A
`5,372,502 A
`5,401,170 A
`5,440,383 A
`5,545,039 A
`5,759,030 A
`5,857,853 A
`6,050,821 A
`6,126,445 A
`6,210,162 Bl
`6,227,850 Bl
`6,364,660 Bl *
`6,386,867 Bl *
`
`4/1982
`3/1986
`9/1986
`6/1990
`* 10/1990
`5/1992
`10/1994
`12/1994
`3/1995
`8/1995
`8/1996
`6/1998
`1/1999
`4/2000
`10/2000
`4/2001
`5/2001
`4/2002
`5/2002
`
`....... 433/223
`
`Heitlinger et al.
`Moermann et al.
`Duret et al.
`O'Harra
`Steinbichler et al.
`Cooper et al.
`Schroeder et al.
`Massenet al.
`Nonomura
`Bacchus et al.
`Mushabac
`Jung et al.
`van Nifterick et al.
`Klaassen et al.
`Willoughby
`Chishti et al.
`Chishti et al.
`Durbin et al.
`Durbin et al.
`
`................ 433/29
`................ 433/31
`
`FOREIGN PATENT DOCUMENTS
`40 34 007 Al * 4/1992
`* 10/1998
`WO 98/48242
`
`DE
`WO
`
`Related U.S. Application Data
`
`* cited by examiner
`
`(51)
`
`( 63) Continuation-in-part of application No. 09/696,065, filed on
`Oct. 25, 2000, now Pat. No. 6,364,660, and a continuation(cid:173)
`in-part of application No. 09/726,834, filed on Nov. 30,
`2000, now Pat. No. 6,386,867.
`Int. Cl.7 ......................... G0lB 11/24; A61B 5/103;
`A61C 3/00
`(52) U.S. Cl. .......................................... 433/214; 433/29
`(58) Field of Search .......................... 433/29, 213, 214,
`433/215
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`3,861,044 A
`
`1/1975 Swinson
`
`Primary Examiner-Ralph A. Lewis
`
`(57)
`
`ABSTRACT
`
`Systems and methods for generating a three-dimensional
`(3D) model of a structure include coating the structure with
`a luminescent substance to enhance the image quality, the
`luminescent substance having an excitation range; and cap(cid:173)
`turing one or more images of the structure through at least
`one image aperture each having a frequency sensitivity,
`wherein the frequency sensitivity of each image aperture is
`maximized for the luminescent material emission range.
`
`22 Claims, 9 Drawing Sheets
`
`llluminator, Image Aperture,
`Air Jets & Spray Orifices
`
`/ . 920 - 920'\
`'-
`/
`
`-----
`
`/
`910 - 910'
`
`Lateral Track
`
`Align EX1017
`Align v. 3Shape
`IPR2022-00145
`
`

`

`U.S. Patent
`
`Jul. 15, 2003
`
`Sheet 1 of 9
`
`US 6,592,371 B2
`
`lntraoral Apparatus
`
`100
`
`132
`
`Drive
`Mechanism
`
`134
`
`136'
`
`130
`
`Figure 1
`
`122
`
`Display
`
`110
`
`Image Processor
`
`Computer
`
`120
`
`llluminator &
`cmage Aperture
`
`132 - 134
`
`206
`
`- - - 202
`
`Lateral Track
`
`Figure 2
`
`200
`
`

`

`U.S. Patent
`
`Jul. 15, 2003
`
`Sheet 2 of 9
`
`US 6,592,371 B2
`
`llluminators &
`
`7e Apertures
`----
`
`132A -134A
`
`132 -134
`
`202
`
`Figure 3
`
`

`

`U.S. Patent
`
`Jul. 15, 2003
`
`Sheet 3 of 9
`
`US 6,592,371 B2
`
`Insert Mouthpiece into Patient's Mouth
`
`252
`
`Reset Device
`
`----- 254
`
`250
`
`/
`
`Establish illuminator position, light spectrum and light strength
`
`/
`
`255
`
`Capture image in memory
`
`256
`
`Traverse arc track to capture image on both sides
`
`/
`
`258
`
`Move shuttle to next position
`
`----- 260
`
`N
`
`Generate 3D model and display model
`
`264- 266
`
`Exit
`
`Figure 4
`
`

`

`U.S. Patent
`
`Jul. 15, 2003
`
`Sheet 4 of 9
`
`US 6,592,371 B2
`
`110
`
`j
`
`302
`
`/
`
`304
`
`/
`
`306
`
`v
`
`308
`
`/
`
`310
`
`V
`
`_i..-- 312
`
`v 314
`
`I
`
`RAM
`
`ROM
`
`Display
`
`Motor&
`llluminator
`1/0 Port
`
`Image
`Interface
`
`Computer
`Interface
`
`Storage Drive
`
`300
`
`/
`
`CPU
`
`Figure 5
`
`

`

`U.S. Patent
`
`Jul. 15, 2003
`
`Sheet 5 of 9
`
`US 6,592,371 B2
`
`y
`
`484"';
`
`Image 2 :
`
`/
`
`488
`
`482"'
`
`Image 1
`
`I 486
`
`Aperture
`Field of View
`
`Image
`Aperture 1 @
`_________ -------------···
`(X1, Y1)
`----------~01
`/
`#~-.::::--= - _£ -
`
`-
`
`Aperture
`Field of View
`
`2D Contour of
`Dental Structure
`
`480
`
`(Xu, Yu)
`
`Specific element on suliace
`to be mapped for inclusion
`in model.
`
`01 = line of sight angle from aperture 1 to point (Xu, Yu)
`on surface of dental structure.
`
`Q2 = line of sight angle from aperture 2 to point (Xu, Yu)
`on surface of dental structure.
`
`X
`
`Figure 6
`
`

`

`U.S. Patent
`
`Jul. 15, 2003
`
`Sheet 6 of 9
`
`US 6,592,371 B2
`
`CPU
`
`512
`
`___,. 514
`
`516 "- ..------,
`RAM
`
`500
`
`/
`
`___,.535
`
`536
`532"
`. - - - -~ - - , r-~-~-----,
`Touch Screen
`1/0 Interface
`Display
`
`550
`
`--....._
`
`ADC
`
`NAC
`
`534
`
`"" Drive
`
`/
`
`537
`
`560
`
`Figure 7
`
`

`

`U.S. Patent
`
`Jul. 15, 2003
`
`Sheet 7 of 9
`
`US 6,592,371 B2
`
`llluminator, Image Aperture,
`
`AO Jet zray Orffice
`
`820
`
`810
`
`/ Mouthpiece
`
`/
`
`Single Aperture Arch
`Traverse Mechanism
`
`Lateral Track
`
`Figure 8
`
`Lateral Track
`
`llluminator, Image Aperture,
`Air Jets & Spray Orifices
`
`/s20- 920·\
`"'
`/
`------
`/
`910 - 910'
`
`Figure 9
`
`

`

`U.S. Patent
`
`Jul. 15, 2003
`
`Sheet 8 of 9
`
`US 6,592,371 B2
`
`Insert Mouthpiece into Patient's Mouth
`
`1252
`
`Reset Device
`
`------ 1254
`
`1250
`
`/
`
`Establish illuminator position, light spectrum and light strength
`
`/
`
`1256
`
`Establish air nozzle position and flow parameters
`
`1258
`
`Establish material spray nozzle position and spray parameters
`
`/
`
`1260
`
`Capture image in memory ~---
`
`1262
`
`Traverse arc track to capture image on both sides
`
`/
`
`1264
`
`Move shuttle to next position
`
`------ 1266
`
`N
`
`Generate 3D model and display model
`
`1270 -1272
`
`Exit
`
`Figure 10
`
`

`

`U.S. Patent
`
`Jul. 15, 2003
`
`Sheet 9 of 9
`
`US 6,592,371 B2
`
`110
`
`j
`
`1302
`
`1304
`
`/
`
`/
`
`1306
`v'
`
`1308
`
`/
`
`RAM
`
`ROM
`
`Display
`
`Motor &
`llluminator
`1/0 Port
`
`Air Nozzle
`1/0 Port
`
`1310
`
`/
`
`Spray Nozzle
`1/0 Port
`
`/ 1312
`
`1300
`/
`
`CPU
`
`Image V
`
`Interface
`
`1314
`
`Computer V 1316
`Interface
`
`- 1318
`
`~
`
`Storage Drive
`
`Figure 11
`
`

`

`US 6,592,371 B2
`
`1
`METHOD AND SYSTEM FOR IMAGING
`AND MODELING A THREE DIMENSIONAL
`STRUCTURE
`
`This application is a continuation-in-part application of
`U.S. application Ser. No. 09/696,065, filed Oct. 25, 2000
`now U.S. Pat. No. 6,364,660 Bl and U.S. application Ser.
`No. 09/726,834, filed Nov. 30, 2000, now U.S. Pat. No.
`6,386,867 Bl the contents of which are hereby incorporated
`by reference.
`1. Field of Invention
`The present invention relates to intra-oral methods and
`apparatus for optically imaging a structure and creating
`representative 3D models from the images.
`2. Background
`Determination of the surface contour of objects by non(cid:173)
`contact optical methods has become increasingly important
`in many applications. A basic measurement principle behind
`collecting range data for these optical methods is triangu(cid:173)
`lation. Triangulation techniques are based on elementary
`geometry. Given a triangle with the baseline of the triangle
`composed of two optical centers and the vertex of the
`triangle the target, the range from the target to the optical
`centers can be determined based on the optical center
`separation and the angle from the optical centers to the
`target.
`Triangulation methods can be divided into passive and
`active. Passive triangulation (also known as stereo analysis)
`utilizes ambient light and both optical centers are cameras.
`Active triangulation uses only a single camera and in place 30
`of the other camera uses a source of controlled illumination
`(also known as structured light). Stereo analysis while
`conceptually simple is not widely used because of the
`difficulty in obtaining correspondence between camera
`images. Objects with well-defined edges and corners, such 35
`as blocks, may be rather easy to obtain correspondence, but
`objects with smoothly varying surfaces, such as skin or tooth
`surfaces, with no easily identifiable points to key on, present
`a significant challenge for the stereo analysis approach.
`To overcome the correspondence issue, active 40
`triangulation, or structured light, methods project known
`patterns of light onto an object to infer its shape. The
`simplest structured light pattern is just a spot, typically
`produced by a laser. The geometry of the setup enables the
`calculation of the position of the surface on which the light 45
`spot falls by simple trigonometry. Other patterns such as a
`stripe, or 2-dimensional patterns such as a grid of dots can
`be used to decrease the required time to capture the image
`surface.
`The surface position resolution of structured lighting 50
`methods is a direct function of the fineness of the light
`pattern used. The accuracy of active triangulation methods
`depends on the ability to locate the "center" of the imaged
`pattern at each image capture step. A variety of real-world
`situations can cause systematic errors to be introduced that 55
`affect the ability to accurately determine the true imaged
`pattern "center". Curved surfaces, discontinuous surfaces,
`and surfaces of varying reflectance cause systematic distor(cid:173)
`tions of the structured light pattern on the surface which can
`increase the uncertainty in measuring the position of the 60
`surface being scanned.
`Additional measurement uncertainty is introduced if a
`laser is used as the light source to create the light pattern.
`Due to the coherence of laser light, reflections from the
`surface create a random interference pattern, known as laser 65
`speckle, throughout space and at the image sensor. The result
`is an imaged pattern with a noise component that affects the
`
`5
`
`10
`
`2
`"center" determination, causing measurement errors even
`from a flat surface. The difficulty of determining the "center"
`of the pattern is further compounded if the surface that the
`pattern is projected upon is not opaque but translucent. This
`type of surface can result in the projected pattern "bloom(cid:173)
`ing" at the illuminated surface because of the diffusion of
`light throughout the object. A tooth is an example of a
`translucent object that represents a challenging task from
`which to obtain a surface contour with active triangulation.
`The dental and orthodontic field is one exemplary appli-
`cation for digitally generating 3D models of structures. In
`many dental applications, a working model of a patient's
`teeth is needed that faithfully reproduces the patient's teeth
`and other dental structures, including the jaw structure.
`15 Conventionally, a three-dimensional negative model of the
`teeth and other dental structures is created during an
`impression-taking session where one or more U-shaped
`trays are filled with a dental impression material. Impression
`materials include, among others, compositions based on
`20 alginates, polysulphides, silicones and vulcanizable poly(cid:173)
`ether materials. The impression material is typically pre(cid:173)
`pared by mixing a base component and a hardener or
`initiator or catalyst component. The impression tray con(cid:173)
`taining the impression material, in its plastic state, is intro-
`25 duced into the mouth of the patient. To ensure a complete
`impression, an excessive amount of impression material is
`typically used. While the tray and impression material is
`held in place, the material cures, and after curing, the tray
`and material are removed from the mouth as a unit. The
`impression material is allowed to solidify and form an
`elastic composition, which is the negative mold after
`removal. The working model is obtained by filling this
`impression with a modeling material.
`Dental patients typically experience discomfort when the
`dentist takes an impression of the patient's teeth. The
`procedure can be even more uncomfortable for the patient if
`the impression materials run, slump or are otherwise
`expelled into the patient's throat. Such situations can poten(cid:173)
`tially cause a gag reflex reaction from the patient. In addition
`to patient discomfort, the impression process is time con(cid:173)
`suming. Additionally, the impression process can be error-
`prone. For example, when the impression material is not
`properly applied, the resulting working model may not
`accurately reflect features on the teeth. Moreover, the model
`can show air bubbles trapped during the impression taking
`session. Depending on the accuracy required, such working
`model may not be usable and additional dental impressions
`may need to be taken. Further, the mold and working model
`are fragile and can be easily damaged. The need to store the
`fragile models for future reference tends to become a logis(cid:173)
`tical problem for a dental practice as the number of archived
`models accumulates.
`Automated scanning techniques have been developed as
`alternatives to the mold casting procedure. Because these
`techniques can create a digital representation of the teeth,
`they provide the advantage of creating an "impression" that
`is immediately transmittable from the patient to a dental
`laboratory. The digital transmission potentially diminishes
`inconvenience for the patient and eliminates the risk of
`damage to the mold. For example, U.S. Pat. No. 6,050,821
`discloses a method and apparatus for intraorally mapping the
`structure and topography of dental formations such as peri(cid:173)
`dontium and teeth, both intact and prepared, for diagnosis
`and dental prosthetics and bridgework by using an ultrasonic
`scanning technique. As claimed therein, the method can
`provide details of orally situated dental formations thus
`enabling diagnosis and the preparation of precision mold-
`
`

`

`US 6,592,371 B2
`
`4
`the user apply a coating to the area that is to be imaged to
`create an opaque surface. Typically, titanium dioxide is used
`because of its' high index of refraction. Titanium dioxide is
`a white pigment that is commercially available in one of two
`5 crystalline forms: anatase or rutile and is widely used for
`providing brightness, whiteness, and opacity to such prod(cid:173)
`ucts as paints and coatings, plastics, paper, inks, fibers and
`food and cosmetics.
`To achieve its' optical properties, titanium dioxide par(cid:173)
`ticles must be created with an ideal particle size of 0.3-1 µm.
`In powder form, titanium dioxide must be applied to a
`thickness of between 40 to 60 particles to achieve opacity on
`the tooth surface. This introduces an error into the true
`surface contour of the tooth that can vary from 12 µm to 60
`µm. Since many dental procedures require surface accura(cid:173)
`cies of 25-50 µm the use of titanium dioxide imposes severe
`and unrealistic constraints on the error budgets of the
`remaining parameters involved with making an accurate
`measurement of the teeth surface contours. Further, because
`20 titanium dioxide is a crystalline material, it exhibits optical
`anisotropy so it is important that the applied thickness be
`sufficient to create a truly opaque surface to eliminate
`birefringence effects. In addition, because titanium dioxide
`is an optically rough surface, it provides no reduction in
`25 speckle noise if coherent light is used for the illumination
`source.
`
`3
`ings and fabrications that will provide greater comfort and
`longer wear to the dental patient. Also, as discussed therein,
`infra-red CAD/CAM techniques have been used to map
`impressions of oral structures and make single-tooth pros(cid:173)
`thetics.
`Also, in certain applications such as restorative dentistry
`that is preformed on visible teeth, such as incisors, aesthetic
`considerations require that the prosthetic interface with the
`original tooth surface be underneath the gum (sub gingival)
`to eliminate the sight of the "joining line". In preparation for 10
`the prosthetic, the patient's tooth must be shaped to create a
`ledge or margin beneath the gum line where the prosthetic
`will be sealed to the existing tooth. To prepare this surface,
`the dentist typically places a retraction cord between the
`tooth and gum. The retraction cord creates a working space 15
`that allows the dentist to machine the margin around the
`tooth of interest.
`In order for the finished prosthetic to be correctly sized
`and properly seated on the prepared tooth, it is essential that
`the impression of the prepared tooth contain an accurate
`representation of the sub gingival margin. Improper resolu(cid:173)
`tion of the margin in the impression and the subsequent
`creation of the prosthetic from this impression can result in
`a poor seal along the margin of the prepared tooth and the
`prosthetic. A poor seal along the margin has the potential to
`expose the underlying tooth to decay and the subsequent loss
`of the tooth-the very thing the prosthetic was suppose to
`prevent. Two methods are commonly used to accurately
`capture the margin during the impression process. The first
`method uses a retraction cord to hold the gum away from the 30
`tooth surface to allow the impression compound to flow
`underneath into the sub gingival region. The second method
`uses an impression material with low viscosity that under
`pressure is forced underneath the gums and thus captures the
`sub gingival margin.
`In addition to obtaining sub gingival access for the
`impression material, the area of interest should be dry and
`clean ( dry field) to obtain an accurate impression. A dry field
`is needed because typical impression compounds are hydro(cid:173)
`phobic and the presence of moisture when using a hydro- 40
`phobic impression compound results in bubbles in the
`impression. The dry field is typically created by the dentist
`directing pressurized air across the prepared surface just
`prior to placing the impression tray in the patient's mouth.
`From a surface imaging perspective, human teeth consist 45
`of two primary components: enamel and dentin. The bulk of
`the tooth consists of semi-transparent dentin that is covered
`by a thin translucent layer of enamel that consists almost
`entirely of calcium salts in the form of large apatite crystals.
`These micro crystals form prisms or rods with 4--6 µm 50
`transverse dimensions oriented normally to the tooth sur(cid:173)
`face. The main dentin structural component is micrometer
`sized dentinal tubes, which radiate with an S-shaped curve
`from the pulp cavity toward the periphery. The crystalline
`nature of the enamel surface results in an optically aniso- 55
`tropic medium that results in double refraction or birefrin(cid:173)
`gence of the incident light pattern. Further, the translucent
`nature of the enamel results in a spreading or blooming of
`the incident structured light pattern as observed at the image
`sensor. Similar to the enamel, dentin also exhibits birefrin- 60
`gence as well as having the dentinal tubes act as light
`pipes-further contributing to blooming. The observed color
`of a person's tooth is primarily the result of the frequency
`selective absorption and reflection of the dentin material.
`To minimize the effects of the optical properties of teeth 65
`during imaging, several commercial systems (Sirona Inc.
`Cerac System and Orametrix Inc. Suresmile System) have
`
`SUMMARY
`
`Systems and methods for generating a three-dimensional
`(3D) model of a structure include coating the structure with
`a luminescent substance to enhance the image quality, the
`luminescent substance having an excitation range; and cap(cid:173)
`turing one or more images of the structure through at least
`one image aperture each having a frequency sensitivity,
`35 wherein the frequency sensitivity of each image aperture is
`maximized for the luminescent material emission range.
`For accurately determining the surface contour of a non(cid:173)
`opaque object, the system provides a luminescent coating be
`applied to the surface of the object and then illuminated with
`a structured light pattern at a wavelength, Al, which corre(cid:173)
`sponds to the excitation maxima of the luminescent com(cid:173)
`pound. The incident light at Al induces the luminescent
`compound to emit isotropic radiation at A2. The luminescent
`emission will only occur where the light pattern is incident
`on the surface. An optical filter is used to restrict the input
`to the image sensor to a narrow region around the lumines(cid:173)
`cent compound's emission wavelength, A2, and filters out
`the incident pattern light at Al.
`Advantages of the system may include one or more of the
`following. The system minimizes pattern blooming effect(cid:173)
`when a light pattern is projected onto a translucent object
`both diffuse reflection and diffuse transmission occur. The
`effect of the diffuse transmission is to spread the pattern light
`in all directions within the object. Since translucent objects
`typically will a have relatively low reflection coefficient
`( <5%) the reflected surface pattern image intensity as seen
`by the image sensor will not be significantly larger than the
`diffuse transmitted light within the object-a phenomena
`which has the effect of making the pattern appear larger.
`Conversely, using a luminescent coating results in an unat(cid:173)
`tenuated signal directly from the surface and "noise signals"
`that are reduced >95% by the reflection coefficient of the
`object.
`The system also eliminates speckle noise----due to the
`independent nature of the excitation and emission processes
`of luminescence, the emitted photons are incoherent and
`
`

`

`US 6,592,371 B2
`
`6
`FIG. 5 shows an exemplary image processor for gener(cid:173)
`ating 3D models.
`FIG. 6 shows an exemplary embodiment for modeling
`surface location and contour from stereo images.
`FIG. 7 shows an exemplary computer for using the 3D
`models.
`FIG. 8 shows a third exemplary embodiment of a scanner
`with one aperture, air nozzle and spray orifice.
`FIG. 9 shows a fourth embodiment of a scanner with a
`plurality of apertures, air nozzles and spray orifices.
`FIG. 10 illustrates a process utilizing air jets and spray
`orifices while capturing images and generating 3D models
`from a patient.
`FIG. 11 shows an exemplary image processor for gener(cid:173)
`ating 3D models with controls for air jets and spray orifices.
`
`10
`
`5
`thus do not constructively/destructively interfere in an
`ordered manner. The system works with luminescence com(cid:173)
`pounds with small molecular size to minimize coating
`errors-luminescent compounds are available which allow
`hundreds of layers of material to be used yet still maintain 5
`sub-micron coating depths on the surface being measured.
`Moreover, the frequency shift of emitted luminescent light
`away from the incident pattern illumination frequency
`allows greater image sensor sensitivity and reduces the
`dynamic range requirements.
`The system also provides a spray orifice to coat dental
`structure with substance to improve the imaging capability.
`Images of the dental structures are captured with sufficient
`resolution such that the acquired images can be processed
`into accurate 3D models of the imaged dental structures. The 15
`images and models would have application in dental diag(cid:173)
`nosis and for the specification and manufacture of dental
`working models, dental study models and dental prosthetics
`such as bridgeworks, crowns or other precision moldings
`and fabrications.
`Further, the system provides automated intra-oral scan(cid:173)
`ning of all the dental structures in the jaw through an optical
`aperture and combines the information available in the entire
`set of images to create and present an accurate 3D model of
`the scanned structures. The system allows intra-oral images 25
`of dental structures to be taken rapidly and with high
`resolution such that the acquired images can be processed
`into accurate 3D models of the imaged dental structures. The
`images and models can be used in dental diagnosis and used
`for the specification and manufacture of dental prosthetics
`such as bridgeworks, crowns or other precision moldings
`and fabrications. In addition, the system produces 3D mod-
`els useful in the diagnosis and treatment planning process
`for dental malocclusions. The system-produced data repre(cid:173)
`senting a set of dental images and models can be transmitted
`electronically to support activity such as professional con(cid:173)
`sultations or insurance provider reviews, and the images and
`models may be electronically archived for future reference.
`The digital 3D model of patient's teeth and other dental
`structures has advantages over a conventional cast physical 40
`model due to the following: 1) 3D model efficiently created
`in a single step with accuracy meeting or exceeding the
`conventional multiple step impression technique; 2) reduced
`storage costs; 3) immediate, labor-free retrieval and
`archiving; 4) no model breakage; 5) integrates directly into 45
`computer based analysis tools for diagnosis and treatment
`planning; 6) digital models backup; 7) e-mails to colleagues,
`dental specialists, insurance companies; 8) access to infor(cid:173)
`mation from home, satellite office; 9) effective presentation
`tool; 10) no mess and dust; and 11) no wasted staff time.
`The above and other features and advantages of the
`present invention will be apparent in the following detailed
`description of the preferred embodiments of the present
`invention when read in conjunction with the accompanying
`drawings in which corresponding parts are identified by the 55
`same reference symbol.
`
`20
`
`Description
`Referring to FIG. 1, a system block diagram depicting the
`instrumentation used in scanning teeth and other dental
`structure images and in generating 3D models, will facilitate
`a general understanding and appreciation of the disclosed
`method and apparatus.
`In FIG. 1, an intra-oral scanner 100 is adapted to be placed
`inside the mouth of the patient (intra-oral cavity). The
`intra-oral scanner 100 captures images of various dental
`structures in the mouth and communicates this information
`with a remote image processor 110. The remote image
`30 processor 110 in turn can communicate with a computer 120
`and can display images of the dental structures on a display
`122 connected to the computer 120. Alternatively, function(cid:173)
`alities of the computer 120 such as data storage and display
`can be provided directly by the remote image processor 110
`35 in another embodiment. Images and 3D models derived
`from the images can be transmitted as digital files to other
`equipment or locations by the computer 120.
`In one implementation, the intra-oral scanner 100 is
`embedded in an intra-oral structure, such as a mouthpiece
`130. An image aperture 132 is provided to capture images of
`the dental structures. The image aperture 132 can be an
`objective lens followed by relay lens in the form of a
`light-transmission cable such as a fiber optic cable to trans(cid:173)
`mit images of the dental structures along a pre-selected
`distance to a camera. The fiber optic cable transmits light
`through small filamentary optical materials or fibers.
`Typically, the fibers include a central core and an outer
`surrounding cladding along the entire length of the fiber. The
`transmission of light through the fiber is based on the
`50 phenomenon of total internal reflection. For total internal
`reflection, the refractive index of the core is greater than the
`refractive index of the cladding. In one embodiment, optical
`fibers for the transmission of images comprised of visible
`through mid-infrared light can be used.
`The output of the image aperture 132 can be provided to
`one or more sensors for detecting and converting incident
`light (photons from the light source reflected off the dental
`structure surface )-first into electronic charge (electrons)
`and, ultimately into digital bits. In one implementation, the
`output of the image aperture 132 is provided to a camera (not
`shown), which can be analog or digital. In one embodiment,
`the camera contains one or more image sensor(s) used to
`create digital images of the dental structure. These sensors
`can be devices such as a charge-coupled device (CCD)
`65 sensor or a complementary metal oxide semiconductor
`(CMOS) image sensor. The image sensor can be an array of
`individual photosensitive cells (pixels) whose size deter-
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 illustrates an embodiment of a system for perform(cid:173)
`ing intra-oral scanning and for generating 3D models of 60
`teeth and other dental structures.
`FIG. 2 shows an exemplary embodiment of a scanner with
`one aperture.
`FIG. 3 shows a second embodiment of a scanner with a
`plurality of apertures.
`FIG. 4 illustrates a process in capturing images and
`generating 3D models from a patient.
`
`

`

`US 6,592,371 B2
`
`7
`mines the limiting resolution. Image sensor arrays can have
`from 16x16 pixels to more than 1024x1024 pixels, and the
`arrays can be symmetrical or asymmetrical.
`Further, a source of light delivered through an illuminator
`134 is provided to illuminate the dental structures to 5
`improve the quality or contrast of the images taken by the
`image aperture 132. The light can be white light, light shown
`in one or more colors, or can come from a laser beam. The
`intensity of the light source used to illuminate the dental
`structure is ideally controllable and is in the frequency range 10
`of visible or infra-red light. In one embodiment, the light
`source can be integral to the mouthpiece 130. In another
`embodiment, light can be routed from the light source to the
`illuminator 134 by one or more fiber optic cables (not
`shown). This bundle of optical fibers can be positioned to 15
`surround the outer circumference of the image aperture 132
`to create a plurality of illuminators. The field of illumination
`may be greater than the field of view of the image aperture
`132 and may range up to 180 degrees. In another
`embodiment, the field of illumination may be a focused 20
`beam that illuminates a spot on the dental structure with an
`illumination spot size of dimensions less than 5 mm.
`A drive mechanism 136 is provided to incrementally or
`continuously move the image aperture 132 and the illumi(cid:173)
`nator 134 to various positions in the intra-oral cavity. In one
`embodiment, the image aperture 132 and the illuminator 134
`are movably mounted on a track that is driven by the drive
`mechanism 136. The track can be a U-shaped track con(cid:173)
`forming to the shape of the patient's arch. The drive mecha(cid:173)
`nism 136 can be electrically actuated to move the image
`aperture 132 and the illuminator 134 around all teeth and
`other structures in the jaw. Any of a variety of drive motors
`can be used, and the power of the motor through the drive
`mechanism 136 can be translated into motion for the image
`aperture 132 and the illuminator 134 through rotary, linear,
`hydraulic, or pneumatic mechanisms for example.
`The intra-oral apparatus, as exemplified by mouthpiece
`130, provides the mechanism for traversing image aperture
`132 and the illuminator 134 around the oral cavity and
`positioning the image gathering aperture(s) 132A and
`illuminator(s) 134 at known positions while taking images
`of the dental structures. The mouthpiece 130 in one embodi(cid:173)
`ment includes a sensor arc track 210 that allows the image
`aperture to traverse an arc to capture the image of the dental
`structure while also moving laterally (FIG. 2). In another
`embodiment, the mouthpiece 130 supports multiple image
`gathering apertures in known mechanical alignment and
`moving of said apertures laterally around the oral cavity
`(FIG. 3).
`Although the scanning of one jaw arch at a time has been
`described, it is to be understood that two mouthpieces can be
`simultaneously deployed to capture images of dental struc(cid:173)
`tures on both the upper and lower jaw arches.
`FIG. 2 shows one embodiment of the mouthpiece having
`a single image aperture. In the embodiment of FIG. 2, the
`mouthpiece 130 has a base 200 that is shaped substantially
`in an arch-shape or U-shape. Mounted on the base 200 is a
`lateral rail or track 202 that also conforms to the arch shape
`or U-shape. The track 202 supports a movable shuttle 204 60
`driven by the drive mechanism 136. The shuttle 204 has an
`upwardly extending arm 206. Resting on top of the arm 206
`are the image aperture 132 and the illuminator 134 of FIG.
`1. Additionally, the arc track 210 allows the arm 206 to move
`from a frontal to a posterior view of the