Dental arch digital 3D model with accurate dental arch width

Abstract

A method of generating a virtual 3D model of a dental arch is provided. The method includes receiving an intraoral scan of a dental arch, determining a first depth of a first intraoral 3D surface in the first intraoral scan, and determining a second depth of a second intraoral 3D surface in the first intraoral scan, where a fixed distance exists between the first intraoral 3D surface in the first intraoral scan and the second intraoral 3D surface. The method further includes stitching together the intraoral scans and generating a virtual 3D model of the dental arch from the intraoral scans, where a fixed distance between the first intraoral 3D surface and the second intraoral 3D surface is included in the virtual 3D model.

Description

[0001] This application is a divisional application of the invention patent application with Chinese application number 202080087676.2 (corresponding to PCT international application number PCT / US2020 / 060283), application date November 12, 2020, and invention name “Digital 3D model of dental arch with accurate dental arch width”. Technical Field

[0002] Embodiments of the present disclosure relate to the field of intraoral scanning, and in particular, to a system and method for improving the results of intraoral scanning in an oral cavity (eg, the results of intraoral scanning of an oral cavity that is missing one or more teeth). Background Art

[0003] In restorative procedures designed for implanting a dental prosthesis in the oral cavity, the tooth site where the prosthesis is to be implanted should in many cases be accurately measured and carefully studied so that the prosthesis, such as a crown, denture, or bridge, can be appropriately designed and sized to fit in place, for example. For example, a good fit enables mechanical stresses to be properly transferred between the prosthesis and the jaw and prevents gum infection via the interface between the prosthesis and the tooth site.

[0004] Some procedures also require the fabrication of a prosthesis to replace one or more missing teeth, such as partial or full dentures, in which case the surface contours of the area of ​​missing teeth need to be accurately replicated so that the resulting prosthesis fits the edentulous area and applies even pressure to the soft tissue.

[0005] In some practices, the tooth site is prepared by a dentist and a positive physical model of the tooth site is constructed using known methods. Alternatively, the tooth site can be scanned to provide 3D data of the tooth site. In either case, a virtual or real model of the tooth site is sent to a dental laboratory, which manufactures the prosthesis based on the model. However, if the model is defective or undefined in certain areas, or if the preparation is not optimally configured to accommodate the prosthesis or is inaccurate, the design of the prosthesis may not be optimal.

[0006] In orthodontic procedures, it may be important to provide a model of one or both jaws. In the case of virtually planning such orthodontic procedures, a virtual model of the dental arch may also be beneficial. Such a virtual model may be obtained by scanning the oral cavity directly, or by generating a physical model of the dentition and then scanning the model with a suitable scanner.

[0007] Therefore, in restorative and orthodontic procedures, obtaining a three-dimensional (3D) model of the dental arch in the oral cavity is an initial procedure performed. When the 3D model is a virtual model, the more complete and accurate the scan of the dental arch is, the higher the quality of the virtual model, and thus the greater the ability to design the optimal prosthesis or orthodontic treatment appliance.

[0008] Scanning of dental arches is complicated by areas where a patient is missing teeth, known as edentulous areas. For example, in cases where two or more adjacent teeth are missing, a large span of soft tissue may need to be scanned. Such areas can be difficult to scan because these edentulous areas lack features that can successfully apply stitching between scans.

[0009] A common specific inaccuracy for virtual 3D models generated from scans of dental arches or molds of dental arches is the inaccuracy of the width of the dental arch or jaw (called intermolar width). The virtual 3D model is generated by stitching together images of many smaller dental arch portions, and each registration of one image with another introduces a small amount of error. These small errors accumulate, so that the accuracy of the distance between the rightmost molar and the leftmost molar (intermolar width) usually has an error of about 200-400 microns. Although an error of 200-400 microns is acceptable for some dental procedures (for example, in the case of a single crown), this level of error may cause other dental procedures to fail. For example, the all-on-4 procedure of placing a full set of dentures on four dental implants attached to the patient's jaw is a global structure of the intermolar width that requires high accuracy. However, the all-on-four procedure is usually performed on an edentulous dental arch, which reduces the accuracy of the virtual 3D model of the dental arch due to the lack of features for stitching or the low quality of features for stitching. Therefore, obtaining accurate 3D models of dental arches for full-on four-way procedures is particularly challenging.

[0010] Some intraoral scanners are used in conjunction with powders that are applied to the tooth area. The powder may include particles that are distinguishable from other powder particles, with the goal of providing measurable points on the tooth site that provide features for stitching (also referred to herein as registration). For such systems, these particles, when operating as intended, can be used to assist in image registration. However, powders generally do not attach well to soft tissue, especially wet soft tissue. In addition, the powder may become wet and / or wash away during the scanning process, thereby reducing the accuracy of subsequent image registration. In addition, many patients do not like to have powder applied to their teeth and in their mouths. Having to powder the teeth may have disadvantages such as the following:

[0011] 1. All areas must be powdered and the thickness of the powder layer is uneven, which affects accuracy (for example, because the surface is not scanned directly);

[0012] 2. If the scanner head contacts the powder, the powder sticks to the optics, causing noise in the scan;

[0013] 3. Powders can be expensive;

[0014] 4. Some people are allergic to powder; and

[0015] 5. All teeth are painted white, so color scans of teeth are not possible. Summary of the invention

[0016] In a first aspect of the present disclosure, a method includes receiving, by a processing device, a plurality of intraoral scans of a dental arch. The method also includes determining, by the processing device, that at least one of the plurality of intraoral scans includes a buccal view of a first three-dimensional (3D) surface and a lingual view of at least a feature of a second 3D surface, the second 3D surface not being connected to the first 3D surface in the at least one intraoral scan, wherein a distance exists between the first 3D surface and at least a feature of the second 3D surface in the at least one intraoral scan. The method also includes stitching together the plurality of intraoral scans and generating a virtual 3D model of the dental arch from the plurality of intraoral scans, wherein the distance between the first 3D surface and the second 3D surface in the virtual 3D model is based on the distance between the features of the first 3D surface and the second 3D surface in the at least one intraoral scan.

[0017] In another aspect of the present disclosure, a method includes receiving, by a processing device, a plurality of intraoral scans of a dental arch. The method also includes determining, by the processing device, that at least one of the plurality of intraoral scans includes a depiction of a first three-dimensional (3D) surface and a depiction of at least features of a second 3D surface, the second 3D surface being separated from the first 3D surface by at least one intermediate 3D surface not shown in the at least one intraoral scan, wherein a distance exists between the features of the first 3D surface and the second 3D surface in the at least one intraoral scan. The method also includes stitching the plurality of intraoral scans together and generating a virtual 3D model of the dental arch from the plurality of intraoral scans, wherein the distance between the first 3D surface and the second 3D surface in the virtual 3D model is based on the distance between the features of the first 3D surface and the second 3D surface in the at least one intraoral scan.

[0018] In another aspect of the present disclosure, a method for scanning an edentulous dental arch of a patient includes receiving an indication that a dental prosthesis is to be made for the patient, wherein the dental prosthesis is to be attached to at least a first dental implant and a second dental implant on the edentulous dental arch. The method also includes receiving a plurality of intraoral scans of the edentulous dental arch and determining whether any of the plurality of intraoral scans depicts both a first scan volume associated with the first dental implant and a second scan volume associated with the second dental implant. The method also includes, in response to determining that none of the plurality of intraoral scans depicts both the first scan volume and the second scan volume, outputting instructions to position a probe of an intraoral scanner to generate at least one intraoral scan depicting both the first scan volume and the second scan volume. The method also includes receiving the at least one intraoral scan depicting the first scan volume and the second scan volume and generating a virtual three-dimensional (3D) model of the edentulous dental arch using the plurality of intraoral scans and the at least one intraoral scan. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present disclosure is illustrated by way of example and not limitation in the figures of the accompanying drawings.

[0020] Figure 1A Shown is a scan set of an edentulous dental arch with four scan volumes in accordance with an embodiment of the present disclosure.

[0021] Figure 1B A series of transformations for registering intra-oral scans of a dental arch together is shown in accordance with an embodiment of the present disclosure.

[0022] Figure 1C A flowchart of a method for generating a virtual 3D model of a dental arch according to an embodiment of the present disclosure is shown.

[0023] Figure 1D A flowchart of a method for generating a virtual 3D model of a dental arch according to an embodiment of the present disclosure is shown.

[0024] Figure 2A A flowchart of a method for generating a virtual 3D model of a dental arch according to an embodiment of the present disclosure is shown.

[0025] Figure 2B A flowchart of a method for generating a virtual 3D model of a dental arch according to an embodiment of the present disclosure is shown.

[0026] Figure 3 One embodiment of a system for performing an intraoral scan and generating a virtual 3D model of a dental arch is shown.

[0027] Figure 4A An example scan of an edentulous dental arch is shown in accordance with an embodiment of the present disclosure.

[0028] Figure 4BAn example scan of a dental arch with edentulous areas is shown in accordance with an embodiment of the present disclosure.

[0029] Figure 4C Several example scans of an edentulous dental arch are shown in accordance with embodiments of the present disclosure.

[0030] FIG. 4D to FIG. 4J Some exemplary intra-oral scans showing nearby and distant teeth in a single scan are shown, which may be used to improve the accuracy of surface registration, in accordance with an embodiment of the present disclosure.

[0031] Figure 5A is a schematic diagram of a handheld wand having multiple structured light projectors and cameras disposed within a probe at a distal end of the handheld wand according to an embodiment of the present disclosure.

[0032] Figure 5B yes Figure 5A Schematic diagram of a probe and a magnified view of a portion of the 3D surface.

[0033] Figure 6 FIG. 1 is a diagram illustrating a structured light projector and a camera according to an embodiment of the present disclosure. Figure 5A Diagram of several different configurations of the location of the probe.

[0034] Figure 7 is a schematic diagram of a structured light projector according to an embodiment of the present disclosure, which projects a distribution of discrete unconnected light spots onto multiple object focal planes.

[0035] FIG. 8A to FIG. 8B is a schematic diagram of a structured light projector that projects discrete unconnected spots and a camera sensor that detects the spots according to an embodiment of the present disclosure.

[0036] Fig. 9 is a flow chart outlining a method for determining a depth value for a point in an intraoral scan according to an embodiment of the present disclosure.

[0037] Fig.10 The present invention is an overview of the embodiments of the present invention. Fig. 9 A flowchart of a method of specific operations in a method.

[0038] Fig.11 , Fig.12 , Fig.13 and Fig.14 The present invention is described in accordance with an embodiment of the present invention. Fig.10 Schematic diagram of a simplified example of the operation of .

[0039] Fig.15 is a flowchart outlining other operations in a method for generating a digital three-dimensional image according to an embodiment of the present disclosure.

[0040] Fig.16 , Fig.17 , Fig.18 and Fig.19 The present invention is described in accordance with an embodiment of the present invention. Fig.15 Schematic diagram of a simplified example of the operation of .

[0041] Fig. 20 A block diagram of an example computing device is shown in accordance with an embodiment of the present disclosure. DETAILED DESCRIPTION

[0042] Described herein is a method and apparatus for improving the quality of intraoral scans of dental arches, including the quality of intraoral scans of dental arches of patients who are partially or completely missing teeth. In particular, embodiments enable generation of a virtual 3D model of a dental arch that has an error of less than 200 microns with respect to the width of the dental arch (e.g., the intermolar width). In some embodiments, the error in the intermolar width may be less than 100 microns, or may be as low as 20 microns or less, and thus may be significantly less than the error in the intermolar width of a 3D model of a dental arch generated using a conventional intraoral scanner. For example, conventionally, the error in the intermolar width of a 3D model of a dental arch is approximately 200-400 microns, while in embodiments, the error in the intermolar width of a 3D model of a dental arch may be less than 200 microns, less than 180 microns, less than 150 microns, less than 120 microns, less than 100 microns, less than 80 microns, less than 50 microns, or less than 20 microns.

[0043] Embodiments provide improved techniques for generating a 3D model of a dental arch using a large field of view (FOV) and / or a wide range of depth of focus. One or more scans may be generated that include at least features of a first 3D surface on a first quadrant of the dental arch and a second 3D surface on a second quadrant of the dental arch. These scans may be used with other conventional scans to generate a highly accurate 3D model of a dental arch (e.g., with an error as low as 20 microns in some embodiments).

[0044] In one embodiment, a processing device receives an intraoral scan from an intraoral scanning session of a patient. An intraoral scan may be or include discrete images (e.g., point-and-shoot images) or frames from an intraoral video (e.g., continuous scans). Some intraoral scans may include a representation of a first 3D surface on the proximal half of the dental arch (or quadrant of the jaw) and a representation of a distal 3D surface on the distal half of the dental arch (or quadrant of the jaw). In some embodiments, the 3D surface on the proximal half of the dental arch may have a depth (distance from the probe of the intraoral scanner) of approximately 0-5 mm or 0-10 mm. In some embodiments, for a molar-to-molar distance, the 3D surface on the distal half of the dental arch may have a depth of approximately 40-90 mm or approximately 30-80 mm. Thus, a single intraoral scan may have a greater depth (e.g., up to 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, or 90 mm) and may include representations of two 3D surfaces on the left and right halves of the dental arch. This intraoral scan can be used to greatly improve the accuracy of the virtual 3D model of the dental arch by reducing or eliminating the error accumulation that typically occurs when a scan of the molars (or molar region if molars are missing) in the left half is ultimately spliced ​​together with a scan of the molars (or molar region if molars are missing) in the right half. For canine to canine separations, the 3D surface on the distal half of the dental arch may have a depth of approximately 30 mm or less. For anterior to molar separations or canine to molar separations, the distal half of the dental arch may have a depth of approximately 30 mm or less. These diagonal views can also improve longitudinal errors (e.g., errors in jaw length), which can improve orthodontic treatment.

[0045] In an embodiment, the intraoral scanner has a field of view (FOV) with a focal depth greater than that of a conventional intraoral scanner. For example, embodiments of the present disclosure may be implemented by an intraoral scanner with a large focal depth that can detect 3D surfaces up to 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, or 90 mm from the probe of the intraoral scanner. For example, in some specific applications of the present disclosure, a device for intraoral scanning is provided, the device comprising an elongated handheld stick with a probe at a distal end. During scanning, the probe may be configured to enter the oral cavity of the subject. One or more light projectors (e.g., microstructured light projectors) and one or more cameras (e.g., microcameras) may be coupled to a rigid structure disposed within the distal end of the probe. Each light projector uses a light source such as a laser diode to transmit light. One or more structured light projectors may be configured to project a light pattern defined by a plurality of projector lights when the light source is activated. Each camera may be configured to capture a plurality of images that depict at least a portion of the projected light pattern on the intraoral surface. In some applications, the light projector may have an illumination field of at least 45 degrees. Optionally, the illumination field can be less than 120 degrees. For structured light projectors, each structured light projector can also include a pattern generating optical element. The pattern generating optical element can generate a light pattern using diffraction and / or refraction. In some applications, the light pattern can be a distribution of discrete, unconnected light spots. Optionally, when a light source (e.g., a laser diode) is activated to emit light through the pattern generating optical element, the light pattern maintains a distribution of discrete, unconnected spots on all planes located up to a threshold distance (e.g., 30 mm, 40 mm, 60 mm, etc.) from the pattern generating optical element. Each camera includes a camera sensor and an objective optical device including one or more lenses.

[0046] In some applications, to improve image capture of an intraoral scene under structured light illumination without using contrast enhancement means (e.g., coating the teeth with opaque powder), a distribution of discrete, unconnected light spots (e.g., as opposed to lines) can provide an improved balance between increasing pattern contrast and maintaining the amount of useful information. In some applications, the unconnected light spots have a uniform (e.g., unchanging) pattern. In general, denser structured light patterns can provide more surface sampling, higher resolution, and better stitching of corresponding surfaces obtained from multiple scan frames. However, overly dense structured light patterns may lead to more complex correspondence problems because of the large number of spots for which the correspondence problem is solved. In addition, denser structured light patterns may have lower pattern contrast due to more light in the system, which may be caused by a combination of: (a) stray light reflected from the somewhat shiny surface of the teeth and may be picked up by the camera, and (b) percolation, that is, some light enters the tooth, reflects along multiple paths within the tooth, and then leaves the tooth from many different directions. As further described below, methods and systems for solving the correspondence problem presented by the distribution of discrete, unconnected light spots are provided. In some applications, the discrete, unconnected spots from each projector may be uncoded.

[0047] In some embodiments, one or more of the light projectors are not structured light projectors. For example, one or more of the light projectors may be non-structured light projectors, which may project coherent and / or incoherent light, such as white light or near infrared (NIRI) light. It should be understood that the embodiments described herein with reference to structured light and structured light projectors also apply to combinations of structured light and structured light projectors with non-structured light and non-structured light projectors.

[0048] In some applications, the field of view of each camera can be at least 45 degrees, for example, at least 80 degrees, for example, 85 degrees. Optionally, the field of view of each camera can be less than 120 degrees, for example, less than 90 degrees. The fields of view of each camera can together form the field of view of the intraoral scanner. In any case, the fields of view of each camera can be the same or different. Similarly, the focal lengths of each camera can be the same or different. As used herein, the term "field of view" of each camera refers to the diagonal field of view of each camera. In addition, each camera can be configured to focus on an object focal plane located at a threshold distance from the corresponding camera sensor (e.g., up to 10mm, 20mm, 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, etc.). As the distance increases, the accuracy of the position of the detected surface decreases. In one embodiment, beyond the threshold distance, the accuracy is lower than the accuracy threshold. Similarly, in some applications, the illumination field of each light projector (e.g., a structured light projector and / or an unstructured light projector) can be at least 45 degrees, and optionally less than 120 degrees. The large field of view (FOV) of the intraoral scanner, achieved by combining the respective fields of view of all cameras, can improve accuracy due to a reduction in the amount of image stitching errors (compared to conventional scanners that typically have a FOV of 10-20 mm in the x-axis and y-axis and a capture depth of approximately 0-15 or 0-25 mm), particularly in edentulous areas where the gingival surface is smooth and sharp high-resolution 3D features may be rare. The intraoral scanner having a larger FOV causes large smooth features (e.g., the overall curve of the tooth) to appear in each image frame, which improves the accuracy of stitching the respective surfaces obtained from multiple such image frames.

[0049] In some applications, the total combined FOV of the individual cameras (e.g., of an intraoral scanner) is between about 20 mm and about 50 mm along the longitudinal axis of the elongated handheld wand, and about 20-60 mm (or 20-40 mm) on the z-axis, where the z-axis can correspond to depth. In other applications, the field of view can be about 20 mm, about 25 mm, about 30 mm, about 35 mm, or about 40 mm along the longitudinal axis and / or at least 20 mm, at least 25 mm, at least 30 mm, at least 35 mm, at least 40 mm, at least 45 mm, at least 50 mm, at least 55 mm, at least 60 mm, at least 65 mm, at least 70 mm, at least 75 mm, or at least 80 mm on the z-axis. In some embodiments, the combined field of view can vary with depth (e.g., with scanning distance). For example, at a scanning distance of about 4 mm, the field of view can be about 20 mm along the longitudinal axis, while at a scanning distance of about 20-50 mm, the field of view can be about 30 mm or less along the longitudinal axis. If most of the motion of the intraoral scanner is done relative to the long axis (e.g., longitudinal axis) of the scanner, then the overlap between scans may be large. In some applications, the field of view of the combined camera is discontinuous. For example, the intraoral scanner may have a first field of view separated from a second field of view by a fixed interval. For example, the fixed interval may be along the longitudinal axis of an elongated handheld wand.

[0050] In some embodiments, the large FOV of the intraoral scanner improves the accuracy of the depth of the detected 3D surface. For example, the accuracy of the depth measurement of the detected 3D surface can be based on the longitudinal distance between two cameras or between the light projector and the camera, which can represent the triangulation reference line distance. In embodiments, the cameras and / or light projectors can be spaced apart in a configuration that provides improved accuracy in depth measurement for 3D surfaces having a depth of, for example, up to 30 mm, up to 40 mm, up to 50 mm, up to 60 mm, etc.

[0051] In some applications, a method for generating a digital three-dimensional (3D) model of an intraoral surface is provided. The 3D model may be a point cloud from which an image of the three-dimensional intraoral surface may be constructed. The resulting image of the 3D model, while generally displayed on a two-dimensional screen, contains data related to the three-dimensional structure of the scanned 3D surface and can therefore generally be manipulated to display the scanned 3D surface from different views and perspectives. In addition, the data from the three-dimensional model may be used to create a physical three-dimensional model of the scanned 3D surface. As described above, the 3D model may be a 3D model of a dental arch, and the 3D model of the dental arch may have a dental arch width (e.g., intermolar width) with high accuracy (e.g., in some embodiments, with an error of approximately 20 microns or less).

[0052] Turning now to the accompanying drawings, Figure 1AA collection of scans 8 and 10A-10F of an edentulous dental arch 6 having four scan volumes 15, 20, 25, 30 according to an embodiment of the present disclosure is shown. In an embodiment, each of the scan volumes 15-30 can be attached to a separate dental implant. Each scan volume 15-30 can be a 3D structure with a known shape or geometry. Many scans 8, 10A-10F of the dental arch 6 can be generated. In the example shown, six occlusal scans 10 are shown, and one buccal scan 8 is shown. However, generally to fully scan the dental arch, more scans will be generated, including, for example, buccal scans, lingual scans, and occlusal scans. The scans 8, 10A-10F are stitched together to generate a virtual 3D model of the dental arch 6. The centers of the scans 10A-10F are represented by points 32, and the lines 35 between these points represent the links between the scans that have been registered together. Each registration of one scan with another includes a certain level of error. Conventionally, many such links are required to span from one quadrant of the dental arch (e.g., from scan volume 15) to another quadrant of the dental arch (e.g., to scan volume 30). Although each individual error associated with a link between two scans is small, the cumulative error between the distant scans connected by many links may be clinically significant. For example, the relative distance between scan volume 15 and scan volume 30 may have an error of 200-300 microns. Therefore, the determined arch width of the dental arch may have an error of approximately 200-300 microns. In order to reduce the distance error between distant scans (e.g., scans on different quadrants of the dental arch), and in order to reduce the error in the calculated arch width, one or more scans 8 can be generated that include at least features of a first surface of a first scan volume 15 and a second surface of scan volume 30. Such scans are implemented in the embodiments described herein. Including such scans 8 greatly improves the accuracy of the distance between scan volume 15 and scan volume 30, and also greatly improves the accuracy of the calculated arch width of the dental arch 6. For example, without scan 8, in the simplified example shown, the number of links connecting scan 10A to scan 10F is five. However, by adding scan 8, the number of links connecting scan 10A to scan 10F is two (one link from scan 10A to scan 8 and one link from scan 8 to scan 10F). Similarly, when scan 8 is included, the number of links connecting scan 10A to scan 10E is reduced from four to three in the example shown. In addition, by showing two scan volumes in scan 8, a more accurate estimate of the distance between the two scan volumes can be determined.

[0053] Figure 1BA series of transformations T1-2, T2-3, T3-4 to T90-91, T91-92, T92-93 for registering intraoral scans S1, S2, S3, S4 to S90, S91, S92, S93 of a dental arch according to an embodiment of the present disclosure are shown. As shown, there are many scans S1-S93 (e.g., hundreds of scans), many of which overlap at least partially with multiple other scans. The transformations include transformations between scans that are adjacent in time (e.g., T1-2, T2-3, T3-4, etc.) and transformations between scans that are not adjacent in time but at least partially overlap (e.g., T1-3, T90-92). There may be six degrees of freedom between any pair of scans, and the transformations T1-2 to T92-93 between each pair of overlapping scans (e.g., translations on three axes and rotations around three axes) can be calculated in each of the six degrees of freedom. Transformations T1-2 to T92-93 provide information about how to position and orient the scan relative to another overlapping scan. In addition, a transformation set can provide information about how to position and orient any scan to any other scan. For example, to know how to position scan S1 relative to scan S4, the system traverses the transformation set (e.g., T1-2, T2-3, and T3-4) between S1 and S4. Transformation chains are generally longer, more complex, and denser than the simplified transformation chain shown. In addition, there are generally dense connections, which means that for a given scan, connections exist not only between the scans immediately before and after in time, but also to any scan that has a geometric overlap with the given scan (e.g., including transformations T1-3 and T90-92). As described above, each transformation between scan pairs introduces a small amount of error. Therefore, the cumulative error between S1 and S93 may be relatively large. However, in an embodiment, a scan may include representations of two parts of the jaw at once. Such a scan is represented by lines T1-92 and T2-93. This scan including data of features on the proximal side of the jaw and features on the distal side of the jaw greatly reduces the cumulative error that may occur between, for example, S1 and S93.

[0054] In some embodiments, a first intraoral scan set is generated for one portion of a dental arch (e.g., the left side of the dental arch), and a second intraoral scan set is generated for another portion of the dental arch (e.g., the right side of the dental arch). However, not enough scans may have been captured to enable the system to accurately register or stitch the first intraoral scan set with the second intraoral scan set. In embodiments, this situation can be avoided based on one or more intraoral scans that include both representations of teeth and / or other objects (or portions thereof) in the first portion of the dental arch and representations of teeth and / or other objects (or portions thereof) in the second portion of the dental arch, as described in detail herein. A first 3D surface of the first portion of the dental arch can be generated from the first intraoral scan set, and a second 3D surface of the second portion of the dental arch can be generated from the second intraoral scan set. Even if there are not enough scans to generate a 3D surface of an intermediate region between the first 3D surface and the second 3D surface, the first intraoral scan set (and / or the first 3D surface) can be registered with the second intraoral scan set (and / or the second 3D surface) in a common reference frame using one or more intraoral scans that depict both the surface on the first portion of the dental arch and the surface on the second portion of the dental arch. This may enable a user to scan a first area of ​​a dental arch, then scan a second area of ​​the dental arch that does not overlap with the first area of ​​the dental arch, and generate 3D surfaces of the first and second areas of the dental arch without discarding the intraoral scans because the scans cannot be registered with each other. In embodiments, intraoral scans depicting two non-adjacent or otherwise non-connected areas of a dental arch may be used to register the otherwise non-connected intraoral scans together, thereby producing two non-connected 3D surfaces having known positions and orientations relative to each other (e.g., surfaces of non-adjacent teeth and / or teeth on opposite sides of a dental arch).

[0055] Figure 1C A flowchart of a method 101 for generating a virtual 3D model of a dental arch according to an embodiment of the present disclosure is shown. The method 101 may be performed by a processing logic including hardware (e.g., circuits, dedicated logic, programmable logic, microcode, etc.), software (e.g., instructions running on a processing device), or a combination thereof. In one embodiment, the processing logic is Figure 3 In some embodiments, some aspects of method 101 may be performed by an intraoral scanner (e.g., Figure 3 350), while other aspects of method 101 are performed by a computing device operably coupled to the intraoral scanner (e.g., Figure 3 The computing device 305 is executed by the computing device 305 of the present invention. The computing device may be a local computing device connected to the intraoral scanner via a wired connection or via a wireless connection. Alternatively, the computing device may be a remote computing device connected to the intraoral scanner or a local computing device via a network (e.g., the Internet and / or an intranet), which in turn is connected to the intraoral scanner.

[0056] At box 105 of method 101, processing logic receives multiple intraoral scans of a dental arch. Each intraoral scan may include image data generated by multiple cameras of the intraoral scanner. In an example, two or more cameras of the intraoral scanner may each generate an intraoral image, and the multiple intraoral images may be combined based on the known positions and orientations of the corresponding two or more cameras to form an intraoral scan. In one embodiment, each intraoral scan may include captured spots projected onto an area of ​​the dental arch by one or more structured light projectors. For example, one or more structured light projectors may be driven to project a distribution of discrete, unconnected spots of light onto an intraoral surface, and the cameras may be driven to capture the projected images. The images captured by each camera may include at least one spot. The images generated by each camera at a particular time together may form an intraoral scan. In some embodiments, non-structured light (e.g., incoherent light or white light and / or near infrared light) is also used to illuminate the dental arch.

[0057] Each camera may include a camera sensor having an array of pixels, and for each pixel there is a corresponding ray in 3D space originating from the pixel, directed toward the object being imaged; each point along a particular one of these rays, when imaged on the sensor, will fall on its corresponding corresponding pixel on the sensor. As used throughout this application, the term used for this is "camera ray". Similarly, for each projected spot from each projector, there is a corresponding projector ray. Each projector ray corresponds to a corresponding path of pixels on at least one camera sensor, i.e., if the camera sees a spot projected by a particular projector ray, then the spot must be detected by a pixel on a particular pixel path corresponding to the particular projector ray. The values ​​of the camera ray (a) corresponding to each pixel on the camera sensor of each camera and the values ​​of the projector ray (b) corresponding to each projected spot from each projector can be stored as calibration data, as described below.

[0058] The dentist may have performed an intraoral scan of the dental arch to generate multiple intraoral scans of the dental arch. This may include performing an intraoral scan of part or all of the mandibular arch or the maxillary arch, or performing a partial or full scan of both dental arches. Performing the intraoral scan may include projecting a pattern of discrete, non-connected spots onto the intraoral surface of the patient using one or more light projectors disposed in a probe at a distal end of the intraoral scanner, wherein the pattern of discrete, non-connected spots is non-encoded. Performing the intraoral scan may also include capturing multiple scans or images of the projected pattern of non-connected spots using two or more cameras disposed in the probe.

[0059] At block 110, processing logic determines a first depth of a first intraoral 3D surface in a first intraoral scan of the plurality of intraoral scans. The first depth may be determined using a correspondence algorithm and stored calibration values. The stored calibration values ​​may associate camera rays corresponding to pixels on a camera sensor of each of the plurality of cameras with the plurality of projector rays.

[0060] The processing logic can run a correspondence algorithm using the stored calibration values ​​to identify the three-dimensional position of each projected spot on the surface of the scanned 3D surface (e.g., the first intraoral 3D surface). For a given projector light, the processor "looks" at the corresponding camera sensor path on one of the cameras. Each detected spot along the camera sensor path will have a camera light that intersects with the given projector light. The intersection defines a three-dimensional point in space. Then, the processor searches in the camera sensor path corresponding to the given projector light on other cameras and identifies how many other cameras also detect spots whose camera light intersects with the three-dimensional point in space on their corresponding camera sensor paths corresponding to the given projector light. As used throughout this application, if two or more cameras detect spots whose corresponding camera light intersects with the given projector light at the same three-dimensional point in space, the cameras are considered to "agree" that the spots are located at the three-dimensional point. Therefore, the processor can identify the three-dimensional position of the projected light pattern based on the two or more cameras agreeing that there is a projected light pattern of projector light at certain intersections. The process is repeated for additional spots along the camera sensor path, and the spot with which the greatest number of cameras "agrees" is identified as the spot being projected onto the surface from a given projector ray. Thus, the three-dimensional position on the surface is calculated for that spot, including the depth of that spot. Thus, the depth of the first intra-oral 3D surface can be determined (which can include the depths of a plurality of different points on the surface of the first intra-oral 3D surface). In one embodiment, the first depth of the first intra-oral 3D surface is approximately 0-5 mm.

[0061] Once the position on the surface is determined for a particular spot, the projector ray that projects that spot and all camera rays corresponding to that spot can be removed from consideration, and the correspondence algorithm can be run again for the next projector ray. This can be repeated until the depths of many or all spots are determined. Ultimately, the identified three-dimensional position can be used to generate a digital three-dimensional model of the intraoral surface.

[0062] At box 120, processing logic determines a second depth of a second intraoral 3D surface in the first intraoral scan. The second depth may be determined using a correspondence algorithm and stored calibration values. In one embodiment, the second depth of the second intraoral 3D surface is about 40-90 mm. Alternatively, the second depth may be about 10 mm or more, about 20 mm or more, about 30 mm or more, or some other depth value. For example, the first intraoral 3D surface may be a first tooth or a first scan volume on a first half of a dental arch, which may have a depth of about 0-30 mm, or 5-30 mm, or 10-35 mm, or 10-20 mm, etc., from a camera of an intraoral scanner. The second intraoral 3D surface may be a second tooth or a second scan volume on a second half of a dental arch, which may have a depth of about 40-90 mm, or 35-80 mm, or 40-60 mm, or 31-80 mm, etc. In one embodiment, the distance between the first 3D surface and the second 3D surface is greater than 30 mm. For a child's jaw, a first intraoral 3D surface on a first half of the dental arch (e.g., a first tooth or a first scan volume) can have a depth of approximately 0-20 mm, while a second intraoral 3D surface on a second half of the dental arch (e.g., a second tooth or a second scan volume) can have a depth of approximately 21-40 mm. For example, the first intraoral scan can include a buccal view of the first intraoral 3D surface and can include a lingual view of the second intraoral 3D surface. Since the first intraoral 3D surface and the second intraoral 3D surface are captured by a single intraoral scan, a determined distance between the first intraoral 3D surface and the second intraoral 3D surface can be determined and fixed. This fixed distance can then be used to improve the accuracy of the intermolar width in the 3D model generated from the intraoral scan.

[0063] In one embodiment, at box 112, the correspondence algorithm is run using a depth threshold. For example, the depth threshold may be 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, or other values. In an embodiment, the correspondence algorithm may be run multiple times, each time using a different depth threshold. The correspondence algorithm may discard or filter out from consideration any possible depth values ​​where the point is greater than the depth threshold. Generally speaking, most or all depth values ​​will be less than the depth threshold. By not considering depth values ​​where the point is greater than the depth threshold, the depth calculations for the spots may be significantly reduced, which may speed up the operation of the correspondence algorithm.

[0064] For some intraoral scans, for example, those that capture points or 3D surfaces on the proximal half of the dental arch and additional points or 3D surfaces on the distal half of the dental arch, there may be points whose depth values ​​are greater than the threshold. Therefore, at box 122, the correspondence algorithm can be rerun without the depth threshold. Running the correspondence algorithm with the depth threshold may have been able to detect the depth of the spots on the first intraoral 3D surface, but may have excluded the detection of the depth of the spots on the second intraoral 3D surface. Therefore, by rerunning the correspondence algorithm without using the depth threshold, those spots that depict the second intraoral 3D surface can be reconsidered and their depths greater than the depth threshold can be determined. In some embodiments, after running the correspondence algorithm with the depth threshold at box 112, the depths of all spots (or a threshold number of spots) are determined, and the operations of boxes 120 and 122 are not performed. Alternatively, in some embodiments, it is determined at the end of box 110 or 112 that there are remaining spots with undetermined depths, and the operations of boxes 120 and / or 122 can be performed.

[0065] In one embodiment, at box 114, the processing logic determines a first correspondence between a first detected spot detected by the first camera and a first projected spot projected by a first light projector having a first distance from the first camera. For example, the first correspondence can be determined based on running the correspondence algorithm at box 112. In one embodiment, at box 124, the processing logic also determines a second correspondence between a second detected spot detected by the first camera or the second camera and a second projected spot projected by a second light projector having a second distance from the first camera or the second camera. The second distance between the first camera or the second camera and the second light projector can be greater than the first distance between the first camera and the first light projector. In the example, since the first intraoral 3D surface is closer to the camera of the intraoral scanner than the second intraoral 3D surface, the first intraoral 3D surface can be within the FOV of a different pair of camera and light projector than the second intraoral 3D surface. This will refer to Figure 5B Described and shown in more detail.

[0066] In some embodiments, a first depth of a first intraoral 3D surface and a second depth of a second intraoral 3D surface are determined without using structured light. For example, non-structured light or white light may be used to illuminate the oral cavity during an intraoral scan. Multiple cameras may capture images of the same intraoral 3D surface scanned intraorally, and stereo imaging techniques may be used to determine the depths of these intraoral 3D surfaces. In such embodiments, at box 117, processing logic may triangulate a first depiction of the first intraoral 3D surface captured by the first camera with a second depiction of the first intraoral 3D surface captured by the second camera. The second camera may be separated from the first camera by a first distance. Triangulation may be performed to determine the first depth of the first intraoral 3D surface. At box 128, processing logic may additionally triangulate a first depiction of the second intraoral 3D surface captured by the first camera or the third camera with a second depiction of the second intraoral 3D surface captured by the fourth camera, the fourth camera being separated from the first camera or the third camera by a second distance. The second distance may be greater than the first distance. In an example, because the first intraoral 3D surface is closer to the camera of the intraoral scanner than the second intraoral 3D surface, the first intraoral 3D surface may be within the FOV of a different pair of cameras than the second intraoral 3D surface.

[0067] Operations 110 - 120 may be performed for each of the remaining intra-oral scans of the plurality of received intra-oral scans.

[0068] At block 130, processing logic stitches together the multiple intraoral scans. This may include registering a first intraoral scan to one or more additional intraoral scans using overlapping data between the individual intraoral scans. In one embodiment, performing scan registration includes capturing 3D data for various points of the surface in the multiple intraoral scans and registering the intraoral scans by calculating a transformation between the intraoral scans. The intraoral scans may then be integrated into a common reference frame by applying an appropriate transformation to the points of each registered intraoral scan.

[0069] In one embodiment, surface registration is performed on adjacent or overlapping intraoral scans (e.g., consecutive frames of an intraoral video). A surface registration algorithm is performed to register two or more intraoral scans with overlapping scan data, which primarily involves determining a transformation that aligns one scan with another. In an embodiment, each registration between scans can be accurate to within 10-15 microns. Surface registration can be performed using, for example, an iterative closest point (ICP) algorithm, which can involve identifying multiple points in multiple scans (e.g., point clouds), fitting a surface to the points of each scan, and matching the points of overlapping scans using a local search around the points. Francois Pomerleau et al., "Comparing ICP Variants on Real-World Data Sets," 2013, describes some examples of ICP algorithms that can be used, which is incorporated herein by reference. For example, other techniques that can be used for registration include techniques based on determining point-to-point correspondences using other features and minimizing point-to-surface distances. In one embodiment, scan registration (and stitching) is performed as described in U.S. Patent No. 6,542,249, entitled "Three-dimensional Measurement Method and Apparatus," issued April 1, 2003, which is incorporated herein by reference. Other scan registration techniques may also be used.

[0070] Surface registration may include sequentially stitching in-plane scan pairs, and performing a global optimization that minimizes all pairs of positions together and / or minimizes all points from all scans from one scan to another. Thus, if scan-to-scan registration (e.g., using ICP) searches in 6 degrees of freedom (3 translations and 3 rotations), optimizing the distance of all points from one scan to another, then a global optimization of 11 scans will search in (11-1)x6=60 degrees of freedom of all scans relative to all other scans, while minimizing a certain distance between all scans. In some cases, this global optimization should weight different errors (e.g., edges and / or far points of a scan may be given lower weights for better robustness).

[0071] Special situations may arise when features (e.g., lines or points) smaller than a surface are to be registered to a surface. Assume that feature points of a surface (e.g., corners of a scanned volume) are captured in one scan, and a surface including the feature points is captured in another scan. In ICP, points from one surface to another are minimized, but the point correspondence step size of ICP may change in each iteration. In a variant algorithm, a fixed correspondence may be found between feature points (e.g., features of a surface) and surface points (e.g., surfaces), and an attempt is made to minimize it together with all surface minimizations. Since the feature may be a single point or a few points, and may be overwhelmed by most of the surface points, the error of the feature point will receive a higher weight in the global error. In an embodiment, a single scan may capture a first surface (e.g., a proximal tooth or buccal surface of a scanned volume) and may additionally capture a second surface (e.g., a distal tooth or lingual surface of a scanned volume) or features of the second surface (e.g., one or more points and / or lines). This information may be used to perform registration of the first surface with other scanned surfaces and to perform registration of the second surface (or features of the second surface) with other scanned surfaces.

[0072] At box 135, processing logic generates a virtual 3D model of the dental arch from the intraoral scans. This may include integrating data from all intraoral scans into a single 3D model by applying appropriately determined transformations to each scan. For example, each transformation may include rotations about one to three axes and translations in one to three planes.

[0073] A fixed distance between a first intraoral 3D surface and a second intraoral 3D surface determined from the first intraoral scan can be included in the virtual 3D model, which can greatly improve the accuracy of the intraoral width of the 3D model of the dental arch, as opposed to a dental arch 3D model generated using conventional intraoral scans, which do not include image data of 3D surfaces on both the proximal and distal halves (quadrants of the jaw) of the dental arch in a single scan.

[0074] For some applications, there is at least one uniform light projector (also referred to as an incoherent light projector) that projects incoherent light. In an embodiment, the uniform light projector emits white light onto the object being scanned. At least one camera uses the illumination from the uniform light projector to capture a two-dimensional color image of the object. The processing logic can run a surface reconstruction algorithm that combines at least one image captured using the illumination from the structured light projector with one or more images captured using the illumination from the uniform light projector to generate a digital three-dimensional image of the intraoral three-dimensional surface. The combination of using structured light and uniform illumination enhances the overall capture of the intraoral scanner and can help reduce the number of options that the processing logic needs to consider when running the correspondence algorithm. In one embodiment, stereo vision technology, deep learning technology (e.g., using a convolutional neural network) and / or simultaneous localization and mapping (SLAM) technology can be used with scan data from structured light and scan data from incoherent light to improve the accuracy of the determined 3D surface and / or reduce the number of options that the processing logic needs to consider when running the correspondence algorithm.

[0075] For some applications, there is at least one near infrared light projector that projects near infrared and / or infrared light onto the object while the object is being scanned. At least one camera captures an image of the object using illumination from the near infrared light projector. Processing logic can run a surface reconstruction algorithm that combines at least one image captured using illumination from the structured light projector with one or more images captured using illumination from the near infrared light projector to generate a digital three-dimensional image of the intraoral three-dimensional surface. The combination of using structured light and near infrared illumination enhances the overall capture of the intraoral scanner and can help reduce the number of options that the processing logic needs to consider when running the correspondence algorithm. In one embodiment, stereo vision technology, deep learning technology (e.g., using convolutional neural networks) and / or simultaneous localization and mapping (SLAM) technology can be used with scan data from structured light and scan data from near infrared light to improve the accuracy of the determined 3D surface and / or reduce the number of options that the processing logic needs to consider when running the correspondence algorithm.

[0076] In some embodiments, structured light from a structured light projector, incoherent light from one or more incoherent light projectors, and near infrared light from one or more near infrared light projectors are used together.

[0077] In an embodiment, the scanned dental arch may include one or more areas (e.g., edentulous areas) that primarily or exclusively contain soft tissue. Conventionally, such edentulous areas may hinder or complicate a successful intraoral scanning operation of a patient because the soft tissue may lack defining distinctive features (e.g., geometric features) suitable for performing surface registration (i.e., the tissue contours may be too smooth to allow individual snapshots to be accurately registered with each other). For example, the soft tissue may not allow for accurate surface registration or surface shape measurements that can be used for scanning. The edentulous area may be part of a dental part that forms the focus of a patient-specific dental procedure. For example, a specific procedure may be planned for a dental part, and in some cases, an accurate depiction of a complete mandibular or maxillary arch (including an accurate intermolar width) may be desired to successfully perform a specific procedure. However, it is conventionally difficult to accurately determine the intermolar width (e.g., with an error of less than 100 microns). An embodiment is capable of generating an accurate 3D model of a dental arch (whose intermolar width has an error as low as 20 microns), even in the case of an edentulous dental arch. This accurate model can be used for both full-mouth denture treatments and full-mouth treatments without dental implants (including dentures supported by multiple implants).

[0078] The 3D model of the dental arch with improved accuracy provided in the embodiment can be used for restorative (restoration) procedures and orthodontic procedures. As a non-limiting example, dental procedures can be roughly divided into restorative (restoration) procedures and orthodontic procedures, and then further subdivided into specific forms of these procedures. The term restorative procedure refers in particular to any procedure involving the design, manufacture or installation of a denture at a tooth site in the oral cavity, or its real or virtual model, or the design and preparation of a tooth site for accommodating such a prosthesis. For example, a prosthesis may include any restoration (such as a crown, veneer, inlay, onlay and bridge) and any other artificial partial or full denture. The term orthodontic procedure refers in particular to any procedure involving the design, manufacture or installation of orthodontic elements at a tooth site in the oral cavity, or its real or virtual model, or the design and preparation of a tooth site for accommodating such an orthodontic element. These elements can be appliances, including but not limited to brackets and wires, retainers, transparent aligners or functional appliances. A specific procedure for which the embodiments of the present disclosure may be particularly useful is a full-to-four procedure. In a full-to-four procedure, the replacement of all teeth is supported by four dental implants. The full-on-four procedure is intended for the complete rehabilitation of edentulous patients or for restorative procedures for patients with severely broken teeth, decayed teeth, or teeth damaged due to gum disease. An accurate 3D model of the dental arch is particularly important for the full-on-four procedure, but is particularly difficult to obtain due to the lack of distinctive features on the patient's dental arch. The embodiments provided herein enable the generation of an accurate 3D model from an intraoral scanning session that produces an intraoral scan of the dental arch including four scan volumes, wherein the 3D model can have, for example, an intermolar width with an accuracy of + / -50μm (or + / -30μm, + / -20μm, or + / -10μm). This enables the full-on-four procedure to be performed with improved accuracy and reduced failure rate.

[0079] Some orthodontic treatments require changes in jaw width (i.e., intermolar width). Typically in conventional intraoral scanning systems, the planned change in jaw width may be less than the error associated with the intermolar width of the virtual 3D model of the scanned dental arch. In this case, it is difficult to determine whether the intermolar width complies with the treatment plan (e.g., whether the planned palatal expansion has been achieved). However, in an embodiment, the accuracy of the intermolar width is very high, with an error as low as 20 microns. Therefore, changes in intermolar width can be tracked over time during orthodontic treatment. In an example, an adult jaw may have a length of approximately 100 mm and a width of approximately 50-60 mm. The treatment plan may indicate that the jaw width (intermolar width) should be increased by 100 microns. In a system where the intermolar width error exceeds 100 microns, it may be challenging to determine whether a 100 micron palate expansion is successfully achieved after treatment. However, in the embodiments described herein, the palatal expansion amount can be determined and compared to the planned palatal expansion amount proposed in the treatment plan.

[0080] Figure 1D A flow chart of a method 150 for generating a virtual 3D model of a dental arch according to an embodiment of the present disclosure is shown. The method 150 may be performed, for example, at blocks 130 and / or 135 of the method 101. The method 150 may be performed by processing logic including hardware (e.g., circuits, dedicated logic, programmable logic, microcode, etc.), software (e.g., instructions running on a processing device), or a combination thereof. In one embodiment, the processing logic is Figure 3 The computing device 305.

[0081] At block 155 of method 150, processing logic determines intraoral scans that have overlapping data (e.g., pairs of intraoral scans, each intraoral scan depicting a particular intraoral 3D surface). At block 160, for each overlapping pair of intraoral scans, processing logic registers a first intraoral scan from the pair with a second intraoral scan from the pair in a common reference frame. A corresponding error may be associated with registering the first intraoral scan to the second intraoral scan, the corresponding error having a corresponding magnitude.

[0082] In some embodiments, each alignment between pairs of intraoral scans may have a certain level of inaccuracy, which may be on the order of about 10-15 microns. These alignment errors are generally accumulated as a 3D model of the dental arch is generated, so that the cumulative error in the width of the 3D model of the dental arch (e.g., the intermolar width) has an error on the order of 200-400 microns. A cost function may be applied to a combination of overlapping pairs of intraoral scans to determine the cumulative error. The cost function can be configured to optimize each individual alignment to minimize the cumulative error. In general, the same weight is applied to each alignment.

[0083] At block 165, processing logic weights the respective magnitudes of the respective errors of the overlapping intraoral scan pairs. The respective magnitudes associated with the overlapping scan pairs included in an intraoral image that includes a depiction of a first intraoral 3D surface in a first half of a dental arch and a depiction of a second intraoral 3D surface in a second half of the dental arch can be assigned a respective first weight that is higher than a respective second weight assigned to one or more other overlapping intraoral scan pairs (e.g., that do not depict both the first 3D surface and the second 3D surface).

[0084] At block 170, processing logic applies a cost function to the overlapping image pair to assign a specific error to a specific registration between the scan pair and determines a cumulative error. The cost function may use the weighted magnitudes to select a specific error to use for each individual registration. In an embodiment, the respective magnitudes of the respective errors modified by the respective first weights and the respective second weights are selected to minimize the cumulative error.

[0085] Figure 2AA flowchart of a method 200 for generating a virtual 3D model of a dental arch according to an embodiment of the present disclosure is shown. The method 200 may be performed by a processing logic including hardware (e.g., circuits, dedicated logic, programmable logic, microcode, etc.), software (e.g., instructions running on a processing device), or a combination thereof. In one embodiment, the processing logic is Figure 3 In some embodiments, some aspects of method 200 may be performed by an intraoral scanner (e.g., Figure 3 350), while other aspects of method 200 are performed by a computing device operably coupled to the intraoral scanner (e.g., Figure 3 The computing device 305) is executed.

[0086] At box 205 of method 200, processing logic may receive an indication that a dental prosthesis is to be manufactured for a patient (and / or that a particular orthodontic procedure or restorative procedure is to be performed). The dental prosthesis may be configured to be attached to at least a first dental implant and a second dental implant, which may be on an edentulous dental arch of the patient. In one embodiment, the procedure is an all-to-four procedure, and the dental prosthesis is to be attached to four dental implants on the dental arch. In the absence of identification of a particular procedure, a standard scanning procedure may be performed that may not take into account or emphasize particular intraoral scans, such as those depicting two scan volumes, each of which may be attached to a dental implant. Identification that a particular procedure is to be performed may result in execution of an alternative scanning procedure and cause method 200 to proceed.

[0087] The processing logic can identify spatial relationships suitable for scanning the dental sites so that complete and accurate image data can be obtained for the procedure in question. The processing logic can establish an optimal manner for scanning the dental arch. This can include determining specific intraoral scans that should be generated, wherein each specific intraoral scan should include a depiction of multiple specific scan volumes. In addition, the processing logic can calculate the optimal placement of the intraoral scanner to generate the specific intraoral scans. The processing logic can then identify one or more positions (e.g., optimal placement) and / or orientations at which the intraoral scanner is to be placed to the dentist to generate these intraoral scans. When recommending the location at which the intraoral scan should be generated to ensure that the scan registration will be successful, the processing logic can take into account the field of view (including depth of focus) of the intraoral scanner to be used.

[0088] The scanning protocol may be identified or determined by associating the type of scanner, its resolution, the capture area at the optimal spacing between the scanner head and the tooth surface with the target area, etc. The scanning protocol may include, for example, a series of scanning stations spatially associated with the tooth surface of the target area.

[0089] At box 210, processing logic receives an intraoral scan of an edentulous dental arch. In one embodiment, processing logic analyzes each received intraoral scan to determine whether any intraoral scan includes a depiction of two or more scan volumes. In one embodiment, if an intraoral scan is received that includes a depiction of two or more scan volumes, processing logic generates a notification for the user. This can include an auditory indication (e.g., a bang), a tactile indication, a visual indication (e.g., a message on a screen), and the like. In one embodiment, the scanning procedure to be performed includes a set of scans, each scan including a representation of a particular scan volume pair. A graphical user interface (GUI) can show each of these specified scans. As each such specified intraoral scan is received, the GUI can be updated to show that the particular scan has been received.

[0090] At block 215, processing logic determines whether any intraoral scans depict the first scan volume and the second scan volume. Processing logic may have identified a particular scanning station (with a particular position and orientation of the intraoral scanner) and that generating an intraoral scan at that particular scanning station may generate an intraoral scan depicting the first scan volume and the second scan volume. If no intraoral scans depicting the first scan volume and the second scan volume are identified, the method continues to block 220. If such intraoral scans depicting the first scan volume and the second scan volume are identified, the method continues to block 245.

[0091] At block 220, processing logic outputs instructions to position a probe of the intraoral scanner to generate an intraoral scan depicting the first scan volume and the second scan volume. This may include guiding a user to place the probe at a particular station (e.g., in a particular position and orientation) at block 222. For example, the user may be guided via a graphical user interface.

[0092] At box 225, processing logic may detect when the probe is in a particular position and orientation. At box 230, processing logic may automatically cause a first intra-oral scan to be generated when the probe is in a particular position and orientation. At box 235, processing logic receives a first intra-oral scan depicting a first scan volume and a second scan volume. In some embodiments, the first scan volume and the second scan volume are each on the same half of the dental arch (quadrant of the jaw). In some embodiments, the first scan volume and the second scan volume are on opposite halves of the dental arch (quadrants of the jaw).

[0093] In an embodiment, processing logic may determine a plurality of different stations from which intraoral scans should be generated. Each station may provide intraoral scans having depictions of different combinations of two scan volumes. For example, for an all-to-four procedure, a first station may provide an intraoral scan having depictions of a first scan volume and a second scan volume, a second station may provide an intraoral scan having depictions of a second scan volume and a third scan volume, and a third station may provide an intraoral scan having depictions of a third scan volume and a fourth scan volume. A fourth station may provide an intraoral scan having depictions of a second scan volume and a fourth scan volume. A fifth station may provide an intraoral scan having depictions of a first scan volume and a third scan volume. A sixth station may provide an intraoral scan having depictions of a first scan volume and a fourth scan volume. Processing logic may repeat the operations of blocks 215-235 for each station (e.g., for each target scan depicting a particular scan volume pair).

[0094] At box 245, processing logic stitches the intraoral scans together. At box 250, processing logic generates a virtual 3D model of the dental arch from the intraoral scans. Thus, method 200 detects when two or more scan volumes are represented in a single intraoral scan, and uses such an intraoral scan that includes a representation of the two or more scan volumes to determine the correct position and spacing between the scan volumes.

[0095] Figure 2B A flow chart of a method 252 for generating a virtual 3D model of a dental arch according to an embodiment of the present disclosure is shown. The method 252 may be performed by processing logic including hardware (e.g., circuits, dedicated logic, programmable logic, microcode, etc.), software (e.g., instructions running on a processing device), or a combination thereof. In one embodiment, the processing logic is Figure 3 In some embodiments, some aspects of method 252 may be performed by an intraoral scanner (e.g., Figure 3 350), while other aspects of method 252 are performed by a computing device operably coupled to the intraoral scanner (e.g., Figure 3 The computing device 305) is executed.

[0096] At box 255 of method 252, processing logic receives multiple intraoral scans of the dental arch. Each intraoral scan can include image data generated by multiple cameras of the intraoral scanner. In an example, two or more cameras of the intraoral scanner can each generate an intraoral image, and the multiple intraoral images can be combined based on the known positions and orientations of the corresponding two or more cameras to form the intraoral scan. The dentist may have performed an intraoral scan of the dental arch to generate multiple intraoral scans of the dental arch. This may include performing an intraoral scan of part or all of the mandibular arch or the maxillary arch, or performing a partial or full scan of both dental arches.

[0097] At box 260, processing logic determines that at least one intraoral scan of the plurality of intraoral scans includes a depiction of a first three-dimensional (3D) surface and a depiction of at least features of a second 3D surface, wherein in the at least one intraoral scan, the second 3D surface is separated from the first 3D surface by at least one intermediate 3D surface that is not shown. In the at least one intraoral scan, there may be a distance between the features of the first 3D surface and the second 3D surface. In one embodiment, the at least one intraoral scan includes a buccal view of the first 3D surface and a lingual view of at least features of the second 3D surface, which is not connected to the first 3D surface in the at least one intraoral scan. Although the first 3D surface and the second 3D surface are not connected in the at least one intraoral scan, it should be noted that the first 3D surface and the second 3D surface may be physically connected on the patient's jaw. However, the physical connection may not be shown in the intraoral scan. For example, the first 3D surface may be on the proximal quadrant of the dental arch and the second 3D surface may be on the distal quadrant of the dental arch, but the portion of the dental arch connecting the first 3D surface and the second 3D surface may not be shown. In one embodiment, the dental arch is an edentulous dental arch comprising a plurality of scanned volumes, the first 3D surface represents at least a portion of a first scanned volume of the plurality of scanned volumes, the at least one intermediate 3D surface represents a second scanned volume of the plurality of scanned volumes, and the second 3D surface represents at least a portion of a third scanned volume of the plurality of scanned volumes.

[0098] In one embodiment, the intraoral scanner that generates the intraoral scan can be as described in more detail below. In one embodiment, the intraoral scanner has multiple cameras with different focal depth ranges or settings. In one embodiment, the first intraoral scan is a buccal scan, and the first 3D surface and the second 3D surface are at different depths in the buccal scan (e.g., as described in reference to FIG. 1 ). Figure 1B For example, the maximum depth of the first 3D surface can be less than the minimum depth of the second 3D surface. In one embodiment, the plurality of intraoral scans are generated by an intraoral scanner having a depth of focus greater than 30 mm, wherein the first 3D surface has a depth less than 30 mm, and wherein the second 3D surface has a depth greater than 30 mm.

[0099] In embodiments, the accuracy of detected points and surfaces may decrease with increasing depth. Thus, the accuracy of the determined depth and / or position of the second 3D surface may be lower than the accuracy of the determined depth and / or position of the first 3D surface. In some embodiments, the second 3D surface is a swept volume having a known 3D geometry. Thus, the second 3D surface (or detected features of the second 3D surface) may be compared to the known geometry of the swept volume to determine that the 3D surface is a swept volume. The known geometry of the swept volume may then be used to improve the accuracy of the depth and / or position of the second 3D surface.

[0100] Alternatively, the first intraoral scan can be an occlusal scan, and the first 3D surface and the second 3D surface can have similar depths (e.g., can have a depth of less than 30 mm) but different x, y positions. In one embodiment, an intraoral scanner that generates the intraoral scan can be as described in more detail below. Alternatively, the intraoral scanner may not have a wide range of depth of focus, but may have a large FOV on the x, y axis. Such an intraoral scanner can use, for example, one or more cameras, a light projector, a fisheye camera, etc. to generate the scan. The FOV of the intraoral scanner can be a large FOV (e.g., including overlapping FOVs of multiple cameras) or can be two or more disconnected FOVs (e.g., including FOVs that do not overlap with two or more cameras that are laterally separated). In an example, the first intraoral scan can have a length of 30 microns, the first 3D surface can be at one extreme of the length, and the second 3D surface can be at a second extreme of the length (e.g., at the opposite end of the 3D scan). In one embodiment, a plurality of intraoral scans are generated by an intraoral scanner having a lateral field of view greater than 30 mm, wherein a first 3D surface is at a first side of the field of view, and wherein a second 3D surface is at a second side of the field of view.

[0101] At block 265, processing logic stitches the plurality of intraoral scans together. This may include registering at least one intraoral scan to one or more additional intraoral scans using overlapping data between the individual intraoral scans.

[0102] At box 270, processing logic generates a virtual 3D model of the dental arch from the intraoral scans. This may include integrating data from all intraoral scans into a single 3D model by applying appropriately determined transformations to each scan. For example, each transformation may include rotations about one to three axes and translations in one to three planes.

[0103] The distance between a first intraoral 3D surface and a second intraoral 3D surface determined from at least one intraoral scan can be included in the virtual 3D model, which can greatly improve the accuracy of the intraoral width of the 3D model of the dental arch, as opposed to a dental arch 3D model generated using a conventional intraoral scan (image data of 3D surfaces on both the proximal and distal halves (quadrants of the jaw) of the dental arch are not included in a single scan). Due to stitching together multiple intraoral scans other than at least one intraoral scan, a first number of links may exist between pairs of intraoral scans that connect a first 3D surface on a first quadrant of the dental arch to a second 3D surface on a second quadrant of the dental arch. Due to stitching together multiple intraoral scans including at least one intraoral scan, a second number of links may exist between pairs of intraoral scans that connect a first 3D surface on a first quadrant of the dental arch to a second 3D surface on a second quadrant of the dental arch. The second number of links is lower than the first number of links and results in improved accuracy of the virtual 3D model.

[0104] Figure 3 One embodiment of a system 300 for performing intraoral scanning and / or generating a virtual 3D model of a dental arch is shown. In one embodiment, the system 300 performs one or more operations of the above-described methods 101, 150, and / or 200. The system 300 includes a computing device 305, which can be coupled to an intraoral scanner 350 (also referred to as scanner 350) and / or a data storage 310.

[0105] The computing device 305 may include a processing device, a memory, a secondary storage, one or more input devices (e.g., such as a keyboard, a mouse, a tablet computer, etc.), one or more output devices (e.g., a display, a printer, etc.), and / or other hardware components. The computing device 305 may be connected to the data storage 310 directly or via a network. The network may be a local area network (LAN), a public wide area network (WAN) (e.g., the Internet), a private WAN (e.g., an intranet), or a combination thereof. In some embodiments, the computing device and the memory device may be integrated into the scanner to improve performance and mobility.

[0106] Data storage 310 may be an internal data storage, or an external data storage connected directly or via a network to computing device 305. Examples of network data storage include storage area networks (SANs), network attached storage (NASs), and storage services provided by cloud computing service providers. Data storage 310 may include a file system, a database, or other data storage arrangements.

[0107] In some embodiments, a scanner 350 for obtaining three-dimensional (3D) data of a dental region in a patient's mouth is also operably connected to the computing device 305. The scanner 350 may include a probe (eg, a handheld probe) for optically capturing a three-dimensional structure.

[0108] In some embodiments, the scanner 350 includes an elongated handheld wand comprising: a probe at a distal end of the handheld wand; a rigid structure disposed within the distal end of the probe; one or more structured light projectors coupled to the rigid structure (and optionally, one or more non-structured light projectors coupled to the rigid structure, e.g., incoherent light projectors and / or near infrared light projectors); and one or more cameras coupled to the rigid structure. In some applications, each light projector can have an illumination field of 45-120 degrees. Optionally, one or more light projectors can utilize a laser diode light source. In addition, the structured light projector can include beam shaping optics. In addition, the structured light projector can include pattern generating optics.

[0109] The pattern generating optical element can be configured to generate a distribution of discrete, unconnected light spots. When a light source (e.g., a laser diode) is activated to emit light through the pattern generating optical element, a distribution of discrete, unconnected light spots can be generated at all planes located between specific distances from the pattern generating optical element (e.g., 1-30 mm, 1-50 mm, 1-80 mm, etc.). In some applications, the pattern generating optical element generates the distribution using diffraction and / or refraction. Optionally, the pattern generating optical element has a light conversion efficiency of at least 90%.

[0110] For some applications, the light projectors and cameras are positioned so that each light projector faces an object placed in its illumination field outside the rod. Alternatively, each camera can face an object placed in its field of view outside the rod. Furthermore, in some applications, at least 20% of the discrete, unconnected light spots are in the field of view of at least one camera.

[0111] The scanner 350 can be used to perform an intraoral scan of a patient's mouth. The result of the intraoral scan can be a sequence of intraoral scans that have been discretely generated (e.g., by pressing a "generate scan" button of the scanner for each intraoral scan). Alternatively, the result of the intraoral scan can be one or more videos of the patient's mouth. The operator can start recording a video with the scanner 350 at a first position in the mouth, move the intraoral scanner 350 to a second position while taking the video, and then stop recording the video. In some embodiments, when the scanner identifies that it is at a specific station (e.g., at a specific position and orientation in the patient's mouth), recording can be started automatically. In either case, the scanner 350 can send discrete intraoral scans or intraoral videos (collectively referred to as scan data 335) to the computing device 305. Note that in some embodiments, the computing device can be integrated into the scanner 350. The computing device 305 can store the scan data 335 in the data store 310. Alternatively, the scanner 350 can be connected to another system that stores the scan data in the data store 310. In such an embodiment, the scanner 350 may not be connected to the computing device 305.

[0112] The scanner 350 can drive each of the one or more light projectors to project a distribution of discrete, unconnected light spots onto an intraoral three-dimensional surface. The scanner 350 can also drive each of the one or more cameras to capture an image, the image comprising at least one spot. Each of the one or more cameras can include a camera sensor, the camera sensor including a pixel array. The images captured together at a particular time can together form an intraoral scan. The intraoral scan can be transmitted to the computing device 305 and / or stored in the data storage 310 as scan data 335.

[0113] The computing device 305 may include an intraoral scanning module 308 for facilitating intraoral scanning and generating a 3D model of a dental arch from the intraoral scan. In some embodiments, the intraoral scanning module 308 may include a surface detection module 315 and a model generation module 325. The surface detection module 315 may analyze the received image data 335 to identify objects in the intraoral scan of the image data 335. The surface detection module may perform a correspondence algorithm on the intraoral scan to determine the depth of spots or points in the intraoral scan. The surface detection module 315 may access stored calibration data 330, which indicates (a) camera rays corresponding to each pixel on a camera sensor of each of one or more cameras, and (b) projector rays corresponding to each projected spot from each of one or more projectors, wherein each projector ray corresponds to a respective path of a pixel on at least one camera sensor. Using the calibration data 330 and the correspondence algorithm, the surface detection module 315 may (1) for each projector ray i, identify, for each detected spot j on the camera sensor path corresponding to the ray i, how many other cameras on their corresponding camera sensor paths corresponding to the ray i detected a corresponding spot k corresponding to the corresponding camera ray that intersects the ray i and the camera ray corresponding to the detected spot j. The ray i is identified as the particular projector ray that produced the detected spot j, for which the largest number of other cameras detected the corresponding spot k. The surface detection module 315 may also (2) calculate the corresponding three-dimensional position on the intra-oral three-dimensional surface at the intersection of the projector ray i and the corresponding camera rays corresponding to the detected spot j and the corresponding detected spot k. For some applications, running the correspondence algorithm further includes, after operation (1), removing, using a processor, the projector ray i and the corresponding camera rays corresponding to the detected spot j and the corresponding detected spot k from consideration, and running the correspondence algorithm again for the next projector ray i.

[0114] The model generation module 325 can perform surface registration between the intraoral scans (eg, the intraoral scans can be stitched together, as described above). The model generation module 325 can then generate a virtual 3D model of the dental arch from the registered intraoral scans, as described above.

[0115] In some embodiments, the intraoral scanning module 308 includes a user interface module 309 that provides a user interface that can display the generated virtual 3D model. In addition, the user interface module 309 can guide the user to position the probe of the scanner 350 in a specific position and orientation (e.g., a specific site) to generate a specific intraoral scan.

[0116] In some embodiments, at least one intraoral scan included in the scan data 335 includes features and / or 3D surfaces on a first side or first half of the dental arch, and additionally includes features and / or 3D surfaces on a second side or second half of the dental arch. To generate such an intraoral scan, the probe of the scanner 350 can be positioned at the lingual side of the proximal half of the dental arch. The probe of the scanner 350 can be oriented so that the longitudinal axis of the probe is approximately parallel to the plane of the dental arch, and so that the buccal side of the proximal half of the dental arch and the lingual side of the distal half of the dental arch are in the FOV of the scanner 350.

[0117] Figure 4A A single intraoral scan 412 of an edentulous dental arch 402 having a first scan volume 404, a second scan volume 406, a third scan volume 408, and a fourth scan volume 410 is shown. A probe 414 of an intraoral scanner (e.g., scanner 350) is positioned at the buccal side of the proximal half of the dental arch 402 and is oriented so that the longitudinal axis (x-axis) of the probe is approximately parallel to the plane of the dental arch, and the z-axis (depth) of the probe is approximately parallel to the plane of the dental arch. Thus, the buccal side of the first scan volume 404 and the lingual side of the fourth scan volume 410 are in the FOV of the probe 414. As shown, the probe 414 can have a FOV that generates the intraoral scan 412 including the first scan volume 404 and the fourth scan volume 410. The x-axis corresponds to the longitudinal axis of the probe 414, and the z-axis corresponds to the depth measured as a distance from the probe 414. The z-axis and x-axis of the intraoral scan 412 are shown, but the y-axis (entering the page) is not shown.

[0118] Figure 4B A single intraoral scan 440 of a dental arch 420 having an edentulous area is shown. The dental arch 420 includes a plurality of teeth, including tooth 422, tooth 424, tooth 426, tooth 428, tooth 430, tooth 432, and tooth 434. A probe 414 of an intraoral scanner (e.g., scanner 350) is positioned buccally on the proximal half of the dental arch 420 and oriented such that the longitudinal axis of the probe is substantially parallel to the plane of the dental arch (e.g., the xz plane) and such that the buccal sides of teeth 422, 424 and the lingual sides of teeth 426-434 are in the FOV of the probe 414. As shown, the probe 414 can have a FOV that generates an intraoral scan 440 that includes proximal teeth 422, 424 and distal teeth 426-434. The x-axis corresponds to the longitudinal axis of the probe 414 and the z-axis corresponds to a depth measured as a distance from the probe 414.

[0119] Figure 4C Shows Figure 4AMultiple intraoral scans of an edentulous dental arch 402. Each of the intraoral scans may have been generated by an intraoral scanner having a specific distance from the imaged tooth surface (e.g., from the dental arch). At the specific distance, the intraoral scan has a specific scan area and scan depth. The shape and size of the scan area generally depends on the scanner and is represented by a rectangle in this document. Each scan may have its own reference coordinate system and origin. Each intraoral scan may be generated by the scanner at a specific location (e.g., a scanning station). The location and orientation of a specific scanning station may be selected to generate a specific target scan (e.g., such as intraoral scan 412 and intraoral scans 450, 455, 460, etc.).

[0120] An intraoral scan 412, referred to as a buccal scan, may have been generated while a probe (not shown) of an intraoral scanner (e.g., scanner 350) is positioned at the buccal side of the proximal half of the dental arch 402 and oriented so that the longitudinal axis (x-axis) of the probe is generally parallel to the plane of the dental arch, and the z-axis (depth) of the probe is generally parallel to the plane of the dental arch. Thus, the buccal side of the first scan volume 432 and the lingual side of the fourth scan volume 438 are in the FOV of the probe. The z-axis and x-axis of the intraoral scan 412 are shown, but the y-axis is not shown (enter the page). Other intraoral scans (not shown) may also be generated with the x-axis and z-axis of the probe generally parallel to the plane of the dental arch.

[0121] A number of intraoral scans (including intraoral scans 450, 455, and 460) may also be obtained with the longitudinal axis of the probe approximately perpendicular to the plane of the dental arch and optionally the z-axis approximately perpendicular to the plane of the dental arch, which are referred to as occlusal scans. Thus, for intraoral scans 450, 455, 460, the x-axis and y-axis of the FOV of the scan are shown, but the z-axis of the scan is not shown. For intraoral scan 412 and each of intraoral scans 450, 455, 460, at least two scan volumes are represented. For example, first scan volume 404 and second scan volume 406 are included in intraoral scan 450, second scan volume 406 and third scan volume 408 are included in intraoral scan 455, third scan volume and fourth scan volume 410 are included in intraoral scan 460, and first scan volume 404 and fourth scan volume 410 are included in intraoral scan 412. In an embodiment, these intraoral scans may be stitched together to generate a very accurate virtual 3D model of dental arch 402.

[0122] In some embodiments, intraoral scans depicting two scan volumes may be given higher importance than other intraoral scans for building an accurate 3D model of the dental arch. This higher importance may be naturally achieved in certain algorithms because they include a large number of unique surfaces that can be used to perform accurate scan registration. In other embodiments, such intraoral scans may be detected and during optimization of the computed 3D model of the dental arch, these scans (or links / transformations including these scans) may be given higher weight than other intraoral scans.

[0123] Surface registration can be performed between each overlapping pair of scans (e.g., between intraoral scan 450 and intraoral scan 455, and between intraoral scan 455 and intraoral scan 460). For each surface registration operation, a 3D transformation can be calculated between the intraoral scan pair. The 3D transformation can be visually shown as a link between the two scans. For example, link 475 between intraoral scan 450 and intraoral scan 455 represents a first transformation, and link 480 between intraoral scan 455 and intraoral scan 460 represents a second transformation. Transformations such as between intraoral scan 412 and intraoral scan 450 and between intraoral scan 412 and intraoral scan 460 can also be calculated, but are not shown for clarity. When the entire jaw is scanned, many such transformations and links can be calculated, which can produce a chain of links that indirectly connects one side of the dental arch to the other side of the dental arch. Each link / transformation can have specific small errors associated with it, which can accumulate into large errors from side to side, resulting in large errors in the width between the molars. However, using an intraoral scan 412 that depicts both sides of the dental arch can significantly reduce the error in the intermolar width caused by the cumulative error from the combined link / transformation. Any error in the intermolar width included in the intraoral scan 412 can be based on the inaccuracy of the depth measurement of the distal side of the jaw (e.g., the fourth scan volume 410), and is much smaller than the cumulative inaccuracy caused by multiple links across the jaw. The distance between the first scan volume 404 (or other features on the proximal side of the jaw) and the fourth scan volume (or other features on the distal side of the jaw) can be fixed from the intraoral scan 412 and can directly provide the intermolar width or can be used to accurately calculate the intermolar width. Each scan can be considered a rigid body, and the distance between the 3D surfaces within the scan can be fixed during surface registration and / or the generation of the 3D model. When building a 3D model, the processing logic can search for the relative position that is most consistent with the distance initially determined or found during surface registration. This means optimizing the difference between the original transformation of the stitched scan and the final relative position of the scan determined for the 3D model. In some embodiments, processing logic may detect that some scans include data from both sides or halves of the dental arch and may prioritize these scans (eg, may provide greater weight to these scans or links including these scans during optimization).

[0124] Any inaccuracies in the depth measurement of the fourth scan volume (or other 3D surface with large depth) can be mitigated by using an intraoral scanner with a large baseline between the cameras (or between the camera and the light projector), as described below with reference to Figure 5B as described.

[0125] As discussed above, the intraoral scanners set forth in embodiments of the present disclosure may be used to generate an intraoral scan that includes scan data of nearby objects (e.g., objects such as teeth or portions of teeth in the proximal quadrant of a dental arch) and scan data of distant objects (e.g., objects such as teeth or portions of teeth in the distal quadrant of a dental arch). Such a scan that includes both a depiction of nearby objects on a dental arch and a depiction of distant objects on a dental arch may be used to greatly improve the accuracy of a surface registration that is performed to stitch scans of a dental arch together. For example, the scan may include surfaces of the buccal side of the mesial molar and the lingual side of the distal molar, the buccal side of the mesial molar and the lingual side of the distal premolar, the buccal side of the mesial molar and the lingual side of the distal incisor, the buccal side of the mesial premolar and the lingual side of the distal molar, the buccal side of the mesial premolar and the lingual side of the distal premolar, the buccal side of the mesial premolar and the lingual side of the distal incisor, the buccal side of the mesial incisor and the lingual side of the distal molar, the buccal side of the mesial incisor and the lingual side of the distal premolar, and / or the buccal side of the mesial incisor and the lingual side of the distal incisor.

[0126] Figure 4D-4J Some example intraoral scans according to embodiments of the present disclosure are shown, which show nearby teeth and distant teeth in a single scan, which can be used to improve the accuracy of surface registration. The example intraoral scans are generated using an intraoral scanner as described in the embodiments herein. In some example intraoral scans, a lingual view of one or more teeth, a buccal view of one or more teeth, and / or an occlusal view of one or more teeth are shown.

[0127] Figure 4D A scan of the buccal side of proximal teeth 481 (e.g., buccal premolars) is shown, which also shows the lingual side of distal teeth 482 (e.g., incisor to molars) on the opposite side of the jaw. The occlusal side of one or more distal teeth 482 is also shown.

[0128] Figure 4E A scan of the buccal side of the proximal teeth 483 (e.g., buccal incisors) is shown, which also shows the lingual side of the distal teeth 484 (e.g., lingual premolars and molars) on the opposite side of the jaw. The occlusal side of one or more distal teeth 484 is also shown.

[0129] Figure 4FA scan of an occlusal view of an incisor 485 (eg, a buccal incisor) on a first side of a dental arch is shown, which also shows a number of other teeth on the opposite side of the dental arch, such as a distal incisor 486. The occlusal side of one or more teeth is also shown.

[0130] Figure 4G A scan of a buccal view of an incisor 487 is shown, which also shows a lingual view of a molar 489 and a premolar 488. The occlusal side of one or more incisors 487, molars 489, and premolars 488 is also shown.

[0131] Figure 4H A scan of a buccal and / or occlusal view of the premolar 489 is shown, which also shows a lingual and / or occlusal view of the incisor 490 and premolar 491 on the opposite side of the jaw.

[0132] Fig. 4I A scan showing all teeth on the dental arch between and including the mesial incisors 492 and distal incisors 493 is shown.

[0133] Figure 4J A scan is shown showing the buccal side of the proximal teeth 494 and the lingual side of the distal teeth 495 , which are part of the same dental arch as the proximal teeth.

[0134] Reference now Figure 5A , which is a schematic diagram of an elongated handheld wand 20 for intraoral scanning according to some applications of the present disclosure. A plurality of light projectors 22 (e.g., including a plurality of structured light projectors and / or unstructured light projectors) and a plurality of cameras 24 are coupled to a rigid structure 26 disposed within a probe 28 at a distal end 30 of the handheld wand. In some applications, during intraoral scanning, the probe 28 enters the oral cavity of a subject.

[0135] For some applications, the light projector 22 is positioned within the probe 28 so that one or more light projectors 22 face a 3D surface 32A and / or a 3D surface 32B placed in the illumination field of the projector outside the handheld wand 20, rather than positioning the light projector at the proximal end of the handheld wand and illuminating the 3D surface by reflecting light from a mirror and then onto the 3D surface. Similarly, for some applications, the camera 24 is positioned within the probe 28 so that each camera 24 faces a 3D surface 32A, 32B placed in the camera's field of view outside the handheld wand 20, rather than positioning the camera at the proximal end of the handheld wand and observing the 3D surface by reflecting light from a mirror and into the camera. This positioning of the projector and camera within the probe 28 enables the scanner to have an overall large field of view while maintaining a low profile probe.

[0136] In some applications, the height H1 of the probe 28 is less than 15 mm, and the height H1 of the probe 28 is measured from the lower surface 176 (sensing surface) to the upper surface 178 opposite the lower surface 176, through which reflected light from the scanned 3D surface 32A, 32B enters the probe 28. In some applications, the height H1 is between 10-15 mm.

[0137] In some applications, the cameras 24 each have a large field of view β (beta) of at least 45 degrees (e.g., at least 70 degrees, for example, at least 80 degrees (e.g., 85 degrees)). In some applications, the field of view can be less than 120 degrees, such as less than 100 degrees, such as less than 90 degrees. In experiments conducted by the inventors, it was found that the field of view β (beta) of each camera between 80 and 90 degrees is particularly useful because it provides a good balance between pixel size, field of view and camera overlap, optical quality, and cost. The camera 24 may include a camera sensor 58 and an objective optical device 60 including one or more lenses. In order to achieve close-focus imaging, the camera 24 may focus at an object focal plane 50, which is located between 1 mm and 30 mm, such as between 4 mm and 24 mm, such as between 5 mm and 11 mm, such as 9 mm to 10 mm from the lens farthest from the camera sensor. The camera 24 may also detect 3D surfaces located at greater distances from the camera sensor, for example, 3D surfaces at 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, etc. from the camera sensor.

[0138] As described above, the large field of view achieved by combining the respective fields of view of all cameras can improve accuracy due to the reduction in the amount of image stitching errors, particularly in edentulous areas where the gingival surface is smooth and sharp high-resolution 3D features may be fewer. Having a larger field of view causes large smooth features (e.g., the overall curve of a tooth) to appear in each image frame, which improves the accuracy of stitching the respective surfaces obtained from multiple such image frames.

[0139] Similarly, light projectors 22 may each have a large illumination field α(alph) of at least 45 degrees, such as at least 70 degrees. In some applications, the illumination field α(alph) may be less than 120 degrees, such as less than 100 degrees.

[0140] For some applications, to improve image capture, each camera 24 has a plurality of discrete preset focus positions, at each focus position, the camera focuses at a corresponding object focal plane 50. Each camera 24 may include an autofocus actuator that selects a focus position from the discrete preset focus positions to improve a given image capture. Additionally or alternatively, each camera 24 includes an optical aperture phase mask that extends the depth of focus of the camera so that the image formed by each camera remains in focus at all 3D surface distances between 1 mm and 30 mm (e.g., between 4 mm and 24 mm, e.g., between 5 mm and 11 mm, e.g., 9 mm-10 mm) from the lens farthest from the camera sensor. In other embodiments, the image formed by one or more cameras may additionally remain in focus at greater 3D surface distances (e.g., up to 40 mm, up to 50 mm, up to 60 mm, up to 70 mm, up to 80 mm, or a maximum of 90 mm).

[0141] In some applications, the light projectors 22 and cameras 24 are coupled to the rigid structure 26 in a closely packed and / or alternating manner such that (a) a majority of each camera's field of view overlaps with an adjacent camera's field of view, and (b) a majority of each camera's field of view overlaps with an adjacent projector's illumination field. Optionally, at least 20% (e.g., at least 50%, e.g., at least 75%) of the projected light pattern is in the field of view of at least one camera at an object focal plane 50 that is located at least 4 mm from a lens that is farthest from the camera sensor. Due to the different possible configurations of the projectors and cameras, some projected patterns may never be seen in the field of view of any camera, and some projected patterns may be blocked from view by the 3D surfaces 32A, 32B as the scanner moves back and forth during scanning.

[0142] The rigid structure 26 may be a non-flexible structure to which the light projector 22 and the camera 24 are bonded to provide structural stability for the optics within the probe 28. Bonding all projectors and all cameras to a common rigid structure helps maintain the geometric integrity of the optics of each light projector 22 and each camera 24 under varying environmental conditions (e.g., under mechanical stresses that may be caused by a subject's mouth). In addition, the rigid structure 26 helps maintain a stable structural integrity and positioning of the light projector 22 and the camera 24 relative to each other. As further described below, controlling the temperature of the rigid structure 26 can help maintain the geometric integrity of the optics over a wide range of ambient temperatures when the probe 28 enters and exits the subject's mouth or when the subject breathes during scanning.

[0143] As shown, the 3D surface 32A and the 3D surface 32B are in the FOV of the probe 28 , wherein the 3D surface 32A is relatively close to the probe 28 and the 3D surface 32B is relatively far from the probe 28 .

[0144] refer to Figure 5B , showing Figure 5A 2A and a magnified view of a portion of the probe 28 and 3D surfaces 32A, 32B. As shown in the illustrated example, the probe 28 includes a first light projector 22A, a second light projector 22B, and a third light projector 22C. In addition, the probe 28 includes a first camera 24A, a second camera 24B, a third camera 24C, and a fourth camera 24D. The 3D surface 32A is in the FOV of the first camera 24A and the first light projector 22A. However, the 3D surface 32A is not in the FOV of the fourth camera 24D. The 3D surface 32B, which is farther away from the probe 28 than the 3D surface 32, is in the FOV of the first light projector 22A and the fourth camera 24D. The first distance (referred to as the baseline) between the first light projector 22A and the first camera 24A is less than the second distance (baseline) between the fourth camera 24D and the first light projector 22A. Therefore, the corresponding data of the first light projector 22A and the fourth camera 24D can be used to determine the depth of the 3D surface 32B more accurately than the corresponding data of the first light projector 22A and the first camera 24A.

[0145] Similarly, 3D surface 32A is in the FOV of first camera 24A and second camera 24B, but not in the FOV of fourth camera 24D. Therefore, image data from first camera 24A and second camera 24B can be used to determine the depth of 3D surface 32. 3D surface 32B is in the FOV of first camera 24A and fourth camera 24D. Therefore, image data from first camera 24A and fourth camera 24D can be used to determine the depth of 3D surface 32B. Since the distance (baseline) between first camera 24A and fourth camera 24D is greater than the distance between first camera 24A and second camera 24B, image data from first camera 24A and fourth camera 24D can be used to determine the depth of 3D surface 32B with improved accuracy.

[0146] Whether using a pair of cameras or a pair of cameras and a light projector, the accuracy of the triangulation used to determine the depth of 3D surfaces 32A and 32B can be roughly estimated by the following equation:

[0147]

[0148] Among them, z err is the depth error, p erris the basic image processing error (generally a sub-pixel error), z is the depth, f is the focal length of the lens, and b is the baseline (the distance between the two cameras when stereo imaging is used or the distance between the camera and the light projector when structured light is used). In an embodiment, the probe of the intraoral scanner is configured so that the maximum baseline between the two cameras or between the camera and the light projector is large and provides a high level of accuracy for triangulation.

[0149] Reference now Figure 6 , which is a diagram depicting various different configurations of the positions of the light projector 22 and the camera 24 in the probe 28 according to some applications of the present disclosure. Figure 6 is represented by a circle, and the camera 24 is Figure 6 Note that rectangles are used to represent cameras because typically each camera sensor 58 and field of view β (beta) of each camera 24 has an aspect ratio of 1:2. Figure 6 Column (a) shows a bird's eye view of various configurations of the light projector 22 and the camera 24. The x-axis labeled in the first row of column (a) corresponds to the central longitudinal axis of the probe 28. Column (b) shows a side view of the camera 24 from various configurations when viewed from a line of sight with the central longitudinal axis of the probe 28. Figure 6 Column (b) shows the cameras 24 positioned so that the optical axes 46 are at an angle of 90 degrees or less (e.g., 35 degrees or less) relative to each other. Column (c) shows side views of the cameras 24 in various configurations when viewed from a line of sight perpendicular to the central longitudinal axis of the probe 28.

[0150] Typically, the farthest end (towards Figure 6 in the positive x direction) and the closest end (towards Figure 6 The cameras 24 located at the most distal end (i.e., the negative x-direction in the probe 28) are positioned so that their optical axes 46 are slightly rotated inward relative to the next closest camera 24, for example, at an angle of 90 degrees or less (e.g., 35 degrees or less). The cameras 24 located more centrally (i.e., neither the most distal camera 24 nor the most distal camera 24) are positioned so that their optical axes 46 face directly outward from the probe, with their optical axes 46 being substantially perpendicular to the central longitudinal axis of the probe 28. It should be noted that in row (xi), the projector 22 is located at the most distal position of the probe 28, so the optical axis 48 of the projector 22 points inward, thereby allowing a large number of spots 33 projected from this particular projector 22 to be seen by more cameras 24.

[0151] Typically, the number of light projectors 22 in the probe 28 can range from two (e.g., Figure 6Typically, the number of cameras 24 in the probe 28 can range from four (e.g., as shown in rows (iv) and (v)) to seven (e.g., as shown in row (ix)). Note that Figure 6 The various configurations shown in are exemplary and non-limiting, and thus the scope of the present disclosure includes additional configurations not shown. For example, the scope of the present disclosure includes more than five projectors 22 located in the probe 28 and more than seven cameras located in the probe 28.

[0152] In an example application, a device for intraoral scanning (e.g., an intraoral scanner) includes an elongated handheld wand including a probe at a distal end of the elongated handheld wand, at least two light projectors disposed within the probe, and at least four cameras disposed within the probe. Each light projector may include at least one light source configured to generate light when activated and a pattern generating optical element configured to generate a light pattern when light is transmitted through the pattern generating optical element. Each of the at least four cameras may include a camera sensor and one or more lenses, wherein each of the at least four cameras is configured to capture a plurality of images depicting at least a portion of the projected light pattern on an intraoral surface. The at least two light projectors and most of the at least four cameras may be arranged in at least two rows, each row being approximately parallel to a longitudinal axis of the probe, the at least two rows including at least a first row and a second row.

[0153] In other applications, the farthest camera along the longitudinal axis of at least four cameras and the closest camera along the longitudinal axis are positioned so that their optical axes are at an angle of 90 degrees or less relative to each other from a line of sight perpendicular to the longitudinal axis. The cameras in the first row and the cameras in the second row can be positioned so that the optical axes of the cameras in the first row are at an angle of 90 degrees or less relative to the optical axes of the cameras in the second row from a line of sight coaxial with the longitudinal axis of the probe. The remaining cameras of the at least four cameras except the farthest camera and the closest camera have optical axes substantially parallel to the longitudinal axis of the probe. Each of the at least two rows may include an alternating sequence of light projectors and cameras.

[0154] In other applications, the at least four cameras include at least five cameras, the at least two light projectors include at least five light projectors, the proximal-most components in the first row are the light projectors, and the proximal-most components in the second row are the cameras.

[0155] In other applications, the farthest camera along the longitudinal axis and the closest camera along the longitudinal axis are positioned so that their optical axes are at an angle of 35 degrees or less relative to each other from a line of sight perpendicular to the longitudinal axis. The cameras in the first row and the cameras in the second row can be positioned so that the optical axes of the cameras in the first row are at an angle of 35 degrees or less relative to the optical axes of the cameras in the second row from a line of sight coaxial with the longitudinal axis of the probe.

[0156] In other applications, at least four cameras may have a combined field of view of about 25-45 mm or about 20-50 mm along the longitudinal axis and a field of view of about 20-40 mm or about 15 mm-80 mm along the z-axis corresponding to the distance from the probe. Other FOVs discussed herein may also be provided.

[0157] Reference now Figure 7 , which is a schematic diagram of a structured light projector 22 projecting a distribution of discrete, unconnected light spots onto multiple object focal planes according to some applications of the present disclosure. The scanned 3D surfaces 32A, 32B may be one or more teeth or other intraoral objects / tissues within the mouth of the subject. The somewhat translucent and glossy properties of the teeth may affect the contrast of the structured light pattern being projected. For example, (a) some of the light striking the teeth may be scattered to other areas in the intraoral scene, resulting in a certain amount of stray light, and (b) some of the light may penetrate the teeth and then be emitted from the teeth at any other point. Therefore, in order to improve image capture of intraoral scenes under structured light illumination without using contrast enhancement means (e.g., coating the teeth with opaque powder), a sparse distribution 34 of discrete, unconnected light spots may provide an improved balance between reducing the amount of projected light and maintaining the amount of useful information. The sparsity of the distribution 34 can be characterized by the ratio of: (a) the illuminated area on the orthogonal plane 44 in the illumination field α (alpha), that is, the sum of the areas of all projected spots 33 on the orthogonal plane 44 in the illumination field α (alpha), and (b) the non-illuminated area on the orthogonal plane 44 in the illumination field α (alpha).

[0158] In some applications, the sparsity ratio can be at least 1:150 and / or less than 1:16 (eg, at least 1:64 and / or less than 1:36).

[0159] In some applications, each structured light projector 22 projects at least 400 discrete, unconnected spots 33 onto the intraoral three-dimensional surface during scanning. In some applications, each structured light projector 22 projects less than 3,000 discrete, unconnected spots 33 onto the intraoral surface during scanning. To reconstruct the three-dimensional surface from the sparse distribution of projections 34, a correspondence between the corresponding projected spots 33 and the spots detected by the camera 24 is determined, as described below with reference to Figure 9-Figure 19 Further described.

[0160] Reference now Figure 8A-B , which is a schematic diagram of a structured light projector 22 projecting discrete, unconnected spots 33 and a camera sensor 58 detecting spots 33' according to some applications of the present disclosure. For some applications, a method is provided for determining a correspondence between projected spots 33 on an intraoral surface and detected spots 33' on a corresponding camera sensor 58. Once the correspondence is determined, a three-dimensional image of the surface is reconstructed. Each camera sensor 58 has an array of pixels, and for each pixel, there is a corresponding camera ray 86. Similarly, for each projected spot 33 from each projector 22, there is a corresponding projector ray 88. Each projector ray 88 corresponds to a corresponding path 92 of a pixel on at least one camera sensor 58. Therefore, if the camera sees a spot 33' projected by a particular projector ray 88, then that spot 33' will necessarily be detected by a pixel on a particular pixel path 92 corresponding to that particular projector ray 88. Specific reference is made to Figure 8B , shows the correspondence between corresponding projector rays 88 and corresponding camera sensor paths 92. Projector ray 88' corresponds to camera sensor path 92', projector ray 88" corresponds to camera sensor path 92", and projector ray 88"' corresponds to camera sensor path 92"'. For example, if a particular projector ray 88 projects a spot into a dusty space, then the dust line in the air will be illuminated. The dust line detected by the camera sensor 58 will follow the same path on the camera sensor 58 as the camera sensor path 92 corresponding to the particular projector ray 88.

[0161] During the calibration process, calibration values ​​are stored based on the camera light 86 corresponding to the pixels on the camera sensor 58 of each camera 24 and the projector light 88 corresponding to the projection spot 33 from each structured projector 22. For example, calibration values ​​may be stored for (a) a plurality of camera light 86 corresponding to a corresponding plurality of pixels on the camera sensor 58 of each camera 24 and (b) a plurality of projector light 88 corresponding to a corresponding plurality of projection spots 33 from each structured light projector 22.

[0162] As an example, the following calibration process can be used. A high-accuracy point target (e.g., a black dot on a white background) is illuminated from below and an image of the target is captured using all cameras. The point target is then moved vertically (i.e., along the z-axis) toward the camera to the target plane. The point center is calculated for all points in all corresponding z-axis positions to create a three-dimensional grid of points in space. The distortion and camera pinhole model is then used to find the pixel coordinates of each three-dimensional position of the corresponding point center, thereby limiting the camera light for each pixel to the light originating from the pixel whose direction is toward the corresponding point center in the three-dimensional grid. The camera light corresponding to the pixels between the grid points can be interpolated. The above camera calibration process is repeated for all corresponding wavelengths of each laser diode 36, so that the stored calibration values ​​include camera light 86 for each pixel on each camera sensor 58 for each wavelength.

[0163] After the camera 24 has been calibrated and all camera light 86 values ​​are stored, the structured light projector 22 can be calibrated as follows. Use a flat featureless target and turn on one structured light projector 22 at a time. Each spot is located on at least one camera sensor 58. Since the camera 24 is now calibrated, the three-dimensional spot position of each spot is calculated by triangulation based on the image of the spot in multiple different cameras. Repeat the above process with featureless targets at multiple different z-axis positions. Each projected spot on the featureless target will define the projector light originating from the projector in space.

[0164] Reference now Fig. 9 , which summarizes a method 900 for determining a depth value of a point in an intraoral scan according to some applications of the present disclosure. For example, the method 900 may be implemented at blocks 110 and 120 of the method 101 .

[0165] In operations 62 and 64 of method 900, respectively, each structured light projector 22 is driven to project a distribution 34 of discrete, unconnected light spots 33 onto the intraoral three-dimensional surface, and each camera 24 is driven to capture an image including at least one spot 33. In operation 66, a correspondence algorithm is run using processor 96 based on the stored calibration values, which will be referred to below. Figure 10-Figure 14 Further described, the stored calibration values ​​indicate (a) camera light 86 corresponding to each pixel on the camera sensor 58 of each camera 24, and (b) projector light 88 corresponding to each projection spot 33 from each structured light projector 22. In an embodiment, the processor 96 may be Figure 3 The processor of the computing device 305 and in an embodiment may correspond to Fig. 20The processing device 2020. Once the correspondence is solved, in operation 68, the three-dimensional position on the intraoral surface is calculated and used to generate a digital three-dimensional image of the intraoral surface. In addition, the use of multiple cameras 24 to capture the intraoral scene provides a signal-to-noise ratio improvement in the capture by a factor of the square root of the number of cameras.

[0166] Reference now Fig.10 , which is a flow chart outlining a correspondence algorithm of operation 66 in method 900 according to some applications of the present disclosure. Based on the stored calibration values, all projector rays 88 and all camera rays 86 corresponding to all detected spots 33' are mapped (operation 70), and all intersection points 98 of at least one camera ray 86 and at least one projector ray 88 are identified (operation 98). Fig.12 )(Operation 72). Fig.11 and Fig.12 They are Fig.10 A schematic diagram of a simplified example of operations 70 and 72 is shown. Fig.11 As shown, three projector rays 88 are mapped with eight camera rays 86 corresponding to a total of eight detected spots 33' on the camera sensor 58 of the camera 24. Fig.12 As shown, sixteen intersection points 98 are identified.

[0167] In operations 74 and 76 of method 900 , processor 96 determines a correspondence between projected spots 33 and detected spots 33 ′ in order to identify the three-dimensional position of each projected spot 33 on the surface. Fig.13 is a diagram that depicts the simplified example described in the previous paragraph above. Fig.10 Schematic diagram of operations 74 and 76 of . For a given projector ray i, the processor 96 "looks" at the corresponding camera sensor path 90 on the camera sensor 58 of one of the cameras 24. Each detected spot j along the camera sensor path 90 will have a camera ray 86 that intersects the given projector ray i at an intersection 98. The intersection 98 defines a three-dimensional point in space. The processor 96 then "looks" at the camera sensor paths 90' corresponding to the given projector ray i on the corresponding camera sensors 58' of the other cameras 24, and identifies how many other cameras 24 also detected corresponding spots k on their corresponding camera sensor paths 90' corresponding to the given projector ray i whose camera rays 86' intersect the same three-dimensional point in space defined by the intersection 98. The process is repeated for all detected spots j along the camera sensor path 90, and the spot j that the greatest number of cameras 24 "agrees" with is identified as spot 33 ( Fig.14), the spot 33 is projected onto the surface from a given projector ray i. That is, the projector ray i is identified as the specific projector ray 88 that produced the detected spot j for which the largest number of other cameras detected the corresponding spot k. The three-dimensional position on the surface is thus calculated for this spot 33.

[0168] For example, Fig.13 As shown, all four cameras detect respective spots on their respective camera sensor paths corresponding to projector ray i where their respective camera rays intersect with projector ray i at intersection point 98, which is defined as the intersection of camera ray 86 corresponding to detected spot j with projector ray i. Thus, all four cameras are said to "agree" that there is a spot 33 projected by projector ray i at intersection point 98. However, when the process is repeated for the next spot j', no other camera detects, on its corresponding camera sensor path corresponding to projector ray i, a corresponding spot whose corresponding camera ray intersects with projector ray i at intersection 98', which intersection 98' is defined as the intersection of camera ray 86" (corresponding to detected spot j') and projector ray i. Therefore, only one camera is said to "agree" that there is a spot 33 projected by projector ray i at intersection 98', while four cameras "agree" that there is a spot 33 projected by projector ray i at intersection 98. Therefore, projector ray i is identified as being projected onto the surface at intersection 98 by projecting spot 33 onto the surface ( Fig.14 ) to produce the specific projector light 88 of the detected spot j. Fig.10 Operation 78 and Fig.14 As shown, the three-dimensional position 35 on the inner surface of the mouth at the intersection point 98 is calculated.

[0169] Reference now Fig.15 , which is a flow chart outlining other operations in a correspondence algorithm according to some applications of the present disclosure. Once the position 35 on the surface is determined, the projector ray i that projects spot j and all camera rays 86 and 86' corresponding to spot j and the corresponding spot k are removed from consideration (operation 80), and the correspondence algorithm is run again for the next projector ray i (operation 82). Fig.16 The simplified example described above is depicted after removing the specific projector ray i that projects spot 33 at position 35. Fig.15 Operation 82 in the flowchart of , and then the correspondence algorithm is run again for the next projector ray i. Fig.16 As shown, the remaining data shows that the three cameras "agree" that spot 33 exists at intersection point 98, which is defined by the intersection of camera ray 86 corresponding to detected spot j and projector ray i. Fig.17 As shown, the three-dimensional position 37 at the intersection point 98 is calculated.

[0170] like Fig.18 As shown, once the three-dimensional position 37 on the surface is determined, the projector ray i that projects spot j and all camera rays 86 and 86' corresponding to spot j and the corresponding spot k are again removed from consideration. The remaining data shows the spot 33 projected by the projector ray i at the intersection 98, and the three-dimensional position 41 on the surface at the intersection 98 is calculated. Fig.19 As shown, according to a simplified example, three projected spots 33 of three projector rays 88 of the structured light projector 22 have now been positioned on the surface at three-dimensional positions 35, 37, and 41. In some applications, each structured light projector 22 projects 400-3000 spots 33. Once the correspondence is solved for all projector rays 88, a reconstruction algorithm can be used to reconstruct a digital image of the surface using the calculated three-dimensional positions of the projected spots 33.

[0171] Reference again Figure 5A . For some applications, there is at least one uniform light projector 118 coupled to the rigid structure 26. The uniform light projector 118 emits white light onto the 3D surface 32, 33 being scanned. At least one camera (e.g., one of the cameras 24) captures a two-dimensional color image of the 3D surface 32A using the illumination from the uniform light projector 118. The processor 96 can run a surface reconstruction algorithm that combines at least one image captured using the illumination from the structured light projector 22 with multiple images captured using the illumination from the uniform light projector 118 to generate a digital three-dimensional image of the intraoral three-dimensional surface. Using a combination of structured light and uniform illumination enhances the overall capture of the intraoral scanner and can help reduce the number of options that the processor 96 needs to consider when running the correspondence algorithm.

[0172] Fig. 20A graphical representation of a machine in the example form of a computing device 2000 is shown, in which a set of instructions can be executed, which is used to make the machine perform any one or more methods discussed herein. In alternative embodiments, the machine can be connected (e.g., networked) to other machines in a local area network (LAN), an intranet, an extranet, or the Internet. The machine can run in the capacity of a server or client machine in a client-server network environment, or as a peer machine in a peer-to-peer (or distributed) network environment. The machine can be a personal computer (PC), a tablet computer, a set-top box (STB), a personal digital assistant (PDA), a cellular phone, a web device, a server, a network router, a switch or a bridge, or any machine capable of executing a set of instructions (sequentially or otherwise) specifying the action to be taken by the machine. In addition, although only a single machine is shown, the term "machine" should also be considered to include any collection of machines (e.g., computers) that execute a set (or multiple sets) of instructions to perform any one or more methods discussed herein, either individually or jointly.

[0173] The example computing device 2000 includes a processing device 2002, a main memory 2004 (e.g., read-only memory (ROM), flash memory, dynamic random access memory (DRAM) such as synchronous DRAM (SDRAM), etc.), a static memory 2006 (e.g., flash memory, static random access memory (SRAM), etc.), and an auxiliary memory (e.g., a data storage device 2028), which communicate with each other via a bus 2008.

[0174] Processing device 2002 represents one or more general-purpose processors such as a microprocessor, a central processing unit, etc. More specifically, processing device 2002 may be a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, a processor implementing other instruction sets, or a processor implementing a combination of instruction sets. Processing device 2002 may also be one or more special-purpose processing devices, such as an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal processor (DSP), a network processor, etc. Processing device 2002 is configured to execute processing logic (instructions 2026) for performing the operations discussed herein.

[0175] The computing device 2000 may also include a network interface device 2022 for communicating with a network 2064. The computing device 2000 may also include a video display unit 2010 (e.g., a liquid crystal display (LCD) or a cathode ray tube (CRT)), an alphanumeric input device 2012 (e.g., a keyboard), a cursor control device 2014 (e.g., a mouse), and a signal generating device 2020 (e.g., a speaker).

[0176] The data storage device 2028 may include a machine-readable storage medium (or more specifically, a non-transitory computer-readable storage medium) 2024, on which is stored one or more sets of instructions 2026 that embody any one or more methods or functions described herein. Among them, the non-transitory storage medium refers to a storage medium other than a carrier wave. During the execution of the instructions 2026 by the computer device 2000, the instructions 2026 may also reside completely or at least partially in the main memory 2004 and / or the processing device 2002, and the main memory 2004 and the processing device 2002 also constitute computer-readable storage media.

[0177] The computer readable storage medium 2024 may also be used to store an intraoral scanning module 2050, which may correspond to Figure 3 . The computer-readable storage medium 2024 may also store a software library containing methods for calling the intraoral scanning module 2050, the scanning registration module, and / or the model generation module. Although the computer-readable storage medium 2024 is shown as a single medium in the example embodiment, the term "computer-readable storage medium" should be deemed to include a single medium or multiple media (e.g., centralized or distributed databases, and / or associated caches and servers) that store one or more sets of instructions. The term "computer-readable storage medium" should also be deemed to include any medium that is capable of storing or encoding a set of instructions for machine execution and causing the machine to perform any one or more methods of the present disclosure. Therefore, the term "computer-readable storage medium" should be deemed to include, but is not limited to, solid-state memories, and optical and magnetic media.

[0178] It should be understood that the above description is intended to be illustrative rather than restrictive. After reading and understanding the above description, many other embodiments will be apparent. Although the embodiments of the present disclosure have been described with reference to specific example embodiments, it should be appreciated that the present disclosure is not limited to the described embodiments, but can be practiced by modification and change within the spirit and scope of the appended claims. Therefore, the description and drawings should be regarded as illustrative rather than restrictive. Therefore, the scope of the present disclosure should be determined with reference to the full scope of the appended claims and the equivalents of these claims.

Claims

1. A system comprising: an intraoral scanner configured to generate a plurality of intraoral scans of a dental arch; as well as One or more computing devices configured to: receiving a plurality of intraoral scans of the dental arch; determining that at least one intra-oral scan of the plurality of intra-oral scans includes a depiction of a first three-dimensional (3D) surface and a depiction of at least one feature of a second 3D surface, the second 3D surface being separated from the first 3D surface by at least one intermediate 3D surface not shown in the at least one intra-oral scan, wherein a distance exists between the first 3D surface and the feature of the second 3D surface in the at least one intra-oral scan; stitching the plurality of intraoral scans together; and A virtual 3D model of the dental arch is generated from the multiple intraoral scans, wherein the distance between the first 3D surface and the second 3D surface in the virtual 3D model is based on the distance between the features of the first 3D surface and the second 3D surface in at least one of the intraoral scans.

2. A system comprising: an intraoral scanner configured to generate a plurality of intraoral scans of a dental arch; as well as One or more computing devices configured to: receiving a plurality of intraoral scans of the dental arch; determining that at least one intra-oral scan of the plurality of intra-oral scans includes a depiction of a first three-dimensional (3D) surface in a first quadrant of the dental arch and a depiction of at least one feature of a second 3D surface in a second quadrant of the dental arch, wherein a distance exists between the features of the first 3D surface and the second 3D surface in the at least one intra-oral scan; stitching the plurality of intraoral scans together; and A virtual 3D model of the dental arch is generated from the multiple intraoral scans, wherein the distance between the first 3D surface and the second 3D surface in the virtual 3D model is based on the distance between the features of the first 3D surface and the second 3D surface in at least one of the intraoral scans.

3. A non-transitory computer-readable medium comprising instructions, which, when executed by one or more processing devices, cause the one or more processing devices to perform the following operations, including: determining that at least one intra-oral scan of the plurality of intra-oral scans includes a depiction of a first three-dimensional (3D) surface of a dental arch and a depiction of at least one feature of a second 3D surface of the dental arch, the second 3D surface being separated from the first 3D surface by at least one intermediate 3D surface not shown in the at least one intra-oral scan, wherein a distance exists between the first 3D surface and the feature of the second 3D surface in the at least one intra-oral scan; stitching the plurality of intraoral scans together; and A virtual 3D model of the dental arch is generated from the multiple intraoral scans, wherein the distance between the first 3D surface and the second 3D surface in the virtual 3D model is based on the distance between the features of the first 3D surface and the second 3D surface in at least one of the intraoral scans.

4. A non-transitory computer-readable medium comprising instructions, which, when executed by one or more processing devices, cause the one or more processing devices to perform the following operations, including: determining that at least one intra-oral scan of the plurality of intra-oral scans includes a depiction of a first three-dimensional (3D) surface in a first quadrant of a dental arch and a depiction of at least one feature of a second 3D surface in a second quadrant of the dental arch, wherein a distance exists between the features of the first 3D surface and the second 3D surface in the at least one intra-oral scan; stitching the plurality of intraoral scans together; and A virtual 3D model of the dental arch is generated from the multiple intraoral scans, wherein the distance between the first 3D surface and the second 3D surface in the virtual 3D model is based on the distance between the features of the first 3D surface and the second 3D surface in at least one of the intraoral scans.

5. A system comprising: an intraoral scanner configured to generate a plurality of intraoral scans of a dental arch; as well as A computing device configured to: receiving a plurality of intraoral scans of the dental arch; determining that at least one intra-oral scan of the plurality of intra-oral scans includes a buccal view of a first three-dimensional 3D surface and a lingual view of at least one feature of a second 3D surface, wherein a distance exists between the first 3D surface and at least the feature of the second 3D surface in the at least one intra-oral scan; stitching the plurality of intraoral scans together; and A virtual 3D model of the dental arch is generated from the multiple intraoral scans, wherein at least one of the intraoral scans is used to generate both a first 3D surface of the virtual 3D model and a second 3D surface of the virtual 3D model, and wherein a distance between the first 3D surface and the second 3D surface in the virtual 3D model is based on a distance between the features of the first 3D surface and the second 3D surface in the at least one intraoral scan.

6. A system comprising: an intraoral scanner configured to generate a plurality of intraoral scans of the patient's edentulous dental arch; as well as One or more computing devices configured to: receiving an indication that a dental prosthesis is to be fabricated for the patient, wherein the dental prosthesis is to be attached to at least a first dental implant and a second dental implant on the edentulous dental arch; receiving a plurality of intraoral scans of the edentulous dental arch; determining whether any intra-oral scan of the plurality of intra-oral scans depicts both a first scan volume associated with the first dental implant and a second scan volume associated with the second dental implant; In response to determining that none of the plurality of intraoral scans depicts both the first scan volume and the second scan volume, outputting instructions to position a probe of the intraoral scanner to generate at least one intraoral scan depicting both the first scan volume and the second scan volume; receiving the at least one intraoral scan depicting the first scan volume and the second scan volume; and A virtual three-dimensional (3D) model of the edentulous dental arch is generated using the plurality of intraoral scans and the at least one intraoral scan.

7. A system comprising: Intraoral scanner, which includes: one or more light projectors configured to project pattern features of a light pattern onto a dental arch comprising a first 3D surface and a second 3D surface; and one or more cameras configured to generate a plurality of intra-oral scans comprising captured pattern features of the light pattern projected onto the dental arch; and One or more computing devices configured to: running a correspondence algorithm that determines a three-dimensional position of a capture pattern feature on the dental arch for at least one of the plurality of intraoral scans using a depth threshold to determine a first depth of the first 3D surface, wherein the depth threshold limits a search for the capture pattern feature to a depth greater than the depth threshold; subsequently running the correspondence algorithm on the at least one intraoral scan without the depth threshold to determine a second depth of the second 3D surface, wherein the first depth is less than the depth threshold and the second depth is greater than the depth threshold; stitching the plurality of intraoral scans together; and A virtual 3D model of the dental arch is generated from the multiple intraoral scans.

8. A computer-readable medium comprising instructions, which, when executed by one or more processing devices, cause the one or more processing devices to perform the following operations, including: causing one or more light projectors of the intraoral scanner to project pattern features of the light pattern onto a dental arch including the first 3D surface and the second 3D surface; causing one or more cameras of the intraoral scanner to generate a plurality of intraoral scans including captured pattern features of the light pattern projected onto the dental arch; running a correspondence algorithm that determines a three-dimensional position of a capture pattern feature on the dental arch for at least one of the plurality of intraoral scans using a depth threshold to determine a first depth of the first 3D surface, wherein the depth threshold limits a search for the capture pattern feature to a depth greater than the depth threshold; subsequently running the correspondence algorithm on the at least one intraoral scan without the depth threshold to determine a second depth of the second 3D surface, wherein the first depth is less than the depth threshold and the second depth is greater than the depth threshold; stitching the plurality of intraoral scans together; and A virtual 3D model of the dental arch is generated from the multiple intraoral scans.

9. A method comprising: causing one or more light projectors of the intraoral scanner to project pattern features of the light pattern onto a dental arch including the first 3D surface and the second 3D surface; causing one or more cameras of the intraoral scanner to generate a plurality of intraoral scans including captured pattern features of the light pattern projected onto the dental arch; running a correspondence algorithm that determines a three-dimensional position of a capture pattern feature on the dental arch for at least one of the plurality of intraoral scans using a depth threshold to determine a first depth of the first 3D surface, wherein the depth threshold limits a search for the capture pattern feature to a depth greater than the depth threshold; subsequently running the correspondence algorithm on the at least one intraoral scan without the depth threshold to determine a second depth of the second 3D surface, wherein the first depth is less than the depth threshold and the second depth is greater than the depth threshold; stitching the plurality of intraoral scans together; and A virtual 3D model of the dental arch is generated from the multiple intraoral scans.

Images