Intraoral 3D scanner with multiple miniature cameras and miniature pattern projector

Abstract

Apparatus for intraoral scanning includes an elongate handpiece having a probe. One or more light projectors and two or more cameras are disposed within the probe. Each light projector has a pattern generating optical element that uses diffraction or refraction to form a light pattern. Each camera can be configured to focus at between 1 mm and 30 mm from a lens furthest from the camera sensor. Other applications are described.

Description

[0001] This application is a divisional application of the following invention patent application: filed on June 24, 2019, application number 201910550559.4, entitled Intraoral 3D Scanner with Multiple Miniature Cameras and Miniature Pattern Projector. Technical Field

[0002] This invention generally relates to three-dimensional imaging, and more specifically, to intraoral three-dimensional imaging using structured light illumination. Background Technology

[0003] Dental impressions of the subject's three-dimensional oral surfaces (e.g., teeth and gums) are used to plan dental procedures. Conventional dental impressions are made using impression trays filled with impression material (e.g., PVS or alginate) that contains the subject's occlusion. The impression material is then cured to form a negative imprint of the teeth and gums, thereby creating a three-dimensional model of the teeth and gums.

[0004] Digital dental impressions utilize intraoral scanning to generate a three-dimensional digital model of the subject's intraoral surface. Digital intraoral scanners typically employ structured light 3D imaging. The surfaces of a subject's teeth can be highly reflective and somewhat translucent, which can reduce the contrast in the structured light pattern reflected from the teeth. Therefore, to improve capture during intraoral scanning, when using a digital intraoral scanner utilizing structured light 3D imaging, the subject's teeth are often coated with an opaque powder before scanning to ensure that the contrast of the structured light pattern reaches a usable level, for example, to transform the surface into a scattering surface. While intraoral scanners utilizing structured light 3D imaging have made some progress, additional advantages can be found. Summary of the Invention

[0005] The use of structured light 3D imaging can lead to a "correspondence problem," where it's necessary to determine the correspondence between light points in a structured light pattern and the light points seen by a camera observing the pattern. One technique for solving this problem is based on projecting an "encoded" light pattern and imaging the scene from one or more viewpoints. Encoding the emitted light pattern makes each part of the pattern unique and distinguishable when captured by the camera system. Because the pattern is encoded, it's easier to find the correspondence between image points and points in the projected pattern. Triangulation can be performed on the decoded points to reconstruct 3D information.

[0006] Applications of this invention include systems and methods relating to a three-dimensional intraoral scanning apparatus, which includes one or more cameras and one or more pattern projectors. For example, some applications of this invention may relate to an intraoral scanning apparatus having multiple cameras and multiple pattern projectors.

[0007] Other applications of the present invention include methods and systems for decoding structured light patterns.

[0008] Other applications of the invention may relate to systems and methods for three-dimensional intraoral scanning utilizing non-coded structured light patterns. For example, the non-coded structured light pattern may include a uniform spot pattern.

[0009] For example, in certain applications of the invention, an apparatus for intraoral scanning is provided, comprising an elongated handheld stick with a probe at its distal end. During scanning, the probe can be configured to enter the oral cavity of a subject. One or more light projectors (e.g., miniature structured light projectors) and one or more cameras (e.g., miniature cameras) are integrated into a rigid structure disposed within the distal end of the probe. Each structured light projector emits light using a light source (e.g., a laser diode). Each light projector can be configured to project a light pattern defined by the light rays from the multiple projectors when the light source is activated. Each camera can be configured to capture multiple images depicting at least a portion of the light pattern projected onto an intraoral surface. In some applications, the structured light projector may have an illumination field of at least 45 degrees. Optionally, the illumination field may be less than 120 degrees. Each structured light projector may also include pattern-generating optics. The pattern-generating optics may utilize diffraction and / or refraction to generate the light pattern. In some applications, the light pattern may be a distribution of discrete, unconnected light points. Optionally, when a light source (e.g., a laser diode) is activated to emit light through the pattern-generating optics, the light pattern maintains a discrete distribution of unconnected light points across all planes between 1 mm and 30 mm from the pattern-generating optics. In some applications, the pattern-generating optics of each structured light projector may have a luminous flux efficiency of at least 80% (e.g., at least 90%), i.e., the proportion of light falling on the pattern generator and entering the pattern. Each camera includes a camera sensor and objective optics comprising one or more lenses.

[0010] In some applications, laser diode light sources and diffraction and / or refractive pattern generating optics can offer certain advantages. For example, the use of laser diodes and diffraction and / or refractive pattern generating optics can help maintain an energy-efficient structured light projector to prevent the probe from overheating during use. Furthermore, these components can help reduce costs by eliminating the need for active cooling within the probe. For example, modern laser diodes can use less than 0.6 watts of power while continuously emitting at high brightness (e.g., compared to modern light-emitting diodes (LEDs)). When pulsed according to some applications of the invention, these modern laser diodes may use even less power; for example, when pulsed at a 10% duty cycle, a laser diode can use less than 0.06 watts (however, for some applications, laser diodes can use at least 0.2 watts while continuously emitting at high brightness, and when pulsed, even less power can be used; for example, when pulsed at a 10% duty cycle, a laser diode can use at least 0.02 watts). Furthermore, diffraction and / or refraction pattern generating optical elements can be configured to utilize most (if not all) of the emitted light (e.g., compared to a mask that blocks some light from reaching the object).

[0011] Specifically, diffraction and / or refraction-based pattern-generating optics generate patterns through the diffraction, refraction, or interference of light, or any combination thereof, rather than through light modulation via transparent or transmission masks. In some applications, this can be advantageous because the throughput efficiency (the ratio of light entering the pattern to light falling on the pattern generator) is close to 100% (e.g., at least 80%, or at least 90%), independent of the area-based duty cycle mode. Conversely, the throughput efficiency of transparent or transmission mask pattern-generating optics is directly related to the area-based duty cycle. For example, for a desired area-based duty cycle of 100:1, the throughput efficiency of a mask-based pattern generator would be 1%, while the efficiency of a diffraction and / or refraction-based pattern-generating optics remains close to 100%. Furthermore, because lasers inherently have a smaller emission area and divergence angle, resulting in brighter output illumination per unit area, the light collection efficiency of a laser is at least 10 times higher than that of an LED with the same total light output. The high efficiency of lasers and diffraction and / or refraction pattern generators can help achieve thermally efficient configurations, limiting significant temperature rise of the probe during use, thereby reducing costs by potentially eliminating or limiting the need for active cooling within the probe. While laser diodes and DOEs may be particularly preferred in some applications, their use alone or in combination is not necessary. Other light sources, including LEDs, and pattern generating elements, including transparent and transmissive masks, can be used in other applications.

[0012] In some applications, without using contrast enhancement methods such as coating teeth with opaque powder, the inventors have realized that, to improve image capture of intraoral scenes under structured light illumination, the distribution of discrete, unconnected light points (e.g., rather than lines) can provide an improved balance between increasing pattern contrast and maintaining useful information. In some applications, the unconnected light points have a uniform (e.g., invariant) pattern. Generally, denser structured light patterns can provide more surface sampling, higher resolution, and better stitching of corresponding surfaces obtained from multiple image frames. However, overly dense structured light patterns can lead to more complex correspondence problems because there are more light points to solve. Additionally, 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 and (b) percolation, where stray light reflects off some smooth surfaces of the teeth and may be captured by the camera, and percolation is when some light enters the tooth, reflects along multiple paths within the tooth, and then exits the tooth in many different directions. As further described below, methods and systems are provided for solving the correspondence problems presented by the distribution of discrete, unconnected light points. In some applications, discrete, unconnected light spots from each projector can be uncoded.

[0013] In some applications, the field of view of each camera can be at least 45 degrees, for example, at least 80 degrees (e.g., 85 degrees). Alternatively, the field of view of each camera can be less than 120 degrees, for example, less than 90 degrees. For some applications, one or more cameras have fisheye lenses or other optics that provide a viewing angle of up to 180 degrees.

[0014] In any case, the fields of view of the various cameras can be the same or different. Similarly, the focal lengths of the various cameras can be the same or different. The term "field of view" used herein for each camera refers to the diagonal field of view of each camera. Furthermore, each camera can be configured to focus on the object focal plane at a distance between 1 mm and 30 mm, for example, at least 5 mm and / or less than 11 mm, such as 9 mm-10 mm, from the lens furthest from the corresponding camera sensor. Similarly, in some applications, the illumination field of each structured light projector can be at least 45 degrees and optionally less than 120 degrees. The inventors have recognized that a large field of view achieved by combining the individual fields of view of all cameras can improve accuracy due to a reduced amount of image stitching errors, especially in edentulous regions where the gingival surface is smooth and there may be fewer sharp, high-resolution 3D features. A larger field of view allows large, smooth features, such as the overall curve of the teeth, to appear in each image frame, which improves the accuracy of stitching individual surfaces obtained from multiple such image frames. In some applications, the combined field of view of the various cameras (e.g., an intraoral scanner) is between about 20 mm and about 50 mm along the longitudinal axis of the elongated handheld rod, and about 20-40 mm along the z-axis, where the z-axis may correspond to depth. In other applications, the field of view along the longitudinal axis may be at least 20 mm, at least 25 mm, at least 30 mm, at least 35 mm, or at least 40 mm. In some embodiments, the combined field of view may vary with depth (e.g., with scanning distance). For example, at a scanning distance of about 4 mm, the field of view along the longitudinal axis may be about 40 mm, and at a scanning distance of about 14 mm, the field of view along the longitudinal axis may be about 45 mm. If most of the movement of the intraoral scanner is performed relative to the long axis (e.g., the longitudinal axis) of the scanner, there may be significant overlap between scans. In some applications, the combined field of view of the cameras 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. The fixed interval may, for example, be along the longitudinal axis of the elongated handheld rod.

[0015] In some applications, a method is provided for generating digital three-dimensional images of the intraoral surface. It should be noted that the term "three-dimensional image" as used in this application refers to an image of the three-dimensional intraoral surface constructed from a three-dimensional model (e.g., a point cloud). While the resulting image is typically displayed on a two-dimensional screen, it contains data relating to the three-dimensional structure of the scanned object and can therefore often be manipulated to display the scanned object from different views and perspectives. Additionally, data from the three-dimensional image can be used to create a physical three-dimensional model of the scanned object.

[0016] For example, one or more structured light projectors can be driven to project a discrete distribution of unconnected light spots onto the intraoral surface, and one or more cameras can be driven to capture the projected images. The image captured by each camera may include at least one light spot.

[0017] Each camera includes a camera sensor with a pixel array. For each pixel, there exists a corresponding ray of light originating from that pixel in three-dimensional space, the direction of which is toward the object being imaged; when imaging occurs on the sensor, each point along a particular one of these rays will fall on its corresponding pixel on the sensor. As used throughout this application, including in the claims, the term used here is “camera ray.” Similarly, for each projected light spot from each projector, there exists a corresponding projector ray. Each projector ray corresponds to a corresponding pixel path on at least one camera sensor, i.e., if a camera sees a light spot projected by a particular projector ray, then that light spot must be detected by a pixel on a particular path of the pixel corresponding to that particular projector ray. (a) the value of the camera ray corresponding to each pixel on the camera sensor of each camera and (b) the value of the projector ray corresponding to each projected light spot from each projector can be stored during the calibration process, as described below.

[0018] Based on stored calibration values, the processor can be used to run a corresponding algorithm to identify the three-dimensional position of each projected light spot on the surface. For a given projector ray, the processor "looks" at the corresponding camera sensor path on one of the cameras. Each detected light spot along this camera sensor path will have a camera ray that intersects with the given projector ray. This intersection defines a three-dimensional point in space. The processor then searches the camera sensor paths corresponding to the given projector ray on the other cameras and identifies how many other cameras also detect light spots on their corresponding camera sensor paths corresponding to the given projector ray, whose camera rays intersect with the three-dimensional point in space. As used throughout this application, if two or more cameras detect light spots whose corresponding camera rays intersect with the given projector ray at the same three-dimensional point in space, the cameras are considered to "agree" that the light spot is located at that three-dimensional point. Therefore, the processor can identify the three-dimensional position of the projected light pattern based on the agreement of two or more cameras that the projector ray projects a light pattern at some intersection. This process is repeated for additional light spots along the camera sensor path, and the maximum number of light spots that the cameras "agree" to be identified as light spots projected onto the surface from the given projector ray. Therefore, the three-dimensional position on the surface is calculated for this light spot.

[0019] Once the position of a specific light spot on the surface is determined, the projector ray projecting that spot and all corresponding camera rays can be disregarded, and the corresponding algorithm can be run again for the next projector ray. Ultimately, the identified 3D position can be used to generate a digital 3D model of the intraoral surface.

[0020] In another example, a method for generating a digital 3D model of an intraoral surface may include projecting a pattern of discrete, unconnected light spots onto the intraoral surface of a patient using one or more light projectors positioned at the distal end of an intraoral scanner, wherein the pattern of discrete, unconnected light spots is non-coded. The method may also include capturing multiple images of the projected pattern of unconnected light spots using two or more cameras positioned in the probes, decoding the multiple images of the projected pattern to determine 3D surface information of the intraoral surface, and using the 3D surface information to generate a digital 3D model of the intraoral surface. Decoding the multiple images may include accessing calibration data that associates camera rays corresponding to pixels on the camera sensors of each of the two or more cameras with multiple projector rays, wherein each of the multiple projector rays is associated with one of the discrete, unconnected light spots. Decoding may also include using the calibration data to determine intersections of the projector rays and camera rays corresponding to the pattern of projected discrete, unconnected light spots, wherein the intersections of the projector rays and camera rays are associated with 3D points in space. Decoding may also include identifying the 3D location of the pattern of discrete, unconnected light spots based on the consensus of the two or more cameras that there are discrete, unconnected light spots projected by the projector rays at certain intersections.

[0021] Therefore, according to some applications of the present invention, an apparatus for intraoral scanning is provided, the apparatus comprising:

[0022] A slender handheld stick, including a probe at the distal end of the handheld stick;

[0023] A rigid structure is installed inside the distal end of the probe.

[0024] One or more structured light projectors, integrated into a rigid structure; and

[0025] One or more cameras are integrated into a rigid structure.

[0026] In some applications, each structured light projector can have an illumination field of 45-120 degrees. Optionally, one or more structured light projectors can use laser diode light sources. Furthermore, structured light projectors may include beam-shaping optics. Additionally, structured light projectors may include pattern-generating optics.

[0027] Pattern generating optics 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 optics, a distribution of discrete, unconnected light spots can be generated at all planes between 1 mm and 30 mm from the pattern generating optics. In some applications, the pattern generating optics (i) utilize diffraction and / or refraction to generate this distribution. Optionally, the pattern generating optics has a luminous flux efficiency of at least 90%.

[0028] Furthermore, in some applications, each camera can (a) have a field of view of 45-120 degrees. The camera may include a camera sensor and objective optics comprising one or more lenses. In some applications, the camera can be configured to focus on the object focal plane between 1 mm and 30 mm from the lens furthest from the camera sensor.

[0029] For some applications, each of one or more cameras is configured to focus on the focal plane of the object between 5mm and 11mm from the lens furthest from the camera sensor.

[0030] For some applications, the pattern generating optics of each of one or more projectors are configured to generate a distribution of discrete, unconnected light spots at all planes between 4 mm and 24 mm from the pattern generating optics when a light source (e.g., a laser diode) is activated to emit light through the pattern generating optics.

[0031] For some applications, each of one or more cameras is configured to focus on the focal plane of an object between 4mm and 24mm from the lens, which is furthest from the camera sensor.

[0032] For some applications, each structured light projector has an illumination field of 70-100 degrees.

[0033] For some applications, each camera has a field of view of 70-100 degrees.

[0034] For some applications, each camera has an 80-90 degree field of view.

[0035] For some applications, the device also includes at least one uniform light projector configured to project white light onto the scanned object, and at least one camera configured to capture a two-dimensional color image of the object using illumination from the uniform light projector.

[0036] For some applications, beam-shaping optics include collimating lenses.

[0037] For some applications, the structured light projectors and cameras are positioned such that each structured light projector faces an object placed outside the wand within its illumination field. Optionally, each camera may face an object placed outside the wand within its field of view. Furthermore, in some applications, at least 20% of the discrete, unconnected light spots are located within the field of view of at least one camera.

[0038] For some applications, the probe height is 10-15mm, in which light enters the probe through the lower surface (or sensing surface) of the probe, and the probe height is measured from the lower surface of the probe to the upper surface of the probe opposite to the lower surface.

[0039] For some applications, one or more structured light projectors happen to be a structured light projector, and one or more cameras happen to be a camera.

[0040] For some applications, pattern-generating optics include diffractive optics (DOEs).

[0041] For some applications, each DOE is configured to generate a discrete distribution of unconnected light points such that when a light source is activated to emit light through the DOE, the ratio of the illuminated area to the unilluminated area is 1:150 to 1:16 for each orthogonal plane in the illumination field.

[0042] For some applications, each DOE is configured to generate a discrete distribution of unconnected light points such that when a light source is activated to emit light through the DOE, the ratio of the illuminated area to the unilluminated area is 1:64 to 1:36 for each orthogonal plane in the illumination field.

[0043] For some applications, one or more structured light projectors are multiple structured light projectors. In some applications, each light spot generated by a particular DOE has the same shape. Optionally, the shape of the light spot generated by at least one DOE differs from the shape of the light spot generated by at least one other DOE.

[0044] For some applications, each of one or more projectors includes an optical element disposed between a beam-shaping optics element and a DOE, the optical element being configured to generate a Bessel beam when the laser diode is activated to emit light through the optical element, such that discrete, unconnected light spots passing through each inner surface of a sphere centered on the DOE and having a radius between 1 mm and 30 mm maintain a diameter of less than 0.06 mm.

[0045] For some applications, the optical element is configured to generate a Bessel beam when the laser diode is activated to emit light through the optical element, such that discrete, unconnected light spots pass through each inner surface of a geometric sphere centered on the DOE with a radius between 1 mm and 30 mm, maintaining a diameter of less than 0.02 mm.

[0046] For some applications, each of one or more projectors includes an optical element positioned between a beam-shaping optics element and a DOE. The optical element can be configured to generate a Bessel beam when the light source is activated to emit light through the optical element, such that discrete, unconnected light spots maintain a small diameter throughout the depth range. For example, in some applications, discrete, unconnected light spots can maintain a diameter of less than 0.06 mm through each orthogonal plane between 1 mm and 30 mm from the DOE.

[0047] For some applications, the optical element is configured to generate a Bessel beam when the laser diode is activated to emit light through the optical element, such that discrete, unconnected light spots maintain a diameter of less than 0.02 mm through each orthogonal plane between 1 mm and 30 mm from the DOE.

[0048] For some applications, the optical element is configured to generate a Bessel beam when the laser diode is activated to emit light through the optical element, such that discrete, unconnected light spots maintain a diameter of less than 0.04 mm through each orthogonal plane between 4 mm and 24 mm from the DOE.

[0049] For some applications, the optical element is an axonoconical lens.

[0050] For some applications, the axial tapered lens is a diffractive axial tapered lens.

[0051] For some applications, the optical element is a ring aperture.

[0052] For some applications, one or more structured light projectors are multiple structured light projectors, and the light sources of at least two structured light projectors are configured to emit light of two different wavelengths respectively.

[0053] For some applications, the light sources of at least three structured light projectors are configured to emit three different wavelengths of light, respectively.

[0054] For some applications, the light sources of at least three structured light projectors are configured to emit red, blue, and green light, respectively.

[0055] In some applications, the light source includes laser diodes.

[0056] For some applications, one or more cameras are multiple cameras combined into a rigid structure such that the angle between the two corresponding optical axes of at least two cameras is 0-90 degrees.

[0057] For some applications, the angle between the two corresponding optical axes of at least two cameras is 0-35 degrees.

[0058] For some applications, one or more structured light projectors are multiple structured light projectors combined into a rigid structure such that the angle between the two corresponding optical axes of at least two structured light projectors is 0-90 degrees.

[0059] For some applications, the angle between the two corresponding optical axes of at least two structured light projectors is 0-35 degrees.

[0060] For some applications, each camera has multiple discrete preset focus positions, at which the camera is configured to focus on the corresponding object's focal plane.

[0061] For some applications, each camera includes an autofocus actuator configured to select a focus position from discrete preset focus positions.

[0062] For some applications, each of one or more cameras includes an optical aperture phase mask, configured to extend the depth of focus of the camera, such that the image formed by each camera remains in focus at all object distances between 1 mm and 30 mm from the lens furthest from the camera sensor.

[0063] For some applications, the optical aperture phase mask is configured to extend the depth of focus of the camera, so that the image formed by each camera remains in focus at all object distances between 4mm and 24mm from the lens furthest from the camera sensor.

[0064] For some applications, each of one or more cameras is configured to capture images at a frame rate of 30-200 frames per second.

[0065] For some applications, each of one or more cameras is configured to capture images at a frame rate of at least 75 frames per second.

[0066] For some applications, each of one or more cameras is configured to capture images at a frame rate of at least 100 frames per second.

[0067] For some applications, the laser diodes of each of one or more projectors are configured to emit elliptical beams. The beam-shaping optics of each of the one or more projectors may include collimating lenses. Optionally, the pattern-generating optics include diffractive optical elements (DOEs) divided into multiple sub-DOE sheets arranged in an array. Each sub-DOE sheet can generate a corresponding distribution of discrete, unconnected light spots in different regions of the illumination field, such that when the light source is activated to emit light through the divided DOEs, a discrete distribution of unconnected light spots is generated.

[0068] For some applications, the collimating lens can be configured to generate an elliptical beam with a major axis of 500-700 micrometers and a minor axis of 100-200 micrometers.

[0069] For some applications, when the laser diode is activated to emit light through the segmented DOE, the sub-DOE array can be positioned to be contained within an elliptical beam.

[0070] For some applications, the cross-section of each sub-DOE sheet is a square with sides of 30-75 micrometers in length, and the cross-section is perpendicular to the optical axis of the DOE.

[0071] For some applications, multiple sub-DOE wafers are arranged in a rectangular array, including 16-72 sub-DOE wafers and having a maximum size of 500-800 micrometers.

[0072] For some applications, the collimating lens and the segmented DOE are a single optical element, with the collimating lens on the first side of the optical element and the segmented DOE on the second side of the optical element opposite to the first side.

[0073] In some applications, at least one light source for each of one or more projectors is a plurality of laser diodes. In some applications, the plurality of laser diodes can be configured to emit light of the same wavelength.

[0074] For some applications, multiple laser diodes can be configured to emit light of different wavelengths.

[0075] For some applications, multiple laser diodes are two laser diodes configured to emit light at two different wavelengths.

[0076] For some applications, multiple laser diodes are three laser diodes, which are configured to emit light at three different wavelengths.

[0077] For some applications, the three laser diodes are configured to emit red, blue, and green light, respectively.

[0078] For some applications:

[0079] The beam-shaping optics of each of one or more projectors include a collimating lens, and

[0080] Pattern-generating optical elements include composite diffraction periodic structures with periodic structural feature sizes of 100-400 nm.

[0081] For some applications, the collimating lens and the compound diffraction periodic structure are a single optical element, with the collimating lens on the first side and the compound diffraction periodic structure on the second side of the optical element opposite to the first side.

[0082] For some applications, the device also includes an axial cone lens positioned between the collimating lens and the compound diffraction periodic structure, the axial cone lens having an axial cone head angle of 0.2-2 degrees.

[0083] For some applications, collimating lenses have a focal length of 1.2-2mm.

[0084] For some applications:

[0085] The beam-shaping optics of each of one or more projectors include a collimating lens, and

[0086] The pattern-generating optical element comprises a microlens array with a numerical aperture of 0.2–0.7.

[0087] For some applications, the microlens array is a hexagonal microlens array.

[0088] For some applications, the microlens array is a rectangular microlens array.

[0089] For some applications, the collimating lens and the microlens array are a single optical element, with the collimating lens on the first side and the microlens array on the second side of the optical element opposite to the first side.

[0090] For some applications, the device also includes an axial cone lens positioned between the collimating lens and the microlens array, the axial cone lens having an axial cone head angle of 0.2-2 degrees.

[0091] For some applications, collimating lenses have a focal length of 1.2-2mm.

[0092] For some applications:

[0093] Each of one or more projectors comprises a beam-shaping optics element including a collimating lens having a focal length of 1.2-2 mm.

[0094] Each of one or more projectors includes an aperture ring disposed between a collimating lens and a pattern-generating optics, and

[0095] Pattern-generating optical elements include composite diffraction periodic structures with periodic structural feature sizes of 100-400 nm.

[0096] For some applications:

[0097] Each of one or more projectors comprises a beam-shaping optics element including a lens (a) disposed between a laser diode and a pattern-generating optics element, and (b) having a planar surface on a first side of the lens and an aspherical surface on a second side of the lens opposite to the first side, the aspherical surface being configured to generate a Bessel beam directly from the diverging beam when the laser diode is activated to emit a diverging beam through the lens and the pattern-generating optics element, such that discrete, unconnected light spots have substantially uniform size at any orthogonal plane between 1 mm and 30 mm from the pattern-generating optics element.

[0098] For some applications, the aspherical surface of the lens is configured to generate a Bessel beam directly from the diverging beam when the laser diode is activated to emit a diverging beam through the lens and the pattern-generating optics, such that discrete, unconnected light spots have substantially uniform size at any orthogonal plane between 4 mm and 24 mm from the pattern-generating optics.

[0099] For some applications, patterning optical elements include composite diffraction periodic structures with periodic structure feature sizes of 100-400 nm.

[0100] For some applications, pattern-generating optics include microlens arrays with numerical apertures of 0.2–0.7.

[0101] For some applications:

[0102] (a) A beam-shaping optical element includes an aspherical surface on a first side of the lens, and (b) a planar surface on a second side of the lens opposite to the first side is shaped to define a pattern-generating optical element.

[0103] The aspherical surface is configured to generate a Bessel beam directly from the diverging beam when the laser diode is activated to emit a diverging beam through the lens, such that the Bessel beam is split into a discrete array of Bessel beams when the laser diode is activated to emit a diverging beam through the lens, such that the discrete, unconnected light spots have substantially uniform size in all planes between 1 mm and 30 mm from the lens.

[0104] For some applications, the planar surface of the lens is shaped to define a pattern-generating optics such that when a laser diode is activated to emit a diverging beam through the lens, the Bessel beam is split into a discrete array of Bessel beams, such that the discrete, unconnected light spots have substantially uniform size at all planes between 4 mm and 24 mm from the pattern-generating optics.

[0105] For some applications, the apparatus and method may also include:

[0106] At least one temperature sensor, incorporated into the rigid structure and configured to measure the temperature of the rigid structure; and

[0107] Temperature control unit.

[0108] The temperature control circuit can be configured to (a) receive data indicating the temperature of the rigid structure from a temperature sensor, and (b) activate the temperature control unit based on the received data. The temperature control unit and circuit can be configured to maintain the probe and / or the rigid structure at a temperature between 35 and 43 degrees Celsius.

[0109] For some applications, the temperature control unit is configured to maintain the probe at a temperature between 37 and 41 degrees Celsius.

[0110] For some applications, the temperature control unit is configured to prevent the temperature change of the probe from exceeding a threshold temperature change.

[0111] For some applications, the device also includes:

[0112] The target, such as a diffuse reflector, comprises multiple regions disposed within the probe such that:

[0113] (a) Each projector has at least one diffuse reflector region in its illumination field.

[0114] (b) Each camera has at least one diffuser area in its field of view, and

[0115] (c) Multiple diffuser regions are in the field of view of one of the cameras and in the illumination field of a projector.

[0116] In some applications, the temperature control circuit can be configured to (a) receive data from the camera indicating the location of the diffuser relative to the distribution of discrete, unconnected light spots, (b) compare the received data with the stored calibration position of the diffuser, (i) the difference between the received data indicating the location of the diffuser and (ii) the stored calibration position of the diffuser indicates a temperature change of the probe, and (c) adjust the temperature of the probe based on the comparison between the received data and the stored calibration position of the diffuser.

[0117] According to some applications of the present invention, a method for generating digital three-dimensional images is also provided, the method comprising:

[0118] Drive each of one or more structured light projectors to project a discrete distribution of unconnected light spots onto a three-dimensional surface within the mouth;

[0119] Drive each of one or more cameras to capture an image including at least one light spot, each of the one or more cameras including a camera sensor including a pixel array;

[0120] Based on stored calibration values, it indicates (a) camera rays corresponding to each pixel on the camera sensor of each of one or more cameras, and (b) projector rays corresponding to each projected light spot from each of one or more projectors, such that each projector ray corresponds to a corresponding pixel path on at least one camera sensor:

[0121] Use the processor to run the corresponding algorithm:

[0122] (1) For each projector ray i, for each detected light spot j on the camera sensor path corresponding to ray i, identify how many other cameras on their respective camera sensor paths corresponding to ray i have detected a corresponding light spot k corresponding to the corresponding camera ray, the corresponding camera ray intersecting with ray i and the camera ray corresponding to the detected light spot j, so that ray i is identified as the specific projector ray that generated the detected light spot j, for which the maximum number of other cameras detected the corresponding light spot k; and

[0123] (2) Calculate the corresponding three-dimensional position on the inner surface of the aperture using the intersection point of the projector ray i with the corresponding camera ray corresponding to the detected light point j and the corresponding detected light point k.

[0124] For some applications, running the corresponding algorithm using the processor also includes, after step (1), using the processor to:

[0125] The projector ray i and the individual camera rays corresponding to the detected light point j and each detected light point k are no longer considered; and

[0126] The corresponding algorithm is run again for the next projector ray i.

[0127] For some applications, driving one or more structured light projectors to project a distribution of discrete, unconnected light spots involves driving each structured light projector to project 400-3000 discrete, unconnected light spots onto a three-dimensional surface inside the mouth.

[0128] For some applications, driving one or more structured light projectors to project a distribution of discrete, unconnected light points involves driving multiple structured light projectors, each projecting a distribution of discrete, unconnected light points, where:

[0129] (a) At least two structured light projectors are configured to emit light of different wavelengths, and

[0130] (b) For each wavelength, the stored calibration value represents the camera light corresponding to each pixel on the camera sensor.

[0131] For some applications, the distribution of discrete, unconnected light spots projected by each of one or more structured light projectors includes the distribution of discrete, unconnected light spots projected by each of multiple structured light projectors, wherein each light spot projected from a particular structured light projector has the same shape, and the shape of the light spot projected from at least one structured light projector is different from the shape of the light spot projected from at least one other structured light projector.

[0132] For some applications, the method also includes:

[0133] Drive at least one uniform light projector to project white light onto a three-dimensional surface within the mouth; and

[0134] At least one camera is driven to capture two-dimensional color images of the three-dimensional surface inside the mouth using illumination from a uniform light projector.

[0135] For some applications, the method also includes using a processor to run a surface reconstruction algorithm that combines at least one image captured using illumination from a structured light projector with multiple images captured using illumination from a uniform light projector to generate a three-dimensional image of the intraoral three-dimensional surface.

[0136] For some applications, each of driving one or more structured light projectors includes driving multiple structured light projectors to simultaneously project a distribution of corresponding discrete, unconnected light spots onto a three-dimensional surface within the mouth.

[0137] For some applications, each of driving one or more structured light projectors includes driving multiple structured light projectors to project corresponding discrete, unconnected light spots onto the three-dimensional surface within the mouth at different times.

[0138] For some applications, driving multiple structured light projectors to project corresponding discrete, unconnected light spots onto a three-dimensional surface within the mouth at different times includes driving multiple structured light projectors to project corresponding discrete, unconnected light spots onto a three-dimensional surface within the mouth in a predetermined order.

[0139] For some applications, driving multiple structured light projectors to project corresponding discrete, unconnected light spots onto the intraoral three-dimensional surface at different times includes:

[0140] Drive at least one structured light projector to project a discrete distribution of unconnected light points onto a three-dimensional surface within the mouth; and

[0141] During the scan, it is determined which of the multiple structured light projectors will be driven next to project a distribution of discrete, unconnected light spots.

[0142] For some applications:

[0143] Each of driving one or more structured light projectors includes driving exactly one structured light projector to project a discrete distribution of unconnected light spots onto a three-dimensional surface within the mouth.

[0144] For some applications, driving one or more cameras involves driving one or more cameras at a frame rate of 30-200 frames per second so that each captures an image.

[0145] For some applications, driving one or more cameras involves driving one or more cameras at a frame rate of at least 75 frames per second so that each captures an image.

[0146] For some applications, driving one or more cameras involves driving one or more cameras at a frame rate of at least 100 frames per second so that each captures an image.

[0147] For some applications, the processor uses data received from a temperature sensor indicating the temperature of the structured light projector and camera to select among multiple sets of stored calibration data corresponding to multiple corresponding temperatures of the structured light projector and camera, each set of stored calibration data for the corresponding temperature indication (a) projector light corresponding to each projected light spot from each of one or more projectors, and (b) camera light corresponding to each pixel on the camera sensor of each of one or more cameras.

[0148] For some applications, the processor uses data received from temperature sensors indicating the temperature of the structured light projector and camera to interpolate between multiple sets of stored calibration data to obtain calibration data for the temperature range corresponding to each set of calibration data.

[0149] For some applications:

[0150] Driving one or more cameras includes driving each of one or more cameras to capture an image, the image also including at least one region of a diffuser having multiple regions, such that:

[0151] (a) Each projector has at least one diffuse reflector region in its illumination field.

[0152] (b) Each camera has at least one diffuser area in its field of view, and

[0153] (c) Multiple diffuser regions are in the field of view of one of the cameras and in the illumination field of one of the projectors.

[0154] The processor can be used to (a) receive data from the camera indicating the location of the diffuser relative to the distribution of discrete, unconnected light points, (b) compare the received data with the stored calibration location of the diffuser, (i) use the difference between the received data indicating the location of the diffuser and (ii) the stored calibration location of the diffuser to indicate the offset of the projector ray and the camera ray from their respective stored calibration values, and (c) run a corresponding algorithm based on the offset of the projector ray and the camera ray from their respective stored calibration values.

[0155] In some embodiments, such as any of those described above or the entire specification, combined structured illumination using light field imaging can provide high dynamic range 3D imaging. A stripe pattern can be projected onto the scene and modulated by the scene depth. The structured light field can then be detected using a light field recording device. The structured light field contains information about the direction and phase-encoded depth of the rays, which allows for estimation of the scene depth from different directions. Multi-directional depth estimation can effectively achieve high dynamic range 3D imaging.

[0156] Applications of the present invention may also include systems and methods relating to a three-dimensional intraoral scanning apparatus, which includes one or more light field cameras and one or more pattern projectors. For example, in some embodiments, an intraoral scanning apparatus is provided. The apparatus may include an elongated handheld rod including a probe at its distal end. The probe may have a proximal end and a distal end. During intraoral scanning, the probe may be placed in the oral cavity of a subject. According to some applications of the present invention, a structured light projector and a light field camera may be positioned proximally to the probe, and a mirror may be positioned distally to the probe. The structured light projector and the light field camera may be positioned facing the mirror, and the mirror is positioned to (a) reflect light from the structured light projector directly onto the object being scanned, and (b) reflect light from the object being scanned onto the light field camera.

[0157] The structured light projector in the proximal end of the probe includes a light source. In some applications, the light source may have an illumination field of at least 6 degrees and / or less than 30 degrees. The structured light projector can focus light from the light source onto a projector focal plane at a distance of at least 30 mm and / or less than 140 mm from the light source. The structured light projector may also include a pattern generator disposed in the optical path between the light source and the projector focal plane. When the light source is activated to emit light through the pattern generator, the pattern generator generates a structured light pattern at the projector focal plane.

[0158] In some applications, the light field camera in the proximal end of the probe can have a field of view of at least 6 degrees and / or less than 30 degrees. The light field camera can be focused at a focal plane at a distance of at least 30 mm and / or less than 140 mm from the camera. The light field camera may also include a light field camera sensor comprising (i) an image sensor including an array of sensor pixels, and (ii) a microlens array disposed in front of the image sensor, such that each microlens is disposed on a subarray of sensor pixels. An objective lens disposed in front of the light field camera sensor forms an image of the scanned object onto the light field camera sensor.

[0159] According to some applications of the invention, one or more structured light projectors and one or more light field cameras are disposed at the distal end of the probe. The structured light projectors and light field cameras are positioned such that each structured light projector directly faces an object placed outside the rod within its illumination field, and each camera directly faces an object placed outside the rod within its field of view. At least 40% of the projected structured light pattern from each projector is within the field of view of at least one camera.

[0160] One or more structured light projectors at the distal end of the probe each include a light source. In some applications, each structured light projector may have an illumination field of at least 60 degrees and / or less than 120 degrees. Each structured light projector can focus light from the light source onto a projector focal plane at a distance of at least 30 mm and / or less than 140 mm from the light source. Each structured light projector may also include a pattern generator disposed in the optical path between the light source and the projector focal plane, which generates a structured light pattern at the projector focal plane when the light source is activated to emit light through it.

[0161] In some applications, one or more light field cameras at the distal end of the probe may each have a field of view of at least 60 degrees and / or less than 120 degrees. Each light field camera may be focused at a focal plane at a distance of at least 3 mm and / or less than 40 mm from the light field camera. Each light field camera may also include a light field camera sensor comprising (i) an image sensor including an array of sensor pixels, and (ii) an array of microlenses disposed in front of the image sensor, such that each microlens is disposed on a subarray of sensor pixels. An objective lens disposed in front of each light field camera sensor forms an image of the scanned object onto the light field camera sensor.

[0162] Therefore, according to some applications of the present invention, an apparatus for intraoral scanning is provided, the apparatus comprising:

[0163] (A) A slender handheld rod, including a probe located at the distal end of the handheld rod, the probe having a proximal end and a distal end; (B) A structured light projector disposed at the proximal end of the probe, the structured light projector:

[0164] (a) An irradiation field with a temperature of 6 to 30 degrees.

[0165] (b) Includes the light source, and

[0166] (c) Configured to focus light from the light source onto the projector focal plane between 30 mm and 140 mm from the light source, and

[0167] (d) includes a pattern generator disposed in the optical path between the light source and the focal plane of the projector, the pattern generator being configured to generate a structured light pattern at the focal plane of the projector when the light source is activated to emit light through the pattern generator.

[0168] (C) A light field camera, positioned near the probe, wherein the light field camera:

[0169] (a) Has a field of view of 6 to 30 degrees.

[0170] (b) Configured to focus on the focal plane of the camera at a distance of 30mm to 140mm from the light field camera.

[0171] (c) Includes a light field camera sensor, the light field camera sensor comprising (i) an image sensor including an array of sensor pixels, and (ii) a microlens array disposed in front of the image sensor, such that each microlens is disposed on a subarray of sensor pixels, and

[0172] (d) Includes an objective lens, positioned in front of the light field camera sensor, and configured to be scanned.

[0173] An image of the object is formed onto a light field camera sensor; and

[0174] (D) A mirror, positioned at the far end of the handheld stick.

[0175] The structured light projector and the light field camera are positioned to face the mirror, and the mirror is positioned to (a) reflect light from the structured light projector directly onto the object being scanned, and (b) reflect light from the object being scanned into the light field camera.

[0176] For some applications, the light source includes light-emitting diodes (LEDs), and the pattern generator includes a mask.

[0177] For some applications, the light source includes laser diodes.

[0178] For some applications, the pattern generator includes a diffractive optical element (DOE) configured to generate structured light patterns as a distribution of discrete, unconnected light points.

[0179] For some applications, pattern generators include refractive microlens arrays.

[0180] For some applications, the probe height is 14-17mm and the probe width is 18-22mm. This height and width define a plane perpendicular to the longitudinal axis of the rod. Light enters the probe through the lower surface of the probe and the height of the probe is measured from the lower surface of the probe to the upper surface of the probe opposite to the lower surface.

[0181] For some applications, the device is configured to be used with an output device, and the device also includes:

[0182] The control circuit is configured as follows:

[0183] (a) Drive the structured light projector to project the structured light pattern onto the object outside the rod.

[0184] (b) Driving a light field camera to capture a light field generated by a structured light pattern reflected from an object, the light field including (i) the intensity of the structured light pattern reflected from the object, and (ii) the direction of the light rays; and

[0185] At least one computer processor is configured to reconstruct a three-dimensional image of the surface of the scanned object based on the captured light field and output the image to an output device.

[0186] For some applications:

[0187] (a) The object outside the stick is the subject's teeth inside his mouth.

[0188] (b) The control circuit is configured to drive the light field camera to capture a light field generated by a structured light pattern reflected from the teeth in the absence of powder on the teeth, and

[0189] (c) The computer processor is configured to reconstruct a three-dimensional image of the tooth based on a light field captured in the absence of powder on the tooth, and output the image to an output device.

[0190] For some applications, the subarray of each sensor pixel in the central region of the image sensor includes 10-40% fewer pixels than the subarray of each sensor pixel in the peripheral region of the image sensor, and the central region of the image sensor includes at least 50% of the total number of sensor pixels.

[0191] For some applications, (a) each microlens on a subarray of sensor pixels in the peripheral region of an image sensor is configured to focus to a depth 1.1 to 1.4 times greater than (b) each microlens on a subarray of sensor pixels in the central region of an image sensor is configured to focus to a depth 1.1 to 1.4 times greater.

[0192] According to some applications of the present invention, an apparatus is also provided, comprising:

[0193] (A) A slender handheld rod, including a probe located at the distal end of the handheld rod, the probe having a proximal end and a distal end; (B) one or more structured light projectors disposed at the distal end of the probe, each structured light projector:

[0194] (a) An irradiation field with a temperature of 60 to 120 degrees.

[0195] (b) Includes the light source, and

[0196] (c) Configured to focus light from the light source onto the projector focal plane between 3 mm and 40 mm from the light source, and

[0197] (d) Includes a pattern generator disposed in the optical path between the light source and the focal plane of the projector, the pattern generator being configured to, when the light source is activated to emit light passing through the pattern generator, generate light in the projection...

[0198] Structured light patterns are generated at the focal plane of the instrument; and

[0199] (C) One or more light field cameras, positioned at the far end of the probe, each light field camera:

[0200] (a) Has a field of view of 60 to 120 degrees,

[0201] (b) is configured to focus on the camera's focal plane at a distance of 3mm to 40mm from the light field camera.

[0202] (c) Includes a light field camera sensor, the light field camera sensor comprising (i) an image sensor including an array of sensor pixels, and (ii) a microlens array disposed in front of the image sensor, such that each microlens is disposed on a subarray of sensor pixels, and

[0203] (d) Includes an objective lens, positioned in front of the light field camera sensor, and configured to form an image of the object to be scanned onto the light field camera sensor; and

[0204] The structured light projectors and light field cameras are positioned such that (a) each structured light projector is directly facing an object placed outside the rod in its illumination field, (b) each camera is directly facing an object placed outside the rod in its field of view, and (c) at least 40% of the structured light pattern from each projector is located in the field of view of at least one camera.

[0205] For some applications, the probe height is 10-14 mm and the probe width is 18-22 mm. This height and width define a plane perpendicular to the longitudinal axis of the rod. Light enters the probe through the lower surface of the probe and the height of the probe is measured from the lower surface of the probe to the upper surface of the probe opposite to the lower surface.

[0206] For some applications, one or more structured light projectors are exactly one structured light projector, and one or more structured light field cameras are exactly one light field camera.

[0207] For some applications, one or more structured light projectors are multiple structured light projectors, and one or more light field cameras are multiple light field cameras.

[0208] For some applications, the device is configured to be used with an output device, and the device also includes:

[0209] The control circuit is configured as follows:

[0210] (a) Each of one or more structured light projectors projects a structured light pattern onto an object outside the rod.

[0211] (b) Driving one or more light field cameras to capture a light field generated by a structured light pattern reflected from an object, the light field including (i) the intensity of the structured light pattern reflected from the object, and (ii) the direction of the light rays; and

[0212] At least one computer processor is configured to reconstruct a three-dimensional image of the surface of the scanned object based on the captured light field and output the image to an output device.

[0213] For some applications:

[0214] At least one of the one or more structured light projectors is a monochromatic structured light projector, configured to project a monochromatic structured light pattern onto the scanned object.

[0215] At least one of the one or more light field cameras is a monochromatic light field camera, configured to capture a light field generated by a monochromatic structured light pattern reflected from a scanned object, and

[0216] The device also includes: (a) a light source configured to emit white light onto the object being scanned; and (b) a camera configured to capture a two-dimensional color image of the object being scanned.

[0217] For some applications, monochromatic structured light projectors are configured to project structured light patterns at wavelengths of 420-470 nm.

[0218] According to some applications of the present invention, an apparatus is also provided, comprising:

[0219] (A) A slender handheld rod, including a probe located at the distal end of the handheld rod, the probe having a proximal end and a distal end; (B) A structured light projector disposed at the proximal end of the probe, the structured light projector:

[0220] (a) has an irradiation field,

[0221] (b) Includes the light source, and

[0222] (c) is configured to focus light from the light source onto the focal plane of the projector, and

[0223] (d) Includes a pattern generator disposed in the optical path between the light source and the focal plane of the projector, the pattern generator being configured to generate a structured light pattern at the focal plane of the projector when the light source is activated to emit light through the pattern generator.

[0224] (C) A light field camera, positioned near the probe, wherein the light field camera:

[0225] (a) Has a field of view,

[0226] (b) is configured to focus on the camera's focal plane.

[0227] (c) Includes a light field camera sensor, the light field camera sensor comprising (i) an image sensor including an array of sensor pixels, and (ii) a microlens array disposed in front of the image sensor, such that each microlens is disposed on a subarray of sensor pixels, and

[0228] (d) Includes an objective lens, positioned in front of the light field camera sensor, and configured to form an image of the object to be scanned onto the light field camera sensor; and

[0229] (D) A mirror, positioned at the far end of the handheld stick.

[0230] The structured light projector and the light field camera are positioned to face the mirror, and the mirror is positioned to (a) reflect light from the structured light projector directly onto the object being scanned, and (b) reflect light from the object being scanned into the light field camera.

[0231] According to some applications of the present invention, an apparatus is also provided, comprising:

[0232] (A) A slender handheld rod, including a probe located at the distal end of the handheld rod, the probe having a proximal end and a distal end; (B) one or more structured light projectors disposed at the distal end of the probe, each structured light projector:

[0233] (a) has an irradiation field,

[0234] (b) Includes the light source, and

[0235] (c) is configured to focus light from the light source onto the focal plane of the projector, and

[0236] (d) includes a pattern generator disposed in the optical path between the light source and the focal plane of the projector, the pattern generator being configured to generate a structured light pattern at the focal plane of the projector when the light source is activated to emit light passing through the pattern generator; and

[0237] (C) One or more light field cameras, positioned at the far end of the probe, each light field camera:

[0238] (a) Has a field of view,

[0239] (b) is configured to focus on the camera's focal plane.

[0240] (c) Includes a light field camera sensor, the light field camera sensor comprising (i) an image sensor including an array of sensor pixels, and (ii) a microlens array disposed in front of the image sensor, such that each microlens is disposed on a subarray of sensor pixels, and

[0241] (d) Includes an objective lens, positioned in front of the light field camera sensor, and configured to form an image of the object to be scanned onto the light field camera sensor; and

[0242] The structured light projectors and light field cameras are positioned such that (a) each structured light projector is directly facing an object placed outside the rod in its illumination field, (b) each camera is directly facing an object placed outside the rod in its field of view, and (c) at least 40% of the structured light pattern from each projector is located in the field of view of at least one camera.

[0243] The invention will be more fully understood from the following detailed description of its application in conjunction with the accompanying drawings. Attached Figure Description

[0244] Figure 1 This is a schematic diagram of a handheld wand according to some applications of the present invention, wherein multiple structured light projectors and cameras are disposed in a probe at the distal end of the handheld wand.

[0245] Figure 2A -B are schematic diagrams of the positioning configurations of cameras and structured light projectors according to some applications of the present invention;

[0246] Figure 2C These are diagrams depicting various configurations of the positions of the structured light projector and camera in a probe, according to some applications of the present invention.

[0247] Figure 3 This is a schematic diagram of a structured light projector for some applications according to the present invention;

[0248] Figure 4 This is a schematic diagram of a structured light projector according to some applications of the present invention, which projects a discrete distribution of unconnected light points onto a focal plane of multiple objects;

[0249] Figure 5A -B is a schematic diagram of a structured light projector according to some applications of the present invention, the structured light projector including a beam shaping optics element and an additional optics element disposed between the beam shaping optics element and the pattern generating optics element;

[0250] Figure 6A -B is a schematic diagram of a structured light projector that projects discrete, unconnected light spots and a camera sensor that detects light spots, according to some applications of the present invention.

[0251] Figure 7 This is a flowchart outlining some applications of the present invention for a method of generating digital three-dimensional images;

[0252] Figure 8 This is an overview of some applications according to the present invention for performing Figure 7 A flowchart of a specific step in a method;

[0253] Figure 9 , Figure 10 , Figure 11 and Figure 12 This is a description of some applications according to the present invention. Figure 8 A simplified example of the steps is illustrated in the diagram.

[0254] Figure 13This is a flowchart outlining other steps in a method for generating digital three-dimensional images, according to some applications of the present invention;

[0255] Figure 14 , Figure 15 , Figure 16 and Figure 17 This is a description of some applications according to the present invention. Figure 13 A simplified example of the steps is illustrated in the diagram.

[0256] Figure 18 This is a schematic diagram of a probe including a diffuse reflector for some applications according to the present invention;

[0257] Figure 19A -B is a schematic diagram of a structured light projector and a beam emitted by a laser diode for some applications according to the present invention, wherein pattern generating optical elements are shown disposed in the optical path of the beam;

[0258] Figure 20A -E is a schematic diagram of a microlens array used as a pattern-generating optical element in a structured light projector for some applications according to the present invention;

[0259] Figure 21A -C is a schematic diagram of a compound 2-D diffractive periodic structure used as a pattern-generating optical element in a structured light projector according to some applications of the present invention.

[0260] Figure 22A -B is a schematic diagram illustrating a single optical element and a structured light projector including the optical element in some applications according to the present invention, the single optical element having an aspherical first side and a planar second side opposite to the first side;

[0261] Figure 23A -B is a schematic diagram of an axial cone lens and a structured light projector including an axial cone lens, according to some applications of the present invention;

[0262] Figure 24A -B is a schematic diagram illustrating an optical element and a structured light projector including an optical element for some applications according to the present invention, the optical element having an aspherical surface on a first side and a flat surface on a second side opposite to the first side;

[0263] Figure 25 This is a schematic diagram of a single optical element in a structured light projector according to some applications of the present invention;

[0264] Figure 26A -B is a schematic diagram of a structured light projector having more than one laser diode according to some applications of the present invention;

[0265] Figure 27A -B is a schematic diagram illustrating different ways of combining laser diodes of different wavelengths according to some applications of the present invention;

[0266] Figure 28A This is a schematic diagram of a handheld stick according to some applications of the present invention, wherein a structured light projector and a light field camera are disposed at the near end of the handheld stick, and a mirror is disposed in a probe at the far end of the handheld stick.

[0267] Figure 28B This is according to some applications of the present invention. Figure 28A A schematic diagram of a handheld probe, showing the probe inside the subject's mouth;

[0268] Figure 29A -B is a schematic diagram of a structured light projector according to some applications of the present invention;

[0269] Figure 30 This is a schematic diagram of a light field camera and a captured three-dimensional object according to some applications of the present invention;

[0270] Figure 31 This is a schematic diagram of a handheld stick according to some applications of the present invention, the handheld stick having a structured light projector and a light field camera disposed within a probe at the distal end of the handheld stick; and

[0271] Figure 32 This is a schematic diagram of a handheld stick according to some applications of the present invention, wherein a plurality of structured light projectors and a light field camera are disposed in a probe at the distal end of the handheld stick. Detailed Implementation

[0272] Now for reference Figure 1 , Figure 1 This is a schematic diagram of an elongated handheld stick 20 for intraoral scanning according to some applications of the present invention. Multiple structured light projectors 22 and multiple cameras 24 are integrated into a rigid structure 26 disposed within a probe 28 at the distal end 30 of the handheld stick. In some applications, the probe 28 enters the subject's oral cavity during intraoral scanning.

[0273] For some applications, the structured light projectors 22 are located within the probe 28, such that each structured light projector 22 faces an object 32 placed outside the handheld stick 20 within its illumination field, rather than positioning the structured light projector in the proximal end of the handheld stick and illuminating the object by reflecting light through a mirror and then onto the object. Similarly, for some applications, the cameras 24 are located within the probe 28, such that each camera 24 faces an object 32 placed outside the handheld stick 20 within its field of view, rather than positioning the camera in the proximal end of the handheld stick and observing the object by reflecting light into the camera through a mirror. This positioning of the projectors and cameras within the probe 28 allows the scanner to have a large overall field of view while maintaining a low-profile probe.

[0274] In some applications, the height H1 of the probe 28 is less than 15 mm. The height H1 of the probe 28 is measured from the lower surface 176 (sensing surface) to the upper surface 178 opposite to the lower surface 176. Reflected light from the scanned object 32 enters the probe 28 through the lower surface 176. In some applications, the height H1 is between 10 and 15 mm.

[0275] In some applications, each of the cameras 24 has a large field of view β(beta) of at least 45 degrees, for example, at least 70 degrees, for example, at least 80 degrees, for example, 85 degrees. In some applications, the field of view may be less than 120 degrees, for example, less than 100 degrees, for example, less than 90 degrees. In experiments conducted by the inventors, a field of view β(beta) between 80 and 90 degrees for each camera was found to be 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 optics 60 comprising one or more lenses. To enable near-focus imaging, the camera 24 may be focused at an object focal plane 50, which is between 1 mm and 30 mm away from the lens furthest from the camera sensor, for example, between 4 mm and 24 mm, for example, between 5 mm and 11 mm, for example, 9 mm-10 mm. In experiments conducted by the inventors, the focal plane 50 of the object, located between 5mm and 11mm from the lens at its furthest point from the camera sensor, was found to be particularly useful because teeth are easily scanned at this distance, and because the focus is good on most tooth surfaces. In some applications, the camera 24 can capture images at a frame rate of at least 30 frames per second, for example, at a frame rate of at least 75 frames per second, or even at a frame rate of at least 100 frames per second. In some applications, the frame rate can be less than 200 frames per second.

[0276] As mentioned above, a large field of view 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, especially in edentulous regions where the gingival surface is smooth and there may be fewer sharp, high-resolution 3D features. A larger field of view allows large, smooth features, such as the overall curve of the teeth, to appear in each image frame, which improves the accuracy of stitching individual surfaces obtained from multiple such image frames.

[0277] Similarly, each structured light projector 22 can have a large illumination field α(alpha) of at least 45 degrees, for example, at least 70 degrees. In some applications, the illumination field α(alpha) can be less than 120 degrees, for example, less than 100 degrees. Other features of the structured light projector 22 are described below.

[0278] For some applications, to improve image capture, each camera 24 has multiple discrete preset focus positions, at each focus position the camera focuses on the corresponding object focal plane 50. Each camera 24 may include an autofocus actuator that selects the 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, such that the image formed by each camera remains in focus across all object distances between 1 mm and 30 mm from the lens furthest from the camera sensor, for example, between 4 mm and 24 mm, for example, between 5 mm and 11 mm, for example, between 9 mm and 10 mm.

[0279] In some applications, the structured light projector 22 and camera 24 are combined to the rigid structure 26 in a close-packed and / or alternating manner, such that (a) the main portion of the field of view of each camera overlaps with the field of view of a neighboring camera, and (b) the main portion of the field of view of each camera overlaps with the illumination field of a neighboring projector. Optionally, at least 20%, for example, at least 50%, for example, at least 75% of the projected light pattern is in the field of view of at least one camera at the object focal plane 50, which is at least 4 mm away from the lens furthest from the camera sensor. Due to the possible different 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 by the object 32 and cannot be observed during scanning when the scanner is moved.

[0280] The rigid structure 26 can be a non-flexible structure to which the structured light projector 22 and camera 24 are integrated to provide structural stability for the optics within the probe 28. Integrating all projectors and cameras into a common rigid structure helps maintain the geometric integrity of the optics of each structured light projector 22 and each camera 24 under varying environmental conditions, such as mechanical stresses that may be induced by the subject's mouth. Additionally, the rigid structure 26 helps maintain the stable structural integrity and positioning of the structured light projectors 22 and cameras 24 relative to each other. As further described below, controlling the temperature of the rigid structure 26 helps 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 the scan.

[0281] Now for reference Figure 2A -B, Figure 2A -B are schematic diagrams illustrating the positioning configurations of the camera 24 and the structured light projector 22 according to some applications of the present invention. For some applications, to improve the overall field of view and illumination field of the intraoral scanner, the camera 24 and the structured light projector 22 are positioned such that they do not both face the same direction. For some applications, such as... Figure 2A As shown, multiple cameras 24 are integrated into a rigid structure 26 such that the angle θ (theta) between two corresponding optical axes 46 of at least two cameras 24 is 90 degrees or less, for example, 35 degrees or less. Similarly, for some applications, such as... Figure 2B As shown, a plurality of structured light projectors 22 are integrated into a rigid structure 26 such that the angle between two corresponding optical axes 48 of at least two structured light projectors 22 is such that... It is 90 degrees or less, such as 35 degrees or less.

[0282] Now for reference Figure 2C , Figure 2C This is a diagram depicting various different configurations of the positions of the structured light projector 22 and the camera 24 in a probe 28 according to some applications of the present invention. The structured light projector 22 is... Figure 2C The circle indicates that camera 24 is in Figure 2C Rectangles are used to represent the cameras. Note that rectangles are used to represent cameras because, typically, the field of view β (beta) of each camera sensor 58 and each camera 24 has an aspect ratio of 1:2. Figure 2C Column (a) shows a bird's-eye view of various configurations of the structured light projector 22 and camera 24. The x-axis marked in the first row of column (a) corresponds to the central longitudinal axis of the probe 28. Column (b) shows a side view of various configurations of the camera 24 as seen from a line of sight coaxial with the central longitudinal axis of the probe 28. Similar to Figure 2A , Figure 2CColumn (b) shows camera 24 positioned such that optical axes 46 are at an angle of 90 degrees or less relative to each other, such as 35 degrees or less. Column (c) shows side views of various configurations of camera 24 as viewed from a line of sight perpendicular to the central longitudinal axis of probe 28.

[0283] Typically, the farthest side (towards) Figure 2C (in the positive x direction) and the nearest side (towards) Figure 2C The negative x-direction cameras 24 are positioned such that their optical axes 46 are slightly rotated inward relative to the nearest adjacent camera 24, for example, at an angle of 90 degrees or less, such as 35 degrees or less. The more central cameras 24, i.e., neither the farthest nor the closest cameras 24, are positioned such that they face directly outward from the probe, and their optical axes 46 are 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 farthest point of the probe 28, and therefore the optical axis 48 of this projector 22 points inward, allowing a greater number of light spots 33 projected from this particular projector 22 to be seen by more cameras 24.

[0284] Typically, the number of structured light projectors 22 in probe 28 can range from two (e.g., as...). Figure 2C The number of cameras 24 in probe 28 typically ranges from four (as shown in rows (iv) and (v)) to seven (as shown in row (ix)). Note that Figure 2C The various configurations shown are merely examples and not limitations, and the scope of the invention includes additional configurations not shown. For example, the scope of the invention includes more than five projectors 22 located in probe 28 and more than seven cameras located in probe 28.

[0285] In an exemplary application, an apparatus for intraoral scanning (e.g., an intraoral scanner) includes an elongated handheld rod comprising: a probe located at the distal end of the elongated handheld rod; 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 optics configured to generate a light pattern when light is emitted through the pattern-generating optics. 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 multiple images depicting at least a portion of a light pattern projected onto an intraoral surface. Most of the at least two light projectors and at least four cameras may be arranged in at least two rows, each row being generally parallel to the longitudinal axis of the probe, the at least two rows including at least a first row and a second row.

[0286] In further applications, the farthest and nearest cameras along the longitudinal axis of at least four cameras are positioned such that, from a line of sight perpendicular to the longitudinal axis, their optical axes form an angle of 90 degrees or less relative to each other. Cameras in the first and second rows can be positioned such that, from a line of sight coaxial with the probe's longitudinal axis, the optical axes of the cameras in the first row form an angle of 90 degrees or less relative to the optical axes of the cameras in the second row. The remaining portions of the at least four cameras, excluding the farthest and nearest cameras, have optical axes substantially parallel to the probe's longitudinal axis. Each of the at least two rows may include an alternating sequence of light projectors and cameras.

[0287] In further applications, at least four cameras include at least five cameras, at least two light projectors include at least five light projectors, the nearest-side component in the first row is a light projector, and the nearest-side component in the second row is a camera.

[0288] In further applications, the farthest camera along the vertical axis and the nearest camera along the vertical axis are positioned such that, from a line of sight perpendicular to the vertical axis, their optical axes are at an angle of 35 degrees or less relative to each other. The cameras in the first row and the cameras in the second row can be positioned such that, from a line of sight coaxial with the probe's vertical axis, the optical axis of the camera in the first row is at an angle of 35 degrees or less relative to the optical axis of the camera in the second row.

[0289] In further applications, corresponding to the distance from the probe, at least four cameras can have a combined field of view of 25-45mm along the longitudinal axis and a field of view of 20-40mm along the z-axis.

[0290] Now for reference Figure 3 , Figure 3 This is a schematic diagram of a structured light projector 22 according to some applications of the present invention. In some applications, the structured light projector 22 includes a laser diode 36, a beam shaping optics element 40, and a pattern generating optics element 38, which generates a discrete distribution 34 of unconnected light spots (refer to below). Figure 4(Further discussion follows). In some applications, the structured light projector 22 can be configured to generate a distribution 34 of discrete, unconnected light points at all planes between 1 mm and 30 mm (e.g., 4 mm and 24 mm) of the pattern-generating optics 38 when the laser diode 36 emits light through the pattern-generating optics 38. For some applications, the distribution 34 of discrete, unconnected light points is focused on one plane located between 1 mm and 30 mm (e.g., between 4 mm and 24 mm), while all other planes located between 1 mm and 30 mm, such as those between 4 mm and 24 mm, still contain discrete, unconnected light points. Although the above description uses a laser diode, it should be understood that this is an exemplary and non-limiting application. Other light sources can be used in other applications. Furthermore, although described as a pattern projecting discrete, unconnected light points, it should be understood that this is an exemplary and non-limiting application. Other light patterns or arrays, including but not limited to lines, grids, checkerboards, and other arrays, can be used in other applications.

[0291] The pattern generating optical element 38 can be configured to have a light throughput efficiency of at least 80%, for example, at least 90% (i.e., the ratio of light entering the pattern to the total light falling on the pattern generating optical element 38).

[0292] For some applications, the corresponding laser diodes 36 of each structured light projector 22 emit light of different wavelengths; that is, the corresponding laser diodes 36 of at least two structured light projectors 22 emit light of two different wavelengths respectively. For some applications, the corresponding laser diodes 36 of at least three structured light projectors 22 emit light of three different wavelengths respectively. For example, red, blue, and green laser diodes can be used. For some applications, the corresponding laser diodes 36 of at least two structured light projectors 22 emit light of two different wavelengths respectively. For example, in some applications, six structured light projectors 22 are arranged within the probe 28, three of which contain blue laser diodes and three of which contain green laser diodes.

[0293] Now for reference Figure 4 , Figure 4This is a schematic diagram of a structured light projector 22 according to some applications of the present invention, which projects a discrete distribution of unconnected light points onto a focal plane of multiple objects. The scanned objects 32 may be one or more teeth or other intraoral objects / tissues within the subject's mouth. Some translucent and smooth properties of teeth may affect the contrast of the projected structured light pattern. For example, (a) some light hitting the teeth may scatter into other areas within the intraoral scene, resulting in a certain amount of stray light, and (b) some light may penetrate the teeth and subsequently exit from the teeth at any other point. Therefore, without using contrast enhancement devices such as coating teeth with opaque powder, the inventors have recognized that a sparse distribution 34 of discrete unconnected light points can provide an improved balance between reducing the amount of projected light and maintaining the amount of useful information in order to improve image capture of intraoral scenes under structured light illumination. The sparsity of the distribution 34 can be characterized by the ratio of (a) to (b):

[0294] (a) The irradiated area on the orthogonal plane 44 in the irradiation field α(alpha), i.e., the irradiation field α(alpha).

[0295] The sum of the areas of all projected light points 33 on the orthogonal plane 44 in the middle,

[0296] (b) The non-irradiated area on the orthogonal plane 44 in the irradiation field α. In some applications, the sparsity ratio may be at least 1:150 and / or less than 1:16 (e.g., at least 1:64 and / or less than 1:36).

[0297] In some applications, during scanning, each structured light projector 22 projects at least 400 discrete, unconnected light spots 33 onto the intraoral 3D surface. In other applications, during scanning, each structured light projector 22 projects fewer than 3000 discrete, unconnected light spots 33 onto the intraoral surface. To reconstruct the 3D surface from the sparse distribution 34 of the projected light spots, the correspondence between the individual projected light spots 33 and the light spots detected by the camera 24 must be determined, as referenced below. Figures 7 to 1 9. Further description.

[0298] For some applications, pattern generating optical element 38 is a diffractive optical element (DOE) 39. Figure 3When the laser diode 36 emits light through the DOE and reaches the object 32, the DOE generates a distribution 34 of discrete, unconnected light spots 33. As used throughout this application, including in the claims, a light spot is defined as a small area of ​​light having any shape. For some applications, the corresponding DOEs 39 of different structured light projectors 22 generate light spots with different corresponding shapes, i.e., each light spot 33 generated by a particular DOE 39 has the same shape, and the shape of the light spot 33 generated by at least one DOE 39 is different from the shape of the light spot 33 generated by at least one other DOE 39. For example, some of the DOEs 39 may generate circular light spots 33 (e.g., circular light spots 33). Figure 4 As shown in the diagram, some DOE 39s can generate square dots, and some DOE 39s can generate elliptical dots. Optionally, some DOE 39s can generate connected or unconnected line patterns.

[0299] Now for reference Figure 5A -B, Figure 5A -B is a schematic diagram of a structured light projector 22 according to some applications of the present invention, which includes a beam-shaping optics element 40 and an additional optics element disposed between the beam-shaping optics element 40 and a pattern-generating optics element 38 (e.g., DOE 39). Optionally, the beam-shaping optics element 40 is a collimating lens 130. The collimating lens 130 can be configured to have a focal length of less than 2 mm. Optionally, the focal length can be at least 1.2 mm. For some applications, when the laser diode 36 emits light through the optics element 42, the additional optics element 42 disposed between the beam-shaping optics element 40 and the pattern-generating optics element 38 (e.g., DOE 39) generates a Bessel beam. In some applications, the Bessel beam is transmitted through DOE 39 such that all discrete, unconnected light spots 33 maintain a small diameter (e.g., less than 0.06 mm, less than 0.04 mm, less than 0.02 mm) through a series of orthogonal planes 44 (e.g., each orthogonal plane is located between 1 mm and 30 mm from DOE 39, e.g., between 4 mm and 24 mm from DOE 39, etc.). In the context of this patent application, the diameter of the light spot 33 is defined as the full width at half maximum (FWHM) of the light spot intensity.

[0300] Although all the light spots described above are less than 0.06 mm, some light spots with diameters close to the upper end of these ranges (e.g., only slightly less than 0.06 mm or 0.02 mm) and also near the edge of the illumination field of projector 22 can be extended when they intersect a geometric plane orthogonal to DOE 39. In this case, it is useful to measure their diameters when they intersect the inner surface of a geometric sphere centered on DOE 39 with a radius between 1 mm and 30 mm, which corresponds to a distance from the corresponding orthogonal plane between 1 mm and 30 mm from DOE 39. As used throughout this application, including in the claims, the term "geometry" is used in relation to theoretical geometric constructions (e.g., planes or spheres) and is not part of any physical device.

[0301] For some applications, when a Bessel beam is transmitted through DOE 39, in addition to a spot with a diameter less than 0.06 mm, a spot 33 with a diameter greater than 0.06 mm is also generated.

[0302] For some applications, optical element 42 is an axonoconical lens 45, for example... Figure 5A As shown and as referenced below Figure 23A -B further described. Alternatively, optical element 42 can be an annular aperture ring 47, for example... Figure 5B As shown in the diagram. Maintaining a small-diameter spot improves the three-dimensional resolution and accuracy throughout the depth of focus. In the absence of optical element 42 (e.g., a cone lens 45 or annular aperture ring 47), the size of spot 33 can change, for example, become larger, as you move away from the optimal focusing plane due to diffraction and defocus.

[0303] Now for reference Figure 6A -B, Figure 6A -B is a schematic diagram of a structured light projector 22 that projects discrete, unconnected light spots 33 and a camera sensor 58 that detects light spots 33' according to some applications of the present invention. For some applications, a method is provided for determining the correspondence between projected light spots 33 on an intraoral surface and detected light spots 33' on the corresponding camera sensor 58. Once the correspondence is determined, a three-dimensional image of the surface is reconstructed. Each camera sensor 58 has a pixel array, and for each pixel there exists a corresponding camera ray 86. Similarly, for each projected light spot 33 from each projector 22, there exists 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 light spot 33' projected by a particular projector ray 88, then that light spot 33' will necessarily be detected by a pixel on a particular path 92 of the pixel corresponding to that particular projector ray 88. See details Figure 6B The diagram illustrates the correspondence between each projector ray 88 and its corresponding camera sensor path 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 light spot into a dusty space, a dust line in the air will be illuminated. This dust line, detected by camera sensor 58, will follow the same path on camera sensor 58 as the camera sensor path 92 corresponding to that particular projector ray 88.

[0304] During the calibration process, calibration values ​​are stored based on camera rays 86 corresponding to pixels on the camera sensor 58 of each camera 24 and projector rays 88 corresponding to projection points 33 from each structured light projector 22. For example, calibration values ​​are stored for (a) multiple camera rays 86 corresponding to corresponding multiple pixels on the camera sensor 58 of each camera 24, and (b) multiple projector rays 88 corresponding to corresponding multiple projection points 33 from each structured light projector 22.

[0305] For example, the following calibration process can be used. A high-precision point target, such as a black dot on a white background, is illuminated from below, and images of the target are captured using all cameras. The point target is then moved vertically toward the cameras, i.e., along the z-axis to the target plane. The center of each point at all corresponding z-axis positions is calculated to create a 3D grid of points in space. The pixel coordinates of each 3D position of the corresponding point center are then found using distortion and camera pinhole models, thus defining the camera ray for each pixel as a ray originating from the pixel oriented toward the corresponding point center in the 3D grid. The camera rays corresponding to pixels between grid points can be interpolated. The above camera calibration process is repeated for all corresponding wavelengths of the individual laser diodes 36, such that for each wavelength, the camera ray 86 included in the stored calibration values ​​corresponds to each pixel on each camera sensor 58.

[0306] After calibrating camera 24 and storing all camera ray values ​​86, structured light projector 22 can be calibrated as follows: A flat, featureless target is used, and one structured light projector 22 is turned on at a time. Each light spot is located on at least one camera sensor 58. Since camera 24 is now calibrated, the three-dimensional position of each light spot is calculated using triangulation based on images of light spots from multiple different cameras. The above process is repeated using featureless targets located at multiple different z-axis positions. Each projected light spot on the featureless target will be confined in space by projector rays originating from the projector.

[0307] Now for reference Figure 7 , Figure 7 This is a flowchart outlining a method for generating digital three-dimensional images, based on some applications of the present invention. Figure 7 In steps 62 and 64 of the outlined method, each structured light projector 22 is driven to project a distribution 34 of discrete, unconnected light spots 33 onto a three-dimensional surface within the mouth, and each camera 24 is driven to capture an image including at least one light spot 33. Based on stored calibration values ​​indicating (a) camera rays 86 corresponding to each pixel on the camera sensor 58 of each camera 24, and (b) projector rays 88 corresponding to each projected light spot 33 from each structured light projector 22, the processor 96 is used in step 66. Figure 1 Run the corresponding algorithm, as will be explained below. Figures 8 to 12 Further description. Once the correspondence is resolved, the three-dimensional position on the intraoral surface is calculated in step 68 and used to generate a digital three-dimensional image of the intraoral surface. Furthermore, capturing the intraoral scene using multiple cameras 24 provides a signal with noise reduction through a factor equal to the square root of the number of cameras.

[0308] Now for reference Figure 8 , Figure 8 This is an overview of some applications according to the present invention. Figure 7 The flowchart of the corresponding algorithm for step 66 is shown below. Based on the stored calibration values, all projector rays 88 are mapped to all camera rays 86 corresponding to all detected light points 33' (step 70), and all intersections 98 of at least one camera ray 86 and at least one projector ray 88 are identified. Figure 10 (Step 72). Figure 9 and Figure 10 They are Figure 8 A simplified example of steps 70 and 72 is illustrated in the diagram. Figure 9 As shown, the eight detected light spots 33' on the camera sensor 58 corresponding to camera 24 map together the three projector rays 88 with the eight camera rays 86. Figure 10 As shown, sixteen intersection points 98 were identified.

[0309] exist Figure 8 In steps 74 and 76, the processor 96 determines the correspondence between the projected light spot 33 and the detection light spot 33' in order to identify the three-dimensional position of each projected light spot 33 on the surface. Figure 11 It uses the simplified example described in the previous paragraph to depict Figure 8A schematic diagram of steps 74 and 76. 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 light point j along the camera sensor path 90 will have a camera ray 86 that intersects the given projector ray i at the 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 detect a corresponding light point k on their respective camera sensor paths 90' corresponding to the given projector ray i, whose camera ray 86' intersects the same three-dimensional point in space defined by the intersection 98. This process is repeated for all detected light points j along the camera sensor path 90, and the maximum number of cameras 24 “agree” to identify light point j as light point 33 (projected from the given projector ray i onto the surface). Figure 12 In other words, projector ray i is identified as the specific projector ray 88 that generates the detected light spot j, for which the highest number of other cameras detect the corresponding light spot k. Therefore, the three-dimensional position of light spot 33 on the surface is calculated.

[0310] For example, such as Figure 11 As shown, all four cameras detect corresponding light spots on their respective camera sensor paths corresponding to projector ray i. The corresponding camera rays intersect with projector ray i at intersection point 98, which is defined as the intersection of camera ray 86 corresponding to the detected light spot j and projector ray i. Therefore, all four cameras are said to "agree" that a light spot 33 projected by projector ray i exists at intersection point 98. However, when the process is repeated for the next light spot j', none of the other cameras detect the corresponding light spot on their respective camera sensor paths corresponding to the projector ray i, whose corresponding camera ray intersects the projector ray i at intersection 98', which is defined as the intersection of camera ray 86 (corresponding to the detected light spot j') and projector ray i. Therefore, only one camera is considered to "agree" to have light spot 33 projected by projector ray i at intersection 98', while all four cameras "agree" to have light spot 33 projected by projector ray i at intersection 98. Thus, projector ray i is identified as the specific projector ray 88 (88) that generates the detected light spot j by projecting light spot 33 onto the surface at intersection 98. Figure 12 ).according to Figure 8 Step 78, and as Figure 12 As shown, the three-dimensional position 35 on the inner surface of the outlet is calculated at intersection 98.

[0311] Now for reference Figure 13 , Figure 13 This is a flowchart outlining other steps in the corresponding algorithm according to some applications of the present invention. Once the position 35 on the surface is determined, the projected ray i of the projected light point j, as well as all camera rays 86 and 86' corresponding to light point j and corresponding light point k, are disregarded (step 80), and the corresponding algorithm is run again for the next projector ray i (step 82). Figure 14 A simplified example of the above description is depicted after removing the specific projector ray i projected at position 35, point 33. According to... Figure 13 Step 82 in the flowchart is followed, and then the corresponding algorithm is run again for the next projector ray i. For example... Figure 14 As shown, the remaining data indicates that the three cameras "agree" to have a light spot 33 at intersection 98, which is defined by the intersection of the camera ray 86 corresponding to the detected light spot j and the projector ray i. Therefore, as Figure 15 As shown, the three-dimensional position 37 is calculated at intersection 98.

[0312] like Figure 16 As shown, once the three-dimensional position 37 on the surface is determined, the projected ray i of the projected light point j, and all camera rays 86 and 86' corresponding to light point j and corresponding light point k are disregarded. The remaining data shows that there is a light point 33 projected by projector ray i at intersection 98, and the three-dimensional position 41 on the surface is calculated at intersection 98. Figure 17 As shown in the simplified example, the three projected light spots 33 of the three projector rays 88 of the structured light projector 22 are now located at three-dimensional positions 35, 37, and 41 on the surface. In some applications, each structured light projector 22 projects 400-3000 light spots 33. Once the correspondences of all projector rays 88 are resolved, a reconstruction algorithm can be used to reconstruct a digital image of the surface using the calculated three-dimensional positions of the projected light spots 33.

[0313] Refer again Figure 1For some applications, at least one uniform light projector 118 is incorporated into the rigid structure 26. The uniform light projector 118 emits white light onto the object 32 being scanned. At least one camera (e.g., one of cameras 24) is configured to capture a two-dimensional color image of the object 32 using illumination from the uniform light projector 118. The processor 96 can run a surface reconstruction algorithm that combines at least one image captured using illumination from the structured light projector 22 with multiple images captured using illumination from the uniform light projector 118 to generate a three-dimensional image of the intraoral three-dimensional surface. The 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 corresponding algorithm.

[0314] For some applications, multiple structured light projectors 22 are driven simultaneously to project their respective discrete, unconnected light spot distributions 34 onto the intraoral three-dimensional surface. Alternatively, multiple structured light projectors 22 can be driven to project their respective discrete, unconnected light spot distributions 34 onto the intraoral three-dimensional surface at different times, for example, in a predetermined order or in an order dynamically determined during scanning. Alternatively, for some applications, a single structured light projector 22 can be driven to project the distribution 34.

[0315] Dynamically determining which structured light projector 22 to activate during scanning can improve the overall signal quality of the scan, as some structured light projectors may have better signal quality in certain areas of the oral cavity compared to others. For example, when scanning the subject's upper palate (maxillary region), red projectors tend to have better signal quality than blue projectors. Additionally, areas within the oral cavity that are difficult to see during scanning may be encountered, such as areas with missing teeth or narrow gaps between molars. In these types of cases, dynamically determining which structured light projector 22 to activate during scanning allows for the activation of specific projectors that may offer better visibility.

[0316] For some applications, different structured light projectors 22 can be configured to focus on different object focal planes. Dynamically determining which structured light projector 22 to activate during scanning allows specific structured light projectors 22 to be activated based on their respective object focal planes, which depend on their distance from the area currently being scanned.

[0317] For some applications, all data points acquired at a specific time are used as rigid point clouds, and multiple such point clouds are captured at a frame rate of more than 10 captures per second. The multiple point clouds are then stitched together using a registration algorithm (e.g., Iterative Closest Point (ICP)) to create a dense point cloud. A surface reconstruction algorithm can then be used to generate a representation of the surface of object 32.

[0318] For some applications, at least one temperature sensor 52 is integrated into the rigid structure 26 and measures the temperature of the rigid structure 26. A temperature control circuit 54 disposed within the handheld stick 20 (a) receives data from the temperature sensor 52 indicating the temperature of the rigid structure 26, and (b) activates a temperature control unit 56 in response to the received data. The temperature control unit 56 (e.g., a PID controller) maintains the probe 28 at a desired temperature (e.g., between 35 and 43 degrees Celsius, between 37 and 41 degrees Celsius, etc.). Maintaining the probe 28 above 35 degrees Celsius, for example above 37 degrees Celsius, reduces fogging of the glass surface of the handheld stick 20, through which a structured light projector 22 projects light when the probe 28 enters the oral cavity, and is observed by a camera 2; the oral cavity is typically around or above 37 degrees Celsius. Maintaining the probe 28 below 43 degrees Celsius, for example below 41 degrees Celsius, prevents discomfort or pain.

[0319] In addition, to utilize stored calibration values ​​for the camera and projector beams during scanning, temperature variations in the camera 24 and structured light projector 22 can be prevented, thus maintaining the geometric integrity of the optics. Temperature variations can cause the length of the probe 28 to change due to thermal expansion, which in turn can lead to corresponding camera and projector positional shifts. Twisting may also occur due to different types of stress that may accumulate within the probe 28 during this thermal expansion, causing shifts in the angles of the corresponding camera and projector beams. Geometric changes may also occur within the camera and projector due to temperature variations. For example, the DOE 39 may expand and alter the projected pattern, temperature variations may affect the refractive index of the camera lens, or temperature variations may change the wavelength emitted by the laser diode 36. Therefore, in addition to maintaining the probe 28 within the aforementioned temperature range, the temperature control unit 56 can also prevent temperature variations in the probe 28 from exceeding 1 degree Celsius when using the handheld stick 20, thereby maintaining the geometric integrity of the optics housed within the probe 28. For example, if the temperature control unit 56 maintains the probe 28 at a temperature of 39 degrees Celsius, the temperature control unit 56 will further ensure that the temperature of the probe 28 during use is not lower than 38 degrees Celsius or higher than 40 degrees Celsius.

[0320] For some applications, probe 28 is maintained at its controlled temperature using a combination of heating and cooling. For example, temperature control unit 56 may include heaters, such as multiple heaters, and coolers, such as thermoelectric coolers. If the temperature of probe 28 drops below 38 degrees Celsius, heaters can be used to raise the temperature of probe 28, and if the temperature of probe 28 is above 40 degrees Celsius, thermoelectric coolers can be used to lower the temperature of probe 28.

[0321] Alternatively, for some applications, the probe 28 can be maintained at its controlled temperature using only heating without cooling. The use of the laser diode 36 and the diffraction and / or refraction patterning optics helps to keep the structured light projector energy-efficient, thus limiting the probe 28 from overheating during use; the laser diode 36 can emit at a power of less than 0.2 watts while emitting at high brightness, and the diffraction and / or refraction patterning optics utilize all emitted light (e.g., as opposed to a mask that blocks some light from hitting the object). However, ambient temperatures, such as those encountered inside a subject's mouth, can cause heating of the probe 28. To overcome this, heat can be drawn from the probe 28 by a thermally conductive element 94 (e.g., a heat pipe) disposed within the handheld rod 20, such that the distal end 95 of the thermally conductive element 94 contacts the rigid structure 26, and the proximal end 99 contacts the proximal end 100 of the handheld rod 20. Thus, heat is transferred from the rigid structure 26 to the proximal end 100 of the handheld rod 20. Alternatively or additionally, a fan located in the handle area 174 of the handheld stick 20 may be used to draw heat away from the probe 28.

[0322] For some applications, alternatively or additionally, in order to maintain the geometric integrity of the optics by preventing temperature changes of probe 28 from exceeding a temperature threshold, processor 96 can select from multiple sets of calibration data corresponding to different temperatures. For example, the threshold change could be 1 degree Celsius. Based on data received from temperature sensor 52 indicating the temperatures of structured light projector 22 and camera 24, processor 96 can select from multiple sets of stored calibration data corresponding to multiple corresponding temperatures of structured light projector 22 and camera 24, each set of stored calibration data indicating (a) projector light corresponding to each projected light point from each of one or more projectors, and (b) camera light corresponding to each pixel on the camera sensor of each of one or more cameras at the corresponding temperature. If processor 96 only accesses the stored calibration data for specific multiple temperatures, processor 96 can interpolate between the multiple sets of stored calibration data based on data received from temperature sensor 52 to obtain calibration data for the temperature between the corresponding temperatures of each set of calibration data.

[0323] Now for reference Figure 18 , Figure 18 This is a schematic diagram of a probe 28 for some applications according to the present invention. For some applications, the probe 28 also includes a target, such as a diffuser 170, which has a feature disposed within the probe 28 (or, as...). Figure 18As shown, multiple regions 172 adjacent to probe 28. In some applications, (a) each structured light projector 22 may have at least one region 172 of diffuser 170 in its illumination field, (b) each camera 24 may have at least one region 172 of diffuser 170 in its field of view, and (c) multiple regions 172 of diffuser 170 in the field of view of camera 24 and in the illumination field of structured light projector 22. Alternatively or additionally, in order to maintain the geometric integrity of the optics by preventing temperature changes of probe 28 from exceeding a threshold temperature change, processor 96 may (a) receive data from camera 24 indicating the position of the diffuser relative to the distribution 34 of discrete unconnected light spots 33, (b) compare the received data with the stored calibration position of diffuser 170, wherein (i) the difference between the received data indicating the position of diffuser 170 and (ii) the stored calibration position of diffuser 170 indicates the offset of projector ray 88 and camera ray 86 from their respective stored calibration values, and (c) run a corresponding algorithm based on the offset of projector ray 88 and camera ray 86.

[0324] Optionally or additionally, (i) the difference between the received data indicating the position of diffuser 170 and (ii) the stored calibration position of diffuser 170 can indicate a temperature change in probe 28. In this case, the temperature of probe 28 can be adjusted based on the comparison between the received data of diffuser 170 and the stored calibration position.

[0325] The following describes several applications of the structured light projector 22.

[0326] Now for reference Figure 19A -B, Figure 19A -B is a schematic diagram of the cross-section of a structured light projector 22 and a beam 120 emitted by laser diodes 36 according to some applications of the present invention, wherein a pattern-generating optics element 38 is shown disposed in the optical path of the beam. In some applications, each laser diode 36 emits an elliptical beam 120 having an elliptical cross-section having (a) a major axis of at least 500 micrometers and / or less than 700 micrometers and (b) a minor axis of at least 100 micrometers and / or less than 200 micrometers. For some applications, a small-area beam splitter can be used to generate a tightly focused array of light spots; for example, a DOE with a side length of less than 100 micrometers can be used to keep the projected light spots 33 tightly focused throughout the focal range of interest. However, such a small DOE will only utilize a portion of the light emitted through the elliptical laser beam 120.

[0327] Therefore, for some applications, the pattern-generating optics 38 is a segmented DOE 122, which is divided into a plurality of sub-DOE sheets 124 arranged in an array. The array of sub-DOE sheets 124 is positioned such that (a) it is contained within an elliptical laser beam 120, and (b) it utilizes a high percentage, for example, at least 50%, of the light emitted through the elliptical laser beam 120. In some applications, the array is a rectangular array comprising at least 16 and / or fewer than 72 sub-DOE sheets 124, and having a longest dimension of at least 500 micrometers and / or less than 800 micrometers. Each sub-DOE sheet 124 may have a square cross-section with sides of at least 30 micrometers and / or less than 75 micrometers in length, the cross-section being truncated perpendicular to the optical axis of the DOE.

[0328] Each sub-DOE sheet 124 generates a corresponding distribution 126 of discrete, unconnected light spots 33 in different regions 128 of the illumination field. For this application of the structured light projector 22, see the reference above. Figure 4 The distribution 34 of the discrete, unconnected light spots 33 is a combination of the corresponding distributions 126 generated by the corresponding sub-DOE slices 124. Figure 19B An orthogonal plane 44 is shown, on which are shown corresponding distributions 126 of discrete, unconnected light spots 33, each corresponding distribution 126 located in a different region 128 of the illumination field. Since each sub-DOE sheet 124 is responsible for a different region 128 of the illumination field, each sub-DOE sheet 124 is designed differently to point its corresponding distributions 126 in different directions and to avoid beam crossing to prevent overlap between projected light spots 33.

[0329] Now for reference Figure 20A -E, Figure 20A -E is a schematic diagram of a microlens array 132 as a pattern-generating optical element 38 according to some applications of the present invention. The microlens array can be used as a spot generator because it is periodic and the profile variation of each lens in the array is wavelength-scale. The spacing of the microlens array 132 is adjusted to obtain the desired angular pitch between the spots. As described above, the numerical aperture (NA) of the microlens array 132 is adjusted to provide an illumination field at the desired angle. In some applications, the NA of the microlens array 132 is at least 0.2 and / or less than 0.7. The microlens array 132 can be, for example, a hexagonal microlens array, such as... Figure 20C As shown, or a rectangular microlens array, such as Figure 20E As shown.

[0330] The structured light projector 22, which has a microlens array 132 as a pattern-generating optical element 38, may include a laser diode 36, a collimating lens 130, an aperture, and the microlens array 132. The aperture defines a small input beam diameter so as to maintain a tightly focused spot at a near-focal distance from the microlens array 132, for example, at least 1 mm and / or less than 30 mm, for example, at least 4 mm and / or less than 24 mm. Figure 20B The diagram shows a collimated laser beam illuminating a microlens array 132, which then generates a diverging beam 134. The interference of these diverging beams generates a spot array 33, for example, distributed 34. Figure 20D For some applications, the aperture is a chrome film applied to the laser diode side of the collimating lens 130. Alternatively, for some applications, the aperture is a chrome film disposed on the collimating lens side of the microlens array 132. In some applications, the aperture may span at least 10 times the spacing of the microlens array 132 and have a diameter of at least 50 micrometers and / or less than 200 micrometers.

[0331] Now for reference Figure 21A -C, Figure 21A -C is a schematic diagram of a composite two-dimensional diffraction periodic structure 136 (e.g., a diffraction grating such as a Dammann grating) as a pattern-generating optical element 38 according to some applications of the present invention. The composite diffraction periodic structure 136 may have a periodic structure feature size 137 of at least 100 nm and / or less than 400 nm. A large illumination field, as described above, can be obtained with small sub-features of about 300 nm. The period of the composite diffraction periodic structure 136 can be adjusted to provide the desired angular spacing of the projected beam.

[0332] A structured light projector 22 having a compound diffraction periodic structure 136 as a pattern-generating optical element 38 may include a laser diode 36, a collimating lens 130, an aperture, and the compound diffraction periodic structure 136. The aperture defines a small input beam diameter to maintain a tightly focused spot at a near-focal distance from the compound diffraction periodic structure 136, for example, at least 1 mm and / or less than 30 mm, or, for example, at least 4 mm and / or less than 24 mm. For some applications, the aperture is a chromium film located on the periodic structural features of the compound diffraction periodic structure 136. In some applications, the aperture may span at least 10 periods of the compound diffraction periodic structure 136 and have a diameter of at least 50 micrometers and / or less than 200 micrometers.

[0333] For some applications, beam-shaping optical element 40 (e.g.) Figure 3 (As shown) is a collimating lens 130 disposed between the laser diode 36 and the pattern generating optical element 38. (Referring to the above reference) Figure 19AIn the applications described in -B, 20A-E, and 21A-C, the collimating lens 130 can be positioned between the laser diode 36 and the segmented DOE 122. Figure 19A ), positioned between the laser diode 36 and the microlens array 132 ( Figure 20A ), and disposed between the laser diode 36 and the composite diffraction periodic structure 136 ( Figure 21A ).

[0334] Now for reference Figure 22A -B, Figure 22A -B is a schematic diagram illustrating a single optical element 138 and a structured light projector 22 including the optical element 138 for some applications according to the present invention. The single optical element 138 has an aspherical first side and a planar second side opposite to the first side. For some applications, the collimating lens 130 and the patterning optical element 38 can be fabricated as a single optical element 138, whose first aspherical side 140 collimates light emitted from the laser diode 36, and whose second planar side 142 generates a distribution 34 of discrete, unconnected light spots 33. The planar side 142 of the single optical element 138 can be shaped to define a DOE 39, a segmented DOE 122, a microlens array 132, or a compound diffraction periodic structure 136.

[0335] Now for reference Figure 23A -B, Figure 23A -B is a schematic diagram of an axial-cone lens 144 and a structured light projector 22 including the axial-cone lens 144 for some applications according to the present invention. An axial-cone lens is known to generate a Bessel beam, which is a beam focused within a desired depth range according to the input beam diameter and the axial-cone head angle. For some applications, the axial-cone lens 144, having a head angle γ (gamma) of at least 0.2 degrees and / or less than 2 degrees, is positioned between a collimating lens 130 and a pattern-generating optics element 38. When a laser diode 36 emits light through the axial-cone lens 144, the axial-cone lens 144 generates a focused Bessel beam 146. The focused Bessel beam 146 is split into a plurality of beams 148 by the pattern-generating optics element 38, each beam 148 being an exact copy of the Bessel beam 146 generated by the axial-cone lens 144. The pattern-generating optics element 38 may be a DOE 39, a microlens array 132, or a compound diffraction periodic structure 136.

[0336] Now for reference Figure 24A -B, Figure 24A-B is a schematic diagram illustrating an optical element 150 and a structured light projector 22 including the optical element 150 for some applications according to the invention. The optical element 150 has an aspherical surface 152 on a first side and a planar surface on a second side opposite to the first side. For some applications, a collimating lens 130 and an axonocone lens 144 can be fabricated as a single optical element 150. When the laser diode 36 emits light through the optical element 150, the aspherical surface 152 of the single optical element 150 directly generates a Bessel beam from the diverging beam. Then, as the light travels through a pattern-generating optical element 38, a distribution 34 of discrete, unconnected light spots 33 is generated, such that the discrete, unconnected light spots 33 have substantially uniform size at any orthogonal plane between 1 mm and 30 mm, for example, between 4 mm and 24 mm, from the pattern-generating optical element 38. The pattern-generating optical element 38 can be a DOE 39, a microlens array 132, or a compound diffraction periodic structure 136. As used throughout this application, and as included in the claims, a spot having a “substantially uniform size” means that the size variation of the spot does not exceed 40%.

[0337] Now for reference Figure 25 , Figure 25 This is a schematic diagram of a single optical element 154 in a structured light projector 22 according to some applications of the present invention. For some applications, the single optical element 154 can perform the functions of a collimating lens, an axonocone lens, and a pattern-generating optics. The single optical element 154 includes an aspherical surface 156 on a first side and a planar surface 158 on a second side opposite the first side. When the laser diode 36 emits a diverging beam through the single optical element 154, the aspherical surface 156 directly generates a Bessel beam from the diverging beam. The planar surface 158 is shaped to define a pattern-generating optics 38 and thus splits the Bessel beam into an array of discrete Bessel beams 160 to generate a distribution 34 of discrete, unconnected light spots 33, such that the discrete, unconnected light spots 33 have substantially uniform dimensions at any orthogonal plane between 1 mm and 30 mm, for example, between 4 mm and 24 mm, from the single patterned optics 154. The planar surface 158 can be shaped to define a DOE 39, a microlens array 132, or a compound diffraction periodic structure 136.

[0338] Now for reference Figure 26A -B, Figure 26A-B is a schematic diagram of a structured light projector 22 with more than one light source (e.g., laser diode 36) according to some applications of the invention. When using laser diodes, laser speckle can generate spatial noise. The speckle effect is the result of interference from many waves of the same frequency but different phases and amplitudes. When all the waves are superimposed, the composite wave is a wave whose amplitude varies randomly across the beam profile. For some applications, the speckle effect can be reduced by combining multiple laser diodes 36 of the same wavelength. Different lasers with the same wavelength are incoherent with each other, so combining them in the same space or the same diffraction beam splitter 162 will reduce the speckle by at least the square root of the number of different laser diodes 36.

[0339] Beam splitter 162 can be a standard 50 / 50 splitter that reduces the efficiency of the two beams to below 50%, or a polarization beam splitter (PBS) that maintains greater than 90% efficiency. For some applications, each laser diode 36 can have its own collimating lens 130, such as... Figure 26A As shown. Alternatively, multiple laser diodes 36 can share a collimating lens 130, which is positioned between the beam splitter 162 and the pattern generating optical element 38, as shown. Figure 26B As shown. The pattern generating optical element 38 can be a DOE 39, a segmented DOE 122, a microlens array 132, or a composite diffraction periodic structure 136.

[0340] As described above, the sparse distribution 34 improves capture by providing an improved balance between maintaining the amount of useful information and reducing the amount of projected light. For some applications, to provide a higher density pattern without reducing capture, multiple laser diodes 36 with different wavelengths can be combined. For example, each structured light projector 22 may include at least two, such as at least three, laser diodes 36 that emit light of different corresponding wavelengths. Although the projected light spots 33 may almost overlap in some cases, the color discrimination capability of a camera sensor can be used to distinguish the light spots of different colors in space. Optionally, red, blue, and green laser diodes can be used. All the structured light projector configurations described above can be implemented using multiple laser diodes 36 in each structured light projector 22.

[0341] Now for reference Figure 27A -B, Figure 27A -B is a schematic diagram illustrating different ways of combining laser diodes of different wavelengths according to some applications of the present invention. An optical fiber coupler 164 ( Figure 27A ) or laser combiner 166 ( Figure 27BTwo or more lasers of different wavelengths are combined into the same diffraction element. For laser combiner 166, the combining element can be a dichroic bidirectional or tri-dichroic combiner. Within each structured light projector 22, all laser diodes 36 emit light simultaneously or at different times through a common pattern generating optics 38. The individual laser beams can strike slightly different locations in the pattern generating optics 38 and generate different patterns. These patterns do not interfere with each other due to different colors, different pulse times, or different angles. The use of fiber optic coupler 164 or laser combiner 166 allows the laser diodes 36 to be positioned in a remote enclosure 168. The remote enclosure 168 can be positioned near the end of the handheld stick 20, allowing for a smaller probe 28.

[0342] For some applications, the structured light projector 22 and the camera 24 can be located in the proximal end 100 of the probe 28.

[0343] The following description primarily relates to the application of the present invention, including light field cameras.

[0344] Now for reference Figure 28A , Figure 28A This is a schematic diagram of an intraoral scanner 1020 according to some applications of the present invention. The intraoral scanner 1020 includes an elongated handheld rod 1022, with a probe 1028 at a distal end 1026 of the handheld rod 1022. The probe 1028 has a distal end 1027 and a proximal end 1024. As used throughout this application, and included in the claims, the proximal end of the handheld rod is defined as the end of the handheld rod closest to the user's hand when the user holds the handheld rod in a ready-to-use position, and the distal end of the handheld rod is defined as the end of the handheld rod furthest from the user's hand when the user holds the handheld rod in a ready-to-use position.

[0345] For some applications, a single structured light projector 1030 is disposed in the proximal end 1024 of the probe 1028, a single light field camera 1032 is disposed in the proximal end 1024 of the probe 1028, and a mirror 1034 is disposed in the distal end 1027 of the probe 1028. The structured light projector 1030 and the light field camera 1032 are positioned to face the mirror 1034, and the mirror 1034 is positioned to reflect light from the structured light projector 1030 directly onto the scanned object 1036 and reflect light from the scanned object 1036 into the light field camera 1032.

[0346] The structured light projector 1030 includes a light source 1040. In some applications, the structured light projector 1030 may have an illumination field ψ (psi) of at least 6 degrees and / or less than 30 degrees. In some applications, the structured light projector 1030 focuses light from the light source 1040 onto a projector focal plane 1038 at a distance of at least 30 mm and / or less than 140 mm from the light source 1040 (e.g., ...). Figure 29A (as shown in -B). The structured light projector 1030 may have a pattern generator 1042 disposed in the optical path between the light source 1040 and the projector focal plane 1038. When the light source 1040 is activated to emit light through the pattern generator 1042, the pattern generator 1042 generates a structured light pattern at the projector focal plane 1038.

[0347] The light field camera 1032 may have a field of view ω (omega) of at least 6 degrees and / or less than 30 degrees. The light field camera 1032 may be focused on a camera focal plane 1039 at a distance of at least 30 mm and / or less than 140 mm from the light field camera 1032 (e.g., ...). Figure 30 (As shown in the diagram). The light field camera 1032 has a light field camera sensor 1046, which includes an image sensor 1048 and a microlens array 1050 disposed in front of the image sensor 1048. The image sensor 1048 includes a pixel array, such as a CMOS image sensor. The microlens array 1050 is such that each microlens 1050 is disposed on a subarray 1052 of the sensor pixels. In addition, the light field camera 1032 has an objective lens 1054 disposed in front of the light field camera sensor 1048, which forms an image of the scanned object 1036 onto the light field camera sensor 1046.

[0348] The intraoral scanner 1020 may include control circuitry 1056, which (a) drives a structured light projector 1030 to project a structured light pattern onto an object 1036 outside the handheld stick 1022, and (b) drives a light field camera 1032 to capture a light field generated by the structured light pattern reflected from the object 1036. The structured light field contains information about the intensity and direction of the light rays from the structured light pattern reflected from the object 1036. The light field also contains information about phase-encoded depth, which allows estimation of scene depth from different directions. Using the information from the captured light field, a computer processor 1058 can reconstruct a three-dimensional image of the surface of the object 1036 and can output the image to an output device 1060, such as a monitor. Note that in Figure 28A , Figure 31 and Figure 32The computer processor 1058 is shown external to the handheld stick 1022 in an illustrative and non-limiting manner. For other applications, the computer processor 1058 may be located within the handheld stick 1022.

[0349] In some applications, the object being scanned 1036 is at least one tooth inside the subject's mouth. As mentioned above, dentists often coat the subject's teeth with an opaque powder to improve image capture when using a digital intraoral scanner. The light field camera 1032 in the intraoral scanner 1020 can capture the light field from a structured light pattern reflected from the teeth even in the absence of such powder, thus enabling a simpler digital intraoral scanning experience.

[0350] When the structured light projector 1030 and the light field camera 1032 are positioned in the proximal end 1024 of the probe 1028, the dimensions of the probe 1028 are limited by the placement angle of the mirror 1034. In some applications, the height H2 of the probe 1028 is less than 17 mm, and the width W1 of the probe 1028 is less than 22 mm. The height H2 and width W1 define a plane perpendicular to the longitudinal axis 1067 of the handheld rod 1022. Furthermore, the height H2 of the probe 1028 is measured from the lower surface 1070 (scanning surface) to the upper surface 1072 opposite to the lower surface 1070, through which reflected light from the scanned object 1036 enters the probe 1028. In some applications, the height H2 is between 14 and 17 mm. In some applications, the width W1 is between 18 and 22 mm.

[0351] Now for reference Figure 29A , Figure 29A This is a schematic diagram of a structured light projector 1030 with a laser diode 1041 as a light source 1040, according to some applications of the present invention. For some applications, the pattern generator 1042 may be a diffractive optical element (DOE) 1043. The laser diode 1041 may emit light through a collimator 1062, and then the collimated light is transmitted through the DOE 1043 to generate a structured light pattern as a distribution of discrete, unconnected light spots. As an alternative to the DOE 1043, the pattern generator 1042 may be a refractive microlens array disposed in the optical path (configuration not shown) between the laser diode 1041 and the projector focal plane.

[0352] Now for reference Figure 29B , Figure 29B This is a schematic diagram of a structured light projector 1030 having a light-emitting diode (LED) 1064 as a light source 1040 and a mask 1066 as a pattern generator 1042.

[0353] Now for reference Figure 30 , Figure 30This is a schematic diagram of a light field camera 1032 according to some applications of the present invention, showing a light field camera sensor 1046 and a captured three-dimensional object 1036. For some applications, the optical parameters of the light field camera 1032 can be selected such that (a) light reflected from the foreground 1075 of the object 1036 is focused onto the central region 1074 of the light field camera sensor, and (b) light reflected from the background 1077 of the object 1036 is focused onto the peripheral region 1076 of the light field camera sensor 1046. In some applications, when scanning intraoral scenes, the peripheral region 1076 can be pointed more frequently to more distant objects, such as gums, compared to closer objects, such as teeth.

[0354] The central region 1074 of the light field camera sensor 1046 can have a higher spatial resolution than the peripheral region 1076 of the light field camera sensor 1046. For example, each subarray 1052 in the central region 1074 of the image sensor 1048 can have 10-40% fewer pixels than each subarray 1052 in the peripheral region 1076; that is, the microlenses in the central region 1074 can be smaller than those in the peripheral region 1076. Smaller microlenses allow for more microlenses per unit area in the central region 1074. Therefore, due to the increased microlens ratio per unit area, the central region 1074 of the light field camera sensor 1046 can have a higher spatial resolution. In some applications, the central region 1074 may comprise at least 50% of the total number of sensor pixels.

[0355] Although the central region 1074 has a higher spatial resolution than the peripheral region 1076, the peripheral region 1076 can have a higher depth resolution than the central region 1074 and can be configured to focus at an object distance farther than the central region 1074. Larger microlenses in the peripheral region 1076 of the light field camera sensor 1046 are configured to focus at a greater depth than smaller microlenses in the central region 1074. For example, each microlens 1050 disposed on a subarray 1052 of sensor pixels in the peripheral region 1076 of the image sensor 1048 can be configured to focus at a depth 1.1-1.4 times greater than the depth at which each microlens 1050 disposed on a subarray 1052 of sensor pixels in the central region 1074 of the image sensor 1048 is configured to focus.

[0356] Therefore, the higher spatial resolution of the central region 1074 allows for capturing the foreground 1075 of the object 1036 at a higher spatial resolution than the background 1077 of the object 1036. For example, when scanning an intraoral scene of a subject, teeth can be captured at a higher spatial resolution than the area around the teeth. Meanwhile, the more distant focus and greater depth resolution of the peripheral region 1076 allows for capturing the background 1077, such as the edentulous area and gingiva around the teeth in the foreground 1075.

[0357] Now for reference Figure 31 , Figure 31 This is a schematic diagram of an intraoral scanner 1020 according to some applications of the invention, having a light field camera 1032 and a structured light projector 1030 disposed in the distal end 1027 of the probe 1028. For some applications, exactly one structured light projector 1030 and exactly one light field camera 1032 are disposed in the distal end 1027 of the probe 1028. The structured light projector 1030 can be positioned directly facing an object 1036 placed outside the handheld stick 1022 within its illumination field. Therefore, light projected from the structured light projector 1030 will fall on the object 1036 without any optical redirection, for example, by reflection from a mirror to redirect the light, as referenced above. Figure 28A Similarly, the light field camera 1032 can be positioned directly facing an object 1036 located outside the handheld stick 1022 within its field of view. Therefore, light reflected from the object 1036 will enter the light field camera 1032 without any optical redirection, such as reflection from a mirror to redirect the light, as described above. Figure 28A As stated above.

[0358] Positioning the structured light projector 1030 in the distal end 1027 of the probe 1028 allows for a wider illumination field ψ (psi) of the structured light projector 1030, for example, at least 60 degrees and / or less than 120 degrees. Positioning the structured light projector 1030 in the distal end 1027 of the probe 1028 also allows the structured light projector 1030 to focus light from the light source 1040 at a projector focal plane at a distance of at least 3 mm and / or less than 40 mm from the light source 1040.

[0359] Positioning the light field camera 1032 at the distal end 1027 of the probe 1028 allows for a wider field of view ω(omega) for the light field camera 1032, for example, at least 60 degrees and / or less than 120 degrees. Positioning the light field camera 1032 at the distal end 1027 of the probe 1028 also allows the light field camera 1032 to focus at a focal plane at a distance of at least 3 mm and / or less than 40 mm from the light source 1040. In some applications, the illumination field ψ(psi) of the structured light projector 1030 and the field of view ω(omega) of the light field camera 1032 overlap, such that at least 40% of the structured light pattern projected from the structured light projector 1030 is within the field of view ω(omega) of the light field camera 1032. Similar to the above reference. Figure 30 When the intraoral scanner 1020 has a single light field camera 1032 disposed in the distal end 1027 of the probe 1028, the optical parameters of the light field camera sensor 1046 can be selected so that the central region of the light field camera sensor 1090 has a higher resolution than the peripheral region of the light field camera sensor 1046.

[0360] Positioning the structured light projector 1030 and the light field camera 1032 in the distal end 1027 of the probe 1028 allows for a smaller probe 1028 because the mirror 1034 is not used in this configuration. In some applications, the height H3 of the probe 1028 is less than 14 mm, and the width W2 of the probe 1028 is less than 22 mm. The height H3 and width W2 define a plane perpendicular to the longitudinal axis 1067 of the handheld rod 1022. In some applications, the height H3 is between 10 and 14 mm. In some applications, the width W2 is between 18 and 22 mm. As described above, the height H2 of the probe 1028 is measured from (a) the lower surface 1070 (scanning surface) to (b) the upper surface 1072 opposite to the lower surface 1070, through which reflected light from the scanned object 1036 enters the probe 1028. The control circuit 1056 can (a) drive the structured light projector 1030 to project a structured light pattern onto an object 1036 outside the handheld stick 1022, and (b) drive the light field camera 1032 to capture the light field generated by the structured light pattern reflected from the object 1036. Using information from the captured light field, the computer processor 1058 can reconstruct a three-dimensional image of the surface of the object 1036 and output the image to an output device 1060, such as a monitor.

[0361] Now for reference Figure 32 , Figure 32This is a schematic diagram of an intraoral scanner 1020 having a plurality of structured light projectors 1030 and a plurality of light field cameras 1032 disposed in the distal end 1027 of a probe 1028, according to some applications of the invention. Having a plurality of structured light projectors and a plurality of light field cameras increases the overall field of view of the intraoral scanner 1020, which makes it possible to capture a plurality of objects 1036, for example, a plurality of teeth and the areas surrounding the teeth, such as edentulous areas in the subject's mouth. In some applications, a plurality of illumination fields ψ (psi) overlap with corresponding plurality of fields of view ω (omega), such that at least 40% of the structured light pattern projected from each structured light projector 1030 is within the field of view ω (omega) of at least one light field camera 1032. Control circuitry 1056 can (a) drive the plurality of structured light projectors 1030 to project structured light patterns onto the objects 1036 outside the handheld stick 1022, and (b) drive the plurality of light field cameras 1032 to capture the light fields generated by the plurality of structured light patterns reflected from the objects 1036. Using information from the captured light field, the computer processor 1058 can reconstruct a three-dimensional image of the surface of the object 1036 and output the image to an output device 1060, such as a monitor.

[0362] For some applications, at least one of the structured light projectors 1030 may be a monochromatic structured light projector that projects a monochromatic structured light pattern onto the object 1036 being scanned. For example, the monochromatic structured light projector may project a blue structured light pattern at a wavelength of 420-470 nm. At least one of the light field cameras 1032 may be a monochromatic light field camera that captures the light field generated by the monochromatic structured light pattern reflected from the object 1036 being scanned. The intraoral scanner 1020 may also include a light source that emits white light onto the object 1036 and a camera that captures a two-dimensional color image of the object 1036 under white light illumination. The computer processor 1058 may combine (a) the information captured from the monochromatic light field with (b) at least one two-dimensional color image of the object 1036 to reconstruct a three-dimensional image of the surface of the object 1036. The computer processor 1058 may then output the image to an output device 1060, such as a monitor.

[0363] Any of the above-described apparatuses can be used to perform a method for generating image data (e.g., image data of an intraoral surface). In one example embodiment, the method includes generating a corresponding light pattern by one or more light projectors disposed on a probe of an intraoral scanner. Generating a light pattern by one or more light projectors may include generating light by the light projectors, focusing the light on a focal plane of the projectors, and generating a light pattern from the light at the focal plane of the projectors by a pattern generator. The method may also include projecting the corresponding light pattern of one or more light projectors toward an intraoral surface disposed within an illumination field of one or more light projectors. The method may also include receiving a light field generated by at least a portion of the corresponding light pattern reflected from the intraoral surface by one or more light field cameras disposed on the probe. The method may further include generating multiple images depicting the light field by one or more light field cameras and sending the multiple images to a data processing system.

[0364] In some implementations, one or more light projectors and one or more light field cameras are disposed at the distal end of the probe, and the one or more light projectors and one or more light field cameras are positioned such that (a) each light projector faces directly toward the intraoral surface, (b) each light field camera faces directly toward the intraoral surface, and (c) at least 40% of the light pattern from each light projector is within the field of view of at least one light field camera.

[0365] In some embodiments, one or more light projectors and light field cameras are positioned near the probe. In such embodiments, the method may further include using a mirror to reflect a corresponding light pattern onto the intraoral surface, and using a mirror to reflect the light field reflected from the intraoral surface into one or more light field cameras.

[0366] In some applications of the invention, the method to generate a digital three-dimensional model of the intraoral surface can be performed by any of the described devices for intraoral scanning (e.g., an intraoral scanner and / or a data processing system such as a computer processor 1058). In one embodiment, the method includes driving one or more light projectors of the intraoral scanner to project a light pattern onto the intraoral surface. The method also includes driving one or more light field cameras of the intraoral scanner to capture multiple images depicting a light field generated by the projected light pattern reflected from at least a portion of the intraoral surface, wherein the light field contains information about the intensity of the light pattern reflected from the intraoral surface and the direction of the light rays. The method further includes receiving multiple images depicting at least a portion of the light pattern projected onto the intraoral surface and using information from the captured light field depicted in the multiple images to generate a digital three-dimensional model of the intraoral surface.

[0367] In one application, at least 40% of the light pattern from each light projector is within the field of view of at least one of one or more light field cameras. In one application, each light projector is a structured light projector having an illumination field of 60-120 degrees, and wherein the projector focal plane is between 3 mm and 40 mm from the light source. In one application, each light field camera has a field of view of 60-120 degrees and is configured to focus at a camera focal plane between 3 mm and 40 mm from the light field camera. In one application, the multiple images include images from multiple light field cameras. In one application, the light field also contains information about phase-encoded depth, through which depth can be estimated from different directions. In one application, the method further includes receiving multiple two-dimensional color images of the intraoral surface and determining color data of a digital three-dimensional model of the intraoral surface based on the multiple two-dimensional color images.

[0368] The applications of the invention described herein can take the form of a computer program product accessible from a computer-usable or computer-readable medium (e.g., a non-transitory computer-readable medium) that provides program code for use by or in connection with a computer or any instruction execution system (e.g., processor 96 or processor 1058). For the purposes of description, a computer-usable or computer-readable medium can be any means that can include, store, communicate, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The medium can be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system (or apparatus or device) or a propagation medium. In some applications, the computer-usable or computer-readable medium is a non-transitory computer-usable or computer-readable medium.

[0369] Examples of computer-readable media include semiconductor or solid-state memory, magnetic tape, removable computer disks, random access memory (RAM), read-only memory (ROM), rigid disks, and optical discs. Current examples of optical discs include read-only optical disc storage (CD-ROM), read / write optical discs (CD-R / W), and DVDs. For some applications, cloud storage and / or storage on remote servers are used.

[0370] A data processing system suitable for storing and / or executing program code will include at least one processor (e.g., processor 96 or processor 1058) directly or indirectly coupled to memory elements via a system bus. Memory elements may include local memory, mass storage, and cache memory used during the actual execution of the program code, the cache memory providing temporary storage for at least some of the program code to reduce the number of times code must be retrieved from mass storage during execution. The system can read the instructions of the present invention from the program storage device and follow those instructions to execute the application method of the present invention.

[0371] Network adapters can be coupled to a processor, enabling the processor to be coupled to other processors or remote printers or storage devices via an intermediate private or public network. Modems, cable modems, and Ethernet cards are just a small subset of the types of network adapters currently available.

[0372] The computer program code used to perform the operations of this invention can be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java, Smalltalk, and C++, and traditional procedural programming languages ​​such as C or similar programming languages.

[0373] It should be understood that the methods described herein can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to generate a machine, such that the instructions, which execute via the processor of the computer (e.g., processor 96 or processor 1058) or other programmable data processing apparatus, create means for implementing the functions / actions specified in the methods described herein. These computer program instructions can also be stored in a computer-readable medium (e.g., a non-transitory computer-readable medium) that can instruct the computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable medium generate an article of manufacture including instruction means that implement the functions / actions specified in the methods described herein. The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to generate a computer-implemented process, such that the instructions, which execute on the computer or other programmable apparatus, provide a process for implementing the functions / actions specified in the methods described herein.

[0374] Processors 96 and 1058 are typically hardware devices programmed with computer program instructions to generate a corresponding dedicated computer. For example, when programmed to perform the methods described herein, a computer processor is typically used as a dedicated three-dimensional surface reconstruction computer processor. Generally, the operations described herein performed by the computer processor transform the physical state of the memory, which is a real physical object, into having different magnetic polarities, charges, etc., depending on the technology of the memory used.

[0375] Alternatively, the processor 96 can take the form of a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), or a neural network implemented on a dedicated chip.

[0376] Those skilled in the art will understand that the present invention is not limited to what has been specifically shown and described above. Rather, the scope of the invention includes combinations and sub-combinations of the various features described above, as well as variations and modifications that would occur to those skilled in the art upon reading the foregoing description and not found in the prior art.

Claims

1. An apparatus for intraoral scanning, the apparatus comprising: A long, thin rod, including a probe located at the distal end of the long, thin rod; One or more light projectors, wherein each light projector includes at least one light source and a pattern generating optics element, and each light projector is configured to generate a light pattern by transmitting light from at least one light source through the pattern generating optics element, the light pattern comprising a uniformly distributed discrete unconnected dot or checkerboard pattern light pattern. Two or more cameras, wherein each of the two or more cameras is configured to capture multiple images of at least a portion of a light pattern projected onto an intraoral surface; and One or more processors are configured as follows: Receive multiple images from the two or more cameras depicting at least a portion of a light pattern projected onto the surface inside the mouth; Determine the correspondence between points in the light pattern and points in a plurality of images depicting at least a portion of the light pattern projected onto the intraoral surface; The three-dimensional position of the projected light pattern is identified based on the consensus among the two or more cameras that there is a correspondence between points in the light pattern and points in the plurality of images at the agreed three-dimensional position of the light pattern; and The identified three-dimensional location is used to generate a digital three-dimensional model of the intraoral surface.

2. The apparatus according to claim 1, wherein, The light pattern is defined by a plurality of projector rays, and wherein the one or more processors determine, through the following steps, a correspondence between points in the light pattern and points in a plurality of images depicting at least a portion of the light pattern projected onto the intraoral surface: Access calibration data that associates camera rays corresponding to pixels on the camera sensors of each of the two or more cameras with projector rays from the plurality of projector rays; and The intersection of the projector ray and the camera ray corresponding to at least a portion of the projected light pattern is determined using calibration data, wherein the intersection of the projector ray and the camera ray is associated with a three-dimensional point in space.

3. The apparatus according to claim 2, wherein, The one or more processors are also used for: The three-dimensional position of the projected light pattern is identified based on the existence of a light pattern projected by the projector light at certain intersections of the two or more cameras and the camera light corresponding to the pixels on the camera sensors.

4. The apparatus according to claim 2, wherein, The light pattern comprises a plurality of light spots, wherein each of the plurality of projector rays corresponds to a light spot among the plurality of light spots.

5. The apparatus according to claim 2, wherein, Each projector ray corresponds to a corresponding path of a pixel on the camera sensor of one of the two or more cameras, and wherein, in order to identify the three-dimensional position, the one or more processors run a corresponding algorithm: For each projector ray i, for each detected feature j on the camera sensor path corresponding to projector ray i, identify how many other cameras on their respective camera sensor paths corresponding to projector ray i detect the corresponding feature k of the light pattern corresponding to the corresponding camera ray, which intersects with projector ray i and the camera ray corresponding to the detected feature j, wherein projector ray i is identified as the specific projector ray that generates the detected feature j, for which the maximum number of other cameras detect the corresponding feature k; and The corresponding three-dimensional position on the inner surface of the mouth is calculated using the intersection point of the projector ray i with the corresponding camera ray corresponding to the detected feature j and the corresponding detected feature k.

6. The apparatus according to claim 5, wherein, Each detected feature j is a detected light spot, and each detected feature k is a detected light spot.

7. The apparatus according to claim 5, wherein, To identify three-dimensional positions, the one or more processors are also used for: We no longer consider the projector ray i, and the corresponding camera ray corresponding to the detected feature j and the corresponding detected feature k; and The corresponding algorithm is run again for the next projector ray i.

8. The apparatus according to claim 5, further comprising: Temperature sensor; The one or more processors are further configured to: Temperature data is received from a temperature sensor, wherein the temperature data indicates the temperature of at least one of the one or more light projectors or the two or more cameras; and Based on temperature data, selection is made among multiple sets of stored calibration data corresponding to multiple corresponding temperatures, each set of stored calibration data for the corresponding temperature indication (a) projector light corresponding to each projected feature of light from each of the one or more light projectors, and (b) camera light corresponding to each pixel on the camera sensor of each of the two or more cameras.

9. The apparatus according to claim 1, wherein, The light pattern includes non-coded structured light patterns.

10. The apparatus according to claim 1, wherein, The light pattern includes a first set of light spots having a first wavelength and a second set of light spots having a second wavelength, wherein the one or more processors are used to determine the correspondence using first calibration data of the first wavelength and second calibration data of the second wavelength.

11. The apparatus according to claim 1, further comprising: The target has multiple regions; in: The one or more light projectors have at least one area of ​​the target in their illumination field; Each of the two or more cameras has at least one area of ​​the target in its field of view; Multiple areas of the target are within the field of view of one of two or more cameras and within the illumination field of one of one or more light projectors; and The one or more processors are further configured to: Receive data from the two or more cameras indicating the position of the target relative to the light pattern; Determine the difference between the received data indicating the target's location and the stored calibrated location of the target; and In the identification of three-dimensional positions, the difference between the received data indicating the position of the target and the stored calibrated position of the target is taken into account.

12. The apparatus according to claim 1, wherein, One or more light projectors include multiple light projectors disposed in a probe at the distal end of the elongated rod, wherein the two or more cameras are disposed at the distal end of the elongated rod.

13. The apparatus according to claim 1, wherein, The one or more processors are further configured to: Drive each of the one or more light projectors to project a light pattern onto the intraoral surface; as well as Drive each of the two or more cameras to capture the plurality of images.

14. The apparatus according to claim 1, wherein, The one or more light projectors include a plurality of structured light projectors, wherein each of the plurality of structured light projectors is used to simultaneously project a distribution of corresponding discrete, unconnected light spots onto the intraoral surface.

15. The apparatus according to claim 1, wherein, The one or more light projectors include a plurality of structured light projectors, wherein each of the plurality of structured light projectors is used to project a corresponding discrete distribution of unconnected light spots onto the intraoral surface at different times.

16. The apparatus according to claim 1, wherein, The pattern-generating optical element includes a diffractive optical element or a refractive optical element.

17. The apparatus according to claim 1, wherein, The two or more cameras are configured to focus on an object focal plane, which is positioned between 1 mm and 30 mm away from the camera lens furthest from the camera sensor of the two or more cameras.

18. An apparatus for intraoral scanning, the apparatus comprising: A long, thin rod, including a probe located at the distal end of the long, thin rod; One or more light projectors, each light projector comprising: At least one light source is configured to produce light when activated; and A pattern generating optical element, wherein the pattern generating optical element is configured to generate a light pattern when light is transmitted through the pattern generating optical element, the light pattern comprising uniformly distributed discrete unconnected dots or a checkerboard pattern. Two or more cameras, each of the two or more cameras including a camera sensor and one or more lenses, wherein each of the two or more cameras is configured to capture multiple images depicting at least a portion of a light pattern projected onto an intraoral surface; and One or more processors are configured to: determine a correspondence between points in the light pattern and points in a plurality of images of at least a portion of the light pattern projected onto the inner surface of the mouth.

19. The apparatus according to claim 18, wherein, Each of the two or more cameras is configured to focus on an object focal plane, which is positioned between 1 mm and 30 mm away from the lens of the one or more lenses furthest from the camera sensor.

20. The apparatus according to claim 18, wherein, The one or more light projectors are disposed within the probe, and the two or more cameras are disposed within the probe.

21. The apparatus according to claim 18, wherein, The one or more light projectors and the two or more cameras are disposed at the distal end of the slender rod.

22. The apparatus according to claim 18, wherein, The one or more light projectors include at least two light projectors, and the two or more cameras include at least four cameras.

23. The apparatus according to claim 22, wherein, Most of the at least two light projectors and the at least four cameras are arranged in at least two rows, each row being generally parallel to the longitudinal axis of the probe, the at least two rows including at least a first row and a second row; The farthest camera and the nearest camera along the longitudinal axis of the at least four cameras are positioned such that, from a line of sight perpendicular to the longitudinal axis, their optical axes are at an angle of 90 degrees or less relative to each other. as well as The cameras in the first row and the cameras in the second row are positioned such that, from a line of sight coaxial with the vertical axis of the probe, the optical axis of the camera in the first row forms an angle of 90 degrees or less relative to the optical axis of the camera in the second row.

24. The apparatus according to claim 23, wherein: The remaining cameras, excluding the farthest and closest cameras, have optical axes substantially parallel to the longitudinal axis of the probe; and Each of the at least two rows includes an alternating sequence of light projectors and cameras.

25. The apparatus according to claim 23, wherein, The at least four cameras include at least five cameras, wherein the at least two light projectors include at least five light projectors, wherein the nearest-side component in the first row is a light projector, and wherein the nearest-side component in the second row is a camera.

26. The apparatus according to claim 23, wherein: The farthest camera along the longitudinal axis and the nearest camera along the longitudinal axis are positioned such that, from a line of sight perpendicular to the longitudinal axis, their optical axes are at an angle of 35 degrees or less relative to each other. as well as The cameras in the first row and the cameras in the second row are positioned such that, from a line of sight coaxial with the vertical axis of the probe, the optical axis of the camera in the first row forms an angle of 35 degrees or less relative to the optical axis of the camera in the second row.

27. The apparatus according to claim 18, wherein, The light pattern is defined by a plurality of projector rays, and the one or more processors are configured to determine, by means of the following steps, a correspondence between points in the light pattern and points in a plurality of images depicting at least a portion of the light pattern projected onto the intraoral surface: Access calibration data that associates camera rays corresponding to pixels on the camera sensors of each of the two or more cameras with projector rays of the plurality of projectors; The intersection of the projector ray and the camera ray corresponding to a portion of the projected light pattern is determined using calibration data, wherein the intersection of the projector ray and the camera ray is associated with a three-dimensional point in space. The one or more processors are further configured to: The three-dimensional position of the projected light pattern is identified based on the existence of a projector light pattern at certain intersection points agreed upon by the two or more cameras; and The identified three-dimensional location is used to generate a digital three-dimensional model of the intraoral surface.

28. The apparatus according to claim 18, wherein, The one or more structured light projectors are all configured to generate a discrete distribution of unconnected light spots at all planes between 1 mm and 30 mm from the pattern generating optics.

29. The apparatus according to claim 28, wherein, Each of the one or more structured light projectors has an illumination field of 45 to 120 degrees, and each of the two or more cameras has a field of view of 45 to 120 degrees.

30. The apparatus according to claim 18, wherein, The pattern-generating optical element is configured to generate the light pattern using at least one of diffraction or refraction.

31. The apparatus according to claim 18, wherein, The pattern-generating optical element has a luminous flux efficiency of at least 90%.

32. The apparatus of claim 18, further comprising: At least one uniform light projector is configured to project white light onto an intraoral surface, wherein at least one of the two or more cameras is configured to capture a two-dimensional color image of the intraoral surface using illumination from the uniform light projector.

33. The apparatus according to claim 18, wherein, The pattern generating optical element includes a diffractive optical element (DOE).

34. The apparatus according to claim 33, wherein, The DOE is divided into multiple sub-DOE sheets arranged in an array, wherein each sub-DOE sheet generates a corresponding discrete distribution of unconnected light points in different regions of the illumination field, such that when the light source is activated, a discrete distribution of unconnected light points is generated.

35. The apparatus according to claim 18, wherein, Each of the one or more projectors includes an additional optical element disposed between the light source and the pattern generating optical element, the additional optical element being configured to generate a Bessel beam from light transmitted through the additional optical element.

36. The apparatus according to claim 35, wherein, The additional optical element includes an axonoconical lens.

37. The apparatus according to claim 18, wherein, For each orthogonal plane in the illumination field of one or more light projectors, the ratio of the illuminated area to the unilluminated area is 1:150 to 1:16.

Images