WO2025202064A1

WO2025202064A1 - An intraoral scanning system with a tip housing configured to transmit infrared light

Info

Publication number: WO2025202064A1
Application number: PCT/EP2025/057815
Authority: WO
Inventors: Dylan Reynolds; Philip Grabow WESTERGAARD; Oliver Sundberg
Original assignee: 3Shape AS
Current assignee: 3Shape AS
Priority date: 2024-03-26
Filing date: 2025-03-21
Publication date: 2025-10-02
Anticipated expiration: 2026-09-26

Abstract

The present disclosure relates to an intraoral scanning system configured to determine a three-dimensional model of an oral cavity of a patient. The system includes a tip housing configured to be inserted at least partially into an oral cavity of a patient. The tip housing includes a scan window arranged at an aperture of the tip housing, and wherein the scan window includes an inner surface arranged within the tip housing, and an infrared light source configured to emit infrared light towards the oral cavity via the scan window. The system includes a visible light source configured to emit visible light towards the oral cavity via the scan window, an image sensor unit configured to capture reflection of the emitted visible light and/or the emitted infrared light from the dental arch, and one or more processors configured to determine the three-dimensional model based on the captured visible light and to determine infrared images based on the captured infrared light. The scan window includes a window coating on at least the inner surface, and wherein the window coating is configured to reduce reflections of the infrared light and reflections of the visible light from the inner surface.

Description

AN INTRAORAL SCANNING SYSTEM WITH A TIP HOUSING CONFIGURED

TO TRANSMIT INFRARED LIGHT

FIELD

The disclosure relates to an intraoral scanning system with a tip housing that is configured to transmit infrared light. More specifically, the tip housing includes one or more coatings that improves guiding of infrared light within the tip housing.

BACKGROUND

State of the art, ionizing radiation (e.g., X-rays) has been used to image the teeth for diagnostic purposes. For example, X-ray bitewing radiographs are often used to provide non-quantitative images of the teeth's internal structures. However, in addition to the risk of ionizing radiation, such images are typically limited in their ability to show early tooth mineralization changes (e.g. initial caries) resulting in underestimation of the demineralization depth; they are unable to assess the presence or not of micro-cavitation; they result in frequent overlap of the approximal tooth surfaces which requires repetition of radiograph acquisition and thus may involve a lengthy and expensive procedure.

Some intraoral features such as soft tissues and dental plaque are usually not visualized via X-ray because of their low density. Other techniques, such as cone beam computed tomography (CBCT) may provide tomographic images and be used to collect more information about the tissues and internal structure, but still require ionizing radiation.

It is known that near-infrared (NIR) light can be used for assessing internal structure of a tooth and tooth surface in the form of transillumination of teeth or light reflection and backscattering from teeth. The NIR range offers a non-ionizing and safe approach to assess dental caries, restorations, cracks, enamel and dentin defects.

For an intraoral scanning system to be inserted in an oral cavity of a patient, the intraoral scanning system may have a tip housing that is shaped in way which makes a scanning session comfortable for the patient. The purpose of the tip housing is to guide emitted light to the oral cavity and receive reflected light from the oral cavity. For the tip housing to be able to guide both visible light and infrared light there is a need for optimizing the optical components within the tip housing. Furthermore, to improve the intraoral scanning system to generate both infrared images and the visible images, there is a need to reduce stray light that is caused mainly by the infrared light.

SUMMARY

It is an aspect of the present disclosure to overcome the above needs for optimizing the tip housing for visible light and infrared light.

According to the aspect, an intraoral scanning system configured to determine a three- dimensional model of an oral cavity is disclosed. The oral cavity may be a mouth of a patient which includes teeth and soft tissue, such as gingival. The intraoral scanning system may be a system for scanning an oral cavity by an intraoral scanning device. The intraoral scanning device may be configured to communicate via a wired or wireless communication interface to an external server or an external computer. The system may comprises one or more processors that are arranged within the intraoral scanning device, the external server and/or the external computer. The intraoral scanner system may comprise a tip housing configured to be inserted at least partially into an oral cavity of a patient, and wherein the tip housing includes a scan window arranged at an aperture of the tip housing, and wherein the scan window includes an inner surface arranged within the tip housing, and an infrared light source configured to emit infrared light towards the oral cavity via the scan window. The tip housing may be detachable connected to a main housing of the intraoral scanning system. The tip housing may be detachable connected to a main housing of an intraoral scanning device. The tip housing is shaped differently than the main housing for the purpose of being inserted into an oral cavity of a patient. A cross-section area of the tip housing is less than a cross-section of the main housing.

The intraoral scanning system may include a visible light source configured to emit visible light towards the oral cavity via the scan window, and an image sensor unit configured to capture reflection of the emitted visible light and/or the emitted infrared light from the dental arch. During the scanning the user of the system may sweep the tip housing across surfaces of the oral cavity. The visible light may include one or more wavelengths within 350 nm and 750 nm, and the infrared light may include a wavelength withing 800 nm and 1100 nm. The visible light source may be configured to a UV light having a wavelength between 350 nm and 450 nm. The visible light source may include one or more light emitting diodes (LED), one for emitting white light and another for emitting UV light.

The system may include one or more processors configured to determine the three- dimensional model based on the captured visible light, such as white light, and infrared images based on the captured infrared light. The one or more processors may be configured to determine a composed image which includes a difference between visible image(s) and infrared image(s). The composed image includes enhanced contrast of internal structures of teeth in the oral cavity relative to the infrared image.

The scan window may include a window coating on at least the inner surface, and wherein the window coating may be configured to reduce reflections of the infrared light and reflections of the visible light from the inner surface. The window coating may be an antireflective coating. The thickness of the scan window may be half a wavelength or a quarter of a wavelength, and due to the thickness, the scan window may also be a circular-polarizer or a linear-polarizer. The window coating may include a plurality of thin film layers that includes Tantalum pentoxide and Silicium, and wherein the plurality of thin film layers includes at least 2 layers. The thickness of the scan window may be between 0.5 mm and 1.5 mm.

The tip housing may be protective by a hygiene barrier, such as a sleeve with another scan window. When the sleeve is applied on the tip housing, the another scan window and the scan window of the tip housing are aligned. The alignment may include a partially full overlap of the two scan windows. The another scan window may include an antireflective window coating. The antireflective window coating may include a plurality of thin film layers that includes Tantalum pentoxide and Silicium, and wherein the plurality of thin film layers includes at least 2 layers. The outer layer of the antireflective window coating of the another scan window may include a first material. The scan window of the tip housing includes an external surface, wherein the external surface is opposite to the internal surface of the scan window. Another window coating is applied on the external surface, and wherein the another window coating may be configured to reduce reflection of the infrared light and visible light. The another window coating applied on the external surface of the scan window has a second outer layer that includes a second material. The first material of the outer layer of the antireflective window coating is different from the second material for the purpose of maintaining the optimal antireflective profile of the antireflective coatings of the scan window and the another scan window.

The light sources of the intraoral scanning system, such as the visible light source and the infrared light source may be arranged within the tip housing.

The image sensor unit may include one or more cameras, wherein each of the one or more cameras includes an array of pixels. The image sensor unit may be arranged in the tip housing.

The visible light source may be arranged in a main housing of the system, such as an intraoral scanning device, and the images sensor unit may be arranged in the main housing.

The tip housing may include a tip mirror having a mirror surface, wherein the mirror surface is arranged with an angle of less than 90 degrees relative to the at least inner surface of the scan window. The mirror surface includes a mirror coating configured to increase reflections of the infrared light and reflections of the visible light from the mirror surface. The tip mirror may be arranged at a tip of the tip housing, wherein the tip mirror is configured to reflect visible light and the infrared light towards the scan window and the image sensor unit depending on a direction of the visible and infrared light. The tip housing may include an optical axis which extends along a longitudinal axis of the tip housing. The mirror surface of the tip mirror may have an acute angle relative to the optical axis.

The scan window may have a normal axis which may be orthogonal to the optical axis. The window coating may be configured to reduce the reflections of light having one or more wavelengths between 400 nm and 1100 nm, 400 nm and 950 nm, 350 nm and 950 nm or 350 nm and 1100 nm.

The mirror coating may be configured to increase the reflections of light having one or more wavelengths between 400 nm and 1100 nm, 400 nm and 950 nm, 350 nm and 950 nm or 350 nm and 1100 nm.

An example of an intraoral scanning system may include one or more scan units arranged along a longitudinal axis of the tip housing. The intraoral scanning system may comprise two scan units arranged in series along a longitudinal axis of the scanner in order to increase the field of view of the scanner. Having a larger field of view enables large smooth features, such as the overall curve of a given tooth, to appear in each image, which improves the accuracy of a subsequent stitching of respective 3D scan data, such as 3D surfaces, obtained from different sets of visible images. The one or more scan units may be arranged in combination with a reflecting element, such as a tip mirror, wherein the reflecting element is configured to alter the direction of light in the tip housing.

A scan unit of the one or more scan units may be understood herein as a unit comprising at least one projector unit, such as a visible light source, and an image sensor unit including a plurality of camera units. In some embodiments, each scan unit comprises at least two camera units having at least partly overlapping fields of view along different camera optical axes. Preferably, each scan unit comprises at least four camera units having at least partly overlapping fields of view along different camera optical axes. An advantage of having overlapping fields of view of the camera units is an improved accuracy due to reduced amount of image stitching errors.

The at least one projector unit and the plurality of camera units of the scan unit may be provided as modular units for being inserted into a fixation unit of the scan unit and then arranged in the tip housing. Each unit, camera unit or projector unit, may be connected to its own flexible printed circuit board (PCB). The projector unit and camera units may be fixedly mounted inside the fixation unit, e.g. using an adhesive.

The each of the one or more scan units may further be considered as a modular unit in the sense that it provides a complete optical system with projector unit and a plurality of camera units. In some embodiments, the scanner is adapted for receiving several of such scan units, such that the field of view of the scanner may be extended or enlarged.

In this example a visible light source configured to emit UV light and an infrared light source may be arranged in the tip housing but separate from the one or more scan units. In one example, the visible light source for emitting UV light and the infrared light source may be arranged such that the emitted light is directed towards the scan window with no need of the tip mirror, i.e. the reflecting element. In such configuration, the two light sources are arranged in vicinity to an upper inner surface of the tip housing which is opposite to a bottom inner surface in which the scan window is arranged.

An example of an intraoral scanning system may include an image sensor unit and a visible light source. The depth information in the 3D model is determined by triangulation between a point in the oral cavity, the visible light source and the image sensor unit. In this example, the image sensor unit and the visible light source are arranged in a main housing of an intraoral scanning device of the system, and an infrared light source is arranged in the tip housing of the intraoral scanning device. The tip housing may be connectable to the main housing of the intraoral scanning device. In another example, the intraoral scanning device may be a focus scanner, where a focus lens is moving along an optical axis of the intraoral scanning device for the purpose of changing the focus of the image sensor unit. The visible light source and the image sensor unit may share the same optical axis via a beamsplitter. The beamsplitter is configured to transmit the emitted light in one direction, and the reflected light to be captured by the image sensor unit is directed by the beamsplitter in another direction. In this example, the focus lens, the image sensor unit and the visible light source are arranged within a main housing of the intraoral scanning device, and the infrared light source is arranged within the tip housing. In yet another example of the intraoral scanning system, the infrared light source, the visible light source and the image sensor unit are all arranged in the tip housing of an intraoral scanning device. The tip housing may be connectable to a main housing of the intraoral scanning device. The tip housing may include a facing probe that is facing towards the scan window of the tip housing. The infrared light source, the visible light source and the image sensor unit are all mounted on a surface of the facing probe that is directed towards the scan window. In this example, the light that transfer through the scan window is received directly by the image sensor unit or emitted directly by the light sources through the scan window. In this example, there are no needs for a tip mirror to redirect the light inside the tip housing. The facing probe may include a plurality of infrared light sources configured to emit infrared light towards the oral cavity via the scan window, a plurality of visible light sources configured to emit visible light towards the oral cavity via the scan window, and a plurality of image sensor units configured to capture reflection of the emitted visible light and/or the emitted infrared light from the dental arch.

The scan window may be arranged within an aperture of the tip housing, or, the scan window may be aligned to an aperture of the tip housing but mounted to an inner surface of the tip housing. The scan window may include a substrate that is made of a polymer, such as poly(methyl methacrylate) (PMMA), or it may be made of a glass, such as sapphire glass, borosilicate-crown glass etc. On the glass or polymer, the window coating is applied.

The inner surfaces of the tip housing may contribute to stray light of the visible light and infrared light, and therefore, it would of benefit to cover the inner surfaces with a material that is configured to reduce the reflections of the infrared light and the visible light. The material may be coated onto the inner surfaces. The infrared light source may be arranged within the tip housing on an upper inner surface opposite to a bottom inner surface where the scan window is arranged. In this example, if would be of benefit to cover all inner surfaces of the tip housing which the infrared light has the highest intensity. These inner surfaces define an infrared area, and this infrared area stretch from the tip and at least 5 cm along the longitudinal axis of the tip housing in a direction away from the tip.

To reduce the amount of coating to be applied, it would be of benefit to apply a coating of a material that is configured to reduce the reflections of the infrared light and the visible light of the inner surfaces at the aperture and an area around the aperture of at least 1 mm in width. The scan window may have a first end that is arranged in vicinity to the tip of the tip housing and a second end that is opposite to the first end. The area around the aperture to be covered by the coating may be non-symmetrical as the area of material may be at least 5 mm wide at the second end of the scan window, and at the first end the area of material may be between 0.5 mm and 2 mm.

The tip housing may include electronics that reflects infrared light. For example, the tip housing may include flexible circuit with at least a copper layer. The flexible circuit may be partly arranged in vicinity to the scan window, and wherein the flexible circuit arranged in vicinity to the aperture is covered by a material that is configured to reduce the reflections of the infrared light. The flexible circuit may include a heating unit that includes at least two heating parts that are arranged on both sides of the scan window. The two heating parts that irradiates the heat for defogging the scan window is not covered by any material for reducing reflections, however, the part of the heating unit that supplies an electrical power to the two heating parts are covered by the material. A temperature sensor may be arranged in vicinity to the scan window, and the temperature sensor is configured to measure a temperature which the one or more processors is configured to use for controlling the electrical power. The temperature sensor is not covered by the material. The material may be a sticker, such as an optical adhesive layer, wherein a reflective layer and an adhesive layer are arranged in a stacked configuration.

The tip housing may include a heating unit that may be arranged partly around the scan window, and wherein the heating unit may be configured to apply a heat to the scan window upon receiving an electrical power. The heat defogs the scan window during a scanning scenario. The scan window may be even more complexed. Beside being a polarizer and antireflective, the scan window may also include a transparent conductive layer that is configured to apply a heat uniformly across the inner surface of the scan window upon receiving an electrical power.

The window coating may be a transparent conductive layer, and wherein the transparent conductive layer may be configured to reduce reflection of the infrared light and reflection of the visible light from the inner surface. When the transparent conductive layer receives an electrical effect, it generates heat, thereby transferring the heat to the scanning window.

The transparent conductive layer may be further coated with a dielectric insulating layer, thereby protecting the transparent conductive layer. A dielectric insulating layer may be deposited over the transparent conductive layer acting as a protective coating to prevent the transparent conductive layer from wearing off or being damaged during use. The protective function of the dielectric insulation layer can be helpful because the transparent conductive layer can be very thin and can be easily damaged. In addition to a protective function, the dielectric insulating layer can provide an insulating function, thus preventing the conductive layer from making electrical shorts with surrounding conductive objects. The dielectric insulating layer may further be used for optical index matching the conductive layer to the surrounding ambient environment, e.g., air, body cavity, etc. In addition, a plurality of dielectric insulation layers may be coated on the transparent conductive layer for the purpose of creating an anti-reflective coating.

The antireflective coating may be optimized to the transparent conductive layer and applied to an outer surface of the transparent conductive layer. In one example, the inner surface of the scan window may include both the transparent conductive layer and an antireflective coating, and the external surface that is opposite to the inner surface, may be coated with an antireflective coating only. The antireflective coatings may be optimized for transmitting the infrared light and the visible light with a 95 % efficiency. The window coating may be configured to transmit at least 70%, 80%, 90% or 95 % of the infrared light and the visible light. The window coating may include both the antireflective coating and the transparent conductive layer.

The scan window may include an infrared and visible coating adapted to transmit both visible light and infrared light, and the infrared coating is extending in front of the scan window in such manner as to face the tip mirror.

The design of a single antireflective coating that is configured to transmit light with wavelengths between 350 nm and 1100 nm would result in a very complex thin film layer structure which will be costly to manufacture and also difficult to manufacture with a transmission of above 95 % across the whole spectrum. Instead of making a single antireflective coating, then the surface of the scan window may be partly coated with an infrared coating and a visible coating. The infrared coating may be adapted to transmit infrared light with an efficiency of more than 95 %. Furthermore, the visible coating may be adapted to transmit infrared light with an efficiency of more than 95 %. Between 50% and 75 % of the scan window may be coated with the visible coating, and between 15 % and 50% of the scan window may be coated with the infrared coating. For example, the tip housing may include the infrared light source that is arranged such that the light is penetrating through the scan window with the infrared coating. The emitted white light may be guided to penetrate through the scan window with the visible coating. The intraoral scanner system may include at least two image sensor units which includes a first image sensor unit configured to receive visible light (incl. UV light), and a second image sensor unit configured to receive infrared light. The first image sensor unit is arranged such that the visible light that is transmitted from the dental object and through the visible coating would be received. The second image sensor unit is arranged such that the infrared light that is transmitted from the dental object and through the infrared coating would be received. The two image sensor units may be arranged in vicinity to the scan window. By separating the window coating into two separate coatings, one for the infrared light and another one for the visible light, would make the window coating even more tolerant for variation in the angle of incidence of the light. The tip mirror may include a mirror coating that is configured to reflect at least 95 % of the infrared light and the visible light. The mirror coating would also benefit from reducing the amount of thin film layers by coating a first part of the mirror surface of the tip mirror with a visible coating configured to reflect with at least 95% of visible light, and by coating a second part of the mirror surface of the tip mirror with an infrared coating configured to reflect with at least 95 % of the infrared light. The benefit is that the mirror coating becomes more tolerant for variations in the angle of incidence of the light.

The mirror coating may include a plurality of thin film layers that includes Titanium dioxide and Silicium, and wherein the plurality of thin film layers includes at least 50 layers. The mirror coating is configured to reflect at least 95 % of light within 350 nm to 750 nm and at least 800nm to at least 1100 nm.

The window coating may include a plurality of thin film layers that includes Tantalum pentoxide and Silicium, and wherein the plurality of thin film layers includes at least 4 layers.

BRIEF DESCRIPTION OF THE FIGURES

Aspects of the disclosure may be best understood from the following detailed description taken in conjunction with the accompanying figures. The figures are schematic and simplified for clarity, and they just show details to improve the understanding of the claims, while other details are left out. Throughout, the same reference numerals are used for identical or corresponding parts. The individual features of each aspect may each be combined with any or all features of the other aspects. These and other aspects, features and/or technical effect will be apparent from and elucidated with reference to the illustrations described hereinafter in which:

FIGS. 1 A to ID illustrate different examples of an intraoral scanning system; FIGS. 2A to 2C illustrate different examples of a scan window in a tip housing; FIGS. 3 A and 3B illustrate different examples on providing electrical connection to a transparent conductive layer;

FIGS. 4A to 4C illustrate different examples of a tip housing; FIGS. 5A to 5C illustrate different examples of a scan window;

FIGS. 6A and 6B illustrate different examples of the tip housing;

FIGS. 7A to 7C illustrate different examples of the tip housing;

FIGS. 8 A and 8B illustrate different examples of the tip housing; and FIG. 9 illustrates an example of the intraoral scanning system.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. Several aspects of the devices, systems, mediums, programs and methods are described by various blocks, functional units, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as “elements”). Depending upon particular application, design constraints or other reasons, these elements may be implemented using electronic hardware, computer program, or any combination thereof.

The electronic hardware may include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. Computer program shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

A scanning for providing intra-oral scan data may be performed by a dental scanning system that may include an intraoral scanning device such as the TRIOS series scanners from 3 Shape A/S. The dental scanning system may include a wireless capability as provided by a wireless network unit. The scanning device may employ a scanning principle such as triangulation-based scanning, confocal scanning, focus scanning, ultrasound scanning, x-ray scanning, stereo vision, structure from motion, optical coherent tomography OCT, or any other scanning principle. In an embodiment, the scanning device is capable of obtaining surface information operated by projecting a pattern and translating a focus plane along an optical axis of the scanning device and capturing a plurality of 2D images at different focus plane positions such that the series of captured 2D images corresponding to each focus plane forms a stack of 2D images. The acquired 2D images are also referred to herein as raw 2D images, wherein raw in this context means that the images have not been subject to image processing. The focus plane position is preferably shifted along the optical axis of the scanning system, such that 2D images captured at a number of focus plane positions along the optical axis form said stack of 2D images (also referred to herein as a sub-scan) for a given view of the object, i.e. for a given arrangement of the scanning system relative to the object. After moving the scanning device relative to the object or imaging the object at a different view, a new stack of 2D images for that view may be captured. The focus plane position may be varied by means of at least one focus element, e.g., a moving focus lens. The scanning device is generally moved and angled relative to the dentition during a scanning session, such that at least some sets of sub-scans overlap at least partially, in order to enable reconstruction of the digital dental 3D model by stitching overlapping 3D subscans together in real-time and display the progress of the virtual 3D model on a display as feedback to the user. The result of stitching is the digital 3D representation of a surface larger than that which can be captured by a single sub-scan, i.e. which is larger than the field of view of the 3D scanning device. Stitching, also known as registration and fusion, works by identifying overlapping regions of 3D surface in various sub-scans and transforming sub-scans to a common coordinate system such that the overlapping regions match, finally yielding the digital 3D model. An Iterative Closest Point (ICP) algorithm may be used for this purpose. Another example of a scanning device is a triangulation scanner, where a time varying pattern is projected onto the dental arch and a sequence of images of the different pattern configurations are acquired by one or more cameras located at an angle relative to the projector unit. Color texture of the dental arch may be acquired by illuminating the object using different monochromatic colors such as individual red, green and blue colors or by illuminating the object using multi chromatic light such as white light. A 2D image may be acquired during a flash of white light or other colors/wavelengths.

Generally, the process of obtaining surface information in real time of a dental arch to be scanned requires the scanning device to illuminate the surface and acquire high number of 2D images. Typically, a high speed camera is used with a framerate of 300-2500 2D frames pr second dependent on the technology and 2D image resolution. The high amount of image data needed to be handled by the scanning device to either directly forward the raw image data stream to an external processing device or performing some image processing before transmitting the data to an external device or display. This process requires that multiple electronic components inside the scanner is operating with a high workload thus requiring a high demand of current.

The scanning device comprises one or more light projectors configured to generate an illumination pattern to be projected on a three-dimensional dental arch during a scanning session. The light projector(s) preferably comprises a light source, a mask having a spatial pattern, and one or more lenses such as collimation lenses or projection lenses. The light source may be configured to generate light of a single wavelength or a combination of wavelengths (mono- or polychromatic). The combination of wavelengths may be produced by using a light source configured to produce light (such as white light) comprising different wavelengths. Alternatively, the light projector(s) may comprise multiple light sources such as LEDs individually producing light of different wavelengths (such as red, green, and blue) that may be combined to form light comprising the different wavelengths. Thus, the light produced by the light source may be defined by a wavelength defining a specific color, or a range of different wavelengths defining a combination of colors such as white light. In an embodiment, the scanning device comprises a light source configured for exciting fluorescent material of the teeth to obtain fluorescence data from the dental arch. Such a light source may be configured to produce a narrow range of wavelengths. In another embodiment, the light from the light source is infrared (IR) light, which is capable of penetrating dental tissue. The light projector(s) may be DLP projectors using a micro mirror array for generating a time varying pattern, or a diffractive optical element (DOF), or back-lit mask projectors, wherein the light source is placed behind a mask having a spatial pattern, whereby the light projected on the surface of the dental arch is patterned. The back-lit mask projector may comprise a collimation lens for collimating the light from the light source, said collimation lens being placed between the light source and the mask. The mask may have a checkerboard pattern, such that the generated illumination pattern is a checkerboard pattern. Alternatively, the mask may feature other patterns such as lines or dots, etc.

The scanning device preferably further comprises optical components for directing the light from the light source to the surface of the dental arch. The specific arrangement of the optical components depends on whether the scanning device is a focus scanning apparatus, a scanning device using triangulation, or any other type of scanning device. A focus scanning apparatus is further described in EP 2 442 720 Bl by the same applicant, which is incorporated herein in its entirety.

The light reflected from the dental arch in response to the illumination of the dental arch is directed, using optical components of the scanning device, towards the image sensor(s). The image sensor(s) are configured to generate a plurality of images based on the incoming light received from the illuminated dental arch. The image sensor unit may be a high-speed image sensor such as an image sensor configured for acquiring images with exposures of less than 1/1000 second or frame rates in excess of 250 frames pr. second (fps). As an example, the image sensor may be a rolling shutter (CCD) or global shutter sensor (CMOS). The image sensor(s) may be a monochrome sensor including a color filter array such as a Bayer filter and/or additional filters that may be configured to substantially remove one or more color components from the reflected light and retain only the other non-removed components prior to conversion of the reflected light into an electrical signal. For example, such additional filters may be used to remove a certain part of a white light spectrum, such as a blue component, and retain only red and green components from a signal generated in response to exciting fluorescent material of the teeth. The network unit may be configured to connect the dental scanning system to a network comprising a plurality of network elements including at least one network element configured to receive the processed data. The network unit may include a wireless network unit or a wired network unit. The wireless network unit is configured to wirelessly connect the dental scanning system to the network comprising the plurality of network elements including the at least one network element configured to receive the processed data. The wired network unit is configured to establish a wired connection between the dental scanning system and the network comprising the plurality of network elements including the at least one network element configured to receive the processed data.

The dental scanning system preferably further comprises a processor configured to generate scan data (such as extra-oral scan data and/or intra-oral scan data) by processing the two-dimensional (2D) images acquired by the scanning device. The processor may be part of the scanning device. As an example, the processor may comprise a Field- programmable gate array (FPGA) and/or an Advanced RISC Machines (ARM) processor located on the scanning device. The scan data comprises information relating to the three- dimensional dental arch. The scan data may comprise any of 2D images, 3D point clouds, depth data, texture data, intensity data, color data, and/or combinations thereof. As an example, the scan data may comprise one or more point clouds, wherein each point cloud comprises a set of 3D points describing the three-dimensional dental arch. As another example, the scan data may comprise images, each image comprising image data e.g. described by image coordinates and a timestamp (x, y, t), wherein depth information can be inferred from the timestamp. The image sensor(s) of the scanning device may acquire a plurality of raw 2D images of the dental arch in response to illuminating said object using the one or more light projectors. The plurality of raw 2D images may also be referred to herein as a stack of 2D images. The 2D images may subsequently be provided as input to the processor, which processes the 2D images to generate scan data. The processing of the 2D images may comprise the step of determining which part of each of the 2D images are in focus in order to deduce/generate depth information from the images. The internal depth information may be used to generate 3D point clouds comprising a set of 3D points in space, e.g., described by cartesian coordinates (x, y, z). The 3D point clouds may be generated by the processor or by another processing unit. Each 2D/3D point may furthermore comprise a timestamp that indicates when the 2D/3D point was recorded, i.e., from which image in the stack of 2D images the point originates. The timestamp is correlated with the z-coordinate of the 3D points, i.e., the z-coordinate may be inferred from the timestamp. Accordingly, the output of the processor is the scan data, and the scan data may comprise image data and/or depth data, e.g. described by image coordinates and a timestamp (x, y, t) or alternatively described as (x, y, z). The scanning device may be configured to transmit other types of data in addition to the scan data. Examples of data include 3D information, texture information such as infra-red (IR) images, fluorescence images, reflectance color images, x-ray images, and/or combinations thereof.

FIGs. 1A to ID illustrate different examples of an intraoral scanning system 1. In these examples the intraoral scanning system 1 includes an intraoral scanning device with a tip housing 2 and a main housing 4. The tip housing 2 is configured to be inserted into a mouth of a patient to be scanned, and the main housing 4 is configured to be handled by a user’s hand. The intraoral scanning system 1 is configured to determine a three- dimensional model of an oral cavity of a patient. The tip housing includes a scan window 9 arranged at an aperture of the tip housing 2, and wherein the scan window 9 includes an inner surface 9A arranged within the tip housing 2, and an infrared light source 3 configured to emit infrared light towards the oral cavity via the scan window 9. The system 1 further comprises a visible light source 7 configured to emit visible light and/or a UV light source configured to emit UV light towards the oral cavity via the scan window 9, an image sensor unit 5 configured to capture reflection of the emitted visible light and/or the emitted infrared light from the dental arch, and one or more processors 100 configured to determine the three-dimensional model based on the captured visible light and to determine infrared images based on the captured infrared light. In these examples at least one of the one or more processors 100 is arranged within the intraoral scanning system 1. In all examples illustrated by FIGs. 1A to ID, at least the tip housing 2 is covered by a hygienic sleeve 6 that is detachable connected to at least the tip housing 2. The hygienic sleeve 6 includes a second scan window 11 that is aligned with the scan window 9 when the hygienic sleeve 6 is applied to the tip housing 2. The hygienic sleeve may include a second scan window that includes a window coating on both surfaces of the second scan window.

In FIG. 9, the one or more processors 100 are arranged within the intraoral scanning system 1, and external computers (202, 204, 206), such as a server and an external laptop or an external desktop computer. Part of processing may be performed within the processor in the intraoral scanning system 1 and/or another part of processing may be performed within the external computers 100. The scan window (9, not shown) includes a window coating (20, not shown) on at least the inner surface 9A, and wherein the window coating 20 is configured to reduce reflections of the infrared light and reflections of the visible light from the inner surface 9A. The scan window 9 includes an external surface 9B which is opposite to the inner surface 9A. The external surface 9B may also be covered by a window coating that is similar to the window coating on the inner surface 9A.

In Fig. 1 A, the visible light source and the image sensor unit are arranged in the main housing 4 along with a prism 103 or a cube 103 that consists of two prisms put together. The prism or cube 103 is configured to reflect light from the dental arch and transmit the emitted light. In this example, an optical axis 102 along a longitudinal axis of the intraoral scanning system 1 is shared by the visible light source 7 and the image sensor unit 5. In this system 1, a tip mirror 10 is applied to an angled inner surface of the tip housing 2, and wherein an angle of less than 90 degrees is formed between the tip mirror 10 and the scan window 9. In some examples, the angle may be 90 degrees. The tip mirror 10 is configured to reflect the emitted light (3, 7) towards the scan window 9. Furthermore, the tip mirror 10 is configured to reflect the light from the oral cavity towards the image sensor unit 5. The scan window 9 is arranged in vicinity to a bottom end of the tip mirror 10, and the infrared light source is arranged in vicinity to an upper end of the tip mirror 10. Most of the emitted infrared light is directly transmitted to the scan window 9, and some of the emitted infrared light is transmitted to the scan window 9 via the tip mirror 10. The tip mirror 10 has a mirror surface that is configured to reflect infrared light and visible light. The mirror surface includes a mirror coating configured to increase reflection of the infrared light and the visible light. The mirror surface has an angle of less than 90 degrees relative to the at least inner surface 9A of the scan window 9. In the example illustrated in FIG. 1 A, a single infrared light source 3 is seen. In another example, the tip housing 2 may include a plurality of infrared light sources.

FIG. IB illustrates another example of the intraoral scanning system 1 wherein the visible light source 7 and the image sensor unit 5 are mounted in a scan unit 110 that is arranged within the tip housing. The scan unit 110 includes a plurality of camera units (5A,5B) having at least partly overlapping fields of view along different camera optical axes. The different camera optical axes are directed along the longitudinal axes 102 and so is the field of view of the visible light source 7. The tip mirror 10 directs the emitted light from the visible light source 7 towards the scan window 9, and wherein the tip mirror 10 further directs the reflected visible light and reflected infrared light towards the plurality of camera units (5A,5B). The infrared light source 3 is arranged on an opposite inner surface relative to the inner surface in/on which the scan window 9 is arranged. In this example, the plurality of camera units (5A,5B) are arranged around the visible light source 7 in a symmetrical manner. In yet another example, the scan unit 110 includes a plurality of camera units including at least four camera units with overlapping field-of-view.

FIG. 1C illustrates yet another on the intraoral scanning system 1. In this example, the tip housing 2 includes two scan units (110 A, 100B), wherein each of the scan units (110A,l 10B) is paired with a tip mirror (10A,10B). Furthermore, the tip housing includes two infrared light sources 3 each assigned to one of the two tip mirrors (10A,10B). In another example, the system 1 includes one infrared light source 3 arranged in the tip housing 2. In this example, the scan window 9 is extended along the optical axis 102 so to cover both field-of-views of the scan units (110A,l 10B). In another example, the system 1 includes two scan windows including a first and a second scan window, wherein the first scan window is aligned to a first scan unit 110A and the second scan window is aligned to a second scan unit HOB. The two scan windows are arranged in respective apertures in the tip housing 2. In the example illustrated in FIG. 1C, the window coating is the same across the whole inner surface 9A and/or the external surface 9B. In the example where the scan window 9 is divided into two scan windows one for each scan units (110A, HOB), the window coating on the scan windows are the same, however, the example where the system 1 includes one infrared light source 3, assigned to a part of the scan window 9 or to one of the scan windows if divided into two scan windows, the window coating may not be the same across the whole scan window 9 or for both scan windows. The first scan window is aligned to the first scan unit 110A and the infrared light source 3, and the second scan window is aligned to the second scan unit HOB and not the infrared light 3, and in this example, the first scan window includes a window coating that is an antireflective coating optimized to transmit light from 350 nm to 1100 nm. The window coating for the second scan window is an antireflective coating optimized to transmit light from 350 nm to 800 nm. The purpose of having different window coatings is for minimizing cost for producing the window coatings, and, to reduce the sensitivity to variations in the angle of incidence of the light on the surfaces of the scan window 9 with the simpler window coating.

In the examples illustrated in FIGS. 1 A to 1C includes an infrared light source 3 that is arranged on a sub-flexible printed circuit board which extends away from a main flexible printed circuit that are arranged along the bottom surface of the tip housing 2. The subflexible printed circuit board extends away from the main flexible printed circuit and along an inner surface of the tip housing 2 to the upper surface of the tip housing. The main flexible printed circuit provides power to the infrared light source via the sub-flexible printed circuit board and to a heating unit (not shown) arranged in the tip housing 2. The heating unit provides heat to the scan window 9 for the purpose of avoiding fog to be generated on the scan window during scanning of a patient.

FIG. ID illustrates yet another example of the intraoral scanning system 1 which does not include a tip mirror 10. In this example, the tip housing 2 includes a facing probe 115 that is facing towards the scan window 9 of the tip housing 2. The infrared light source 3, the visible light source 7 and the image sensor unit 5 are all mounted on a surface of the facing probe 115 that is directed towards the scan window 9. In this example, the light that transfer through the scan window 9 is received directly by the image sensor unit 5 or emitted directly by the light sources (3,7) through the scan window 9. The facing probe may include a plurality of infrared light sources (3A,3B) configured to emit infrared light towards the oral cavity via the scan window 9, a plurality of visible light sources (7A,7B) configured to emit visible light towards the oral cavity via the scan window 9, and a plurality of image sensor units (5A,5B) configured to capture reflection of the emitted visible light and/or the emitted infrared light from the dental arch.

FIGS. 2A to 2C illustrate different examples of the scan window 9 in a tip housing 2. In these examples, there are no tip mirrors inside the tip housing 2 and an infrared light source. In other examples of the tip housing illustrated in FIGS. 2A to 2C, the tip housing 2 is similar to the tip housing 2 illustrated in FIGS. 1 A to ID. The scan window may include a substrate that is made of a polymer, such as poly(methyl methacrylate) (PMMA), or of a glass, such as sapphire glass, borosilicate-crown glass etc. On the substrate the window coating 20 is applied. The polarization of the light transferring through the scan window is determined by the thickness of the substrateand/or a coating applied to a substrate, and the material composition of thin film layers in the window coating 20 includes tantalum pentoxide and Silicium. In another example, the scan window may be a regular substrate without being a waveplate. The thickness of at least the outermost layer of the window coating 20 is adapted to air or to an outer layer of a window coating of the another scan window 11 arranged in the sleeve 6. In FIG. 2A, the inner surface 9A of the scan window 9 is coated with the window coating 20A, and wherein the thickness of at least the outermost layer of the window coating 20A is adapted to air. In FIG. 2B, both the inner and external surface (9 A, 9B) are coated with a window coating (20A,20B), wherein the thickness of at least the two outermost layers of the window coating 20B are adapted to air or to an outer layer of a window coating of the another scan window 11 arranged in the sleeve 6. In FIG. 2C, the inner surface 9A of the scan window 9 includes multiple coatings 20A, a coating that is a transparent conductive layer that is configured to generate heat onto the scan window 9 upon receiving electrical power, and a coating that is an antireflective coating adapted to improve the efficiency of transmitting visible light and infrared light. In this example, the innermost layers of the antireflective coating are adapted to the transparent conductive layer.

FIGS. 3 A and 3B illustrate different examples of providing electrical power to the transparent conductive layer 32 with the antireflective coating 34. In other examples of the tip housing 2 illustrated in FIGS. 3 A and 3B, the tip housing 2 is similar to the tip housing illustrated in FIGS. 1 A to ID In FIG. 3 A, the electrical power is applied on the outer surface of the window coating 20A, which in this example is directly on the transparent conductive layer 32. The antireflective coating 34 is applied between the scan window 9 and the transparent conductive layer 32. In FIG. 3B, the electrical power is applied to the edges of the transparent conductive layer 32. In this example, the transparent conductive layer 32 is applied between the scan window 9 and the antireflective coating 34. The window coating 20A includes both the transparent conductive layer 32 and the antireflective coating 34.

FIGS. 4 A to 4C illustrate an example of the tip housing including one or more tip mirrors (10, 10A,10B).The one or more tip mirrors (10,10A,10B) has a mirror surface, wherein the mirror surface is arranged with an angle 42 of less than 90 degrees relative to the at least inner surface 9A of the scan window 9, and the mirror surface includes a mirror coating 40 configured to increase reflections of the infrared light and reflections of the visible light from the mirror surface. The mirror coating 40 is configured to increase the reflections of light having one or more wavelengths between 400 nm and 1100 nm, 400 nm and 950 nm, 350 nm and 950 nm or 350 nm and 1100 nm. The mirror coating 40 is configured to reflect at least 95 % of the infrared light and the visible light. In one example, the mirror coating 40 includes a plurality of thin film layers that includes Titanium dioxide and Silicium, wherein the plurality of thin film layers includes at least 50 layers. In FIGS. 4B and 4C, the tip housing 2 includes a first scan unit 110A and a second scan unit HOB that are arranged along a longitudinal axis 102 of the tip housing 2. The scan units 110 are similar to the once illustrated in FIGS. IB and 1C. Each of the scan units (110A,l 10B) is arranged in combination with a tip mirror (10A,10B) and an infrared light source (3A,3B). The tip mirrors (10A,10B) has a surface that includes a mirror coating (40A,40B) that are similar, and the window coating 20A extends across the whole inner surface 9 A of the scan window 9. In FIG. 4C, the second scan unit HOB is not arranged in combination with an infrared light source 3, which then resolves in that the window coating 40B on the second tip mirror 10B is different from the window coating 40 A on the first tip mirror 10 A. In another example, the window coatings (40A,40B) may be the same for the simplicity in the manufacturing of the tip housing 2. However, having two similar mirror coatings (40A,40B) in the example illustrated in FIG. 4C would not be of an advantage cost-wise. Furthermore, the window coating on the scan window is not the same across the whole inner surface 9A of the scan window 9. A first part of the scan window 9 that is aligned with the first tip mirror 10A does include a first window coating 20A that is optimized for transmitting infrared light and visible light (incl UV Light). A second part of the scan window 9 that is aligned with the second tip mirror 10B does include a second window coating 20C that is optimized for transmitting visible light (incl. UV light). In the example illustrated in FIG. 4C, the scan window 9 is made in one piece. In another example, the first part and the second part may be divided into two separate scan windows, which means, that a first scan window of the two separate scan windows includes the first part and a second scan window of the two separate scan windows includes the second part.

In the examples illustrated in FIGS. 4A to 4C do only describe a scan window 9 having a window coating on the inner surface 9A. In another example, the scan window 9 includes a window coating (20A,20B) on both the inner 9A and the external surface 9B as illustrated in FIGS. 2B and 2C.

FIGS. 5A to 5C illustrate different examples of the scan window (9, 11). In FIG. 5A, the scan window (9,11) includes different window coatings (20’, 20”), a first window coating 20’ that is optimized for transmitting both visible light (incl. UV light) and infrared light, and a second window coating 20” that is optimized for transmitting visible light (incl. UV light).

In FIG. 5A, the infrared light source 3 is aligned to the first window coating 20’, and optionally, a second image sensor unit is aligned to the first window coating 20’, wherein the second image sensor unit is configured for capturing infrared light. The second image sensor unit may be arranged in vicinity to the infrared light source 3. Both the first and second window coating (20’, 20”) are optimized for transmitting visible light which allows to have at least two scan units (110A,l 10B) aligned with the full scan window (9,11). It would be of benefit to have an extended view for the visible light for creating the 3D model, and the extended view of the infrared light is not needed. In the example illustrated in FIG. 5B, the first window coating 20’ is optimized for transmitting visible light (incl. UV light), and the second window coating 20” is optimized for transmitting infrared light. The size of the first window coating 20’ is larger than the size of the second window coating 20”. In the example illustrated in FIG. 5B there is a need to have a larger field of view of the visible light due to the generation of the 3D model than for generating infrared content images.

In the example illustrated in FIG. 5C the first window coating 20’ is surrounded by the second window coating 20” which allows infrared light sources (3A-3F) and/or image sensor units 5 to be arranged around visible light sources (7A-7C) and/or other image sensor units 5. The image sensor units 5 are not shown in FIG. 5C. The light sources (3,7) and the image sensor units 5 may be arranged pairwise within the tip housing 2. The light sources (3,7) and the image sensor units 5 may be arranged on a facing probe that is facing towards the scan window 9, which results in that an optical axis of the light sources (3,7) and the image sensor units 5 are directed towards the scan window 9. In FIG. 5C, the first window coating 20’ is optimized for transmitting visible light (incl. UV light), and the second window coating 20” is optimized for transmitting infrared light. In this example, a first group of infrared light sources (3 A - 3C) is arranged partly around a first visible light source 7A and at least a second group of infrared light sources is arranged partly around a second visible light source 7B. Thereby, an improved similarity between images generated based on visible light and images generated based on infrared light is obtained.

FIGS. 6A and 6B illustrate an inner surface 61 of the tip housing 2 being coated 60A by an antireflective coating for reducing reflections of infrared light and visible light (incl. UV light) from the inner surface 61. In FIG. 6A, a majority part of the inner surface 61 is coated with the antireflective coating. In. FIG. 6B, a majority part 60B of the inner surface 61 is not coated with an antireflective coating. In this example, an area 60B around an aperture 6C of at least 1 mm wide is coated with a material that is configured to reduce the reflections of the infrared light and the visible light from inner surfaces at the aperture and the area around the aperture of at least 1 mm wide. FIGS. 7A to 7C illustrate other examples of antireflective coatings on inner 61 and outer 62 surfaces of the tip housing 2. In FIG. 7A a majority part 61 of the inner surface 61 and the outer surface 62 of the tip housing 2 is coated with the antireflective coating 60A. FIG. 7B reflects FIG. 6A seen from a different perspective of the tip housing 2. FIG. 7C reflects FIG. 6B seen from a different perspective of the tip housing 2.

FIGS. 8A and 8B illustrate the tip housing 2 with a heating unit 80 that is connected to a flexible circuit 81. The heating unit is arranged partly around the scan window 9. In the examples, the heating unit 80 includes a first heating arm 80 that is arranged on a first side of the scan window 9 and a second heating arm 80 that is arranged on an opposite side relative to the first side. The two heating arms 80 are touching the scan window 9, and upon receiving an electrical power, the two heating arms 80 generate heat, and the heat is transferred onto the scan window 9 via the connection between the two heating arms 80 and the scan window 9. The electrical power is transferred via the flexible circuit 81 to the two heating arms 80. A temperature sensor 83 may be arranged in vicinity to the scan window 9 for the purpose of measuring a temperature of the air inside the tip housing 2 and near the scan window 9. In FIG. 8B, the flexible circuit 81 is partly covered by a material 82 that is configured to reduce the reflections of the infrared light and visible light. In the example as illustrated in FIG. 8B, the temperature sensor is covered by the material 82, but in another example, the material 82 may not be applied onto the temperature sensor for the purpose of not disturbing the measurements of the temperature.

FIG. 9 illustrates the intraoral scanning system 1, wherein the intraoral scanning device 200 includes at least the tip housing 2, the visible light source 7 and the image sensor unit 5. The one or more processors 100 may be distributed between the intraoral scanning device 200, an external computer 100, a server 204 and/or another external computer 206 configured to communicate with the intraoral scanning device 200 via a server 204. The communication between the intraoral scanning device 200 and the external computer 202 and/or the server 204 is via a wireless link 95.

Many modifications and other embodiments of the inventions set forth herein will come to mind of one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing descriptions and the associated drawings describe example embodiments in the context of certain example combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and/or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

ITEM

1. An intraoral scanning system configured to determine a three-dimensional model of an oral cavity of a patient, and wherein the system includes:

• a tip housing configured to be inserted at least partially into an oral cavity of a patient, and wherein the tip housing includes: o a scan window arranged at an aperture of the tip housing, and wherein the scan window includes an inner surface arranged within the tip housing, and o an infrared light source configured to emit infrared light towards the oral cavity via the scan window,

• a visible light source configured to emit visible light towards the oral cavity via the scan window,

• an image sensor unit configured to capture reflection of the emitted visible light and/or the emitted infrared light from the dental arch, and

• one or more processors configured to determine the three-dimensional model based on the captured visible light and to determine infrared images based on the captured infrared light, and wherein the scan window includes a window coating on at least the inner surface, and wherein the window coating is configured to reduce reflections of the infrared light and reflections of the visible light from the inner surface.

2. The intraoral scanning system according to item 1, wherein the window coating is an antireflective coating, (half/quarter wavelength is depended on the type of substrate and possibly the thickness of the substrate.)

3. The intraoral scanning system according to any of the previous items, wherein another window coating is applied on an external surface of the scan window, wherein the external surface is arranged opposite to the at least inner surface of the scan window, and wherein another window coating is configured to reduce reflection of the infrared light and reflection of the visible light.

4. The intraoral scanning system according to any of the previous items, wherein the tip housing includes a tip mirror having a mirror surface, wherein the mirror surface is arranged with an angle of less than 90 degrees relative to the at least inner surface of the scan window, and the mirror surface includes a mirror coating configured to increase reflections of the infrared light and reflections of the visible light from the mirror surface.

5. The intraoral scanning system according to any of the previous items, wherein the window coating is configured to reduce the reflections of light having one or more wavelengths between 400 nm and 1100 nm, 400 nm and 950 nm, 350 nm and 950 nm or 350 nm and 1100 nm.

6. The intraoral scanning system according to item 4, wherein the mirror coating is configured to increase the reflections of light having one or more wavelengths between 400 nm and 1100 nm, 400 nm and 950 nm, 350 nm and 950 nm or 350 nm and 1100 nm. 7. The intraoral scanning system according to any of the previous items, wherein the tip housing is coated with a material that is configured to reduce the reflections of the infrared light and the visible light.

8. The intraoral scanning system according to any of the previous items, wherein at least the aperture and an area around the aperture of at least 1 mm wide is coated with a material that is configured to reduce the reflections of the infrared light and the visible light from inner surfaces at the aperture and the area around the aperture of at least 1 mm wide.

9. The intraoral scanning system according to any of the previous items, wherein at least a part of the inner surface of the tip housing is coated with a material that is configured to reduce the reflections of the infrared light and the visible light from the inner surface of the tip housing, and wherein the inner surface of the tip housing is arranged in vicinity to the aperture.

10. The intraoral scanning system according to any of the previous items, wherein the tip housing includes a flexible circuit that partly is arranged in vicinity to the aperture, and wherein the flexible circuit is at least partly covered by a material that is configured to reduce the reflections of the infrared light.

11. The intraoral scanning system according to any of the previous items, comprising a heating unit that is arranged partly around the scan window, and wherein the heating unit is configured to apply a heat to the scan window upon receiving an electrical power.

12. The intraoral scanning system according to any of items 1 to 10, wherein the window coating is a transparent conductive layer, and wherein the transparent conductive layer is configured to reduce reflection of the infrared light and reflection of the visible light from the inner surface.

13. The intraoral scanning system according to item 12, wherein responsive to application of electrical power to the transparent conductive layer, the transparent conductive layer generates heat, and wherein the heat is transferred onto the scan window.

14. The intraoral scanning system according to any of the previous items, wherein the window coating is configured to transmit at least 95 % of the infrared light and the visible light.

15. The intraoral scanning system according to item 4 or 6, wherein the mirror coating is configured to reflect at least 95 % of the infrared light and the visible light.

16. The intraoral scanning system according to any of items 4, 6, and 15, wherein the mirror coating includes a plurality of thin film layers that includes Titanium dioxide and Silicium, and wherein the plurality of thin film layers includes at least 50 layers.

17. The intraoral scanning system according to any of items 4, 6 and 15 to 16, wherein the mirror coating is configured to reflect at least 95 % of light within 350 nm to 750 nm and at least 800nm to at least 1100 nm.

18. The intraoral scanning system according to any of the previous items, wherein the window coating includes a plurality of thin film layers that includes Tantalum pentoxide and Silicium, and wherein the plurality of thin film layers includes at least 4 layers.

Claims

• one or more processors configured to determine the three-dimensional model based on the captured visible light and to determine infrared images based on the captured infrared light, and wherein the scan window includes a window coating on at least the inner surface, and wherein the window coating is optimized for minimizing reflections of the infrared light and reflections of the visible light from the inner surface such that at least 70 % of the emitted infrared light and visible light are transmitted through the scan window.

2. The intraoral scanning system according to claim 1, wherein the window coating is an antireflective coating.

3. The intraoral scanning system according to any of the previous claims, wherein another window coating is applied on an external surface of the scan window, wherein the external surface is arranged opposite to the at least inner surface of the scan window, and wherein another window coating is configured to reduce reflection of the infrared light and reflection of the visible light.

4. The intraoral scanning system according to any of the previous claims, wherein the tip housing includes a tip mirror having a mirror surface, wherein the mirror surface is arranged with an angle of less than 90 degrees relative to the at least inner surface of the scan window, and the mirror surface includes a mirror coating configured to increase reflections of the infrared light and reflections of the visible light from the mirror surface.

5. The intraoral scanning system according to any of the previous claims, wherein the window coating is configured to reduce the reflections of light having one or more wavelengths between 400 nm and 1100 nm, 400 nm and 950 nm, 350 nm and 950 nm or 350 nm and 1100 nm.

6. The intraoral scanning system according to claim 4, wherein the mirror coating is configured to increase the reflections of light having one or more wavelengths between 400 nm and 1100 nm, 400 nm and 950 nm, 350 nm and 950 nm or 350 nm and 1100 nm.

7. The intraoral scanning system according to any of the previous claims, wherein the tip housing is coated with a material that is configured to reduce the reflections of the infrared light and the visible light.

8. The intraoral scanning system according to any of the previous claims, wherein at least the aperture and an area around the aperture of at least 1 mm wide is coated with a material that is configured to reduce the reflections of the infrared light and the visible light from inner surfaces at the aperture and the area around the aperture of at least 1 mm wide.

9. The intraoral scanning system according to any of the previous claims, wherein at least a part of the inner surface of the tip housing is coated with a material that is configured to reduce the reflections of the infrared light and the visible light from the inner surface of the tip housing, and wherein the inner surface of the tip housing is arranged in vicinity to the aperture.

10. The intraoral scanning system according to any of the previous claims, wherein the tip housing includes a flexible circuit that partly is arranged in vicinity to the aperture, and wherein the flexible circuit is at least partly covered by a material that is configured to reduce the reflections of the infrared light.

11. The intraoral scanning system according to any of the previous claims, comprising a heating unit that is arranged partly around the scan window, and wherein the heating unit is configured to apply a heat to the scan window upon receiving an electrical power.

12. The intraoral scanning system according to any of claims 1 to 10, wherein the window coating is a transparent conductive layer, and wherein the transparent conductive layer is configured to reduce reflection of the infrared light and reflection of the visible light from the inner surface.

13. The intraoral scanning system according to claim 12, wherein responsive to application of electrical power to the transparent conductive layer, the transparent conductive layer generates heat, and wherein the heat is transferred onto the scan window.

14. The intraoral scanning system according to any of claims 4 and 6, wherein the mirror coating includes a plurality of thin film layers that includes Titanium dioxide and Silicium, and wherein the plurality of thin film layers includes at least 50 layers.

15. The intraoral scanning system according to any of the previous claims, wherein the window coating includes a plurality of thin film layers that includes Tantalum pentoxide and Silicium, and wherein the plurality of thin film layers includes at least 4 layers.